Crayfish Tissues Research Articles

Distribution of arsenic and other metals in crayfish tissues (Procambarus clarkii) under different production practices

Louisiana is one of the world's largest producer of crayfish. Arsenic (As) and other metals (Cd, Cu, Pb and Zn) concentrations were determined in crayfish tissues, plant and soil samples collected from Louisiana paddy rice fields, where crayfish/rice rotation farming is a common practice. The samples were collected from November 2013 to April 2014 from three different crayfish farming systems. Concentration of As in rice grain, rice straw, and native vegetation ranged between 0.33 and 0.41, 3.14–4.93, and 3.26–5.89mgkg−1, respectively. The highest As levels in the crayfish external and internal body parts were found in gill (4.04±1.70mgkg−1), followed by hepatopancreas (3.42±1.57mgkg−1), exoskeleton (1.52±0.85mgkg−1), and muscle (1.50±0.69mgkg−1). Positive correlations between As levels in the crayfish muscle and the plant tissue on which they feed were found in all farming systems (r=0.405–0.438). The biomagnification factor (BMF) of As in different tissues varied between 0.29 and 1.08, having gill and hepatopancreas were the highest As accumulation while the lowest biomagnification was observed in crayfish muscle tissues which is a food source for human. The As levels along with other metals in crayfish muscle tissue were in acceptable levels for human consumption under all crayfish/rice rotation practices. Further studies are needed in determining the percentage of organic and inorganic arsenic in crayfish tissue.

Effects of dietary antioxidants on oxidative stress, antioxidant defence and growth of freshwater crayfishAstacus leptodactylus(Eschscholtz, 1823) during the reproductive period in females

In this study, we examined the effects of dietary antioxidant vitamins [vitamin E (Vit E), vitamin C (Vit C) and vitamin A (Vit A)], astaxanthin (AX) and β-carotene (βC) supplementation on oxidative stress [malondialdehyde (MDA)], antioxidant enzyme activities [superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px)] and glutathione (GSH) levels in hepatopancreas, ovarian, muscle, gill tissues and survival rates (SR), live weight gain (LWG), specific growth rate (SGR) of Astacus leptodactylus during ovarian development. The EE, EC, EA, EAX and EβC groups were formed by addingClick here to enter text. Vit E, Vit C, Vit A, AX and βC to the diet respectively. The antioxidants did not have a significant impact on the values of SR, LWG and SGR. After 137 days, the MDA levels in the Control (C) group were statistically higher in the hepatopancreas, ovarian and muscle tissues according negative control (NC), EE, EC, EA, EAX and EβC groups. The SOD activities in ovarian, muscle and gill tissues and GSH levels in ovarian and muscle tissues were lower in the C group compared with the NC group, but GSH-Px activities in hepatopancreas and ovarian tissues and GSH levels in gill tissues were higher. The MDA levels were statistically lower in all tissues of crayfish in experimental groups according to C group. The antioxidant enzyme activities and GSH levels changed according to tissue. The results showed that Vit E and AX should be supplemented in diets to increase the reproductive performance of crayfish, because Vit E and AX were of higher potential as antioxidants than other vitamins and carotenoids in ovarian tissues.

Immunological study of freshwater crayfish nervous tissue for receptors for neurotrophins and ciliary neurotrophic factor

Neurotrophic factors support survival of neural and glial cells under injuring impacts to mammalian nerve tissue. In invertebrates elements of neurotrophic signaling system (receptors and ligands) were not found for a long time, while phenomenology indicates that cytoprotective neuroglial communication involving neurotrophins, probably, occurs. Presence of proteins immunologically similar to receptors of neurotrophic factors—NGF, BDNF and CNTF—in freshwater crayfish nerve tissue was studied in this work. The proteins similar to low affinity neurotrophins receptor p75, as well as similar to ciliary neurotrophic factor receptor CNTFR were found. In the stretch receptor organ of freshwater crayfish immunostaining for p75 receptors was mainly localized in the receptor neurons, whereas immunostaining for CNTFR was most pronounced in certain glial cells.

