Sex Reversal and Fighting Behavior: Coevolved Phenomena in a Tanaid Crustacean
1983
Highsmith, Raymond C.
The intertidal, sand—dwelling crustacean Leptochelia dubia (Tanaidacea), living at an average density >50 000 individuals/m², was found to be protogynous. Sex reversal occurs rapidly and is evidently environmentally determined. Similar to a number of coral reef fishes, protogyny in L. dubia appears to be an integral component of a mating system in which the presence of males inhibits sex reversal and males fight for females. This is the first report of fighting behavior in the order Tanaidacea. Fighting is stereotyped in L. dubia, and the components of this behavior are described. Large males always won fights with smaller males, and males occupying mucous tubes or holes usually won fights against equal—sized intruders. Males were not physically harmed during fights, but losing a fight may increase a male's risk of mortality from other sources. As males are unable to feed or grow, all but the smallest males are derived from females that have reversed sex. Because females tend not to reverse sex when males are present and males have high mortality rates (those not dying from other causes ultimately starve). <5% of the population is male. Because females brood, the rate of population increase is a function of the proportion of females in the population. An advantage of this life history with its higher maximum rate of population increase is that a high density of females, which are facultative predators on larvae and juveniles of potential superior space competitors, is maintained.
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