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The Role of Grass Shrimp, Palaemonetes pugio, in a Tidal Marsh Ecosystem
Ecology
Abstract
The grass shrimp, Palaemonetes pugio, is a dominant species uniquely adapted to a highly stressed tidal marsh embayment. Monthly sampling of length and dry weight revealed that its life cycle was a single year, with spawning in May, June, and July and most rapid growth in late summer and fall. Mark and recapture estimates conducted quarterly and quadrat net estimates calculated monthly indicated that shrimp were present throughout the year and that densities peaked in the fall (over 1.2 million in 0.01 km2 in October). Production of biomass (growth) equated loss to predation (including decomposition) over the annual cycle, averaging 0.2 kcal@?m^-^2@?day^-^1. Respiration averaged 1.1 kcal 1.1 kcal@?m^-^2@?day^-^1. Average daily production per square meter of "total consumables" (fecal pellets = 0.8 kcal, dissolved organic matter [DOM] = 0.7 kcal, biomass = 0.2 kcal) was 60% of total ingestion (2.9 kcal); production of feces and DOM thus outweighed biomass production 15:2. Microcosm studies and observations by scanning electron microscope revealed that shrimp macerated detritus into a heterogeneous assortment of uneaten particles by plucking away the cellular matrix from surfaces of large detrital fragments. This action provided cavities that became heavily invaded by pennate diatoms, and particles that became suspended in the water column and populated by bacteria. Nutrient analyses indicated the shrimp excreted large quantities of ammonia and phosphate which together with DOM release was presumably responsible for heavy growth of microflora and increased protein fraction in both feces and large and small uneaten detrital fragments. Palaemonetes pugio, while supporting its own trophic requirements, accelerated breakdown of detritus, preventing blockages or accumulations that might have occurred from pulses of emergent grass and macroalgal detritus in the embayment. This repackaging into feces, heterogeneous fragments, DOM, and shrimp biomass made detrital energy available at a variety of trophic levels, smoothing out organic pulses over time and space, and raising the efficiency of transfer to the food web. The special adaptation of P. pugio to the low-oxygen environment of the decomposer system appeared to limit predation and competition, allowing the shrimp to develop large populations necessary to carry out its role effectively.
... The grass shrimp, Palaemon pugio (Holthuis, 1949), is a caridean shrimp widely distributed along the western Atlantic Ocean and Gulf of Mexico coastlines in estuarine habitats (Anderson, 1985;Kneib, 1987;Macías, 2012;Schreiber et al., 2019;Espinoza & Bremer, 2023). Palaemon pugio spawns between May and July; adults are present year-round, with the highest densities typically being found in the fall (Welsh, 1975;Ganz & Knowlton, 2002;Cházaro-Olvera, 2009). Grass shrimp commonly occur in highly fluctuating habitats and experience changes in oxygen levels and salinity (Welsh, 1975;Rowe, 2002). ...
... Palaemon pugio spawns between May and July; adults are present year-round, with the highest densities typically being found in the fall (Welsh, 1975;Ganz & Knowlton, 2002;Cházaro-Olvera, 2009). Grass shrimp commonly occur in highly fluctuating habitats and experience changes in oxygen levels and salinity (Welsh, 1975;Rowe, 2002). They can be found in waters with salinity < 1 g kg −1 and > 40 g kg −1 , but have the greatest abundance in waters with salinity ranging 10-20 g kg −1 (Wood, 1967;Thorp & Hoss, 1975;Knowlton & Kirby, 1984;Barba et al., 2005). ...
... They can be found in waters with salinity < 1 g kg −1 and > 40 g kg −1 , but have the greatest abundance in waters with salinity ranging 10-20 g kg −1 (Wood, 1967;Thorp & Hoss, 1975;Knowlton & Kirby, 1984;Barba et al., 2005). Although grass shrimp have little to no commercial value, they have key ecological roles as prey for fishes and as part of the detrital food web (Welsh, 1975;Mason & Zengel, 1996;Clark et al., 2003). ...
Estuarine environments often undergo fluctuations in dissolved oxygen and salinity. Two experiments were performed, one with the penaeid shrimp Penaeus aztecus at two life stages (juvenile, adult) under constant normoxia conditions or diel cycled hypoxia for 2 weeks. The second experiment was with the caridean shrimp Palaemon pugio at two salinity levels (15 g kg⁻¹ and 5 g kg⁻¹) under constant normoxia conditions or diel cycled hypoxia for 2 weeks. After experimentation, partial bioenergetic composition and oxygen consumption were quantified. Cycled hypoxia had no effect on body composition (protein or lipid in P. aztecus, protein in P. pugio), or oxygen consumption in both experiments, suggesting both species are well adapted to short-term fluctuations in dissolved oxygen. Juvenile P. aztecus had higher percent lipid compared to adults, with no difference in percent protein composition. Palaemon pugio in the 5 g kg⁻¹ salinity group had higher oxygen consumption compared to the 15 g kg⁻¹ salinity group. Salinity had no effect on bioenergetic composition. There were no interactions between the factors in both experiments. Hyposalinity may be a stressor for P. pugio; however, the occurrence of salinity stress and short-term cyclic hypoxia together do not appear to affect one another.
... Parasitic isopods are a common group of crustaceans and can act as ectoparasites on several taxa (Leonardos and Trilles, 2003;Welicky and Sikkel, 2014) including salt marsh shrimp species, such as the ecologically important daggerblade grass shrimp (Palaemon [previously Palaemonetes] pugio; see De Grave and Ashelby, 2013). Daggerblade grass shrimp are endemic to salt marshes along the western Atlantic and throughout the Gulf of Mexico (Welsh, 1975;Collins, 1981;Anderson, 1985). Palaemon pugio, hereafter referred to as grass shrimp, plays a critical role in salt marsh food webs as prey for a variety of shorebirds, crabs, and finfish, including commercially important species (Heard and Lutz, 1982;Manderson et al., 2000). ...
... Palaemon pugio, hereafter referred to as grass shrimp, plays a critical role in salt marsh food webs as prey for a variety of shorebirds, crabs, and finfish, including commercially important species (Heard and Lutz, 1982;Manderson et al., 2000). Depending on their life stage and food availability, grass shrimp act as opportunistic omnivores or detritivores, influencing multiple trophic levels (Welsh, 1975;McCall and Rakocinski, 2007). Additionally, grass shrimp influence salt marsh structure, functioning, and dynamics through their feeding behavior and movement. ...
... Additionally, grass shrimp influence salt marsh structure, functioning, and dynamics through their feeding behavior and movement. For instance, grass shrimp can indirectly increase macrophyte productivity by grazing on epiphytes that inhibit photosynthetically active radiation and can also increase nutrient availability to macrophytes and microbes via bioturbation and fecal deposition (Welsh, 1975;Sikora, 1977;McCall and Rakocinski, 2007). ...
In salt marsh ecosystems, daggerblade grass shrimp, Palaemon (Palaemonetes) pugio, play a crucial role in food webs and serve as the definitive host for the bopyrid isopod Probopyrus pandalicola. These ectoparasites infest the branchial chambers of grass shrimp, which can lead to decreased energy availability and sterilization of infected hosts. Although bopyrid isopod infestation of daggerblade grass shrimp has been frequently reported in literature from coastal marshes of the southeastern United States, the prevalence of this parasite has not been recently documented in daggerblade grass shrimp from marshes of the northeastern United States. The goal of this project was to quantify the prevalence of Pr. pandalicola infestations in Pa. pugio across Cape Cod, Massachusetts. We evaluated bopyrid isopod prevalence from shrimp collected from 5 different salt marsh habitats along Cape Cod in August 2021. Bopyrid isopod infestations were found in shrimp at 4 of 5 salt marshes, with prevalence ranging from 0.04 to 14.1%. Seasonal resampling of one of the salt marshes revealed the highest average infestation prevalence in spring (<17.1%) and an isolated high of 30.3% prevalence in a single salt panne. A series of linear and multivariate models showed that panne area, shrimp abundance, and distance to shoreline were related to Pr. pandalicola shrimp infestations in salt pannes in summer. This study describes the prevalence of the bopyrid isopod infesting daggerblade grass shrimp in salt marshes in New England, with implications for how parasitized shrimp influence salt marsh food webs in which they are found.
... Grass shrimp (Palaemonetes pugio) are among the few highly abundant benthic invertebrates in salt marshes of the eastern United States that tolerate wide fluctuations in salinity, water temperature, and oxygen levels. 27,28 They are important prey for many juvenile and adult fish and are considered a keystone species in salt marshes. 27,29,30 Grass shrimp are opportunistic omnivores that mainly consume benthic invertebrates, but also plant detritus, epiphytes, and benthic diatoms. ...
... 27,28 They are important prey for many juvenile and adult fish and are considered a keystone species in salt marshes. 27,29,30 Grass shrimp are opportunistic omnivores that mainly consume benthic invertebrates, but also plant detritus, epiphytes, and benthic diatoms. 27,31 As such, grass shrimp represent a potential trophic link between bioavailable MeHg in salt marshes and higher trophic-level animals, including the YOY of various fish species such as striped bass, summer flounder, and bluefish. ...
... 27,29,30 Grass shrimp are opportunistic omnivores that mainly consume benthic invertebrates, but also plant detritus, epiphytes, and benthic diatoms. 27,31 As such, grass shrimp represent a potential trophic link between bioavailable MeHg in salt marshes and higher trophic-level animals, including the YOY of various fish species such as striped bass, summer flounder, and bluefish. 25,26 However, only a few studies reported concentrations of total Hg (THg) 32−34 or MeHg 34,35 in grass shrimp from salt marsh ecosystems. ...
Grass shrimp (Palaemonetes pugio) represent a potential link in the transfer of methylmercury (MeHg) from salt marsh sediments to transient young-of-the-year (YOY) fish. Across six salt marshes subject to varying degrees of Hg contamination, MeHg concentration in grass shrimp was significantly correlated with MeHg in sediment (p < 0.05, R2 = 0.81). Bioenergetic models show that grass shrimp alone account for 12-90% of MeHg observed in YOY striped bass and 6-22% of MeHg in YOY summer flounder. Direct accumulation of MeHg from grass shrimp to YOY fish increased with MeHg levels in grass shrimp and sediment. However, in the most contaminated salt marshes with the highest levels of MeHg in grass shrimp and sediment, indirect accumulation of MeHg from grass shrimp by YOY summer flounder, whose diet is dominated by benthic forage fish (mummichog), is predicted to plateau because higher concentrations of MeHg in grass shrimp are offset by a lower proportion of grass shrimp in the mummichog diet. Our results demonstrate that grass shrimp are an important trophic link in the bioaccumulation of MeHg in salt marsh food webs and that MeHg accumulation in YOY fish varies with both the concentration of MeHg in salt marsh sediments and benthic food web structure.
... Within the Lymington marshes, UK, the ditch shrimp Palaemon varians Leach (1814), was chosen as a model due to its key ecological role in the ecosystem (Aguzzi, Cuesta, Librero, & Toja, 2005). In fact, in European marshes, export of organic material is largely absent (Cattrijsse & Hampel, 2006) and decaying marsh flora are processed by detritivorous species, such as P. varians, which plays a fundamental role in transfer of nutrients and energy in the ecosystem (Aguzzi et al., 2005;Welsh, 1975). We demonstrated that the exposure to a daily cyclic hypoxic regime (of 7 hr per day in hypoxia) induced changes in the transcriptome of the entire cephalothorax (not limited to cuticle and hypodermis but including hepatopancreas and all major organs) after 7 days. ...
