The effect of subchronic metribuzin exposure to signal crayfish (Pacifastacus leniusculus Dana 1852)

OBJECTIVES

The aim of the study was to investigate effects of the triazine herbicide metribuzin on signal crayfish Pacifastacus leniusculus Dana by determining oxidative stress (thiobarbituric acid reactive substances) and antioxidant indices (total superoxide dismutase, catalase, glutathione reductase) in hepatopancreas, muscle, and gill as well as assessing their histopathology.

DESIGN

Crayfish were exposed to metribuzin concentrations of 0.52 μg x l(-1) (realistic environmental concentration) and 3.06 mg x l(-1) (10% 96hLC50) for 10 and 30 days followed by a 30-day depuration period without exposure to metribuzin.

RESULTS

In the thiobarbituric acid reactive substances, superoxide dismutase, and catalase were observed differences in all examined tissues compared to the control group. Differences from control were observed in glutathione reductase activity in hepatopancreas after 10 days for both exposure concentrations and after 30 days at 3.06 mg x l(-1). Histological examination revealed extensive focal autolytic disintegration of tubular epithelium in hepatopancreas of crayfish exposed to metribuzin for 30 days.

CONCLUSIONS

Chronic exposure of metribuzin resulted in oxidative damage to cell lipids, in changes of antioxidant activity in crayfish tissue, and pathological changes in hepatopancreas. The results suggest that selected oxidative stress biomarkers, antioxidant enzymes, and pathologies of hepatopancreas may have potential as biomarkers for monitoring residual triazine herbicides in the aquatic environment.

A histopathological study of Hudson River crayfish, Orconectes virilis, exposed to platinum group metals

Platinum group metals (PGMs), such as platinum (Pt), palladium (Pd), and rhodium (Rh), are of increasing concern due to rising anthropogenic input to aquatic systems. In this study, PGMs' effects on bioaccumulation and histopathological changes were investigated using Orconectes virilis, a native Hudson River crayfish, as a model. Organisms were exposed to varying concentrations of water-soluble PGM salts for 10 days. The following experimental treatments were established: 0.0, 1.0, 5.0, 10.0 ppm Pt(IV), 1.0 ppm Rh(III), 1.0 ppm Pd(II), and a PGM mix (1.0 ppm Pt(IV), Rh(III), Pd(II) each) dissolved in raw Hudson River water. Metal content in the tissue samples were analyzed by a Spectro Genesis ICP-OES. The relationship between Pt, Pd, and Rh concentrations in different treatments and observed behavioral changes during the experiment was analyzed through One-Way ANOVA Student-Newman-Keuls multiple comparison test (P ≤ 0.05). Paraffin sections, 6-μm-thick, were prepared in standard eosin-Y and hematoxylin-2 stain and examined for histological abnormalities within hepatopancreas, exoskeleton, brain, and ganglia tissue. Statistically significant differences in PGM bioaccumulation were observed in all organs, with highest concentrations found in the hepatopancreas, 81.68 mg g(-1) dw in 1.0 ppm Pd treatment, 20.03 mg g(-1) dw Rh in 1.0 ppm Rh treatment, and 81.58 mg g(-1) dw Pt in the 5.0 ppm Pt treatment. Pt bioaccumulation in the hepatopancreas and exoskeleton decreased at the highest Pt exposure treatment, suggesting severe structural damage to tissue. Hyper-segmentation of vacuoles and swelling of the vascular channels were observed in the hepatocyte structure of the hepatopancreas. Exoskeleton exhibited visible bands in the exocuticle indicating demineralization. Brain and ganglia demonstrated extensive vacuolization. Behavioral analysis showed an increase of maximum response intensity over the experimental period within each treatment. Bioaccumulation and cellular abnormalities observed in exposed aquatic organisms raise concern of PGM bio-magnification within the food chain and its effect on the environment and human health.

Aminergic control of social status in crayfish agonistic encounters

Using pairings of male crayfish Procambarus clarkii with a 3–7% difference in size, we confirmed that physically larger crayfish were more likely to win encounters (winning probability of over 80%). Despite a physical disadvantage, small winners of the first pairings were more likely to win their subsequent conflicts with larger naive animals (winning probability was about 70%). By contrast, the losers of the first pairings rarely won their subsequent conflicts with smaller naive animals (winning probability of 6%). These winner and loser effects were mimicked by injection of serotonin and octopamine. Serotonin-injected naive small crayfish were more likely to win in pairings with untreated larger naive crayfish (winning probability of over 60%), while octopamine-injected naive large animals were beaten by untreated smaller naive animals (winning probability of 20%). Furthermore, the winner effects of dominant crayfish were cancelled by the injection of mianserin, an antagonist of serotonin receptors and were reinforced by the injection of fluoxetin, serotonin reuptake inhibitor, just after the establishment of social order of the first pairings. Injection of octopamine channel blockers, phentolamine and epinastine, by contrast, cancelled the loser effects. These results strongly suggested that serotonin and octopamine were responsible for winner and loser effects, respectively.

