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A confict of interest occurs when parasites manipulate the behavior of their host in contradictory ways to achieve diferent 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 fnal host elicit the opposite response. Since these parasites are altering the host’s behavior in opposing directions, a confict of interest would occur in co-infected shrimp. Natural selection should favor attempts to resolve this confict through avoidance, killing, or sabotage. In a feld survey of shrimp populations in four tidal creeks in the Cape Fear River, we found a signifcant negative association between the two parasites. Parasite abundance was negatively correlated in diferently 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 signifcantly diferent 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 diferently sized hosts, thus avoiding a confict and confrming the importance of testing assumptions in natural contexts. [ABSTRACT FROM AUTHOR]

Pharmaceuticals and personal care products (PPCPs) such as caffeine and sulfamethoxazole have been detected in the estuarine environment. The present study characterized effects of a maternal exposure of these compounds on the development of the daggerblade grass shrimp Palaemonetes pugio from embryo to juvenile life stage. Ovigerous females were exposed to either caffeine (20 mg/L), sulfamethoxazole (60 mg/L), or a mixture of both (20 mg/L caffeine and 60 mg/L sulfamethoxazole). Embryos were then removed from the females and the effects of the PPCPs on hatching, metamorphosis, juvenile growth, and overall mortality were determined. No significant effect was observed on gravid female survival after 5 d of exposure to caffeine, sulfamethoxazole, or the mixture; however, development of the embryos on the female shrimp was delayed in the mixture. Caffeine and sulfamethoxazole in the mixture significantly reduced embryo survival. There was a significant effect of caffeine, sulfamethoxazole, and the mixture on embryo hatching time. Exposure to sulfamethoxazole alone significantly delayed larval metamorphosis. Exposure to caffeine and sulfamethoxazole separately led to significantly smaller length of juvenile shrimp. Maternal exposure to caffeine and sulfamethoxazole, individually and in mixture, resulted in negative effects on P. pugio offspring survival and development; however, the concentrations tested in the present study were well above maximum detected field concentrations. These results may be incorporated into PPCP risk assessments to protect sensitive estuarine ecosystems more effectively. Environ Toxicol Chem 2014; 33:2120-2125. © 2014 SETAC [ABSTRACT FROM AUTHOR]

Abstract: Estuarine organisms often experience periods of cyclic hypoxia characterized by hypoxia in the early morning and normoxia in the afternoon. Here we examine the genomic responses of grass shrimp, Palaemonetes pugio, exposed to cyclic hypoxia in the laboratory. Differentially expressed genes in the hepatopancreas were determined in cyclic hypoxic vs. normoxic control groups after 1, 2, 5 and 10days of exposure to cyclic hypoxia using microarrays printed with 661 annotated transcripts obtained from multiple EST (expressed sequence tag) libraries. Sampling on each day was conducted at two different time series, one in the morning (representing low concentration of dissolved oxygen (DO), designated C-AM) and one in the afternoon (representing high DO concentration, designated C-PM). Distinct differences were observed between the number and identity of specific genes that were significantly down- or up-regulated in shrimp collected at the low DO and high DO points of the cyclic DO cycle. However, cluster analysis showed that the overall response patterns of high (C-PM) and low DO (C-AM) exposures were in the same cluster at 1, 2, and 5days. In contrast, the response patterns on different days were in different clusters. Day 1 was characterized by up-regulation of 17 unknown genes in the morning and a transient down-regulation of several hemocyanin genes, which returned to normoxic control levels in the afternoon. Days 2 and 5 showed significant down-regulation of 10 (C-AM) and 15 (C-PM) unknown genes, respectively. On day 10 the high DO samples showed a dramatic increase in the number of up-regulated genes, including several distinct hemocyanin genes, and this profile did not cluster with any of the other treatment groups. Vitellogenin, cathepsin L, cytochrome c oxidase subunit III, and fatty acid binding protein 10 were the signature down-regulated genes at day 10 (C-AM). According to GO annotation, the most abundant group of genes for both cyclic low (C-AM) and high (C-PM) DO exposure was associated with transport, defense response, and metabolic process. The differentially expressed genes were mapped to KEGG metabolic and regulatory pathways according to the gene distribution in Drosophila pathway database. Cyclic high (C-PM) DO affected a broad range of pathways compared to cyclic low (C-AM) DO. [Copyright &y& Elsevier]