Oxidative Status Profile in Different Tissues of Parastacus brasiliensis promatensis (Crustacea, Decapoda, Parastacidae) over a Seasonal Cycle.

The objective of this study was to assess annual redox balance by quantifying activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST), as well as measuring lipid peroxidation levels by determination of thiobarbituric acid-reactive substances, in different tissues of male and female crayfish collected from an area little affected by anthropogenic impacts. A total of 37 male and 32 female of Parastacus brasiliensis promatensis were collected over an annual cycle, and gill, muscle, hepatopancreas, and gonad samples were harvested and subjected to the aforementioned analyses via spectrophotometry. Comparison of the annual oxidative status response profile in gill and in hepatopancreas between males and females revealed differences only in SOD activity. In abdominal muscle, this comparison revealed a distinct profile of SOD and GST activity, as well as of lipid peroxidation. SOD activity in gonads of females increased in the summer when compared to autumn; conversely, CAT and GST levels did not differ over the year. During reproduction, a possible increase of the energy requirements led to an increase in lipid peroxidation in all tested tissues, in males and females alike. It was least evident in female gonad tissue, which suggests this tissue type is relatively protected; within this context, one may establish a tissue-specific grading of Lipid Peroxidation intensity in females of the species during the spring: gonads < muscle < gills < hepatopancreas. Our results show that the responses of the defenses analyzed antioxidants, as well as lipid peroxidation levels, were sex and tissue dependent and a clear pattern of seasonal variation.

Comparison of the efficiency and relevancy of reference genes in crayfish tissue samples / Kerevit doku örneklerinde referans genlerin geçerlilik ve etkinliğinin karşılaştırılması

Abstract Objective: Relevancy of the reference genes have not been investigated in crayfish tissue samples. Various genes have been proposed for establishing a reference level to analyze qPCR results obtained in different tissue samples. However, majority of those genes have been investigated solely in mammalian species. There is no report related to the relevancy and the efficiency of those common reference genes in crayfish tissue samples yet. The primary aim of the present work is to compare the expression level of a set of reference genes in various crayfish tissue samples to establish a reliable reference gene for quantitative expression level comparisons. Methods: cDNA copies were synthesized by RT-PCR from equalised total RNA samples of nine different tissue samples. qPCR were performed on cDNA samples by using four different primer pairs specific for β-actin, Peptidylprolyl Isomerase B, Sarcoplasmic Calcium Binding Protein and 18S ribosomal RNA genes. Results: qActin2 amplified gene fragments for β-actin in all samples. Cycle time of the amplification reaction differed substantially between the investigated tissue types. A similar difference was observed between the melting curves of the products. The primer pair PPIB amplified gene fragments for Peptidylprolyl Isomerase B only in heart, muscle and intestine samples but not in the rest of the tissue samples. Further, both amplification and melting curves for heart, muscle and intestine were different. qSCP amplified some gene fragments for Sarcoplasmic Reticulum Binding Protein only in muscle, heart and ganglion samples. The 18S_1 amplified fragments for 18S. Amplification curves the samples superimposed on each other. Melting curves of the products were very similar. Variance of the obtained data was the lowest for 18S ribosomal RNA. Conclusion: In refer to present results; it is conceivable to propose that among all the genes investigated in the present study, expression level of ribosomal 18S RNA is the most homogeneously distributed one within the body parts of the crayfish. Further, it is minimally affected by extreme biological changes such as molting. Thus, 18S Ribosomal RNA would be suggested as a reference gene to be used when investigating tissue specific expression level of a gene in the crayfish.

