Alainopaguroides sinensis, Han, Yuan-Yuan, Komai, Tomoyuki & Sha, Zhong-Li, 2016

Han, Yuan-Yuan, Komai, Tomoyuki & Sha, Zhong-Li, 2016, A new species of the hermit crab genus Alainopaguroides McLaughlin, 1997 (Crustacea: Decapoda: Anomura: Paguridae) from the South China Sea, Zootaxa 4173 (6), pp. 569-576 : 570-575

publication ID	https://doi.org/ 10.11646/zootaxa.4173.6.4
publication LSID	lsid:zoobank.org:pub:6C3BA513-1BB3-4F1C-B3B6-3ACE72DD377D
DOI	https://doi.org/10.5281/zenodo.6062916
persistent identifier	https://treatment.plazi.org/id/03E70B71-FFDE-2B5C-FF5F-C6021C298663
treatment provided by	Plazi
scientific name	Alainopaguroides sinensis
status	sp. nov.

Treatment

Alainopaguroides sinensis View in CoL sp. nov.

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined. Holotype: MBM 059852 View Materials , ovigerous female (SL 2.4 mm), E of Hainan Island South China Sea, 19°30'N, 111°30'E, 110 m, mud-sandy bottom, RV 171, station 6121, beam trawl, coll. Xiu-Tong Ma, 26 January 1959 GoogleMaps .

Description. Shield ( Fig. 1 View FIGURE 1 a) 1.1 times wider than long, vaulted; anterior margin between rostrum and lateral projections concave; posterior margin roundly truncate; dorsal surface convex, with scattered tufts of short setae either side of midline and lateral parts; and with shallow depression somewhat posterior to each anterolateral projection. Rostrum broadly rounded. Lateral projections overreaching as far as rostral lobe, each with marginal spines directed anterolaterally.

Ocular peduncles (including corneas) ( Fig. 1 View FIGURE 1 a) short, about 0.6 length of shield, narrowed basally, widened distally, with corneas well dilated; corneal width about half length of ocular peduncle; dorsal surfaces each with row of setae along base of cornea and one tuft of minute spiniform bristle medially. Ocular acicles relatively short, triangular, terminating in slender spine, 0.2 length of ocular peduncles (including corneas), widely separated basally by broad inter-ocular lobe; dorsal surfaces flat.

Antennular peduncles ( Fig. 1 View FIGURE 1 a) overreaching distal corneal margins by approximately 0.5 length of penultimate segment. Ultimate segment 1.6 times as long as penultimate segment, with short setae distally on dorsal surface. Penultimate segment with few scattered setae. Basal segment subequal in length to penultimate segment, with small spine at ventrodistal angle and subdistal spine on lateral margin; statocyst lobe weakly inflated.

Antennal peduncles ( Fig. 1 View FIGURE 1 a) overreaching distal corneal margins by entire length of fifth segment. Fifth segment with sparse, moderately long setae. Fourth segment unarmed, with few setae. Third segment with spinule on ventrodistal margin. Second segment with dorsolateral distal angle produced, and terminating in slender spine; lateral margin with sparse tufts of long setae; dorsomesial distal angle with small spine. First segment with prominent spine on lateral margin; ventrodistal margin produced, with tiny spine distolaterally. Antennal acicle reaching beyond distal margin of fourth peduncular segment, slightly overreaching distal corneal margin; mesial margin with 1 spine proximally and 1 spiniform bristle at about midlength and additional few short setae.

Mandible ( Fig. 2 View FIGURE 2 a) without distinctive features. Maxillule ( Fig. 2 View FIGURE 2 b) with endopod slender, tapering distally, and with apical bristle. Maxilla ( Fig. 2 View FIGURE 2 c) with endopod slender and nearly reaching anterior end of basial endite. First maxilliped ( Fig. 2 View FIGURE 2 d) with endopod not reaching anterior margin of distal endite; exopod with lateral margin slightly expanded proximally. Second maxilliped ( Fig. 2 View FIGURE 2 e) with basis-ischium fusion incomplete; exopod elongate. Third maxilliped ( Fig. 2 View FIGURE 2 f) slender; basis and ischium separated by distinct suture; propodus subequal in length to carpus; carpus unarmed; merus with small spine on dorsodistal margin; ischium ( Fig. 2 View FIGURE 2 g) with somewhat reduced crista dentata composed of row of 5 triangular teeth of various size and 1 accessory tooth; basis with 1 acute tooth on mesial margin; exopod long, reaching nearly to distal margin of carpus.