With increased shoreline hardening and development, it is important to understand the ecological processes occurring in these and adjacent coastal habitats. A common species found associated with these hard-substrate habitats in Chesapeake Bay is the grass shrimp, Palaemonetes pugio. Caging experiments were conducted from June to August 2010 to examine the effects of shrimp on the recruitment and development of hard-substrate communities. Experiments were conducted at two low-salinity sites within Chesapeake Bay and one high-salinity site in an adjacent coastal bay in Virginia. The addition of grass shrimp reduced recruitment of polychaetes and scyphistomae of the sea nettle, Chrysaora quinquecirrha, and increased recruitment of encrusting bryozoans and the oyster, Crassostrea virginica. After 12 weeks, sea nettles at one low-salinity site, dominated predator-exclusion treatments. At the high-salinity site, oysters dominated when shrimp were present. Although it is unclear whether the results of short-term caging studies can be applied across larger temporal and spatial scales, the significant effects of grass shrimp on two important Chesapeake Bay species suggests that increases in hard-substrate habitat could have broader impacts within this and other systems. [ABSTRACT FROM AUTHOR]

Phenothrin is a synthetic pyrethroid used as a contact insecticide in mosquito control programs. This study compared the toxicity of phenothrin to adult, larval and embryonic grass shrimp (Palaemonetes pugio) and examined oxidative stress responses in adult and larval grass shrimp. The adult 24-h LC50 was 0.341 μg/L (95 % confidence intervals 0.282-0.412) and the 96-h LC50 was 0.161 μg/L (95 % CI 0.128-0.203 μg/L). The larval 24-h LC50 was 0.50 μg/L (95 % CI 0.441-0.568) and the 96-h LC50 was 0.154 μg/L (95 % CI 0.139-0.170 μg/L). In the presence of sediment, the 24-h LC50 was 6.30 μg/L (95 % CI 5.00-7.44 μg/L) for adults and 0.771 μg/L (95 % CI 0.630-0.944) for larvae. The sublethal biomarkers glutathione and lipid peroxidase (LPx) were examined after 96-h phenothrin exposure at five concentrations, and there were no statistically significant differences in these levels in adults or larvae compared to controls. There was a significant downward trend in larval LPx levels. This research confirms that phenothrin is highly toxic to grass shrimp and suggests that both adult and larval grass shrimp are appropriate life stages for risk assessments. [ABSTRACT FROM AUTHOR]

Transparency is an effective form of camouflage, but it must be present throughout the entire volume of an animal to succeed. Certain environmental stressors may cause physiological responses that increase internal light scattering, making tissue less transparent and more conspicuous to predators. We tested this in the transparent grass shrimp, Palaemonetes puglo, which is found in shallow estuaries where both salinity and temperature change rapidly because of tidal cycles, evaporation and runoff. Animals originally kept at a salinity of 15p.p.t. and a temperature of 20°C were placed into solutions with salinities of 0, 15, 25 or 30p.p.t. and temperatures of 13, 20 or 27°C for 12h (N=26 for each of 12 treatments). Under the control conditions of 15 p.p.t. at 20°C, the transparency of grass shrimp tails was 54±3% (mean ± s.e.). At higher salinities and at both higher and lower temperatures, transparency dropped significantly (P<0.001, two-way ANOVA), reaching 0.04±0.01% at 30 p.p.t. at 27°C. Confocal microscopy of P. pugio's tail suggested that the observed loss of transparency was due to the pooling of low refractive index hemolymph between the high index muscle fibers, creating many index boundaries that increased light scattering. Analysis of a year-long salinity and temperature record from a North Carolina estuary showed that changes of the order of those found in this study are relatively common, suggesting that P. puglo may undergo periods of reduced crypsis, potentially leading to increased predation. [ABSTRACT FROM AUTHOR]

Abstract: Palaemonetes pugio exposed to copper (9 or 26μg Cu2+/L) for a full life cycle were unable to produce viable embryos, precluding completion of the life cycle, despite no lethal effects on larval, juvenile, or adult life stages. Exposure to copper also resulted in a significant delay in larval development. When adults raised in copper were transferred to control seawater, they produced viable embryos, but larval output per clutch was reduced by 43% compared to clutches from females that had never been exposed to copper, suggesting reduced energetic allocation to reproduction. In acute exposures, adults exposed to copper for as little as three days were unable to produce viable embryos. Furthermore, exposure of control embryos to copper reduced hatching success by 74%. The reduction in hatching success and energetic allocation to reproduction are unlikely to be completely responsible for the lack of larval production observed in pre-spawning exposures to copper, suggesting that copper may also inhibit processes before or during spawning and fertilization. [Copyright &y& Elsevier]

