Mating Behavior and Strategies

Given the variation in size, form, and habitats of shrimp species, it shouldn't be too surprising that there is considerable variation in the way that males and females find each other, court and mate. The suite of ecological, morphological, and behavioral adaptations which have co-evolved to assure successful mating are known as mating "strategies" by evolutionary biologists. In some shrimp species, males are as big or bigger than females, have large claws, and are aggressive. They find females before they molt (when mating takes place in most caridean shrimps) and defend them from other males, thus insuring that they will inseminate the female.

However, in many other species, males are small (allowing them to hide easily from predators) and not particularly aggressive. Females are larger (a bigger female produces more eggs).

In two such species studied, Sicyonia dorsalis (a penaeoid) and Palaemonetes pugio (a caridean), time-lapse video observations showed that males do not recognize nor guard females that will soon molt and be ready to mate. Rather, their "strategy" is simply be "socially active," increasing the chances of encountering a just-molted, sexually receptive female. When one is encountered, recognition and mating occurs within seconds, and the mating partners separate quickly (see Bauer, 1996a for S. dorsalis, Bauer & Abdalla, 2000 for P. pugio). This has been called a "pure search" or "scramble competition" type of mating strategy [see also Heptacarpus sitchensis (= pictus), Bauer, 1976]. Although the male is not assured of a mating, as are males of species which guard premolt females, he does not have to invest a lot of energy in growth or defense of the female, and exposure to predators is reduced.  In P. pugio, it appears that a pheromone is released about an hour before her mating molt, stimulating nearby males to a more active search pattern (Bauer & Abdalla, 2000).

In order to understand mating systems, one must understand the basic breeding biology of the species. This work, which is as interesting and rewarding as experiments on mating systems, has revealed the relationship between mating, molting, spawning, mechanics of actual mating, and sex attractants (pheromones) in various species (see Bauer 1996a,b, 1992a, 1991a,b, 1986, 1979a, 1976; Bauer & Cash, 1991; Bauer & Min, 1993, Bauer & Holt, 1998). Research is needed on these topics, especially on pheromones.

References Cited

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