Functional characterization on invertebrate and vertebrate tissues of tachykinin peptides from octopus venoms

It has been previously shown that octopus venoms contain novel tachykinin peptides that despite being isolated from an invertebrate, contain the motifs characteristic of vertebrate tachykinin peptides rather than being more like conventional invertebrate tachykinin peptides. Therefore, in this study we examined the effect of three variants of octopus venom tachykinin peptides on invertebrate and vertebrate tissues. While there were differential potencies between the three peptides, their relative effects were uniquely consistent between invertebrate and vertebrae tissue assays. The most potent form (OCT-TK-III) was not only the most anionically charged but also was the most structurally stable. These results not only reveal that the interaction of tachykinin peptides is more complex than previous structure-function theories envisioned, but also reinforce the fundamental premise that animal venoms are rich resources of novel bioactive molecules, which are useful investigational ligands and some of which may be useful as lead compounds for drug design and development.

Effects of selenium supplemented diets on growth and condition indexes in juvenile red swamp crayfish, Procambarus clarkii

Effects of selenium diets (Se, 0.3 and 1.2mgkg(-1)) on juvenile red swamp crayfish Procambarus clarkii were observed for eight weeks. Growth, condition factors and Se levels in exoskeleton and hepatopancreas for both sexes and diets were evaluated at three endpoints. The specific growth rate (SGR) showed a faster, but not statistically significant growth in Se exposed specimens. Se levels were higher in exoskeleton and hepatopancreas of both Se exposed males and females, when compared to controls. The abdomen-total weight relationship (Tw/B) showed no significant differences between Se exposed and control groups. A constant decline of HI values was recorded in both Se exposed sexes and the same trend was observed in control males. Se exposed females evidenced lower HI after 4 and 8 weeks when compared to controls. Therefore, evident reductions of the health indicator values HI suggested that selenium can deplete the hepatopancreas energy reserves, mainly in juvenile male crayfish.

Immunological responses of customised probiotics-fed marron, Cherax tenuimanus, (Smith 1912) when challenged with Vibrio mimicus

A two-phased experiment was conducted to investigate the effects of dietary supplementation of customised probiotics on marron physiology. During the first phase marron were fed probiotic supplemented feed for 70 days, while in phase two the same marron were challenged with Vibrio mimicus and their physiological responses were investigated for 4 days post-challenged. The experiment was carried out in a purpose-built room, designed for aquaculture research, using 18 of 250 L cylindrical plastic tanks. Five species of isolated probiotic bacteria from commercial probiotic products and marron's intestine were tested in this experiment. The probiotic bacteria were (Bacillus sp.); A10 (Bacillus mycoides); A12 (Shewanella sp.); PM3 (Bacillus subtilis); and PM4 (Bacillus sp.), which were added to the formulated basal marron diet (34% crude protein, 8% crude lipid, 6% ash) at a concentration of 10(8) cfu/g of feed. Immune responses of marron fed probiotics were evaluated by investigating organosomatic indices, growth rate, survival, intermoult period, total haemocytes counts (THC), proportion of granular cells (GC), bacteraemia, bacteria load in the intestine and water quality. The results showed that dietary supplementation of probiotics in marron had no significant impact on growth, intermoult period and survival of the marron. However, their supplementation improved the physiological condition of marron in terms of significantly higher tail muscle indices, THC and proportion of granular cells (GC) and reduced bacterial load in the haemolymph. The addition of probiotics in marron diets also increased the bacteria load in the marron intestine. In addition, dietary supplementation of the customised probiotics was effective in improving the resistance of marron against V. mimicus as they had higher THC, higher proportion of GC and lower presence of bacteria in their haemolymph, after marron were challenged with V. mimicus. The results also showed that probiotic Bacillus mycoides (A10) and PM4 are the most beneficial dietary probiotics for marron health.

