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An evaluation of the use of reptile dermal scutes as a non-invasive method to monitor mercury concentrations in the environment
... As apex predators, crocodilians bioaccumulate environmental contaminants that biomagnify across food webs, and thus can be particularly vulnerable to their toxicity (Cook et al. 1991;Camus et al. 1998;Rainwater et al. 2007). Therefore, they are relevant bioindicators regarding environmental contamination (Guillette et al. 1994;Manolis et al. 2002;Campbell et al. 2003;Chumchal et al. 2011;Schneider et al. 2015). In addition, such an evaluation is also useful to determine the relatively poorly known detrimental effects of contaminants on this taxon, such as physiological and reproductive impairment and DNA damages (Guillette et al. 2000;Siroski et al. 2016;Burella et al., 2018;Lemaire et al. 2021a). ...
... However, interspecific variability across the whole group remains still poorly understood to date as most of the available studies on Hg concentrations have disproportionately focused on two species, the American Alligator, Alligator mississippiensis and the Morelet's Crocodile, Crocodylus moreletii (Yanochko et al. 1997;Jagoe et al. 1998;Elsey et al. 1999;Burger et al. 2000;Rainwater et al. 2007;Horai et al. 2014;Trillanes et al. 2014;Nilsen et al. 2017a;Buenfil-Rojas et al. 2018;Nilsen et al. 2019;Buenfil-Rojas et al. 2020). Some recent studies, however, have focused on several other species (Almli et al. 2005;Vieira et al. 2011;Lázaro et al. 2015;Schneider et al. 2015;Marrugo-Negrete et al. 2019;Lemaire et al. 2021a,b). Furthermore, Hg concentrations in crocodilians have been determined in a variety of tissues (blood, muscles, internal organs or keratinized tissues), depending on the study, which limits robust comparisons between them. ...
... Furthermore, Hg concentrations in crocodilians have been determined in a variety of tissues (blood, muscles, internal organs or keratinized tissues), depending on the study, which limits robust comparisons between them. It is worth noting that the associated methodologies (e.g., sample preparation and tissues studied) are variable, which also limits straightforward comparisons between studies (Schneider et al. 2015). Further, total Hg (THg) concentrations in these papers are either presented as the concentration relative to the wet-, or dry-weight of sampled tissues. ...
Mercury (Hg) is a global environmental contaminant that affects ecosystems. It is known to biomagnify through food webs, and to bioaccumulate especially in the tissues of top predators. Large scale comparisons between taxa and geographic areas are needed to reveal critical trends related to Hg contamination and its deleterious effects on wildlife. Yet, the large variety of tissues (keratinized tissues, internal organs, blood) as well as the variability in the units used to express Hg concentrations (either in wet- or dry-tissue weight) limits straightforward comparisons between studies. In the present study, we assessed the moisture content that could influence the total Hg (THg) concentrations measured in several tissues (claws, scutes, total blood and red blood cells) of three caiman species. First, we aimed to evaluate the moisture content from the different tissues, and second to provide information on THg concentrations in various matrices. Our results show a difference of THg concentrations between the tissues and intra- and interspecific variations of moisture content, with the highest THg values found in keratinized tissues (scute keratinized layers and claws). For the three species, we found positive relationships between body size and THg concentration in keratinized tissues. In the blood, the relationship between body size and THg concentration was species-dependent. Our results emphasize the need for a standardized evaluation of THg concentration and trace elements quantification based on dry weight analytical procedures. In addition, the use of both blood and keratinized tissues offers the possibility to quantify different time scales of THg exposure by non-lethal sampling.
... Delany et al., 1988;Jagoe et al., 1998;Burger et al., 2000;Almli et al., 2005;Vieira et al., 2011;Eggins et al., 2015;Nilsen et al., 2017;Buenfil-Rojas et al., 2020). In certain geographical areas (e.g., Amazon region), the abundant natural Hg in soil and biota (e.g. an average of 0.3 µg.g -1 in forest soil in French Guiana, Richard et al., 2000), human activities such as deforestation, gold mining activities and agriculture additionally contribute to increase Hg bioavailability (Roulet et al., 1998;Maurice-Bourgoin et al., 2000, Vieira et al., 2011Schneider et al., 2012;Correia et al., 2014;Eggins et al., 2015;Lázaro et al., 2015;Schneider et al., 2015;Rivera et al., 2016, Marrugo-Negrete et al., 2019, Lemaire et al., 2021. ...
... Mercury concentrations obtained in crocodilian tissues have been shown to reflect the contamination of the individual's environment across different temporal scales (Lázaro et al., 2015;Schneider et al., 2015). Blood Hg concentration is thought to reflect relatively recent Lemaire et al.: I got it from my mother: Inter-nest variation of mercury concentration in neonate Smoothfronted Caiman (Paleosuchus trigonatus) suggests maternal transfer and possible phenotypical effects 4 exposure, while keratinized tissues (e.g., scales and claws) seem to reflect Hg concentration accumulated during longer time periods . ...
... In our samples, claws had 2.1 times higher Hg concentrations than scutes which reflect the fact that our scute samples were composed of keratin layer as well as the underlying connective tissues with presumably lower Hg Lemaire et al.: I got it from my mother: Inter-nest variation of mercury concentration in neonate Smoothfronted Caiman (Paleosuchus trigonatus) suggests maternal transfer and possible phenotypical effects 10 concentrations. Keratinized tissues, by the immobilization of Hg, reflect the long-term Hg exposure in crocodilians (Lazaro et al., 2015;Schneider et al., 2015). The significant relationship between Hg concentrations in the total blood and the keratinized tissues claims for the use of keratinized tissues as a less invasive sampling method to provide information on Hg concentration in caimans. ...
The deleterious effects of mercury (Hg) contamination are well documented in humans and wildlife. Chronic exposure via diet and maternal transfer are two pathways which increase the toxicological risk for wild pop- ulations. However, few studies examined the physiological impact of Hg in crocodilians. We investigated the Hg contamination in neonate Smooth-fronted Caimans, Paleosuchus trigonatus, and the use of keratinized tissues and blood to evaluate maternal transfer. Between November 2017 and February 2020, we sampled 38 neonates from 4 distinct nests. Mercury concentration was measured in claws, scutes and total blood. Highest Hg concentrations were found in claws. Strong inter-nest variations (Hg ranging from 0.17 ± 0.02 to 0.66 ± 0.07 μg.g− 1 dw) presumably reflect maternal transfer. Reduced body size in neonates characterized by elevated Hg concentrations suggests an influence of Hg during embryonic development. We emphasize the use of claws as an alternative to egg collection to investigate maternal transfer in crocodilians. Our results demonstrated the need of further investigation of the impact of Hg contamination in the first life stages of crocodilians.
... Indeed, they are long-lived predators, resulting in the accumulation of Hg over a lifespan of several decades. As ectothermic vertebrates, crocodilians display relatively low metabolic rates, but relatively high tissue conversion rates; two features that are expected to favor the bioaccumulation of significant levels of Hg (Cook et al., 1989;Camus et al., 1998;Jagoe et al., 1998;Twining et al., 1999;Schneider et al., 2015;Lázaro et al., 2015;Nilsen et al., 2017). Maternal transfer, an elimination pathway of Hg, which is already known from a variety of reptiles, can also be found in crocodilians (Sakai et al., 2000;Day et al., 2005;Nilsen et al., 2020). ...
... Eaton and Link, 2011), yet, in wild populations, detailed information on age is rarely available. The relationship between crocodilian size and Hg concentration in tissues such as blood, scutes, claws, muscles and liver shows that Hg is bioaccumulated across the life of an individual (Burger et al., 2000;Schneider et al., 2015;Lázaro et al., 2015;Marrugo-Negrete et al., 2019). Although the Hg concentration in various tissues and the body size are positively correlated in some crocodilian species (i.e., Alligator mississippiensis, Caiman crocodilus, Melanosuchus niger, Caiman yacare), we emphasize that this pattern has not been detected in other species (i.e., Crocodylus acutus, Crocodylus moreletii, Yanochko et al., 1997;Burger et al., 2000;Rainwater et al., 2007;Schneider et al., 2015;Lázaro et al., 2015;Marrugo-Negrete et al., 2019). ...
... The relationship between crocodilian size and Hg concentration in tissues such as blood, scutes, claws, muscles and liver shows that Hg is bioaccumulated across the life of an individual (Burger et al., 2000;Schneider et al., 2015;Lázaro et al., 2015;Marrugo-Negrete et al., 2019). Although the Hg concentration in various tissues and the body size are positively correlated in some crocodilian species (i.e., Alligator mississippiensis, Caiman crocodilus, Melanosuchus niger, Caiman yacare), we emphasize that this pattern has not been detected in other species (i.e., Crocodylus acutus, Crocodylus moreletii, Yanochko et al., 1997;Burger et al., 2000;Rainwater et al., 2007;Schneider et al., 2015;Lázaro et al., 2015;Marrugo-Negrete et al., 2019). Such divergent findings may highlight the importance of relatively large sample sizes associated with significant body size ranges in order to robustly assess the relationship between Hg and individual traits. ...
... Similarly, no significant correlation was found between the THg concentrations in the tissues and the size or weight of crocodilians at the different sampling sites (r b 0.1, p N 0.05). Several studies have found a positive relationship between the THg concentration in tissues such as muscle, scales, blood, and claws and the size of Alligator mississippiensis, Melanosuchus niger, and Caiman crocodilus (Yanochko et al., 1997;Burger et al., 2000;Schneider et al., 2012Schneider et al., , 2015Lázaro et al., 2015;Nilsen et al., 2016). However, other studies on Crocodylus moreletii and Crocodylus acutus have found a different pattern (Rainwater et al., 2002). ...
... Highest THg concentrations were found in claws, followed by scutes and blood (Table 1). Similar findings were previously reported in other species of alligators and caimans (Lázaro et al., 2015;Schneider et al., 2015;Buenfil-Rojas et al., 2018). Moreover, the highest THg in all the biological samples correspond to samples located at S1. THg concentrations were about 18 times higher in claws than in blood in all three sampling sites. ...
... This protein is rich in amino acids with sulfhydryl groups that form complexes with Hg of the metallothioneins type, facilitating the toxic bioconcentration of Hg. In fact, these tissues have shown a high potential for serving as a better indicator of contaminant levels in internal tissues than muscle and bone (Buenfil-Rojas et al., 2018;Schneider et al., 2015). On the other hand, in the caudal scutes of crocodiles, the content of THg in the keratinized epidermis can be diluted by the bone dermis of the scales ; in addition to the losses due to the natural erosion of the skin, and the effect that dietary changes have on the THg concentration in both blood and scales, due to continuous metabolic exchange with the rest of the body (Rainwater et al., 2007;Richardson et al., 2002;Nilsen et al., 2016). ...
One of the most representative predator species in tropical ecosystems is caiman that can provide relevant information about the impact of mercury (Hg) associated with artisanal and small-scale gold mining. To evaluate the degree to which adverse effects are likely to occur in Caiman crocodilus, total Hg (THg) concentrations in different tissues and DNA damage in erythrocytes were determined. Samples of claws, scutes, and blood were taken from 65 specimens in sites impacted by upstream gold mining, and in a crocodile breeding center as control site, located in a floodplain in northern Colombia. In all the sites, the highest THg among tissues was in the following order: claws >> scutes > blood. High concentrations of THg were found in the different tissues of the specimens captured in areas impacted by mining activities, with mean values in claws (1100 ng/g ww), caudal scutes (490 ng/g ww), and blood (65 ng/g ww), and statistically significant differences compared to those of the control site (p < 0.05). THg in scutes from impacted sites are 15-fold higher than in control, whereas for claws and blood are 8 times higher, and a high significant correlation with THg was found in all the tissues. The comet assay reveals significant differences in the DNA damage in the exposed reptiles compared to the controls (p < 0.01). In sum, C. crocodilus from La Mojana floodplain presents a high ecological risk given its genotypic susceptibility to Hg levels present in its habitat, which could possibly influence vital functions such as reproduction of the species and the ecological niche that it represents within the ecosystem.
... Whereas Hg bioaccumulation in fish and humans is well documented in the Amazon basin [13,23], few studies have reported Hg concentrations in Amazonian reptiles. Only 5 studies have investigated Hg bioaccumulation in Amazonian turtles [7,16,[24][25][26], and only 2 studies have investigated Amazonian caimans [6,25]. These studies indicate that substantial Hg bioaccumulation is occurring but are largely inconclusive as to what factors control Hg bioaccumulation in Amazonian reptiles. ...
... Whereas Hg bioaccumulation in fish and humans is well documented in the Amazon basin [13,23], few studies have reported Hg concentrations in Amazonian reptiles. Only 5 studies have investigated Hg bioaccumulation in Amazonian turtles [7,16,[24][25][26], and only 2 studies have investigated Amazonian caimans [6,25]. These studies indicate that substantial Hg bioaccumulation is occurring but are largely inconclusive as to what factors control Hg bioaccumulation in Amazonian reptiles. ...
... It also assessed whether farming of these reptiles can reduce Hg exposure to consumers and whether nonlethal sampling techniques can be used to monitor Hg concentrations in threatened Amazonian reptile species. With the threatened status of many reptile species [28], it is becoming increasingly important to develop reliable nonlethal sampling techniques to monitor Hg concentrations in their tissues [24,25,29]. Accordingly, we focused on commonly consumed species that are of high commercial value, specifically 2 species of turtle of the Podocnemididae family (Podocnemis unifilis and Podocnemis expansa) and 2 species of caiman (Melanosuchus niger and Caiman crocodilus). ...
