High Sublethal Concentrations Research Articles

High pesticide tolerance of S. mansoni: implications for the risk of schistosomiasis

BackgroundSchistosomiasis is a neglected tropical disease caused by trematodes of the genus Schistosoma. The pathogen is transmitted via freshwater snails. These snails are highly tolerant to agricultural pesticides and indirectly benefit from exposure due to adverse effects on their more sensitive enemy species. Pesticides in surface waters may thus increase the risk of schistosomiasis transmission unless they also affect the pathogen. We tested the tolerance of the free-swimming life stages (miracidia and cercariae) of Schistosoma mansoni to the insecticides diazinon and imidacloprid. We also investigated whether these pesticides decrease the ability of miracidia to infect and further develop as sporocysts within the host snail Biomphalaria pfeifferi.ResultsExposure to imidacloprid for 6 and 12 h immobilized 50% of miracidia at 150 and 16 µg/L, respectively (nominal EC50); 50% of cercariae were immobilized at 403 and 284 µg/L. Diazinon immobilized 50% of miracidia at 51 and 21 µg/L after 6 and 12 h; 50% of cercariae were immobilized at 25 and 13 µg/L. The observed insecticide tolerance is lower than those of the host snail B. pfeifferi and comparable to those of other commonly tested freshwater invertebrates. Exposure for up to 6 h decreased the infectivity of miracidia at high sublethal concentrations (48.8 µg imidacloprid/L and 10.5 µg diazinon/L, i.e. 20–33% of EC50), but not at lower concentrations commonly observed in the field (4.88 µg imidacloprid/L and 1.05 µg diazinon/L). The development of sporocysts within the snail host was not affected at any of these test concentrations.ConclusionsInsecticides did not affect the performance of S. mansoni at environmentally relevant concentrations. Particularly within its host snail the pathogen can escape exposure peaks that have been shown to affect other sensitive invertebrates and their biological control of host snails. Our findings suggest that freshwater pollution with agricultural pesticides increases the risk of schistosomiasis; they illustrate the need to integrate an environmental and public health risk assessment and management.

Analysis of Sanitizer Rotation on the Susceptibility, Biofilm Forming Ability and Caco-2 Cell Adhesion and Invasion of Listeria.

The purpose of this study was to determine the effect of sanitizer use conditions on the susceptibility, biofilm forming ability and pathogenicity of Listeria monocytogenes. Two different strains of L. monocytogenes and a non-pathogenic L. innocua were exposed to sodium hypochlorite, benzalkonium chloride and peroxyacetic acid at different concentrations (4 to 512 ppm) and treatment times (30 s to 5 min), respectively. Under the tested conditions, no significant difference (p > 0.05) in reduction was observed among the three tested sanitizers. A reduction of 1 to 8 log CFU/mL was observed depending upon the sanitizer concentration and treatment times. The survived cells at the highest sublethal concentration and treatment time of a particular sanitizer upon re-exposure to the same or different sanitizer showed either no change or increased susceptibility when compared to parent strains. Upon repeated exposure to sanitizers at progressively increasing concentrations from 1 to 128 ppm, L. innocua was able to survive concentrations of up to 32 ppm benzalkonium chloride and 64 ppm peroxyacetic acid treatments, respectively. At the tested sub-lethal concentrations, no significant difference (p > 0.05) in biofilm formation was observed among the tested strains. Caco-2 interaction with L. innocua showed a reduction in invasion ability with sublethal concentrations of sanitizers.

Toxic Effect Of Monocrotophos On Various Blood Parameters In Edible Freshwater Fish Oreochromis mossambicus (Tilapia)