In this study, the toxicity of endosulfan sulfate, the primary degradation product of the insecticide endosulfan, was determined in three life stages of the grass shrimp (Palaemonetes pugio). After 96 h exposure to endosulfan sulfate, the grass shrimp adult LC50 was 0.86 μ g/L (95% CI 0.56-1.31), the grass shrimp larvae LC50 was 1.64 μ g/L (95% CI 1.09-2.47) and the grass shrimp embryo LC50 was 45.85 μ g/L (95% CI 23.72-88.61 μ g/L). This was compared to the previously published grass shrimp 96-h LC50s for endosulfan. The toxicity of the two compounds was similar for the grass shrimp life stages with adults more sensitive than larvae and embryos. The presence of sediment in 24h endosulfan sulfate-exposures raised LC50s for both adult and larval grass shrimp but not significantly. The USEPA expected environmental concentrations (EEC) for total endosulfan and endosulfan sulfate and the calculations of risk quotients (RQ) based on the more sensitive adult grass shrimp 96-h LC50 clearly show that environmental concentrations equal to acute EECs would prove detrimental to grass shrimp or other similarly sensitive aquatic organisms. These results indicate that given the persistence and toxicity of endosulfan sulfate, future risk assessments should consider the toxicity potential of the parent compound as well as this degradation product. [ABSTRACT FROM AUTHOR]

Abstract: DNA microarrays have become an important tool to measure global gene expression changes and genetic pathways involved in response to environmental stressors and toxicants. In this study a cDNA microarray was designed and constructed from six libraries of expressed sequence tags generated in a previous study (Li, T., Brouwer, M., 2009. Bioinformatic analysis of expressed sequence tags from grass shrimp Palaemonetes pugio exposed to environmental stressors. Comp. Biochem. Physiol. Part D Genomics Proteomics. doi:10.1016/j.cbd.2009.03.001). The microarrays were used to examine differentially expressed genes in hypoxic vs. normoxic groups at 6 (H6), 12 (H12), 24 (H24), 48 (H48), 120 (H120), and 240 (H240) h exposure to chronic hypoxia (dissolved oxygen (DO) 1.5 mg/L). The initial response to hypoxia was an up-regulation of 29 genes. Only 6 h later, a dramatic down-regulation of 47 genes was observed. There was another reversal with 19 genes being up-regulated and none down-regulated at 24 h. After 2 and 5 days 34 and 22 genes were up-regulated, respectively, and 24 genes were down-regulated and 6 up-regulated by day 10. Cluster analysis confirmed two response patterns, one composed of an up-regulated dominated cluster, including H6, H24, and H120, the other composed of a down-regulated dominated cluster, including H12, H48, and H240. Venn diagrams of differentially expressed genes showed there was no gene up- or down-regulated common to all six groups. Hemocyanin transcription was up-regulated after 24, 48, and 120 h, but down-regulated after 12 h. Some genes appeared unique for specific time points. Phosphoenolpyruvate carboxykinase was up-regulated in the H120 and H240 groups. Cytochrome c oxidase subunit I and C-type lectin were uniquely up-regulated in H12, whereas vitellogenin and trachealess were uniquely down-regulated in H48. GOstats and org.Dm.eg.db packages from R were used to assign GO terms to significantly expressed genes. A total of 291, 129, and 219 genes were assigned to biological process, cellular components, and molecular function, respectively. The most abundant groups of genes were associated with transport, metabolic process, defense response, and proteolysis. Pathways were analyzed using Drosophila metabolic pathways in the KEGG database. Oxidative phosphorylation/Citrate cycle and Ribosome were the most abundant categories for chronic hypoxic exposure. Of 19 selected genes that showed differential expression on the microarrays, 17 showed similar up- or down-regulated patterns in both microarray and qPCR. In conclusion, the custom cDNA microarray is a valid and useful tool to investigate the changes in gene expression of grass shrimp during chronic hypoxia exposure. Some genes, such as those coding for hemocyanin, ATP synthase, phosphoenolpyruvate carboxykinase, vitellogenin, trachealess, cytochrome c oxidase subunit I, lysosomal thiol reductase, and C-type lectin, could be used as molecular indicators of chronic hypoxia at specific time points. However, changes of these significant genes were too dynamic to serve as generic biomarkers of hypoxia stress in grass shrimp for the whole duration of the chronic hypoxia exposure. [Copyright &y& Elsevier]

