New Insight into the Crayfish Procambarus clarkii (Girard, 1852) (Crustacea, Cambaridae): A Morphometric Combined Approach to Describe the Case of a Mediterranean Population

We adopted a morphometric approach to provide statistical support for the description of two different morphotypes (I, reproductive, II, non-reproductive) firstly observed in <i>Procambarus clarkii</i> specimens caught in a population from Sardinia Island (western Mediterranean). The morphometric study was preceded by molecular taxonomic identification using the mitochondrial Cytochrome C Oxidase subunit I (COI) gene. The presence or absence of the pathogen <i>Aphanomyces astaci</i>, responsible for the plague, was also investigated using the ribosomal Internal Transcribed Spacer (ITS) marker. The estimation of the size at onset of maturity (SOM) was further performed in males. Finally, the population structure was examined. Our results confirmed the entirety of the individuals as <i>P. clarkii</i>, and the absence of the pathogen <i>A. astaci</i>. Morphological analysis revealed a significant correlation between chela and carapace lengths, while intra- and inter-sexual dimorphism in the chela length confirmed the occurrence of the two morphotypes. The SOM in males was established between 35.0 and 37.1 mm carapace length. Finally, the size-population structure showed a Gaussian distribution. The recognition of the two distinct morphotypes in the crayfish could be useful as an additional tool not only to identify the reproductive period of this invasive crustacean but also to enrich the guidelines for the correct taxonomic identification of the species.