The germinal elements were released from twice the peritoneum into the coelomic cavity as mulberry-like clusters of spermatogonia (Figure 3(a)) and all the following divisions occurred in the coelom (Figures 3(b) and 3(c)). The spermatogenesis was not synchronous and all stages of spermatogenesis could be found at any time in the coelom of males (Figure 3(c)). Nevertheless, the frequency of the different stages of the spermatogenesis varied according to the season. Males were considered mature when the proportion of free spermatozoa was high and the proportion of clusters of spermatogonia was negligible. The percentage of mature males was maximal from December to April (between 40 and 93%) indicating that this period corresponded to the most intense reproductive period.

A few isolated mature males were found from June to September (between 20 and 37%) and in November (28%) while no mature males were observed in May and October indicating the presence of a sporadic reproduction.Figure 3Spermatogenesis. (a) Coelomic fluid from a male collected in June showing early germ cells arranged as mulberry-like clusters; (b) clusters of spermatogonia (Sg) and primary spermatocytes (Scy) in the coelomic fluid of a male collected in July; (c) coelomic …3.3. Female Sexual CycleThe examination of histological sections and observation of sexual products allowed us to describe the morphological oocytes aspects at different stages. The ovaries of M. sanguinea were discrete organs present in the posterior segments and consisted of coelomic germ-cell clusters surrounded by a thin envelope of follicle cells (i.

e., sheath cells according to Fisher, 1975) derived from the peritoneum (Figures 4(a) and 4(b)). Clusters were attached to the genital blood vessels (Figure 4(b)). Females usually had two clusters per segment except for the first segments. Oogenesis was of the extraovarian type. Germ cells in premeiotic and previtellogenic phases were observed in one cluster (Figure 4(b)). In each cluster the more differentiated oocytes detached from the ovary and completed vitellogenesis while floating freely in the coelomic fluid (Figure 4(a)). Vitellogenesis took place entirely outside the ovary. Figure 4Ovogenesis. (a) Histological section of a posterior segment of a female collected in March showing ovaries (arrowheads) containing primary oocytes (arrows), oogonia (Oo), free vitellogenic (VOc) and mature oocytes (MOc) in the coelom (Co).

(b) Detail …Oogenesis consisted of a proliferative phase followed by a prolonged growth phase resulting in the production of mature oocytes. During the proliferative Dacomitinib stage oogonia and young oocytes were small (8��m in diameter). Prior to the beginning of vitellogenesis, the oocytes increased in diameter. They began to elongate and measured about 25�C35��m in length.