Chanopagurus atopos, 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 : 106-109

Chanopagurus atopos sp. nov.

Figures 1–3

Material examined. Holotype: South China Sea, off Taiwan, 22°14.8´N, 120°02.8´E, 880 m, 29 Jul 2000 ( TAIWAN 2000 station CP 23), National Taiwan Ocean University , Keelung, Taiwan , NTOU H-23a (ovigerous female, SL 6.0 mm).

Description of holotype. Shield ( Fig. 1b) about as broad as long; anterolateral margins sloping; posterior margin truncate; accessory portions extending posteriorly slightly beyond posterior margin, delimited by deep grooves; dorsal surface with numerous tufts of short transverse or oblique rows of setae. Rostral lobe not exceeding lateral projections, broadly rounded. Lateral projections subtriangular, strongly produced and each armed with prominent terminal spine. Branchiostegites calcified dorsodistally; anterodistal margins rounded, setose. Posterior carapace with small calcareous anterolateral tubercle on each side, and small calcified portion adjacent to posterior margin of shield lateral to each cardiac sulcus.

Ocular peduncles ( Fig. 1b–e) short, stout, inflated and nearly contiguous basally, tapering distally; dorsal surface with tuft of few setae medially; dorsomesial margin well defined by low, setose lobes; mesial surface ( Fig. 1d) concave medially, with small setose tubercle submedially. Cornea reduced, surface weakly convex, unpigmented. Ocular acicles ( Fig. 1c) nearly contiguous basally, about 3 times as broad as long, each with very small calcareous spine pointing anteromesially.

Antennular peduncle ( Fig. 1b), when fully extended, overreaching ocular peduncle by 0.5 length of penultimate segment. Ultimate segment about 2.3 times as long as penultimate segment; dorsal surface with short setae. Penultimate segment with few setae dorsally. Basal segment with acute spine on dorsolateral margin. Ventral flagellum with 6 articles. Antennal peduncle ( Fig. 1b) strong and nearly as long as shield length, overreaching ocular peduncles by full length of fourth peduncular segment. Fifth segment nearly twice as long as fourth segment; with setae laterally. Fourth segment with few setae laterally. Third segment with small spine on ventrodistal margin. Second segment with dorsolateral, distal angle produced, terminating in strong simple (left) or bifid (right) spine; dorsomesial distal angle with prominent spine. First segment with small spine at laterodistal margin, and 2 small spines on ventrodistal margin. Acicle long, reaching distal margin of fifth antennal segment; broadly curving laterally (dorsal view), terminating in strong spine; mesial margin with dense, long simple setae. Flagellum relatively short, not overreaching right cheliped; articles with numerous long, simple setae 1–4 times as long as each antennal article.

Mouthparts not dissected. Mandible with incisor edge nearly straight, calcified. Maxillule with external endopodal lobe short, internal endopodal lobe bearing 3 long distal setae. First maxilliped with multiarticulate flagellum. Maxilla with elongate, slender endopod reaching distal margin of adjoining endite. Second maxilliped without distinguishing characters. Third maxilliped with crista dentata ( Fig. 1f) of 13 or 14 corneous-tipped teeth; accessory tooth on inner face of ischium placed submedially; basis with 3 corneous-tipped teeth on mesial margin. Third thoracic sternite (of third maxillipeds; Fig. 1f) with strong corneous-tipped spine on each side of midline.