... Whereas Hg bioaccumulation in fish and humans is well documented in the Amazon basin [13,23], few studies have reported Hg concentrations in Amazonian reptiles. Only 5 studies have investigated Hg bioaccumulation in Amazonian turtles [7,16,[24][25][26], and only 2 studies have investigated Amazonian caimans [6,25]. These studies indicate that substantial Hg bioaccumulation is occurring but are largely inconclusive as to what factors control Hg bioaccumulation in Amazonian reptiles. ...
... Whereas Hg bioaccumulation in fish and humans is well documented in the Amazon basin [13,23], few studies have reported Hg concentrations in Amazonian reptiles. Only 5 studies have investigated Hg bioaccumulation in Amazonian turtles [7,16,[24][25][26], and only 2 studies have investigated Amazonian caimans [6,25]. These studies indicate that substantial Hg bioaccumulation is occurring but are largely inconclusive as to what factors control Hg bioaccumulation in Amazonian reptiles. ...
... It also assessed whether farming of these reptiles can reduce Hg exposure to consumers and whether nonlethal sampling techniques can be used to monitor Hg concentrations in threatened Amazonian reptile species. With the threatened status of many reptile species [28], it is becoming increasingly important to develop reliable nonlethal sampling techniques to monitor Hg concentrations in their tissues [24,25,29]. Accordingly, we focused on commonly consumed species that are of high commercial value, specifically 2 species of turtle of the Podocnemididae family (Podocnemis unifilis and Podocnemis expansa) and 2 species of caiman (Melanosuchus niger and Caiman crocodilus). ...
Total mercury (Hg) concentrations of muscle, liver, blood, and epidermal keratin were measured in typically consumed, economically and culturally important species of turtle (Podocnemis unifilis and Podocnemis expansa) and caiman (Melanosuchus niger and Caiman crocodilus) from the Rio Purus in the Amazon basin, Brazil. Methylmercury (MeHg) concentrations were also measured in muscle tissue, representing the first analysis of MeHg concentrations in Amazonian reptile species. In muscle tissues Hg was mostly MeHg (79–96%) for all species. No correlations existed between animal size and total Hg or MeHg concentrations for any species other than M. niger, possibly as a result of growth dilution or the evolution of efficient Hg elimination mechanisms. Significant linear correlations were found between total Hg concentrations in all pairs of nonlethally sampled tissues (keratin and blood) and internal tissues (muscle and liver) for M. niger and between keratin and internal tissues for P. expansa, indicating that nonlethally sampled tissues can be analyzed to achieve more widespread and representative monitoring of Hg bioaccumulation in Amazonian reptiles. Although mean Hg concentrations in muscle for all species were below the World Health Organization guideline for safe consumption (500 µg kg–1), mean concentrations in caiman liver were above the safe limit for pregnant women and children (200 µg kg–1). No significant differences were found between total Hg and MeHg concentrations in tissues from wild-caught and farm-raised P. expansa, suggesting that farming may not reduce Hg exposure to humans. Environ Toxicol Chem 2015;9999:1–11. © 2015 SETAC
... They are relatively simple to collect and should contain high concentrations of Hg due to their high keratin content (Alibardi, 2003). These tissues are also devoid of bones or muscles, which could act as sources of varying concentrations of Hg (Richardson et al., 2002;Schneider et al., 2015). ...
... Since there are differences between sizes of caimans captured in the study areas, we use a size ratio to include the data in the ANCOVA model, eliminating the effect of size. The size ratio for each animal was calculated by dividing the sampled SVL by the maximum SVL reported for the animals of each area (Schneider et al., 2015). ...
... There are several works showing that Hg in crocodilians muscles increases linearly with time of exposure (Yanochko et al., 1997;Burger et al., 2000;Rumbold et al., 2002;Schneider et al., 2012) but few have examined the relationship between size and Hg concentration in keratinized tissues (Schneider et al., 2015). Previous studies have reported a significant positive correlation between Hg concentration in scute and size in A. mississipiensis, M. niger and C. crocodilus (Yanochko et al., 1997;Burger et al., 2000;Schneider et al., 2015) but not in C. moreletii and C. acutus (Rainwater et al., 2002). ...
... Os autores alertaram para o risco de problemas de saúde associados ao Hg caso o consumo seja frequente (SCHNEIDER et al., 2012). Ainda no Rio Purus, Schneider et al. (2015) utilizaram os cágados Podocnemis unifilis e Podocnemis expansa e os jacarés Melanosuchus niger e Caiman crocodilos como modelo para avaliar qual tecido (queratina, ossos e músculo) seria melhor preditor da concentração de Hg. Além disso, os autores associaram os anéis de crescimentos dos cágados com o acúmulo de Hg. ...
... Além disso, os autores associaram os anéis de crescimentos dos cágados com o acúmulo de Hg. A queratina foi considerada um melhor preditor de exposição ao Hg, apresentando a vantagem de ser uma técnica menos invasiva, ideal para o biomonitoramento (SCHNEIDER et al., 2015). Ademais, a medição de Hg nos aneis de crescimento da carapaça dos cágados, apresentaram um potencial significativo para estimar a bioacumulação de Hg ao longo do tempo. ...
Pollution is a threat to the aquatic ecosystem because different chemicals, such as metals and drugs, are discarded and can interfere with the metabolism and physiology of aquatic organisms. Among these environments affected by anthropic action, municipal water reservoirs can be highlighted. Faced with this problem, this chapter presents different ecotoxicological tools (biomarkers) to assess the impact of pollution on freshwater fish from municipal water reservoirs. We highlight the following biomarkers: biotransformation, metal sequestration, oxidative stress, genotoxic effects, cellular integrity, cell/tissue damage, neurotoxicity, and reproductive (endocrine disruption and seminal quality). It is observed that some of these biomarkers are widely used in field studies to evaluate the impact of the mixture of pollutants on different physiological processes, such as the generation of oxidative stress. However, other biomarkers are still little explored in these studies, such as cell integrity and seminal quality analysis.
... Os autores alertaram para o risco de problemas de saúde associados ao Hg caso o consumo seja frequente (SCHNEIDER et al., 2012). Ainda no Rio Purus, Schneider et al. (2015) utilizaram os cágados Podocnemis unifilis e Podocnemis expansa e os jacarés Melanosuchus niger e Caiman crocodilos como modelo para avaliar qual tecido (queratina, ossos e músculo) seria melhor preditor da concentração de Hg. Além disso, os autores associaram os anéis de crescimentos dos cágados com o acúmulo de Hg. ...
... Além disso, os autores associaram os anéis de crescimentos dos cágados com o acúmulo de Hg. A queratina foi considerada um melhor preditor de exposição ao Hg, apresentando a vantagem de ser uma técnica menos invasiva, ideal para o biomonitoramento (SCHNEIDER et al., 2015). Ademais, a medição de Hg nos aneis de crescimento da carapaça dos cágados, apresentaram um potencial significativo para estimar a bioacumulação de Hg ao longo do tempo. ...
A toxicologia é uma ciência muito antiga, já que as plantas e os animais desde os primórdios já apresentavam substâncias tóxicas em suas estruturas e o ser humano necessitava compreender suas ações como medidas de precaução. Com o surgimento da problemática gerada pela degradação exacerbada e poluição ambiental decorrente da revolução industrial do pós-guerra e das transformações científico-tecnológicas, agravadas por fatores como o elevado crescimento populacional e pressão sobre
os recursos naturais, houve a necessidade de incorporar os aspectos ecológicos ao estudo dos efeitos tóxicos das substâncias sintetizadas por ações antropogênicas e que invariavelmente afetam o meio ambiente e organismos não-alvo. Assim, surge a ecotoxicologia com suas ferramentas metodológicas de avaliação da qualidade ambiental e crítica sobre a relação predatória com o ambiente natural. A ecotoxicologia é uma ferramenta útil para criar políticas com a implantação de diretrizes e regulamentações mais rígidas para combater a poluição. Recentemente, contaminantes que não eram encontrados frequentemente no ambiente ou que não haviam sido relatados como oferecendo potencial perigo aos organismos vivos passaram a ser relatados em diversos habitats e seu risco passou a ser investigado; essa classe de compostos é chamada de contaminantes emergentes. Assim, este capítulo objetiva
contextualizar a ecotoxicologia, explorando as suas metodologias de investigação da saúde ambiental com foco nos ecossistemas aquáticos e principalmente poluentes emergentes.
... Caudal scute sampling is a widespread non-lethal technique providing tissues samples for the analysis of pollutants (Lázaro et al., 2015), which has been shown more useful in predicting Hg exposure than muscle or bone tissues (Schneider et al., 2015). The method is preferred over other types of tissue sampling since it is easily performed in the field, allows for tag identification of specimens, and permits ethical, non-intrusive sampling of many individuals. ...
... Hg -0.10 +0.08 +0.02 -0.23 ** Cd +0.15 * +0.12 þ0.30 *** Pb þ0.23 ** -0.01 * Cu þ0.35 *** (Schneider et al., 2015). However, and despite the widespread use of scutes in ecotoxicological studies, the reliability of scutes as a proxy for internal trace element concentrations in organs for crocodiles is rarely discussed as such studies are not applicable in wild populations with protection status. ...
Crocodylus moreletii (Morelet’s crocodile) and Crocodylus acutus (American crocodile) are generalist, apex predators of subtropical aquatic habitats in Central America. As top predators, crocodiles may be exposed to high levels of micro pollutants, such as trace elements via bioaccumulation that enter the food web as a consequence of human activities. As such, the status of their population can be considered indicative of that of the entire ecosystem – i.e., crocodiles constitute as genuine indicator species. In this study, we report on the concentrations of trace elements found in the caudal scutes of 178 specimens of C. acutus and C. moreletii from Belize. Our objectives were three-fold: (1) to assess variation in trace element concentration between species, sexes, age classes and body index; (2) to identify areas with elevated exposure to trace elements by comparing concentrations in the scutes of crocodiles at various sites in Belize; and (3) to explore links between crocodile trace element load and local land use. All elements tested (Hg, Pb, Cd, As, Cu, Zn, Co) could be detected in at least some scutes. Many of the readings of As and Co were under or close to the detection limit and were not further analyzed. Relatively high Hg concentrations were observed in adults from Chiquibul Forest (median 3.170 µg/g) and Ambergris Caye (0.834 µg/g). Concentrations of Hg and Pb tended to be higher in adult animals than in juveniles, especially in C. acutus. On the other hand, concentrations of Cd, Cu and Zn were higher in juveniles than in subadult adult animals. Concentrations of Cu were higher in C. acutus than in C. moreletii, but otherwise no species-effects were found for the other trace elements. We found a negative correlation between Hg and Zn concentrations; correlations among Cd, Pb, Cu and Zn concentrations tended to be positive. In both juveniles and adults, animals with high concentrations of Zn had lower body-indices (a proxy for physiological condition). None of the other element concentrations correlated with the body-index. Specimens of C. acutus were more often sampled at coastal sites, while C. moreletii sampling points were typically closer to agricultural or forested areas. A canonical correlation analysis revealed a significant association between trace element load and habitat characteristics. Animals sampled inland, near submontane forests, contained higher levels of Hg, while animals sampled near agricultural, urban or lowland habitats tended to have higher concentrations of Cd, Pb, Cu and Zn. This study identifies the most prevalent trace element concentrations impacting Belizean watersheds while highlighting the exposure risk to non-essential trace elements in less-urbanised areas or protected areas.
... Amazonian crocodilians' diet varies with ages, sex, season, habitat, year, and availability of prey (Santos et al. 1996;Grigg and Kirshner 2015). Yacare position in the trophic chain should result in high concentrations of mercury as seen for other species of South American crocodiles (Vieira et al. 2011;Schneider et al. 2015). However, Rivera et al. (2016) reported mercury concentration in the muscle tissue of the Yacare below the levels seen in carnivorous fish, which are part of the Yacare diet. ...
... The highest concentrations of THg found in our Yacare liver samples relative to other tissues agrees with data from other species of crocodilians and also other vertebrate's (Rumbold et al. 2002;Lucia et al. 2010;Branco et al. 2011;Souza-Araujo et al. 2015;Schneider et al. 2015;Buenfil-Rojas et al. 2018) (Table S1). Hg may be initially retained in the liver before distribution to other tissues and also before excretion as a result of higher metallothionein production (Piotrowski et al. 1974;Zalups and Koropatnick 2000). ...
Caiman yacare is considered one of the top predators in the Amazon basin, and understanding pollutant distribution within its tissues may help its sustainable management. As a top predator, C. yacare should have the highest mercury concentrations, but has lower Hg concentrations than carnivorous fish (Rivera et al. 2016), which are part of their diet. We compared total Hg among liver, kidney, fat, and muscle of C. yacare, and whether trends in the distribution of Hg among tissues were like other crocodilians, aquatic birds, omnivorous, and carnivorous fish. Fat had the lowest concentrations (0.025 ± 0.03 mg kg⁻¹) followed by muscle (0.15 ± 0.06 mg kg⁻¹), kidney (0.57 ± 0.30 mg kg⁻¹) and liver (1.81 ± 0.80 mg kg⁻¹). Such preferential accumulation makes C. yacare meat a safer alternative for human consumption than carnivorous fish. The relation between Hg accumulation in liver and muscle is highest in crocodilians, which has evolutive and environmental implications.
... Day et al., 2005;Komoroske et al., 2011;Bezerra et al., 2013). Because the high affinity of Hg for keratinized tissues, concentrations of this element in scutes or nails are commonly higher than in other tissues (Hopkins et al., 2013a;Schneider et al., 2015). However, the use of scutes or nails to monitor other elements like lead (Pb) is not so frequent in chelonians (Barraza et al., 2019), and no links between Pb concentrations in scutes and internal tissue burdens have been established for these species. ...
