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We studied the presence of possible Aphanomyces astaci infections in eight Turkish narrow-clawed crayfish ( Astacus leptodactylus ) populations by analyzing the prevalence and genotypes of the disease agent A. astaci . The qPCR analyses revealed A. astaci infection in seven of the studied eight populations, with the agent level A2 or higher. The agent levels among the infected populations varied from A0 to A5, i.e., from negative to high level of infection, based on qPCR ranking. Based on the sequencing of the chitinase gene and the mitochondrial ribosomal rnnS and rnnL subunits, we detected both A (As) and B (PsI) haplogroups of A. astaci in our samples, with each of the studied populations being carriers of only one haplotype. The results confirm previous detections of A. astaci in Turkish narrow-clawed crayfish populations and reveal, that both A and B haplogroup A. astaci carriers exist widely in A. leptodactylus populations of Turkey. Nous avons étudié la présence possible d' Aphanomyces astaci dans huit populations turques d'écrevisses à pattes grêles ( Astacus leptodactylus ) en analysant la prévalence et les génotypes de l'agent pathogène A. astaci . Les analyses qPCR ont révélé une infection à A. astaci dans sept des huit populations étudiées, avec le niveau d'agent A2 ou plus. Les taux d'agents chez les populations infectées variaient de A0 à A5, c'est-à-dire du niveau négatif au niveau élevé d'infection, selon le classement qPCR. En se basant sur le séquençage du gène de la chitinase et des sous-unités rnnS et rnnL du ribosome mitochondrial, nous avons détecté les haplogroupes A (As) et B (PsI) d' A. astaci dans nos échantillons, chacune des populations étudiées n'étant porteuse que d'un seul haplotype. Les résultats confirment les détections précédentes d' A. astaci dans les populations d'écrevisses à pattes grêles et révèlent que les porteurs des deux haplogroupes d' A. astaci existent largement dans les populations d' A. leptodactylus de Turquie.

Astacus leptodactylus Eschscholtz, 1823 is an important, marketable species of crustacean, consumed intensely as a luxury food in many countries. Because A. leptodactylus is 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, including A. 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 in A. leptodactylus. In conclusion, sex differentiation in A. leptodactylus can 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.

Freshwater crayfish are amongst the largest macroinvertebrates and play a keystone role in the ecosystems they occupy. Understanding the global distribution of these animals is often hindered due to a paucity of distributional data. Additionally, non-native crayfish introductions are becoming more frequent, which can cause severe environmental and economic impacts. Management decisions related to crayfish and their habitats require accurate, up-to-date distribution data and mapping tools. Such data are currently patchily distributed with limited accessibility and are rarely up-to-date. To address these challenges, we developed a versatile e -portal to host distributional data of freshwater crayfish and their pathogens (using Aphanomyces astaci , the causative agent of the crayfish plague, as the most prominent example). Populated with expert data and operating in near real-time, World of Crayfish ™ is a living, publicly available database providing worldwide distributional data sourced by experts in the field. The database offers open access to the data through specialized standard geospatial services (Web Map Service, Web Feature Service) enabling users to view, embed, and download customizable outputs for various applications. The platform is designed to support technical enhancements in the future, with the potential to eventually incorporate various additional features. This tool serves as a step forward towards a modern era of conservation planning and management of freshwater biodiversity.

Astacus leptodactylus is naturally and widely distributed in lakes, ponds and rivers throughout of Turkey. It has also been stocked in many freshwater systems in Turkey to establish new populations and to restore crayfish stocks devastated by the plague (Aphanomyces astaci) and some other reasons (i.e., farming and culinary purposes). Human consumption of A. leptodactylushas always been very low in Turkey; therefore, it was exported mainly to Europe until 1986. A plague was observed in 1985 in Eirdir, Apolyont, Sapanca and Manyas lakes which included the main harvest areas, and the fishery was lost within 2 years. Consequently, crayfish harvest was banned in all populations to control the plague. Because of the plague, over-fishing and pollution, the harvest of A. leptodactylusin Turkey declined from approximately 5000 (1984) to 200 (1991) tons annually. In 2000s, there has been a gradual increase in the rate of harvest of A. leptodactylusin Turkey, reaching approximately 1600-1900 tons annually, but the plague is still observed in this species at certain localities. The present study reveals that A. leptodactylus in Turkey needs professional support for recovery, because the present harvest of A. leptodactylusis still nearly 20% of the crayfish catch in 1980s.[PUBLICATION ABSTRACT]

The effect of vitamin E on the pleopodal egg number of Astacus leptodactylus (Eschscholtz, 1823) was studied. Crayfish were fed 2% of their total wet weight daily with vitamin E supplemented diets and a control for 70 days. The vitamin E content of the control diet, diet 1, diet 2 and diet 3 were 20 mg kg^sup -1^, 40 mg kg^sup -1^, 80 mg kg^sup -1^ and 160 mg kg^sup -1^ respectively on a dry weight basis. Vitamin E levels of the control and experimental diets were analysed by High Performance Liquid Chromatography. Results showed that diets containing supplemental vitamin E were associated with an increase in the number of pleopodal eggs. The best result was obtained with diet 2 containing 80 mg kg^sup -1^ supplemental vitamin E.[PUBLICATION ABSTRACT]

The differences in the ridge structure of the mandibles of different size Astacus leptodactylus (32-80 mm carapace length, CL) were investigated. The results showed that a modification occurs with an increase in size in the incisor ridge of mandibles in A. leptodactylus. The results also showed that A. leptodactylus possesses four different types of ridge structure in the mandibles. These are: (1) Incisor ridge with big teeth (dentate crenate), (2) Blade-like incisor ridge with numerous small teeth, (3) Blade-like ridge (toothless), (4) Blunt ridge. In conclusion, it is thought that the incisor ridge modification of the mandibles may cause the difference in the food choice of different size A. leptodactylus, because, crayfish possessing different ridge structures of the mandible may probably feed on different type of food.[PUBLICATION ABSTRACT]