Chemical communication in peracarid crustaceans

Abstract

Chemical communication plays an important role during the life of peracarid crustaceans, where the two main taxa, the amphipods and isopods, have representatives in both aquatic and terrestrial habitats. As in other crustaceans, the antennae bear the most important chemosensory structures, which are used for food-finding, predator detection and intraspecific interactions. The chemical nature of peracarid pheromones is unknown, but numerous experimental studies confirm that chemical signals can be soluble/volatile or contact pheromones. Waterborne chemicals mediate mate finding while contact pheromones are mainly involved in mate assessment. Males of some species appear capable to determine the reproductive status of females (closeness to the reproductive molt), which is possibly mediated by chemical compounds. Contrasting with this fine-tuned chemoreception in male-female interactions are other examples that suggest that reproductive isolation between closely related congeneric species is incomplete. The fact that males form precopulatory associations with heterospecific females indicates that chemicals mediating these interactions are not sufficiently specific to permit species discrimination. Gregarious behavior in many species is also guided by chemical cues that lead to aggregation on shared food sources or in communal shelters. Studies on kin recognition in mother-offspring groups have produced ambiguous results - in some species females appear unable to discriminate between their own and unrelated offspring, while females of other species recognize their own juveniles. The best example for kin recognition comes from desert isopods where family-specific chemical signatures allow parents to recognize their offspring. In summary, there is abundant experimental and observational evidence that numerous intra- and interspecific interactions in peracarids are mediated via chemical stimuli, but knowledge about the chemical structure of these compounds is still very limited. Given that all species have direct development and that many species can be easily cultured in the laboratory, peracarid crustaceans are proposed as ideal model organisms for studies aiming at the identification of the compounds used in chemical communication.