Seasonal variations in morphometric features and haemolymph parameters of female and male crabs (Carcinus aestuarii) from the Lagoon of Venice.

In the Lagoon of Venice, fishing and farming of Carcinus aestuarii are important economical activities. Despite this species is widely used in biomonitoring studies, no information concerning seasonal variations in morphometric features and haemolymph parameters of crabs are available in the literature. To fill this gap, in the present study seasonal variations in morphometric features and haemolymph parameters from both male and female crabs were evaluated for the first time. Crabs were collected seasonally (November 2010 to August 2011) in the Lagoon of Venice, and total haemocyte count (THC), haemocyte diameter and volume, haemolymph glucose concentration, total protein levels, and phenoloxidase (PO) and N-acetyl-β-glucosaminidase (NAG) activities were measured. Morphometric features included animal weight, width and length of carapace, and width and length of the bigger chela. Crab moult stage was also determined. All crabs used in this study were in intermoult stage and males were always bigger than females. Two-way ANOVA analysis revealed significant effects of the variable “season” on THC and haemocyte volume, whereas the variable “gender” influenced significantly haemocyte diameter. Season and gender influenced significantly haemolymph glucose concentration, whereas haemolymph protein levels were season-dependent. Haemolymph PO and NAG activities resulted influenced significantly by both season and gender. Two-way ANOVA analysis indicated a significant effect of season on crab morphometric features. Overall, results obtained demonstrated that cellular and biochemical parameters and crab morphometric features varied significantly during the study, depending on both season and animal gender. This aspect should be taken into account when biomonitoring studies are performed with crabs, since seasonal variability in biological responses may influence animal responses to stressors.