Heavy metals bioaccumulation in selected tissues of red swamp crayfish: An easy tool for monitoring environmental contamination levels

In this paper we explored the heavy metal bioaccumulation (Cd, Cu, Pb and Zn) in Procambarus clarkii, a crayfish recently suggested as a potential bioindicator for metals pollution in freshwater systems. The present study is focused on crayfishes populations caught in a heavily polluted industrial and in a reference sites (Central Italy), though the results are generalized with a thorough analysis of literature metadata. In agreement with the literature, the hepatopancreas (Hep, detoxification tissues) of the red swamp crayfish showed a higher concentration of heavy metals in comparison to the abdominal muscle (AbM, not detoxification tissues) in the sites under scrutiny. Hep/AbM concentration ratio was dependent on the specific metal investigated and on its sediment contamination level. Specifically we found that Hep/AbM ratio decreases as follows: Cd (11.7)>Cu (5.5)>Pb (3.6)>Zn (1.0) and Pb (4.34)>Cd (3.66)>Zn (1.69)>Cu (0.87) for the industrial and reference sites, respectively. The analysis of our bioaccumulation data as well as of literature metadata allowed to elaborate a specific contamination index (Toxic Contamination Index, TCI), dependent only on the bioaccumulation data of hepatopancreas and abdominal muscle. In the industrial site, TCI expressed values much higher than the unit for Cd and Cu, confirming that these metals were the main contaminants; in contrast for lower levels of heavy metals, as those observed in the reference site for Cu, Zn and Pb, the index provided values below unit. TCI is proposed as a useful and easy tool to assess the toxicity level of contaminated sites by heavy metals in the environmental management.

The nucleic acid-binding protein PcCNBP is transcriptionally regulated during the immune response in red swamp crayfish Procambarus clarkii.

Gene family encoding cellular nucleic acid binding proteins (CNBP) is well conserved among vertebrates; however, there is limited knowledge in lower organisms. In this study, a CNBP homolog from the red swamp crayfish Procambarus clarkii was characterised. The full-length cDNA of PcCNBP was of 1257 bp with a 5'-untranslated region (UTR) of 63 bp and a 3'-UTR of 331 bp with a poly (A) tail, and an open-reading frame (ORF) of 864 bp encoding a polypeptide of 287 amino acids with the predicted molecular weight of about 33 kDa. The predicted protein possesses 7 tandem repeats of 14 amino acids containing the CCHC zinc finger consensus sequence, two RGG-rich single-stranded RNA-binding domain and a nuclear localization signal, strongly suggesting that PcCNBP was a homolog of vertebrate CNBP. The PcCNBP transcript was constitutively expressed in all tested tissues of unchallenged crayfish, including hepatopancreas, gill, eyestalk, haemocytes, intestine, stomach and cuticle with highest expression in haemocytes, intestine, gills and hepatopancreas. The mRNA expression of PcCNBP in haemocytes was modulated at transcriptional level by different immune challenges, suggesting its involvement in the immune response of P. clarkii during both bacteria and viruses infection.

Passive samplers accurately predict PAH levels in resident crayfish

Contamination of resident aquatic organisms is a major concern for environmental risk assessors. However, collecting organisms to estimate risk is often prohibitively time and resource-intensive. Passive sampling accurately estimates resident organism contamination, and it saves time and resources. This study used low density polyethylene (LDPE) passive water samplers to predict polycyclic aromatic hydrocarbon (PAH) levels in signal crayfish, Pacifastacus leniusculus. Resident crayfish were collected at 5 sites within and outside of the Portland Harbor Superfund Megasite (PHSM) in the Willamette River in Portland, Oregon. LDPE deployment was spatially and temporally paired with crayfish collection. Crayfish visceral and tail tissue, as well as water-deployed LDPE, were extracted and analyzed for 62 PAHs using GC–MS/MS. Freely-dissolved concentrations (Cfree) of PAHs in water were calculated from concentrations in LDPE. Carcinogenic risks were estimated for all crayfish tissues, using benzo[a]pyrene equivalent concentrations (BaPeq). ∑PAH were 5–20 times higher in viscera than in tails, and ∑BaPeq were 6–70 times higher in viscera than in tails. Eating only tail tissue of crayfish would therefore significantly reduce carcinogenic risk compared to also eating viscera. Additionally, PAH levels in crayfish were compared to levels in crayfish collected 10years earlier. PAH levels in crayfish were higher upriver of the PHSM and unchanged within the PHSM after the 10-year period. Finally, a linear regression model predicted levels of 34 PAHs in crayfish viscera with an associated R-squared value of 0.52 (and a correlation coefficient of 0.72), using only the Cfree PAHs in water. On average, the model predicted PAH concentrations in crayfish tissue within a factor of 2.4±1.8 of measured concentrations. This affirms that passive water sampling accurately estimates PAH contamination in crayfish. Furthermore, the strong predictive ability of this simple model suggests that it could be easily adapted to predict contamination in other shellfish of concern.

