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Suntanning in hammerhead sharks [4]

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... High natural UVR levels have deleterious consequences for aquaculture fish species inhabiting shallow waters, such as tanks, ponds, and cages in offshore areas (Bullock, 1982;Rodger, 1991;Lowe and Goodman-Lowe, 1996;Zagarese and Williamson, 2001). Handinger et al. (1997) suggested that UVR can have a significant role in the infection of salmonids by Flexibacter maritimus. ...
... However, when confined, such as occurs with S. aurata in aquaculture cages, fish cannot avoid UVB exposure by moving to lower depths or by sheltering. In fact, significant production losses were previously reported in several fish farms between the 1980 and 1990s, where skin lesions and sunburn in fish from outdoor tanks were indicated as a potential cause for increased mortality rates (Bullock, 1982;Bullock and Coutts, 1985;Lowe and Goodman-Lowe, 1996). Fifteen percent mortality was observed during the first 16 days of the experiment in the UVB-H (UVB doses -11.9 kJ m −2 d −1 ) exposed fish, and about 8% of fish from the UVB-M treatment died during the 43 days of exposure (daily UVB doses -6.1 kJ m −2 d −1 ). ...
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Ultraviolet B (UVB) radiation has recently been recognized as a major stressor for marine vertebrates, particularly fish confined to aquaculture cages. Here, the harmful effects of UVB radiation on gilthead seabream (Sparus aurata), which is a widely cultured species, were investigated. Seabream juveniles were exposed to three UVB conditions (UVB-H – high UVB, 12 kJ m−2 d−1; UVB-M - moderate UVB, 6 kJ m−2 d−1; UVB-L – low UVB, 2.4 kJ m−2 d−1) that are representative of natural underwater UVB levels throughout the water column in the Red Sea. One experimental treatment without UVB exposure was used as a control. The adverse effects of UVB were evaluated after short- (10 days) and long-term (43 days) exposure. The results indicated that short- and long-term exposure to UVB retarded growth and decreased survival rates. UVB exposure resulted in behavioral changes, mainly in UVB-H and UVB-M exposed fish. Swimming activity was reduced; most of the fish tried to avoid exposure and showed a stationary behavior with slow caudal and dorsal fins movements (UVB-H), or a slow displacement behavior (UVB-M). Moreover, a reduction in appetite, reflected by a remarkable increase in the time required to consume the food was observed. Lesions on the skin occurred in the three UVB treatments, and the incidence and severity increased under long-term UVB exposure. Also, physiological changes were observed, including a decrease in total protein and total cholesterol concentrations (all UVB treatments). A potential modulation of the innate immune system (reduction of total anti-protease and total peroxidase activities) was observed (UVB-M, UVB-L). The present results suggest that exposure to solar underwater UVB radiation levels has the potential to interfere and affect the health of S. aurata. Indeed, aquaculture fish species growing at locations where water transparency and UVB incidence is as high as the Mediterranean in summer, and the Red Sea year-round, may be affected, and their welfare, resistance to pathogens, and survival may be compromised. Strategies should be considered to mitigate the adverse effects of UVB exposure, such as deeper and more-shaded cages, or the development of functional foods.
... As one of the most diverse phenotypic traits under strong selection pressure in many organisms, coloration plays numerous adaptive functions such as predator deterrence, species recognition, and even protecting the organism from solar ultraviolet radiation damage (Lowe and Goodman-Lowe, 1996;Parichy, 2006;Roberts et al., 2009;Zhang et al., 2015). Skin coloration can be influenced by many factors, such as genetics, diet, and general health (Wang et al., 2014;Zhang et al., 2015). ...
... Animal coloration plays an important role in ecological interactions, species recognition, and even protecting the organism from ultraviolet radiation damage (Muske and Fernald, 1987;Lowe and Goodman-Lowe, 1996;Fujimura et al., 2009;Sefc et al., 2014). Diverse body coloration is mainly controlled by the development and location of pigment cells. ...
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Pristella maxillaris is known as the X-ray fish based on its translucent body. However, the morphological characteristics and the molecular regulatory mechanisms of these translucent bodies are still unknown. In this study, the following three phenotypes, a black-and-gray body color or wild-type (WT), a silvery-white body color defined as mutant I (MU1), and a fully transparent body with a visible visceral mass named as mutant II (MU2), were investigated to analyze their chromatophores and molecular mechanisms. The variety and distribution of pigment cells in the three phenotypes of P. maxillaris significantly differed by histological assessment. Three types of chromatophores (melanophores, iridophores, and xanthophores) were observed in the WT, whereas MU1 fish were deficient in melanophores, and MU2 fish lacked melanophores and iridophores. Transcriptome sequencing of the skin and peritoneal tissues of P. maxillaris identified a total of 166,089 unigenes. After comparing intergroup gene expression levels, more than 3,000 unigenes with significantly differential expression levels were identified among three strains. Functional annotation and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses of the differentially expressed genes (DEGs) identified a number of candidates melanophores and iridophores genes that influence body color. Some DEGs that were identified using transcriptome analysis were confirmed by quantitative real-time PCR. This study serves as a global survey of the morphological characteristics and molecular mechanism of different body colors observed in P. maxillaris and thus provides a valuable theoretical foundation for the molecular regulation of the transparent phenotype.