Abstract: Six libraries of expressed sequence tags (ESTs) were constructed by suppression subtractive hybridization (SSH) from the grass shrimp, Palaemonetes pugio, exposed to environmental stress: severe (Dissolved Oxygen (DO) 1.5 mg/L) and moderate (DO 2.5 mg/L) chronic hypoxia, cyclic hypoxia (1.5→7 mg/L), contaminant-induced stress (pyrene and copper), and biological stress (molt). A total of 1553 ESTs were clustered and assembled using Paracel Transcript Assembler software. The resulting 661 potential transcripts included 181 contigs and 480 singlets. The assembled sequences were annotated by BLAST searches against the public protein database. Gene Ontology (GO) terms for each sequence were provided using GOblet software. A total of 312 assembled transcripts matched a protein with an E-value less than 1E-5. The most similar matches (18%) were from different crustaceans. Large proportions of sequences had no significant BLAST hits (53%) or GO terms (64%). GO analysis by libraries showed several genes that were present in only one library suggesting that their expression may be stressor specific. Up-regulation of muscle proteins and GSH-peroxidase appeared specific for chronic (1.5 mg/L) and cyclic hypoxia exposures, respectively. Several genes involved in sulfur redox and (homo)cysteine metabolism were all down-regulated in response to cyclic hypoxia. Up-regulation of cytochrome c oxidase subunit I and down-regulation of vitellogenin was a common response to chronic (1.5 mg/L and 2.5 mg/L) and cyclic DO exposures. The molting process was accompanied by changes in expression of many genes not found in the hypoxia/copper/pyrene libraries. The cDNA clones and sequence information can be used for future functional analysis and for construction of microarrays for monitoring of environmental stressors in coastal waters using wild or caged grass shrimp. [Copyright &y& Elsevier]

Abstract: Yellow-head virus (YHV) is a major pathogen in penaeid shrimps. We surveyed 13 crustacean species in eight families from two orders that are commonly found in the Mississippi coastal area and freshwater environments as potential reservoir or carrier hosts of YHV. Using semi-nested polymerase chain reaction (PCR) on relatively small sample sizes, we did not detect any natural infection. However, when the daggerblade grass shrimp, Palaemonetes pugio, and the blue crab, Callinectes sapidus, were exposed to YHV by injection and per os, YHV was detected in the tissue of P. pugio and in the hemolymph of C. sapidus when tested by semi-nested reverse transcription PCR (RT-PCR) and real time quantitative reverse transcription PCR (qRT-PCR). YHV replicated in P. pugio, causing 8% mortality (9/112) after injection, with the viral titer reaching a peak at 14days post-inoculation (dpi) and remaining detectable at 36dpi. The number of infected animals and viral load, however, were relatively low but the virus still remained infectious to penaeids when administered by feeding. When YHV was injected into P. pugio, in situ hybridization detected a positive response to it at 7dpi in connective tissue of hepatopancreas, muscle, and midgut. Viral RNA in injected C. sapidus remained at a low level for 3days, and it was not detected from 7dpi onwards. In fed C. sapidus, the viral RNA reached a peak at 3dpi and still detectable at 7dpi, but it became undetectable at 14 and 21dpi. These data suggest that P. pugio under some conditions could act as a reservoir host for YHV but that the blue crab could serve as a poor, short term carrier host only. [Copyright &y& Elsevier]

This study investigated the lethal and sublethal effects of the pyrethroid insecticide bifenthrin on adult and larval grass shrimp, Palaemonetes pugio, and adult sheepshead minnows, Cyprinodon variegatus. The effects were determined by conducting 96-h aqueous static renewal tests and 24-h static tests with sediment. Oxidative stress biomarkers, lipid peroxidation, glutathione, and catalase were also assessed. The 96-h aqueous LC50 value for adult shrimp was 0.020 μ g/L (95% CI: 0.015-0.025 μ g/L) and for larval shrimp was 0.013 μ g/L (95% CI: 0.011-0.016 μ g/L). The 96-h aqueous LC50 for adult sheepshead minnow was 19.806 μ g/L (95% CI: 11.886-47.250 μ g/L). The 24-h sediment LC50 for adult shrimp was 0.339 μ g/L (95% CI: 0.291-0.381 μ g/L) and for larval shrimp was 0.210 μ g/L (95% CI: 0.096-0.393 μ g/L). The oxidative stress assays showed some increasing trends toward physiological stress with increased bifenthrin concentrations but they were largely inconclusive. Given the sensitivity of grass shrimp to this compound in laboratory bioassays, additional work will be needed to determine if these exposure levels are environmentally relevant. [ABSTRACT FROM AUTHOR]

This study examined the toxicity of two pesticides (carbaryl and diquat dibromide) and one polycyclic aromatic hydrocarbon (fluoranthene), both singly and in mixture, to grass shrimp larvae (Palaemonetes pugio). These three chemicals are all present in coastal environments and can easily enter estuarine ecosystems. Fluoranthene was the most toxic chemical with a 96-h LC50 value of 32.45 μ g/L, followed by carbaryl (43.02 μ g/L) and diquat dibromide (1624 μ g/L). In the chemical mixture tests, the binary carbaryl/diquat dibromide mixture and the ternary carbaryl/diquat dibromide/fluoranthene mixture had additive results. [ABSTRACT FROM AUTHOR]