Trace element concentrations in red swamp crayfish (Procambarus clarkii) and surface sediments in Lake Preola and Gorghi Tondi natural reserve, SW Sicily.

Concentrations of trace elements (Cd, Pb, As, V, Cr, Ni, Cu and Zn) were determined in superficial sediments and in muscle and hepatopancreas tissues of the red swamp crayfish Procambarus clarkii from Lake Preola and Gorghi Tondi Natural Reserve (SW Sicily). In particular, hepatopancreas showed a decidedly higher content of all analysed trace elements with respect to muscles (two- to threefold higher for Cd, Cu, As, Zn and V; four- to fivefold higher for Pb and Cr and seven times higher for Ni). However, no statistically reliable differential accumulation pattern emerged with regard to length and weight for trace elements (except for Cd for which significant positive correlations with length were recorded). Trace element concentrations found in crayfish tissues were in the range considered harmful to human health (except for Cd and Cr). Moreover, the As and Pb concentrations, either in sediment or crayfish tissues, are clearly related to intense agricultural activities, with extensive use of fertilizers and pesticides, that significantly affect the levels of these toxic metals in the study area.

Growth, Survival and Fatty Acid Composition of Freshwater Crayfish (Astacus leptodactylus) Juveniles Fed Enriched Daphnia magna as an Alternative to Artemia

This experiment was conducted to investigate the effects Daphnia magna enriched with lipid emulsions as an alternative to Artemia, on growth, survival rate, and fatty acid composition of freshwater crayfish (Astacus leptodactylus Esch. 1823). The four treatment groups were (a) unenriched Artemia (UEA), (b) unenriched D. magna (UED), (c) D. magna enriched with redpepper emulsion (DER), and (d) D. magna enriched with anchovy oil emulsion (DEA). All tests were carried out in triplicate for 30 days. The crayfish (mean weight 0.12g) were fed ad libitum once daily. At the end of experiment, the highest eicosapentaenoic acid, 20:5n-3 (EPA) level was found in the DEA group (5.77%). The highest DHA (docosahexaenoic acid, 22:6n-3) level was found in the DER group (2.73%) which was statistically similar to the DEA group. In addition, high n-3 HUFA (high unsaturated fatty acid) levels were detected in enriched D. magna groups with emulsions. However, high EPA levels in enriched D. magna groups with emulsions were not reflected in crayfish tissues, but DHA level was reflected in crayfish tissues fed with anchovy oil emulsion. The crayfish fed with D. magna showed similar growth to that of the Artemia fed groups. The growth of the enriched D. magna groups did not differ.

Growth performance of Noble Crayfish Astacus astacus in recirculating aquaculture systems

There is growing interest in using recirculating aquaculture systems (RAS) to raise noble crayfish Astacus astacus a valuable and once plentiful food species in Europe, now a highly endangered species. The growth and survival of A. astacus was compared in growth trials in RAS and open-pond systems (OPS) over a period of 2 months. Energy and lipid content of available diets and crayfish tissue were also determined. Growth of A. astacus during summer was significantly (p < 0.01, one sample t test) higher in OPS (SGR 1.23) than in RAS even at the highest feeding ration provided at 5 % bw/d−1 (RAS HI SGR 0.78 ± 0.06). OPS crayfish also had significantly (p < 0.01 OPS vs. all RAS treatments; Pairwise Wilcoxon) higher lipid content (8.51 %) than RAS crayfish (RAS HI 5.73 %, RAS MED 6.93 %, RAS LOW 5.92 %). Survival rates in RAS were, however, 100 % compared with previous observations in OPS of approx. 70 %. While results showed OPS growth exceeds than that in RAS in the short term, RAS survival rates and annualized growth performance may outweigh this disadvantage, particularly if optimal artificial diets for RAS holding are provided. Feed and crayfish analysis indicated that culturing A. astacus in RAS require a diet protein content exceeding 30 % and lipid content of <13 %, indicating that the carp diet supplied was not optimal. RAS culture allows this valuable species to be cultured in controlled, disease-free enclosed systems—resulting in high-value food products as well as high-quality seedlings for restocking purpose.