Fluoride bioaccumulation and toxic effects on the survival and behavior of the endangered white-clawed crayfish Austropotamobius pallipes (Lereboullet)

Laboratory experiments were performed to examine the toxic effects of fluoride (F(-)) on the survival and behavior of white-clawed crayfish (Austropotamobius pallipes). Body fluoride contents (bioaccumulation) of test crayfish were also examined. No significant differences between male and female crayfish regarding mortality, escape (tail-flip) response, and fluoride bioaccumulation were detected. For mortality, 48-, 72-, 96-, 120-, 144-, 168-, and 192-h median lethal concentrations (LC50) were estimated to be 93.0, 55.3, 42.7, 36.5, 32.9, 30.6, and 28.9 mg F(-)/l, respectively. For the escape response, 48-, 72-, 96-, 120-, 144-, 168- and 192-h median effective concentrations (EC50) were estimated to be 18.4, 11.1, 8.6, 7.4, 6.7, 6.2 and 5.9 mg F(-)/l, respectively. Average food consumption in test crayfish tended to decrease with increasing water fluoride concentration with a 192-h lowest-observed effect concentration of 10.7 mg F(-)/l. These results indicate that the escape response was the most sensitive end point to fluoride toxicity followed by food consumption and mortality. Fluoride bioaccumulation in test crayfish increased with increasing water fluoride concentration and exposure time. The exoskeleton accumulated more fluoride than muscle. A comparison of the obtained results with previous data for other freshwater invertebrates shows that white-clawed crayfish are relatively tolerant to fluoride toxicity. We conclude that fluoride pollution in freshwater ecosystems should not be viewed as an important risk factor contributing to the catastrophic decrease of A. pallipes in many European countries. Our results indicate that fluoride bioaccumulation in A. pallipes might be used as a bioindicator of fluoride pollution in freshwater ecosystems where it is present.

Dietary organic selenium improves growth, survival and resistance to Vibrio mimicus in cultured marron, Cherax cainii (Austin, 2002)

To determine the effects of dietary organic selenium (OS) supplementation on the growth performance and immune competence of marron, Cherax cainii (Austin, 2002), a group of marron were fed 0.2 g kg(-1) of Sel-Plex(®) supplemented basal diet and then compared with another group (control) of marron fed basal diet without any supplementation. After 90 days of feeding, final weight, average weekly gains (AWG), relative gain rate (RGR), specific growth rate (SGR), survival, total and differential haemocyte counts (THC and DHC), were compared between the two groups. Surviving marron from each group were then divided into three sub-groups (three tanks per sub-group with seven marron per tank); (1) first sub-group was injected with 20 μL of 3.24 × 10(6) cfu Vibrio mimicus; (2) the second sub-group was injected with 20 μL normal saline and (3) the third sub-group was not subjected to injection and became the control group. THC, DHC, neutral red retention time (NRRT) and Vibrio ranks of post-injected marron were evaluated for 96 h, at every 24-h interval. The results showed that after 90 days of feeding, final weight, AWG, RGR, SGR, survival, THC, proportion of hyaline cells of OS-fed marron were significantly higher (P < 0.05) than the control group, whereas proportion of granular and semigranular cells were not affected by dietary OS. After challenging with V. mimicus, survival rate of marron without dietary OS significantly decreased (P < 0.05) as compared to the control group of marron. THC of marron in all sub-groups were significantly reduced (P < 0.05) after the challenge. However, THC and granular cells of sub-groups fed OS were higher than other sub-groups. Vibrio ranks and NRRT of marron fed OS were significantly lower and slower, respectively, than marron fed without OS. These findings demonstrated the benefits of OS inclusion in the marron diet in terms of growth, health and disease resistance.

Effects of historical lead-zinc mining on riffle-dwelling benthic fish and crayfish in the Big River of southeastern Missouri, USA

The Big River (BGR) drains much of the Old Lead Belt mining district (OLB) in southeastern Missouri, USA, which was historically among the largest producers of lead-zinc (Pb-Zn) ore in the world. We sampled benthic fish and crayfish in riffle habitats at eight sites in the BGR and conducted 56-day in situ exposures to the woodland crayfish (Orconectes hylas) and golden crayfish (Orconectes luteus) in cages at four sites affected to differing degrees by mining. Densities of fish and crayfish, physical habitat and water quality, and the survival and growth of caged crayfish were examined at sites with no known upstream mining activities (i.e., reference sites) and at sites downstream of mining areas (i.e., mining and downstream sites). Lead, zinc, and cadmium were analyzed in surface and pore water, sediment, detritus, fish, crayfish, and other benthic macro-invertebrates. Metals concentrations in all materials analyzed were greater at mining and downstream sites than at reference sites. Ten species of fish and four species of crayfish were collected. Fish and crayfish densities were significantly greater at reference than mining or downstream sites, and densities were greater at downstream than mining sites. Survival of caged crayfish was significantly lower at mining sites than reference sites; downstream sites were not tested. Chronic toxic-unit scores and sediment probable effects quotients indicated significant risk of toxicity to fish and crayfish, and metals concentrations in crayfish were sufficiently high to represent a risk to wildlife at mining and downstream sites. Collectively, the results provided direct evidence that metals associated with historical mining activities in the OLB continue to affect aquatic life in the BGR.