... Acoustically tagged C. limbatus showed a preference for the north of the park, and this could explain the absence of recorded sightings in the UAV surveys in the south.The first record of N. brevirostris in CPNP was in 1975, in shallow water close to the shoreline(Reyes-Bonilla et al., 2016). The differences in colouration that were observed between N. brevirostris are likely because of sun-exposure with larger, older sharks exhibiting darker colourations than younger, smaller sharks, as shown in scalloped hammerhead sharks (Sphyrna lewini)(Lowe & Goodman- Lowe, 1996). The presence of neonate N. brevirostris could indicate nearby nursery areas, which are yet to be described for this species in the Gulf of California. ...
Article
Cabo Pulmo National Park was established in 1995 and has since seen a large increase in fish biomass. An unoccupied aerial vehicle (UAV) was used to survey shallow coastal habitat in which lemon sharks (Negaprion brevirostris), bull sharks (Carcharhinus leucas) and Pacific nurse sharks (Ginglymostoma unami) were recorded. Sharks were more common in the afternoon, potentially utilising warmer shallow areas to behaviourally thermoregulate. This study highlights UAV surveying to be a viable tool for species identification, a limitation of previous terrestrial surveys conducted in the area. This article is protected by copyright. All rights reserved.
... In addition to its not so common "bioluminescence function, " shark skin is also known to be a pleiotropic tissue involved in a variety of functions such as senses (e.g., Fields, 2007;Hart and Collin, 2014), protection and hydrodynamics through the placoid scale squamation pattern (e.g., Wainwright et al., 1978;Reif, 1985;Meyer and Seegers, 2012;Oeffner and Lauder, 2012), immunity (e.g., Moore et al., 1993;Tsutsui et al., 2015), and color changes for camouflage or UV protection through melanophore pigment motion (e.g., Lowe and Goodman-Lowe, 1996;Visconti et al., 1999;Robbins and Fox, 2012). ...
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The cookie-cutter shark Isistius brasiliensis (Squaliformes: Dalatiidae) is a deep-sea species that emits a blue luminescence ventrally, except at the level of a black band located beneath the jaw. This study aims to (i) investigate the distribution and histology of the photophores (i.e., light-emitting organs) along the shark body, (ii) describe the tissue-specific transcriptomes of the black band integument region (i.e., non-photogenic) and the ventral integument region (i.e., photogenic), (iii) describe the repertoire of enzyme-coding transcripts expressed the two integument regions, and (iv) analyze the potential expression of transcripts coding for luciferase-like enzymes (i.e., close homologs of known luciferases involved in the bioluminescence of other organisms). Our analyses confirm the black band's non-photogenic status and photophore absence within this region. The sub-rostral area is the region where the photophore density is the highest. In parallel, paired-end Illumina sequencing has been used to generate two pilot transcriptomes, from the black band and the ventral integument tissues of one individual. In total, 68,943 predicted unigenes have been obtained (i.e., 64,606 for the black band transcriptome, 43,996 for the ventral integument transcriptome) with 43,473 unigenes showing significant similarities to known sequences from public databases. BLAST search analyses of known luciferases, coupled with comparative predicted gene expression (i.e., photogenic versus non-photogenic), support the hypothesis that the species uses an unknown luciferase system. An enzymatic repertoire was predicted based on the PRIAM database, and Enzyme Commission numbers were assigned for all detected enzyme-coding unigenes. These pilot transcriptomes based on a single specimen, and the predicted enzyme repertoire, constitute a valuable resource for future investigations on the biology of this enigmatic luminous shark.
... Many fertilized eggs and larvae, as well as visual predators, herbivores and farmed fish obligated to live at the photic surface layer, are potentially exposed to significant UVR radiation. From an economic point of view, several cases of sunburn due to overexposure to high natural solar radiation resulted in numerous losses in aquaculture fish farms during the 1980-1990s, particularly in those where the fish were grown in outdoor tanks (Bullock 1982(Bullock , 1984(Bullock , 1988Bullock and Coutts 1985;Lowe and GoodmanLowe 1996). ...
