Histological studies of the ovaries of two tropical portunid crabs, Portunus pelagicus (L.) and Scylla serrata (F.)

摘要

The histology of ovaries of adult crabs, Portunus pelagicus and Scylla serrata, were studied and compared using light microscopy, hi general, the histological features, the steps of oogenetic cells and the stages of ovarian development appear similarin the two species. The ovary possesses three to four lobes, and eachlobe is divided into lobules. A thick capsule surrounds the ovarian lobes and its extensions cover and separate each lobule. The lobule is composed of follicles, each containing a cluster of oocytes at different steps within the confinement of connective tissue trabeculae. There are five steps of oogenetic cells, i.e., oogonia (Og) and four steps of oocytes (Oc_1, Oc_2,0%, Oc_4). Og are the earliest germ cells and are located in the center of each lobule. They divide mitotically and move into each follicle where they become Oc_1. Oc, rapidly increase in size, exhibits a clock-face nucleus and basophilic cytoplasm. Oc_2 possess larger nuclei, non-condensed chromatin, a prominent nucleolus and are intensely basophilic. Oc_1 and Oc_2 are previtellogenic and do not contain yolk granules. Oc_3 are larger in size, with a slate grey cytoplasm and contain a few yolk granules. Oc_4 are fully mature oocytes, in possession of completely dispersed chromatin in the nucleus and a very prominent nucleolus. The cytoplasm is eosinophilic due to the presence of numerous yolk granules. The Periodic acid-Schiff reaction and Sudan black stains suggest that Oc_4 also contain large amounts of glycoproteinand lipid in their cytoplasm. The ovarian cycle is divided into four stages, i.e., spawn-spent (stage I), prolifierative (stage II, pre-mature (stage III) and mature (stage IV). Each stage contains different cellular associations: stage I is characterized by the reconfiguration of connective tissue scaffold, plus remnants of unspawned oocytes; stage II contains numerous dividing Og and a few Oc_1 ; stage III contains primarily OC_1, Oc_2, Oc_3; and stage IV contains mostly Oc_4 and small clusters of Og.