Chelipeds subequal in length; right slightly longer, stouter. Right cheliped ( Fig. 1g) with dorsal surfaces of carpus and chela covered with numerous tufts or short transverse rows of long, simple, stiff setae. Dactyl and fixed finger weakly curved ventrally, lacking spines; dactyl about as long as mesial margin of palm, terminating in blunt corneous claw; cutting edges each with 2 large, rounded calcareous teeth on proximal half, and row of short, fused corneous teeth distally. Palm about as broad as long, unarmed except for small, setose tubercles on dorsal and ventral surfaces; mesial and lateral margins rounded; ventral surface smooth except for scattered tufts of setae proximally, and long setae near base of fixed finger. Carpus slightly broadened distally; unarmed except for distal dorsomesial spine and low setose tubercles on dorsal surface; ventral surface smooth except for scattered setae. Merus with short transverse rows of setae on dorsal margin; lateral, mesial, and ventral surfaces smooth except for scattered setae; ventral surface with small ventromesial and ventrolateral spines distally. Ischium with scattered setae; ventral surface with small ventromesial and ventrolateral spines distally. Left cheliped ( Fig. 1h) with dorsal surfaces of carpus and chela covered with numerous tufts or short transverse rows of long, simple, stiff setae. Dactyl and fixed finger weakly curved ventrally, each terminating in blunt corneous claw; dactyl about 1.5 times as long as mesial margin of palm; cutting edges each with row of short, fused corneous teeth distally, on fixed finger corneous teeth interspersed with short calcareous teeth. Palm lacking spines; dorsal surface with very small setose tubercles; ventral surface smooth except for long setae near base of fixed finger. Carpus with dorsodistal spine; dorsal surface with weak longitudinal depression; mesial margin strongly sloping; ventral surface smooth except for scattered setae. Merus with short, transverse rows of long setae on dorsal margin; lateral, mesial, and ventral surfaces smooth except for scattered setae; ventral surface with small ventromesial and ventrolateral spines distally. Ischium with scattered setae; ventral surface with small ventromesial and ventrolateral spines distally.

Second and third pereopods ( Figs 2a–d) with meri, carpi, propodi and dactyls having numerous, long stiff setae on lateral and mesial surfaces; meri, carpi and propodi with low tubercles transverse rows of long stiff setae. Dactyls ( Figs 2b, d) broadly curved, each terminating in sharp, corneous claw, about 1.7 (second pereopod) to 1.9 (third pereopod) as long as propodus; with dorsal and dorsomesial distal rows of long setae; with ventromesial row of 3–8 spinules. Propodi lacking spines. Carpi each with dorsodistal spine. Meri lacking spines. Ischia with scattered tufts of setae on lateral face and dorsal margin. Sixth thoracic sternite (of third pereopods; Fig. 3a) with anterior lobe subrectangular, setose, with 6 small subdistal spines. Fourth pereopod ( Fig. 2e) semichelate, with long setae dorsally on merus, carpus, propodus and dactyl. Dactyl subtriangular, terminating in sharp, corneous claw; with ventrolateral row of closely-set corneous spines; no preungual process. Propodus with rasp consisting of single row of ovate scales distally, and 2 rows proximally; lateroventral surface and ventral margin setose. Fifth pereopod ( Fig. 2f) chelate; chela with dense, long setae on dorsal and ventral margins distally. Propodal rasp occupying subtriangular area not reaching midpoint of segment, consisting of small, closely-set rounded scales. Merus and carpus with long setae on dorsal and ventral margins.

Uropods ( Fig. 3c) with left exopod about 3 times as long as broad, somewhat sickle-shaped, and about twice as long as right exopod; rasps of exopod and endopod consisting of small, closely-set rounded scales. Telson ( Fig. 3c) longer than broad, with scattered short setae dorsally; anterior lobes setose distolaterally; with lateral angles of posterior lobes each produced as prominent spine with minute corneous tip; posterior lobes separated by U-shaped median cleft, concave inner margins with 1 (right) or 2 (left) minute, blunt spines.

Female first pleopods ( Fig. 3b) slender, overreaching ventral margin of eighth thoracic sternite (sternite of fifth pereopods); with few short setae distally; segmentation not apparent. Eggs large, diameter about 1.8 mm.

Male. Unknown.

Colour. In preservative, uniformly orangish, with yellowish setae.

Distribution and habitat. Off Taiwan, South China Sea; 880 m; inhabiting a gastropod shell.

Etymology. Atopo s, Greek, meaning out of place, odd, or strange, referring to the unusual characteristics of the ocular peduncles, corneas and ocular acicles.