... However, whereas Pb also shows affinity by bone tissues in the inner bone layer of the carapace (Anan et al., 2001), the little affinity of Hg by these bone tissues could be limiting the capacity of scutes to accumulate Hg even in the keratinized external surface that we monitored. Schneider et al. (2015) found a significant correlation between Hg concentrations in scutes and in muscle of two Amazonian freshwater turtle species (Podocnemis unifilis and Podocnemis expansa), but scute and bone concentrations were not correlated. Considering nails, a keratinized structure that does not growth over an ossified layer, a correlation of Hg concentrations between this tissue and blood was also observed by Hopkins et al. (2013a) in three turtle species (C. ...
Among reptiles, freshwater turtle species have high potential for metal accumulation because of their long lifespan or their aquatic and terrestrial habits. In order to monitor metal bioaccumulation, determine potential toxic effects, and investigate tools for non-invasive metal sampling in reptiles, we studied lead (Pb) and mercury (Hg) accumulation in Mediterranean pond turtles (Mauremys leprosa) inhabiting two former mining areas, one of them with high environmental concentrations of Pb (Sierra Madrona-Alcudia Valley district) and the other one with high environmental concentrations of Hg (Almadén district). Individuals from the Pb mining area showed mean blood concentrations (i.e. 5.59 μg Pb/g dry weight, d.w.) that were higher than those measured in other populations. Blood Hg concentrations were highest (8.83 μg Hg/g d.w.) in the site close to the former Hg mines, whereas blood Hg concentrations in terrapins from another site of Almadén district, located ∼28 km downstream, were not different from locations at the non-mining area. Animals from the Pb-contaminated site showed evidence of oxidative stress, whereas those from the Hg-contaminated site showed increased activity of the antioxidant enzyme glutathione peroxidase, as well as reduced circulating levels of the main endogenous antioxidant peptide, glutathione. Concentrations measured in feces and carapace scutes were useful indicators to monitor blood concentrations of Pb, but not of Hg. Our results provide evidence of the usefulness of freshwater turtles as sentinels of chronic metal pollution, and validate non-invasive tools to advance Pb monitoring in reptiles.
... The use of scutes has helped to promote research with sea turtles, mainly because it is a non-invasive method and a tissue that, unlike the liver or kidney, accumulates Hg for a longer time, thus providing a history of Hg accumulation (Schneider et al. 2015). Studies such as those by Vander Zanden et al. (2013) show that the estimated time that scutes can retain several types of resources (e.g. ...
With no known biological function, mercury (Hg) is highly toxic, bio-accumulates, and biomagnifies up the food web. Long-living marine animals, such as sea turtles, can be exposed to Hg in the oceans. The wide distributions of these reptiles and lifespans compatible with Hg residence time in ocean surface waters (approximately 30 yr) makes them reliable biological monitors of the long-term changes in Hg concentrations in the oceans. Taking this into consideration, we conducted a thorough review of studies to compare the concentrations of Hg in the 7 species of sea turtles distributed in different regions of the Atlantic, Pacific, and Indian Oceans and the Mediterranean Sea. Hg concentrations in muscle and scutes of Chelonia mydas were highest in the South Atlantic, whereas the highest concentrations found in Caretta caretta occurred in the Mediterranean Sea. The differences could be associated with the feeding habits of each species and the characteristics of the environment, such as the oligotrophic nature of the water and the lower productivity in the Mediterranean Sea. Unfortunately, few studies exist for the other 5 sea turtles (Dermochelys coriacea, Eretmochelys imbricata, Lepidochelys olivacea, L. kempii, and Natator depressus), which hampers a more detailed regional or ecological comparison among species. The results found in this review reveal information gaps that should be filled through more numerous studies focused on different oceanic regions and species.
... 52(3) 2022: 254 -263 ACTA AMAZONICA lithogenic mercury intake is more significant than that from external sources (Brabo et al. 2003;Castro et al. 2016). THg levels in the muscle of P. unifilis in this study were similar to those found in P. unifilis in the Purus River (Schneider et al. 2015) and in the lower Xingu River (Souza-Araujo et al. 2015), and were lower than the concentrations observed in the Negro River basin (Schneider et al. 2010(Schneider et al. , 2011 and another study from the lower Xingu River (Pignati et al. 2018) (see Table 3). ...
Chelonians are considered good bioindicators of environmental quality. The assessment of the health status of chelonian populations in the Amazon is important because they are traditionally consumed in large numbers in riverine communities and sustainable use reserves. The present study aimed to evaluate the health of Podocnemis unifilis (Testudines, Podocnemididae) in an environmental protection area in the Amazon region in Brazil. We analyzed the biomarkers lipoperoxidation, carbonylation of proteins, occurrence of micronuclei and erythrocytic nuclear abnormalities, quantified metallothioneins, and evaluated mercury bioaccumulation. We generated pioneering data regarding biomarkers in wild Amazonian freshwater turtles. All biomarker responses did not vary significantly between the sexes. The occurrence of oxidative and genotoxic damage, as well as concentrations of metallothioneins was low compared to other studies. In addition, the bioaccumulation of mercury in the muscle of the animals was below the limit recommended for human consumption by the World Health Organization. Our results provide baseline data on mercury bioaccumulation and biomarker responses that can be useful for future comparisons with other freshwater turtles. The data also provide evidence that the sustainable exploitation of these turtles in the study area (Piagaçu-Purus Sustainable Development Reserve) does not pose a risk to local riverine communities, as the detected mercury concentrations are safe for human consumption. In this sense, our results highlight the importance of protected areas for the conservation of healthy turtle populations, at the same time ensuring the health of the human populations that use them as a food resource.
KEYWORDS:
freshwater turtle; health parameters; chelonians; Testudinidae; ecotoxicology
... Several papers report efforts to elucidate the spatial distribution of Hg with LA-ICP-MS using simple line scans on samples like hair [22], dorsal spine of fish [23], or turtle carapace [24], to reveal variations in exposure to this heavy metal over time. X-ray spectroscopic techniques have been employed to investigate Hg uptake and its 2-dimensional distribution in plants [25], fish [26], and whale brains [27]. ...
This work describes the development of a novel method for quantitative mapping of Hg and Se in mushroom fruit body tissues with laser ablation coupled to inductively coupled plasma-mass spectrometry (LA-ICP-MS). Different parameters of the protocol for preparation of the standards used for quantification via external calibration were assessed, e.g., the dissolution temperature of gelatin standards and the addition of chitosan and l -cysteine as additives to the gelatin-based calibration droplets to better match the sample matrix. While chitosan was not suited for this purpose, the presence of l -cysteine considerably improved the figures of merit of the calibration, leading to limits of detection of 0.006 and 0.3 µg g ⁻¹ for Hg and Se, respectively, at a pixel size of 20 × 20 µm. Further, an in-house reference material, ideally suited for the validation of the method for application to mushroom samples, was successfully prepared from a paste of Boletus edulis . The newly developed method was used to investigate the distribution of Hg and Se in tissue sections of five porcini mushroom individuals of three different species ( Boletus edulis , Boletus aereus , and Boletus pinophilus ) and one sample of a parasol mushroom ( Macrolepiota procera ) . For one sample, additional areas were ablated at higher spatial resolution, with a laser spot size down to 5 µm, which allows a detailed investigation of the spatial distribution of Hg and Se in mushrooms.
Graphical abstract
... Although they showed that PCR has a higher sensitivity than standard microscopy for ectoparasite detection, they concluded that PCR on swabs is less accurate [190]. For reptiles, the detection of mercury in skin scutes has been described [191]. It would be of interest to assess whether the shed skins of reptiles could be used with similarly reliable results. ...
In the last decades, wildlife diseases and the health status of animal populations have gained increasing attention from the scientific community as part of a One Health framework. Furthermore, the need for non-invasive sampling methods with a minimal impact on wildlife has become paramount in complying with modern ethical standards and regulations, and to collect high-quality and unbiased data. We analysed the publication trends on non-invasive sampling in wildlife health and disease research and offer a comprehensive review on the different samples that can be collected non-invasively. We retrieved 272 articles spanning from 1998 to 2021, with a rapid increase in number from 2010. Thirty-nine percent of the papers were focussed on diseases, 58% on other health-related topics, and 3% on both. Stress and other physiological parameters were the most addressed research topics, followed by viruses, helminths, and bacterial infections. Terrestrial mammals accounted for 75% of all publications, and faeces were the most widely used sample. Our review of the sampling materials and collection methods highlights that, although the use of some types of samples for specific applications is now consolidated, others are perhaps still underutilised and new technologies may offer future opportunities for an even wider use of non-invasively collected samples.
... Indeed, the positive relationship between Hg concentration and body size of M. niger is in accordance with the study from Eggins et al. (2015) in Brazil, though contrasts with previous studies for C. crocodilus in Brazil and Colombia, where Hg concentrations and body size were not correlated Marrugo-Negrete et al., 2019). In most vertebrates, Hg blood concentration is considered to represent a relatively recent contamination (Monteiro and Furness, 2001;Fournier et al., 2002;Schneider et al., 2015) that reflects variations in the environmental Hg contamination or modifications in the origin of prey. Such variations may explain the nonconsistence in the relationship between body size and Hg contamination in some cases. ...
Trace elements in the blood of crocodilians and the factors that influence their concentrations are overall poorly documented. However, determination of influencing factors is crucial to assess the relevance of caimans as bioindicators of environmental contamination, and potential toxicological impact of trace elements on these reptiles. In the present study, we determined the concentrations of 14 trace elements (Ag, As, Cd, Cr, Co, Cu, Fe, Hg, Pb, Mn, Ni, Se, V, and Zn) in the blood of four French Guiana caiman species (Spectacled Caiman Caiman crocodilus [n = 34], the Black Caiman Melanosuchus niger [n = 25], the Dwarf Caiman Paleosuchus palpebrosus [n = 5] and the Smooth-fronted Caiman Paleosuchus trigonatus [n = 20]) from 8 different sites, and further investigated the influence of individual body size and stable isotopes as proxies of foraging habitat and trophic position on trace element concentrations. Trophic position was identified to be an important factor influencing trace element concentrations in the four caiman species and explained interspecific variations. These findings highlight the need to consider trophic ecology when crocodilians are used as bioindicators of trace element contamination in environmental studies.
... It follows that carapace Hg concentration is a better predictor of exposure to Hg than Hg concentrations in skin tissue of flatbacks. This is in agreement with previous Hg studies on reptiles, which demonstrated the ability of keratin from both turtle carapace and caiman (Melanosuchus niger and Caiman crocodilus) skin to bioaccumulate Hg (Bezerra et al., 2013;Day et al., 2005;Innis et al., 2008;Komoroske et al., 2011;Schneider et al., 2015Schneider et al., , 2009. This is because beta-keratins from caiman and turtle epidermis contain large amounts of amino acids (Alibardi, 2003;Toni et al., 2007) to which Hg is bound in relatively stable Hg complexes . ...
Mercury pollution in the surface ocean has more than doubled over the past century. Within oceanic food webs, sea turtles have life history characteristics that make them especially vulnerable to mercury (Hg) accumulation. In this study we investigated Hg concentrations in the skin and carapace of nesting flatback turtles (Natator depressus) from two rookeries in Western Australia. A total of 50 skin samples and 52 carapace samples were collected from nesting turtles at Thevenard Island, and 23 skin and 28 carapace samples from nesting turtles at Eighty Mile Beach. We tested the influence of turtle size on Hg concentrations, hypothesizing that larger and likely older adult turtles would exhibit higher concentrations due to more prolonged exposure to Hg. We compared the rookeries, hypothesising that the turtles from the southern rookery (Thevenard Island)
were more likely to forage and reside in the Pilbara region closer to industrial mining activity and loading ports (potential exposure to higher environmental Hg concentrations) with turtles from the northern rookery (Eighty Mile Beach) more likely to reside and feed in the remote Kimberley. Turtles from the Eighty Mile Beach rookery had significantly higher skin Hg concentrations (x�= 19.4 ± 4.8 ng/g) than turtles from Thevenard Island (x�= 15.2 ± 5.8 ng/g).
There was no significant difference in carapace Hg concentrations in turtles between Eighty
Mile Beach (x�= 48.4 ± 21.8 ng/g) and Thevenard Island (x�= 41.3 ± 16.5 ng/g). Turtle size did not explain Hg concentrations in skin samples from Eighty Mile Beach and Thevenard Island, but turtle size explained 43.1% of Hg concentrations in the carapace of turtles from Eighty Mile Beach and 44.2% from Thevenard Island. Mercury concentrations in the flatback turtles sampled in this study are relatively low compared to other sea turtles worldwide, likely a result of the generally low concentrations of Hg in the Australian environment. Although we predicted that mining activities would influence flatback turtle Hg bioaccumulations, our data did not support this effect. This may be a result of foraging ground overlap between the two rookeries, or the predominant wind direction carrying atmospheric Hg inland rather than seaward. This is the first Hg study in skin and carapace of flatback turtles and represents a baseline to compare Hg contamination in Australia’s surrounding oceans
... De modo geral, as principais ameaças aos crocodilianos estão relacionadas à perda de hábitat (MAGNUSSON e CAMPOS, 2010a, b;CAMPOS et al., 2012b;MUNIZ, et al., 2018 resíduos químicos e o despejo e/ou rompimento de minérios com Pb em substratos aquáticos (BRAZAITIS et al., 1996). Na Amazônia, as taxas de mercúrio (Hg) geralmente são altas (SCHNEIDER et al., 2012), sendo encontrado em concentrações significativas nos jacarés da Bacia Amazônica (SCHNEIDER et al., 2015;EGGINS, et al., 2015). ...