Acute toxicity of triazine pesticides to juvenile signal crayfish (Pacifastacus leniusculus)

OBJECTIVES

Crustacea are at high risk of toxic effects of agricultural pesticides. Currently, many questions regarding the toxicity of triazine herbicides to crayfish remain unresolved. The aim of this research was to evaluate the acute toxicity of atrazine, hexazinone, metribuzine, prometryne, simazine, and terbutryne to juvenile signal crayfish (Pacifastacus leniusculus).

DESIGN

Acute toxicity tests were performed in accordance with standardized guidelines for testing of chemicals, OECD no. 203, using a semistatic test system. Signal crayfish juveniles (n=672) of 49.0-81.5 mg weight and 12.8-16.0 mm total length were used for the bioassay. Mortalities were recorded daily to 96 h. Each pesticide was tested at concentrations of 1, 10, 40, 70, and 100 mg.l-1. Percent mortalities were analyzed by linear regression, and median lethal concentration (LC50) values were computed using probit analysis EKO-TOX 5.2 software.

RESULTS

96hLC50 values for juvenile signal crayfish were 12.1 mg.l-1 for atrazine, 13.9 mg.l-1 for terbutryne, 14.4 mg.l-1 for prometryne, 19.5 mg.l-1 for hexazinone, 30.6 mg.l-1 for metribuzine, and 77.9 mg.l-1 for simazine. Atrazine showed the greatest toxicity to signal crayfish.

CONCLUSIONS

The present study demonstrated that triazines are toxic to signal crayfish. Signal crayfish is more sensitive than the fish for atrazine, hexazine, metribuzine, and for these triazines signal crayfish can be used as a bio-indicator of environmental contamination.

[Effects of Cd2+ on antioxidant system in hepatopancreas of Procambarus clarkii]

By the method of toxicity bioassay, this paper studied the effects of different concentration (1.72, 3.44, 6.89, 13.77, and 27.55 mg x L(-1)) Cd2+ on the activities of antioxidative enzymes (SOD, CAT, and GSH-PX) and the antioxidation substances (GSH and Vc) in hepatopancreas of freshwater crayfish Procambarus clarkii. The results showed that the SOD activity was induced at the lowest concentration (1.72 mg x L(-1)) Cd2+ but inhibited at all other test concentrations Cd2+, and the inhibition degree was positively correlated with the Cd2+ concentration. Under all test concentrations Cd2+, the CAT activity decreased after an initial increase, with a peak 3 days after exposure. The CAT activity was sensitive to lower concentrations (< or = 6.89 mg x L(-1)) Cd2+, but had no significant difference at higher concentrations (>6.89 mg x L(-1)) Cd2+. When the Cd2+ concentration was < or = 6.89 mg x L(-1), the GSH-PX activity showed a trend of increasing first and then decreased; when the Cd2+ concentration was 13.77 or 27.55 mg x L(-1), the GSH-PX activity was depressed during the first day of exposure. When the Cd2+ concentration was < or = 6.89 mg x L(-1), the GSH content reached the highest value on the first day of exposure, and maintained at a higher level than the control group. However, when the Cd2+ concentration was > or = 13.77 mg x L(-1), the GSH content had no significant difference with the control. The Vc content was very sensitive to all test concentrations Cd2+. It decreased significantly on the first day of exposure, with the decrement positively correlated to Cd2+ concentration, but showed a recovering trend with exposure time. The results indicated that both the antioxidative enzymes and the antioxidation substances in the hepatopancreas of P. clarkii played important roles in coping with Cd2+ stress, and in most cases, showed a time- and dose-dependent relationship with Cd2+ concentration. The GSH-PX activity and Vc content of P. clarkii could be used as the potential bio-indicators in evaluating Cd2+ contamination.

