Ovary development of the red shrimp, Aristeus antennatus (Risso, 1816) from the northwestern Mediterranean Sea

The present work reviews the previous reproductive studies on red shrimp, Aristeus antennatus, and is initially based on those. Subsequently, we propose a reduction in the number of stages distinguished in macroscopic gonadal classification, in an attempt to correlate the microscopic characteristics observed with each macroscopic stage recognized. Macroscopic and microscopic characteristics of the stages of ovarian maturity of the red shrimp are reported, with special attention to the relationship between the general appearance of the ovary and the histology of ovarian tissues. Six different stages of ovarian development can be defined according to the relationship between the general appearance of the ovary, the histology of the ovarian tissues, and the gonadosomatic index. They constitute a reliable guide for judging maturation stages. Previtellogenic oocytes correspond to nucleolar and perinuclear chromatin oocytes. Endogenous vitellogenesis starts on perinuclear oocytes, in cysts located at the periphery of the ovarian lobe. Exogenous vitellogenesis starts just after the onset of folliculogenesis, the coloration appearing when follicle cells surround the oocytes. Following initial oocyte growth, follicle cells move from the germinal epithelium into the growth zone, attach to the periphery of each oocyte, and surround it. The final stage of the ripe ovary shows that developing oocytes mature synchronously, with only one spawning event for each individual shrimp taking place in each reproductive season. The exogenous vitellogenesis process of ovarian maturation seems to be induced by spermatophore attachment, since gonad weight increases after a spermatophore is attached. Only a few individuals with spent ovaries were detected and this may indicate that females move to other zones or even to deeper waters just before spawning. Variability in the onset and the duration of the reproductive cycle has been recorded between reproductive years, to account for environmental variability.