Anisogamy, the bimodal distribution of gametic sizes (smaller in males, larger in females), is a characteristic feature of all sexually reproducing animals. It implies that males have an inherent capacity to produce vast numbers of small and energetically cheap gametes, whereas females can produce far fewer but energetically more expensive eggs. As a consequence, males have more reproductive potentials than the females in terms of producing more offspring. However, the female reproductive success is maximized by the choice of mates that confers material or genetic benefits, whereas male reproductive success is maximized by mating with as many females as possible (Clutton-Brock and Parker, 1992).

The evolutionary effects of anisogamy on mating systems include higher fecundity potential in males than in females, behavioral tendencies in males to seek multiple mates with greater inclination toward polygyny, greater investment by females in postzygotic care of progeny, greater competition for females among males than among females, and the elaboration of secondary sexual traits in males than in females. In Crustacea, the above characteristics influence markedly the formation of different mating systems as well as mating associations.

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