Astacus Leptodactylus Eschscholtz Research Articles

Перебіг гаметогенезу у вузькопалих річкових раків (Astacus leptodactylus Eschscholtz, 1823) в умовах водойм Придніпров’я

Purpose. Detailed study of the stages of reproductive development (oogenesis and spermatogenesis) of crayfish using the example of the narrow-clawed crayfish Astacus leptodactylus Eschscholtz, 1823 in reservoirs of the Dnieper region. Methodology. The study was conducted during the period of 2022-2023. The material for the study were individuals of the narrow-clayed crayfish A. leptodactilus. A morphometric analysis was performed, after which the crayfish were preserved in an alcohol solution (70% ethanol and 2% glycerol) for the slide of histological cross-sections. Histological slides of crayfish gonads were made in accordance with generally accepted histological methods. The analysis of the cross-sections was carried out using a microscope and a digital camera. Descriptions of the slides were made using atlases of histology of decapods. Findings. It has been found that the gonads exhibited an asynchronous development and were in stages C, D, E, F, with a significant number of oocytes in stage C. The diameter of oocytes in phase D mainly ranged from 195.72 ± 12.43 μm with an area of 38,21 μm². The nucleus had a diameter of 48.14 ± 1.44 μm. In phases E, the size of oocytes reached a diameter of 259.24 ± 76.18 μm and an area of 52,850 ± 5,760 μm². Throughout phase D, the diameter of vacuoles was 18.45 ± 0.86 μm. In phase E, the diameter of vacuoles increased to 26.55 ± 1.24 μm, and as soon as in the transitional phase E–F, vacuoles merged massively with individual non-merging vacuoles having a diameter of 25.22 ± 1.12 μm. At the terminal stage F, oocytes reached definitive sizes and were ready for ovulation. The average size of larvae was 2600 ± 0.093 μm in diameter. The course of spermatogenesis in crayfish males was characterized by synchronous development of gametes. The analysis of sections showed that the area of spermatocytes was 43.14 ± 0.74 μm with a diameter of 7.14 ± 0.23 μm². In turn, the nuclei of spermatocytes had dimensions of 21.64 ± 0.35 μm² and 5.24 ± 0.02 μm in diameter. Originality. A comprehensive analysis of crayfish gametogenesis was conducted for the first time in the zones of the reproductive range of the Dnieper reservoirs. Some features of the stages of oogenesis and spermatogenesis were identified and the impact of the ecological regime on the reproduction of crayfish was studied. Keywords: narrow-clawed crayfish, water bodies, reproduction, ecological state of water bodies, reservoir, eggs, gametogenesis.

Does persistent organic pollutant PFOS (perfluorooctane sulfonate) negative impacts on the aquatic invertebrate organism, Astacus leptodactylus [Eschscholtz, 1823

Highly persistent perfluorooctane sulfonate (PFOS) is an industrial fluorinated organic chemical with significant bioaccumulation and biomagnification properties. The purpose of this study was to determine the toxic effects of sublethal PFOS on the aquatic invertebrate organism, narrow-clawed crayfish [Astacus leptodactylus Eschscholtz, 1823]. The 96 h LC50 value was determined as 48.81 mg/L (34.19-63.68 mg/L) with probit analysis. The sublethal experimental design was formed into four groups solvent control (DMSO, dimethyl sulphoxide), non-treated control group, and 1/10 (5 mg/L) and 1/100 (0.5 mg/L) of 96 h LC50 of PFOS, and crayfish were exposed for 48 h, 7 d, and 21 d under laboratory conditions. Total haemocyte counts (THCs) decreased, while the haemolymph total antioxidant status (TAS) values increased (p < 0.05) after exposure to 0.5 and 5 mg/L PFOS for 48 h, 7 d, and 21 d. Haemolymph total oxidative stress (TOS) levels significantly increased at 5 mg/L PFOS concentration (p < 0.05). Catalase (CAT) activities increased at both concentrations after 48 h and 7 d and then returned to control levels after 21 d; whereas superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities did not change in muscle tissue (p > 0.05). GPX and CAT activities decreased, but SOD activity increased in hepatopancreas tissue (p < 0.05). SOD activity at both concentrations and CAT activity at 5 mg/L PFOS exposure decreased in gill tissue, while GPX activity increased at both concentrations of 48 h and 7 d and returned to control values on day 21 of exposure. Histopathological alterations were detected in hepatopancreas and gill tissues. Lamellar deformations, epithelial hyperplasia, and haemocytic infiltrations were observed in the gill tissues, whereas tubular degeneration, tubule loss, necrosis, and lesions in the hepatopancreas tissues were the major recorded alterations. As a result, the sublethal concentrations of PFOS have toxic effects on crayfish and histologically cause tissue damage. Our findings also support a better understanding of the early toxicological effects of PFOS in freshwater ecosystems. Also, it could be concluded that A. leptodactylus is a reliable model for examining histopathological alterations and differences in enzyme activities together with the haemolymph findings in toxicology studies amid aquatic species.