Abstract: Piperonyl butoxide (PBO) is a commonly used synergist in many pyrethroid formulations due to its ability to interfere with cytochrome P450 (CYP) monooxygenases. Because PBO can co-occur in the estuarine environment with polycyclic aromatic hydrocarbons (PAHs), a class of compounds metabolized by CYP isozymes, the overall objective of this study was to investigate the influence of PBO on the bioconcentration and photoinduced toxicity of two common PAH contaminants, fluoranthene (FLU) and benzo[a]pyrene (BaP), on the larvae of the grass shrimp (Palaemonetes pugio). PBO alone was not particularly toxic to grass shrimp larvae. In dark exposures and under simulated sunlight (UV-A=211.0±7.0μW/cm2, UV-B=9.8±2.4μW/cm2), 96-h LC50 values were similar (814.4 and 888.6μg/L, respectively), suggesting that PBO toxicity is not enhanced in the presence of sunlight. The presence of sublethal concentrations of PBO in single PAH toxicity tests increased the bioconcentration of the two tested PAHs, and these increases were greatest at the lowest tested PAH concentrations. Mean bioconcentration factors (BCF) at the three lowest FLU and BaP treatments increased 14.3- and 7.1-fold, respectively, in the low PBO (127μg/L) exposure compared to that of the no PBO exposure. Under simulated sunlight, PBO exposure also increased the photoinduced toxicity of the two tested PAHs, and this increase occurred in a PBO concentration-dependent fashion. For FLU, 96-h LC50 values decreased from 2.35μg/L in the absence of PBO to 0.76μg/L in the high PBO (256μg/L) exposure. For BaP, 96-h LC50 values similarly decreased from 1.02μg/L in the absence of PBO to 0.30μg/L in the high PBO exposure. The presence of PBO also influenced the PAH tissue residue–response relationship, but in different ways for FLU and BaP. For FLU, slopes of the tissue residue–response relationship decreased in the presence of PBO, and for BaP, there was a trend towards increased slopes in the presence of PBO. These results demonstrate that sublethal levels of PBO increase the bioconcentration and photoinduced toxicity of certain PAH in grass shrimp larvae, and underscore the need to consider the potential for PBO to synergize the toxicity of co-occurring environmental contaminants in future risk assessments. [Copyright &y& Elsevier]

This study examined the toxicity of three pesticides, singly and in mixture, to grass shrimp (Palaemonetes pugio) larvae. The pesticides included atrazine, an herbicide used on turf grass and field crops; fipronil, a persistent insecticide used against termites and fire ants; and imidacloprid, a systemic insecticide used in agricultural and home products. Fipronil was the most toxic to shrimp larvae with a 96-h LC50 of 0.68μg/L (95% CI 0.57–0.79μg/L). Shrimp larvae were less sensitive to imidacloprid with a 96-h LC50 of 308.8μg/L (95% CI 273.6–348.6μg/L). Atrazine was non-toxic to shrimp larvae at concentrations up to 10,000μg/L. In mixtures, fipronil plus atrazine and imidacloprid plus atrazine had no change in toxicity compared to fipronil and imidacloprid tested singly. Similarly, a fipronil/imidacloprid mixture did not show greater than additive toxicity. However, when atrazine was added to the fipronil/imidacloprid mix, greater than additive toxicity occurred. [Copyright &y& Elsevier]

Abstract: Hypoxia-inducible factor 1α (HIF-1α) is a key transcription factor that controls a variety of cellular and systemic homeostatic responses to hypoxic stress. Expression and function of HIF-1α have not been studied in crustaceans, which experience wide fluctuations of oxygen tensions in their aquatic environment. Here we show that an HIF-1α homolog, gsHIF, is present in the hypoxia-tolerant grass shrimp Palaemonetes pugio. Using RT-PCR and 3′ and 5′RACE, we cloned a full-length gsHIF cDNA (3822 bp) with an open reading frame encoding a 1057 amino acid protein. Similar to vertebrate HIF-1α, gsHIF has one basic helix–loop–helix (bHLH) domain, two PAS domains, an oxygen-dependent degradation domain (ODD) with two proline hydroxylation motifs, and a C-terminal transactivation domain (C-TAD) with an asparagine hydroxylation motif. In addition to these conserved sequences, gsHIF has a unique 230 amino acid sequence (aa 790–1020) not found in any vertebrate HIF proteins. Phylogenetic analysis indicates that grass shrimp and vertebrate HIFs belong to distinct clades within the HIF protein family. Expression analysis shows that gsHIF is constitutively expressed under normoxic (7.5 ppm DO), moderate (2.5 ppm DO) and severe (1.5 ppm DO) hypoxic conditions. In addition to gsHIF, we cloned a fragment of a second bHLH-PAS transcription factor from the grass shrimp, which had one bHLH and two PAS domains, and an overall 68% amino acid sequence homology with Apis mellifera trachealess protein. [Copyright &y& Elsevier]

