Oncopagurus cidaris, Lemaitre, 1996

Lemaitre, R., 1996, Hermit crabs of the family Parapaguridae (Crustacea: Decapoda: Anomura) from Australia: species of Strobopagurus Lemaitre, 1989, Sympagurus Smith, 1883 and two new genera., Records of the Australian Museum 48 (2), pp. 163-221 : 204-207

Oncopagurus cidaris n.sp.

Figs 22, 23

Holotype. Male (SL 2.6 mm), off Tully, Queensland, CIDARIS I sta. 1 -3, 18°07.9'S, 147°35.7'E, epibenthic sledge, ORV Franklin , 956-969 m, 6 May 1986, colI. JCU, QM W16596.

Paratypes. QUEENSLAND: 2 males (SL 2.2, 2.7 mm), off Tully, CIDARlS, sta. 16-3, ORV Franklin , 17°47'S, l 48°13'E, epibenthic sledge, ㄱ㐱縱㄰ ㈠ m, 10 May 1986, colI. JCU, QM W16506, 16508 . 3 males (SL 2.4-2.7 mm), 1 female (SL 2.3 mm), 2 females ovig. (SL 2.7, 2.8 mm) offTully, CIDARlS I, sta. 㐹縠 2, ORV Franklin , 17°51'S, 147°lO'E, epibenthic sledge, 904-916 m, 17 May 1986, colI. JCU, QM W16496, USNM 270107 . 3 males (SL 2.6-2.9 mm), 2 females ovig. (SL 2.5, 2.6 mm), same station data as holotype, QM W16596 .

NEW SOUTH WALES: 1 male (SL 3.8 mm), E of Bass Point , FRV Kapa /a, sta. K75-02-16, ㌴뀲㥾㌵❓Ⱐ 151°19~17'E, 439~ 457 m, 30 Jun 1975, AM P20754 . 1 female ovig. (SL 3.2 mm), offNewcastle, NZOI Tangaroa , cruise U223, 1150~ 951 m, 10 Oct 1982, AM P40390 .

Description. Shield (Fig. 22a) as broad as long; dorsal surface weakly calcified on usually more than half of surface, and scattered short setae; rostrum broadly rounded, weakly produced, with short mid-dorsal ridge; anterior margins weakly concave; lateral projections subtriangular, terminating bluntly; anterolateral margins sloping; posterior margin broadly rounded; ventrolateral margins of shield each with small spine. Anterodistal margin of branchiostegite rounded, unarmed, setose.

Ocular peduncles more than half length of shield, with dorsal row of long setae. Cornea width subequal to distal width of ocular peduncle. Ocular acicles subtriangular, terminating in strong spine; separated basally by less than basal width of 1 acicle.

Antennular peduncle long, slender, exceeding distal margin of cornea by entire length of ultimate segment. Ultimate segment twice as long as penultimate segment, with scattered setae. Basal segment with strong ventromesial spine; lateral face with distal subrectangular lobe armed or with 1 small spine, and strong spine proximally. Ventral flagellum with 5 to 6 articles.

Antennal peduncle (Fig. 23a) reaching distal margin of cornea. Fifth segment unarmed, but with scattered setae. Fourth segment with strong dorsodistal spine. Third segment with strong ventromesial distal spine. Second segment with dorsolateral distal angle produced, terminating in strong, simple spine; mesial margin with spine on dorsodistal angle. First segment with I small spine on lateral face; ventromesial angle produced, with 3 to 4 small spines laterally. Antennal acicles slightly curved outward (in dorsal view), at most slightly exceeding distal margins of corneae, terminating in strong spine; mesial margin armed with row of 5 to 9 spines, setose. Flagellum long, exceeding extended right cheliped and ambulatory legs, articles with numerous setae <1 to 3 flagellar articles in length (Fig. 23b).

Mandible with 3-segmented palp. Maxillule (Fig. 23c) with external lobe of endopod weakly developed, internal lobe with 1 long seta. Maxilla with endopod exceeding distal margin of scaphognathite. First maxilliped with endopod exceeding exopod in distal extension. Second maxilliped without distinguishing characters. Third maxilliped (Fig. 23d) with crista dentata of about 8 corneous-tipped teeth; coxa and basis each with 1 tooth mesially. Sternite of 3rd maxillipeds with small spine on each side of midline.