Bafra Balık Gölleri’nden Tatlı Gölü ve Gıcı Gölü’ndeki Tatlısu Istakozu (Astacus leptodactylus Eschscholtz, 1823)’nun Bazı Popülasyon Parametrelerinin Belirlenmesi

In this study, determination of the morphometric parameters and egg fecundity freshwater crayfish (Astacus leptodactylus Eschscholtz, 1823), measurement and comparing of were aimed in Tatlı and Gıcı Lakes from Bafra Fish Lakes in Samsun, Turkey. The research was carried out between November 2018 and October 2019 by monthly catching of freshwater crayfish using fyke net at determined stations. While 105 of 242 freshwater crayfish from Tatlı Lake were female and 137 were male, 87 of 216 freshwater crayfish from Gıcı Lake were female and 129 were male and the difference between the sexes was not significant. The average total length and average weight of freshwater crayfish from Tatlı Lake were 10.27±0.09 cm and 33.76±0.88 g, respectively. In Gıcı Lake, the average total length and average weight of freshwater crayfish were 10.44±0.41 cm and 37.15±1.91 g, respectively. A strong positive linear relationship was found between length and weight of freshwater crayfish in Tatlı Lake and Gıcı Lake. However, the claw length and claw width of the male freshwater crayfish were greater. The average number of individual eggs, the average total egg weight, the average unit egg weight and the average egg diameter of the sampled egged crayfish in Tatlı Lake were 241.24±11.94, 3.22±0.17 g, 0.013±0.001 g and 2.61±0.02 mm, respectively. These were 245.38±15.87, 3.03±0.19 g, 0.013±0.001 g and 2.73±0.02 mm for sampled egged lobsters in Gıcı Lake, respectively. At the end of the study, it was determined that the environmental and morphometric parameters, egg fecundity of freshwater crayfish in Tatlı and Gıcı Lakes were similar between the lakes.

Determination of meat productivity and biochemical composition of freshwater lobster (Astacus leptodactylus Eschscholtz, 1823) in Lake Tatlı and Lake Gici from Bafra Fish Lakes

In this study, it was aimed to determine the meat productivity and biochemical compositions of freshwater lobster (Astacus leptodactylus Eschscholtz, 1823) in Tatlı and Gıcı Lakes from Bafra Fish Lakes. The research was carried out by monthly fishing of freshwater lobsters using Pinters at the stations determined between November 2018 and October 2019. While 105 of the 242 freshwater lobsters caught in Tatlı Lake were female and 137 male, 87 of the 216 freshwater lobsters obtained in Gıcı Lake were found to be female and 129 as male. In the study, the average total length and an average weight of freshwater lobsters in Tatlı Lake were determined as 10.27±0.09 cm and 33.76±0.88 g, respectively. In Lake Gıcı, the mean total length was 10.44±0.41 cm and the average weight was 37.15±1.91 g. While the total meat yield of female and male lobsters obtained from Tatlı Lake was 15.27±0.51% and 15.13±0.64%, respectively, the total meat yield of female and male lobsters obtained from Gıcı Lake was 15.18±0.59% and 15.51± 0.69.%, respectively. Crude protein, crude oil, crude ash and moisture values ​​were determined as 16.10±0.23, 0.59±0.39%, 1.60±0.24% and 81.60±0.26%, respectively, in lobsters obtained from Lake Tatlı. In lobsters, it was determined as 15.49±0.13%, 0.61%±0.06%, 1.57±0.36% and 82.24±0.19%, respectively.

