Studio sui calamari Loligo vulgaris (Lamarck, 1798) e Loligo forbesii (Steenstrup, 1856) delle acque della Sardegna

This thesis aims to deepening knowledge on the biology and ecology of the two squids Loligo vulgaris (Lamarck, 1798) and Loligo forbesii (Steenstrup, 1856) from Sardinian waters. Considering their socio- economic importance in the Sardinian fisheries, the annual fluctuations in abundance highlighted the possibility of set management measures for their rational exploitation on the base of the knowledge of their life cycle Even if their different preferential bathymetric range, the study of the reproductive process through macroscopic histological and gravimetric analysis of the reproductive systems showed similarities between the two squids both in morphology of the gonads and in the pattern of reproduction. They are similar because they show an extended period of sexual maturity; they have an intermittent spawning with intermediate characteristics between coastal and deep spawning. In particular specific results on the reproductive output of L.vulgaris, showed a potential fecundity of about 4000 eggs (size 0.30-3 mm) and 436 spermatophores (size 7.25-17.37 mm) according to the few studies so far carried out on the species. The reading of the age from the eye lens, tested here for the first time on cephalopods decapods, has allowed to estimate for both species a life cycle of about 18-20 months. For both squids were also performed morphometric analysis of the beaks and calculated specific correlations with the animal size. Considering the taxonomic value of the beak such information may be helpful in studies on diets of predators of these species.