HISTOLOGICAL STUDIES OF THE OOGENESIS AND MATURATION OF THE PORTUNID CRAB Portunus pelagicus (L.) IN EGYPTIAN WATERS.

This study is concerned with understanding the process of reproduction and the changes happening in the ovary of Portunus pelagicus during maturation, which would be useful for its broodstock development for hatchery purposes. Results showed that, the ovarian development stages of P. pelagicus females were divided into five stages: immature; early maturing; maturing; ripe and spent.

Introduction

Marine blue swimmer crab Portunus pelagicus is considered the most economical established invasive alien crab species in Egypt, The studies on the structural details of reproductive stages form the base knowledge to perceive the process of its reproduction, which in turn is the primary step toward developing the hatchery technology of P. pelagicus in Egypt.

Material and Methods:

Live female specimens of P. pelagicus collected from Egypt, Alexandria Mediterranean coasts during March 2015-February 2016, and dissected in order to determine the gonad development stages according to Ravi et al. (2013). Gonad lobes were fixed in Davidson solution, then preserved into the 70% alcohol solution, after that dehydrated and moved into cedar oil, embedded in paraffin. Sectioning was at 5 μm, then mounted, and stained with H&E, then examined with Olympus CX 31 light microscope.

Results and Discussion:

The ovarian maturation stages during one reproductive cycle have been classified into five stages included A- Immature stage: Ovary comprised of three different kinds of cells; Og, Oc I and Oc II. Og mean cell diameter were about 11 µm, they are localized in at the center of each follicle moved toward the periphery of the ovary as they grow. Oc I mean cell diameter were about 39 µm. their cytoplasm appeared with highly distinct blue color, while Oc II mean cell diameter were about 57 µm. The cytoplasm was blue and had eosinophilic yolk granules. Supporting follicular cells are present adjacent to Oc I & II (Fig.1.A). B- Early maturing stage: ovaries characterized by the appearance of Oc III. Which had a mean cell diameter about 92 µm. The cyoplasm was slightly eosinophilic. The follicular cells were also found indicating a special microenvironment for them, (Fig.1.B).C- Maturing stage: Oc III were predominant, as they mature to form Oc IV. The developing cells from the germinal zone invaded and formed extension of germinal zone called "germinal nests", this was also observed in the study of Ravi et al. (2013), (Fig.1.C). D- Ripe stage: Ovary was filled with Oc IV (Fig.1.D), which had a mean cell size of 156 µm, where size increased as yolk was developed into the cytoplasm, these results are in agreement with the work of Islam et al. (2010) of the mud crab Scylla paramamosain. The cytoplasm was highly eosinophilic and granular. Lumen and germinal zone were completely absent. E- Spent stage: "spawning" stage, also termed as 'resting' as it was reported by (Fondo et al., 2010), after which most of the completely mature and viable eggs have been released from the ovary. At this stage, the ovary had a large number of spent⁄resorbing oocytes. Visible degeneration of the oocytes occurs, then oogenesis is reinitiated immediately, (Fig.1.E).

References:

1-Fondo, E.N., Kimani, E.N. and Odongo, D.O., 2010. The status of mangrove mud crab fishery in Kenya, East Africa. International Journal of Fisheries and Aquaculture, 2(3), pp.079-086.

2-Islam, M.S., Kodama, K. and Kurokora, H. 2010. Ovarian development of the mud crab Scylla paramamosain in a tropical mangrove swamps, Thailand. Journal of       Scientific Research, 2(2), pp.380-389.

3-Ravi, R., Manisseri, M.K., and Sanil, N.K., 2013. Ovarian maturation and oogenesis in the blue swimmer crab, Portunus pelagicus (Decapoda: Portunidae). Acta Zoologica, 94(3), pp. 291-299.