Effects of endosulfan exposure and Taura Syndrome Virus infection on the survival and molting of the marine penaeid shrimp, Litopenaeus vannamei

Molting in crustaceans is an important endocrine-controlled biological process that plays a critical role in growth and reproduction. Many factors can affect this physiological cycle in crustaceans including environmental stressors and disease agents. For example the pathology of Taura Syndrome Virus (TSV) of shrimp is closely related to molting cycle. Similarly, endosulfan, a commonly used pesticide is a potential endocrine disruptor. This study explores interrelationships between pesticide exposure, virus infection and their interactions with physiology and susceptibility of the shrimp. Litopenaeus vannamei (Pacific white shrimp) were challenged with increasing doses of endosulfan and TSV (TSV-C, a Belize reference strain) to determine the respective median lethal concentrations (LC₅₀s). The 96-h endosulfan LC₅₀ was 5.32 μg L⁻¹, while the 7-d TSV LC₅₀ was 54.74 mg L⁻¹. Subsequently, based on their respective LC₅₀ values, a 20-d interaction experiment with sublethal concentrations of endosulfan (2 μg L⁻¹) and TSV (30 mg L⁻¹) confirmed a significant interaction (p < 0.05, χ² = 5.29), and thereby the susceptibility of the shrimp. Concurrently, molt-stage of animals, both at the time of exposure and death, was compared with mortality. For animals challenged with TSV, no strong correlation between molt-stage and mortality was observed (p > 0.05). For animals exposed to endosulfan, animals in the postmolt stage were shown to be more susceptible to acute toxicity (p < 0.05). For animals exposed to both TSV and endosulfan, interference of endosulfan-associated stress lead to increasingly higher susceptibility at postmolt (p < 0.05) during the acute phase of the TSV disease cycle.     

Tolerance of the periwinkles Pachymelania aurita (Muller) and Tympanotonus fuscatus (Linne) to refined oils

Tolerance of Pachymelania aurita (Muller) and Tympanotonus fuscatus (Linne) to kerosene, diesel, and gasoline was studied. Emulsions of these refined oils were observed to be more harmful when compared with such oil films on the water surface. T. fuscatus was observed to be less susceptible to such exposures. After 48 h exposure to kerosene, diesel, and gasoline, as an oil film on the water surface, there was no significant difference in the mean survival values obtained for T. fuscatus and P. aurita, respectively. However, the differences in the mean survival values obtained for P. aurita in emulsions of these three refined oils were statistically significant, following a trend of kerosene > diesel > gasoline in order of toxic effects. The values for T. fuscatus showed no significant differences.     

Lethal and sublethal effects of the pyrethroid, bifenthrin, on grass shrimp (Palaemonetes pugio) and sheepshead minnow (Cyprinodon variegatus)

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 microg/L (95% CI: 0.015-0.025 microg/L) and for larval shrimp was 0.013 microg/L (95% CI: 0.011-0.016 microg/L). The 96-h aqueous LC50 for adult sheepshead minnow was 19.806 microg/L (95% CI: 11.886-47.250 microg/L). The 24-h sediment LC50 for adult shrimp was 0.339 microg/L (95% CI: 0.291-0.381 microg/L) and for larval shrimp was 0.210 microg/L (95% CI: 0.096-0.393 microg/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.     

Lethal and sublethal effects of the pyrethroid,bifenthrin, on grass shrimp (Palaemonetes pugio) and sheepshead minnow (Cyprinodon variegatus)

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.     

Toxicity of the mosquito control pesticide Scourge to adult and larval grass shrimp (Palaemonetes pugio)