Como citar este trabalho:
SILVA, F. P.; MACIEL, J. C. T.; FRANCO, D. L.; OLIVEIRA, B. R.; BOTERIO-ARIAS, R.; BARRETO-LIMA, A. F. Pesquisa e conservação de crocodilianos da Região Norte do Brasil. In: BARRETO-LIMA, A. F.; SANTOS, M. R. de D.; NÓBREGA, Y. C. (Ed.) Tratado de Crocodilianos do Brasil. 1a. ed. Vitória: Editora Instituto Marcos Daniel, 2021. Cap. 18, p. 457-497. Disponível em: <htpp://www.imd.org.br>. Acesso em: data, mês, ano.
... Several species of reptiles display long life cycles, territorial behavior, and resistance to environmental changes and are important key species for maintaining ecosystem homeostasis. Since the 1980s, they have been applied in the detection and monitoring of contaminated sites, mainly lentic environments such as lakes, ponds, and reservoirs (Tellez & Merchant, 2015;Schneider et al., 2015;Nilsen et al., 2017). Despite adequate responses, the use of organs in the detection of chemical contaminants requires animal sacrifice. ...
In the present study, Fe, Cu, Cr, Cd, Pb, Ni, and Al concentrations in Caiman latirostris and Testudines blood from the Tapacurá reservoir, Pernambuco, Brazil, were investigated. Blood was acid digested with HNO3, and metals were determined by ICP-OES and FAAS. Lead showed concentrations below the established limit of detection. Eighty animals were evaluated, forty from each group. The levels of all elements were statistically significant when compared between the two studied taxa (p < 0.05). In caimans, significant differences between young and adults were observed for chromium (p = 0.0539) and aluminum (p = 0.0515). Testudines showed no statistically significant differences for the variable age structure. Gender did not influence metal concentrations detected in the present study for either group. Differences between species of testudines were significant for Fe between Mesoclemmys tuberculata vs Phrynops geoffroanus (p = 0.0932) and Kinosternon scorpioides vs Phrynops geoffroanus (p = 0.063). The inter-elementary correlations showed statistically significant differences between the elements Cr vs Al (R2 = 0.52), Cr vs Cd (0.43), Cd vs Cu (R2 = 0.41), Ni vs Cu (R2 = 0.31), Ni vs Cr (R2 = 0.30), Al vs Cd (R2 = 0.27), and Cd vs Fe (R2 = 0.26). It is concluded that blood is an excellent predictor of metals in crocodilians and testudines in the Tapacurá reservoir, with statistically significant differences when correlated to concentrations such as size and species studied. In addition, it evidenced data that prove the exposure of these animals to metals, with strong inter-elementary correlations and opening doors for future studies that seek to understand possible biological effects caused in the studied taxa.
... In this case the levels of mercury exceeded the Brazilian permitted limit of 0.5 ppm. Other studies show that despite detecting levels of pollution below the limits, they can represent risks for health to pregnant women, children and those populations that base their diet almost exclusively on aquatic animals coming from contaminated areas (Bourdineaud et al., 2015;Schneider et al., 2015). We provide here a useful database for researchers and governments to develop environmental research strategies, promoting the protection of biodiversity, including human beings. ...
Emissions of metals and metalloids (Hg; Cd; Cr; Cu; Pb; Ni; Zn; Fe; Mn; As; Se) generated by natural (e.g.,geothermal activity) or anthropic causes (eg., industry or mining) represent a worldwide contamination problem, especially in developing countries. Exposure to high concentrations of these elements is harmful to living beings, including humans. Information on this type of contamination is scarce and fragmented, limiting research which could benefit from these data. To know the state of the research, we reviewed the studies of environmental pollution by metals and metalloids carried out on animal species in Latin America. The use of animals as biomonitors of contamination by metals and metalloids is a continuously expanding practice that allows for early detection of problems. With this work, we were able to identify the most studied areas in Latin America(Amazon, Gulf of California, coastal area between Rio de Janeiro and Florianopolis and River Plate Estuary). Moreover, we provide information on the most studied metals (Hg, Cd, Cu, Pb, Zn) and wild species, which evidence the use of endangered species. The data reviewed should help researchers to direct their efforts towards sparsely researched areas and facilitate bibliographic consultation of scientific information on exposure to metals and metalloids in Latin America.
... Blood was drawn into sodiumheparinized 10-mL glass vacutainers (Becton Dickson, San Jose, California). To account for varying keratin concentrations throughout the carapace (Schneider et al., 2015), scutes were sampled via numbering each scute and using a random number selector to randomly choose scutes to sample. Scutes were only sampled if there were no injuries on the scutes chosen or if the scute exhibited a thin keratin layer. ...
Foraging aggregations of east Pacific green sea turtles (Chelonia mydas) inhabit the Seal Beach National Wildlife Refuge (SBNWR) and San Diego Bay (SDB), two habitats in southern California, USA, located near urbanized areas. Both juvenile and adult green turtles forage in these areas and exhibit high site fidelity, which potentially exposes green turtles to anthropogenic contaminants. We assessed 21 trace metals (TM) bioaccumulated in green turtle scute and red blood cell (RBC) samples collected from SBNWR (n = 16 turtles) and SDB (n = 20 turtles) using acid digestion and inductively coupled plasma mass spectrometry. Principal component analyses of TM composition indicate that SBNWR and SDB turtles have location-specific contaminant signatures, characterized by differences in cadmium and selenium concentrations: SBNWR turtles had significantly more cadmium and selenium in RBC and more selenium in scute samples, than SDB turtles. Cadmium and selenium concentrations in RBC had a strong positive relationship, regardless of location. SBNWR turtles had higher selenium in RBCs than previously measured in other green turtle populations globally. Due to different retention times in blood vs. scute, these results suggest that SBNWR turtles have high long- and short-term selenium exposure. Turtles from SBNWR and SDB had higher trace metal concentrations than documented in green turtle populations that inhabit non-urbanized areas, supporting the hypothesis that coastal cities can increase trace metal exposure to local green turtles. Our study finds evidence that green turtle TM concentrations can differ between urbanized habitats and that long-term monitoring of these green turtles may be necessary.
... The accumulation of Hg in tissues of freshwater turtles exposed to environmental Hg has been well-documented (Green et al. 2010;Turnquist et al. 2011;Hopkins 2012;Yu et al. 2011;Hopkins et al. 2013a;Meyer et al. 2014;Powell 2014;Zapata et al. 2014;Châteauvert et al. 2015;Schneider et al. 2015;Landler et al. 2017;Slimani et al. 2018). Turtles that inhabit freshwater wetlands can serve as effective biomonitors for these increasingly threatened ecosystems because of their wide distribution, long life expectancies and their higher trophic positions eating fish, amphibians, and invertebrates (Golet and Haines 2001;Guillot et al. 2018). ...
Aquatic turtles are suitable biomonitors of wetland ecosystem health because they are long-lived and occupy elevated trophic positions in wetland food webs. This study aimed to determine Hg exposure in adult Blanding's turtles (Emydoidea blandingii), an imperiled prairie-wetland species endemic to the northern U.S. and southern Canada. Claw samples were collected from gravid females from four wetland sites in northeast Illinois. Claw Hg concentrations ranged from 654 to 3132 ng/g and we found no effect of body size (carapace length, CL) and some evidence for an effect of wetland site (WS) on mean Hg (i.e. weak effect of site on Hg, detected between WS1 and WS3). Claw Hg concentrations reported in this study were lower than claw concentrations published for other freshwater turtles (e.g. Chelydra serpentina, Sternotherus oderatus). This is the first Hg-related study on Blanding's turtles and can serve as a reference for other Hg studies in Illinois wetlands.
... Characterized by an indeterminate growth, many aquatic reptile species display very wide size range between minute neonates and large adult individuals which allow access to bioaccumulation processes within a population. Finally, easily accessible tissues such as claws in turtles or scales in snakes, in which Hg tends to accumulate and bind to keratins (Hopkins et al., 2013b), provide a powerful opportunity to adopt a non-invasive technique in order to assess Hg contamination in these organisms (Schneider et al., 2015). ...
... Most recently, researchers have been using blood and dermal scutes in reptile monitoring studies (Rainwater et al., 2007;Schneider et al., 2015;Sherwin et al., 2016;Tremblay et al., 2017;Trillanes et al., 2014) as a reliable non-lethal sampling technique to monitor the OCP presence in animals and the environment. Blood samples are widely accepted measurements for chemical exposure (Angerer et al., 2007). ...
... Yacare meat is rich in proteins, and it may be an important source of Omega-3 fatty acids (IBCE, 2010). Its position in the trophic chain generates a high concern of potential Hg exposure for the consumers, as high mercury concentrations have already been reported in other species of South American crocodilians ( Schneider et al., 2015;Vieira, 2011). Here we investigate the concentrations of total mercury in Caiman yacare and compare it to the mercury concentration in seven fish species (five carnivorous and two non-carnivorous), which are all common in the diet of the Tacana people in the Beni river basin ( Miranda-Chumacero et al., 2011). ...
Mercury contamination in the River Beni basin is an important health risk factor, primarily for indigenous communities that live along the river. Among them are the Tacana, living in their original territory with sustainable use of their natural resources, consuming fish, Caiman yacare, and other riverine resources as their main source of protein. To assess mercury exposure to Tacana people, total mercury (THg) was evaluated in the muscle of seven commercial fish, and Caiman yacare (yacare caiman) during 2007 and 2008. THg was extracted by acid digestion and concentrations were determined by atomic absorption spectrometry. Mean mercury concentrations in C. yacare was 0.21 ± 0.22 μg g(-1)Hg w.w. (wet weight), which is lower than expected given its high trophic level, and its long life-span. It is possible that mercury in C. yacare is accumulated in other organs, not included in this study; but it is also possible that physiological mechanisms are involved that help caimans get rid of ingested mercury, or simply that C. yacare's diverse diet reduces THg accumulation. Carnivorous fishes (Pygocentrus nattereri, Pseudoplatystoma tigrinum, Zungaro zungaro, Plagioscion squamosissimus, and Leiarius marmoratus) had the highest total mercury concentrations, ranging from 0.35 to 1.27 μg g(-1)Hg w.w. moreover, most were above the limit recommended by WHO (0.5 μg g(-1)Hg w.w.); except for Leiarius marmuratus, which presented a mean of 0.353 ± 0.322 μg g(-1)Hg w.w. The two non-carnivorous fish species (Prochilodus nigricans, and Piaractus brachypomus) present mean concentrations of 0.099 ± 0.027, and 0.041 ± 0.019 μg g(-1)Hg w.w., respectively. Finally, recommendations on the consumption habits of Tacana communities are discussed.
Researchers are highly aware of the silent, negative effects caused by mercury pollution in gold mining areas. Freshwater turtles are culturally part of the diet of riverside populations in the Amazon region and this area presents mercury (Hg) pollution issues mainly due to gold mining activities. Thus, this research aimed to evaluate the total mercury (THg) content in the different organs of river turtles (P. expansa) and carry out a human health risk assessment associated with the consumption of these animals. Skin (n=28), muscle (n=19) and brain (n=2) samples were analyzed by Atomic Absorption Spectrometry (TDA-AAS) and a DMA-80™ mercury analyzer used for the total mercury determinations. The average values found for THg in the skin, muscle and brain samples were, respectively, 0.1045 mg.kg-1, 0.1092 mg.kg-1 and 0.0601mg.kg-1. Thus, THg was observed even though the P. expansa were kept in captivity, possibly due to previous contamination by air, water and food. The Hazard Quotient (HQ) was calculated considering a 9.07g.day-1 intake dose of P. expansa and the consumption of turtles once a week showed a HQ=2.45, which may cause long-term injuries to human health. Although the muscle concentrations were below the maximum limit established by the World Health Organization (WHO) and Brazilian regulatory agencies, it is important to evaluate consumption factors such as amount ingested, frequency and animal gender, which may cause a potential risk to regular consumers due to mercury bioaccumulation. The WHO may consider various aspects in order to warn the amazon population about the severity and silent hazard of this metal, especially due to the importance of this matrix in the region. This region urgently needs government actions to inhibit clandestine mining and to prevent future serious, chronic health problems of the entire population.
With no known biological function, mercury (Hg) is highly toxic, bio-accumulates, and biomagnifies up the food web. Long-living marine animals, such as sea turtles, can be exposed to Hg in the oceans. The wide distributions of these reptiles and lifespans compatible with Hg residence time in ocean surface waters (approximately 30 yr) makes them reliable biological monitors of the long-term changes in Hg concentrations in the oceans. Taking this into consideration, we conducted a thorough review of studies to compare the concentrations of Hg in the 7 species of sea turtles distributed in different regions of the Atlantic, Pacific, and Indian Oceans and the Mediterranean Sea. Hg concentrations in muscle and scutes of Chelonia mydas were highest in the South Atlantic, whereas the highest concentrations found in Caretta caretta occurred in the Mediterranean Sea. The differences could be associated with the feeding habits of each species and the characteristics of the environment, such as the oligotrophic nature of the water and the lower productivity in the Mediterranean Sea. Unfortunately, few studies exist for the other 5 sea turtles ( Dermochelys coriacea , Eretmochelys imbricata , Lepidochelys olivacea , L. kempii , and Natator depressus ), which hampers a more detailed regional or ecological comparison among species. The results found in this review reveal information gaps that should be filled through more numerous studies focused on different oceanic regions and species.
Mercury (Hg) is a global environmental contaminant that affects ecosystems. It has the particularity to biomagnify through the food web, and to bioaccumulate especially in tissues of top predators. Mercury has been identified to have detrimental effects on human and wildlife. Top predators from tropical ecosystems are particularly affected by Hg contamination due to artisanal small scale gold mining, which uses massive amounts of Hg in the gold extraction process.