De novo cloning and functional characterization of potassium channel genes and proteins in the crayfish Astacus leptodactylus (Eschscholtz, 1823) (Decapoda: Astacidea: Astacidae)

Abstract Current knowledge about the molecular properties of the crustacean ion channels is rather limited even if crustaceans have been widely used as a model in neuroscience. We cloned for the first time two different potassium channel genes from the freshwater crayfish Astacus leptodactylus (Eschscholtz, 1823), one of the genes functionally expressed in the Xenopus oocytes. The open-reading frames of the genes were 1,203 and 3,447 bp, respectively. The nucleic acid sequence of the genes and associated proteins were similar to those of a typical potassium channel. BLAST analyses indicated that one of the cloned genes had a substantial similarity to an inward-rectifier potassium channel whereas the other gene was similar to a high-conductance-KCa type potassium channel reported in related species. Transmembrane topology and three-dimensional structure of the coded proteins were calculated and functional regions of the channel proteins responsible for ion selectivity, voltage sensing, gating, and calcium binding were identified. One of the cloned channel genes has been expressed in the Xenopus oocytes. Analysis of the expressed potassium currents confirmed that the cloned gene was coding a typical Kir-type potassium channel with ATP sensitivity.

In vitro effects of selected endocrine disruptors (DEHP, PCB118, BPA) on narrow-clawed crayfish (Astacus leptodactylus) primary cells.

Environmental pollutants with endocrine-disrupting effect are of global importance due to their contribution to the aethiologies of variety of complex diseases. These lipophilic pollutants are persistent in the environment and able to bioaccummulate in nontarget organisms. BPA, DEHP and PCB118 (dioxin-like PCB) are associated with endocrine disruption effects, while information on their effects on aquatic invertebrates are limited. In the current study, the effects of these compounds, which are ubiqutous and present at low concentrations in the environment, are studied in the primary hepatopancreas, muscle, gill, intestine and gonadal cultures of narrow-clawed crayfish (Astacus leptodactylus Eschscholtz, 1823), a widely distributed freshwater crayfish in Turkey with high economic importance. IC50 values following MTT assay ranged 0.27-12.61 nM; when compared with other tissues, the gonads were more affected with lower IC50 values. PCB118 induced higher cytotoxicity, while DEHP was the least toxic compound. This is the first study on the primary culture of A. leptodactylus¸ and the toxic effects of these compounds in this organism providing mechanistic insights on the responses and detoxification capacity of the organs. This study provides basis to unravel the mechanism of action of the tested EDCs in crayfish and improvement of cell culture conditions for ecotoxicity and screening assays.

Evaluation of the acute toxic effect of azoxystrobin on non-target crayfish (Astacus leptodactylus Eschscholtz, 1823) by using oxidative stress enzymes, ATPases and cholinesterase as biomarkers

Azoxystrobin is a broad-spectrum fungicide used worldwide. Since azoxystrobin spreads to large areas, its toxic effects on non-target organisms have aroused interest. In this study, the acute toxicity (96 h) of azoxystrobin on the crayfish (Astacus leptodactylus) was examined by using various biomarkers. The 96 h-LC50 dose (1656 mg L−) and its three sub-doses (828, 414, 207 mg L−1) were applied to crayfish. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were increased significantly compared to the control in hepatopancreas, gill and muscle tissues. The activities of acetylcholinesterase (AChE) and glutathione S-transferase (GST) increased, and glutathione reductase (GR) activity decreased significantly in hepatopancreas. Level of reduced glutathione (GSH) decreased significantly. The content of malondialdehyde (MDA) increased in a dose-dependent manner in all azoxystrobin treatments with the exception of the lowest dose (207 mg L-1)treatment. ATPases (Na+/K+ -ATPase, Mg2+ -ATPase, Ca2+ -ATPase, total ATPase) were significantly inhibited in gill and muscle tissues. The results of the present study indicate that azoxystrobin induces oxidative stress, and has adverse effects on activities of AChE and ATPases in crayfish.