This study investigated the toxicity of various concentrations of technical resmethrin and Scourge on adult and larval Palaemonetes pugio, a common grass shrimp species. Two types of tests were conducted for each of the resmethrin formulations using adult and larval grass shrimp life stages, a 96-h static renewal aqueous test without sediment, and a 24-h static nonrenewal aqueous test with sediment. For resmethrin, the 96-h aqueous LC50 value for adult shrimp was 0.53 microg/L (95% confidence interval (CI): 0.46-0.60 microg/L), and for larval shrimp was 0.35 microg/L (95% CI: 0.28-0.42 microg/L). In the presence of sediment, technical resmethrin produced a 24-h LC50 value for adult shrimp of 5.44 microg/L (95% CI: 4.52-6.55 microg/L), and for larval shrimp of 2.15 microg/L (95% CI: 1.35-3.43 microg/L). For Scourge, the 96-h aqueous LC50 for adult shrimp was 2.08 microg/L (95% CI: 1.70-2.54 microg/L), and for larval shrimp was 0.36 microg/L (95% CI: 0.24-0.55 microg/L). The 24-h sediment test yielded an LC50 value of 16.12 microg/L (95% CI: 14.79-17.57 microg/L) for adult shrimp, and 14.16 microg/L (95% CI: 12.21-16.43 microg/L) for larvae. Adjusted LC50 values to reflect the 18% resmethrin concentration in Scourge are 0.37 microg/L (adult), 0.07 microg/L (larvae) for the 96-h aqueous test, and 2.90 microg/L (adult), 2.6 microg/L (larvae) for the 24-h sediment test. Larval grass shrimp were more sensitive to technical resmethrin and Scourge than the adult life stage. The results also demonstrate that synergized resmethrin is more toxic to P. pugio than the nonsynergized form, and that the presence of sediment decreases the toxicity of both resmethrin and Scourge.     

Concentrations of pentachlorophenol (PCP) in fish and shrimp in Jiangsu Province, China

Pentachlorophenol (PCP) concentrations were determined in 55 samples of fish, shrimp, crabs, frogs and turtles collected in Jiangsu Province and 55 freshwater shrimp samples collected from the Huiming Fish Market, Nanjing, China between 2003 and 2004. PCP concentrations ranged from less than the method detection limit (MDL: 0.5 microg/kg ww) to 61 microg/kg ww, with a mean of 5.2 microg/kg ww in 55 samples collected across Jiangsu Province and a mean of 0.5 microg/kg ww for freshwater shrimp collected from the Huiming Fish Market. Concentrations of PCP in common carp (Carassius auratus) were significantly greater than concentrations of PCP in other species from all of the areas studied. Grass carp (Ctenopharyngodon idella) contained the second greatest concentrations and crustacean species contained the least concentrations. Concentrations of PCP were greater in samples collected from Southern Jiangsu than those collected from other areas of Jiangsu Province. Concentrations of PCP in the freshwater shrimp (Macrobrachium nipponense) from the Huiming Fish Market were greater in March and September than those collected in June and December. Based on the allowable daily intake (ADI) set by the US National Academy of Science, current concentrations of PCP measured in aquatic products from Jiangsu Province presented minimus health risks to humans.     

Flame retardants, surfactants and organotins in sediment and mysid shrimp of the Scheldt estuary (The Netherlands)

Sediment and mysids from the Scheldt estuary, one of the largest and most polluted estuaries in Western Europe, were analyzed for a number of contaminants that have been shown to possess endocrine-disrupting activity, i.e. organotins, polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBPA), nonylphenol ethoxylates (NPE) and transformation products, nonylphenol (NP) and nonylphenol ether carboxylates (NPEC). In addition, in vitro estrogenic and androgenic potencies of water and sediment extracts were determined. Total organotin concentrations ranged from 84 to 348 ng/g dw in sediment and 1110 to 1370 ng/g dw in mysid. Total PBDE (excluding BDE-209) concentrations ranged from 14 to 22 ng/g dw in sediment and from 1765 to 2962 ng/g lipid in mysid. High concentrations of BDE-209 (240-1650 ng/g dw) were detected in sediment and mysid (269-600 ng/g lipid). Total HBCD concentrations in sediment and mysid were 14-71 ng/g dw and 562-727 ng/g lipid, respectively. Total NPE concentrations in sediment were 1422 ng/g dw, 1222 ng/g dw for NP and 80 ng/g dw for NPEC and ranged from 430 to 1119 ng/g dw for total NPE and from 206 to 435 ng/g dw for NP in mysid. Significant estrogenic potency, as analyzed using the yeast estrogen assay, was detected in sediment and water samples from the Scheldt estuary, but no androgenic activity was found. This study is the first to report high levels of endocrine disruptors in estuarine mysids.     

Trophic transfer of CuO nanoparticles from brine shrimp (Artemia salina) nauplii to convict cichlid (Amatitlania nigrofasciata) larvae: uptake,accumulation and elimination

Environmental Science and Pollution Research - We investigated the trophic transfer potential of CuO-NPs from Artemia salina to Amatitlania nigrofasciata. The Cu uptake was investigated by exposure...     