Crocodilians are top predators of tropical ecosystems and have been identified to accumulate high concentrations of Hg in their tissues. They are potentially good candidates to monitor Hg contamination, as they are long-living animals with low metabolic, and high tissue conversion rates, which favours the bioaccumulation of Hg. Additionally, they have a large repartition over tropical and sub-tropical ecosystems, which make large-scale Hg evaluation possible. My doctoral work focuses on the four caiman species that are present in French Guiana (the Black caiman Melanosuchus niger, the Dwarf caiman Paleosuchus palpebrosus, the Smooth- fronted caiman Paleosuchus trigonatus and the Spectacled caiman Caiman crocodilus). First, I have worked on Hg variation across different tissues obtained by minimally invasive methods, and investigated the influence of morphology and feeding ecology (by using stable isotope method) on Hg contamination in caimans. Second, I have investigated the impact of Hg contamination on physiological mechanisms, and the maternal transfer and its effects on neonates.
The quantification of Hg in blood and keratinized tissues of caimans is more reliable when using dry weight due to the variation of moisture content in different tissues. These tissues further inform on different time scales of Hg contamination: Relatively recent contamination in blood, and long-term contamination in keratinized tissues. Trophic ecology had been the main factor that influence Hg concentration; Body size of caimans was essential to be consider during Hg contamination assessment due to the bioaccumulation, and because caimans growth continuously. Results showed that Hg contamination was related to disruption of renal, hepatic and endocrine functions in young C. crocodilus at low Hg level, leading to potential toxic effects of Hg on caimans. Maternal transfer was evaluated in claws of freshly hatched P. trigonatus, which provides an effective method to quantify foetal Hg exposure, and additionally offers an alternative to evaluate maternal transfer in caimans, compared to egg destruction. In neonates, Hg exposure was related to a reduction of body size, which indicated a potential disruption during embryonic development.
This doctoral work highlights that caimans are effective species to monitor Hg contamination, and stresses the need to thoroughly investigate the consequences of Hg contamination in crocodilians.
Capítulo 19 do Tratado de crocodilianos do Brasil, que aborda aspectos sobre o histórico, status e prespectivas sobre os jacarés na região nordeste.
Como citar este trabalho:
COUTINHO, M. E.; SANTOS, M. R. DE D.; BARRETO-LIMA, A. F.; NÓBREGA, Y. C. Conservação de crocodilianos no Brasil: Perspectivas e possibilidades. In: BARRETO-LIMA, A. F.; SANTOS, M. R. de D.; NÓBREGA, Y. C. (Ed.) Tratado de Crocodilianos do Brasil. 1a. ed. Vitória: Editora Instituto Marcos Daniel, 2021. Cap. 24, p. 622-641. Disponível em: <htpp://www.imd.org.br>. Acesso em: data, mês, 2021.
Como citar a obra: BARRETO-LIMA, A. F.; SANTOS, M. R. de D.; NÓBREGA, Y. C. Tratado de Crocodilianos do Brasil. Vitória: Editora Instituto Marcos Daniel, 2021. 641 p. Disponível em: <htpp://www.imd.org.br>. Acesso em: dia, mês, ano.
RESUMO
Esta relevante obra acadêmica – Tratado de Crocodilianos do Brasil – representa uma grande ação colaborativa com a participação significativa de 69 pesquisadores(as) de diferentes gerações, formações acadêmicas e técnicas, reunindo informações básicas e especializadas de diversas áreas de interesse. A obra está estruturada em seções temáticas, apresentando 24 capítulos científicos originais. Pioneiramente, este livro apresenta os aspectos fundamentais, históricos, bem como os mais atualizados sobre estudos com populações de espécies de jacarés do Brasil. Estudos estes aos quais os(as) pesquisadores(as) dedicaram anos ou mesmo décadas de esforços pessoais e profissionais em pesquisas com os crocodilianos em seus respectivos ambientes naturais ou em cativeiros. O livro está organizado em eixos sequenciais, contemplando na primeira parte a evolução e a história de vida dos crocodilianos fósseis (paleontologia), a riqueza de espécies e as linhagens crípticas entre as espécies brasileiras (sistemática e taxonomia). A segunda parte aborda os métodos de campo voltados aos estudos ecológicos e comportamentais com populações, além do uso de ferramentas de modelagem de distribuição potencial direcionados à conservação. Na terceira parte, é abordado o uso comercial sustentável, os diferentes manejos de criação de jacarés aplicados à conservação de espécies de valor comercial, enfocando também uma discussão importante e atualizada sobre tais assuntos e as suas consequências de uso. A quarta parte foi exaustivamente dedicada à medicina veterinária e à saúde dos crocodilianos, abordando o manejo e a conservação das espécies em temos clínicos, sob diferentes pontos de vista: farmacologia aplicada, histologia, necropsia, parasitologia e semiologia. A quinta parte apresentou e valorizou elegantemente os estudos de conhecimentos culturais e tradicionais, por meio da difusão científica, educação ambiental e pesquisas etnozoológicas, todas aplicadas à conservação dos jacarés. E na sexta parte, a obra encerra-se estrategicamente revelando o cenário atual das pesquisas e perspectivas relacionadas à conservação das seis espécies de crocodilianos do Brasil, de acordo com as regiões do país (Norte, Nordeste, Centro-Oeste, Sudeste e Sul) e os seus diferentes biomas associados. Este livro deixa a mensagem de que o conhecimento e a ciência devem ser divulgados da forma mais ampla, gratuita e democrática possível, gerando reais ganhos à nossa sociedade, à biodiversidade, ao ambiente em que vivemos e aos inúmeros profissionais que trabalham heroicamente nas diferentes áreas de atuação.
Despite the general lack of studies that use reptiles as bioindicators, the value of freshwater turtles and crocodilians in ecotoxicology has been proven, due to their importance as sentinel species. The aim of this study was to compile information on the use of freshwater turtles and crocodilians as environmental biomonitors of inorganic element contamination. We searched for articles in databases using specific keywords. A total of 104 studies published between the years 1970 and 2020 were collected. We noted a general increase in the number of studies involving turtles and crocodilians during the study time period. The Order Testudines were the subjects of 46% of the analysed publications, and the Order Crocodylia accounted for 54%. Within these studies, we counted 39 species (turtles n=29 and crocodilians n=10). Forty chemical elements were evaluated in the analysed articles, of which the majority represented non-essential elements (Hg, Cd, Pb). Although internal organs constituted the main biological matrix chosen for each group (37%), we observed an increase in the use of non-destructive matrices in both groups (scale, blood, tail muscle, carapace). The majority of analysed studies used HNO3 for the sample decomposition, with the majority of analyses being per-
formed using atomic absorption spectroscopy (53%). Mainly blank controls (19%), analyte recovery (18%) and replicates (18%) were used as methods of validating analytical procedures. Furthermore, the studies used certified reference materials, which measure the accuracy of the methods used. We conclude that the increase in the use of aquatic reptiles in environmental monitoring research is mainly due to their ability to reveal integrated changes in ecosystems, aiding
in environmental public policy decision-making and effective management plans.
Environmental contaminants affect ecosystems worldwide and have deleterious effects on biota. Non-essential mercury (Hg) and lead (Pb) concentrations are well documented in some taxa and are described to cause multiple detrimental effects on human and wildlife. Additionally, essential selenium (Se) is known to be toxic at high concentration but, at lower concentrations, Se can protect organisms against Hg toxicity. Crocodilians are known to bioaccumulate contaminants. However, effects of these contaminants on physiological processes remain poorly studied. In the present study, we quantified Hg, Pb and Se concentrations in spectacled caimans (Caiman crocodilus) and investigated effects of these contaminants on several physiological processes linked to osmoregulatory, hepatic, endocrine and renal functions measured through blood parameters in 23 individuals. Mercury was related to disruption of osmoregulation (sodium levels), hepatic function (alkaline phosphatase levels) and endocrine processes (corticosterone levels). Lead was related to disruption of hepatic functions (glucose and alanine aminotransferase levels). Selenium was not related to any parameters, but the Se:Hg molar ratio was positively related to the Na⁺ and corticosterone concentrations, suggesting a potential protective effect against Hg toxicity. Overall, our results suggest that Hg and Pb alter physiological mechanisms in wild caimans and highlight the need to thoroughly investigate the consequences of trace element contamination in crocodilians.
The illegal pet trade facilitates the global dispersal of invasive alien species (IAS), providing opportunities for new pests to establish in novel recipient environments. Despite the increasing threat of IAS to the environment and economy, biosecurity efforts often lack suitable, scientifically-based methods to make effective management decisions, such as identifying an established IAS population from a single incursion event. We present a proof-of-concept for a new application of a stable isotope technique to identify wild and captive histories of an invasive pet species. Twelve red-eared slider turtles ( Trachemys scripta elegans ) from historic Australian incursions with putative wild, captive and unknown origins were analysed to: (1) present best-practice methods for stable isotope sampling of T. s. elegans incursions; (2) effectively discriminate between wild and captive groups using stable isotope ratios; and (3) present a framework to expand the methodology for use on other IAS species. A sampling method was developed to obtain carbon (δ ¹³ C) and nitrogen (δ ¹⁵ N) stable isotope ratios from the keratin layer of the carapace (shells), which are predominantly influenced by dietary material and trophic level respectively. Both δ ¹³ C and δ ¹⁵ N exhibited the potential to distinguish between the wild and captive origins of the samples. Power simulations demonstrated that isotope ratios were consistent across the carapace and a minimum of eight individuals were required to effectively discriminate wild and captive groups, reducing overall sampling costs. Statistical classification effectively separated captive and wild groups by δ ¹⁵ N (captive: δ ¹⁵ N‰ ≥ 9.7‰, minimum of 96% accuracy). This study outlines a practical and accessible method for detecting IAS incursions, to potentially provide biosecurity staff and decision-makers with the tools to quickly identify and manage future IAS incursions.
La región de la Mojana desde hace muchos años ha estado presentando problemáticas ambientales asociadas a los metales pesados, principalmente por mercurio, que potencialmente está afectando la fauna silvestre. El objetivo de este estudio fue determinar las concentraciones de mercurio total en hígado de T. callirostris en tres localidades del departamento de Sucre pertenecientes a la región de la Mojana. Se tomaron muestras de hígado de 35 individuos de T. callirostris, se cuantificaron las concentraciones de mercurio total por el método de Espectrometría de Absorción Atómica con previos tratamientos de las muestras. Los resultados mostraron diferencias significativas entre los sitios muestreados (p<0,05) en las concentraciones de mercurio, y no se encontró ninguna correlación con los parámetros morfométricos. Las concentraciones de mercurio encontradas en este estudio demuestran el potencial riesgo ambiental para esta y las demás especies, en especial las de mayor consumo humano.
The present work tests the use of carapace fragments of the marine turtle Caretta caretta as a tool for environmental biomonitoring of mercury (Hg) and to evaluate the influence of biological and ecological factors in Hg concentrations. Samples of carapace fragments were obtained during the nesting season of 2012 and 2016 and were analyzed for their total-Hg and methyl-Hg concentrations and the isotopic composition of carbon and nitrogen (δ15N and δ13C). Seventy-six females were sampled, with an average size of 87.1 to 107 cm of curved carapace length (CCL). The results showed a wide variation in total Hg concentrations (3.3 - 1,672 ng g-1) and low concentrations of methyl-Hg, not showing any pattern of accumulation among the individuals. The isotopic composition of δ15N and δ13C suggests that the individuals sampled belong to a high trophic level but did not present any relationship with the Hg concentrations. It suggests that, at least with the existing results, and unlike other turtle species, carapace fragments of C. caretta cannot yet be used in environmental monitoring.
Blood is considered a suitable biomonitoring matrix for evaluating relatively recent exposure to environmental contaminants since abrupt changes in exposure regimes are rapidly reflected in blood. On the other hand, keratinized tissues, such as turtle scutes, are known to integrate trace element exposure over relatively long time periods. This study aimed to test the use of the differences in blood and scute to inform on the historical trace element exposure of green turtles. We propose a blood-scute kinetic model to predict how an increase in exposure would affect the concentrations in these two matrices over time. We then tested the relationship between blood and scute concentrations for 19 trace elements in two green turtle populations presumed to experience relatively constant exposure conditions. Significant log-log and linear correlations were observed between blood and scute concentrations for Co, As, Mo, Sb, and Cd. We then analysed blood-scute ratios in turtles from two coastal sites with known elevated exposure to various trace elements from previous studies. Deviations from the steady-state were clearly evident in these coastal turtles (for Co and Cd) and were consistent with the model prediction of changes in exposure. These field data provide evidence that blood-scute ratios can provide a valuable tool for examining the historical trace element exposure of turtles. We further present a method by which the general model may be refined and validated, by using data from individual turtles that had been recaptured across multiple years. Although the timeframe and number of recaptured samples available for this study were limited, the temporal changes in blood-scute ratios in these animals were generally consistent with those suggested by the model. Thus, the ratio between paired blood and scute trace element concentrations could be used to establish a temporal exposure index in turtles.