Чужеродные макробеспозвоночные в донных сообществах Новосибирского водохранилища (эколого-фаунистический обзор)

Строительство и последующее использование водохранилищ стало ведущим фактором проникновения и распространения чужеродных видов в Обь-Иртышском бассейне. Фауна чужеродных видов Новосибирского водохранилища представлена пятью видами, три из которых (Gmelinoides fasciatus Steb., Micruropus possolskii Sowinsky и Neomysis intermedia (Czerniavsky)) были преднамеренно вселены для повышения кормовой базы водоема, еще два (Viviparus viviparus (L.) и Astacus leptodactylus Eschscholtz) появились в результате непреднамеренных интродукций. Прослежена история проникновения и натурализации каждого вида, проанализированы экологические факторы их обитания, рассмотрены особенности современного пространственного распределения вселенцев. Отмечено, что несмотря на невысокое видовое богатство, вселенцы существенно влияют на структурные характеристики донных сообществ водохранилища.

Interactions of season, sex and size on nutrient composition of freshwater crayfish (Astacus leptodactylus Eschscholtz, 1823) from Lake Eğirdir

Effects of interaction of season, sex and size on nutrient composition and fatty acid profiles of freshwater crayfish (Astacus leptodactylus) caught from the Eğirdir Lake were investigated on a factorial level. In the factorial analysis; 4 levels of season factors (autumn, winter, spring, summer), 2 levels of sex factor (male, female) and 1 level size factor were available. According to the results of biochemical analysis, effects of seasons were determined on crude protein and moisture levels. Crude ash levels changed depending on sex and season. There were no interactions of these three factors on the crude fat levels. The season and sex affected on LA, α-LNA and ∑HUFA levels. ARA, EPA, DHA, ∑SFA and ∑PUFA levels were affected from seasonal changes. Interaction of season/sex affected to ∑MUFA levels. The crude protein content, DHA, EPA and n-3 contents in tail muscle of A. leptodactylus increased by feeding in summer while these contents decreased by gonadal development in autumn. Therefore, in terms of nutritional protein contents, EPA, DHA and n-3 of this species were higher in summer. EPA, n-3 and DHA contents are important for A. leptodactylus.

Effects of dietary galactooligosaccharide enriched commercial prebiotic on growth performance, innate immune response, stress resistance, intestinal microbiota and digestive enzyme activity in Narrow clawed crayfish (Astacus leptodactylus Eschscholtz, 1823)

The present study was carried out to evaluate dietary effects of galactooligosaccharide (GOS) (0, 1, 2 and 3%) on the innate immune response, stress resistance, intestinal microbiota, digestive enzyme activity as well as growth performance of narrow clawed crayfish (Astacus leptodactylus). At the end of a 97-day feeding trial, crayfish fed 2% GOS supplemented diets had significantly higher total haemocyte count (THC), semi-granular cell (SGC) and hyaline cell (HC) counts compared to the other groups (P < .05). Furthermore, the highest catalase (CAT) was in crayfish fed 3% GOS-enriched diet while the highest lysozyme (LYZ) activity was detected in treatments fed 2 and 3% enriched diets (P < .05). Evaluation of autochthonous intestinal microbiota revealed that the total intestinal heterotrophic bacteria (TIHB) counts increased in all GOS fed treatments as well as lactic acid bacteria (LAB) levels in 2 and 3% GOS supplemented groups (P < .05). However, following the replacement of GOS-supplemented diet with the basal diet for 14 days, LAB counts reduced quickly. The highest amylase and lipase activity observed in the groups fed 2 and 3% GOS (P < .05). Moreover, dietary GOS enhanced the THC, SGC and HC count in crayfish fed 1 and 2% GOS as well as CAT activity in 3% GOS-supplemented group (P < .05). These results confirm the advantageous effects of dietary GOS on innate immunity, stress resistance, intestinal microbiota, and digestive enzyme activity in A. leptodactylus, albeit had no significant improvement on the growth performance and survival (P > .05).

