Decaphyllus proprius, Komai & Rahayu, 2013

Komai, Tomoyuki & Rahayu, Dwi Listyo, 2013, Six New Species Of The Hermit Crab Genus Decaphyllus De Saint Laurent, 1968 (Crustacea: Decapoda: Anomura: Paguridae) From The Boholo Sea, The Philippines, And The Ryukyu Islands, Japan, Raffles Bulletin of Zoology 61 (2), pp. 589-620 : 605-610

publication ID	https://doi.org/ 10.5281/zenodo.5352524
publication LSID	lsid:zoobank.org:pub:3EC76281-1ABA-4E72-BBE1-0BF811387484
persistent identifier	https://treatment.plazi.org/id/850B9A25-FFC4-FF8C-7326-FED1FE919F42
treatment provided by	Tatiana
scientific name	Decaphyllus proprius
status	sp. nov.

Treatment

Decaphyllus proprius , new species

( Figs. 13–16 View Fig View Fig View Fig View Fig , 23A View Fig )

Material examined. — Holotype: male (sl 1.4 mm), PANGLAO 2004, stn T39 , Cervera shoal, West Pamilacan Island, 09°30.1'N, 123°50.4'E, 100–138 m, muddy sand, 6 Jul.2004, NMCR 39089. GoogleMaps

Description. — Ten pairs of biserial phyllobranchiae (no pleurobranchs). Two very small arthrobranchs above base of third maxilliped, each bearing few lamellae ( Fig. 13C View Fig ).

Shield ( Fig. 13A View Fig ) approximately as long as wide; anterior margin between rostral region and lateral projection slightly concave; anterolateral margins sloping; posterior margin roundly truncate; dorsal surface with median part poorly calcified, with several minute setae anteriorly and laterally. Rostrum broadly rounded. Lateral projections weakly developed, exceeding as far as rostral lobe, each with terminal spinule.

Ocular peduncle ( Fig. 13A View Fig ) approximately as long as shield, faintly constricted at midlength; dorsal surface with mesial row of tufts of moderately short to long setae directed mesially and few individual setae laterally, and prominent tuft of long setae at base of cornea; cornea not dilated, its width slightly more than 0.2 of length of ocular peduncle; basal part slightly inflated, its width greater than corneal width. Ocular acicle drawn out into long acute spine, mesial margin with some moderately short setae; separated basally by width of less than 1 acicle. Interocular lobe visible in dorsal view, anteriorly slightly convex.

Antennular peduncle ( Fig. 13A View Fig ) overreaching distal corneal margin by about 0.4 length of ultimate segment. Basal segment with prominent spine on lateral margin of statocyst lobe, without ventromesial subdistal spine. Penultimate and ultimate segments unarmed, almost glabrous except for 1 short, thin seta on dorsomesial distal angle.

Antennal peduncle ( Fig. 13A View Fig ) reaching to distal 0.4 of ocular peduncle. Fifth and fourth segments with few setae. Third segment with prominent spine on ventromesial distal margin. Second segment with dorsolateral distal angle strongly produced, terminating in bifid spine (lateral spine distinctly subterminal), dorsomesial distal angle with strong spine. First segment with strong spine on ventrodistal margin; lateral surface unarmed. Antennal acicle slightly overreaching distal margin of fifth peduncular segment, far falling short of corneal base, terminating in small simple (left) or slightly falling short of distal margin of fifth peduncular segment, terminating in bifid spine (right) (possibly abnormal condition); mesial surface with sparse row of setae; lateral margin with small spine located at proximal 0.3. Antennal flagellum with 2–4 short to moderately setae on distal margin of each article.

Third maxilliped ( Fig. 13B View Fig ) with merus armed with strong dorsodistal spine; crista dentata on ischium consisting of 3 triangular teeth; basis with minute denticle on mesial face. Exopod long, reaching nearly to distal margin of carpus.