Mercury (Hg) is a toxic contaminant present in most aquatic ecosystems. High concentrations pose serious threats to organisms and to human health. Because previous studies focused on few countries, environmental hazard due to Hg contamination remains obscure in many geographic areas, and for example limited information is available in North Africa. We examined total Hg contamination in 13 sites in Morocco (12 rivers and one lake) spread over a large area, 400 km north–south and 350 km west–east, that encompasses different biogeographic zones separated by the Atlas Mountains. Due to their longevity and sedentary habits, we used freshwater turtles as biological probes to monitor Hg exposure. Keratinized tissues reflect long-term Hg exposure; thus, we assayed Hg concentration in the claws of > 200 individuals and supplemented these data with blood Hg concentrations of > 60 individuals (a tissue that provides shorter term Hg exposure integration). The results provide the first large-scale picture of Hg contamination in the aquatic freshwater systems of Morocco. Comparisons with previous studies revealed that some of the sites were highly contaminated (e.g. mean Hg concentrations were above 5 μg g⁻¹, a very high level in keratinized tissues) whereas other sites presented moderate or baseline levels. Unexpectedly, all highly contaminated sites were found in less densely populated areas, while more densely urbanized northern sites, even the sewers of large cities, were not highly contaminated. We hypothesize that silver mining activities in the southern High Atlas and in the Anti-Atlas contaminate rivers of the catchment basins over long distances. These findings indicate that fish, water consumption and contamination levels in local people should be further scrutinized.
Urbanization and the continued encroachment of human activity into green spaces often result in the decline of several animal species. Macroclemys temminckii (alligator snapping turtle) is particularly sensitive to human activity as it is an opportunistic scavenger and carnivore. The longevity of this species, as well as its dietary habits make it an excellent candidate for biomonitoring. In this preliminary study, twelve (12) shell samples were collected from individuals trapped at Fort Polk, LA and Sam Houston Jones State Park, LA. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to determine the presence of the toxic metals cadmium (Cd), chromium (Cr) and lead (Pb) in addition to other trace minerals and iron (Fe). The levels of the toxic metal were below the detection limit of the ICP-OES. This report represents the first study of this nature on Macroclemys temminckii.
Marine turtles are considered good sentinel species for environmental assessment because of their long lifespan, feeding ecology, habitat use and migratory nature. In the present study, we assessed presence of cadmium, lead and mercury, together with organic pollutants, both in fat and muscle tissue of 25 stranded loggerhead turtles (Caretta caretta) stranded along the Valencian Community coast (East Spain) (43.7 ± 13.5 cm). Mean concentrations of Cd, Pb and Hg were 0.04 μg/g w.w., 0.09 μg/g w.w. and 0.03 μg/g w.w. in fat and 0.05 μg/g, 0.08 μg/g and 0.04 μg/g in muscle, respectively. These measures indicate a relatively low mean heavy metal concentration, which may be explained by juvenile size and developmental stage of the turtles analysed. A preliminary non-targeted analysis (using time-of-flight (TOF) technology), made for the first time in marine turtles, allowed to detect 39 different pesticides, most of them previously undetected in this species. Most of the organic substances detected are used in agricultural activities, and the use of 15 of them (38.5%) is not approved in the European Union. Our sample did not show any trend on pollutant contents in relation to turtle size or stranding location, probably because of the high diversity of pollutants found. However, the potential for a positive latitudinal gradient should be explored in future studies due to riverine inputs and high agricultural and industrial activities in the area. Despite the high diversity of pollutants found here, comparative studies of pollutants in other matrices at sea are needed to ascertain whether the loggerhead turtle is a good sentinel of chemical pollution in the western Mediterranean.
The measurement of trace elements and phosphorus in marine biological tissues by ICP-MS after low-volume closed-vessel microwave digestion with nitric acid is described. Variations in final nitric acid concentration (0-6%, v/v) of digests caused a decrease in ICP-MS signal only for Zn and Se. Polyatomic interferences from Ca, Na, K, Mg, P, S, Cl, and C at levels expected in marine tissues were investigated. Isotopes of Cr, V, Fe, Co, Ni, Cu, Zn, Cd, As, and Se are likely to suffer from interferences. Choosing alternative isotopes for most elements can minimize potential interferences. Eleven CRMs were analyzed: BCR CRM 414 Plankton, IAEA 140/TM Fucus, NIES No. 9 Sargasso Seaweed, IAEA-MA-A-1 Copepods, NIST SRM 1566a Oyster Tissue, AGAL-3 Prawn, NRCC Tort-1 Lobster Hepatopancreas, AGAL-2 Shark, IAEA MA-A-2 Fish Flesh, NRCC DOLT-1 Dog Fish Liver, NIST CRM 50 Albacore Tuna. Acceptable concentrations were obtained for P, V, Mn, Fe, Cr, Co, Ni, Cu, Zn, As, Se, Ag, Cd, and Pb. There was little indication of - interference from CI on As and Se or from Ca on Co. Sb concentrations were in general agreement with certified concentrations, but variability in certified concentrations are large, thus not allowing a rigorous comparison to be made. Cr concentrations are also in general agreement with certified concentrations when isotopic mass counts are corrected for carbon and/or chloride interferences. Hg values are consistently overestimated and variable as the CRM concentrations are near the instrumental limit of detection.
Although turtles are well protected by laws in Brazil, the laws are not enforced in some places and ignored in others. Based on 15 years of work in the Rio Negro Basin, we describe the history of turtle exploitation in this region, comment on their current conservation status, and suggest practical conservation alternatives that are necessary to preserve stable populations.
Methyl mercury is a persistent environmental contaminant that threatens the health of organisms in ecosystems throughout the world. Since methylmercury bioaccumulates over time and biomagnifies at each trophic level, long-lived, carnivorous species such as reptiles are at greatest risk. Reptiles have often been used as bioindicators of local mercury contamination, and many species have been shown to accumulate large concentrations of mercury in affected habitats. Annually worldwide, millions of reptiles, both wild and farm-raised, are sold for human consumption. Consuming wildlife contaminated with mercury poses a serious threat to human health, particularly for pregnant women and children. In this chapter, we review data of mercury concentrations in reptile species harvested for food. Mercury concentrations in reptile species are compared considering their trophic status and origin (wild-caught or farm-raised) to assess how different groups of organisms respond to mercury contamination. Also, the different origins of Hg are considered in order to understand the effects of different bioaccumulation routes. The issue of legal and illegal trade of reptiles for food in both developed and developing countries is described here to demonstrate the potential health risks to humans. In order to assess the contamination risk per species, we compared Hg concentrations in reptiles with consumption limits developed by the U.S. Environmental Protection Agency and Food and Drug Administration to evaluate mercury consumption No part of this digital document may be reproduced, stored in a retrieval system or transmitted commercially in any form or by any means. The publisher has taken reasonable care in the preparation of this digital document, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained herein. This digital document is sold with the clear understanding that the publisher is not engaged in rendering legal, medical or any other professional services.
Although turtles are well protected by laws in Brazil, the laws are not enforced in some places and ignored in others. Based on 15 years of work in the Rio Negro Basin, we describe the history of turtle exploitation in this region, comment on their current conservation status, and suggest practical conservation alternatives that are necessary to preserve stable populations.
Caiman crocodilus crocodilus and Melanosuchus niger occur throughout most of the Anavilhanas Archipelago, located in the lower Rio Negro, Central Amazonia. The observed densities of these species vary from 0 to 58 per km of shoreline and 0 to 8 per km of shoreline, respectively. Multiple regression analysis indicated that the temperature difference between the water and the air, and water depth affected the observed density of C. crocodilus during spotlight surveys in the Archipelago. Percentage illumination by the moon, cloud cover, frequency of occurrence of grass, and food availability did not significantly affect the observed density of C. crocodilus. Nine hatchling groups of M. Niger that hatched in 1992 were found on islands near the north bank of the Rio Negro, and 15 of 20 hatchlings groups of C. crocodilus were found closer to the south bank, indicating a tendency for separation of nesting areas. Discriminant function analysis indicated that water depth and presence of grass were correlated with the occurrence of hatchling groups. Melanosuchus niger hatchling groups occurred in areas with deeper water and more grass than those of C. crocodilus. This study showed that surveying hatchling groups in the Anavilhanas Archipelago is more efficient than surveying for subadults and adults, which, by itself, can give false impressions about the suitability of areas for conservation of breeding populations of these species.
This study determined the concentrations of mercury (Hg) in four tissues of six species of turtles from the Rio Negro in the Amazon Basin. For two species, blood and carapace tissues were correlated with concentrations in internal tissues to establish whether blood or carapace could serve as a non-lethal indicator of internal metal exposure or body burden. The four tissues’ Hg levels were also correlated to turtle size and gender. The liver in five species of turtles had the highest concentration, followed by carapace, muscle, and blood. The exception was Chelus fimbriatus, which had a higher metal concentration in the muscle than carapace. Regarding the correlation between total Hg concentrations in tissues of the two species, no significant correlation was noted for Podocnemis erythrocephala. However, for Podocnemis sextuberculata significant correlation was found between muscle × liver, muscle × blood, and liver × blood. For P. erythrocephala, there was a correlation between Hg concentration in carapace and turtle size. For P. sextuberculata, there was no marked correlation between Hg concentration and size, but concentration in muscle was significantly influenced by gender. The patterns of Hg accumulation in tissues of the five species followed those described for freshwater species and some species of sea turtles. The difference in C. fimbriatus may be a result of a different pattern of non-living keratin layers on the carapace tissue. The use of carapace to infer internal concentrations of Hg is common in freshwater and sea turtles, but in this study it was found that only blood might be a reliable indicator of Hg concentrations in liver and muscle tissues for P. sextuberculata. Thus blood may be used as a non-invasive method to study concentrations of Hg in liver and muscle of P. sextuberculata.
Growth rings of costal scutes were counted using 35 mm photographic slides of 192 desert tortoises (Gopherus agassizii) from 11 study sites in the Mojave and Colorado deserts of California. From 0 to ≥ 3 rings were formed yearly, but subannular rings could not be distinguished visually from annular rings. Growth ring counts from photographic records of scutes are not a reliable means of determining absolute age in juvenile and immature desert tortoises ≤ 180 mm in carapace length. Ring count data varied by desert region; mean number of rings produced yearly varied from 0.86 in the western Mojave to 1.17 in the northeastern Mojave. Mean numbers of rings formed yearly were significantly different between the western and northeastern Mojave regions and western and eastern Mojave regions, but not between the western Mojave region and Colorado Desert. Grouping data from several study sites and years obscured annual variations, however. At Goffs in the eastern Mojave Desert, numbers of rings formed annually differed significantly between 1983, 1984, and 1985. Numbers of tortoises producing 2 rings per year declined between 1983 and 1985, whereas numbers of tortoises with 0 rings per year increased in the same interval. At Goffs, ring formation was positively correlated with annual precipitation, as well as summer and winter rainfall. Correlations between ring counts and biomass of annual plants used for forage were weaker.
Between 1995 and 1998 we studied the effects of water level, moon phase, and site on the number of caimans observed in spotlight surveys in the Mamiraua Sustainable Development Reserve, Brazilian Amazonia. Multiple linear regression analyses including water level of the Amazon River and the moon phase explained 91 and 73% of the variance in number of Melanosuchus niger seen in spotlight surveys in Lago Mamiraua and Cano Mamiraua, respectively, and 60 and 76%, respectively, of the variance in the number of Caiman crocodilus seen. Water level had a statistically significant and negative effect on the number of M. niger and C. crocodilus seen. Moon phase had no significant effect on the number of C. crocodilus seen, but more M. niger were detected in Lago Mamiraua on nights with more moon light. The regression equations derived for Lago Mamiraua and Cano Mamiraua did not adequately predict the variation in numbers seen in 18 other water bodies in the Mamiraua Reserve. Analysis of covariance showed an interaction between water level and site on the numbers of M. niger and C. crocodilus observed in the spotlight surveys in these water bodies, indicating that the effect of water level depends on the site. In these analyses, moon phase did not have a significant effect on either species, and there was no interaction between moon phase and site. To monitor natural tendencies, or impacts (e.g., controlled commercial hunting), on caiman populations of Mamiraua Reserve, it will be necessary to undertake regular spotlight surveys in many water bodies of all types at a narrow range of water level to have confidence in the results.
The technique of counting growth rings to estimate age of turtles is widespread in the scientific literature. Review articles to date have provided primarily lists of authors who have found the technique useful or not, but these reviews have failed to evaluate properly how well the technique actually works. In an attempt to examine how well the published literature supports a biologically meaningful relationship between age and number of growth rings, we surveyed 145 scientific papers that have used counts of rings on scutes to estimate age of individual turtles. Of the 145 papers surveyed, the authors of 44 papers, which comprised 49 case studies, presented data testing the use of growth ring counts for a population of turtles. Of these 49 case studies, 6 reported that the use of the technique was reliable for aging their turtle species past sexual maturity, 15 reported its use to be reliable for aging turtles to young adult (i.e., sexual maturity), 8 reported its use to be reliable for aging juvenile turtles, 2 found it to be reliable with no age limit given, and 8 reported its use unreliable as a method for aging their turtles. The remainder of the case studies presented data that were difficult for us to interpret as reliable or unreliable. Although 22 papers addressed the pattern of growth ring deposition, only four case studies had sufficient data to indicate that a consistent number of rings was added each year. In this paper, we illustrate how the widespread use of this technique ultimately has led to its acceptance without the rigor of tests of its validity or accuracy. We conclude that (a) studies attempting to calibrate the relationship between growth rings and age are few, (b) a majority of the papers that we surveyed referenced other papers that did not themselves include a test justifying growth ring counts as an estimate of turtle age, (c) aging turtles from counts of growth rings might be feasible in some types of studies, for some species at some locations, but only after calibrating the relationship between ring counts and age for each circumstance, and (d) there is currently no justification for generalizing the use of growth rings to estimate turtle age for many species.
