Discovery of a new species of hermit crab of the genus Pylopaguropsis Alcock, 1905 from the Caribbean: "den commensal" or "cleaner"? (Crustacea, Anomura, Paguridae).

Rafael Lemaitre

doi:10.3897/zookeys.646.11132

Rafael Lemaitre

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https://doi.org/10.3897/zookeys.646.11132

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A new secretive, yet brightly colored hermit crab species of the family Paguridae, Pylopaguropsis mollymullerae sp. 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 of Pylopaguropsis Alcock, 1905 known from the western Atlantic, the 20th named worldwide, and belongs in the teevana group 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 from Pylopaguropsis teevana in the relative length of the antennal acicles (exceeding the corneas versus not exceeding the corneas in Pylopaguropsis teevana); dorsal armature of the right chela (smooth or with scattered minute tubercles versus with numerous small tubercles in Pylopaguropsis teevana); surface shape of the lateral face of the dactyl of right pereopod 3 (evenly convex versus flattened in Pylopaguropsis teevana); and coloration (red bright red stripes versus brown stripes in Pylopaguropsis 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 that Pylopaguropsis mollymullerae sp. 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 of Pylopaguropsis is presented. Supplemental photographs and a video of live Pylopaguropsis mollymullerae sp. n. are included.

Highlights

The genus Pylopaguropsis Alcock, 1905, currently includes a group of 19 morphologically striking species that typically live in hard bottoms on or near coral reefs, and at depths ranging from the subtidal to the upper continental slope (0–610 m)
The only differences detected between these two species are minor, as follows: the antennal acicles slightly exceed the corneas, whereas the acicles do not reach the distal margin of the cornea in P. teevana; the dorsal surfaces of the right chela is smooth or with only scattered minute tubercles on the lateral half, whereas the same surfaces have numerous albeit well-spaced small tubercles in P. teevana; and the lateral face of the dactyl of right pereopod 3 is evenly convex, whereas the lateral surface is slightly flattened in P. teevana
The morphological similarity of this new species with the eastern Pacific congener, P. teevana, is so remarkable that there is little doubt the two are closely related and geminate species that have barely diverged since the complete ocean separation by the central American isthmus

Summary

Introduction

The genus Pylopaguropsis Alcock, 1905, currently includes a group of 19 morphologically striking species that typically live in hard bottoms on or near coral reefs, and at depths ranging from the subtidal to the upper continental slope (0–610 m). Telson (Fig. 1E) with distinct lateral indentations separating anterior and posterior lobes; posterior lobes subtriangular, nearly symmetrical, separated by deep, narrow median cleft, distal margins armed with row of small, sharp spines and blunt laterodistal angle.

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