Biochemical response of crayfish Astacus leptodactylus exposed to textile wastewater treated by indigenous white rot fungus Coriolus versicolor.

The discharge of textile effluents into the environment without appropriate treatment poses a serious threat for the aquatic organisms. The present study was undertaken to investigate biochemical response of crayfish Astacus leptodactylus exposed to textile wastewater (TW) treated by indigenous white rot fungus Coriolus versicolor. Glutathione S-transferase (GST), cytochrome P450 1A1 (CYP1A1), and acetylcholinesterase (AchE) levels in hepatopancreas and abdomen tissues of crayfish exposed to untreated, treated, and diluted rates (1/10) in both TW during 24 and 96 h were tested. Physiochemical parameters (electrical conductivity (EC), chemical oxygen demand (COD), pH, and total dissolved solid (TDS)) of TW were determined before and after treatment. Physiochemical parameters of TW decreased after treatment. The GST activity and AchE were generally increased, but CYP1A1 activity was decreased in hepatopancreas tissue of crayfish exposed to different kinds of untreated TW. After treatment by indigenous white rot fungus (C. versicolor), GST and CYP1A1 activities were returned to control values, while AchE activities were increasing further. In this study, only GST and CYP1A1 activities of A. leptodactylus confirmed the efficiency of TW treatment with C. versicolor.

Direct visualization of the novel pathogen, Spiroplasma eriocheiris, in the freshwater crayfish Procambarus clarkii (Girard) using fluorescence in situ hybridization.

Spiroplasma eriocheiris is the first spiroplasma strain known to be pathogenic to freshwater crustaceans. It has caused considerable economic losses both in the freshwater crayfish Procambarus clarkii (Girard) and in some other crustaceans. The monitoring of the pathogen in crustacean populations and study of its behaviour in the laboratory require the development of reliable diagnostic tools. In this article, we improved microscopic identification of S.eriocheiris by combining in situ hybridization with specific fluorescently labelled oligonucleotide probes. The established fluorescence in situ hybridization (FISH) allowed simultaneous visualization, identification and localization of S.eriocheiris in the tissues of diseased crayfish P.clarkii and exhibited low background autofluorescence and ideal signal-to-noise ratio. With the advantages of better tissue penetration, potentially more specific and stable, we designed three species-specific oligonucleotide probes utilizing the sequences of 16S-23S rRNA intergenic spacer regions (ISRs) of S.eriocheiris. Positive hybridization signals were visualized in haemocytes and connective tissues of hepatopancreas, cardiac muscle and gill from diseased crayfish. This unique distribution pattern matched the pathological changes when diagnosed by H&E staining and indicated that S.eriocheiris probably spread throughout the tissues in P.clarkii by hemokinesis. This assay will facilitate our understanding of the pathogenesis of S.eriocheiris and enhance the early diagnosis of the novel pathogen.

Do trace element differences in diabetic patients persist with time? The HUNT3 survey

enzymes SOD, CAT, and GR were observed in all tested concentrations to prometryne for each exposure period (P<0.01) as compared with the control group. We did not see any differences in histopathological examination to hepatopancreas. Prolonged exposure of prometryne did not result in oxidative damage to cell lipids and proteins, but it led to changes in antioxidant activity in crayfish tissues. Changes in antioxidant systems were also observed in the environmental prometryne concentration of 0.51 g L−1. The results suggest that antioxidant responses may have potential as biomarkers for monitoring residual triazine herbicides in aquatic environments.