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Current levels of Ultraviolet Radiation (UVR) represent a significant threat to many fish species. The first studies on the effects of UVR on organisms were performed on fish at the beginning of the twentieth century, and the topic has been progressing continuously until the present. Here, we review the reported harmful effects of ultraviolet B (UVB) and A (UVA) radiations in fish at different lifecycle stages, including embryo, larvae, juveniles and adults. The most evident negative effects during the early development stages are an increase in mortality and incidence in developmental malformations, with the skin and gills the most affected tissues in larvae. Growth reduction, a loss in body condition, and behavioral, physiological and metabolic changes in juveniles/adults occur under short- or long-term UVB exposure. The skin in juveniles/adults undergoes profound morphological and functional changes, even after acute exposure to UVR. Impairment of molecular and cellular processes was evidenced in all development stages by increasing the levels of DNA damage, apoptosis and changing tissues’ antioxidant status. The different photo-protective mechanisms to cope with excessive UVR exposure are also revised. Currently, stratospheric ozone dynamics and climate change interact strongly, enhancing the potential exposure of fish to UVR under water. Due to these environmental changes, fish are exposed to new and complex interactions between UVR and environmental stressors, which potentially affects fish growth and survival. Understanding the ability of fish to cope and adapt to these environmental changes will be essential to evaluate the potential impact in fisheries and mitigate ecological problems.
... 24 Juvenile hammerhead sharks (Sphyrna lewini) have been shown to increase their melanin secretion when exposed to sun, similar to sun tan in humans. 104 Early lifehistory stages of fish tend to be more susceptible to the detrimental effects of ultraviolet radiation. 24 Adult catfish can also be affected by UVA: in a study performed in15 cm water depth and exposure to an artificial UVA light during one hour for three days led to hepatic and cutaneous lesions, highlighted by significant biochemistry and hematologic changes. ...
Article
Many animals under human care are kept indoors to prevent infectious diseases vectored by wildlife, facilitate environment control, or due to the lifestyle of their owners. However, ultraviolet radiation has documented effects on animal vision, vitamin synthesis, immunity, behavior, psychogenic disorders and on their environment. Ultraviolet-emitting lights are commercially available and the documentation of their effect on indoor-housed animals is increasing. This article reviews published information about ultraviolet effects in vertebrate animals from veterinary and ethological perspectives, and techniques used to assess ultraviolet exposure across animal taxa.
... A further example is the case of juveniles of Sphyrna lewini (hammerhead shark), which primarily, as a means of protection against predators and to facilitate obtaining food, stay in shallow-water reef environments, thereby leading to higher sun exposure. Consequently, they present a darker skin when compared to adults, which live in deeper waters (Lowe and Goodman-Lowe, 1996). ...
... In several small-bodied elasmobranch fishes, their ability to camouflage can be modulated according to their environment, with individuals in darker surroundings becoming more pigmented than those in lighter surroundings (Gunn, 2018). In non-camouflaged scalloped hammerheads (Sphyrna lewini), increased pigmentation in the skin and ocular lens protect against oxidative damage from radiation in high-UV habitats (Lowe and Goodmanlowe, 1996;Nelson et al., 2003). While the interaction between neuroendocrine mechanisms and environmental stimuli ultimately underlies the plasticity of body coloration, this has not been studied in detail. ...
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A strength of physiological ecology is its incorporation of aspects of both species’ ecology and physiology; this holistic approach is needed to address current and future anthropogenic stressors affecting elasmobranch fishes that range from overexploitation to the effects of climate change. For example, physiology is one of several key determinants of an organism’s ecological niche (along with evolutionary constraints and ecological interactions). The fundamental role of physiology in niche determination led to the development of the field of physiological ecology. This approach considers physiological mechanisms in the context of the environment to understand mechanistic variations that beget ecological trends. Physiological ecology, as an integrative discipline, has recently experienced a resurgence with respect to conservation applications, largely in conjunction with technological advances that extended physiological work from the lab into the natural world. This is of critical importance for species such as elasmobranchs (sharks, skates and rays), which are an especially understudied and threatened group of vertebrates. In 2017, at the American Elasmobranch Society meeting in Austin, Texas, the symposium entitled `Applications of Physiological Ecology in Elasmobranch Research’ provided a platform for researchers to showcase work in which ecological questions were examined through a physiological lens. Here, we highlight the research presented at this symposium, which emphasized the strength of linking physiological tools with ecological questions. We also demonstrate the applicability of using physiological ecology research as a method to approach conservation issues, and advocate for a more available framework whereby results are more easily accessible for their implementation into management practices.
