Catapaguroides iejimensis, Osawa & Takeda, 2004

Osawa, M. & Takeda, M., 2004, Hermit crabs (Crustacea: Decapoda: Anomura: Paguroidea) from submarine caves in the Ryukyu Islands, south-western Japan, Journal of Natural History 38, pp. 1097-1132 : 1113-1120

Catapaguroides iejimensis sp. nov.

(figures 5–7)

Material examined. H  : NSMT-Cr 14373; male (SL 2.0 mm); Ie Island ; small tunnel near ‘ Shodokutsu’; 26°42.9∞N, 127°50.1∞E; 20 m; 13 October 1990. P    : NSMT-Cr 14374; one ovigerous female (SL 1.9 mm); same data as holotype .

Description. Ten pairs of biserial phyllobranchiate gills, arthrobranchs on third maxilliped to fourth pereopod moderately developed, no pleurobranch on seventh thoracic somite (above arthrobranchs of fourth pereopod).

Shield (figure 5A) as long as or slightly longer than broad; anterior margin between rostrum and lateral projections concave; anterolateral margins slightly terraced; posterior margin roundly truncate; dorsal surface weakly convex, with few tufts of short setae laterally; gastric region weakly calcified. Rostrum broadly rounded, slightly over-reaching lateral projections. Lateral projections moderately well developed, broadly subtriangular, each with small submarginal spine. Accessory portions of carapace narrow, membranous, each with calcified plate along cervical groove. Posterior carapace membranous; posteromedian plate very weakly calcified and bearing scattered short setae in anterior half; cardiac sulci weakly marked, divergent posteriorly in anterior half and convergent in posterior part, not extending to posterior margin; sulci cardiobranchialis extending posteriorly along posterior margin of branchiostegite. Branchiostegites membranous, with few scattered short setae; anterior and dorsal margins unarmed.

Ocular peduncles (figure 5A) slender, subcylindrical, 0.8–0.9 times as long as shield; dorsal surface with row of sparse tufts of short setae mesially; basal portion slightly inflated; lateral face slightly or moderately concave; cornea occupying approximately 0.2 length of peduncle, slightly dilated, semisphere-shaped, pigmented. Ocular acicles subovate, each with small terminal submarginal spine, separated basally by 0.6 basal width of one acicle; dorsal surface slightly convex; lateral margin curved anteriorly; mesial margin bearing short setae.

Antennular peduncles (figure 5A) when fully extended, exceeding ocular peduncles by 0.7–0.8 length of ultimate segment. Ultimate segment elongate, 1.7–2.0 times longer than penultimate segment, somewhat deeper distally, with two long, distally plumose setae on dorsodistal margin; dorsal and ventral surface with few short setae. Penultimate segment with few short setae. Basal segment elongate; statocyst lobe produced laterally, with spine on distolateral margin; ventrodistal margin with few long setae and spine. Upper flagellum (distal part broken in holotype during examination) elongate, 0.8–0.9 times longer than ultimate peduncular segment; lower flagellum reaching to or slightly over-reaching half of upper flagellum.

Antennal peduncles (figure 5A) when fully extended, slightly over-reaching base of corneas or reaching nearly to distal margins, with supernumerary segmentation. Fifth segment with few scattered, moderately long setae. Fourth segment glabrous. Third segment with few long setae and spine at ventromesial distal angle. Second segment with dorsolateral distal angle strongly produced, reaching mid-length of fourth segment, terminating in bifid spine; dorsomesial distal angle with strong spine; mesial margin with short setae. First segment with very small spine on ventrolateral margin distally; ventrodistal margin slightly produced, with small spine. Antennal acicles slender, strongly arcuate, reaching distal margin of fifth peduncular segment and over-reaching base of corneas, each terminating in small spine; mesial and dorsal surfaces with tufts of long setae. Antennal flagella missing.