Mercury (Hg) concentrations in the Amazon are generally high, but no studies have been published on Hg concentrations in caimans (Alligatoridae) from the region. Aiming for sizes representative of caimans traded for food in the Amazon, we measured Hg concentration in tail muscle of spectacled caiman (Caiman crocodilus crocodilus) and black caiman (Melanosuchus niger) from the Purus River basin. The information on Hg concentration in caimans from this area is important because of the potential health risk to humans and other animals that eat them as well as the potential use of these top-level predators as bioindicators. There were no significant interspecific or sex differences in Hg concentrations. The mean Hg concentration was 291.2 μg/kg in C. c. crocodilus and 193.9 μg/kg in M. niger. A significant positive correlation between Hg concentration and size was found for M. niger (p = 0.005) but not for C. c. crocodilus. Our Hg sample from M. niger corresponded to the size of M. niger collected for commercial trade, but our Hg sample from C. c. crocodilus turned out to be significantly smaller than the trade samples (p = 0.004), but this difference is not pertinent in the absence of a correlation between size and Hg concentration for this species. Although there are no standards for reptile meat, both species had mean Hg concentrations lower than the maximum allowable level of 500 μg/kg Hg recommended by the World Health Organization and by the Brazilian Health Ministry for fish. However, by calculating daily consumptions limits and number of meals per month that can be safely consumed, we found that consumers who eat caimans frequently may be at risk for Hg-related health problems.
A number of environmental factors influence the dynamics of Hg in aquatic ecosystems, yet few studies have examined these factors for turtles, especially from South America. Red-headed river turtle (Podocnemis erythrocephala) is easy to capture in the black waters of Rio Negro, making it the turtle species that is consumed most often by people of the region. In this study, environmental factors and turtle size were investigated to determine their influence on the Hg concentration in blood, muscle, liver and carapace of the red-headed river turtle. Factors investigated included turtle length, pH, dissolved organic carbon and availability of potential methylation sites (floodplain forests and hydromorphic soils). The study was conducted in the Rio Negro basin, where we collected water and turtle blood, muscle, liver and carapace samples from 12 tributaries for chemical analysis. Through radar imagery and existing soil maps with GIS, the percentage of alluvial floodplains and hydromorphic soils (potential methylation sites) was estimated for each drainage basin at sampling points. The mean Hg concentration in blood of P. erythrocephala was 1.64 ng g− 1 (SD = 1.36), muscle 33 ng g− 1 (SD = 11), liver 470 ng g− 1 (SD = 313) and carapace 68 ng g− 1 (SD = 32). Sex or length did not influence the Hg concentration in P. erythrocephala blood, muscle and liver, but Hg increased in carapace tissue when length size increased (ANCOVA p = 0.007). In the multiple regression analysis, none of the environmental factors studied had a significant relation with blood, muscle, liver and carapace. P. erythrocephala moves among habitats and in the open and interconnected aquatic systems of the Amazon basin, characterized by high levels of limnological variability, a good bioindicator of Hg concentration needs to be relatively sedentary to represent a specific habitat. However, the levels of Hg in liver were sufficient to pose a potential risk to humans that consume them, suggesting the usefulness of P. erythrocephala as a bioindicator.
Mercury concentrations in carapace fragments of the green turtle Chelonia mydas from the Ceará coast in NE Brazil are reported. Concentrations varied from <0.34 to 856.6 ng.g(-1) d.w., and were highest (average of 154.8 ng.g(-1) d.w.) in juveniles (n = 22), whereas lowest concentrations (average of 2.5 ng.g(-1) d.w.) were observed in adult/sub-adult animals (n = 3). There was a significant negative correlation between animal size and Hg concentration probably due to different diets between juveniles and sub-adults/adults. Carapace fragments, which are non-invasive, non-lethal substrates, may be of importance for monitoring purposes of these generally endangered species.
Mercury (Hg) deposited onto the landscape can be transformed into methylmercury (MeHg), a neurotoxin that bioaccumulates up the aquatic food chain. Here, we report on Hg concentrations in snapping turtles (Chelydra serpentina) across New York State, USA. The objectives of this study were to: (1) test which landscape, water, and biometric characteristics correlate with total Hg (THg) concentrations in snapping turtles; and (2) determine whether soft tissue THg concentrations correlate with scute (shell) concentrations. Forty-eight turtles were sampled non-lethally from ten lakes and wetlands across New York to observe patterns under a range of ecosystem variables and water chemistry conditions. THg concentrations ranged from 0.041 to 1.50 μg/g and 0.47 to 7.43 μg/g wet weight of muscle tissue and shell, respectively. The vast majority of mercury (~94%) was in the MeHg form. Sixty-one percent of turtle muscle samples exceeded U.S. Environmental Protection Agency (U.S. EPA) consumption advisory limit of 0.3 μg Hg/g for fish. Muscle THg concentrations were significantly correlated with sulfate in water and the maximum elevation of the watershed. Shell THg concentrations were significantly correlated with the acid neutralizing capacity (ANC) of water, the maximum elevation of the watershed, the percent open water in the watershed, the lake to watershed size, and various forms of atmospheric Hg deposition. Thus, our results demonstrate that THg concentrations in snapping turtles are spatially variable, frequently exceed advisory limits, and are significantly correlated with several landscape and water characteristics.
Mercury contamination threatens many ecosystems worldwide. Methylmercury bioaccumulates at each trophic level, and biomagnifies within individuals over time. Long-lived turtles often occupy high trophic positions and are likely to accumulate mercury in contaminated habitats. Millions of turtles worldwide are sold in Asia for human consumption, and consumers may be at risk if turtles contain high levels of mercury. The authors dissected 71 turtles from 14 food trade species and analyzed their tissues (liver, kidneys, muscle, claws, and scutes) for total mercury content. Mercury was generally highest in carnivores, and lowest in herbivores. Liver and scutes had the highest concentrations. The authors compared mercury concentrations with consumption limits developed by the U.S. Environmental Protection Agency and Food and Drug Administration to evaluate mercury in fish tissue. Several samples exceeded the recommended 1,900 parts per billion (ppb) consumption threshold, indicating that consumers who eat certain turtle species frequently may be at risk for mercury-related health problems.
SYNOPSIS. A study of common snapping turtles conducted from 1975 through 1992 in southeastern Michigan provided sufficient demographic data to examine how life history characteristics may constrain population responses of long-lived organisms. Females reached sexual maturity between 11 and 16 years of age. Minimum reproductive frequency was less than annual (0.85), and nest survivorship over 17 years ranged from 0 to 64% and averaged 23%. Survivorship of yearlings had to be estimated since hatchlings can pass through the mesh on traps. Actual survivorship of juveniles was over 0.65 by age 2 and averaged 0.77 between the ages of 2 and 12 years. Annual survivorship of adult females ranged from 0.88 to 0.97. A life table for the population resulted in a cohort generation time of 25 years. Population stability was most sensitive to changes in adult or juvenile survival, and less sensitive to changes in age at sexual maturity, nest survival or fecundity. An increase in annual mortality of 0.1 on adults over 15 years of age with no density-dependent compensation would halve the number of adults in less than 20 years.
The results from the present study indicate that life history traits of long-lived organisms consist of co-evolved traits that severely constrain the ability of populations to respond to chronic disturbances. Successful management and conservation programs for long-lived organisms will be those that recognize that protection of all life stages is necessary. Without protection of adults and older juveniles, programs that protect nests and headstart hatchlings have a low probability of success. Carefully managed sport harvests of turtles or other long-lived organisms may be sustainable; however, commercial harvests will certainly cause substantial population declines
Mercury levels in the Amazon River are generally high, but there are no published studies on Hg levels in turtles from the region. In this study, levels of Hg were examined in the muscle of six species of turtles in the Rio Negro in the Amazon basin of Brazil, including Podocnemis unifilis, Podocnemis expansa, Podocnemis erythrocephala, Podocnemis
sextuberculata,
Peltocephalus dumerilianus, and Chelus fimbriatus. It is important to analyze Hg levels in chelonians in this region because of the potential health risk to humans and other receptors that eat them, as well as their potential use as bioindicators. The effect of sex, weight, and carapace length on Hg concentrations in turtle muscle was examined to determine if the levels represent a health risk to riverine people. There was a significant interspecific difference in Hg levels but no differences as a function of size or gender. The highest Hg level was found in Chelus fimbriatus (mean = 432 ppb, standard deviation ± 196 ppb), followed by Peltocephalus dumerilianus (106 ± 41 ppb), Podocnemis expansa (62 ± 49 ppb), P. sextuberculata (61 ± 40 ppb), P. unilifis (35 ± 17 ppb), and P. erythrocephala (33.1 ± 17 ppb). Of the species studied, the piscivorous C. fimbriatus had the highest Hg level. Hg levels in turtles were similar to the levels found in fish from the same basin. Levels of Hg in the muscle of C. fimbriatus are sufficiently high to pose a potential risk to humans who consume them. This study represents the first comparative study of Hg levels in muscle of six species of turtles.
Concentrations of metals and selenium were examined in tissues of American alligators (Alligator mississippiensis) from three lakes in central Florida, in one of which alligators have exhibited reproductive or developmental defects. Our overall objective was to determine whether the levels of metals were sufficiently high to confound the association between chlorinated hydrocarbons, which are elevated in eggs and juvenile plasma, and reproductive impairment. The concentrations of all metals were relatively low compared to those reported for alligators from elsewhere in Florida and the southeastern United States, suggesting that reproductive impairment is not due to metals and that metals pose no health risk to the alligators. We also wanted to determine whether skin, biopsied tail muscle, or tail tip tissue, all easily collected from live alligators, could be used as surrogate measures of internal tissue loads. Concentrations of arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in liver were highly correlated with at least one of the three biopsied tissues. Only tin showed no significant positive correlation. No single tissue gave a high prediction of liver levels for all metals, although skin gave the highest correlation for mercury, and tail muscle gave the best overall correlation for lead and cadmium.
The dermal influence on the epidermis during scale formation in reptiles is poorly known. Cells of the superficial dermis are not homogeneously distributed beneath the epidermis, but are instead connected to specific areas of the epidermis. Dermal cells are joined temporarily or cyclically through the basement membrane, with the reactive region of the epidermis forming specific regions of dermo-epidermal interactions. In these regions morphoregulatory molecules may be exchanged between the dermis and the connected epidermis. Possible changes in the localization of these regions in the skin may result in the production of different appendages, in accordance with the genetic makeup of the epidermis in each species. Regions of dermo-epidermal interactions seem to move their position during development. A hypothesis on the development and evolution of scales, hairs, and feathers from sarcopterigian fish to amniotes is presented, based on the different localization and extension of regions of dermo-epidermal interactions in the skin. It is hypothesized that, during phylogenesis, possible variations in the localization and extension of these regions, from the large scales of basic amniotes to those of sauropsid amniotes, may have originated scales with hard (beta)-keratin. In extant reptiles, extended regions of dermo-epidermal interaction form most of the expanse of outer scale surface. It is hypothesized that the reduction of large regions of dermo-epidermal interactions into small areas in the skin were the origin of dermal condensations. In mammals, small regions of dermo-epidermal interactions have invaginated, forming the dermal papilla with the associated hair matrix epidermis. In birds, small regions of dermo-epidermal interactions have reduced the original scale surface of archosaurian scales, forming the dermal papilla. The latter has invaginated in association with the collar epidermis from which feathers were produced.
Mercury concentrations in carapace fragments of the green turtle Chelonia mydas from the Ceará coast in NE Brazil are reported. Concentrations varied from <0.34 to 856.6 ng.g -1 d.w., and were highest (average of 154.8 ng.g -1 d.w.) in juveniles (n = 22), whereas lowest concentrations (average of 2.5 ng.g -1 d.w.) were observed in adult/sub-adult animals (n = 3). There was a significant negative correlation between animal size and Hg concentration probably due to different diets between juveniles and sub-adults/adults. Carapace fragments, which are non-invasive, non-lethal substrates, may be of importance for monitoring purposes of these generally endangered species.
The technique of counting growth rings to estimate age of turtles is widespread in the scientific literature. Review articles to date have provided primarily lists of authors who have found the technique useful or not, but these reviews have failed to evaluate properly how well the technique actually works. In an attempt to examine how well the published literature supports a biologically meaningful relationship between age and number of growth rings, we surveyed 145 scientific papers that have used counts of rings on scutes to estimate age of individual turtles. Of the 145 papers surveyed, the authors of 44 papers, which comprised 49 ease studies, presented data testing the use of growth ring counts for a population of turtles. Of these 49 ease studies, 6 reported that the use of the technique was reliable for aging their turtle species past sexual maturity, 15 reported its use to be reliable for aging turtles to young adult (i.e., sexual maturity), 8 reported its use to be reliable for aging juvenile turtles, 2 found it to be reliable with no age limit given, and 8 reported its use unreliable as a method for aging their turtles. The remainder of the ease studies presented data that were difficult for us to interpret as reliable or unreliable. Although 22 papers addressed the pattern of growth ring deposition, only four ease studies had sufficient data to indicate that a consistent number of rings was added each year. In this paper, we illustrate how the widespread use of this technique ultimately has led to its acceptance without the rigor of tests of its validity or accuracy. We conclude that (a) studies attempting to calibrate the relationship between growth rings and age are few, (b) a majority of the papers that we surveyed referenced other papers that did not themselves include a test justifying growth ring counts as an estimate of tulle age, (c) aging turtles from counts of growth rings might be feasible in some types of studies, for some species at some locations, but only after calibrating the relationship between ring counts and age for each circumstance, and (d) there is currently no justification for generalizing the use of growth rings to estimate tulle age for many species.
