Chanopagurus, Lemaitre, 2003

Lemaitre, R., 2003, A new genus and species of hermit crab (Crustacea: Anomura: Paguridae) from Taiwan, Memoirs of Museum Victoria 60 (1), pp. 105-110 : 105-106

Chanopagurus gen. nov.

Type species. Chanopagurus atopos sp. nov.

Diagnosis. 13 pairs of quadriserial gills ( Fig. 1a): 2 arthrobranchs on each of third maxillipeds and first to fourth pereopods, 1 reduced but functional pleurobranch on fifth and sixth thoracic somites (above second and third pereopods), and 1 well-developed pleurobranch on seventh thoracic somite (above fourth pereopods). Shield well calcified. Rostral lobe unarmed, not exceeding lateral projections. Cornea lateroventral. Ocular acicle with small spine. Posterior carapace almost entirely membranous. Antennal peduncle with supernumerary segmentation. Maxillule with external endopodal lobe not recurved. Third maxillipeds widely separated basally; ischium with crista dentata well developed, and 1 accessory tooth. Chelipeds subequal in length. Second and third pereopods similar except for slightly longer meri on right pereopods. Sixth thoracic sternite (of third pereopods) divided into anterior and posterior lobes by distinct, membranous hinge. Abdomen not reduced, membranous except for moderately calcified tergite of sixth somite. Tergite of sixth somite with transverse furrow dividing tergite into anterior and posterior portions, each portion having weak, median longitudinal depression. Uropods asymmetrical, left larger than right. Telson symmetrical, with distinct lateral indentations separating anterior and posterior lobes, latter each with “half-moon” contour and blade-like lateral margin. Female with unpaired left gonopore; with paired first and biramous left second to fifth pleopods. Male unknown.

Etymology. This genus is named for Dr Tin-Yam Chan ( NTOU), in recognition of his outstanding efforts to advance our knowledge of the Taiwanese crustacean fauna. The genus name is a combination of his last name with the Greek pagourus meaning crab. Masculine.

Remarks. Chanopagurus is the sixth genus of Paguridae with 13 pairs of quadriserial gills; the others are: Bathypaguropsis McLaughlin, 1994 , Propagurus McLaughlin and de Saint Laurent, 1998 , Tomopaguroides Balss, 1912 , Tomopaguropsis Alcock, 1905 , and Xylopagurus A. Milne Edwards, 1880 . Chanopagurus shares with Propagurus the presence of reduced or moderately well developed pleurobranchs on the fifth and sixth thoracic somites. As in the Pylopaguropsis group of pagurid genera (cf. de Saint Laurent-Dechancé, 1966) Chanopagurus seems to be undergoing an evolutionary process leading to reduction or loss of pleurobranchs similar to that in Propagurus (see McLaughlin and de Saint Laurent, 1998). Chanopagurus shows only homoplastic similarity to Tomopaguropsis , in having species with subequal chelipeds, and numerous setae on the antennal peduncles and flagella, chelipeds and second and third pereopods. Chanopagurus differs from Propagurus and Tomopaguropsis in important characters, for example, the shape and location of the corneas, ocular acicles, number of rows of scales on the propodal rasp of the fourth pereopods, number of female gonopores, number of pleopods in females, and shape of telson. Although reduction of ocular peduncles and corneas has occurred frequently in some Pylochelidae , Paguridae , Parapaguridae , it rarely is accompanied by a shift in the position of the corneas or a change in the shape of the peduncles as seen in this new species. The lateroventral position of the corneas, and concave mesial surface of the ocular peduncles ( Figs 1c–e) in C. atopos , are unique autapomorphies among Paguridae . Although the short ocular acicles, each armed with a very small spine in C. atopos , are unusual among Paguridae , a similar condition does occur in Probeebei mirabilis Boone, 1926 , a highly specialized deep-sea parapagurid ( de Saint Laurent, 1972; Lemaitre, 1998).