G. Gibertini

Allometry in the ontogenesis of Austropotamobius pallipes species complex (Decapoda: Astacidae): The use of geometric morphometrics

Abstract The white-clawed crayfish Austropotamobius pallipes is a threatened European crayfish. Our purpose is to provide traits on the anterior portion of the carapace by geometric morphometrics describing landmarks poorly or not affected by ontogeny and sexual dimorphism. In this study, 112 crayfish (59 females and  53 males) from a central Italy brook were studied. A digital picture of dorsal side of each specimen was taken and then analysed according to a least-square method by the Generalized Procrustes Analysis that allowed the size to be standardised and to optimise rotation and translation of the configuration, after the fixation of 18 2D landmarks. In this study, we found no features affected by sexual dimorphism, while a certain percentage of morphological differences were observed only between juveniles and adults. These differences can be explained by positive and negative allometry, and interpreted as a direct effect of growth. The most evident of these changes regards the carapace enlargement and the ocular socket departure. Then, as size increases, there is relative shortening of the rostrum–carapace end line, displaying a negative allometry of this area, and narrowing of the lateral size of the carapace, overall in the infraorbital area. Our results show that in A. pallipes allometry is an important aspect in ontogeny of the carapace anterior portion. Further studies including several populations could be carried out in order to find morphological features characterizing each crayfish population.

Reproduction in the threatened crayfish Austropotamobius pallipes (Decapoda, Astacidae) in the Licenza brook basin (central Italy)

Abstract Austropotamobius pallipes is a vulnerable crayfish, and therefore it is necessary to analyse reproduction in the extant populations. Details of the female annual reproductive cycle in a Mediterranean population are provided for two consecutive years. Maternal-size-related variables and date of collection have been considered in relation to the number of ovarian and pleopodal eggs. Reproductive data from 2587 females collected by hand and traps are reported. In total, 204 (14.69%) and 231 (15.93%) individuals in 2003 and 2004, respectively, were ovigerous. Demonstrable differences exist between ovarian and pleopodal egg counts. In particular, ovarian egg counts were considerably higher than expected pleopodal egg numbers. Mating begins in November and is followed by egg laying in early December–January. Berried females occur until May–June, when hatching occurs. The numbers of both ovarian and pleopodal eggs are correlated with the size of females, although fecundity slightly decreases in larger females. The histology of the reproductive organs of both sexes is also analysed.