Changes in digestive enzyme activities during different developmental stages of the crayfish Astacus leptodactylus Eschscholtz, 182

The present study determined changes in protease, α-amylase and lipase activities during embryonic and post-embryonic developmental stages of the freshwater crayfish &lt;em&gt;Astacus leptodactylus&lt;/em&gt; Eschscholtz, 1823. The embryonic stages studied comprised Phase III (blastula formation), Phase X (embryos with anlagen of masticatory) and Phase XIV (embryos with strongly developed posterior hepatopancreas lobes). The post-embryonic stages comprised Stage I (no feeding) and Stage II (prior to the onset of feeding). Protease and α-amylase activities were relatively high as compared with lipase activity. Protease activity values showed a steady increase from Phase III to Stage I. α-amylase and lipase activities were low in Phase XIV. The activities of these two enzymes tended to increase just before hatching and reached the highest levels in Stage II. Digestive enzyme activities increased in accordance with maturation of the hepatopancreas and prior to the onset of external feeding. Protease activity was high in the early stage of embryonic development and continued to increase in later stages. On the other hand, α-amylase and lipase activities were low until maturation of the hepatopancreas and then remained high. The results of the present study provide important information on changes in digestive enzyme levels during different developmental stages of &lt;em&gt;A. leptodactylus&lt;/em&gt;.

Artificial neural networks approach in length-weight relation of crayfish (Astacus leptodactylus Eschscholtz, 1823) in Eğirdir Lake, Isparta, Turkey

Artificial neural networks approach in length-weight relation of crayfish (Astacus leptodactylus Eschscholtz, 1823) in Eğirdir Lake, Isparta, Turkey

Crayfish in central and southern Ukraine with special focus on populations of indigenous crayfish Astacus pachypus (Rathke, 1837) and their conservation needs

Abstract The thick‐clawed crayfish (Astacus pachypus Rathke, 1837) is the least studied indigenous crayfish species in Europe. Information about its distribution and biology is out of date by more than 15 years. This study identified 94 localities with potential occurrence of thick‐clawed crayfish in eight southern and central regions of Ukraine, using questionnaire and literature analysis. Based on the information obtained, a field survey was conducted to examine and confirm the current distribution and abundance of crayfish species and evaluate basic water quality and habitat characteristics in each locality. Details of density, sex ratio in the catches, health and moulting condition, threat level and water quality were identified for each population of A. pachypus. Only four populations of this species were found, in lower parts of the Dnieper River, co‐occurring with Astacus leptodactylus Eschscholtz, in Kakhovka reservoir near Vesele village, two sites on the Dnieper River near Nova Kakhovka town and near Prydniprovske village, and one locality on the Dnieper's tributary – the Ingulec River near Sadove village. Populations of thick‐clawed crayfish at three sites had low crayfish densities of 0.3–0.4 crayfish m−2 or catch efficiency 0.2 crayfish per trap night. Only one locality on the Dnieper River, close to Nova Khakovka, had a stronger population with higher density (1.7 crayfish m−2). Healthy thick‐clawed crayfish inhabit larger water bodies with stable environments and good water quality. Female catch per unit effort was lower, and they had a higher percentage of chelae injuries compared with males. All of the identified thick‐clawed crayfish populations are exploited by uncontrolled fishing for consumption and there is an urgent need for conservation of both the crayfish and their habitat.

Effect of different substrates on survival and growth of juveniles of the freshwater narrow-clawed crayfish Astacus leptodactylus Eschscholtz, 1823 (Decapoda, Astacidae)

Substrate is a key factor for successful crayfish culture, and it can be used to increase the survival rate. The effects of substrate on the survival and growth of Astacus leptodactylus Eschscholtz, 1823 were evaluated in flow-through compartments, divided into three sections and with two different substrates, over a period of 90 days. The three treatments used in the study were: artificial ropes, small stones, and a control group that received no substrate. The survival rate was highest in the small-stones treatment group (77.3%) and was lowest in the without-substrate treatment group (41.3%), while the artificial-ropes group showed an intermediate value (65.3%). Total yield was lower in the control group, 22.46% (25.0 g) as compared to the small-stones treatment group, with 42.3% (51.3 g) and the artificial-ropes treatment with 35.51% (55.8 g). In addition, cheliped injuries were found in higher proportion in the group without cover, and the artificial ropes yielded better results compared to the small-stones and no-substrate group in regard of the growth-increase rate.