Mandible (figure 5F) with two small teeth on posterior mesial margin of incisor process, distal segment of palp with several short setae marginally. Maxillule (figure 5G) with subquadrate proximal (coxal) endite; endopod with moderately produced, subtriangular external lobe, internal lobe with one bristle. Maxilla (figure 5H) with endopod reaching anterior margin of scaphognathite. First maxilliped (figure 5I) with endopod 0.3 length of exopod, exopod noticeably inflated proximally. Second maxilliped (figure 5J) with incomplete basis–ischium fusion, exopod elongate. Third maxilliped (figure 5K) slender; carpus and merus unarmed on dorsodistal margin; ischium with crista dentata composed of row of five small corneous teeth becoming larger proximally, no accessory tooth; basis–ischium fusion incomplete; coxa with strong spine at distomesial angle; exopod slender, distinctly over-reaching distal margin of merus.

Chelipeds (figures 6A–E, 7A–D) unequal, right appreciably stronger than left. Right cheliped (figure 6A–E) with dactylus articulating obliquely with palm, propodal–carpal articulation rotated clockwise approximately 30° from perpendicular. Chela subovate in dorsal view, 2.1–2.2 times as long as broad; fingers subequal in length, weakly curved ventrally, with very narrow or no hiatus, each terminating in small corneous claw. Dactylus 0.7–0.8 length of palm, overlapped by fixed finger distally; cutting edge with three widely separated, rounded calcareous teeth; dorsal surface convex, with moderately well-developed, longitudinal roundly crested ridge proximally and numerous tufts of long setae distally; dorsomesial margin drawn out into very weak subacute ridge, armed proximally with prominent spine; mesial surface with tufts of long setae in distal 0.7; ventral surface with moderately welldeveloped longitudinal ridge along mesial margin and tufts of short setae along cutting region. Palm approximately as long as carpus; dorsomesial margin delimited by row of three or four strong spines; mesial surface with few short transverse scales dorsally; dorsoproximal margin with spine in mesial half; dorsal surface of palm and fixed finger convex, palm with very weak longitudinal ridges of short transverse scales each along distal half of dorsomesial margin and midline, median ridge with one or two strong spines proximally, fixed finger with scattered tufts of moderately long setae; dorsolateral margin weakly delimited; lateral surface with several short transverse scales; ventral surface of palm and fixed finger with sparse tufts of short setae, most numerous along cutting region; cutting edge of fixed finger with three or four widely separated, rounded calcareous teeth. Carpus broad, subtriangular in dorsal view, 1.2–1.3 times longer than merus; dorsomesial distal angle with small spine, margin distinctly delimited by row of short transverse scales and one or two spines distally; mesial face with few short transverse scales; dorsal surface with distinct ridge of three or four spines along midline, one spine situated on distal margin; dorsolateral surface strongly sloping ventrally; dorsolateral margin weakly delimited, subacute; lateral and ventral surfaces with few moderately long setae; ventral surface with few rounded tubercles and tuberculate ridges; ventrolateral distal angle with small spine. Merus subtriangular; dorsal surface roundly ridged along midline; dorsodistal margin with spine mesially; ventromesial and ventrolateral margins with few rounded tubercles, each margin with three or four and two distal spines, respectively; ventral surface with few rounded tubercles; surfaces nearly naked except for ventromesial margin bearing numerous long setae. Ischium with or without very small denticle on dorsal surface; surfaces with tufts of short and long setae. Coxa with spine at ventrolateral distal angle. Spines, tubercles and scales each accompanied by tuft of long or moderately long setae.