Use of natural pyrethrum to control the red swamp crayfish Procambarus clarkii in a rural district of Italy

BACKGROUND

The crayfish Procambarus clarkii inflicts severe ecological and economic damages in Europe. To develop an efficient method for its control, four experiments were carried out to assess the impact of natural pyrethrum (i.e. Pyblast) on crayfish: (1) the 24 h LC(100) and LC(50) were quantified on crayfish; (2) the breakdown time of the 24 h LC(100) was assessed using Daphnia magna as a bioindicator; the effects of 24 h LC(100) on crayfish were investigated by applying the biocide into burrows (3) and in a drainage channel (4).

RESULTS

Pyblast concentrations of 0.05 and 0.02 mg L(-1) corresponded to 24 h LC(100) and LC(50) respectively. The concentration of 0.05 mg L(-1) broke down after 72 h, whereas 0.02 mg L(-1) did not cause any significant mortality in D. magna after 24 h. However, 0.05 mg L(-1) had no effect on crayfish when introduced into the burrows, but led to a mortality of 95% when applied in the water.

CONCLUSION

Experimental evidence is provided for the efficacy of Pyblast to control invasive crayfish. Obviously, before its use on a large scale, further studies are needed to find a concentration that will achieve the target 100% mortality with the shortest recovery time of the environment.

Genotoxicity monitoring of freshwater environments using caged crayfish (Astacus leptodactylus)

Genotoxicity of freshwater pollution was assessed by measuring DNA damage in haemocytes of caged freshwater crayfish Astacus leptodactylus by the means of Comet assay and micronucleus test, integrated with the measurements of physiological (total protein concentration) and immunological (total haemocyte count) haemolymph parameters as biomarkers of undergone stress. Crayfish were collected at the reference site (River Mrežnica) and exposed in cages for 1 week at three polluted sites along the Sava River (Zagreb, Sisak, Krapje). The long term pollution status of these locations was confirmed by chemical analyses of sediments. Statistically significant increase in DNA damage measured by the Comet assay was observed at all three polluted sites comparing to the crayfish from reference site. In addition, native crayfish from the mildly polluted site (Krapje) cage-exposed on another polluted site (Zagreb) showed lower DNA damage than crayfish from the reference site exposed at the same location indicating adaptation and acclimatisation of crayfish to lower levels of pollution. Micronuclei induction showed similar gradient of DNA damage as Comet assay, but did not reach the statistical significance. Observed increase in total haemocyte count and total protein content in crayfish from polluted environments in the Sava River also confirmed stress caused by exposure to pollution. The results of this study have proved the applicability of caging exposure of freshwater crayfish A. leptodactylus in environmental genotoxicity monitoring using Comet assay and micronucleus test.

Novel protocol for the chemical synthesis of crustacean hyperglycemic hormone analogues--an efficient experimental tool for studying their functions

The crustacean Hyperglycemic Hormone (cHH) is present in many decapods in different isoforms, whose specific biological functions are still poorly understood. Here we report on the first chemical synthesis of three distinct isoforms of the cHH of Astacus leptodactylus carried out by solid phase peptide synthesis coupled to native chemical ligation. The synthetic 72 amino acid long peptide amides, containing L- or D-Phe³ and (Glp¹, D-Phe³) were tested for their biological activity by means of homologous in vivo bioassays. The hyperglycemic activity of the D-isoforms was significantly higher than that of the L-isoform, while the presence of the N-terminal Glp residue had no influence on the peptide activity. The results show that the presence of D-Phe³ modifies the cHH functionality, contributing to the diversification of the hormone pool.

Effects of uranium uptake on transcriptional responses, histological structures and survival rate of the crayfish Procambarus clarkii

This work aims to investigate the accumulation levels and effects (transcriptional responses, histopathology and survival rate) associated with a wide range of dissolved uranium (U) concentrations (0, 0.03, 0.6, 4 and 8 mg/L of U) on adult male crayfish Procambarus clarkii during 4 (T4) and 10 (T10) days of exposure. The follow-up of the crayfish mortality showed that P. clarkii was highly resistant to U. Increasing waterborne U concentrations led to increasing bioaccumulation in key crayfish organs and increasing histological damages. U distribution in tissues was also evaluated using transmission electron microscopy and showed the presence of a detoxified form of U in the gill's epithelium in the shape of flakes. Expression levels of mitochondrial genes (cox1, atp6 and 12S gene) and genes involved in oxidative stress (sod(Mn) and mt) were examined together with the housekeeping gene 18S. atp6 and mt genes of P. clarkii were cloned and sequenced before analysis. Significant correlations were observed between U bioaccumulation and the down-regulation of both cox1 and sod(Mn) genes. This work provides a first U toxicogenomic and histopathological pattern of P. clarkii, identify U biomarkers and associate gene expression endpoints to accumulation levels. It also provides new insights into the mechanisms involved in U stress.