Chelipeds ( Figs. 14 View Fig , 15 View Fig ) slightly unequal in length; right slightly longer but appreciably stronger. Right cheliped ( Fig. 14 View Fig ) with chela elongate subovate in dorsal view, 2.9 times longer than wide. Dactylus ( Fig. 14C View Fig ) set at slightly oblique angle to palm, subequal in length to palm; dorsal surface with 1 tiny spine proximally; all surfaces with scattered moderately short to moderately long setae, particularly numerous on mesial surface; cutting edge with row of small, blunt calcareous teeth, terminating in tiny corneous claw. Palm ( Fig. 14A, C View Fig ) slightly shorter than carpus; dorsomesial margin with row of spinules or minute tubercles, dorsal midline with row of prominent spines decreasing in size distally and not extending onto fixed finger, dorsolateral margin not delimited and with irregular row of slender small spines, dorsal surface lateral to midline unarmed; lateral and mesial surfaces with scattered short to long setae; ventral surface convex, smooth, with sparse setae. Fixed finger with row of small, blunt or subtriangular calcareous teeth on cutting edge, terminating in small calcareous claw. Carpus ( Fig. 14A–C View Fig ) subequal in length to merus, slightly widened distally, 2.4 times longer than wide; dorsomesial margin with row of 7 spines (distalmost 2 minute, others moderately strong), dorsolateral surface with row of 7 small and minute spines; all surfaces with scattered short to long setae, subdistal transverse row of setae particularly prominent; both ventrolateral distal and ventromesial distal angles unarmed. Merus ( Fig. 14A, B, D View Fig ) with 1 small spine on dorsodistal margin mesially; dorsal surface with short transverse rows of setae; lateral surface with 1 low, small tubercle at about midlength adjacent to ventral margin, ventrolateral margin with 1 small subdistal spine; mesial surface with small, low protuberance adjacent to ventral margin proximally, ventromesial margin with 2 small, widely spaced spines; ventral surface unarmed. Ischium ( Fig. 14D View Fig ) with 2 widely spaced small spines on ventromesial margin, distal spine directed distally, proximal spine curved proximally and hook-like; lateral surface with 2 closely spaced spinules ventrodistally.

Left cheliped ( Fig. 15 View Fig ) with distinct hiatus between dactylus and fixed finger. Dactylus ( Fig. 15A, C View Fig ) about 1.2 times longer than palm, dorsal midline with 3 spinules in proximal 0.4; all surfaces with numerous short to long setae particularly on mesial surface; cutting edge with row of minute corneous teeth in distal half, terminating in small corneous claw. Palm ( Fig. 15A, C View Fig ) about 0.6 length of carpus; dorsomesial margin not delimited, dorsal midline with row of 5 small spines not extending onto fixed finger, dorsolateral margin not delimited, unarmed; all surfaces with scattered short to long setae. Fixed finger with row of calcareous denticles increasing in size distally on cutting edge, terminating in small corneous claw. Carpus ( Fig. 15A–C View Fig ) slightly widened distally, about 3.2 times longer than wide; dorsolateral margin with 4 moderately large spines, dorsomesial margin with 5 moderately strong spines; ventrolateral distal and distomesial angles unarmed; all surfaces with scattered setae. Merus ( Fig. 15A, B, D View Fig ) with sparse setae on dorsal surface; dorsodistal margin unarmed; lateral surface with 1 minute denticle adjacent to ventral margin, ventrolateral margin with 2 small subdistal spines and 1 median spinule; mesial surface with 1 small protuberance proximoventrally, ventromesial margin with 2 widely spaced spines in distal half. Ischium ( Fig. 15D View Fig ) with 2 widely spaced small spines on ventromesial margin, distal spine directed distally, proximal spine curved proximally; lateral surface with spinule ventrally.

