Influence of a putative male pheromone on ovarian maturation and ovulation in the freshwater prawn Macrobacterium rosenbergii (de man, 1879)

Abstract

Discovery of a male primer sex pheromone with a specific stimulatory effect on ovarian maturation and ovulation in the small sized freshwater shrimp Paratya compressa and the prawns Macrobrachium kistnensis and M. idella is considered very significant. In this context, it was the objective of the present study to investigate this aspect in the commercially important giant freshwater prawn Macrobrachium rosenbergii (de Man 1879). Two sets of experiments were carried out using sexually mature females and blue claw males collected from wild. The first experiment (to study the effect of male deprivation on ovarian maturation) had two groups of females. Group I had isolated females (without males) and group II had females cohabiting with males. Ovarian maturation was monitored daily for 60 days. Maturity stages and the number of berried females were noted and average spawning frequency calculated. There was no difference in the percentage of berried females and average spawning frequency between the two groups and hence no evidence for blocked ovarian maturation in isolated females due to the lack of a male factor. The second experiment was done to delineate the role of visual and/or chemical cues on ovarian maturation in M. rosenbergii. Specially designed glass aquaria were used which had three compartments for three groups of females. Group I females were isolated and received only visual signals and no chemical cues from the males. Group II females were cohabiting with males. Group III females were also isolated from males but received only chemical cues from males through a common water circulation. The same parameters as in the first experiment were monitored for 60 days and no significant difference found between the three groups. Histological study also showed normal maturation. The conclusion is that there is no evidence for an ovary stimulating pheromone in M rosenbergii thus adding one more feature to the distinctiveness of this species.