Molecular detection and genotyping of Aphanomyces astaci directly from preserved crayfish samples uncovers the Norwegian crayfish plague disease history

Aphanomyces astaci causes crayfish plague in European freshwater crayfish, but most historical epizootics lack agent isolation and identification. Although declared as crayfish plague outbreaks by the Norwegian Competent Authorities, only presumptive diagnoses without agent isolation exist from Norwegian epizootics until 2005. Molecular methods now allow both A. astaci detection and genotype determination from preserved samples. We therefore aimed to (1) investigate molecularly if A. astaci was involved in a selection of mass-mortality events in Norwegian noble crayfish populations from 1971 to 2004, and (2) determine the eventually involved A. astaci genotype groups both from these historical and also more recent mass-mortality events. DNA was extracted directly from presumptively infected crayfish tissues, and screened by A. astaci specific qPCR. A representative selection of positive samples was confirmed by ITS-sequencing. Finally, genotype determination was performed with microsatellite markers that distinguish all known A. astaci genotype groups. The molecular examination detected A. astaci in crayfish materials from all examined mass-mortality events. The first event in 1971–1974 was caused by the A. astaci genotype group A, presumably the first genotype group that entered Europe more than 150 years ago. All later outbreaks were caused by the A. astaci genotype group B which was introduced to Europe by importation of signal crayfish in the 1960s. The results suggest that molecular methods can verify the involvement of A. astaci in the vast majority of observed crayfish mass mortalities in Europe whenever preserved materials exist. Moreover, microsatellite genotyping can reveal at least parts of the underlying epidemiology.

Predicting polycyclic aromatic hydrocarbon concentrations in resident aquatic organisms using passive samplers and partial least-squares calibration.

The current work sought to develop predictive models between time-weighted average polycyclic aromatic hydrocarbon (PAH) concentrations in the freely dissolved phase and those present in resident aquatic organisms. We deployed semipermeable membrane passive sampling devices (SPMDs) and collected resident crayfish (Pacifastacus leniusculus) at nine locations within and outside of the Portland Harbor Superfund Mega-site in Portland, OR. Study results show that crayfish and aqueous phase samples collected within the Mega-site had PAH profiles enriched in high molecular weight PAHs and that freely dissolved PAH profiles tended to be more populated by low molecular weight PAHs compared to crayfish tissues. Results also show that of several modeling approaches, a two-factor partial least-squares (PLS) calibration model using detection limit substitution provided the best predictive power for estimating PAH concentrations in crayfish, where the model explained ≥72% of the variation in the data set and provided predictions within ∼3× of measured values. Importantly, PLS calibration provided a means to estimate PAH concentrations in tissues when concentrations were below detection in the freely dissolved phase. The impact of measurements below detection limits is discussed.

Microsatellite markers for direct genotyping of the crayfish plague pathogen Aphanomyces astaci (Oomycetes) from infected host tissues

Aphanomyces astaci is an invasive pathogenic oomycete responsible for the crayfish plague, a disease that has devastated European freshwater crayfish. So far, five genotype groups of this pathogen have been identified by applying random amplified polymorphic DNA analysis on axenic cultures. To allow genotyping of A. astaci in host tissue samples, we have developed co-dominant microsatellite markers for this pathogen, tested them on pure cultures of all genotype groups, and subsequently evaluated their use on tissues of (1) natural A. astaci carriers, i.e., North American crayfish species, and (2) A. astaci-infected indigenous European species from crayfish plague outbreaks. Out of over 200 potential loci containing simple sequence repeat (SSR) motifs identified by 454 pyrosequencing of SSR-enriched library, we tested 25 loci with highest number of repeats, and finally selected nine that allow unambiguous separation of all known RAPD-defined genotype groups of A. astaci from axenic cultures. Using these markers, we were able to characterize A. astaci strains from DNA isolates from infected crayfish tissues when crayfish had a moderate to high agent level according to quantitative PCR analyses. The results support the hypothesis that different North American crayfish hosts carry different genotype groups of the pathogen, and confirm that multiple genotype groups, including the one originally introduced to Europe in the 19th century, cause crayfish plague outbreaks in Central Europe. So far undocumented A. astaci genotype seems to have caused one of the analysed outbreaks from the Czech Republic. The newly developed culture-independent approach allowing direct genotyping of this pathogen in both axenic cultures and mixed genome samples opens new possibilities in studies of crayfish plague pathogen distribution, diversity and epidemiology.

