Studies of male sexual tubes in hermit crabs (Crustacea: Decapoda: Anomura: Paguroidea). III. Morphology of the sexual tube in Catapagurus sharreri A. Milne-Edwards, 1880 (Paguridae)

This study, the third of a multi-part series on male sexual tubes in hermit crabs, the external morphology of the tube of the western Atlantic Catapagurus sharreri A. Milne-Edwards, 1880 is documented using scanning electron microscopy. The male of this species has an unpaired right sexual tube that is long (more than five coxal lengths), and curves externally and upwardly around the pleon, ending at about the mid-dorsal surface of the pleon. The tubes are subcylindrical, flexible, lack a cuticular ridge, and terminate in an opening surrounded by a dorsal beak-like and a ventral rounded lip. Setation on the tubes consist of short, simple, and relatively sparse setae, more numerous near the distal portion of the tube and gonopore. The tube is of cuticular origin, and represents an extension of the calcified right coxa. The morphology of the tip of the tube, with similar to the tip of an elephant trunk, is particularly intriguing and possibly represents a character shared with other species of Catapagurus A. Milne-Edwards, 1880. The tube of C. sharreri is compared with those documented for other species in previous parts of this series, the marine pagurid Micropagurus acantholepis (Stimpson, 1858), and the semi-terrestrial coenobitids Coenobita perlatus H. Milne Edwards, 1837 and C. clypeatus (Fabricius, 1787). The evolution of highly diverse sexual tubes in 63.6% of the genera of Paguridae that are know to have them, continues to raise intriguing questions for