Abstract:

Macrobrachium asperulum is one of the major freshwater prawn species consumed by residents in Taiwan, China, and therefore is potentially valuable for aquaculture. However, little is known about its reproductive biology. The objective of the present study was to provide a preliminary characterization of the histological structure of the ovary throughout the repro-ductive cycle. Adult M. asperulum was collected in the River Houlong in Miaoli County of Central Taiwan seasonally during December 2007 and September 2008, which represented four seasons of winter, spring, summer and autumn. After sexual de-termination, female M. asperulum was sampled and followed by recording of gravid rate, body weight, and ovarian weight, as well as by determination of gonadosomatic index (GSI) value. Gonadal tissue section was then immediately prepared for his-tological study. The results showed that the highest GSI value was observed in spring while the lowest in winter. The gravid rate of the female prawn reached a maximum of 79.17% in autumn and then dropped sharply in winter. In addition, our results of histological study revealed that the germ cells of M. asperulum could be classified into four different cell types, including oogonia, primary oocytes, secondary oocytes, and mature oocytes, based on differences of size and morphology of cell, chro-matin patterns, and the amounts of lipid droplet and yolk granule. Furthermore, according to the number and type of predomi-nant germ cells presented, the ovarian cycle could be clearly divided into six stages as follows: Stages I and II were prolifera-tive and previtellogenic stages; Stages III and IV were endogenous and exogenous vitellogenic stages; and Stages V and VI were mature and spawn stages.

Key words: reproductive cycle, ovarian development, Macrobrachium asperulum