... salt marshes), in particular on nutrient cycling and energy fluxes. P. varians has been reported to play a key ecological role in macerating detritus and dead marsh plants and in excreting large quantities of ammonia (Aguzzi et al., 2005;Escaravage & Castel, 1990;Welsh, 1975), thus making energy available at a variety of trophic levels and supporting significant growth of microflora (Welsh, 1975). Therefore, a reduced excretion of ammonia due to cyclic hypoxia in the environment may alter nutrient turnover and, in turn, affect the microbial community of the salt marsh. ...
... salt marshes), in particular on nutrient cycling and energy fluxes. P. varians has been reported to play a key ecological role in macerating detritus and dead marsh plants and in excreting large quantities of ammonia (Aguzzi et al., 2005;Escaravage & Castel, 1990;Welsh, 1975), thus making energy available at a variety of trophic levels and supporting significant growth of microflora (Welsh, 1975). Therefore, a reduced excretion of ammonia due to cyclic hypoxia in the environment may alter nutrient turnover and, in turn, affect the microbial community of the salt marsh. ...
Salt marshes are a key coastal environment for their important role as nursery habitats for marine and estuarine fish and crustaceans. Salt marshes are variable environments where species can experience daily cyclic hypoxic stress, characterised by profound variations in oxygen partial pressure ( pO 2 ) from supersaturated conditions (~42 kPa) to extremely hypoxic conditions (~3 kPa) in ~12‐hr.
Here, under laboratory conditions, we assessed the physiological consequences of exposing the shrimp Palaemon varians, a species commonly found in the salt marshes of northern Europe, to the daily cyclic hypoxic regime currently experienced in its habitat in August (7.1 ± 1.8 hr/day below 4.0 kPa). In the laboratory, adults were kept at water pO 2 < 4.5 kPa for 7 hr each night and in normoxic conditions for the rest of the time.
We recorded an acceleration of P. varians ’ moult cycle, which was 15% shorter in animals kept in cyclic hypoxia compared to animals in normoxia. Similarly, the pattern of expression of two cuticular proteins over an entire moult cycle indicated an effect of cyclic hypoxia on moult stage‐related genes. After 16 days, morphological changes to the gills were detected, with shrimps in cyclic hypoxia having a 13.6% larger lamellar surface area (measured in μm ² /mg animal) than normoxic animals, which could improve gas exchange capacity. Overall, phenotypic and morphological data indicate that faster moulting is triggered in response to cyclic hypoxia, with the benefit that gill modifications can be prompted more rapidly in order to meet oxygen requirements of the body.
On the first experimental day, in cyclic hypoxic‐exposed animals, we recorded a 50% decrease in feeding rates (during hypoxic conditions) in comparison with normoxic animals. Similarly, ammonium excretion was reduced by 66%–75% during the 1st and 21st experimental day. Body size was reduced by ~4% after 28 days. Females that reproduced in cyclic hypoxic conditions reduced the amount of yolk in each egg by ~24%. Overall, results underline how, in a decapod shrimp living in a key coastal environment, many physiological parameters are impaired by a cyclic hypoxic regime that is currently found in its natural habitat.
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... De los datos del presente estudio se deduce que P. zariquieyi es una especie de ciclo biológico anual; e igualmente un ciclo anual ha sido descrito para P. paludosus (Beck & Cowell, 1976); P. kadiakensis (Meehann, 1936;y Nielsen & Reynolds, 1977); y P. pugio (Welsh, 1975). Estos autores también resaltan el que algunos pocos individuos de estas especies puede que alcancen a vivir el invierno posterior al de su periodo de reproducción, al igual como sucede para con P. zariquieyi, especialmente en la localidad de Torrente. ...
... El crecimiento de P. zariquieyi no se detiene a lo largo de su ciclo biológico, ni tan siquiera durante los meses invernales, cuando la temperatura de las aguas son más bajas. Welsh (1975) señaló un crecimiento similar en P. pugio; pero indicando que en los meses centrales de su ciclo (invierno) el crecimiento era prácticamente nulo. En el punto B (Sagunto) el tamaño medio alcanzado por los camarones es mayor que en las otras dos localidades, aspecto que hay que atribuir a las condiciones tróficas allí existentes, con gran diversidad de vegetación, habitat natural de estos camarones. ...
... que ocurre en P. pzcgio (Welsh, 1975), P. paludosiis (Beck & Cowell, 1976), en P. kadiakensis (Nielsen & Reynolds, 1977), y en P. antennariz~s (Hofer et al., 1980). Ello no se aprecia de las muestras de Caste-Ilón, debido a las peculariedades de esta población, en la que constantemente existen juveniles incorporándose a la misma. ...
... The daggerblade grass shrimp Palaemonetes pugio Holthuis, 1949 is prevalent in estuaries along the East and Gulf coasts of the United States (Johannes & Satomi, 1966;Welsh, 1975;Sikora, 1977;Anderson, 1985). Palaemonetes pugio plays a pivotal role in the estuarine food web as it transfers energy between trophic levels by facilitating the breakdown of decaying marsh plants (Welsh, 1975). ...
... The daggerblade grass shrimp Palaemonetes pugio Holthuis, 1949 is prevalent in estuaries along the East and Gulf coasts of the United States (Johannes & Satomi, 1966;Welsh, 1975;Sikora, 1977;Anderson, 1985). Palaemonetes pugio plays a pivotal role in the estuarine food web as it transfers energy between trophic levels by facilitating the breakdown of decaying marsh plants (Welsh, 1975). Furthermore, 60% of the material ingested by the shrimp is repackaged into protein-rich fecal pellets that can be utilized by organisms at various trophic levels (Welsh, 1975). ...
... Palaemonetes pugio plays a pivotal role in the estuarine food web as it transfers energy between trophic levels by facilitating the breakdown of decaying marsh plants (Welsh, 1975). Furthermore, 60% of the material ingested by the shrimp is repackaged into protein-rich fecal pellets that can be utilized by organisms at various trophic levels (Welsh, 1975). Palaemonetes pugio is an opportunistic omnivore that feeds primarily on organic and inorganic particles, benthic diatoms, dinoflagellates, ostracods and copepods (Odum & Heald, 1972), and it is a food source for other crustaceans and fish. ...
The daggerblade grass shrimp Palaemonetes pugio Holthuis, 1949 is prevalent in estuaries along the East and Gulf coasts of the United States, and is an integral part of the estuarine food web. Probopyrus pandalicola (Packard, 1879) is a bopyrid isopod that parasitizes P. pugio and decreases the energy available to its host by feeding on the hemolymph of the shrimp. The parasite also causes female shrimp to be castrated. The purpose of this study was to determine the effect of Probopyrus pandalicola on the survival time of P. pugio during starvation at two different temperatures. The experiment was conducted between September 2009 and June 2012 at 20.0 +/- 0.11 degrees C and 25.0 +/- 0.10 degrees C. Three trials at each temperature were performed. For each trial, parasitized, deparasitized and unparasitized shrimp were randomly placed into individual aquaria in a temperature-controlled chamber. All trials lasted until 100% shrimp mortality occurred. The bopyrid isopod did have a significant effect on shrimp survival times, but only at the higher temperature during which parasitized shrimp survived a significantly shorter amount of time (21.8 +/- 6.93 days) than unparasitized shrimp (25.2 +/- 8.25 days). In contrast, the bopyrid did not have a significant effect on shrimp survival times at the lower temperature, with shrimp surviving an average of 26.9-27.5 days. The results of this study have implications related to potential climate change, specifically higher temperatures, as we found that a small increase in temperature significantly affected the response of P. pugio to the isopod parasite. This supports prior research on other host-parasite interactions that are affected by increased temperature.
... Due to their high biomass and abundance (Welsh 1975), daggerblade grass shrimp (P. pugio) are an ecologically important species in tidal creeks, marshes, and estuaries throughout the Atlantic and Gulf coasts, from Massachusetts south to Texas (Welsh 1975;Heard and Lutz 1982). ...
... Due to their high biomass and abundance (Welsh 1975), daggerblade grass shrimp (P. pugio) are an ecologically important species in tidal creeks, marshes, and estuaries throughout the Atlantic and Gulf coasts, from Massachusetts south to Texas (Welsh 1975;Heard and Lutz 1982). Grass shrimp act as important detritivores and predators, as well as prey, allowing nutrients to move from lower to higher trophic levels (Posey and Hines 1991). ...
A conflict of interest occurs when parasites manipulate the behavior of their host in contradictory ways to achieve different goals. In grass shrimp (Palaemonetes pugio), trematode parasites that use shrimp as an intermediate host cause the shrimp to be more active than usual around predators, whereas bopyrid isopod parasites that use shrimp as a final host elicit the opposite response. Since these parasites are altering the host’s behavior in opposing directions, a conflict of interest would occur in co-infected shrimp. Natural selection should favor attempts to resolve this conflict through avoidance, killing, or sabotage. In a field survey of shrimp populations in four tidal creeks in the Cape Fear River, we found a significant negative association between the two parasites. Parasite abundance was negatively correlated in differently sized hosts, suggesting avoidance as a mechanism. Subsequent mortality experiments showed no evidence of early death of co-infected hosts. In behavior trials, co-infected shrimp did not show significantly different behavior from singly infected or uninfected shrimp, suggesting that neither parasite sabotages the manipulation of the other. Taken together, our results suggest that rather than sabotaging or killing one another, bopyrid and trematode parasites tend to infect differently sized hosts, thus avoiding a conflict and confirming the importance of testing assumptions in natural contexts.
... The grass shrimp (Palaemonetes pugio) is an important benthic-pelagic coupler (benthic feeding predator that is prey to more pelagic species) in the Hudson River Estuary (Welsh 1975). Grass shrimp play a vital role in estuarine food webs as they link benthic associated carbon (and pollutants) to higher trophic levels since they are important components of the diets of several finfish, including the mummichog and striped bass (Welsh 1975;Davis et al. 2003). ...
... The grass shrimp (Palaemonetes pugio) is an important benthic-pelagic coupler (benthic feeding predator that is prey to more pelagic species) in the Hudson River Estuary (Welsh 1975). Grass shrimp play a vital role in estuarine food webs as they link benthic associated carbon (and pollutants) to higher trophic levels since they are important components of the diets of several finfish, including the mummichog and striped bass (Welsh 1975;Davis et al. 2003). Feeding experiments with P. pugio using oligochaete prey collected from Cd-contaminated sites have established that grass shrimp can accumulate toxic metals from ingested prey, can induce MT upon metal exposure, and the accumulated metal can be transferred to their predators (Wallace et al. 2000;Seebaugh et al. 2005). ...
In marine invertebrates, reliance upon metallothionein (MT) for toxic metal detoxification may lead to enhanced trophic transfer of metals. MT concentrations were determined in grass shrimp (Palaemonetes pugio) collected from metal contaminated field sites along an established metal impact gradient in Staten Island, NY, (field exposure), as well as in naïve P. pugio from a relatively pristine site in Tuckerton, NJ, that were fed prey from the same set of contaminated Staten Island sites via a feeding experiment (dietary exposure). MT concentrations in P. pugio collected from the Staten Island sites were elevated in comparison to naïve P. pugio from a pristine site in Tuckerton, NJ; however, the concentrations did not vary among shrimp from the impacted sites, possibly due to confounding effects of exposure to an array of contaminants, greater MT turnover or decreasing reliance on MT with increasing metal exposure. MT concentrations in naïve P. pugio fed prey from the same sites did not present increases in MT concentration over control following 3 weeks of feeding. For three of four sites, dietary exposure to metals may in large part account for MT induction in grass shrimp, as MT concentrations in field-collected at experimentally fed shrimp for these sites were similar. For one site in the former Fresh Kills landfill, MT concentration in field-collected shrimp was significantly higher, indicating that chronic environmental exposure at this site may supersede dietary exposure in the induction of MT in P. pugio. In order to parse the impact of metal exposure on MT concentration, analyses of whole body metals burden and trophically available metals, such as those bound to MT, organelles and heat-sensitive proteins, in the field-collected and dietarily exposed P. pugio is required.