The objective of this study was to determine the potential for dietary transfer of sediment-associated fluoranthene from tubificid oligochaetes (Monopylephorus rubroniveus) to grass shrimp (Palaemonetes pugio). Grass shrimp, either in the presence or absence of sublethal waterborne concentrations of the metabolic inhibitor, piperonyl butoxide (PBO), were fed fluoranthene-dosed oligochaetes for 5-days. All grass shrimp bioaccumulated fluoranthene; however, bioaccumulation was 3X higher in the presence of PBO. Trophic transfer coefficients (TTCs) were 0. 02 and 0. 01 in the presence and absence of PBO, respectively. Following the 5-day accumulation period, shrimp in both treatments were allowed to depurate for 3 days. Depuration rates were significantly higher in PBO-exposed shrimp. These results demonstrated that sediment-associated fluoranthene can be transferred through the diet from oligochaetes to grass shrimp, and the presence of PBO enhanced fluoranthene bioaccumulation. However, the comparatively low TTCs suggest that biomagnification of fluoranthene in estuarine food webs is low. [Copyright &y& Elsevier]

Estuaries of the southeastern United States not only serve an important nursery function but also are common repositories of polycyclic aromatic hydrocarbons (PAHs) derived from upland activities. Thus, these habitats may be at risk for PAH phototoxicity. To better characterize this risk, a daily survey of ultraviolet-A (UV-A; 320-400 nm) irradiance was performed at Leadenwah Creek (Wadmalaw Island, SC, USA) on June 27 and August 1, 2003. In addition, laboratory assays were completed using two light exposure regimes: One that was typical of historical phototoxicity assessments (continuous light [C-UV]), and a more environmentally realistic regime (ER-UV). On both survey days, irradiance at a depth of 10 cm exhibited a pattern generally similar to that observed at the surface, whereas irradiance at the bottom of the creek was a function of both tidal height and time of day. Total UV-A dose at a 10-cm depth on June 27 and August 1, 2003 was 4.37 and 4.78 J/cm2, respectively. Attenuation coefficients on both days varied as a function of tidal height. In the laboratory, larval grass shrimp (Palaemonetes pugio) exposed to an ER-UV regime for these habitats (photoperiod, 12: 12-h light: dark; total daily UV-A dose, 4.40 J/cm2) exhibited a 2.5-fold decrease in toxicity compared with those exposed to the C-UV regime (photoperiod, 24: 0-h light: dark; total daily UV dose, 1.50 J/cm2), despite a threefold higher UV dose in the ER-UV regime. The lower potency under the ER-UV regime likely is attributable to the presence of a 12-h dark period allowing for recovery. The consequences of these results are discussed in the context of habitat-specific UV-A dose and its relevance to future laboratory assessments of PAH phototoxicity. [ABSTRACT FROM AUTHOR]

Abstract: Toxicity of the pyrethroid insecticide permethrin was assessed using three life stages of the estuarine grass shrimp, Palaemonetes pugio. Adult and larval shrimp were tested with and without sediment. An aqueous embryo test was also conducted. Cellular stress biomarkers, glutathione, and lipid peroxidation, were assessed. Larval shrimp were the most sensitive life stage with a 96-h lethal concentration (LC50) value of 0.05μg/L, compared to 0.25μg/L for adults, and 6.4μg/L for embryos. The presence of sediment significantly decreased toxicity of permethrin to both adult and larval shrimp. Permethrin exposure increased time to hatch in embryos and decreased swimming behavior of larvae. Lipid peroxidation levels were significantly decreased in the adult shrimp, but increased in larval shrimp exposed to permethrin. Low levels of permethrin may negatively affect grass shrimp health and survival. Permethrin use in the coastal zone should be carefully managed to avoid adverse impacts on nontarget estuarine organisms. [Copyright &y& Elsevier]

Abstract: Three life stages of larval grass shrimp were tested to determine whether acetylcholinesterase (AChE) activity expressed as 24-h sublethal effect endpoints (EC20 and EC50) could be used to predict 96-h mortality (lowest observable effect concentration (LOEC) and LC50) for shrimp exposed to three organophosphate insecticides. With regard to mortality, newly hatched larvae and 18-day-old larvae were the most sensitive in the malathion and azinphosmethyl exposures. In the chlorpyrifos exposures, newly hatched larvae and postlarvae were the most sensitive life stages. Results of the 24-h AChE inhibition tests showed that newly hatched larvae were generally more sensitive in the three organophosphate exposures. A regression analysis of the EC50''s and LC50''s yielded the strongest correlation with (correlation coefficient=0.994 and 95% confidence intervals 0.969–0.999). The LOEC/EC20 relationship yielded . For these grass shrimp life stages and pesticides, sublethal effect endpoints could be used as a predictor of 96-h mortality. [Copyright &y& Elsevier]