Visibility of precursors of the gonopods in a freshwater crayfish, Astacus leptodactylus Eschscholtz, 1823 (Decapoda, Astacidae)

Astacus leptodactylusEschscholtz, 1823 is an important, marketable species of crustacean, consumed intensely as a luxury food in many countries. BecauseA. leptodactylusis less cannibalistic than other crayfish species, is more fecund, and has a fast growth rate, it is accepted as a considerably suitable crayfish for culturing in extensive pond systems. Information on the reproductive biology and anatomy of crayfish is important for developing suitable production methods. Sex recognition may also be essential in separating males and females in crayfish rearing (i.e., to prevent cannibalism, males grow faster than females). Although male reproductive system morphology and spermatophore formation in crayfish, includingA. leptodactylus, have been studied in detail, this study is the first to demonstrate the visibility of precursors of the gonopods and, thus, the actual presence of gonopods, which of course determine the male sex, in a freshwater crayfish. The present study shows that the first signs of secondary sexual characters (i.e., precursors of the gonopods) can be distinguished in the form of small tubercles on the first abdominal somite in male stage 4 juveniles, and the gonopods themselves are distinguishable in male stage 5 juveniles inA. leptodactylus. In conclusion, sex differentiation inA. leptodactyluscan be realized already in stage 4 juveniles. Further studies should be carried out on the presence and shape of precursors of gonopods in stage 4 and gonopods in stage 5 juveniles of species of astacid crayfish in order to facilitate solving taxonomic problems in the family Astacidae.

ABUNDANCE OF NARROW-CLAWED CRAYFISHES (Astacus leptodactylus Eschscholtz, 1823) AND ITS TRENDS IN LAKE SEVAN, ARMENIA

The narrow-clawed crayfish ( Astacus leptodactylus Eschscholtz, 1823) is an indigenous spe­cies in Arme­nia. In 1980s it was occasionally introduced in Lake Sevan where its population started to grow. There is a large scale fishery of the crayfish in the Lake, as its demand remains high. Industrial stock of crayfishes at the Lake monitored annually, shows statistically sig­nifi­cant decline in the 2004-2011 period. This decline can be described by logarithmic model y = -577.5ln(x) + 2158, F = 50.27, P<0.001. The catch rate of crayfish net-boxes also shows loga­rithmic decline F = 9.27, P<0.05 in the 2004-2011 period. Since the net boxes are designed to catch the larger size crayfishes only, the decline indicates a decrease of average size among crayfish population. The female fertility does not show statistically significant correlation with the in­dustrial stock of crayfish. It does, however, show neg­ative correlation with the catch rate of the net boxes: r Pearson = -0.686, P<0.05; ρ Spearman = -0.647, P<0.05. The correlation can be ex­plained as the big animals are actively removed through harvesting, while small­er animals are not captured; meanwhile the remaining smaller animals produce fewer eggs. Decline of cray­fish stock cannot be explained by diseases and inva­sive species, but can be explained by over­harvesting. Continuation of harvesting aimed at supplying the ex­isting demand might result to population decline of more than 70% during next 17 years.

The influence of etofenprox on narrow clawed crayfish (Astacus leptodactylus Eschscholtz, 1823): Acute toxicity and sublethal effects on histology, hemolymph parameters, and total hemocyte counts

The acute and sublethal effects of etofenprox, a nonester pyrethroid, was determined in narrow-clawed crayfish (Astacus leptodactylus Eschscholtz, 1823). Semistatic bioassay procedures were followed in both experiments, and the 24, 48, 72, and 96 h LC50 values (with 95% confidence limits) of technical etofenprox for crayfish were calculated as 0.68, 0.61, 0.45, and 0.41 µg/L, respectively based on Finney's probit analysis. Two concentrations of etofenprox (0.04 and 0.1 µg/L) were tested to determine sublethal effects due to 96 hours exposure. After exposure to sublethal etofenprox, hemolymph glucose, and lactate levels increased while total hemocyte counts and sodium levels decreased (p < 0.05). Hemolymph calcium, potassium, magnesium, and chloride concentrations did not change significantly. Histological alterations were evident in the gills and hepatopancreas after exposure to sublethal etofenprox concentrations. Lamellar hyperplasia and lining in the afferent and efferent branchial vessels were recorded in gills; whilst tubule necrosis was obvious in hepatopancreas. Etofenprox was found to be very highly toxic to crayfish, a nontarget organism. Exposure to sublethal concentrations for 96 h affected circulating hemocytes and hemolymph stress parameters via histological response, to compansate for the adverse effects of etofenprox. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 887-894, 2015.