... Such depauperate levels of variation in Texas described herein collectively represent only a snapshot of the total mtDNA variation observed for the northern Gulf, and could be explained by either founder events [111,112] or sweepstakes in reproductive success (i.e., SRS or the Hedgecock effect) [96]. P. pugio females are highly fecund, capable of producing 100 s of eggs per spawning event, which are repeated multiple times per season [44][45][46]. Additionally, while actual population densities of P. pugio have been reported to be as high as 1.2 million individuals per 0.01 km 2 in a single marsh [44], this study estimated N ef to be 1.9-2.4 million for the entire range sampled, from Mississippi to Texas (Table 11). ...
... P. pugio females are highly fecund, capable of producing 100 s of eggs per spawning event, which are repeated multiple times per season [44][45][46]. Additionally, while actual population densities of P. pugio have been reported to be as high as 1.2 million individuals per 0.01 km 2 in a single marsh [44], this study estimated N ef to be 1.9-2.4 million for the entire range sampled, from Mississippi to Texas (Table 11). This dramatic reduction in N ef in comparison to actual population numbers, combined with high fecundity and Type III life history of P. pugio, is concordant with expected outcomes based on the SRS hypothesis. ...
Coastal wetlands worldwide are experiencing high rates of loss and degradation that may lead to a reduction in diversity in faunal populations. Since salt marsh habitats are subject to a multitude of stressors, evaluations of the genetic diversity, connectivity, and potential resilience of faunal communities within salt marsh habitats are relevant. This study characterizes mitochondrial DNA (mtDNA) diversity for three common faunal residents of salt marshes along the northern Gulf of Mexico. Gulf Killifish (Fundulus grandis) samples were characterized for 1077 bp of the concatenated nucleotide sequence corresponding to the Control Region and Nitrogen Dehydrogenase, Subunits 2 and 5. Daggerblade grass shrimp (Palaemon pugio) samples were characterized using 466 bp of 16sRNA sequence, and phloem-feeding planthoppers (Prokelisia marginata) were characterized using 372 bp of Cytochrome c Oxidase Subunit I (COI) sequence. For F. grandis, our data revealed high levels of haplotypic diversity, evidence of isolation by distance (IBD), and regional population structuring associated with the distribution of two distinct phylogroups and distinct historical demography signatures. P. pugio and P. marginata displayed low levels of haplotypic diversity and evidence of population structure, but both appear to contain only snapshots of the total potential diversity for these species in the Gulf of Mexico. Greater resolution of the patterns of historical demography of Gulf Killifish may be obtained in future studies by including localities from Florida and Mexico. For both P. pugio and planthoppers, future studies would benefit from the characterization of genetic markers with a higher degree of polymorphism. We conclude that despite these three species inhabiting the same habitats along the same stretch of coast, each is subject to a different combination of evolutionary forces, and this study was able to reconstruct differences in how the genetic variation in each of these species emerged, and how it is maintained.
... Estuarine ecosystems are typically dynamic, especially in temperate waters, and comprised of a diverse community of resident and transient species. These can include several abundant shrimp species which are vital to the system as prey (Able and Fahay 2010), predators during different life stages , Bass et al. 2001, Locke et al. 2005, Taylor 2005, Taylor and Danila 2005, Taylor and Peck 2004, processors of plant production (Welsh 1975), and commercially important bait (Townes 1938). Although shrimp are a critical link in the estuarine food web, relatively little work has been done to determine their species composition and examine their life histories in estuaries along the east coast of the US. ...
... Some shrimp species also play a role in detritus decomposition and nutrient cycling. For instance, Palaemonetes pugio Holthuis ( = Palaemon pugio; De Grave and Ashelby 2013) (Daggerblade Grass Shrimp) accelerates the breakdown of detritus and makes detrital energy more readily available to several trophic levels (Welsh 1975). Prior research in the study area have only identified Marsh Grass Shrimp (Rountree andAble 1993, Wilson andAble 1995) or recognized 3 species: Marsh Grass Shrimp, Daggerblade Grass Shrimp, and Palaemon intermedius (Stimpson) (Able et al. 2018). ...
... None of the other 8 taxa in the best-fitting model loaded in a direction similar to F. heteroclitus or L. rhomboides. Palaemonetes spp., a dominant crustacean taxa in tidal creeks in this region (Welsh 1975), loaded in a direction similar to samples from deeper sites but at an intermediate distance to salt marsh. The majority of the 6 other taxa in the bestfitting model loaded in a direction generally similar to Palaemonetes spp. ...
... L. rhomboides was the dominant transient species in this study and a habitat generalist (Jordan et al. 1997). Ordination results for Callinectes sapidus and Palaemonetes spp., crustaceans important to salt marsh trophic dynamics (Welsh 1975, Kneib & Knowlton 1995, Silliman & Bertness 2002, suggest that they also respond to common types of instream development in salt marsh systems. This is consistent with recent studies that have found that shoreline armoring reduces the habitat value for C. sapidus (Long et al. 2011) and that intact salt marsh mosaics support greater abundances of Palaemonetes spp. ...
The specific biological impacts of anthropogenic activities and associated fragmentation of estuarine habitats remain understudied. We compared nekton communities and fish movement at 9 road crossings (with culverts) and a tenth crossing ('reference' crossing that lacked a road or a culvert) in first-order Spartina alterniflora-dominated tidal creeks in coastal North Caro lina. Sample sites were located on both sides of each crossing. Percent salt marsh and increasing water depth were factors that most contributed to dissimilarities in biological communities among sample sites; the resident salt marsh fish Fundulus heteroclitus dominated the catch at sites with high percentages of marsh and inherently shallow depths while a transient species Lagodon rhomboides dominated at deeper sites where marsh was absent. F. heteroclitus was marked with injectable elastomer to determine factors influencing its movement probability to sites on sides of crossings opposite from where it was tagged. The probability of F. heteroclitus moving was positively related to the percentage of marsh-fringed shoreline within its published home range and was highest at intermediate water depths. The results show that preserving salt marsh adjacent to road crossings will maintain communities and movement rates reflective of nonimpacted habitats in tidal creeks in the US South Atlantic coastal plain and emphasize habitat connectivity as an ecological factor important to community structure and movement.
... by eating it and then converting it into feces, dissolved organic matter (DOM), or shrimp biomass (Welsh, 1975). These converted forms of energy are then available to many other organisms in the food web, such as bacteria, diatoms, detritivores, and carnivores (Welsh, 1975). ...
... by eating it and then converting it into feces, dissolved organic matter (DOM), or shrimp biomass (Welsh, 1975). These converted forms of energy are then available to many other organisms in the food web, such as bacteria, diatoms, detritivores, and carnivores (Welsh, 1975). In addition to providing food for other organisms, grass shrimp can be a host to several parasites. ...
... The daggerblade grass shrimp Palaemonetes pugio Holthuis, 1949[currently accepted as: Palaemon pugio (Holthuis, 1949] is an epibenthic macroinvertebrate that is abundant in estuaries on the Atlantic and Gulf coasts (Welsh, 1975;Anderson, 1985). Grass shrimp play a crucial role in estuarine ecosystems because they facilitate the trophic transfer of nutrients that are stored in detritus (Welsh, 1975). ...
... The daggerblade grass shrimp Palaemonetes pugio Holthuis, 1949[currently accepted as: Palaemon pugio (Holthuis, 1949] is an epibenthic macroinvertebrate that is abundant in estuaries on the Atlantic and Gulf coasts (Welsh, 1975;Anderson, 1985). Grass shrimp play a crucial role in estuarine ecosystems because they facilitate the trophic transfer of nutrients that are stored in detritus (Welsh, 1975). P. pugio is consumed by commercially and recreationally important species, including the Atlantic croaker Micropogonias undulatus (Linnaeus, 1766), striped bass Morone saxatilis (Walbaum, 1792) (see Clark et al., 2003), and white shrimp Litopenaeus setiferus (Linnaeus, 1767) (see Kneib & Knowlton, 1995). ...
... L. vannamei occurs naturally from the Gulf of California to northern Peru (Perez Farfante and Kensley 1997), but is imported for use in aquaculture because of its faster growth over native species (Sandifer et al. 1993). The grass shrimp, Palaemonetes pugio, serves an important role in the estuary as a detritivore by consuming and breaking down Spartina and aiding in trophic level energy transfer (Welsh 1975). They also serve as prey for many important commercial and recreational fishes and crustaceans, which use the marsh as nursery grounds (Welsh 1975). ...
... The grass shrimp, Palaemonetes pugio, serves an important role in the estuary as a detritivore by consuming and breaking down Spartina and aiding in trophic level energy transfer (Welsh 1975). They also serve as prey for many important commercial and recreational fishes and crustaceans, which use the marsh as nursery grounds (Welsh 1975). In the first phase of these experiments, an intramuscular bacterial challenge model with survival endpoint was developed and applied in both shrimp species to determine LDso values for V. parahaemolyticus. ...
Estuarine organisms routinely encounter fluctuations in dissolved oxygen, carbon dioxide, and pH, which can vary both seasonally and diurnally. Such environmental stresses as hypoxia can affect the immune response of invertebrates and vertebrates and have been linked to increased disease incidence. This research investigated the effects of hypoxia, hypercapnia, and low pH on disease susceptibility in both penaeid and palaemonid shrimp. Juvenile penaeid shrimp Litopenaeus vannamei and adult grass shrimp Palaemonetes pugio were challenged by intramuscular injection with a previously determined LD50 dose of a known pathogenic strain of Vibrio parahaemolyticus. Mortalities were monitored for shrimp held under normoxia (P(o2) = 150-155 torr, P(co2): = 0.23 torr, pH = 7.6-8.0 for L. vannamei, P(o2) = 150-155 torr, P(co2) = 0.23 torr, pH = 8.0-8.2 for P. pugio) and two levels of hypoxia. The penaeid shrimp were challenged under normocapnic hypoxia (P(o2) = 45 torr, P(co2) = 0.23 torr, pH = 7.8-8.1) and hypercapnic hypoxia ((P(o2) = 30 torr, P(co2) = 15.2 torr, pH = 6.8-7.0). Grass shrimp were challenged under two levels of hypercapnic hypoxia ((Po2) = 45 torr and 30 torr, P(co2) = 15.2 torr, pH = 6.7-7.0). Both the juvenile L. vannamei and the adult P. pugio held under hypercapnic hypoxia at 30 torr oxygen displayed significantly lower 48-hour survival (15.7 and 3.1%, respectively) than animals held in normoxic water (28.7 and 29.4%, respectively). There was no significant decrease in survival in L. vannamei under normocapnic hypoxia at 45 torr oxygen or in P. pugio under hypercapnic hypoxia at 45 torr oxygen. Total hemocyte count (THC/mL) significantly decreased in adult L. vannamei held under hypercapnic hypoxia when compared to normoxic controls. Oxygen level had a significant effect on total hemocyte density; whereas, time and the interaction of time and oxygen did not. The reduction in THC/mL may contribute to an increased rate of mortality in shrimp held under hypoxic conditions and challenged with V. parahaemolyticus. These results show that hypercapnic hypoxia decreases survival following bacterial challenge in both L. vannamei and P. pugio and decreases total hemocyte count in L. vannamei. These data provide direct evidence that naturally occurring variations in oxygen, CO2 and pH can place estuarine organisms at increased risk from opportunistic pathogens.