Ambulatory legs ( Fig. 16 View Fig ) overreaching tip of right cheliped. Dactyli ( Fig. 16A, B, D View Fig ) 1.4–1.5 times longer than propodi, 13.3–14.6 times longer than broad, gently curved ventrally; all surfaces unarmed, but with numerous setae, particularly longer and stronger on dorsal margins. Propodi ( Fig. 16A, D View Fig ) unarmed, but with row of sparse setae on dorsal and ventral margins and with scattered short setae on lateral and mesial faces. Carpi each with dorsodistal spine and 2 additional small dorsal spines in proximal 0.4 (second, Fig. 16C View Fig ) or entirely unarmed (third, Fig. 16E View Fig ). Meri each with 2 small spines (located at slightly distal to midlength and proximal 0.2) on dorsal margin; dorsal and ventral margins with sparse short to long setae, latter armed with spinule at distal 0.3 (second, Fig. 16C View Fig ) or unarmed (third, Fig. 16E View Fig ). Ischium with distal spinule on ventral margin mesially (second, Fig. 16C View Fig ) or unarmed (third, Fig. 16E View Fig ).

Fourth pereopods ( Fig.13D View Fig ) non-chelate, with claw of dactylus entirely masked by tufts of short, dense setae; propodus with sparse setae on dorsal margin and distal half of ventral margin; 2 minute corneous scales present distally. Fifth pereopods semichelate.

Male with right sexual tube ( Fig. 13F View Fig ) long, directed from right to left across ventral body surface and curved anteriorly, reaching to level of coxa of left second pereopod; distal part somewhat flattened. Left sexual tube ( Fig. 13F View Fig ) directed from left to right, reaching to anteromesial part of coxa of right fifth pereopod, twisted, slightly broadened distally.

Anterior lobe of thoracic sternite 6 (third pereopods, Fig. 13E View Fig ) subsemicircular, slightly skewed to left, bearing several moderately long setae anteriorly. Sternite of thoracic sternite 8 (fifth pereopods) in male ( Fig. 13F View Fig ) transversely subovate, almost glabrous; anterior surface slightly concave.

Pleon dextrally twisted, with 4 unpaired left pleopods, second, fourth and fifth uniramous, third unequally biramous.

Telson ( Fig. 13G View Fig ) with shallow median cleft; terminal margin with prominently produced, spinose left exterior angle separated from less produced, but also prominent, spinose right exterior angle, and with 1 minute spinules on either side of median cleft; left lateral margin not chitinous.

Female unknown.

Colouration. — In life ( Fig. 23A View Fig ). Carapace generally pinkish, shield slightly mottled; posterior carapace with scattered darker pink spots. Ocular peduncles mottled with pink. Antennular and antennal peduncles pale pink, without conspicuous markings; antennal flagellum generally translucent. Chelipeds generally whitish, carpi and meri with large darker reddish blotches. Ambulatory legs obscurely banded by dull red and white; dactyli whitish; propodi with distal part white and proximal part white, remainder alternated with red (distal to midlength) and white (proximal to midlength); carpi reddish; meri each with obscure 2 reddish bands. Pleon pinkish.

In preservative. Slight iridescence seen on shield, chelipeds and ambulatory legs.

Distribution. — Known only from Panglao Islands, 100– 138 m.

Remarks. — In proportions of the cephalic appendages and armature of the chelipeds, Decaphyllus proprius , new species, most closely resembles D. maci . However, the present new species is quite distinctive in the genus in having a small but prominent spine on the lateral margin of the antennal acicle, which is located proximal to the midlength. In other congeneric species, such a spine is absent. The lack of a dorsodistal spine on the merus of the left cheliped appears also unique for the genus. Furthermore, D. proprius differs from D. maci in the following characters: shield proportionally wider in D. proprius than in D. maci (approximately as long as wide versus about 1.2 times as long as wide); lateral projections of shield less produced in D. proprius than in D. maci ; fingers of left chela, when closed, leaving a distinct hiatus in D. proprius , whereas no hiatus in D. maci ; dactylus of left cheliped with short proximal row of small spines on dorsal midline in D. proprius , while unarmed in D. maci ; dorsomesial margin of palm of left cheliped unarmed in D. proprius , whereas armed with 2 conspicuous spines in D. maci ; and anterior lobe of thoracic sternite 6 subsemicircular in D. proprius , rather than roundly subtriangular in D. maci .