The effects of invasive epibiont Dreissena polymorpha on the narrow-clawed crayfish (Astacus leptodactylus, Astacidae) in Eğirdir Lake, Turkey: a case study

In aquatic ecosystems, organisms are in a close relationship with each other. While this relationship is sometimes beneficial for both species, it can sometimes be harmful to one species. This study aimed to investigate the effects of colonized zebra mussels Dreissena polymorpha on the growth parameters and total hemocyte counts of the narrow-clawed crayfish Astacus leptodactylus from Eğirdir Lake (Turkey). Zebra mussels were found on various body parts of crayfish and the most intense (44.7%) colonization was in the carapace region. There were significant differences between various biometric data and ratios of the narrow-clawed crayfish with epibiont D. polymorpha and without epibiont D. polymorpha (the control group) in terms of total length, abdomen width, arm length and chelae length, carapace width/carapace length, carapace length/abdomen length, abdomen width/carapace width, and chelae width/chelae length (p < 0.05). When the total hemocyte counts were examined, lower values ​were obtained in the narrow-clawed crayfish with zebra mussels compared to the control group (p < 0.05). As a result, epibiont organisms have negative effects on the health and growth status of the host organisms considering total hemocyte counts and biometric data.