Stomach contents were collected from 213 Caiman crocodilus with snout-vent lengths (SVL) between 15 cm and 115 cm, and 25 Melanosuchus niger with SVLs from 15 cm to 95 cm, in the Anavilhanas Archipelago, Rio Negro, Central Amazonia. The prey types consumed by the two species were generally similar. However, fish were common in the diet of C. crocodilus but absent from the M. niger. Snails (Pomacea) occurred in 24% of stomachs of M. niger, but in only 2% of C. crocodilus. The mean mass of food and the mean proportion of fish consumed increased, while the mean proportion of terrestrial invertebrates decreased significantly with the size class of C. crocodilus. The mean proportion of molluscs consumed increased significantly with the size class of M. niger, but there was no relationship between the mean mass of food or the mean proportion of other prey categories and size class in this species. However, the sample included only subadults. The mean size of all prey consumed, and of fish, increased significantly with size of C. crocodilus. However, there was no relationship between the mean size of prey in the categories terrestrial invertebrates, shrimps, or crabs, and the size of C. crocodilus. The mean size of all prey consumed was positively related to the size of M. niger. The mean mass of food consumed by C. crocodilus varied with the water body type (lake or canal), but there was no effect of season as indexed by the water level of the Rio Negro. Seasonal variation in the proportion of fish, terrestrial invertebrates, and shrimps consumed by C. crocodilus differed among water body types. Empty stomachs occurred in 24% of the C. crocodilus and 20% of the M. niger. Individuals with food in the stomach had eaten small volumes, suggesting that the caiman are unlikely to impact fisheries in the region.
Caiman crocodilus crocodilus and Melanosuchus niger occur throughout most of the Anavilhanas Archipelago, located in the lower Rio Negro, Central Amazonia. The observed densities of these species vary from 0 to 58 per km of shoreline and 0 to 8 per km of shoreline, respectively. Multiple regression analysis indicated that the temperature difference between the water and the air, and water depth affected the observed density of C. crocodilus during spotlight surveys in the Archipelago. Percentage illumination by the moon, cloud cover, frequency of occurrence of grass, and food availability did not significantly affect the observed density of C. crocodilus. Nine hatchling groups of M. niger that hatched in 1992 were found on islands near the north bank of the Rio Negro, and 15 of 20 hatchlings groups of C. crocodilus were found closer to the south bank, indicating a tendency for separation of nesting areas. Discriminant function analysis indicated that water depth and presence of grass were correlated with the occurrence of hatchling groups. Melanosuchus niger hatchling groups occurred in areas with deeper water and more grass than those of C. crocodilus. This study showed that surveying hatchling groups in the Anavilhanas Archipelago is more efficient than surveying for subadults and adults, which, by itself, can give false impressions about the suitability of areas for conservation of breeding populations of these species.
Rates of growth and survival in wild populations are affected by the physical environment, biotic interactions, and density-dependent processes, such as growth and fecundity. However, the relative importance of these factors in long-lived reptiles is poorly understood. We analyzed growth rates of Melanosuchus niger and Caiman crocodilus coexisting in two areas of the Brazilian Amazon with very different environmental characteristics. Growth rates of Caiman crocodilus at the two sites were similar, but M. niger grew more slowly in the area with higher productivity and higher density of caimans. Growth rates of the same species from other sites and of the temperate-zone Alligator mississippiensis indicate large differences among sites, but little evidence that these differences are primarily due to differences in productivity or temperature. Demographic models used to estimate sustained yields from caiman harvests should take into account the likely importance of density-dependent growth.
Large quantities of mercury are being released into the waters of the Amazon and its tributaries by gold-mining activities. Large releases are also taking place into the air. In this paper, the fate of mercury released to the environment by gold mining in the Brazilian Amazon is reviewed. Mercury contamination is presently widespread in the Amazon region. A major source of mercury in the local environment is the burning of the gold–mercury amalgam, which releases from 30 to 150 t of mercury yearly into the Amazon atmosphere. Air samples collected close to mining sites showed extremely high mercury concentrations (up to 7.5 μg∙m−3). Inside gold-dealers' shops or in amalgam-burning stations, ambient air concentrations may reach 100 μg∙m−3. A secondary source is the discharge of metallic mercury into rivers during the amalgamation process. Sediment concentrations frequently range from 0.3 to 3.0 μg∙g−1 in contaminated sites. However, values as high as 19.8 μg∙g−1 have been reported in some sites. Waters of many rivers are also contaminated, although reliable data on dissolved mercury concentrations are still lacking. Local carnivorous fishes typically show mercury concentrations higher than 1.0 μg∙g wet wt.−1 in contaminated sites and methyl mercury represents over 90% of the total content. Human groups with fish-based diets frequently show evidence of mercury contamination, with high mercury concentrations in hair (up to 70 μg∙g−1). However, a reliable epidemiological study on the affected population still has to be carried out.Key words: mercury, gold mining, Amazon, sediments, aquatic biota, humans.
The distributions of alpha and beta keratins, filaggrin and loricrine are described in crocodilian epidermis by immunocytochemistry and electron microscopy. Many layers of beta keratin cells are produced in the outer surface of the scutes, but in the hinge region between scales they are reduced to thin cells of alpha keratin. Alpha keratins are expressed mainly in the basal and a few suprabasal layers, but disappear in the upper spinosus, prekeratinized and keratinized layers. The production of beta keratin, as studied using an antibody against a chicken scale beta keratin, decreases in hinge regions where alpha keratin, including weak keratin-AE2, filaggrin-like, and loricrin-like immunoreactivities are seen. These immunoreactivities are probably associated with a common, unknown antigen. Beta keratin is deposited on bundles of tonofilaments and desmosomes in cells of the upper part of the stratum spinosus which are turned into electron-pale beta keratin packets with the typical 3-4-nm keratin pattern. Some desmosome remnants are present among beta cells of the stratum corneum. Lipid material is also deposited in early beta-keratinizing cells, especially in the hinge regions where beta keratin is replaced by alpha keratin and thin alpha keratinocytes are produced like in the apteric epidermis of birds. Melanosomes derived from epidermal melanocytes are incorporated in maturing keratinocytes from the lowermost level of the stratum spinosus into the stratum corneum, and this produces the skin pigmentation. Although beta keratinization is similar in both neck (softer scales) and tail verticils (harder scales) a heavier condensation of pale beta packets is present in the larger and spinulated beta cells of the tail epidermis.
In this study, we combined grain size and geochemical analyses with radioisotope analysis of lead-210 (210Pb), caesium-137 (137Cs) and radiocarbon (14C) ages to reconstruct the sedimentation history of two urbanised coastal lagoons in south-east Australia. Towradgi and Fairy
Lagoons were both found to exhibit slow initial sedimentation of less than 1mmyear−1 prior to anthropogenic influences. Land clearing in the catchments increased runoff and erosion in the creeks feeding into
the estuaries, and has resulted in progradation of fluvial material into the estuarine systems with a marked increase in sedimentation
to between 2 and 7mmyear−1. The upper 20–50cm of the sediment column in both lagoons contained elevated concentrations of heavy metals such as Pb,
Cu, Ni and Zn. This pollution trend was found to be consistent with the history of industrialisation and urbanisation in the
region, which expanded rapidly post World War 2. The total metal concentrations were consistent with other urbanised/industrialised
estuaries around the world. Despite the fairly disturbed nature of these coastal lagoons, the use of 210Pb, 137Cs and 14C dating in combination with bulk geochemical analyses allowed detailed reconstruction of sedimentation history.
KeywordsSedimentation rates–Heavy metal contamination–Holocene–Estuarine deposits–
210Pb–
137Cs–
14C
Concentrations of heavy metals (Fe, Mn, Zn, Cu, Pb, Ni, Cd, Co and Hg) were determined in tissues and organs of loggerhead (Caretta caretta) and green turtles (Chelonia mydas) collected from Japanese coastal waters, in order to elucidate body distribution and to develop a non-lethal monitoring technique using the carapace. A majority of the metal burdens was present in the muscle, liver, bone and carapace of sea turtles. High Cu concentrations exceeding 10 μg/g wet wt were observed in the liver of these two turtle species. Mean Zn concentrations in fat tissues of loggerhead and green turtles were 94.6 and 51.3 μg/g wet wt respectively, which were about 10-fold higher than those reported in other marine animals. Concentrations of Mn, Zn and Hg in the carapace were correlated with whole body burdens, indicating that the carapace is a useful non-lethal indicator for monitoring heavy metal levels in the body of the sea turtle.
We have used an ArF excimer laser coupled to a quadrupole inductively coupled plasma mass spectrometry (ICP-MS) for the measurement of a range of elements during excavation of a deepening ablation pit in a synthetic glass (NIST 612). Analyte behaviour shows progressive volatile element enrichment at shallow hole depths, with a change to refractory element enrichment as the ablation pit deepens further. Examination of ablation pit morphology and the surface condensate deposited around the ablation site reveals the importance of sequential condensation of refractory, then volatile phases from the cooling plasma plume after the end of the laser pulse. We interpret the observed element fractionation behaviour to reflect a change in ablation processes from photothermal dominated to plasma dominated mechanisms. The development of the surface deposit is greatly reduced by ablating in an ambient atmosphere of He instead of Ar and is accompanied by a two- to four-fold increase in ICP-MS sensitivity.
The influence of ultraviolet light, heating, freezing and weathering on the mercury concentration in the primary feathers from Guillemot and Black Guillemot has been examined. Even within 8 months of exposure variation in mercury concentration due to either loss of mercury or weight loss of the feathers has been found to be less than 10% relative.
The use of low-volume (7 ml) Teflon vessels and microwave heating is described for the digestion of three marine biological tissues representing a mollusc, a fish and a crustacean. Freeze-dried samples (< 0.1 g dry mass) and 1 ml of nitric acid were placed in 7 ml screw-topped Teflon vessels and treated using a programmed three-stage digestion. The first two stages were kept consistent (600 W, 2 min; 0 W, 2 min) and the third stage was varied from 150 to 450 W over 15-60 min to find the optimum microwave digestion conditions. Trace elements were determined using flame atomic absorption spectrometry, or electrothermal atomic absorption spectrometry when analysing samples containing very low concentrations of cadmium. Quantitative recoveries of copper, zinc and cadmium were obtained from the five marine reference materials under the following conditions: 600 W, 2 mins; 0 W, 2 min; 450 W, 45 mins.
Mercury pollution is a serious problem in some areas of the southeastern United States. Due to biomagnification, long-lived predators should have high Hg concentrations in affected areas. American alligators(Alligator mississippiensis) are important predators in many southwestern wetlands, but little information is available on Hg concentrations in this species. We collected tissues from alligators inhabiting two sites in the Everglades, Florida (n = 18) and a manmade reservoir in South Carolina (Par Pond; n = 44), all with documented histories of Hg contamination, and analyzed them for total Hg. Mean concentrations in kidney, liver, muscle, and dermal scutes of alligators from the Everglades (expressed as mg Hg/kg dry mass +/- S.E.M.) were 36.42 +/- 5.23, 41.09 +/- 5.90, 5.57 +/- 0.47, and 5.83 +/- 1.04, respectively. Concentrations in liver, muscle, and scutes from Par Pond alligators were 17.73 +/- 2.56, 4.08 +/- 0.46, and 4.58 +/- 0.63,respectively. Blood from Par Pond alligators contained 2.20 +/- 0.38 mg Hg/kg wet mass. Mercury concentrations did not differ among sexes at any location. Tissue Hg levels did not differ significantly between Everglades locations,but were lower in Par Pond. In Everglades alligators, Hg concentrations in all tissues were positively correlated, as were tissue Hg and total length. Only total length and scute Hg were correlated in Par Pond alligators. Regression revealed a significant relationship between muscle and scute Hg concentrations in Everglades alligators, but not Par Pond alligators. Alligators living in polluted areas can accumulate substantial concentrations of Hg, but relationships among Hg concentrations in specific tissues may vary with location or age and size of the animals sampled.
Thirty American alligators (Alligator mississippiensis), including 24 wild-caught and six control captive farm-raised alligators, were analyzed for whole body mercury contamination. Wild-caught animals were collected from Water Conservation Area 3 in the Everglades ecosystem (n = 12) and from Alachua, Brevard, and Collier counties outside the Everglades (n = 12). Using cold-vapor atomic absorption spectrophotometry, samples of brain, cervical spinal cord, liver, paired kidneys, paired testes, paired ovaries, paired oviducts, heart, lungs, spleen, bile, tail and leg muscle, and tail and leg scales were analyzed on a wet weight basis to determine mercury concentration. Mercury was consistently detected in all specimens except for bile. Farm-raised alligators, fed a commercially prepared diet, contained very low mercury concentrations in all tissues analyzed. In comparison with alligators from outside the Everglades, Everglades alligators had significantly elevated concentrations of mercury in all tissues analyzed except ovaries, oviduct, bile, tail scales, and leg scales (paired two-sample Student's tau-test, P < 0.05). Muscle concentrations exceeded state (0.50-1.50 ppm) and federal (1.00 ppm) allowances for safe human consumption in alligators collected in the Everglades. No clinical signs of neurologic, hepatic, or renal toxicosis were detected. Because of the alligator's ability to bioaccumulate mercury, this species might be useful as a bio-monitor for environmental mercury contamination.
In order to investigate the major sources and cycling of mercury in the Negro River Basin (Amazon), total metal measurements were carried out in soils, in river and lake waters, in the atmosphere, and in bulk precipitation during the period 1995 throughout 1998. Median values of 1.3 ng m(-3) in the atmosphere, 172 microg kg(-1) in soils, 4.6-7.5 ng l(-1) in three different lakes, 4.5 ng l(-1) in 17 different Negro River tributaries and 20.3 microg m(-2) year(-1) in bulk precipitation were found. Mercury concentrations in rivers and lakes waters, as well as in soils and bulk precipitation were high, considering the scarcity of anthropogenic point sources in the region. Mercury leaching from soil, the largest regional reservoir of this metal, was considered to be the major pathway to mercury enrichment in the region.