In modern agriculture, farmers are using the authenticity of pesticides for agricultural activities. Water bodies are often polluted with various harmfull chemical substances. Fishes are very important for human nourishment. In this study, the effect of Pesticide monocrotophos on various hematological parameters such as RBC, WBC, and Hemoglobin was observed in freshwater fish Oreochromis mossambicus. The fish were exposed to various sub-lethal concentrations (1/10, 1/20, and 1/30) of Monocrotophos for 10, 20, and 30 days. The blood samples were analyzed at the end of every exposure period. Increased count of WBC observed in Lower Sub lethal concentration (21.25, 21.76, 22.01), Medium Sub-lethal concentration (21.69, 22.48, 22.89), and Higher Sub lethal concentration (22.47, 23.54, 23.69) of monocrotophos at various monocrotophos exposure periods on experimental fish Oreochromis mossambicus. Decreased count of RBC observed in Lower Sub-lethal concentration (3.58,3.21,3.08), Medium Sub-lethal concentration (2.97,2.35,2.19) and Higher Sub-lethal concentration (2.41,2.16,2.02) and decreased level of Hemoglobin were observed in Lower Sub-lethal concentration (21.25,21.76,22.01), Medium Sub-lethal concentration (21.69,22.48,22.89) and Higher Sub-lethal concentration (22.47,23.54,23.69) of monocrotophos at various exposure period on fish Oreochromis mossambicus. The 1/10 sub-lethal concentration of monocrotophos showed a high level of variation on 30th-day exposure. Reduction of RBC indicates hemolysis in fish and increased WBC count has been considered to be an adaptation of animals to meet stressful conditions. In the present study, it was found that the effect of monocrotophos alters the activity of various blood parameters in freshwater fish Oreochromis mossambicus. Therefore, the experiment is an attempt to study the toxicity of the pesticide Monocrotophos concerning blood parameters of freshwater fish Oreochromis mossambicus. It is concluded from this study that exposure to Monocrotophos affects the hematological parameters of fish.

Temperature sensitive effects of the neonicotinoid clothianidin on bumblebee (<i>Bombus terrestris</i>) foraging behaviour

Pollinating insects are an inherent part of most terrestrial ecosystems as they provide a crucial service for most angiosperms, including numerous important crops. A decrease in pollinator populations can therefore have severe consequences for both natural ecosystems and agricultural yields. Pesticide usage has been pointed out as one of the drivers behind pollinator declines. Globally, neonicotinoids are one of the most commonly used insecticides and studies have shown that exposure at sub-lethal levels can alter foraging behaviour, ultimately negatively affecting survival.Using a custom-made bumblebee colony monitoring system, we examined how the number and duration of foraging bouts of bumblebees (Bombus terrestris) on an individual level, and hive growth rate, was affected by exposure to low (6.5 µg/L) and high (10.6 µg/L) sub-lethal concentrations of the neonicotinoid clothianidin via nectar. We also examined possible interaction between clothianidin exposure and abiotic factors (temperature and precipitation), and its impact on foraging bout number and duration.Exposure to sublethal concentrations of clothianidin increased foraging bout duration in bumblebees. Furthermore, the foraging bout duration decreased with increasing temperature at both exposure concentrations, whereas the unexposed control group was not affected by temperature. Neither number of foraging bouts nor the daily rhythm of foraging bout duration was affected by clothianidin exposure or temperature. The foraging bout duration decreased with increasing precipitation in both exposed and non-exposed groups. However, we did not find any interaction between precipitation and exposure, suggesting that precipitation does not affect toxicity.Our study shows the importance of semi-natural experiments and accounting for ambient factors when assessing the risk that pesticide exposure may present to pollinators. We conclude that the effect of clothianidin exposure on bumblebee foraging behaviour is temperature sensitive and that local climatic conditions and future climate change scenarios should be considered in risk assessments of clothianidin and other insecticides.

Acceleration of emergence of E. coli antibiotic resistance in a simulated sublethal concentration of copper and tetracycline co-contaminated environment

An environment co-contaminated with metals and antibiotics ultimately exposes bacteria to these metals and antibiotics simultaneously. This study aims to explore the efficacy of sublethal concentrations of copper ions contaminated with tetracycline regarding antibiotic resistance in a sensitive strain of E. coli K12. The study proved that a copper ions and tetracycline co-contaminated environment could considerably enhance the mutation frequencies of chloramphenicol and polymyxin B resistance in antibiotic susceptible E. coli; however, the equivalent copper ions and tetracycline alone showed weaker effects. Results also demonstrated that an environment co-contaminated with relatively high sublethal concentrations of copper ion and tetracycline co-contaminated environment could induce much higher antibiotic resistance than the low sublethal and control groups. Whole-genome characterization results indicated that variability existed within the genotype and phenotype involved in antibiotic resistance. Additionally, the evolved resistant strains displayed hereditary resistance after 5 round culture cycles in LB broth over 5 days. Results implied that co-contamination with metals and antibiotics environment could strengthen resistance and contribute to the induction and dissemination of antibiotic resistance in metal and antibiotic co-contaminated environment.