... Cyclostomes (Group 1) change skin colour in response to environmental light (dark/light) through melatonin secreted by the pineal gland (Joss, 1973); however, we are unaware of reports of quick physiological skin adaptation prompted by changing the surface colour (Figure 3, circle with a red cross). Background adaptation does occur in extant gnathostomes starting in Group 2 (cartilaginous fish; Chondrichthyes) with sharks altering their skin pigmentation to adapt to the "background" colour generated by deep and shallow water (Lowe & Goodman-Lowe, 1996), and continuing through to mammals (Beltran, Burns, & Breed, 2018;Zimova et al., 2018) (Figure 3, black and white circles; see additional references in Table S1). ...
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Different camouflages work best with some background matching colour. Our understanding of the evolution of skin colour is based mainly on the genetics of pigmentation (‘background matching’), with little known about the evolution of the neuroendocrine systems that facilitate ‘background adaptation’ through colour phenotypic plasticity. To address the latter, we studied the evolution in vertebrates of three genes, pomc, pmch and pmchl, that code for α‐MSH and two Melanin Concentrating Hormones (MCH and MCHL). These hormones induce either dispersion/aggregation or the synthesis of pigments. We find that α‐MSH is highly conserved during evolution, as is its role in dispersing/synthetizing pigments. Also conserved is the three‐exon pmch gene that encodes MCH, which participates in feeding behaviours. In contrast, pmchl (known previously as pmch), is a teleost specific intron‐less gene. Our data indicate that in zebrafish, pmchl‐expressing neurons extend axons to the pituitary, supportive of an MCHL hormonal role, whereas zebrafish and Xenopus pmch+ neurons send axons dorsally in the brain. The evolution of these genes, and acquisition of hormonal status for MCHL, explain different mechanisms used by vertebrates to background adapt. This article is protected by copyright. All rights reserved.
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Ultrasonic telemetry was used to determine the movements and distribution of juvenile hammerhead sharks (Sphyrna lewini) on their natal grounds in Kaneohe Bay, Oahu, Hawaii. Transmitters were force fed to six pups which were tracked for periods of up to 12 days. All animals showed a high fidelity to a shared daytime core area to which they repeatedly returned after exhibiting wider ranging nocturnal movements. During daytime, the shark pups formed a loose school which moved about within the core area, hovering about 1.5 m off the bay floor. This daytime refuging behavior may serve an antipredation function. Nighttime movements covered the bay floor and bases of patch and fringing reefs and probably represented foraging excursions. Occasional forays away from the core area also occurred during daytime. The small size of the total activity spaces may indicate a healthy forage base for the sharks. Nocturnal swimming speeds were greater than diurnal swimming speeds.
Chapter
Since its inception, scientific research into the impact of solar ultraviolet (UV) radiation has been confined largely to studies related to the harmful effects of the sun’s rays upon the skin of higher animals, principally that of man (Fitzpatrick, Pathak, Harber, Stizi and Kukita, 1974; Giese, 1976; Magnus, 1976). In recent years such investigations have received a new impetus with the realisation that man’s technical capacity has developed to the point where his ability substantially to modify the stratosphere can no longer remain in doubt. Anthropogenic disturbances of the stratospheric ozone layer, a delicate gaseous interface between stratosphere and troposphere, which shields life on earth from the more extreme effects of solar radiation, could result in an increase of UV reaching the earth with profound effects upon its inhabitants (Grobecker, 1975).
Article
Three major classes of hypotheses have been developed to account for the colors of animals: (1) Selection is for the physical or chemical properties of the biochromes; (2) selection is for color patterns that enhance the animals' own vision; and (3) selection is for colors that serve as optical signals for other animals.
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SYNOPSIS Pigment cells and their synthesized products play an important functional role in the skin of most all vertebrates, from cyclostomes to man Both dermal and epidermal pigment cells function in physiological and morphological color changes and provide the cellular basis for vertebrate pigment patterns and differences in racial coloration Epidermal melanization is of particular importance in homeotherms in the regulation of seasonal pelage and feather color changes In addition, melanin pigmenta tion may have a photoprotective function, influence vitamin D synthesis in the skin protect or influence neivous system function, affect heat absorption and consenition, play an intracellular homeostatic role in the skin and (by leucocytic transport) elsewhere in the bodv and provide a structural element to the integument A consideration of the comparative evolution of the vertebrate lntegumental pigmental) system may be necessary for a pioper interpretation of the supposed roles ot melanin and other lntegumental pigments
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The results indicate a major role for MSH in melanogenesis in the elasmobranchs. The skin melanophores require the presence of MSH for their maintenance or they degenerate, leaving only the static epidermal pigment. The melanin content falls to some 50% of that in the control fish in a period of 6 mth (P < 0.005). Conversely, a high level of circulating MSH, caused by uninhibited release of MSH, more than doubles the melanin content of the skin in 6 mth (P < 0.001). The role of other melanogenic agents, ACTH, prolactin and thyroxine, was not investigated and it was assumed that their release would be unaffected by the surgical procedures employed.