Alternative mating strategies in male morphotypes of the freshwater prawn Macrobrachium rosenbergii (De Man)

Males in a mature, single-age, pond population of the freshwater prawn Macrobrachium rosenbergii, can be divided into three distinct morphological types, representing three phases in the male developmental pathway (Brody et al., 1980). Behavioral and physical characteristics of all three morphotypes were examined with regard to mating behavior and reproductive probabilities.

Two alternative mating strategies are described. The largest, dominant males actively court and protect the females prior to mating. Males of the intermediate category demonstrate a reduced rate of reproductive activities in the presence of dominant males. The smallest males practice a form of sneak mating consistent with their small size and high mobility. A cost-benefit balance for each particular strategy is offered, based on qualitative features such as morphology and behavioral observations, as well as on quantitative data, including growth rates, relative proportion of each morphotype in the male population, and the respective frequencies of social encounters with females, which result in successful matings, or, in fatal injuries.