Morphology, Distribution and Comparative Functional Morphology of Setae on the Carapace of the Florida Speck Claw Decorator Crab Microphrys bicornutus (Decapoda, Brachyura)

摘要

Some species of crab are known to “decorate” or attach various materials to their exoskeleton. Little is known about the functional morphology that facilitates such activities. In this study, ultrastructural morphology and distribution of setae on the exoskeleton of the Florida Speck Claw Decorator Crab Microphrys bicornutus were examined using scanning electron microscopy. Eleven morphologically complex structures were identified and mapped on the exoskeleton. Hooked setae were the primary structures used to attach algae to the crab’s body, as confirmed by ablation experiments in which successful decoration by the crab was practically nonexistent. Ten additional setal structures were present, including pappose, cuspidate, connate, plumose, plumodenticulate, two types of serrate, and simple setae. Within the set of these 10 additional setae, two novel types of setae were discovered and possible nomenclature suggested. On the basis of location and the high degree of morphological variation exhibited among these structures, a primary sensory function may be inferred with mechanical decoration playing a minimal role.