Ultrastructure and histochemistry of the male reproductive system of the genus Callinectes Stimpson, 1860 (Brachyura: Portunidae)

Abstract

We described the ultrastructure and histochemistry of the reproductive system of five Callinectes species, and evaluate the seasonal variation in weight of the reproductive system and hepatopancreas by comparing annual changes of somatic indices. The somatic indices changed little throughout the year. In Callinectes, spermatogenesis occurs inside the lobular testes and, within each lobule, the cells are at the same developmental stage. Spermatogenesis and spermiogenesis follow the same development pattern in all Callinectes studied. Mature spermatozoa are released into the seminiferous ducts through the collecting ducts. Cells of the vas deferens are secretory as evidenced by rough endoplasmic reticulum, Golgi complex, and secretory vesicles that produce the seminal fluid. The anterior vas deferens shows two portions: proximal and distal. In proximal portion (AVDp), spermatozoa are clustered and embedded in an electron-dense, basophilic glycoproteinaceous secretion Type I. In the distal portion (AVDd), the spermatophore wall is formed by incorporation of a less electron-dense glycoproteinaceous secretion Type II. The secretion Type I change to an acid polysaccharide-rich matrix that separates the spermatophores from each other. The median vas deferens (MVD) stores the spermatophores and produces the granular glycoproteinaceous seminal fluid. The posterior vas deferens (PVD) has few spermatophores. Its epithelium has many mitochondria and the PVD seminal fluid changes into a liquid and homogeneous glycoprotein. Many outpocketings in the PVD and MVD help to increase the fluid production. Overall, the reproductive pattern of Callinectes is similar to other species that produce sperm plugs. The secretions of AVD, MVD, and PVD are responsible for the polymerization that forms the solid, waxy plug in the seminal receptacle. The traits identified here are common to all Portunidae species studied so far.

Morphometric, Histochemical, and Ultrastructural Analysis of the Reproductive System and Spermatogenic Stages of Male Blue Crab (Callinectessapidus Rathbun, 1896)

“…The gonadosomatic index (GSI) of the crabs obtained in this study suggests that reproduction is likely to increase significantly in spring compared with winter and summer but similar in all to autumn. These results were contrary to the previous findings in closely related species, including Callinectes ornatus, Callinectes danae, and Callinectes bocourti collected from Sao Vicente Bay/Estuary Complex [16], where the GSI was similar across the different seasons, an indication of continuous reproduction. In addition, Sant'Anna, Turra [40] reported continuous reproduction for C. ornatus and C. danae in the Santos-Sao Vicente Estuary/Bay complex.…”

“…In S. philippina [46], spermatophore formation occurs in the distal AVD rather than at the junction to the testes, as in C. opilio [48]. The sperms in AVD were compacted into irregular triangular-like shapes surrounded by two epithelial secretions, and this was in agreement with previous findings in the same species [16,43]. The spermatozoa were surrounded by epithelial secretions of the AVD that consolidate the sperm mass and build the non-cellular spermatophore wall layers in the testes, where spermatophore formation starts into the vas deferens.…”

“…The testes were lobular with highly compacted seminiferous tubules. It is believed that the spermatozoa are transported into the vas deferens through these tubules [16]. Four consecutive gonadal differentiation stages (immature, maturing, mature, and spawning) were observed for Callinectes sapidus in agreement with previous findings [45].…”

“…Our findings further showed that the vas deferens encases the spermatozoa in spermatophores, shielding them from desiccation and microbial infection. As reported in a previous study [43] and in other Callinectes species, such as Callinectes danae [47], and C. ornatus [16], the transverse parts of AVD in this study revealed the presence of spermatophores, which were irregular triangular-like shapes surrounded by two epithelial secretions. In S. philippina [46], spermatophore formation occurs in the distal AVD rather than at the junction to the testes, as in C. opilio [48].…”

“…It is divided into spermatids and eventually into sperm cells [14]. Mature sperms are then transported through the vas deferens and encapsulated into spermatophores [15,16]. Generally, there are few ultrastructural reports in some of the decapods [17,18].…”