Left cheliped (figure 7A–D) slender, reaching beyond proximal margin of dactylus of right cheliped; propodal–carpal articulation twisted approximately 45° counterclockwise from perpendicular. Chela 3.1–3.2 times as long as broad, slightly curved laterally; fingers equal in length, moderately curved ventrally, with narrow hiatus, each terminating in small corneous claw. Dactylus 1.4–1.6 length of palm, overlapped by fixed finger distally, with rows of tufts of long or moderately long setae; dorsomesial margin not delimited, unarmed; dorsal and ventral surfaces each with weakly developed, short ridge on proximal part; dorsal surface convex; cutting edge with row of sharply pointed, small corneous teeth. Palm 0.6 times as long as carpus; with regular or irregular rows of tufts of setae, setae becoming longer on mesial and ventral faces; dorsomesial and dorsolateral margins not delimited, unarmed; dorsal surface of palm and fixed finger convex; cutting edge of fixed finger with row of sharply pointed, small corneous teeth. Carpus 0.9–1.0 times longer than merus; dorsomesial and dorsolateral distal angles each with strong spine, margins each with row of few short transverse scales in proximal half and one spine in distal half, dorsolateral proximalmost scale replaced by protuberances (holotype) or spine (paratype); ventrolateral distal angle with small spine; dorsomesial and ventral surfaces with few short transverse scales; lateral surface almost naked. Merus subtriangular; dorsal surface roundly ridged along midline, with few short setae; dorsodistal margin unarmed but with row of moderately long setae; ventromesial margin with small distal spine and rounded proximal tubercle; ventrolateral margin with two spines in distal half; mesial and lateral surfaces almost naked; ventrolateral margin with long setae. Ischium with or without very small denticle on dorsal surface; ventral surface with moderately long setae. Coxa with spine each at ventromesial and vetrolateral distal angles. Spines, tubercles and scales each with tuft of long or moderately long setae.

Second and third pereopods (figure 7E–I) generally similar from left to right, right propodi slightly longer than those of left; elongate; over-reaching tip of right cheliped by nearly entire length of dactyli. Dactyli 1.3–1.5 times as long as propodi in second, 1.6–1.9 times as long in third, slender, strongly or moderately strongly curved ventrally in lateral view, slightly twisted in dorsal view, each terminating in long, slender corneous claw; lateral and mesial surfaces with few short setae along dorsal and ventral margins; dorsal margins each with row of long setae, distal setae stiff; ventromesial margins each with row of five or six small, slender corneous spines and sparse long setae. Propodi 1.2–1.4 times longer than carpi, each with one or two elongate corneous spines (spines of holotype larger than paratype) and few short setae at mesial ventrodistal angle; lateral and mesial surfaces naked; dorsal and ventral surfaces with widely spaced, sparse tufts of short and long setae. Carpi 0.6–0.8 length of meri, with spinule near dorsodistal angle on second but unarmed on third (right second of holotype unarmed, left third of paratype with spinule); lateral and mesial surfaces naked; dorsal and ventral surfaces with sparse tufts of short and long setae. Meri and ischia each unarmed but with widely spaced tufts of long setae on dorsal and ventral surfaces; lateral and mesial surfaces naked. Coxae unarmed; left third pereopod of female with gonopore.

Fourth pereopods (figure 7J) semi-chelate, with scattered tufts of short and long setae marginally. Dactylus weakly curved, with row of tiny corneous teeth on ventral margin, no preungual process at base of terminal claw. Propodus with slightly convex ventral margin; propodal rasp composed of single row of small ovate or lanceolate, corneous scales present on distal half of ventral margin. Carpus unarmed on dorsal surface.

Fifth pereopods chelate. Right coxa of male (figure 5L) with long sexual tube, directed from right to left under thorax, reaching considerably beyond left coxa, nearly straight but very slightly recurved anteriorly in distal part, terminating in narrow but bluntly pointed apex and bearing short setae distally. Left coxa with very short sexual tube, partially obscured by setae arising from surface of eighth thoracic sternite.

Third thoracic sternite unarmed on anterior margin. Sixth thoracic sternite (figure 5B, C) with roundly subtrapezoidal (holotype) or semicircular (paratype) anterior lobe bearing pair of small spines and long setae on anterior margin. Eighth thoracic sternite (figure 5L) developed anteriorly as two somewhat flattened, subovate lobes separated by shallow median depression, with dense long setae on surface.

Abdomen well developed, coiled. Male with three unpaired, unequally biramous, left pleopods on third to fifth abdominal somites (fourth pleopod missing during examination); all pleopods subequal in size; each endopod 0.3–0.4 length of exopod. Female with four unpaired biramous, left pleopods on second to fifth abdominal somites, second to fourth pleopods well developed, subequal; fifth pleopod smaller than preceding; second and third pleopods each with endopod subequal in length to exopod, fourth and fifth pleopod each with endopod 0.6 length of exopod. Uropods distinctly asymmetrical.