Right cheliped ( Fig. 3 View FIGURE 3 a, c, d) slightly longer and stouter than left. Dactyl approximately 0.8 length of palm; dorsal surface with row of tufts of short setae along cutting edge and few setae on midline, dorsomesial margin not delimited; mesial and ventral surfaces with tufts of short to moderately long setae; cutting edge with large, triangular calcareous tooth and row of small, rounded teeth, terminating in small corneous claw. Palm distinctly shorter than carpus; dorsal surface gently convex, unarmed, dorsomesial and dorsolateral margins not delimited; mesial and lateral faces with few short setae; fixed finger with scattered short setae on dorsal surface; cutting edge with 2 large but low, calcareous teeth medially, terminating in very small corneous claw; ventral surfaces of palm and fixed finger with scattered tufts of sparse setae. Carpus subequal in length to merus; dorsomesial and dorsolateral margins each with row of small spines decreasing in size and sharpness proximally; dorsal surface shallowly grooved, unarmed; mesial, lateral and ventral surfaces unarmed; ventromesial and ventrolateral distal angles each with small spine. Merus with 1 prominent spine on dorsodistal margin; dorsal surface with very short transverse rows of short stiff setae; lateral and mesial surfaces smooth, ventrolateral and ventromesial margins each with small but distinct spine; ventral surface unarmed. Ischium with small spine on ventrolateral distal angle.

Left cheliped ( Fig. 3 View FIGURE 3 b, e, f) slender, with chela weakly compressed dorsoventrally; fingers slightly arched ventrally. Dactyl approximately 1.1 length of palm; dorsomesial margin not delimited; dorsal and ventral surfaces with scattered tufts of short setae; cutting edge with row of minute corneous teeth, terminating in small corneous claw. Palm approximately 0.5 length of carpus; dorsal surface weakly convex, dorsomesial and dorsolateral margins not delimited; mesial, lateral and ventral surfaces with scattered tufts of setae; cutting edge of fixed finger with row of minute corneous teeth, terminating in small corneous claw. Carpus subequal in length to merus; dorsomesial and dorsolateral margins each with row of small spines decreasing in size and sharpness proximally; mesial, lateral and ventral surfaces unarmed; ventromesial and ventrolateral angles each with small distal spine, otherwise unarmed. Merus with prominent spine on dorsodistal margin; dorsal surface narrowly flattened, with row of very short transverse ridges bearing short to long setae; mesial, lateral and ventral surfaces unarmed; ventromesial and ventrolateral margins each with small distal spine. Ischium with few setae on ventromesial margin, unarmed.

Second and third pereopods ( Fig. 4 View FIGURE 4 a, b) generally similar to each other, right pair overreaching right cheliped by approximately full length of dactyli. Dactyli ( Fig. 1 View FIGURE 1 c, d) broad, distinctly blade-shaped in lateral view, shorter than propodi; in dorsal view, straight, in lateral view, slightly curved ventrally; terminating in small corneous claws; dorsal margins each with row of spinules; lateral surface flattened; mesial surface concave, with scattered short setae medially; ventromesial margins each with row of about 20 corneous spinules. Propodi approximately twice length of carpi, somewhat compressed laterally; dorsal surfaces each bearing row of widely-spaced, slender corneous spinules; lateral and media faces smooth; ventral margins unarmed. Carpi approximately half length of meri; dorsal surfaces each with row of small spines and row of corneous spinules distributed over entire length; lateral, mesial and ventral surfaces smooth. Meri each with 3 small but conspicuous spines on dorsal surface in distal 0.3, remaining dorsal surface with row of sparse long setae, but not spinulose; lateral surface of second flattened and with few very short setae in second, but that of third noticeably convex and with 2 rows of short spiniform bristles dorsally and minute setae ventrally; ventral surfaces each with single row of small spines, and short spiniform bristles. Ischia unarmed.