Impact of pesticide monocrotophos on microbial populations and histology of intestine in the Indian earthworm Lampito mauritii (Kinberg)

Soil contamination has enlarged over the decades due to intensive use of pesticides and chemical fertilizers in agronomy. Earthworms are significant organisms in the soil community. Earthworms are the major role in soil fertility in most ecological system and the production of biogenic structures. Moreover, earthworm gut mucus enhances the beneficial soil microorganism potential biological activities. They are used as model organisms for assessing the ecological risks of chemicals. Enrichment of essential nutrients in soil through earthworm is a cost-effective and eco-friendly approach. In India, the organophosphorus pesticide monocrotophos is commonly used to control agricultural pests. Hence, it is important to study the effect of monocrotophos on the gut microbiota in Lampito mauritii. A 15-day exposure to a low (1/10th of the LC50 after 96 h i.e., 0.093 ppm kg−1) and high sublethal concentration (1/3rd of the LC50 after 96 h i.e., 0.311 ppm kg−1) of monocrotophos led to reduced proliferation of the gut microbiota in L. mauritii. However, exposure for 30 days led to a recuperation of the microbial populations to near control values. Among the eight bacterial and five fungal species that inhabit the gut of L. mauritii, only six bacterial and three fungal species were able to survive after exposure to monocrotophos. In addition to the study, histopathological changes were observed in the intestine of L.mauritii after application of lower sublethal concentration of monocrotophos. Severe pathological changes such as vacuolization, degenerated nuclei, damaged villi and congestion of the blood sinuses were noticed in the intestine on 1st and, 5th day of the experiment. But in 30th day the damages were slowly recovered due to degradation of monocrotophos by the presence of some pesticides degrading bacterial and fungal species and regenerative capability of chloragogen cells in the intestine. The results suggested that reduced microbial populations and pathological damages in intestine were observed during the application of monocrotophos. So, the monocrotophos have several harmful impacts on earthworms.

Neuro- and hepatic toxicological profile of (S)-2,4-diaminobutanoic acid in embryonic, adolescent and adult zebrafish.

(S)-2,4-Diaminobutanoic acid (DABA) is a noncanonical amino acid often co-produced by cyanobacteria along with β-N-methylamino-l-alanine (BMAA) in algal blooms. Although BMAA is a well-established neurotoxin, the toxicity of DABA remains unclear. As part of our development of biocompatible materials, we wish to make use of DABA as both a building block and as the end-product of enzymatically induced depolymerization; however, if it is toxic at very low concentrations, this would not be possible. We examined the toxicity of DABA using both in vivo embryonic and adult zebrafish models. At higher sublethal concentrations (700μm), the fish demonstrated early signs of cardiotoxicity. Adolescent zebrafish were able to tolerate a higher concentration. Post-mortem histological analysis of juvenile zebrafish showed no liver or brain abnormalities associated with hepato- or neurotoxicity. Combined, these results show that DABA exhibits no overt toxicity at concentrations (100-300μm) within an order of magnitude of those envisioned for its application. This study further highlights the low cost and ease of using zebrafish as an early-stage toxicological screening tool.

Integrated assessment of biochemical markers in premetamorphic tadpoles of three amphibian species exposed to glyphosate- and methidathion-based pesticides in single and combination forms.

In this study, we evaluated the toxic effects of a glyphosate-based herbicide (GBH) and a methidathion-based insecticide (MBI), individually and in combination, on premetamorphic tadpoles of three anuran species: Pelophylax ridibundus, Xenopus laevis, and Bufotes viridis. Based on the determined 96-h LC50 values of each species, the effects of a series of sublethal concentrations of single pesticides and their mixtures after 96-h exposure and also the time-related effects of a high sublethal concentration of each pesticide were evaluated, with determination of changes in selected biomarkers: glutathione S-transferase (GST), glutathione reductase (GR), acetylcholinesterase (AChE), carboxylesterase (CaE), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH). Also, the integrated biomarker response (IBR) was used to assess biomarker responses and quantitatively evaluate toxicological effects. Isozyme differences in CaE inhibition were assessed using native page electrophoresis; results showed that GBH to cause structural changes in the enzyme but not CaE inhibition in P.ridibundus. In general, single MBI and pesticide mixture exposures increased GST activity, while single GBH exposures decreased GST activity in exposed tadpoles. The AChE and CaE activities were inhibited after exposure to all single MBI and pesticide mixtures. Also, higher IBR values and GST, GR, AST, and LDH activities were determined for pesticide mixtures compared with single-pesticide exposure. This situation may be indicative of a synergistic interaction between pesticides and a sign of a more stressful condition.