Accumulation and toxicity of aluminium-contaminated food in the freshwater crayfish, Pacifastacus leniusculus

The accumulation and toxicity of aluminium in freshwater organisms have primarily been examined following aqueous exposure. This study investigated the uptake, excretion and toxicity of aluminium when presented as aluminium-contaminated food. Adult Pacifastacus leniusculus were fed control (3 μg aluminium/g) or aluminium-spiked pellets (420 μg aluminium/g) over 28 days. Half the crayfish in each group were then killed and the remainder fed control pellets for a further 10 days (clearance period). Concentrations of aluminium plus the essential metals calcium, copper, potassium and sodium were measured in the gill, hepatopancreas, flexor muscle, antennal gland (kidney) and haemolymph. Histopathological analysis of tissue damage and sub-cellular distribution of aluminium were examined in the hepatopancreas. Haemocyte number and protein concentration in the haemolymph were analysed as indicators of toxicity. The hepatopancreas of aluminium-fed crayfish contained significantly more aluminium than controls on days 28 and 38, and this amount was positively correlated with the amount ingested. More than 50% of the aluminium in the hepatopancreas of aluminium-fed crayfish was located in sub-cellular fractions thought to be involved in metal detoxification. Aluminium concentrations were also high in the antennal glands of aluminium-fed crayfish suggesting that some of the aluminium lost from the hepatopancreas is excreted. Aluminium exposure via contaminated food caused inflammation in the hepatopancreas but did not affect the number of circulating haemocytes, haemolymph ion concentrations or protein levels. In conclusion, crayfish accumulate, store and excrete aluminium from contaminated food with only localised toxicity.

Necrophagy by a benthic omnivore influences biomagnification of methylmercury in fish

Omnivory has an important role in the movement of energy, nutrients, and contaminants between benthic and pelagic food webs. While top-predator fish are known to supplement a mostly piscivorous diet with benthic organisms, a more obscure benthic-pelagic coupling occurs when benthic invertebrates forage on fish carcasses, referred to as necrophagy. The combination of these two benthic-pelagic links, top-predator fish feeding on benthic organisms that have fed on dead fish, can generate a trophic feedback cycle that conserves energy and nutrients and may have implications for biomagnification of methylmercury (MeHg) in fish. We investigated the role of necrophagy by crayfish (Procambarus clarkii), via a trophic feedback cycle, on the biomagnification of MeHg in largemouth bass (Micropterus salmoides), a cosmopolitan top predator fish known to feed on crayfish. Controlled laboratory tests quantified the uptake of MeHg by both organisms from artificial and natural food (whole crayfish or bass tissue). Assimilation efficiency (AE) of MeHg was greater for bass fed crayfish (79±0.5%) than those fed artificial food (60±3%). Furthermore, AE of MeHg was greatest for largemouth bass fed crayfish that fed on MeHg-dosed dead fish (i.e., trophic feedback cycle; 94±17%). A model, parameterized with results of the laboratory experiments, was used to make steady-state projections of MeHg biomagnification factors. Model projections also indicate that MeHg biomagnification would be greatest for largemouth bass from a trophic feedback cycle. These results suggest that food web ecology has an important role in determining MeHg levels in predatory fish and underscore the need for further investigation into the magnitude that necrophagy may affect MeHg biomagnification in aquatic systems.

Omic approaches in environmental issues

Biomonitoring requires the application of batteries of different biomarkers, as environmental contaminants induce multiple responses in organisms that are not necessarily correlated. Omic technologies were proposed as an alternative to conventional biomarkers since these techniques quantitatively monitor many biological molecules in a high-throughput manner and thus provide a general appraisal of biological responses altered by exposure to contaminants. As the studies using omic technologies increase, it is becoming clear that any single omic approach may not be sufficient to characterize the complexity of ecosystems. This work aims to provide a preliminary working scheme for the use of combined transcriptomic and proteomic methodologies in environmental biomonitoring. There are difficulties in working with nonmodel organisms as bioindicators when combining several omic approaches. As a whole, our results with heterologous microarrays in M. spretus and suppressive subtractive hybridization (SSH) in P. clarkii indicated that animals sustaining a heavy pollution burden exhibited an enhanced immune response and/or cell apoptosis. The proteomic studies, although preliminary, provide a holistic insight regarding the manner by which pollution shifts protein intensity in two-dimensional gel electrophoresis (2-DE), completing the transcriptomic approach. In our study, the sediment element concentration was in agreement with the intensity of protein expression changes in C. maenas crabs. In conclusion, omics are useful technologies in addressing environmental issues and the determination of contamination threats.