Fourth pereopods ( Fig. 1 View FIGURE 1 c) slender, semichelate. Dactyl curved ventrally, terminating in small corneous claw, with 4 minute corneous spinules on ventral margin; preungual process ( Fig. 1 View FIGURE 1 d) well developed, reaching beyond terminal claw and crossed by latter. Propodus elongate, with reduced propodal rasp consisting of 6 slender spiniform scales arranged in single row and reduced in size proximally on ventrodistal margin.

Thoracic sternites ( Fig. 1 View FIGURE 1 b) broad. Fifth thoracic sternite subdivided into broad lateral lobes by deep longitudinal median groove. Anterior lobe of sixth thoracic sternite very short, broadly subrectangular, with sparse setae on ventral surface.

Pleon reduced, heart-shaped; no paired pleopods, but unpaired left biramous pleopods on second to fourth pleomeres. Uropods ( Fig. 1 View FIGURE 1 e) symmetrical; protopods not produced posteriorly. Telson ( Fig. 1 View FIGURE 1 e) subrectangular, with faint lateral indentations; posterior lobes almost symmetrical, without median cleft, but each with very shallow concavity on both sides.

Male unknown.

Etymology. Named after the country embracing the type locality.

Distribution. Currently only known from the South China Sea, at a depth of 110 m.

Remarks. The present new species is assigned to the genus Alainopaguroide s with little hesitation, although males were not available for study. The generic assignment is based on the following characters derived from the unique female holotype (cf. McLaughlin 2003, 2006): shield of carapace vaulted; gills biserial, 11 pairs; ocular acicles simple; fifth thoracic sternite subdivided into broad lateral lobes by deep longitudinal median groove; crista dentata of third maxilliped somewhat reduced; fourth pereopod with rudimentary propodal rasp, dactyl with prominent tubular preungual process at base of terminal claw; pleon reduced, heart shaped; no paired first pleopods modified as gonopods; uropods generally symmetrical; and telson with faint lateral indentations. Morphologically, A. sinensis sp. nov. is most similar to A. andamanensis among the three known congeneric species, particularly in having a marginally armed antennal acicle, a character being unusual for Paguridae (cf. Komai 1998; Komai & McLaughlin 2005; Komai & Osawa 2009). However, the possession of a sub-distal spine on the lateral margin of the first segment of the antennular peduncle distinguishes the new species from A. andamanensis . Other characters differentiating the present new species and A. andamanensis are discussed below.

The ocular acicles are shorter in A. sinensis sp. nov. than in A. andamanensis (only slightly overreaching the mesial base of the ocular peduncle versus elongate, reaching to approximately the midlength of the ocular peduncle, cf. Komai & McLaughlin 2005: fig. 1A). The carpi of the chelipeds are each armed with a small spine at the ventrolateral distal and ventromesial distal angle in A. sinensis sp. nov., but such spines are absent in A. andamanensis (cf. Komai & McLaughlin 2005: fig. 4B, D). The ischium of the left cheliped is unarmed in A. sinensis sp. nov., but there are two or three small spines on the ventromesial margin in A. andamanensis (cf. Komai & McLaughlin 2005: fig. 4C). The ischium of the second pereopod is unarmed in A. sinensis sp. nov., rather than having one small sub-distal spine on the ventral margin in A. andamanensis (cf. Komai & McLaughlin 2005: fig. 5A).

Komai & McLaughlin (2005) reported that A. andamanensis used a half of bivalve shells as protective covering. Morphological similarity of the new species to A. andamanensis may suggest that A. sinensis sp. nov. have a similar trait of housing, although the unique holotype did not carry any housing. Alainopaguroides shows Indo-West Pacific distribution, but none of the previously described species has been recorded from the South China Sea. The new species is the first representative of the genus known from the area.