... Their annual productivity ranges from 9-16 g dry weight/m 2 /year, large enough for them to be ecologically significant [1]. The daggerblade shrimp, Palaemon pugio, can reduce the blockages of dead plant matter that form in wetland habitats, maintaining the ecosystem itself [2]. ...
Grass shrimp of the genus Palaemon (Crustacea, Decapoda, Palaemonidae) occur worldwide in freshwater and saline wetlands. Palaemon species are frequently misidentified, and the genus itself has been reorganized several times. To clarify the intrageneric phylogenetic relationships and analyze the regional genetic diversity, we sequenced fragments of the mitochondrial cytochrome c oxidase subunit I (COI) and the nuclear Histone H3 (H3) genes from specimens collected along the northern Gulf of Mexico, where several morphologically similar Palaemon species reside. The generated sequences were combined with publicly available Palaemon sequences for phylogenetic and haplotype analyses. Our analyses indicate that the rostral formula is an unreliable character for species identification, that the Mississippi River does not act as a genetic barrier between the eastern and western populations, and that freshwater species are likely not derived from the saltwater species in the region.
... Migratory shrimp are one group of animals that are important to healthy river function and are considered particularly vulnerable to reduced flow connectivity associated with water development (Bauer, 2013;Jarvis & Closs, 2019). Many shrimp species assist in transferring energy from detritus to higher trophic levels, such as fish (Crowl et al., 2001;Welsh, 1975), and some facilitate the transfer of energy from the marine environment to freshwater (Olivier, 2013). ...
Water development threatens rivers and their biodiversity. Amphidromous shrimp are particularly vulnerable as they require migration between freshwater and estuaries to complete their life cycle. The Fitzroy River is a large tropical intermittent river undergoing water development that is home to the amphidromous shrimp Macrobrachium spinipes (cherabin), yet little is known about its habitat use and flow‐ecology making it difficult to inform sustainable water‐take.
We investigated habitat associations, distributional patterns suggestive of amphidromy, and the influence of water availability by sampling main channel and floodplain pools along a 350‐km river length during 2 contrasting flow years. Applying a size‐specific abundance model, we estimated abundance per size class, site, and year. We then predicted abundance at the landscape scale with remotely sensed water to reveal the impact of water availability on the meta‐population.
Our model revealed that juveniles were in greatest abundance in downstream main channel pools, whereas adults were in greatest abundance in upstream floodplain pools. Abundance varied by year with lower numbers predicted in the low‐flow year. Longitudinal and habitat patterns remained when our pool‐level results were scaled to the landscape, and the positive relationship of abundance to wet‐season flow was strengthened. The predominance of smaller cherabin in the lower reaches of the river provides indirect support for an estuarine nursery and amphidromous life history; however, small individuals observed in landlocked pools, during late dry season suggests possible within‐river recruitment.
The importance of water development policies that protect wet‐season flow and passage along the Fitzroy River is supported by this work. These types of policies are likely to be important for this and other amphidromous shrimp species across Australia, Southeast Asia and further afield. Further research detailing the species life history and describing flow–recruitment relationships will be important contributions to understanding this important taxonomic group and refining policies for current and future water resource development.
... As opportunistic omnivores, Daggrblade Grass Shrimp move into intertidal marsh habitat to feed during high tide (Fleeger et al. 1999, Morgan 1980, retreat into subtidal marsh or refuges such as intertidal pools during low tide (Kneib and Wagner 1994), and tend to resist displacement from one intertidal creek to another (Allen et al. 2015). Often occurring in large numbers, this resident marsh species can affect production of the entire estuarine system by consuming meiofauna and grazing on epiphytic algae and detritus, then in turn serving as prey for fish and other crustaceans like Callinectes sapidus M.J. Rathbun (Blue Crab; Fleeger et al. 1999, Key et al. 2006, Kneib 1997, Welsh 1975. ...
With extensive and ongoing human development in coastal areas, effective shoreline-protection strategies against erosion and rising sea level that also provide natural ecosystem services will become increasingly important. Constructed living shoreline marshes can serve as successful management solutions when implemented correctly, but studies comparing these created estuarine habitats to their natural marsh counterparts are needed to assess their ecological functionality. We compared adult Palaemonetes pugio (Daggerblade Grass Shrimp) population demographics and diets from 13 pairs of living shoreline and natural marsh sites in the southwestern portion of the Chesapeake Bay. No significant differences were observed in demographics including abundance, weight, length, number of gravid females, and egg abundance and quality. Gut-content analysis detected significantly more terrestrial debris in shrimp from living shorelines, but the omnivorous dietary needs appeared met in all marsh sites. Overall, shrimp populations differed more among site pairs from different shorescape settings than between created and natural marshes from the same settings, suggesting that living shorelines are approaching ecosystem functionality similar to natural marsh habitats. However, the observed negative effect of agricultural land use on shrimp abundance and the discovery of microplastics in gut contents from all sites sampled indicate the need for further consideration of human impacts in both constructed and natural coastal habitats.
... The daggerblade grass shrimp Palaemon pugio (formerly Palaemonetes pugio, De Grave and Ashelby, 2013) is a crustacean that can be abundant along the Atlantic Coast of the United States (Welsh, 1975;Anderson, 1985). It inhabits submerged vegetation and hard bottom substrates such as oyster reefs near and around shallow marsh habitats (Heard, 1982). ...
The daggerblade grass shrimp Palaemon pugio can be a host for many types of parasites including the microphallid trematode Microphallus turgidus and the haplosporidian hyperparasite Urosporidium crescens. Parasitic infection by trematodes can influence grass shrimp behaviors and may alter habitat selection. We conducted monthly sampling to determine the abundance, density, intensity, and prevalence of M. turgidus and U. crescens at two sites near Savannah, Georgia. The goals of this study were to determine which microhabitat type P. pugio frequented more often, either sandy substrates or rocks with the invasive and habitat altering red alga Agarophyton vermiculophyllum, which was present seasonally, and whether trematode infection corresponded to microhabitat usage. Additionally, we aimed to determine whether temporal changes in parasitic infection correlated to abiotic factors. The results indicated grass shrimp were more likely to be located over sand substrate, even when A. vermiculophyllum was present. Furthermore, the surveys did not detect a relationship between shrimp microhabitat usage and trematode abundance, density, or intensity. All analyzed measures of trematode and hyperparasite infection differed significantly among months with some instances of intraseasonal variation. A negative relationship was detected between salinity and trematode prevalence and mean abundance, but not with temperature. No relationship was observed between salinity or temperature and hyperparasite prevalence or mean abundance. Through consistent monthly sampling of a heterogeneous habitat containing a habitat-altering invasive species, this study supports previous findings that salinity plays a role in M. turgidus abundance within P. pugio and demonstrates that A. vermiculophyllum does not appear to influence host microhabitat preferences, regardless of trematode infection. However, salinity alone cannot account for all observed parasite patterns; thus, it is likely that a combination of fluctuating abiotic conditions, unaccounted for aspects of habitat structure, and the presence of other host species determines grass shrimp risk of parasite infection.
... Palaemonetes spp. are important and abundant detritivores within salt marsh estuaries (Allen et al., 2015;Allen et al., 2007;Welsh, 1975) and are a common prey item for juvenile white shrimp (Hunter and Feller, 1987). Functional response experiments were conducted upon completion of the survival and growth experiment described in Section 2.2 and used the surviving control (n = 16) and tagged (n = 13) white shrimp as well as the same tank set up. ...
Connectivity among estuarine habitats can influence nekton vital rates, and studying these processes requires the ability to track individuals effectively. Passive integrated transponder (PIT) tags have been used to evaluate movement of juvenile fishes in estuaries, yet this technique remains untested for penaeid shrimp. We evaluated survival, growth, and feeding behavior of juvenile white shrimp (Litopenaeus setiferus), an ecologically and economically important penaeid species along the US Atlantic and Gulf coasts, implanted with 8-mm PIT tags. Daily survival and tag retention observations and weekly length and weight measurements were made of tagged individuals (n = 18) kept in individual seawater tanks for 28 days, and compared with similarly housed untagged (control) individuals (n = 18). After four weeks, tagged and control shrimp were offered varying densities of a common estuarine prey item, grass shrimp (Palaemonetes spp.), in feeding trials. Tagged white shrimp exhibited 100% tag retention and an estimated probability of survival after 28 d that was not significantly different from control shrimp (0.81 and 0.94, respectively). We found no evidence of a relationship between tagging treatment or initial shrimp size on the probability of survival. Tagged shrimp demonstrated growth at rates that were not significantly different from control shrimp, and tagged and control shrimp exhibited nearly identical feeding rates on grass shrimp (Palaemonetes spp.) prey. Our results suggest PIT tag technology represents an effective tool to study the movement and vital rates of juvenile white shrimp during their estuarine residence.
... Caloric values from published data were calculated to determine potential energy of the macroinvertebrate community (Welsh, 1975;Fredrickson & Reid, 1988;Foley, 2015). Only macroinvertebrates with published caloric values were used in the analysis. ...
The non-native aquatic fern giant salvinia, Salvinia molesta Mitchell (Salviniaceae), poses a risk to freshwater ecosystems through limiting light penetration, decreasing submerged aquatic vegetation (SAV) abundance, altering water quality, and potentially leading to changes in macroinvertebrate community structure. Here, we conducted repeated quarterly field surveys and measured light, nutrients, water quality, and aquatic macroinvertebrate community composition and energetic value to detect effects from giant salvinia invasion. Giant salvinia reduced dissolved oxygen, pH and light availability in the aquatic environment, and increased the concentration of orthophosphate and ammonium. Following initial colonization, macroinvertebrate communities in giant salvinia resembled SAV communities dominated by aquatic insects, however, richness and relative abundance in giant salvinia decreased over time, resulting in a community populated by few taxa, primarily crustaceans. Total macroinvertebrate energetic value in giant salvinia was significantly lower than SAV communities. Giant salvinia invasion changed habitat composition, triggered internal nutrient loading, and reduced macroinvertebrate abundance, diversity, and ecosystem productivity. Our findings demonstrate larger ecological impacts from giant salvinia than previously reported, including potential disruption to the transfer of energy between trophic levels.
... Giere, 2009 and references therein). Positive effects may include the deeper penetration of oxygen and organic matter into the sediment, which may result in an increase in meiofaunal abundance (Koller et al., 2006); the stimulation of bacterial growth (Lopez et al., 1977;Welsh, 1975), which are a main food source for meiofauna; and the provision of a refuge against predatory macrofauna (Thistle and Eckman, 1990). The majority of studies on the effects of biogenic structures deriving from macrofaunal activities are from intertidal or subtidal areas (Bell et al., 1978;Dittmann, 1996;Passarelli et al., 2012;Reise, 1981). ...