Bioaccumulation and Depuration Rates of Zinc by Capoeta fusca Under Controlled Conditions

The aim of this study was to investigate the bioaccumulation and depuration level of zinc (Zn) by Capoeta fusca in the laboratory condition. The fishes were exposed to two concentrations, i.e., 3.6 and 9.75 mg/L of Zn for 21 days to allow uptake and then transferred to clean water for elimination (10 days). At 21 days of Zn exposure for lower sub-lethal and higher sub-lethal concentrations, the order of Zn bioaccumulation pattern in organs was kidney > liver > gill > muscle and after 10 days; depuration pattern for lower and higher sub-lethal concentrations was gill > liver > muscle > kidney. The highest Zn accumulation was observed in the kidney for lower and higher sub-lethal concentrations. The depuration level of Zn in the gill was the highest for lower and higher sub-lethal concentrations. This study reports the kidney and gill as the target organs for Zn accumulation and depuration in C. fusca, respectively.

LATENT EFFECTS OF IRANIAN CRUDE OIL AND A CHEMICAL OIL DISPERSANT ON RED SEA MOLLUSCS

ABSTRACT Predation rate of the gastropod drill, Drupa granulata, on the mussel, Mytilus variabilis, was measured over a period of 28 days after adults from both species had been immersed for 168 h in seawater solutions containing high sublethal concentrations (10 ml/liter) of Iranian crude oil. Predation rate was three times higher in controls than in the group where both predator and prey had been exposed initially; intermediate values were determined among groups where only one species had been treated initially. Fecundity of drills, as evidenced by number of egg cases deposited, was directly related to mussel consumption. In a similar study with a chemical oil dispersant, exposure to high (0.003 ml/liter) sublethal levels for 168 h did not affect markedly the rate at which mussels were destroyed and consumed during post-treatment. However, the fecundity of untreated drills feeding on untreated mussels (controls) was 3 to 10 times greater than among groups in which one or both species had been exposed i...

Teratogenic Effects of 4-Nonylphenol on Early Embryonic and Larval Development of the Catfish Heteropneustes fossilis

Alkylphenol polyethoxylates (APEs), which are widely used in detergents, paints, herbicides, insecticides, and in many other formulations, have been widely detected in aquatic environments. 4-Nonylphenol (NP) is an important APE detected at microgram levels per litre (0.1-336 μg/L) in water. The objective of the present study was to evaluate NP's toxic effects at low and high sublethal concentrations (0.1 and 1 μg/L) on embryonic development of the catfish Heteropneustes fossilis at different time intervals. The data show that fertilization rate was decreased and cleavage and blastula were severely affected leading to complete mortality of embryos. NP exposure resulted in various body malformations in larvae, such as vertebral deformations, e.g., fin blistering/necrosis, axial deformities (lordosis, kyphosis, and scoliosis) of the spine in the abdominal and caudal region, tail curved completely backward, shortened body, severe spinal and yolk sac malformations, C-shaped severe spinal curvature, cranial malformation with undeveloped head, and failure of eye development. The level of body malformations increased with the concentration and exposure time. After 72 h of exposure, all larvae were dead at both concentrations. Scanning electron microscope study showed that epidermal cells (keratinocytes) were severely damaged in both low- and high-dose treatments throughout development, leading to development of numerous depressions representing sinking holes on the skin. Mucous glands increased significantly in treatment groups compared with control groups. The present study highlights the severe teratogenic effects of NP. The prevalence of the contaminant, if not checked, can lead to decreased population and ultimate disappearance of the species.