Reproduction obstacles for the female green neon shrimp (Neocaridina denticulata) after exposure to chlordane and lindane

The purpose of this study was to investigate the effects of chlordane and lindane on reproduction obstacles and endocrine disruption in female green neon shrimp (Neocaridina denticulata). Individuals of N. denticulata, a common inhabitant of freshwater systems in Taiwan, was exposed to different levels of chlordane (1 and 10 ngl(-1)) and lindane (0.1 and 1 microgl(-1)). The reproductive ability and reproductive hormone levels were observed after exposure. According to our findings, an increase in estrogen, induction of a vitellogenin-like protein, and changes in reproductive performance were observed in both chlordane- and lindane-treated shrimp. Thus, it was concluded that chlordane and lindane may cause some reproduction obstacles and disruption of endocrine functions in N. denticulata.     

Physiological effects of metal toxicity on the tropical freshwater shrimp Microbrachium carcinus (Linneo, 1758)

Pilot tests were performed to determine the level at which Zn(++) and Cu(++) ceased to be acutely toxic in Macrobrachium carcinus. The data indicated that the static 96h-LC(50) values for Zn(++) and Cu(++) were 0.2 and 0.1 mg litre(-1) respectively. A differential reduction in respiration and ammonia excretion rates was noted with increasing concentrations of these metals in the water. These levels may in a toxic body burden and a progressive deterioration of gill efficiency. A decrease in respiration and ammonia excretion rates resulted in a decrease in O:N ratios, upon exposure to Zn(++) and Cu(++) concentrations. The ratios obtained indicate that these metals, also increased dependence on carbohydrate or lipid reserves.     

Toxicity of the mosquito control insecticide phenothrin to three life stages of the grass shrimp (Palaemonetes pugio)

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.     

Toxicity of the mosquito control insecticide phenothrin to three life stages of the grass shrimp (Palaemonetes pugio)

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.     

A multi-biomarker approach to assess the impact of farming systems on black tiger shrimp (Penaeus monodon)

This study examined the advantages of the use of biomarkers as an early warning system by applying it to different shrimp farming systems in Soctrang and Camau provinces, main shrimp producers in Mekong River Delta, Vietnam. Shrimp were collected at 15 different farms divided into four different farming systems: three farms were converted from originally rice paddies into intensive shrimp farming systems (IS1, IS2, IS3); three farms were rice-shrimp integrated farming systems (RS4, RS5, RS6); three farms were intensive farming systems (IS7, IS8, IS9); six farms were extensive shrimp farming systems (From ES1 to ES6). Lipid peroxidation (LPO) and total glutathione (GSH) were measured as well as catalase (CAT), glutathione peroxidase (GPX), glutathione S-transferase (GST) and acetylcholinesterase activities (ACHE). Organ specificity was observed between gills and hepatopancreas with generally higher activity of GST in gills (GSTG) whereas the contrary was observed for LPO level in gills (LPOG). Hierarchical clustering and principal component analysis clearly indicated that shrimp reared in extensive culture system formed a distinct group from those reared in intensive or rice-shrimp integrated systems. CAT in gills (CATG), GPX in gills (GPXG) and hepatopancreas (GPXHP) and ACHE in muscle (ACHEM) of shrimp collected in extensive farms showed a general higher level than those in intensively farmed shrimp. On the contrary, we observed clear high levels of GSTG and GST in hepatopancreas (GSTHP) and LPOG and hepatopancreas (LPOHP) of shrimp sampled in intensive and rice-shrimp integrated systems. Thus, we propose that LPO and CAT, GPX, GST and ACHE can be used as a set of biomarkers for the assessment of health condition and can discriminate between shrimp cultivated in different farming systems. These findings provide the usefulness of integrating a set of biomarkers to define the health status of shrimp in different shrimp culture systems.     

Effects of cadmium and zinc on oxygen consumption, ammonium excretion, and osmoregulation of white shrimp (Litopenaeus vannamei)

White shrimp, Litopenaeus vannamei, a globally important cultured prawn species, is an ideal animal for studying the impairment caused by the effects of heavy metals that are often detected in coastal areas. The main purpose of the present study was to detect the acute toxicity of Cd and Zn to L. vannamei, and to investigate their effects on gill functions, which have not been carried out in this species before, hoping to obtain some important significance. First of all, we examined the acute toxicity of cadmium (Cd) and zinc (Zn) to L. vannamei and obtained 24-, 48-, 72-, and 96-h medium lethal concentration (LC₅₀) values of 2.58, 1.30, 1.14, and 1.07 mg Cd l⁻¹ and 3.98, 2.14, 1.75, and 1.35 mg Zn l⁻¹, respectively. Furthermore, we also found that exposure of shrimp to Cd or Zn caused an inhibition in oxygen consumption of 91.3% and 75.9% lower than that of the control. However, after separate exposure to Cd or Zn, elevations in ammonium excretion were obtained, which were 153.7% and 144.1%, respectively, higher than the control. It is most likely that elevations in ammonium excretion were related to decreased osmotic pressure of shrimp blood. Finally, the distribution of Cd and Zn within gills was also determined.     