Feeding, burrowing, locomotion and death of larger organisms can significantly modify the appearance, texture and habitat conditions of the sediment surface. Such modifications create visible biogenic structures and associated microhabitats, which may have negative and/or positive effects on small-sized benthic communities. A series of dives with the submersible ALVIN was undertaken at the long-term monitoring Station M (4000 m, NE Pacific) in August 2006 to investigate, among other things, the influence of different biogenic structures on meiofauna and nematode assemblages. Five different biogenic structures were sampled; the tracks of two different species of sea urchins (Cystocrepis and Echinocrepis), one bioturbation mound, one decomposing kelp aggregate and one sponge. These were compared to a number of control samples taken away from the influence of the biogenic structures. Meiofauna ranged between 241 and 1277 ind per 10 cm 2 and was dominated by nematodes, with their contribution ranging from 74% to 89%. The comparison of the meiofauna communities from the biogenic structures and the control samples indicated differences between microhabitats for meiofaunal composition and nematode functional groups, which were due to differences between the microhabitats at the mound. The bioturbation mound and the control area hosted the highest number of nematode genera, though statistical analysis did not indicate significant differences. Beta diversity analysis revealed higher variability of meiofauna between than within different biogenic structures, suggesting habitat heterogeneity that may contribute substantially to the overall deep-sea richness. It may be concluded that among the studied biogenic structures, the bioturbation mound appears to be critical in shaping deep-sea meiobenthic communities.
... Black bars highlight omnivory indices that decreased upon substituting the revised diet matrix into WFS-HAB Ecopath, indicating groups becoming less omnivorous. Omnivory indices for all alternative versions of WFS-HAB Ecopath are detailed in Appendix Table C.2. known for strongly influencing benthic communities (e.g., March et al., 2002) and to be essential for the recycling of nutrients (e.g., Welsh, 1975). Additionally, Fujiwara et al. (2016) found significant associations between shrimp abundance and the catch rates of fish in some regions of the Gulf of Mexico. ...
Harmful algal blooms (HABs) are a growing concern in the West Florida Shelf (WFS) region. An Ecopath with Ecosim (EwE) model of the WFS explicitly simulating HABs was previously developed to illuminate the potential impacts of blooms of the dinoflagellate Karenia brevis (colloquially referred to as “red tides”) on the WFS ecosystem. However, the diet matrix of the Ecopath component of this EwE model (referred to as “WFS-HAB Ecopath”) was based largely on sparse, cursory information and not on local survey data. Here, we revise the diet matrix of the WFS-HAB Ecopath model using predictions of a robust statistical model that incorporates local survey data and employs the Dirichlet distribution and maximum likelihood estimation. The relative impacts of both the revised diet matrix and red tide mortality scenarios on model structure are explored by comparing four alternative WFS-HAB Ecopath models: (i) the base model; (ii) a model employing the revised diet matrix; (iii) a model with elevated red tide mortality; and (iv) a model with both the revised diet matrix and elevated red tide mortality. Incorporating the revised diet matrix into the WFS-HAB Ecopath model had a relatively large impact on ecosystem structure (i.e., trophic organization, mortality rates, trophic interaction strengths, and omnivory). Elevated red tide mortality had virtually no impact on ecosystem structure aside from altering the contribution of fishing, natural, and red tide mortalities to the total mortality of functional groups; however, elevated red tide mortality might have meaningful implications in dynamic simulations, which should be explored in future studies. Collectively, results showed that incorporating the revised diet matrix into WFS-HAB Ecopath, which revealed a number of new predator-prey linkages, led to a more complex and interconnected food web. Specifically, prey items were generally consumed by a broader variety of predators, which contrasts with the base WFS-HAB Ecopath model where many prey, particularly juvenile fishes, were subjected to exceedingly high predation mortality rates from specific predators. The incorporation of the revised diet matrix into the WFS-HAB Ecopath model discussed herein is a fundamental step towards increasing the realism of trophic interactions in the model, which is particularly important as these trophic interactions define starting conditions for dynamic simulations.
... Moreover, in all three species, we observed larger females than males, which is common within the Palaemonidae family (Bernard & Froneman, 2005;Rodriguez, 1981), as has previously been reported in P. pugio, P. paludosus, P. antennarium, P. kadiakensis and P. zariquieyi species (Anderson, 1985;Beck & Cowell, 1976;Hofer, Dalla, & Obermuller, 1980;Jalihal, Sankolli, & Shenoy, 1993;Nielsen & Reynolds, 1977;Sanz, 1988;Welsh, 1975). Similarly, the size difference among species, determined by the cephalothorax length and cephalothorax width, was remarkably larger in P. vulgaris; however, no significant influence on separation of species was identified, unlike the situation with propodus length, which was the best discriminating variable and also noticeably larger in P. vulgaris species. ...
Grass shrimps Palaemon mundusnovus, P. pugio and P. vulgaris sympatrically inhabit in the Laguna Madre, Mexico. They exhibit very close morphological similarity and overlap in their diagnostic characteristics, which has hindered certainty in their identification and has raised doubt regarding their taxonomic validity. In this work, we analyse intra‐ and interspecific morphometric and meristic variability through a multivariate analysis, and we determine the molecular variation using mitochondrial sequences of the 12S, 16S and COX1 genes to confirm the validity of the three taxa as having distinct lineages or to recognize a smaller number of species with phenotypic plasticity. Our results corroborate the taxonomic validity of the three species; however, there is intraspecific plasticity, interspecific overlap of characteristics and greater morphological and molecular similarity between the species P. mundusnovus and P. pugio, whereas P. vulgaris was better delimited. These species form a monophyletic group but the phylogenetic relationship obtained is discussed. Telson length was the primary variable in the principal components analysis, whereas the length of the propodus of the second pereiopod was the best discriminant. The range of variation reported in the characteristics linked to the rostrum is extended, and its influence on the separation of these species is recognized. The joint application of multivariate analysis from morphological variables and molecular tools is recommended to clarify the taxonomic status of species featuring close morphological similarity and sympatric distribution.
... P. pugio is widely distributed in the western Atlantic and Gulf of Mexico (Kaplan 1988), where they act as primary and secondary consumers, and aid in the breakdown of detritus . Many recreationally and commercially valuable fish and crab species use estuaries as nursery grounds and prey on P. pugio (Welsh 1975). There are four life stages during the life cycle of P. pugio: embryo, larvae, juvenile (postlarvae), and adult (Manyin and Rowe 2010). ...
Oil spills are a significant source of coastal pollution. Shoreline cleaners, used to remove oil from surfaces during spill response and remediation, may also act as toxins. Adult and larval grass shrimp, Palaemonetes pugio, were tested for lethal and sublethal impacts from two shoreline cleaners, Accell Clean SWA® and PES-51®, alone and in combination with crude oil using Chemically Enhanced Water Accommodated Fractions (CEWAFs). Median lethal toxicity values determined for the individual cleaners were similar. However, when tested in mixture with oil as CEWAFs, Accell Clean SWA resulted in greater hydrocarbon concentrations in the water column and greater toxicity than PES-51. Increased glutathione levels were observed for adult shrimp exposed to Accell Clean SWA, and glutathione was elevated in shrimp exposed to both CEWAFs. Larval shrimp development was delayed after exposure to both CEWAFs. These findings may have implications for managing and mitigating oil spills.
... At our field site, temperatures may differ substantially between the 2 collecting areas when the tide is out: in a previous study (Diederich & Pechenik 2013), Crepidula biomonitors at this site exceeded 40°C in the intertidal zone in the summer of 2011, while subtidal biomonitors reached a maximum of only 27°C during the same time period. Freshwater input at Bissel Cove is typically low, and salinity levels do not fall below 27 psu (Welsh 1975, McKinney et al. 2001, especially on the bay side of the cove where we sampled (C. Diederich pers. ...
The sedentary, suspension-feeding gastropods Crepidula fornicata and Crepipatella peruviana can be found in large numbers both subtidally and intertidally. Although intertidal animals often show reduced reproductive output compared with that of subtidal animals, we know little about how the reproductive output of marine gastropods is affected by exposure to intertidal stresses. We documented reproductive characteristics for intertidal and subtidal Crepidula fornicata in Rhode Island, USA (2012, 2013), and Crepipatella peruviana from Pelluco Beach, Chile (2010-2012). Females of both species brood encapsulated embryos for at least several weeks before releasing offspring, facilitating determinations of individual fecundity (embryos per egg mass). As expected from the environmental stresses experienced uniquely by intertidal individuals while emersed, including an inability to feed, intertidal females of C. peruviana had lower fecundities, producing significantly fewer egg capsules per brood; the mean number of eggs per capsule did not differ significantly by habitat. In marked contrast, the size-adjusted fecundity of Crepidula fornicata was significantly higher for intertidal females than for subtidal females; however, rather than brooding more egg capsules per individual or making larger egg capsules, intertidal females crowded each capsule with significantly more eggs. This study adds to previous work showing how exceptionally well-adapted C. fornicata is to intertidal life, and may help to explain why this species has been so unusually successful as an invasive among calyptraeid gastropods. Future studies will be required to identify the specific conditions that have provoked these adaptations in C. fornicata, and to understand the mechanisms through which this species achieves them.
... Grass shrimp (Palaemonetes pugio) are a key component of the estuarine ecosystem because they break down detritus, assimilate nutrients for other organisms, provide an indication of water quality, and serve as a staple in the diet of many ecologically and economically important organisms such as blue crabs and striped bass (Welsh, 1975). Because of their position in the food web, grass shrimp abundance can have profound effects on the status of both higher and lower trophic levels (Posey and Hines, 1991). ...
The grass shrimp (Palaemonetes pugio) is a staple prey species in the diet of many ecologically and economically important species such as blue crab and striped bass and is commonly infected with a trematode parasite, Microphallus turgidus. To complete its life cycle, M. turgidus must be consumed as a metacercaria by a bird or mammal definitive host. Previous research has found that infected grass shrimp behave more conspicuously than uninfected shrimp around predators, which include mummichogs (Fundulus heteroclitus). In addition, grass shrimp are more likely to avoid predation when they have access to coarse woody debris (CWD). Aquaria experiments revealed that uninfected shrimp significantly reduce the amount of time spent swimming in the presence of a fish predator, whereas infected shrimp did not exhibit this predation avoidance behavior. Uninfected shrimp also increased predator avoidance behavior ("backthrusts'') in the absence of CWD, whereas infected shrimp did not. These findings suggest that M. turgidus does not influence grass shrimp usage of CWD, but it alters shrimp swimming and backthrust behavior, thereby rendering infected shrimp more susceptible to predation. The implications of increased predation by a fish (nonhost or possible paratenic host) versus by a bird or mammal (definitive host) for parasite transmission are discussed.
... Due to their wide thermal tolerance, Atlantic stingrays may not have needed to take refuge from the cold; however, the rays could have been seeking out places of higher food abundance. Two prey items of the Atlantic stingray, grass shrimp (Welsh 1975) and blue crabs (Livingston 1976), move into deeper waters during the winter. These deeper or more topographically complex areas may be more difficult to sample using bottom trawls. ...
The Atlantic stingray Dasyatis sabina is found along the Atlantic and Gulf coasts of the United States. It consumes commercially important shrimp and crabs, and its diet overlaps with recreationally valuable red drum Sciaenops ocellatus and pompano Trachinotus spp. Despite the potential economic impact of this species, it is unclear whether the Atlantic stingray is present year-round or only seasonally in coastal habitats. The objective of this study was to assess the seasonal residency patterns of Atlantic stingrays in two creek systems in the Savannah River estuary. Forty stingrays were tracked using acoustic telemetry, and a seasonal residence index was calculated for each individual. Atlantic stingrays were present year-round in the Savannah River estuary, as 15 % (n = 6) of the tagged rays remained in the study areas throughout the year. This is the northernmost region where this species has been documented to be present all year. Of the 85 % (n = 34) of the rays that migrated during winter, 38 % (n = 13) of those were detected within the estuary less than 20 km away. Had trawls or mark-recapture been used instead, the few animals remaining in the creek systems and/or those that migrated may not have been collected. Acoustic telemetry is a more accurate means of studying the residency of fishes than periodic sampling that requires capture, and researchers should consider incorporating this technology in future studies about fish-environment interactions. Underestimating the presence of a species could result in miscalculation of its economic and ecological impact and, by extension, result in the implementation of ineffective or even detrimental management strategies.
