Comparative morphology of the mouthparts, chelipeds and foregut of two kalliapseudid apseudomorphans (Crustacea: Tanaidacea)

Abstract

The mouthparts, chelipeds and foregut of two kalliapseudid apseudomorphan species, Kalliapseudes macsweenyi (subfamily Kalliapseudinae) and Psammokalliapseudes granulosus (subfamily Tanapseudinae), are described and compared using light and scanning electron microscopy. The setae on the mouthparts differ considerably between these two species and are directly related to the feeding mechanism, being in accord with the subfamilial kalliapseudid classification. K. macsweenyi possesses plumose setae on the chelipeds, maxillipedal palps, and mandibular palps. The females of P. granulosus possess simple setae on the chelipeds. The males possess plumose setae on the chelipeds, but are directed ventrally, and thus do not form a filter as in K. macsweenyi. Females and males of P. granulosus possess simple and serrate setae on the maxillipedal palps; the mandibular palp is reduced and bears one serrate seta; and both sexes of P. granulosus possess comb setae on the moveable endite of the maxilla. The mandibles of K. macsweenyi are more heavily calcified and have better developed molar processes than those of P. granulosus. Foregut morphology of these two species is nearly identical and could be attributed to their close phylogenetic relationships on the familial level, or to their similar, chiefly detritus-based diets.