Chelipeds markedly dissimilar. Right cheliped (Fig. 22c,d) massive, with moderately dense, plumose setae on distal half of chela. Fingers curved ventromesially, terminating in small, usually blunt corneous claw; cutting edges with irregularly-sized calcareous teeth. Dactyl slightly shorter than length of mesial margin of palm, set at strongly oblique angle to longitudinal axis of palm; mesial margin broadly curved, well defined by row of blunt or sharp spines diminishing in size distally; dorsal face with scattered small tubercles, ventral face smooth, ventromesial face concave. Fixed finger broad at base, dorsal and ventral faces smooth. Palm longer than broad, lateral margin well delimited by row ofblunt to sharp spines; mesial face rounded, with scattered small tubercles; dorsomesial margin delimited by row of blunt or sharp spines; dorsal surface smooth except for scattered small tubercles; ventral surface smooth. Carpus with dorsolateral margin rounded or sometimes well delimited distally by row of spines; dorsal face with numerous small spines or tubercles; ventromesial margin with row of spines; ventral face with scattered small tubercles. Merus with row of long bristles and scattered tubercles on dorsal surface; ventromesial margin with row of spines. Ischium and coxa unarmed, but with ventromesial row of setae.

Left cheliped (Fig. 22b) usually weakly well calcified on merus and carpus. Fingers terminating in small corneous claw; dorsal and ventral surfaces unarmed except for scattered tufts of setae; cutting edge of dactyl with row of minute, fused corneous teeth; cutting edge of fixed finger with row of regularly spaced, small, evenly-sized teeth. Dactyl shorter than palm in length. Palm unarmed except for scattered setae on dorsal face and long setae on dorsomesial margin; ventral face smooth. Carpus with strong dorsodistal spine; dorsal margin with long setae; ventral face smooth. Merus with long setae on dorsal margin; ventral face smooth. Ischium and coxa unarmed, but with ventromesial row of setae.

Ambulatory legs (Fig. 22 e-g) similar right from left, exceeding extended right cheliped by approximately 0.25 length of dactyl. Dactyl broadly curved, twice as long as propodus, and terminating in sharp corneous claw; with dorsal and dorsomesial rows of long setae, and ventromesial row of about 7 to 9 slender corneous spines. Propodus with row of setae on dorsal margin. Carpus with small, blunt or sharp dorsodistal spine, and long setae dorsally. Merus with setae on dorsal margin. Ischium and coxa unarmed. Anterior lobe of sternite of 3rd pereopods (Fig. 22h) rounded, setose, unarmed.

Fourth pereopod (Fig. 22i,j) semichelate. Dactyl terminating in sharp corneous claw, and longer and more strongly curved in females than in males; with ventrolateral row of small corneous spinules. Propodus longer than broad, rasp formed of 1 row of rounded scales. Carpus with long setae on dorsal margin. Merus with rows of long setae on dorsal and ventral margins.

Fifth pereopod (Fig. 22k) semichelate. Propodal rasp extending to mid-length of segment.

Uropods and telson (Fig. 23h-j) markedly asymmetrical. Telson lacking transverse suture; dorsal surface with scattered setae; posterior lobes separated by shallow cleft, terminal margin of lobes armed with long, often strongly curved corneous spines.

Males lacking 1st gonopods; 2nd pair of gonopods (Fig. 23e-f) weakly developed, asymmetrical, left usually I-segmented or occasionally 2-segmented with short distal segment (Fig. 23e,g), right I-segmented, rudimentary or absent (Fig. 23f). Females with vestigial 2nd right pleopod.

Habitat. Found inhabiting gastropod shells.

Distributiou. Known so far only from Australia. Depth: 439 to 1150 m.

Etymology. The specific name is given in recognition of the fruitful CIDARIS expeditions.

Affinities. This new species superficially resembles 0. tuamotu ( Lemaitre, 1994). The two species differ in several important characters (see Lemaitre, 1994: 407, figs 24-26, 28i). In 0. cidaris , the right palm is distinctly longer than broad, and the ventromesial margin is rounded, unarmed, and the mesial face is not expanded distally (Fig. 22c,d); in 0. tuamotu the palm is broader than long, the ventromesial margin is well delimited by a row of spines, and the mesial face is expanded distally. In the new species the dactyls of the ambulatory legs are more slender (Fig. 22e-g) than in O. tuamotu; the dactyl of the 4th pereopod is longer and more strongly curved in females than in males (Fig. 22i,j), whereas in O. tuamotu the dactyl is similar in both sexes. Although males of both species have asymmetrical 2nd gonopods, those of 0. cidaris are less developed. In males of 0. cidaris , the right 2nd gonopod can consist of a short bud (Fig. 23f), or sometimes is absent; the left 2nd gonopod is two to three times as long as the right, and can consist of one, or occasionally two segments (Fig. 23e,g). In 0. tuamotu, the 2nd gonopods are two-segmented on both sides.

Remarks. In addition to this new species, three other Oncopagurus species also lack 1st gonopods in males, 0. haigae (De Saint Laurent, 1972) O. orientalis (De Saint Laurent, 1972) and 0. tuamotu ( Lemaitre, 1994). This condition in males has evolved in other parapagurid genera as well. Males of five species of Paragiopagurus n.gen. also lack 1st gonopods, P acutus , P bicarinatus , P hirsutus , P hobbiti ( Macpherson, 1983) , and P ruticheles A. Milne Edwards, 1891 , of which only the first three have been found so far in Australian waters.