... They can be collected from marshes using dip nets or can be found at some major chain pet stores or bait shops. Grass shrimp are easy to collect, handle, and maintain (Kunz et al., 2006) and have been used in many scientific studies (Welsh, 1975;Pung et al., 2002;Chaplin-Ebanks & Curran, 2007;Williamson et al., 2009;Partridge, 2010;Sherman & Curran, 2013, 2015Garcia et al., 2014;Brinton & Curran, 2015a). For example, Kunz et al. (2006) shrimp were observed to determine whether the behavior of the animal was altered by a parasite (Chaplin-Ebanks & Curran, 2005;Brinton, 2014;Brinton & Curran, 2015b), potentially increasing its susceptibility to predators (Brinton, 2014;Brinton & Curran, 2015b). ...
The process of exploration and the methods that scientists use to conduct research are fundamental to science education. In this activity, authentic scientific practices are used to develop hypotheses to explain the natural world. Students observe grass shrimp in aquaria and construct an ethogram, which is a compilation of the observable behaviors an animal exhibits. They then conduct an experiment, just as real scientists would, to determine how changes in the environment alter shrimp behavior. This activity is designed for a fourth-grade science class and allows students to experience the excitement of observing a live organism while learning about scientific inquiry, and also reinforces quantification and graphing skills. "Do You See What I See" covers Next Generation Science Standards and addresses the science and engineering practices of engaging in argument from evidence. © 2016 National Association of Biology Teachers. All rights reserved.
... During nutritional stress, reserves and their order of utilization varies according to the species, recent feeding history, diet composition, and length of fasting (Clifford & Brick 1983, Vinagre & Da Silva, 2002, Vinagre et al. 2007. Some authors refer that the crustaceans metabolism is primarily based on glycogen and fatty acids; in contrast, decreased levels of protein have been noted during fasting in several marine decapods (Welsh 1975, Barclay et al. 1983, Dall & Smith 1986, Wen et al. 2006, Comoglio et al. 2008, Zhang et al. 2009. ...
To study some early life history traits of
Lipophrys pholis
, 110 recruits (TL ≤ 30 mm) were collected in April and May 2013 during the low tide periods in four rocky beaches along the west (Cabo do Mundo, Peniche and Vale do Homem) and south (Olhos de Água) Portuguese coasts. Pelagic larval duration, size at settlement and age at coastal recruitment were back-calculated from the microstructure of otoliths. Pelagic larval duration estimated from micro-increment counts until the settlement marks ranged from 57 to 73 days and showed a latitudinal reduction trend from north to south. This variable seems to be related in 30% with the regional seawater temperatures probably through the direct effect on the somatic growth. Settlement sizes (~19 mm) did not show any regional differences suggesting that this is a more conservative character within species. The mean age at coastal recruitment varied between 69 and 93 days, but northern individuals were recruited at an older age. Back-calculated spawning, hatching and settlement dates appear to be unrelated to the lunar cycle for
L. pholis
.
... Brandt et al. [18] have highlighted the high rate of discovery for new species from the deep Southern Ocean, where up to 86% of isopod crustacean species were new to science, and argued that priority should be given to identifying the spatial distribution and abundance of key species in each trophic group across the region. Decapods are key species in the functioning of marine ecosystems, world-wide, as predators, scavengers, detritivores, and prey [19,20]. In the Ross Sea region, information on the distributions and population densities of shrimps is necessary for producing ecosystem models which will improve understanding of trophic interactions and inform environmental management [21]. ...
... Grass shrimp are predators, scavengers, and detritivores (see Vocabulary List), which means that they have multiple options for acquiring energy (Anderson 1985). Grass shrimp are crustaceans that break down huge volumes of marsh grass in estuaries (Welsh 1975) and are consumed by fish such as the Mummichog Fundulus heteroclitus and the Atlantic Croaker Micropogonias undulatus (Clark, Ruiz, and Hines 2003). Grass shrimp live in environments that are composed primarily of water, grass, and sediment. ...
Everyone needs strong observational skills to solve challenging problems and make informed decisions. However, many students expect to find exact answers to their questions by using the internet and do not understand the role of uncertainty, especially in decision making and scientific research. Humans and other animals choose among many options by using information about their environment. During this activity, students use their observational skills to analyze data from images of grass shrimp and a highly variable salt-marsh habitat as case studies for prioritizing different pieces of information. They gain an increased appreciation of natural variability and learn to build a consensus in a scenario that has no correct answer.
... These values are close to those reported here and suggest that grass shrimp are localized feeders on periphyton and/or detrital material. Grass shrimp are known detritus feeders (see Welsh 1975 and references therein) and the stable carbon isotope data reported here corroborate this. The d 13 C values for grass shrimp in the middle river and lower river/marsh transition zone reflect an increasing importance of estuarine/marine derived detrital material in their diets. ...
A multi-year research project was carried out on five rivers along Florida’s Springs Coast: the Weeki Wachee, Chassahowitzka, Homosassa, Crystal and Withlacoochee rivers. The general objective of the project was to describe quantitatively the physical, chemical and vegetative characteristics of each of the rivers. Physical and chemical data are reported for ten separate quarterly sampling events from August 1998 through January 2001. Vegetative data are reported for three summer sampling periods between 1998 and 2000.
... Many transient species have complex life cycles and are seasonal recruits, the majority of which are juvenile fish and decapod crustaceans that later migrate offshore or to other habitats where they become adults (Heck et al. 2008). In coastal waters of the northern Gulf of Mexico, examples of resident species include rainwater killifish (Lucania parva), blue crab (Callinectes sapidus), and grass shrimp (Palaemonetes pugio) (Jordan 2002;Thomas et al. 1990;Welsh 1975), and transient species include pinfish (Lagodon rhomboides), red drum (Sciaenops ocellatus) and penaeid shrimp species (Farfantepenaeus aztecus and Litopenaeus setiferus) (Minello and Zimmerman 1983;Nelson et al. 2013;Phillips et al. 1989;Rooker and Holt 1997). ...
Coastal lagoons are ubiquitous along coastlines worldwide. Here, we compare the abundance of epifauna, seagrass-associated macroinvertebrates, and small fish across a gradient of seagrass cover in shallow coastal lagoons of the northern Gulf of Mexico. Two of the lagoons had little or no seagrass cover (0–18.8 %), and four had high cover (83.8–97.5 %). All of the lagoons were partially covered with fringing marsh. We hypothesized that, due to habitat redundancy between seagrass beds and fringing marshes, seagrass-associated fish and macroinvertebrates would not be largely reduced despite the large differences in seagrass cover among the lagoons. Our results support this hypothesis. For most sampling dates, we did not find significant differences in fish and macroinvertebrate abundance among the lagoons and, when we did, several highly vegetated lagoons did not have larger abundances than sparsely vegetated lagoons. The extreme shallowness of the lagoons studied (<1 m) may also provide further protection from large predatory fishes in the absence of seagrasses. Our results also suggest that marsh detritus, by providing habitat for epifauna and helping maintain prey availability, may further temper reductions in seagrass-associated fishes and macroinvertebrates following seagrass decline. The results highlight the importance of marsh-bordered, shallow lagoons as habitat for small fish and macroinvertebrates regardless of seagrass cover. This study contributes to the characterization of habitat redundancy in coastal ecosystems and pinpoints the importance of considering all habitats in concert for the proper understanding and management of coastal ecosystems.
... The daggerblade grass shrimp Palaemonetes pugio is an abundant detritivore in estuarine ecosystems on the East and Gulf coasts of the US (Welsh, 1975). Predators of grass shrimp include the Atlantic croaker Micropogonias undulatus and the striped bass Morone saxatilis (Clark et al., 2003). ...
Description
The first comprehensive review of the use of invertebrates in toxicity testing and hazard evaluation. Discussions range from comprehensive evaluations of specific organisms to proposals for alternative methods.
Description
The second symposium on Aquatic Toxicology was held in Cleveland, Ohio, on 31 Oct.-1 Nov. 1977. This symposium was sponsored by the American Society for Testing and Materials through its Committee E35 on Pesticides. L. L. Marking, U.S. Fish and Wildlife Service, and R. A. Kimerle, Monsanto Co., presided as chairmen of the symposium and served as editors of this publication.
Climate warming has facilitated the expansion of black mangrove Avicennia germinans (hereafter ‘ Avicennia ’) into smooth cordgrass Spartina alterniflora (hereafter ‘ Spartina ’) salt marshes in southeastern Louisiana (USA). As macrophytes contribute to soil organic matter (SOM) and primary production, this transition could alter the basal energy pathways supporting salt marsh food webs. We used bulk-tissue and compound-specific stable isotope analyses (SIA) to determine if changes in dominant macrophytes alter basal energy pathways for 2 salt marsh residents: grass shrimp ( Palaemonetes spp.) and marsh periwinkle snails Littoraria irrorata . Specifically, we used Bayesian stable isotope mixing models to quantify the relative contribution of basal energy sources to SOM and resident food webs across a Spartina - Avicennia gradient in southeastern Louisiana. We found that sources of SOM changed in Avicennia -dominated habitat and that foraging strategy dictated trophic responses of salt marsh residents to Avicennia expansion. Marsh periwinkle snail basal energy sources shifted from Spartina to algae (phytoplankton and epiphytic macroalgae) reliance, while grass shrimp basal energy sources remained reliant on algal production, regardless of macrophyte dominance. Compound-specific SIA improved basal energy source distinctions and provided more constrained estimates of their contributions to resident food webs than bulk-tissue SIA. The importance of algal energy across the landscape warrants future investigations into the ability of Avicennia to support the diversity and abundance of algal energy sources present in Louisiana salt marshes. Understanding coastal wetland food web dynamics could help with planning and evaluating the most effective coastal restoration techniques (e.g. prioritizing salt marsh or mangrove habitat) in southeastern Louisiana.