Antifungal effect ofOriganum onitesessential oil as an alternative to formalin in the artificial incubation of narrow-clawed crayfish (Astacus leptodactylusEschscholtz, 1823)

As alternative to formalin, the antifungal effect of a plant product [Origanum onites L. (Lamiaceae) oil] was investigated for use in the artificial incubation of narrow-clawed crayfish (Astacus leptodactylus Eschscholtz) eggs. For this purpose, this study was conducted as two experiments. In experiment I, the eggs were artificially incubated for 40 days. In experiment II, juveniles were cultured to determine effects of O. onites oil on juveniles for 30 days. The experimental groups were as follows: formalin (3500 ppm for 15 min), O. onites oil (300 ppm for 15 min, 700 ppm for 2 min and 1000 ppm as a dip treatment 15 split-second) and a control (no treatment). In the experiment I, the highest hatching rate (86%) and survival rate of stage II juveniles (80%) were observed in 1000 ppm dip group. These results were similar to that of formalin group (85% and 79%) respectively. The control group exhibited the lowest hatching rate (49%) and stage II rate (42%) compared with the 1000 ppm dip group and 3500 ppm formalin treatments. However, other concentrations (300 and 700 ppm) of O. onites showed toxic effects on the eggs and there was no hatching. In the experiment II, the survival rate and growth performance of the crayfish juveniles were similar in all groups. This study indicated that the 1000 ppm O. onites dip treatment could be a good alternative to formalin for improved egg hatchability in the artificial incubation of crayfish eggs.

Two distinct evolutionary lineages of the Astacus leptodactylus species-complex (Decapoda : Astacidae) inferred by phylogenetic analyses

Narrow-clawed crayfish (Astacus leptodactylus Eschscholtz, 1823 species-complex) is one of five European freshwater crayfish species. Even though widely distributed, it hasn’t been frequently studied and its taxonomy and systematics are unresolved. The results of a recent comparative morphometric character study revealed that morphometry of Asian and European populations differ significantly. In this research, for the first time, mitochondrial molecular markers (16S rRNA and COI) were used with the aim of elucidating the phylogenetic relationship between European and Asian populations of the narrow-clawed crayfish. Analyses included crayfish from Croatia, Bulgaria, Armenia, Russia, Poland and Turkey, and three different optimality criteria were applied. Phylogenetic relationships were reconstructed using the COI dataset, as well as the concatenated one (COI + 16S rRNA). For both datasets, congruent topologies were obtained and trees were characterised by the existence of two well supported phylogroups, one that included European populations, and the other Asian. Results indicate the presence of distinct evolutionary lineages within the A. leptodactylus species-complex, and corroborate previous results obtained using morphometric analyses.

Temporal Changes in Concentrations of Some Trace Elements in Muscle Tissue of Crayfish,Astacus leptodactylus(Eschscholtz, 1823), from Keban Dam Lake

Crayfish (Astacus leptodactylus Eschscholtz, 1823) is the native crayfish species in Turkey. It was exported regularly to Western Europe. In this study, bioaccumulation and temporal trends of some trace elements (arsenic: As, cadmium: Cd, copper: Cu, mercury: Hg, lead: Pb, and zinc: Zn) in edible abdomen muscle of crayfish from Keban Dam Lake (Elazığ, Turkey) were investigated for the 2006–2012 period. Sequence of metal concentration levels was Zn > Cu > Hg > Pb > Cd > As in muscle tissues. The highest concentration of Zn (21.69 mg kg−1) was detected in 2006, while the lowest (4.35 mg kg−1) in 2009. In general, it was found that the concentrations of trace elements investigated were lower than the maximum permissible limits of the food regulations of the Ministry of Food, Agriculture, and Livestock (MFAL), the Turkish Food Codex and Commission Regulation (EC). If the crayfish selected for the study are recognized as bioindicators of environmental pollution, then it is possible to conclude that the changes in studied trace elements concentrations in the Keban Dam Lake are being steady.