Metal accumulation in the greentail prawn, Metapenaeus bennettae, in Sydney and Port Hacking estuaries, Australia

Metal concentrations of the inshore greentail prawn, Metapenaeus bennettae, and surface sediments from locations within Sydney estuary and Port Hacking (Australia) were assessed for bioaccumulation and contamination. The current study aimed to assess metal concentrations in prawn tissue (tail muscle, exoskeleton, hepatopancreas and gills), relate whole body prawn tissue metal concentrations to sediment metal concentrations and animal size, as well as assess prawn consumption as a risk to human health. Metal concentrations were highest in sediment and prawns from contaminated locations (Iron Cove, Hen and Chicken Bay and Lane Cove) in Sydney estuary compared with the reference estuary (Port Hacking). Concentrations in sediments varied considerably between sites and between metals (As, Cd, Cr, Cu, Ni, Pb and Zn), and although concentrations exceeded Interim Sediment Quality Guideline-Low values, metals (As, Cd, Cr, Cu, Ni, Pb and Zn) were below Australian National Health and Medical Research Council human consumption guidelines in prawn tail muscle tissue. Metal concentrations in prawn tail muscle tissue were significantly different (p?≤?0.05) amongst locations for Pb, Zn and Cd, and metal concentrations were generally highest in gills tissue, followed by the hepatopancreas, exoskeleton and tail muscle. The exoskeleton contained the highest Sr concentration; the hepatopancreas contained the highest As, Cu and Mo concentrations; and the gills contained the highest Al, Cr, Fe and Pb concentrations. Concentrations of Pb, As and Sr were significantly different (p?≤?0.05) between size groups amongst locations.     

A freshwater shrimp (Paratya compressa improvisa) as a sensitive test organism to pesticides

The susceptibility of 2-week-old individuals of the freshwater shrimp, Paratya compressa improvisa, to five kinds of insecticide and five kinds of herbicide was examined in comparison with that of two species of Cladocera, Daphnia magna and Moina macrocopa. The shrimp was especially sensitive to two organophosphorus insecticides. The 48-h LC50 values for fenitrothion and fenthion to the shrimp were 1.15 and 1.04 microg litre(-1) (mean value, n=2), in contrast with 37.8 and 35.3 microg litre(-1) in the case of M. macrocopa, and more than 50 microg litre(-1) with D. magna. The shrimp also showed the higher susceptibility to other insecticides, diazinon, carbaryl (NAC) and BPMC, apart from D. magna to diazinon and NAC. The shrimp also showed higher susceptibility to herbicides. The 48-h LC50 values of CNP, benthiocarb, oxadiazon, butachlor, and symetryne to the shrimp were two to eight times lower than those of two species of Cladocera, except for the LC50 value of oxadiazon to M. macrocopa, which was very slightly higher. However, the shrimp showed a somewhat lower susceptibility to heavy metals than the two species of Cladocera, especially to copper, and to cadmium and zinc in comparison with D. magna. A bioassay using the shrimp with river water, collected from the river adjacent to the paddy field, showed clearly the high mortality of the shrimp following the aerial spraying with pesticides.     

Field investigation on the toxicity of Alaska North Slope crude oil (ANSC) and dispersed ANSC crude to Gulf killifish, Eastern oyster and white shrimp

A field investigation was conducted on a Louisiana Spartina alterniflora shoreline to evaluate the toxic effects of crude oil (Alaska North Slope crude oil, ANSC) and dispersed oil (ANSC + dispersant Corexit 9,500) on three aquatic species indigenous to the Gulf of Mexico: Fundulus grandis (Gulf killifish), Crassostrea virginica (Eastern oyster), and Litopenaeus setiferus (white shrimp). Results indicated that total hydrocarbons concentration value in oiled treatments decreased rapidly in 3h and were below 1 ppm at 24h after initial treatment. Corexit 9,500 facilitated more ANSC fractions to dissolve and disperse into the water column. L. setiferus showed short-term sensitivity to the ANSC and ANSC + 9,500 at 30 ppm. However, most test organisms (>83%) of each species survived well after 24h exposure to the treatments. Laboratory tests conducted concurrent with the field investigation indicated that concentrations of crude oil higher than 30 ppm were required for any significant toxic effect on the juvenile organisms tested.     