Acute toxicity of chlorantraniliprole to non-target crayfish (Procambarus clarkii) associated with rice-crayfish cropping systems

BACKGROUND

Chlorantraniliprole, a novel anthranilic diamide insecticide, was recently introduced into the United States where rice-crayfish crop rotations are practiced to control rice water weevil (Lissorhoptrus oryzophilus Kuschel) infestations. Chlorantraniliprole has high margins of mammalian safety and excellent insecticidal efficacy, but its toxicity to non-target crayfish is uncertain. In this study, the acute toxicity of chlorantraniliprole to the red swamp crayfish Procambarus clarkii Girard was determined using aquatic and feeding assays.

RESULTS

The aquatic 96 h median lethal toxicity (LC(50)) data indicate that technical-grade chlorantraniliprole is highly toxic (US EPA category) to crayfish with an LC(50) of 951 microg L(-1) (95% CL = 741-1118 microg L(-1)). A no observed effect concentration (NOEC) of 480 microg L(-1) was recorded. Neither the 36 day chronic feeding study, where crayfish fed on chlorantraniliprole-treated rice seed in aquaria, nor the 144 h acute feeding test, where crayfish fed on rice seeds treated with chlorantraniliprole, produced mortality or abnormal behavior.

CONCLUSION

Chlorantraniliprole is three orders of magnitude less acutely toxic to P. clarkii than lambda-cyhalothrin and etofenprox, two pyrethroid insecticides also used in rice, and is less likely to cause acute crayfish toxicity in rice pond ecosystems. Based on acute toxicity data, the use of chlorantraniliprole should be more compatible with rice-crayfish crop rotations than pyrethroids.

Effects of dietary beta-1,3-glucan on the growth, survival, physiological and immune response of marron, Cherax tenuimanus (smith, 1912)

Six isonitrogenous and isocalorific diets supplemented with five different levels of beta-1,3-glucan (0.08%, 0.1%, 0.2%, 0.4% and 0.8%) were formulated and tested for marron (Cherax tenuimanus) growth, survival, organosomatic indices, osmoregulatory capacity and immunological parameters (total and differential haemocyte counts, haemolymph clotting time and bacteraemia). The sixth diet without any beta-1,3-glucan was used as a control. Each diet was provided to 18 marron (0.47 +/- 0.02 g initial weight) replicated 3 times in individual 250 L fiberglass cylindrical tanks. Each tank was provided with a biological filtration recirculating water system. After 84 days of culture, the survival and yield were higher in the marron fed 0.1% beta glucan supplemented diet. The different levels of beta glucan did not alter any of the physiological parameters of marron. However, dietary supplementation with beta glucan resulted in significantly higher (P < 0.05) total haemocyte count (THC) and granular cells. The bacteraemia rank was lower in all diets having beta glucan supplemented with more than or equal to 0.1% compared to the control and 0.08% beta glucan supplemented diets. Results suggest that dietary beta-1,3-glucan at a minimum concentration of 0.1-0.2% can improve the immune system of marron.

[Evaluation of functional state of crayfish Pontastacus leptodactylus in normal and toxic environment by characteristics of their cardiac activity and hemolymph biochemical parameters]

The work deals with study of basic characteristics of cardiac activity (HR and stress-index) and hemolymph protein parameters in the crayfish Pontastacus leptodactylus. The main criteria of the crayfish selection are developed for formation of the animal reference groups available for subsequent toxicologic experiments. The action of a model toxicant, hydroquinone (often present in waste water), at a concentration of 1 g/l on parameters of the crayfish cardiac activity at various exposition time, its effect on circadian cardiac activity and on the hemolymph total protein were studied. At its short-term exposure, hydroquinone produced a temporary increase of HR and stress-index, but had no marked effect on the total protein parameters in hemolymph. At long action (for one day), hydroquinone led to a considerable tachycardia, disturbance of the circadian cardioactivity and to a decrease by 40% of the hemolymph total protein. In 50% of cases the toxicant caused death of the animals either in the course of its action or at period of washout from the toxicant. Mechanisms of the toxic action of hydroquinone at various levels of organization are discussed.

