Structure and Function of Cuticular Sensilla of the Lobster Homarus Americanus

Abstract

Chemosensory neurons and mechanosensory neurons innervate all the cephalothoracic appendages of the lobster Homarus americanus, including the antennules, antennae, six pairs of mouthparts, and five pairs of pereiopods. The structure and sensory function of sensilla on these appendages are described. Sensilla on the pereiopods and maxillipeds can be classified morphologically and physiologically. Smooth setae and squamous setae are the primary setal types in the rows and tufts of hairs on the walking legs; they also are found on the maxillipeds and, less abundantly, on the crusher and seizer claws. Serrate setae are common on the maxillipeds and the third and fourth walking legs. Hedgehog hairs are located on the cutting edges of the claws of the first two pairs of walking legs and on apposable cuticular surfaces on the last two segments of the fourth pair of walking legs. All four of these types of sensilla are both mechano- and chemosensitive. Sensilla sensitive to mechanical but not to chemical stimuli include peg sensilla, which are small sensilla situated in articulated sockets within cuticular depressions and are distributed over the surface of the carapace, pereiopods, and maxillipeds. Other mechanoreceptive sensilla include cuticular articulated peg organs (=CAP organs), located on the pereiopods and on the third maxillipeds, and campaniform sensilla, found on the antennae and antennules. Exclusively chemosensory sensilla were not found.