Abstract: Previous studies have shown that metal partitioned to a subcellular compartment containing trophically available metal (TAM) is readily available to predators and may be enhanced by increased binding of metal to heat-stable proteins (HSP – e.g., metallothioneins). The aim of the current investigation was to determine the influence of TAM on the trophic transfer of Cd along an experimental, three-level food chain: Artemia franciscana (brine shrimp)→Palaemonetes pugio (grass shrimp)→Fundulus heteroclitus (mummichog). P. pugio were fed for 7 days on A. franciscana exposed to Cd in solution (including 109Cd as radiotracer) and subjected to subcellular fractionation or fed to F. heteroclitus. An HSP-driven increase in the percentage of Cd associated with TAM (TAM-Cd%) in A. franciscana exposed to 1 μM Cd resulted in a bioenhancement (i.e., a greater than linear increase with respect to A. franciscana exposure) of Cd trophic transfer to P. pugio. Increased dietary Cd exposure did not affect TAM-Cd% in P. pugio nor trophic transfer to F. heteroclitus. [Copyright &y& Elsevier]

Abstract: During embryogenesis in grass shrimp the capacity to scavenge oxyradicals increased as measured by the Total Oxyradical Scavenging Capacity (TOSC) assay. The increase in TOSC during embryogenesis was associated with increasing concentrations of a number of antioxidants, including coenzyme Q (ubiquinone), α-tocopherol and reduced glutathione. Glutathione concentrations ranged from 0.004 to 0.005 nmol/embryo in early embryo stages and reached concentrations between 0.16 to 0.23 nmol/embryo in late embryo stages. Ascorbate remained essentially constant (0.16–0.20 nmol/embryo) throughout embryogenesis and may provide the preponderance of TOSC during early embryo development. Carotenoids were associated with yolk lipovitellin and these antioxidants decreased as yolk was absorbed during embryogenesis. Astaxanthin and β-carotene were identified in embryos with astaxanthin always the principal carotenoid. In early embryo stages there are maternally derived antioxidants but as embryogenesis proceeds there is an assembly of a complex antioxidant system by newly formed cells and tissues. [Copyright &y& Elsevier]

The primary objective of this research was to determine if the genotype of the enzymes glucose phosphate isomerase (Gpi), phosphoglucomutase (Pgm), or mannose phosphate isomerase (Mpi) are factors affecting survival during acute endosulfan, fluoranthene, and chromium(VI) exposures. Palaemonetes pugio were exposed in the laboratory to 6.3μg/L endosulfan, 100mg/L chromium(VI), or 0.6mg/L fluoranthene. Dead shrimp were removed at approximately 15–30min intervals and the individual''s genotypes for the Gpi, Mpi, and Pgm enzymes were determined. These data were used to establish whether allozyme genotype was related to tolerance as analyzed with non-parametric methods (i.e. development of survival curves using the Kaplan–Meier method of estimation) and parametric methods (i.e. proportional hazards models). Since the sex and/or size of the organism was expected to affect tolerance, these variables were accounted for in the proportional hazards models. Results indicated individuals that were heterozygous (MF) for the Gpi allozyme survived longer and had less overall mortality than the homozygous MM genotype when exposed to chromium(VI) and to fluoranthene. No allozyme genotypes were related to tolerance during the endosulfan exposure when sex was included as a covariate in the analysis. These results support the hypothesis that there is a genetic basis for tolerance in P. pugio during acute exposures to chromium(VI) and to fluoranthene. Although a relationship between Gpi genotype and contaminant tolerance has been identified in previous studies, no such relationship has been documented in P. pugio or with chromium(VI) as the contaminant. [Copyright &y& Elsevier]

The effect of salinity on the photoinduced toxicity of waterborne fluoranthene to larvae of the grass shrimp (Palaemonetes pugio) and tubificid oligochaete worms (Monopylephorus rubroniveus) was studied in a laboratory system under simulated sunlight. In the grass shrimp toxicity tests, five concentrations of fluoranthene (0, 3.6, 7.3, 13.8, and 29.0 µg/L) and four salinities (6.9, 14.5, 21.2, and 28.6‰) were achieved. In the oligochaete toxicity tests, five concentrations of fluoranthene (0, 0.8, 1.4, 3.3, and 7.7 µg/L) and four salinities (7.1, 13.3, 20.5, and 27.6‰) were achieved. Salinity had no effect on either the photoinduced toxicity or the bioaccumulation of fluoranthene in the grass shrimp. However, the highest level of salinity decreased the median lethal time for the oligochaete. Bioaccumulation of fluoranthene was inversely related to salinity for the oligochaete. Additional experiments demonstrated an inverse relationship between salinity and short-term osmotic weight change in the oligochaete. Weight of the grass shrimp larvae was not affected by salinity. These findings show that salinity can influence the toxicity and bioaccumulation of fluoranthene in some estuarine organisms. The influence of salinity on these populations may be related to physiological responses associated with internal osmotic volume changes. Thus, salinity needs to be taken into account when assessing the risk of photoactivated polycyclic aromatic hydrocarbon (PAH) to at least some estuarine species. [ABSTRACT FROM AUTHOR]

Chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) is the second most widely used fungicide in the United States. Due to the widespread use of chlorothalonil, it is important to investigate the effects chlorothalonil may have on estuarine species such as the grass shrimp, Palaemonetes pugio. This study examined the toxicity of chlorothalonil to three life-history stages (embryo, larvae, adult) of the grass shrimp. Also, molting frequency, growth response and metamorphosis from a larval life cycle pulsed exposure assay were examined as sub-lethal indicators of chlorothalonil exposure. Results showed embryos were the least sensitive with a 96-h Median Lethal Concentration (LC50) of 396.0 μg/L (95% Confidence Interval [CI] 331.3-472.4 μg/L). The adult 96-h LC50 was 152.9 μg/L (95% CI 120.3-194.5 μg/L). Larvae were the most sensitive to chlorothalonil exposure with a 96-h LC50 of 49.5 μg/L (95% CI 44.4-55.27 μg/L). In the life cycle pulsed exposure assay, all surviving larvae in the treatments required significantly more molts to reach postlarvae than the control. Other measured parameters showed differences between treatments and control but there was no statistical significance. This research demonstrated that chlorothalonil is highly toxic to grass shrimp and that larval grass shrimp would be the most appropriate life stage to use for chlorothalonil risk assessments since that stage is the most sensitive. [ABSTRACT FROM AUTHOR]

Predation by visual predators is often affected by light conditions and may therefore exhibit strong diel variation. The dominant predators on grass shrimp, Palaemonetes pugio, are finfish predators that are thought to locate their prey by visual cues. We examined the response of grass shrimp to diel variation in predation risk in the nearshore shallow waters of the Chesapeake Bay. We used diel shoreline seines to assess the relative abundance of predators. We assessed the relative risk of predation with shrimp tethered at refuge (30 cm) and nonrefuge (60 cm) depths. To measure grass shrimp response to predation risk, we used dipnets to monitor habitat use. Four predominantly visual predators dominated the shoreline seine catches, Fundulus heteroclitus, Micropogonias undulatus, Morone americana and Morone saxatilis. Total predator abundance had a diel component, with dramatic nighttime decreases in total abundance, whereas guild composition and relative abundance remained unchanged. Relative predation risk for tethered shrimp exhibited significant time by habitat interaction. During the day, depth negatively affected survivorship of tethered shrimp while at night overall survivorship increased and there was no effect of depth. Shrimp habitats use reflected diel predation risks. Abundances in the near shore were highest during the day with decreased abundances at night. Together, the seine and tethering data highlight the importance for a refuge (e.g., shallow water) from predation during the daytime and a relaxation of predation pressure at night. [Copyright &y& Elsevier]

Although much is known regarding photoperiodic effects on crustacean egg production, the effects of ultraviolet (UV) light on reproduction has not been investigated. Likewise, little is known concerning the interaction between UV and xenobiotic exposure on crustacean reproductive cycles. In this study, male and female grass shrimp, Palaemonetes pugio, were exposed to sublethal concentrations of endosulfan (200 ng/l and 400 ng/l ES) under both white fluorescent (WF) and UV-A (315–400 nm) light conditions for 50 days in laboratory bioassays. Female endocrine (vitellogenin, ecdysteroids, and cholesterol), reproductive (percent gravid, clutch size), and embryo (days to hatch, hatching success, and hatching survival) responses were assessed. UV-exposure alone caused a significant (>4-fold) increase in total Palaemonetes pugio female egg production over the course of 50 days. Exposure to ES and UV significantly lowered the percentage of gravid females relative to UV controls, whereas ES-exposed shrimp under WF lighting did not exhibit these trends. Although higher vitellogenin concentrations and lower ecdysteroid titers were correlated with increased female egg production, cholesterol titers only exhibited a dose-dependent change when exposed to ES. Embryos from females exposed to UV had significantly lower ecdysteroid titers and shorter hatching times but there were no differences in embryo vitellogenin concentrations, hatching success, or hatching survival. These results indicate that UV-A exposure has a pronounced effect on grass shrimp (Palaemonetes pugio) reproduction and is likely mediated through 5-hydroxytrptamine (5-HT)-related neuroendocrine pathways. The implications for decapod aquaculture and evaluating chronic contaminant effects are discussed. [ABSTRACT FROM AUTHOR]