Acetyl cholinesterase activity and muscle contraction in the sea urchin Lytechinus variegatus (Lamarck) following chronic phosphate exposure

The common shallow-water sea urchin Lytechinus variegatus is capable of surviving inorganic phosphate exposures as high as 3.2 mg L(-1) and organic phosphate exposures of 1000 mg L(-1) . Nonetheless, chronic exposure to low, medium, and high-sublethal concentrations of organic phosphate inhibits the muscle enzyme acetyl cholinesterase (AChE), responsible for the break down of the neurotransmitter acetylcholine, as well as inhibiting contractions in the muscles associated with the Aristotle's lantern. AChE activity, measured in both a static enzyme assay and by vesicular staining, displayed concentration-dependent declines of activity in individuals maintained in organic phosphate for 4 weeks. The activity of AChE was not adversely affected by exposure to inorganic phosphate or seawater controls over the same time period. Maximum force of muscle contraction and rates of muscle contraction and relaxation also decreased with chronic exposure to increasing concentrations of organic phosphate. Chronic exposure to inorganic phosphates elicited no response except at the highest concentration, where the maximum force of muscular contraction increased compared to controls. These findings indicate that shallow-water populations of Lytechinus variegatus subjected to organic phosphate pollutants may display impaired muscular activity that is potentially related to the inhibition of the muscle relaxant enzyme AChE, and subsequently muscular overstimulation, and fatigue.

Bioaccumulation and elimination of nickel in the organs of black fish (Capoeta fusca)

Since toxicity is based on the effect that a toxicant produces at a target site within an organism, establishing the relationship between the concentration of substance at the target site and the subsequent toxic effect can provide a tool for predicting toxicity. This article aims to investigate the patterns of bioaccumulation and elimination of nickel in the selected organs of black fish (Capoeta fusca) exposed to two treatments of nickel (4.5 and 12.7 mg/L) for a period of 30 days. Nickel was assayed using Shimadzu AA 680 atomic absorption spectrophotometer, and the results were given as μg/g wet weight. This finding showed that the accumulation patterns of nickel, for lower sub-lethal (LSL) and higher sub-lethal (HSL) concentrations of nickel, are in the following order: gill > liver > muscle > skin. The elimination patterns of nickel are in the following order: gill > skin > muscle > liver, for LSL concentration, and gill > skin > liver > muscle, for HSL concentration of nickel. The results show that the target organ for accumulation and elimination of nickel is gill.

Lethal Effect and In Vivo Genotoxicity of Profenofos to Chinese Native Amphibian (Rana spinosa) Tadpoles

Amphibian populations are decreasing in size due to environmental stressors in most areas of southern China. Pesticides are known to be a group of potential stressors to amphibians, especially in agricultural ecosystems. Profenofos, an organophosphate insecticide and acaricide, is widely used for controlling insect pests in China. The aim of this study is to evaluate the acute lethality and genotoxicity of profenofos to amphibian under controlled conditions. Results showed that profenofos was highly lethal to tadpoles of Rana spinosa, with 50% lethal concentration (LC(50)) values of 1.59, 1.14, 0.77, and 0.58 mg l(-1) at 24, 48, 72, and 96 h, respectively. DNA damage of erythrocytes was observed by alkaline single-cell gel electrophoresis assay at all tested sublethal concentrations. The study also showed, by micronucleus test, that profenofos at moderate to high sublethal concentration might have genotoxicity to the tadpole after 96 h exposure. Furthermore, based on our results, it is suggested that the alkaline single-cell gel electrophoresis assay could be used as a screening tool for biomonitoring of pesticide contamination in aquatic systems or agricultural ecosystems.

The effects of chronic inorganic and organic phosphate exposure on bactericidal activity of the coelomic fluid of the sea urchin Lytechinus variegatus (Lamarck) (Echinodermata: Echinoidea)