Effects of T-2 toxin on histopathology,fatty acid and water distribution of shrimp (Litopenaeus vannamei) muscle

T-2 toxin (T-2), one of the naturally occurring mycotoxins, often accumulates in aquatic animals from contaminated feed. Shrimp (n?=?30 per group) were fed with different concentrations (0, 0.5, 1.5, 4.5 and 13.5?mg kg^?1) of T-2 for 20?days. Changes in histopathology, fatty acid and water distribution of shrimp muscle were analyzed. Histopathology of shrimp muscle showed dose-dependent marked degenerative and necrotic changes on exposure to dietary T-2. The T-2 significantly (P?<?0.05) affected the muscle fatty acid composition. ∑SFA, ∑MUFA and ∑PUFA initially decreased and then increased slowly in the high-dosed groups. C16:0, C18:1n-9 and C18:2n-6 were the main saturated fatty acid (SFA), monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA), respectively. Also, T-2 significantly affected water distribution in shrimp muscle. High doses of T-2 reduced free water content, resulting in a reduction in the water holding capacity and hence changes to the shrimp muscle quality. Collectively, these results illustrated that T-2 significantly affects the fatty acid and water distribution, and also muscle histopathology, all of which would result in a reduction in the quality and nutritional value of shrimp.     

Measurement of pollution levels of organochlorine and organophosphorus pesticides in water, soil, sediment, and shrimp to identify possible impacts on shrimp production at Jiquilisco Bay

This study aims to identify levels of several organochlorine and organophosphorus compounds in shrimp-raising areas of coastal El Salvador, to assess potential impacts on shrimp growth and survival that hamper the sustainability of aquaculture in the region. The paper reports the current levels of γ-HCH, 4,4'-DDT, 4,4'-DDE, 4,4'-DDD, endrin, dieldrin, heptachlor, parathion, methyl parathion, and etoprophos in soils (depth 20 cm), sediments (depth 5 cm), shrimp (Penaeus sp.), and water of three rearing ponds and also in the sediment (depth 5 cm) and water surrounding those ponds in Jiquilisco Bay. Sampling was carried out during the dry (January-March) and rainy (June-August) seasons of 2008. The presence of pesticides in the samples of water, shrimp, and sediment at shrimp ponds was not detected in either season; however, in soil samples (depth 20 cm) taken from these ponds, heptachlor, endrin, dieldrin, 4,4'-DDD, and 4,4'-DDT were identified at concentrations below the method limit of quantification (LOQ), and 4,4'-DDE was found in a concentration falling in the range from 3.85 to 19.61 ng/g. In samples of water taken at the bay water intakes to the rearing ponds, we observed dieldrin concentrations in the range between 0.085 ng/mL and 0.182 ng/mL during the dry season. In the samples of sediments taken in the surrounding areas of shrimp ponds, we found-for both seasons-that in 60 % of the samples, 4,4'-DDE was present in concentrations ranging from 3.75 ng/g to 30.97 ng/g. Additionally, in the rainy season, we observed heptachlor in sediment at concentrations below the method quantification limit. It was concluded that organochlorine compounds from pesticides are still present in Jiquilisco Bay, trapped in deep sediment, even though they have been banned since the 1980s. These were not detected in shrimp tissue, surface water, and shallow sediment in rearing ponds, and hence, we do not believe their presence has any major impact on shrimp production in sampled areas.     

The chronic toxicity of fenoxycarb to larvae of the grass shrimp,Palaemonetes pugio

Abstract

This study examined effects of fenoxycarb, a carbamate insecticide, on larvae of the grass shrimp, Palaemonetes pugio. In laboratory experiments, grass shrimp larvae were exposed to fenoxycarb from hatch to postlarval metamorphosis in a chronic, static renewal bio assay. LC50's ranged from 0.92 mg/L at 96 h to 0.35 mg/L at the end of the study (24 days). In assessing sublethal effects of fenoxycarb, postlarval emergence was significantly (p < 0.05) reduced in exposed grass shrimp as compared with controls, and the time to reach postlarval status was significantly (p < 0.05) increased in exposed grass shrimp. Significant differences were not found in other sublethal parameters including postlarval dry weight and intermolt duration. Analysis of fenoxycarb from spiked seawater samples showed concentrations declined by 32 to 42% after 24 h.