Revealing the Shamefaced Crab Calappa granulata (Crustacea: Brachyura) from the Adriatic Sea, Northern Basin of the Mediterranean

This study presents the first data on morphometry, length-weight relationship, diet, reproductive biology, epibionts and genetic identity of the shamefaced crab Calappa granulata from the central eastern Adriatic Sea. A total of 92 crabs were collected during 2011, 2014 and 2015, of which 64 were females and 28 were males. Overall, 11 morphometric characteristics were measured. Carapace length of sampled individuals ranged from 48.46 to 76.09 mm, and body weight from 47.06 to 221.39 g. The length-weight relationship showed negative allometry for males and isometric growth for females. Analysis of the stomach content revealed the crab's preference for crustaceans (20.28%) and cephalopods (10.58%), less for fish (3.4%) and shellfish (0.28%). Size at first sexual maturity (CL50%) of 59.25 and 66.92 mm was estimated for males and females, respectively. Epibiotic serpulid polychaetes were recorded on the crab exoskeleton with an overall prevalence of 29.3%. Analyses of a partial sequence of mtCOI showed high haplotype (Hd = 0.964) and low nucleotide diversity (pi = 0.00598). Phylogenetic inference and estimation of population differentiation (F-ST = 0.013, p = 0.271) with publicly available Mediterranean sequences currently imply one homogenous population unit. To the best of our knowledge, these are the first nucleotide sequences of C. granulata from the Adriatic Sea made publicly available.

Automated summary

This study provides the first comprehensive data on the characteristics, biology, and genetics of the shamefaced crab Calappa granulata from the central eastern Adriatic Sea. The study reveals the crab's dietary preferences, size at first sexual maturity, and presence of epibiotic polychaetes. The analysis of genetic sequences also suggests a homogenous population in the Adriatic Sea.