The sea urchin Lytechinus variegatus can survive chronic exposure to sodium phosphate (inorganic phosphate) concentrations as high as 3.2 mg L − 1 , and triethyl phosphate (organic phosphate) concentrations of 1000 mg L − 1 . However, chronic exposure to low (0.8 mg L − 1 inorganic and 10 mg L − 1 organic phosphate), medium (1.6 mg L − 1 inorganic and 100 mg L − 1 organic phosphate) or high (3.2 mg L − 1 inorganic and 1000 mg L − 1 organic phosphate) sublethal concentrations of these phosphates inhibit bactericidal clearance of the marine bacterium Vibrio sp. Bacteria were exposed to coelomic fluid collected from individuals maintained in either artificial seawater, or three concentrations of either inorganic phosphate or organic phosphate. Sterile marine broth, natural seawater and cell free coelomic fluid (cfCF) were employed as controls. Bacterial survival indices were measured at 0, 24 and 48 h periods once a week for four weeks. Bacteria were readily eliminated from the whole coelomic fluid (wCF) of individuals maintained in artificial seawater. Individuals maintained in inorganic phosphates were able to clear bacteria following a two week exposure period, while individuals maintained at even low concentrations of organic phosphates failed to clear all bacteria from their coelomic fluid. Exposure to phosphates represses antimicrobial defenses and may ultimately compromise survival of L. variegatus in the nearshore environment.

The Effects of the Herbicide Metolachlor on Agonistic Behavior in the Crayfish, Orconectes rusticus

Previous research suggests that agricultural herbicides interfere with olfactory-mediated behavior, such as responses to alarm signals and the ability to locate food, in aquatic organisms. In crayfish, aggressive interactions are also mediated by chemical signals. These social signals are important in establishing dominance, which in turn has an impact on an individual's ability to find and use mates, food, and habitat space. In this study, we investigated the impact of exposure to sublethal levels of the herbicide metolachlor on the ability of crayfish to respond to olfactory signals used in agonistic behaviors. Crayfish were exposed to three different environmentally relevant concentrations (60 ppb, 70 ppb, and 80 ppb) of metolachlor for 96 hours. Each exposed crayfish was then placed in a fight arena and was allowed to interact with a naïve, untreated crayfish for 15 minutes. We analyzed several characteristics of fighting behavior, including initial aggressiveness, time to fight, intensity levels, duration, number of encounters, and the winner and loser of each fight. Crayfish exposed to 80 ppb metolachlor were less likely to initiate and win encounters against naïve conspecifics than any other treatment group. Analysis of fight dynamics shows that metolachlor does not alter the temporal fighting dynamics within crayfish aggression. We conclude that high sublethal concentrations of metolachlor may be interfering with the ability of crayfish to receive or respond to social signals and thus affect certain agonistic behaviors.

Stressor-specific induction of heat shock protein 70 in the freshwater prawn Macrobrachium malcolmsonii (H. Milne Edwards) exposed to the pesticides endosulfan and carbaryl

Agricultural run off that is contaminated with pesticides enters water bodies, thereby polluting the aquatic environment. The sensitivity of the freshwater prawn, Macrobrachium malcolmsonii, to such pesticides is well-documented. However, the stress response to sublethal concentrations of pesticides has scarcely been investigated. In the present study, the effect of two different sublethal concentrations (1/5th and 1/10th of LC 50 value) of endosulfan and carbaryl on the synthesis of hsp70 in various tissues of the prawn M. malcolmsonii was evaluated by Western blotting analysis. Among the tissues analyzed (gill, skeletal muscle, and hepatopancreas), induction of hsp70 synthesis was recorded only in the gill tissue of the prawns that had been exposed to either the high or low sublethal concentration of endosulfan. Induction of synthesis of hsp70 was not observed in any of the tissues sampled from the prawns that had been exposed to either the low or the high sublethal concentration of carbaryl. Pesticides interfere with the hydrophobic core of protein, thus leading to denaturation of the protein by exposing the lipophilic moieties to the aqueous environment. Specific induction of hsp70 in the gill possibly occurred since the gill is the route of exposure for pesticides in the prawns. The absence of induction of hsp70 synthesis in prawns that had been exposed to carbaryl suggests that induction of hsp70 synthesis is stressor-specific.

Effects of inorganic and organic phosphate exposure on aspects of reproduction in the common sea urchin Lytechinus variegatus (Echinodermata: Echinoidea).

