Egg loss during incubation in Macrobrachium nobilii (Henderson & Mathai)

Abstract

The prawn Macrobrachium nobilii (Henderson & Mathai) is iteroparous, moulting, and breeding once every 20 days. By calculating the carapace/ovary length ratio of a female approaching pre-spawning moult, the number of eggs to be incubated is predicted. Reared at a density of 1♂ aquarium^-1, the ovigerous females incur egg loss throughout the incubation period; 53% of the attached eggs are lost during the 12-day incubation period. On the 3rd day of incubation, as much as 5.8, 19.3, 36.2, and 46.3% of the attached eggs are lost by females reared at densities of 1♂, and 1♀♀ respectively; in the natural habitat > 33 % of the attached eggs are lost by the females carrying 3-day-old eggs. Imbibition of water and the consequent volumetric expansion of eggs, abrasion of eggs during the ventilatory movements of the pleopods, and erosion of individual territories are considered as some possible causes for the observed egg loss.