Telson (figure 5D, E) with weakly marked transverse identations on lateral margins; strongly or moderately asymmetrical posterior lobes separated by moderately deep median cleft; terminal margins oblique, each with two or three small spines and obtusely (holotype) or acutely (paratype) pointed lateral angle; lateral margins each delimited by chitinous plate.

Colour. There are no spots, band or stripes on the straw ground colour in the preserved specimens examined.

Habitat. No detailed data.

Etymology. The species name is derived from the collection locality, Ie-jima (Ie Island) of the Ryukyu Islands.

Remarks. In the key to species of Catapaguroides provided by McLaughlin (2002a), this new species keys to C. karubar McLaughlin, 1997 . These two species share the unarmed left chela, but are clearly distinguished from each other by the shape of the ocular peduncles, right chela and anterior lobe of the sixth thoracic sternite.

Catapaguroides iejimensis appears most closely allied to C. foresti McLaughlin, 2002a from Guam and C. kasei sp. nov., described below, in having a broad, subtriangular carpus of the right cheliped (dorsal view), subovately shaped right chela and completely unarmed left chela. However, C. iejimensis is immediately distinguished from the latter two species by having slightly dilated and semisphereshaped corneas of the ocular peduncles and two or three spines proximally on the dorsal surface of the palm of the right cheliped. Catapaguroides foresti and C. kasei have reduced and cone-shaped corneas and no spines on the dorsal surface of the palm of the right cheliped, respectively.

A broad subtriangular carpus of the right cheliped is also seen in C. cristimanus de Saint Laurent, 1968 and C. karubar , both from Indonesia, and C. hooveri McLaughlin and Pittman, 2002 from Hawaii. However, the shape of the right chela immediately distinguishes C. cristimanus and C. karubar from both C. iejimensis and C. kasei . The chela is subcircular-shaped (dorsal view) and sharply crested on the dorsolateral margin in the former two species, whereas it is subovately shaped in the latter two species. Catapaguroides hooveri differs from both C. iejimensis and C. kasei by having a faintly crenulate or somewhat spinulose dorsomesial margin of the dactylus of the right cheliped and two small spines on the dorsomesial margin of the palm of the left cheliped. In the latter two species, the dactylus of the right cheliped has only a single prominent, spine or spinulose protuberance proximally on dorsomesial margin and the palm of the left cheliped is completely unarmed.

Catapaguroides iejimensis also resembles C. fragilis (Melin, 1939) from the Ogasawara Islands and Mururoa, and C. melini de Saint Laurent, 1968 and C. declivis McLaughlin, 1997 , both occurring in Indonesian waters, in having a row of spines on the dorsomesial margin of the palm of the right cheliped, one or two spines or tubercles near the proximal margin in the mesial half of the dorsal surface, and no spines or tubercles on the dorsodistal region. However, it differs from the latter three species in having one or two spines proximally on the dorsomedian ridge of the right palm. The armature of the left cheliped also distinguishes C. iejimensis from C. fragilis , C. melini and C. declivis . Catapaguroides iejimensis is unarmed on the dorsomesial margin of the palm, whereas C. fragilis , C. melini and C. declivis have all been described as having spines on the margin (one or two spines in C. fragilis , a row of spines in C. melini and two or three spines in C. declivis ). On the dactylus of the right cheliped, a crested proximal ridge on the dorsal surface is observed in both C. iejimensis and C. declivis , whereas a distinct spine on the dorsomesial proximal margin is seen in both C. iejimensis and C. fragilis . However, the shape of the anterior lobe of the sixth thoracic sternite is quite different in C. iejimensis . Catapaguroides iejimensis has a roundly subtrapezoidal or semicircular lobe with a pair of small spines, whereas C. melini and C. declivis possess a broadly subsemicircular or roundly rectangular, marginally unarmed lobe (in C. melini , judged from the figure by de Saint Laurent, 1968: 931, figure 10). The more slender ocular peduncles and the weakly armed terminal margin of the telson also distinguish C. iejimensis from C. declivis .

The ovigerous female of Catapaguroides iejimensis (NSMT-Cr 14374) carried large eggs in comparison with its body size, and the number of the eggs is rather small (0.4–0.5 mm in diameter, approximately 40 in number). This suggests an abbreviated mode of development in this species.