Estuarine ecosystem balance typically relies on strong food web interconnectedness dependent on a relatively low number of resident taxa, presenting a potential ecological vulnerability to extreme ecosystem disturbances. Following the Deepwater Horizon (DwH) oil spill disaster of the northern Gulf of Mexico (USA), numerous ecotoxicological studies showed severe species-level impacts of oil exposure on estuarine fish and invertebrates, yet post-spill surveys found little evidence for severe impacts to coastal populations, communities, or food webs. The acknowledgement that several confounding factors may have limited researchers' abilities to detect negative ecosystem-level impacts following the DwH spill drives the need for direct testing of weathered oil exposure effects on estuarine residents with high trophic connectivity. Here, we describe an experiment that examined the influence of previous exposure to four weathered oil concentrations (control: 0.0 L oil m −2 ; low: 0.1 L oil m −2 ; moderate: 0.5-1 L oil m −2 ; high: 3.0 L oil m −2) on foraging rates of the ecologically important Gulf killifish (Fundulus grandis). Following exposure in oiled saltmarsh mesocosms, killifish were allowed to forage on grass shrimp (Palaeomonetes pugio) for up to 21 h. We found that previous exposure to the high oil treatment reduced killifish foraging rate by~37% on average, compared with no oil control treatment. Previous exposure to the moderate oil treatment showed highly variable foraging rate responses, while low exposure treatment was similar to unexposed responses. Declining foraging rate responses to previous high weathered oil exposure suggests potential oil spill influence on energy transfer between saltmarsh and off-marsh systems. Additionally, foraging rate variability at the moderate level highlights the large degree of intraspecific variability for this sublethal response and indicates this concentration represents a potential threshold of oil exposure influence on killifish foraging. We also found that consumption of gravid vs non-gravid shrimp was not independent of prior oil exposure concentration, as high oil exposure treatment killifish consumed~3× more gravid shrimp than expected. Our study findings highlight the sublethal effects of prior oil exposure on foraging abilities of ecologically valuable Gulf killifish at realistic oil exposure levels, suggesting that important trophic transfers of energy to off-marsh systems may have been impacted, at least in the short-term, by shoreline oiling at highly localized scales. This study provides support for further experimental testing of oil exposure effects on sublethal behavioral impacts of ecologically important estuarine species, due to the
The grass shrimp Palaemon pugio is an abundant and ecologically important species in estuarine habitats in the northwest Atlantic and is commonly used as an indicator species for environmental contamination, but little is known about its behavior. We examined aggression and dominance in P. pugio by using experimental arenas and groups of five shrimp that were observed an hour at a time for three days in the laboratory. Female shrimp showed high levels of initial aggression that quickly decreased over time, suggesting the formation of a dominance hierarchy. The dominance hierarchy between groups of females appeared linear, with shrimp at five distinct ranks in most replicates and higher-ranked individuals dominating lower-ranked ones. Dominance was significantly correlated with cheliped size but not body size, suggesting that larger chelipeds in female P. pugio may have evolved as a tool to establish dominance, perhaps to gain access to shelter in salt marshes, seagrass beds, or oyster reefs. Grass shrimp are preyed upon by a wide range of estuarine fish, and females are especially vulnerable; so securing access to shelter may provide a major selective advantage, with the dominance hierarchy evolving to save energy through a long-term reduction in fighting over resources.
In all arthropods the plesiomorphic (ancestral character state) kind of visual system commonly is considered to be the compound eye. Here we are able to show the excellently preserved internal structures of the compound eye of a 429 Mya old Silurian trilobite, Aulacopleura koninckii (Barrande, 1846). It shows the characteristic elements of a modern apposition eye, consisting of 8 (visible) receptor cells, a rhabdom, a thick lens, screening pigment (cells), and in contrast to a modern type, putatively just a very thin crystalline cone. Functionally the latter underlines the idea of a primarily calcitic character of the lens because of its high refractive properties. Perhaps the trilobite was translucent. We show that this Palaeozoic trilobite in principle was equipped with a fully modern type of visual system, a compound eye comparable to that of living bees, dragonflies and many diurnal crustaceans. It is an example of excellent preservation, and we hope that this manuscript will be a starting point for more research work on fossil evidence, and to develop a deeper understanding of the evolution of vision.
The seasonal occurrence and distribution of filamentous fungi on the aerial parts of salt marsh cordgrass, Spartina alterniflora, along a Rhode Island estuary were studied over a 26-mon period. Fungal fruiting bodies were observed on freshly collected standing plants and their frequency varied with the season. Frequency patterns were similar over the two growth-death cycles studied and indicate there may be a characteristic mycota associated with S. alterniflora. The Ascomycetes Buergenerula spartinae and Phaeosphaeria typharum were found to invade early during the growing season and the Deuteromycetes Alternaria alternata, Epicoccum nigrum, and Stagonospora sp. reached their highest frequencies at the time of seed production. Species of Leptosphaeria and Pleospora were found primarily on dead standing culms. A combination of both marine and terrestrial fungi can be observed on S. alterniflora, with the marine species occurring on the lower portion of standing plants. The number of observations of fungal species/plant was the greatest at the time of seed production, senescence, and death (September-January). The mycota at the three sampling stations, which differed in salinity, was similar and, in general, the fungi which occurred at the highest frequencies were found at all the sampling stations.
: Alewife Cove is a small (17 ha) receiving estuary for an 802-ha watershed system in southeast Connecticut. Over the past hundred years, urban development has destroyed or functionally separated 50% of the system's former fresh watercourses and inland wetlands and 40% and 75% respectively of its estuarine basins and marshes. The estuary, no longer buffered against sporadic runoff, undergoes drastic salinity changes following rainstorms, causing the mixing zone to oscillate over fully one-half of its total area. Beneath this zone, flocculent silt-clay sediments (80–85% water) cover the bottom in a layer exceeding 2 m in places. Groundwater intrusion causes salinity gradients in the sediments which can exceed those in the water column, and sediment pH can be reduced to 3.5. The infaunal community lacks spatial or temporal integrity. Small opportunists (Capitella, Streblospio) dominate, representing an early sere. Biomass is low. Epibenthic forms are limited. Macrodetrital (>0.5 mm) fragments, mostly freshwater and terrestrial material, outweigh living biomass by 101-103 and contribute to the conditions inhibiting macroinvertebrate processors large enough to handle them. This situation perpetuates organic loading to the area which sustains the stress. Depressed community structure beneath the mixing zone thus appears to result from a combination of factors which can be linked to the altered pattern of freshwater flow (flocculation, salinity stress, low pH and organic loadings). The proportionate influence of each of these factors, and also the extent to which other small estuaries are similarly affected await further study. These findings suggest that the maintenance of watershed storage capacity to buffer adequately against sporadic runoff is vital to maintaining healthy estuaries downstream from urbanized areas.
Organisms living in coastal waters, and especially estuaries, have long been known to have behavioral or physiological mechanisms that enable them to exist in water containing low amounts of oxygen. However, the respiratory consumption of oxygen that generates hypoxia is also responsible for producing significant amounts of carbon dioxide. An elevation of carbon dioxide pressure in water will cause a significant acidosis in most aquatic organisms. Thus, the combination of low oxygen and elevated carbon dioxide that occurs in estuaries represents a significant environmental challenge to organisms living in this habitat. Organisms may maintain oxygen uptake in declining oxygen conditions by using a respiratory pigment and/or by making adjustments in the convective how of water and blood past respiratory surfaces (i.e., increase cardiac output and ventilation rate). Severe hypoxia may result in an organism switching partially or completely to anaerobic biochemical pathways to sustain metabolic rate. There is also evidence to suggest that organisms lower their metabolism during hypoxic stress. Elevated water CO2 (hypercapnia) produces an acidosis in the tissues of organisms that breathe it. This acidosis may be wholly or partially compensated (i.e., mechanisms return pH to pre-exposure levels), or may be uncompensated. Some studies have examined the effects on organisms of exposure simultaneously to hypoxia and hypercapnia. This article reviews some of the specific adaptations and responses of organisms to low oxygen, to high carbon dioxide, and to the cooccurrence of low oxygen and high carbon dioxide.
More than 98% of the detrital material exported from the investigated Gulf Coast salt marsh is made up of amorphous aggregates. These detrital aggregates, averaging 25–50 µm in diameter, are produced by the benthic microflora of the marsh, rather than by microbial decomposition of the dominant vascular plant Juncus roemerianus as the prevailing view holds. Rising tides lift films of the aggregate material from the dense community of benthic algae that carpet the mud surface of the marsh. Ebbing tides transport the floating films into the tidal creeks where even mild water surface disturbances effect the dispersal of the films, which then sink as detrital aggregates into the water column. Ebb tides occurring during daylight hours carry larger quantities of detrital aggregates than tides that ebb during darkness. Detrital aggregate production follows an annual cycle with high production rates in late summer and low rates in the winter. Vascular plant tissue is decomposed beneath the layer of benthic algae and is retained in the marsh. Previously accepted concepts that stress the role of the decomposers in the production of detritus in tidal marshes are examined.
The caridean genus Palaemonetes occupies a wide variety of habitats from marine conditions to fresh-water. The marine and brackish species have an extended larval development, while fresh-water species have an abbreviated larval cycle. In this study reproductive aspects and type of larval development were compared between P. mexicanus and P hobbsi, both fresh-water species from northeast Mexico. Ovigerous females of each species were collected at the type locality and maintained in the laboratory at temperatures between 22 a 24°C. The larvae were reared individually at the same temperature conditions, and newly hatched nauplii of Artemia and fish flakes were provided as food. P. mexicanus and P. hobbsi have an abbreviated development consisting of 3 larval and 2 postlarval stages. The larval cycle including the postlarva had a duration of 12 days for P. hobbsi, while in P mexicanus lasted 16 days. The larval development of both species is almost identical. However, there are morphological features that can differentiate both species. Aspects of fecundity, biometry of females, eggs and larvae are discussed.
Crustaceans often undergo periods of starvation, due to natural food shortage or physiological constraints. During these periods, several metabolic and behavioral changes can occur. This study evaluates how the brown shrimp Crangon crangon (Linnaeus, 1758) responds to prolonged deprivation of food in two seasons of the year, and how this species mobilizes its energetic reserves. Shrimps caught in June (summer) and October (autumn) 2010 in the Minho estuary (north of Portugal) were placed in individual cages in experimental aquaria and kept in starvation until the last shrimp died or was sacrificed (six shrimp per aquarium every week). The energetic content, total lipids and total protein, and the oxygen consumption rate were compared between seasons, sacrificed and naturally dead shrimp, and considering the weeks of starvation. Summer shrimp proved to be better prepared to endure starvation than those caught in autumn: they survived 2.5 times longer, had a higher Fulton condition factor, higher energy, and higher lipid and protein content at the beginning of the experiments. The percentage of total body protein decreased significantly in the first week, stabilized in the following to decrease again abruptly in the fifth week. The percentage of total lipids only started to decrease after four weeks. This suggests that (1) C. crangon probably uses protein as a first energetic resource, followed by carbohydrates and eventually lipids, though to a much lesser extent; and (2) after 4 wk of starvation, a critical point is reached when structural components may be mobilized to satisfy maintenance costs.
The ability of a species to survive and reproduce in competition with its neighbours depends to a large extent on its relative ability to convert environmental energy to its own use, either as growth of the individual or as an energetic contribution to future generations in the form of gametes. In the presence of abundant food resources, many marine invertebrates make a maximum energetic gain by adoption of an ‘exploitative strategy’ of processing large quantities of food despite relatively low absorption efficiencies and high energetic costs which are strongly dependent on temperature. Energetic gain in such organisms is reflected in a high rate of growth (Pg) and reproduction (Pr). In the presence of limiting food resources in stress conditions of the upper shore, or under conditions of intense biotic competition on the lower shore, it is also possible for energy flow into growth and reproduction to be sustained by adoption of a ‘conservationist strategy’ of adjustment of the rate of consumption (C), absorption efficiency (A'/C) and respiratory losses (R) in response to temperature change. Under these conditions, conservation of metabolic energy expenditure plays a central role in the maintenance of an energetic gain from the environment, since increase of components of energy gain may be precluded by reduced food availability. The rates of oxygen consumption of such organisms are characteristically low and substantially independent of short-term increases in environmental temperature such as occur with the ebb and flow of the tide. A wide variety of patterns of metabolic response to temperature are thus to be anticipated according to spatial or temporal variations in environmental energy resources.
