Use of cytometry for the "reproductive model" assessment of the shrimp Palaemon serratus (Pennant, 1777).

The reproductive biology of the shrimp Palaemon serratus (Crustacea, Decapoda), fisheries resources, has been scarcely studied, especially in the marine habitats of Italian waters. For this purpose, in the present study, monthly samples were taken in brackish waters of the Po River Delta in the North Adriatic Sea. The annual maturative cycle of the ovary was assessed both qualitative, on the basis of histological findings, and quantitative terms, by cytometry. The ovaries feature a proliferative centre from which maturing oocytes branch out in a centrifugal direction. The reproductive period falls between March and June. During the non-reproductive period oocyte diameter ranged from 24 to 153 m, whilst during the reproductive period ranged from 24 to 733 m. The oviposition pattern may be described as “fractioned”, since it is recurrent. In fact, histological and cytometric findings of the Spring catch revealed that the females had both issued eggs that were still attached to the abdomen, as well as oocytes in all stages of vitellogenesis. The size at first maturity was around 51 mm of length.In conclusion, the histo-cytological approach applied throughout the ovary maturation cycle is a good “reproductive model” assessment and an environmental test because the gonadal maturation is closely dependent on enviromental conditions.