The common nearshore sea urchin Lytechinus variegatus is capable of surviving exposure to inorganic phosphate concentrations as high as 3.2 mg/l(-1) and organic phosphate concentrations of 1,000 mg/l(-1). However, chronic exposure to low, medium, or high sublethal concentrations of these phosphates inhibits gonadal tissue indices and spawning activity while altering biochemical composition of gonads, reducing size frequencies of oocyte diameters, and changing gonadal volume fractions. Gonad indices declined significantly in individuals maintained in all phosphate concentrations after both one- and two-month exposures, while percentages of ripe individuals (oozing gametes upon dissection) were reduced after a two-month exposure in individuals maintained in medium and high organic phosphate concentrations. Levels of carbohydrates and lipids were lower in gonads of individuals maintained in all concentrations of both phosphates. Size frequency distributions of oocyte diameters revealed a dramatic decrease in oocyte size with increasing concentrations of both phosphates. Gonadal volume fractions of developing male and female gametes decreased with exposure to increasing phosphate levels. Volume fractions of nutritive phagocytes declined in testes of individuals held in the highest concentration of organic phosphate but displayed no significant change in ovaries. Volume fractions of mature gametes also decreased in gonads of individuals exposed to increasing concentrations of inorganic phosphate, but they remained constant in individuals exposed to all concentrations of organic phosphate. These findings indicate that shallow-water populations of L. variegatus subjected to inorganic and organic phosphate pollutants will exhibit stress that may impair reproductive output, gametogenesis, and spawning in the natural environment.

The effects of organic and inorganic phosphates on fertilization and early development in the sea urchin Lytechinusvariegatus (Echinodermata: Echinoidea)

The embryos of the sea urchin Lytechinus variegatus are capable of surviving chronic exposure to inorganic sodium phosphate and organic triethyl phosphate concentrations as high as 6 and 1000 mg l −1 seawater, respectively. However, chronic exposure to sub-lethal concentrations of these phosphates may cause arrested or abnormal embryonic development. We measured fertilization success and percentages of normal, arrested and abnormal embryos exposed to low, medium and high sub-lethal concentrations of inorganic and organic phosphate. Fertilization success was significantly reduced in all phosphate treatments. After attaining the 4-cell stage, embryos exposed to the highest phosphate concentrations displayed arrested development. Percentages of abnormally developing embryos showed a strong concentration dose–response with a significant increase in abnormal embryonic development with increasing phosphate concentration. Overall, these results indicate that the gametes and embryos of L. variegatus may provide a rapid and sensitive model bioassay for the evaluation of phosphate pollutants in marine systems. Our findings also indicate that shallow-water populations of L. variegatus spawning in areas subjected to inorganic and organic phosphate pollutants may suffer detrimental effects on fertilization and embryonic development.

Effects of inorganic and organic phosphates on feeding, feeding absorption, nutrient allocation, growth and righting responses of the sea urchin Lytechinus variegatus

The sea urchin Lytechinus variegatus is capable of surviving chronic exposure to sodium phosphate (inorganic phosphate) concentrations as high as 3.2 mg l−1, and triethyl phosphate (organic phosphate) concentrations of 1,000 mg l−1. However, chronic exposure to low (0.8 mg l−1 inorganic and 10 mg l−1 organic phosphate), medium (1.6 mg l−1 inorganic and 100 mg l−1 organic phosphate) or high (3.2 mg l−1 inorganic and 1,000 mg l−1 organic phosphate) sublethal concentrations of these phosphates inhibits feeding, fecal production, nutrient absorption and allocation, growth and righting behavior. Food consumption and fecal production declined significantly in individuals exposed to medium and high concentrations of inorganic phosphates and all levels of organic phosphates. Feeding absorption efficiencies for total organics and carbohydrates decreased significantly in individuals held in the highest concentration of organic phosphate. Feeding absorption efficiencies for lipids were significantly reduced in the highest inorganic phosphate concentration only, while they decreased significantly for protein with increasing phosphate exposure. Carbohydrate and lipid levels in gonad and gut tissues decreased significantly with exposure to increasing phosphate concentrations, potentially impairing both gametogenesis and nutrient storage in the gut. Moreover, gonad indices significantly decreased in individuals exposed to the highest concentrations of either phosphate. Growth rates decreased significantly under the influence of all phosphate concentrations, while increasing in seawater alone. Individuals exposed to increasing phosphate concentrations showed reduced righting responses (a measure of stress) and no acclimation in righting times during chronic exposure to phosphates over a 4 week period. These findings indicate that shallow-water populations of L. variegatus subjected to inorganic and organic phosphate pollutants will exhibit stress and be inhibited in their growth and performance due to reductions in feeding, nutrient absorption and allocation of nutrients to key somatic and reproductive tissues.