Developmental stages of a microsporidian parasite of the white prawn, Penaeus merguiensis de Man 1888

Abstract

A microsporidian parasite found to invade the ovaries of the white prawn, Penaeus merguiensis de Man, 1888, causes the whitening of the mature female gonads. Ultrastructure examination of the white ovaries reveal the presence of spores and other developmental stages of the parasite.

The earliest stage observed is the schizont which contains a few cisternae of endoplasmic reticulum, many ribosomes and a thin plasma membrane. The next stage is the sporont characterized by a pansporoblast membrane, an increase in the amount of endoplasmic reticulum, appearance of more vesicles and of polar filament precursors. Diplokaryotic schizonts and sporonts are also found. Division of the sporonts gives rise to uninucleate sporoblasts. At this stage, the spore organelles start to form and the cell acquires a degree of plarity. The polar filament and the polar sao appear and the sporont membrane complex develops into a sporoblast wall. The sporoblast is transformed into a spore with a polar cap, posterior vacuole, polaroplast, and two laters of spore wall, the exospore and the endospore. The polar filament is a tubular structure consisting of seven coils which after the second coil taper abruptly distally. All these stages of development of the parasite are observed in the infected ovaries within which its life cycle is completed. A probable mode of transmission and life cycle of the parasite is presented.