This study evaluates the effects of starvation on the physiological aspects of the southern king crab, Lithodes santolla. Adult males of this crab species were maintained in starving conditions for 12 days. Every 3 days (i.e. 0, 3, 6, 9 and 12), subgroups were taken to evaluate oxygen consumption, ammonia excretion, O:N atomic ratio and biochemical composition of the hepatopancreas. The hepatosomatic index (calculated individually as the percentage of henpatopancreas wet mass in relation to the total body wet weight) was lower at 12 day starving period, coincidentally with the minor amount of hepatopancreatic protein No significant differences in the relative biochemical composition (percentage of water, organic matter and ash) were detected. The lipid content was not significantly different during the experiment, nevertheless the higher value was detected at 3 days of starvation. Between the 3 and 9 days of fasting period ammonia excretion and hepatopancreatic protein were higher and the trypsin activity, lower. These results could indicate that protein catabolism was the most important in these periods. Besides, the lower values of O:N detected for all periods confirm this effect. On the ninth day of starvation oxygen consumption increased together with a high value of ammonia excretion probably due to an extra energy demand produced by starvation. We conclude that L. santolla in the experimental time-range study uses protein as the primary source of energy.
1. Aerobic, heterotrophic, marine bacteria have been found to participate actively in the decomposition of Spartina, both in the field and in the laboratory. Thirty-five per cent of 125 isolates obtained from sea water and marsh mud near Sapelo Island, Georgia, grew in sea water marsh grass extract medium more luxuriantly than in sea water Difco nutrient broth. 2. Assuming similar relationships to hold in nature and in the laboratory quantititive data provided an estimate that about eleven per cent of the annual crop of marsh grass may be rapidly converted to bacteria (dry weight basis). Microbial utilization of crude fiber takes place more slowly than decomposition and use of protein and soluble carbohydrate constituents. 3. Marsh mud extracts failed to serve as an enrichment medium for aerobic heterotrophic bacteria unless supplemented with organic materials, such as casein hydrolysate or grass extract. Supplements of dextrose, phosphate, or ammonium nitrate were generally ineffective. Numerous bacterial isolates from water and mud were able to grow well on extracts of Spartina in either natural or artificial sea water. 4. Bacterial isolates did not possess specific requirements for single amino acids, although growth in the presence of sources of amino nitrogen was generally better than on ammonium sulfate. Growth in the presence of multiple mixtures of pure amino acids or hydrolysed casein was better than growth on single amino acids. Among the combinations of pure amino acids studied, a mixture of alanine, aspartic acid, and glutamic acid yielded very good growth. 5. In the estuarine waters of the Georgia sea island region, where salinity varies greatly with changes in the seasons and tides, both euryhaline and stenohaline types of bacteria occur as natural adaptations to the fluctuating conditions of the environment.
The abundance and chemical composition of marsh grasses, sea lettuce and phytoplankton were determined in the Hempstead Bay estuary of the Town of Hempstead, Long Island, New York in 1967. The marshland comprises about 6,700 acres and the aquatic environment some 11,500 acres. Species of marsh grasses belonging in the genera Spartina and Distichlis produce an estimated 17,113 tons of dry matter per year in the Hempstead estuary, while the acquatic sea lettuce and phytoplankton produce 21,955 tons. The primary producers of organic matter in the Hempstead estuary are shown to form valuable quantities of protein, fat, carbohydrates and vitamins. Protein content of marsh grasses ranged from 9.6% to 14.9% of dry weight. Zostera yielded 14.6% and Ulva 20.8% protein in the dry matter. In the species of Ulva, Zostera, Spartina and Distichlis, ash content varied from 5.5% to 58.2%, fat ranged from 0.5% to 2.9% and carbohydrate yielded from 18.2% to 63.9%. Four B vitamins were present in adequate amounts to satisfy the requirements of grazing animals and microorganisms. Vitamin B12 occurred in relatively small amounts, (0.008 to 0.022 microgm/gm) in the flowering plants, but Ulva yielded 0.26 microgm of B12 per gram of dry matter. These nutrients and essential growth factors are available for direct assimilation by herbivores, and through microbial transformation to detritus they also supply indirectly valuable stores of particulate matter for filter feeders and other marine life.
1. Samples of young, and mature, leafy shoots, and weathered stems of the marsh grass Spartina alterniflora Loisel. were collected, from marsh regions along the coast of Georgia, for proximate analyses, and for the determinations of ten B vitamins and ten essential amino acids. 2. Proximate analysis of young Spartina yields values similar to those which have been published for Coastal Bermuda grass. The following data (per cent dry basis) represent the contents of growing shoots of Spartina: fat, 2.98; protein, 13.24; crude fibre, 29.75; ash, 12.83; and nitrogen-free extract, 40 20. The therms per pound are 1.68. 3. Weathered shoots, collected in August from growth of the preceding year, show loss of their leaves, and greatly lowered content of fat, protein, calcium and phosphorus. 4. The B vitamins, in general, appear to be present in adequate amounts for growth of guinea pigs, as is indicated by comparison of the vitamin level in the dried grass and in experimental rations The B vitamins are present in sufficient amounts for growth of heterotrophic microorganisms. 5. The ten essential amino acids, required for growth of the rat and man, constitute about 15 per cent of the protein of Spartina. Biological value of the protein is calculated to be deficient as a nitrogen supply for marine animals, and it is suggested that microbial conversion of the grass may act as a transformer to step up the potential value of the pool of protein in the sea.
Measurements of the abundance of major populations, their metabolism, and the seasonal patterns of total system metabolism throughout a year were used to develop energy-flow diagrams for a New England salt-marsh embayment. The annual ecological energy budget for the embayment indicates that consumption exceeds production, so that the system must depend on inputs of organic detritus from marsh grasses. Gross production ranged from almost zero in winter to about 5 g O"2 m^-^2 day^-^1 in summer. Respiration values were similar, but slightly higher, with the maximum difference observed in fall. Populations of shrimp and fish were largest in fall, with a much smaller peak in spring. Few animals were present in the embayment from May to July, but fall populations of shrimp ranged from 250 to 800 m^-^2 and fish averaged over 10 m^-^2. Birds were most abundant in winter and spring. In spite of high numbers, no evidence was found that the marsh embayment exported large amounts of shrimp or fish to the estuary. Production of aboveground emergent grasses on the marsh equaled 840 g m^-^2 for tall Spartina alterniflora, 432 g m^-^2 for short S. alterniflora, and 430 g m^-^2 for S. patens. These values are similar to those for New York marshes, but substantially lower than the southern marsh types. The efficiency of production of marsh grasses in the New England marsh was lower than reported for southern areas. A simulation model based on the laboratory and field metabolism and biomass measurements of parts of the embayment system was developed to predict diurnal patterns of dissolved oxygen in the marsh. The model was verified with field measurements of diurnal oxygen curves. The model indicated the importance of the timing of high tides in determining oxygen levels and was used to explore simulated additions of sewage BOD and increases in temperature.
In vivo chlorophyll, like many other organic molecules, possesses the ability to fluoresce. This fluorescence was measured continuously with a modified model III Turner fluorometer at sea. Reliable readings were obtained over the range of 0·04–2·0 mg chlorophyll a m−3 while on a 21-day cruise off the coast of Baja California. Since the relationship between fluorescence and chlorophyll was linear on all scales, it should be possible to continuously monitor chlorophyll from 0·04 to between 10 and 15 mg m−3, a range adequate for all open ocean studies.
Monitoring of the shrimp (Crangon vulgaris L.) catch off West Thurrock in the Thames estuary shows that they occur from September to February–April, but that within this period they are subject to great fluctuations. There is a substantial body of evidence that the lack of shrimps at any one time is associated with the low oxygen tension of the water.Experiments have been devised to determine (a) the level of oxygen depletion at which shrimps are asphyxiated, (b) the behaviour of shrimps as a consequence of oxygen depletion and (c) the effects of varying oxygen tensions on shrimp behaviour. A major effect of reducing oxygen tensions is for shrimps to alter their swimming pattern from the normal ‘background’ type to one in which stimulated swimming takes over and in which greater numbers of individuals of the population participate. During stimulated swimming the shrimps move upwards more vertically through the water body and this frequently involves ‘escape’ and ‘multiple escape’ reactions and passive sinking to the substrate. The ecological implications in a polluted estuary are that the higher the vertical height attained by the shrimps the longer the shrimps take to sink passively downwards. The longer they take to sink downwards the greater will be the distance covered horizontally when picked up by the tidal current and the faster the current the greater will be this distance. Within the context of the tidal Thames with its 14·5 km tidal excursion, the results have been computer-simulated and a model of shrimp migration suggested. The validity of computer simulation of a polluted estuary was tested against that of an unpolluted estuary, which latter can also be analysed mathematically.
Data are given on the kcal/g dry weight, percent ash, and kcal/ash-free g of dry weight for 1 marine diatom species, 70 macroscopic benthic algae, and 1 marine tracheophyte species. For 41 of these, the data have also been converted to kcal/g wet weight. Calorific values, though relatively homogeneous within genera, appear to be influenced by phyletic affinity, water purity, or depth of immersion, and such ecological properties as growth form, generation time, and relative susceptibility to herbivory. Seasonal factors, portion of the plant combusted and growth rate appear to have little effect. The food preferences of various invertebrate herbivores seem to have evolved more in response to an availability factor than to absolute food value.
The assimilation of detritus and its associated bacteria by three species of macrofauna which are abundant in eel grass beds
during the summer was investigated in a laboratory study. The amount of14CO2 respired per milligram of dry body weight by animals that fed on different types of labeled food was compared to determine
the relative amount of assimilation of a particular food. Animals were fed sterilized and unsterillized detritus labeled with14C to determine if they assimilated either the detritusper se or its associated bacteria as food.
All three species ingested and assimilated detritus. After 3 days of feeding, a small gastropod,Bittium varium, had ingested and assimilated more detritus per mg of body weight than either the grass shrimp,Palaemonetes pugio, or the polychaete,Glycera dibranchiata. BothPalaemonetes andBittium assimilated14C from labeled bacteria associated with the detritus as well as from the labeled detritus. All three species assimilated some14C from soluble sources.
A brief outline is given of the use of the Technicon Autoanalyzer® for the determination of phosphate, silicate and nitrate and the use of this equipment, together with continuous measurements of temperature and chlorophyll, to record the properties of surface water from a ship underway. The continuous recording of surface properties gives promise of a valuable new method for studying nutrient enrichment and biological production in space and time over large areas of the sea surface in eutrophic waters.
The effects of season, temperature, and salinity on the standard and active oxygen consumption of Palaemonetes vulgaris (Say) from Texas bays were determined by manometry. Chronic exposure to salinities from 3.5 to 32 p.p.t. produced no change in standard oxygen metabolism. Nor were circadian or tidally induced metabolic rhythms evident. Except for summer or warm-adapted shrimps measured at 10 °C, neither season nor prolonged exposure of shrimps to 10°, 20°, or 30 °C produced shifts in the standard or active oxygen rate – temperature curves obtained between 10° and 30 °C. Rather the effect of treatment or of season was reflected primarily by adaptation to temperature extremes. Thus, warm-adapted and summer shrimps lost equilibrium at 10 °C, whereas cold-acclimated shrimps showed metabolic depressions at high temperatures (35 °C). In general, Q10 values were low (< 2.0) for both standard and active oxygen rates. Also an adaptive adjustment in the availability of energy for activity appears to occur with warm and cold adaptation. Thus, although metabolic rates do not change markedly, when exposed to warm temperatures, warm-adapted grass shrimps swim faster per unit of active oxygen consumption than do intermediate or cold-acclimated shrimps. The reverse condition prevails for cold-acclimated shrimps.