Mantis shrimp: Olfactory apparatus and chemosensory behavior

Abstract

Mantis shrimp (stomatopods) are known to recognize individuals, but this ability varies with species, with reproductive mode, and with the degree of competition for burrow space. In this chapter, we describe the sensory basis, focusing on chemosensory sensilla (aesthetascs) located on the antennules, that allowed the evolution of the intricate communication system found in stomatopods. The efficiency of these chemosensors is supported by self-generated currents, which mantis shrimp employ to both send and receive chemical information. Multiple behavioral experiments, involving paired aggressive contests or studies of mating pairs, highlight the robust abilities of several stomatopod species to both recognize and remember individual opponents and mates. The extent of these capacities can be understood within the context of each species' social and mating systems. Among the main factors selecting for individual recognition, we identified the limited supply of suitable dwellings and the high possibility of repeated encounters among individuals. These, together with powerful weapons (that could inflict lethal damage) and high site fidelity, have led to the evolution of diverse mating systems, some of which (monogamy, for example) facilitate the evolution of individual recognition. Chemical signaling is essential for this, but it is also employed in other contexts: signals indicate sex but not sexual receptiveness, and some species exploit this fact to deceive and to gain access to burrows during mating encounters. Based on our results we suggest that the signaling mechanisms and chemical recognition systems are highly developed in stomatopods, but might also have evolved in other crustaceans that are exposed to similar selective pressures. We end with a projection of future work, focusing on experiments that could improve our understanding of signaling mechanisms, the role of multimodal signaling, and the opportunity to investigate deception and its role in sexual conflict.