engleski

A comparative study of physiological indices of two native and two invasive cryfish species in Croatian rivers

A comparative study of organosomatic indices of two autochthonous species of Astacidae in Croatia, the noble crayfish, Astacus astacus (Linne, 1758) and narrow clawed crayfish Astacus leptodactylus (Eschscholtz, 1823), and the two invasive northamerican species, spiny-cheek crayfish Orconectes limosus (Rafinesque, 1817) and signal crayfish Pacifastacus leniusculus (Dana, 1852), was carried out to detect physiological basis which enable aliens to outcompete native species. Noble crayfish (Aa) is distributed in the continental part of Croatia while narrow-clawed crayfish (Al) spread from eastern to central part of Croatia. Both invasive species were recorded in the Drava River basin in Croatia. Signal crayfish (Pl) is spreading downstream from the north-west along Drava’s tributary, the Mura River and spiny-cheek crayfish (Ol) is spreading upstream from the south-east from the Drava River. As a measure of crayfish condition relative size of hepatopancreas (hepatosomatic indices), gonads (gonadosomatic indices) and tail muscle (muscle indices) and their moisture content were used. Mature males (n = 7–30) and females (n = 7-16) of four species were trapped by baited LiNi traps during September 2009, frozen at -20 oC, held for several days to few weeks, then thawed, weighed and dissected. Digestive glands, gonads and abdominal muscle were removed and weighed. Proportions of hepatopancreas and tail muscle moisture content (HM and MM), as a measure of energy content, are lower in invasive species then in autochthonous species which indicated their better condition and thus better competitive ability. On the other hand, proportions of gonads (Giwet) in body weight were not as different between native and invasive species as it was expected. Therefore, higher fecundity of invasive species could be result of better survival and adaptation of pleopodal eggs rather than higher proportion of gonads in body mass. Furthermore, proportion of tail muscle (Miwet) in spiny-cheek crayfish is higher than in native species which might indicate better adaption abilities in that species compared to natives. Quite contrary, signal crayfish had the lowest proportion of tail muscle in body weight (Miwet) compared to other species which is probably result of huge mass of claws in this species.

invasive crayfish species; physiological indices; Croatia

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