title: Discovery of a new species of hermit crab of the genusPylopaguropsisAlcock, 1905 from the Caribbean: "den commensal" or "cleaner"? (Crustacea, Anomura, Paguridae).
abstract: A new secretive, yet brightly colored hermit crab species of the family Paguridae,Pylopaguropsis mollymulleraesp. n., is fully described based on specimens from the reefs of Bonaire, Lesser Antilles, southern Caribbean Sea. Populations of this new species were discovered and photographed in the Bonaire National Marine Park under a large coral ledge, at a depth of 13.7 m, living in crevices known by scuba divers to serve as den to a pair of "flaming reef lobsters"Enoplometopus antillensis, or a "broad banded moray"Channomuraena vittata. This new species is only the second species ofPylopaguropsisAlcock, 1905 known from the western Atlantic, the 20thnamed worldwide, and belongs in theteevanagroup of species of the genus. It is remarkably similar, and herein considered geminate, to the tropical eastern Pacific congener,Pylopaguropsis teevana(Boone, 1932), the two being characterized and uniquely different from all other species of the genus, by the striking and deeply excavated, scoop-like ventral surface of the chela of the right cheliped. Minor differences separate this new species fromPylopaguropsis teevanain the relative length of the antennal acicles (exceeding the corneas versus not exceeding the corneas inPylopaguropsis teevana); dorsal armature of the right chela (smooth or with scattered minute tubercles versus with numerous small tubercles inPylopaguropsis teevana); surface shape of the lateral face of the dactyl of right pereopod 3 (evenly convex versus flattened inPylopaguropsis teevana); and coloration (red bright red stripes versus brown stripes inPylopaguropsis teevana). The highly visible color pattern of bright red stripes on white background typical of decapods known to have cleaning symbioses with fish, dense setation on the flagella of the antennae, and preference for a crevicular habitat, combined with brief in situ nocturnal observations, suggests the possibility thatPylopaguropsis mollymulleraesp. n. engages in "cleaner" activities or functions as a "den commensal" with moray eels. The morphology and possible meaning of the observed behavior is discussed. A tabular summary of the distribution, habitat, and published information on all species ofPylopaguropsisis presented. Supplemental photographs and a video of livePylopaguropsis mollymulleraesp. n.are included.
authors.affiliation: Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, 4210 Silver Hill Road, Suitland, MD 20746, USA.
authors.forename: Rafael
authors.initials: R
authors.lastname: Lemaitre
keywords: Bonaire; Caribbean; Paguridae; Pylopaguropsis; hermit crab; new species; “cleaner”; “den commensal”