Procambarus clarkii as a bioindicator of heavy metal pollution sources in the lower Ebro River and Delta

In the Ebro River basin, point and diffuse pollution of heavy metals stems mainly from industry and agriculture. Bioaccumulation patterns were examined under different pollution sources (point and diffuse) using levels of heavy metals (As, Cd, Cr, Cu, Hg, Pb and Zn) in abdominal muscle tissue of Procambarus clarkii. P. clarkii captured under point source effects presented the highest concentrations of Hg, Pb and As; and were related with distance to the source of industrial waste sediments. Mean Hg levels in crayfish exposed to point sources of metals significantly exceeded legal allowed values established by the European Union legislation. In the Ebro Delta, high levels of As, Cr, Cu and Zn were associated with traditional agriculture activity (diffuse pollution) as well. These results demonstrate the potential of P. clarkii to bioaccumulate heavy metals from both point and diffuse sources and hence potentially transfer these metals to higher trophic levels.

The effects of pollution on the vitamins A, E, C, beta-carotene contents and oxidative stress of the freshwater crayfish, Astacus leptodactylus

In this study, we determined the effects of pollution on levels of antioxidant vitamins (A, E, C), beta-carotene and malondialdehyde (MDA), in the hepatopancreas and muscle tissues of freshwater crayfish (Astacus leptodactylus). The crayfish samples were collected from Aydincik (unpolluted control site) and Ağin (polluted site) in the Keban Dam Lake (Elazig-Turkey) in August 2007. The results showed that the concentrations of vitamins E, C and beta-carotene in both tissues were significantly lower, and MDA levels were higher than in controls. There were no significant alterations in vitamin A levels. In comparison among the sex groups, some values were different significantly between the localities. The comparison of same-sex groups of the different localities also showed that concentrations of the vitamins E, C, beta-carotene and MDA changed statistically according to the tissues between the localities.

Effects of estradiol and progesterone on the reproduction of the freshwater crayfish Cherax albidus

In this study we have investigated the role of 17beta-estradiol and progesterone in the reproduction of the crayfish Cherax albidus by using vitellogenin (VTG) as a biomarker. Early-vitellogenic (EV), full-vitellogenic (FV), and non-vitellogenic (NV) females of Cherax albidus were treated with 17beta-estradiol, progesterone, or both for 4 weeks. Levels of VTG mRNA in the hepatopancreas were detected by RT-PCR. The PCR product was sequenced and showed 97% homology with Cherax quadricarinatus VTG. 17beta-estradiol was more effective than progesterone and 17beta-estradiol plus progesterone in increasing the vitellogenin transcript in the hepatopancreas of EV and FV females. On the contrary, progesterone was more effective than 17beta-estradiol and 17beta-estradiol plus progesterone in increasing the vitellogenin concentration in the hemolymph of EV and FV females. Hepatopancreas histology and fatty acid composition of females injected with hormones showed major modifications. No effects were registered in NV females. In conclusion, 17beta-estradiol and progesterone influence VTG synthesis, although our data indicate that they act through different pathways and are not effective until the proper hormonal environment is established, as demonstrated by their inefficacy in NV females.

Contaminant accumulation and multi-biomarker responses in field collected zebra mussels (Dreissena polymorpha) and crayfish (Procambarus clarkii), to evaluate toxicological effects of industrial hazardous dumps in the Ebro river (NE Spain)

Large amounts of industrial waste containing high concentrations of mercury, cadmium and organochlorine residues were dumped in a reservoir adjacent to a chlorine-alkali plant in the village of Flix(Catalonia, Spain), situated at the shore of the lower Ebro river. Effects of these contaminants to aquatic river invertebrates were assessed by integrating analyses of metals and organochlorine residues in field collected zebra mussels and crayfish with a wide range of biomarkers. Biological responses included levels of metallothioneins, activities of ethoxyresorufin-O-deethylase, oxidative stress biomarkers (glutathione content, enzymatic activities of superoxide dismutase, catalase, glutathione s-transferase, glutathione peroxidise and glutathione reductase), levels of lipid peroxidation and of DNA strand breaks. The results obtained evidenced similar response patterns in mussels and crayfish with increasing toxic stress levels from upper parts of the river towards the meander located immediately downstream from the most polluted site, close to the waste dumps. The aforementioned stress levels could be related with concentrations of mercury, cadmium, hexachlorobenzene, polychlorobiphenyls and dichlorodiphenyltrichloroethanes from 4- to 195-fold greater than local background levels. The response of biomarkers to these pollutant concentrations differences was reflected in high activities and levels of antioxidant enzymes, metallothioneins, lipid peroxidation and DNA strand breaks and decreased levels of glutathione.