Effect of chronic exposure to prometryne on oxidative stress and antioxidant response in red swamp crayfish (Procambarus clarkii).

The aim of the study was to investigate effects of the triazine herbicide prometryne on red swamp crayfish on the basis of oxidative stress, antioxidant indices in hepatopancreas and muscle, and histopathology of hepatopancreas. Crayfish were exposed to prometryne concentrations of 0.51 μg L−1, 0.144 mg L−1, and 1.144 mg L−1 for 11 and 25 days. Indices of oxidative stress (thiobarbituric acid reactive substances (TBARS)), and antioxidant parameters (superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR)) in crayfish muscle and hepatopancreas were measured. Chronic exposure to prometryne did not showed the impact of oxidative damage to cells. Changes activity of the antioxidant enzymes SOD, CAT, and GR were observed in all tested concentrations to prometryne for 11 and 25 days (P < 0.01) as compared with the control group. We did not see any differences in histopatological examination to hepatopancreas. Prolonged exposure of prometryne did not result in oxidative damage to cell lipids and proteins, but it led to changes in antioxidant activity in crayfish tissues. Changes in antioxidant systems were also observed in the environmental prometryne concentration of 0.51 μg L−1. The results suggest that antioxidant responses may have potential as biomarkers for monitoring residual triazine herbicides in aquatic environments.

Impact of sex and size range on fat, cholesterol content, and fatty acid profiles in edible tissues of spiny-cheek crayfish (Orconectes limosus Raf.) from Lake Goplo (Poland)

The aim of the present work was to determine the fatty acid profile, the total cholesterol content, and the percentage of fat in the meat of the abdominal section of spiny-cheek crayfish Oreonectes limosus (Raf.) caught in Lake Gop³o. A total of 138 crayfish, including males, was collected for the study in spring (May 2012). Analyses indicated that fat content was higher in the meat of females (1.31%) than in that of males (1.14%), and there were no statistically significant differences in the fat content between females and males. Differences between the mean fat content in the muscle of males from groups I, II, and III were not statistically significant (P > 0.05). The same results were observed for both groups of females. The total cholesterol content was higher in the meat of female crayfish (95.65 mg 100 g -1 ) than in that of males (88.53 mg 100 g -1 ). The differences between the mean cholesterol content in the muscles of the three male groups were not statistically significant. The same results were observed for the groups of females. In all the crayfish groups, the main SFA was C16:0, MUFAs were dominated by C18:1 n-6, and the highest percentage of PUFA was of C20:5 n-3.

Temporal dynamics of spore release of the crayfish plague pathogen from its natural host, American spiny-cheek crayfish (Orconectes limosus), evaluated by transmission experiments

The crayfish plague pathogen, Aphanomyces astaci, is one of the most serious threats to indigenous European crayfish species. The North American invasive spiny-cheek crayfish, Orconectes limosus, is an important source of this pathogen in central and western Europe. We evaluated potential changes in A. astaci spore release rate from infected individuals of this species by experiments investigating the pathogen transmission to susceptible noble crayfish, Astacus astacus. We filtered defined volumes of water regularly to quantify spore concentration, and sampled crayfish tissues at the end of the experiment. The filters and tissues were then tested for the presence of A. astaci DNA by species-specific quantitative PCR. Additionally, we tested the efficiency of horizontal transmission to apparently uninfected O. limosus. The experiments confirmed that A. astaci can be transmitted to susceptible crayfish during intermoult periods, and that the pathogen was more frequently detected in noble crayfish recipients than in American ones. The pathogen spore concentrations substantially varied in time, and significantly increased during moulting of infected hosts. Our study strengthens the evidence that although the likelihood of crayfish plague transmission by water transfer from localities with infected American crayfish might increase when these are moulting or dying, no time-periods can be proclaimed safe.