A contribution on the morphometrics of the thick-clawed crayfish Pontastacus pachypus (Rathke, 1837) (Decapoda, Astacoidea, Astacidae)

The thick-clawed crayfish Pontastacus pachypus (Rathke, 1837) is an endangered, and the least known, crayfish species in Europe. Currently, detailed information regarding the morphology, ecology and reproduction of thick-clawed crayfish is outdated. This study presents, for the first time, detailed photographs of the thick-clawed crayfish, and updated information on distinctive morphological characters and morphometric analysis. New specifications of the carapace and appendage morphological characteristics were estab-lished as: 1) the rostrum is long, sharply pointed and has three pairs of distinctive sub-apical lateral spines, 2) two well-developed pairs of post-orbital ridge on the carapace are ended by prominent spine; 3) each finger of chelae ends with a black sharp tip. Among the 18 morphometric indices, carapace width to the total length (CPW/TL), abdomen width to the total length (ABW/TL) and claw height to the claw width (CLH/CLW) clearly differentiate P. pachypus from the other representatives of Astacus genus (A. colchicus and A. astacus) and P. leptodactylus (P<0.05). Comparison of individual indices between P. pachypus and P. leptodactylus revealed that al-most all indices differed significantly except head length to the total length (HEL/TL) and rostrum length to the total length (ROL/TL). This study contributes to the identification of the thick-clawed crayfish for the purpose of conservation and protection of its localities.

Automated summary

This study provides detailed photographs and updated information on the morphology and morphometric analysis of the endangered thick-clawed crayfish. It identifies distinctive morphological characters that differentiate the species from other crayfish and contributes to its conservation and protection.