Decaphyllus litoralis, 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 : 600-605

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-FFDF-FF89-72D4-FB50FD859D62
treatment provided by	Tatiana
scientific name	Decaphyllus litoralis
status	sp. nov.

Treatment

Decaphyllus litoralis , new species

( Figs. 8–12 View Fig View Fig View Fig View Fig View Fig )

Material examined. — Holotype: male (sl 1.8 mm), Manza , Okinawa, Ryukyu Islands, Japan, 18 m, 3 Jul.2011, SCUBA diving, coll. S. Komai, CBM-ZC 11707.

Paratype: ovigerous female (sl 1.7 mm), PANGLAO 2004, stn B5, Biking , Panglao Island, 09°35.2'N, 123°50.4'E, 4 m, reef slope with overhangs, 2 Jun.2004, NMCR 39088 GoogleMaps .

Non-type: 1 juvenile (sl 1.2 mm), Horseshoe, Onna Village , Okinawa, 19 m, 13 Sep.2012, SCUBA diving, coll. Y. Yamada, CBM-ZC 11708 .

Description. — Nine pairs of biserial phyllobranchiae (no pleurobranchs). Single arthrobranch above base of third maxilliped reduced to minute bud.

Shield ( Fig. 8A View Fig ) approximately as long as wide; anterior margin between rostral region and lateral projection slightly concave; anterolateral margins sloping; posterior margin truncate; dorsal surface with anteromedian part poorly calcified, with several short setae laterally. Rostrum obsolete. Lateral projections moderately developed, exceeding beyond rostral lobe, each with terminal spinule.

Ocular peduncle ( Fig. 8A View Fig ) about 0.8–0.9 times as long as shield, faintly constricted at midlength; dorsal surface with mesial row of tufts of moderately short to long setae directed mesially, scattered short setae on dorsal surface, and prominent tuft of long setae at base of cornea; cornea not dilated, its width slightly less than 0.3 of length of ocular peduncle; basal part slightly inflated, its width greater than corneal width. Ocular acicle tapering distally to acute spine, mesial margin glabrous; separated basally by width of 1 acicle. Interocular lobe visible in dorsal view, anteriorly slightly convex.

Antennular peduncle ( Fig. 8A 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 of ultimate segment.

Antennal peduncle ( Fig. 8A View Fig ) reaching or slightly falling short of base of cornea 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 small spine. First segment unarmed on ventrodistal margin; lateral surface unarmed. Antennal acicle slightly overreaching distal margin of fifth peduncular segment, reaching or slightly falling short of corneal base, terminating in small spine; mesial surface with sparse row of setae; lateral margin unarmed. Antennal flagellum with 2–4 short to moderately long setae on distal margin of each article.

Third maxilliped with merus armed with strong dorsodistal spine; crista dentata on ischium consisting of 2–4 triangular teeth; basis unarmed or with minute denticle on mesial face. Exopod long, reaching nearly to distal margin of carpus.

Chelipeds ( Figs. 9 View Fig , 10 View Fig ) slightly unequal in length; right slightly longer but appreciably stronger. Right cheliped ( Fig. 9 View Fig ) with chela elongate subovate in dorsal view, 2.3–2.5 times longer than wide. Dactylus ( Fig. 9C View Fig ) set at slightly oblique angle to palm, slightly shorter than palm; dorsal surface with 2–4 tiny spines or tubercles proximally; all surfaces with scattered moderately short to long setae, particularly numerous on mesial surface; cutting edge with row of small, blunt calcareous teeth in proximal 0.8 and microscopic corneous teeth in distal 0.2, terminating in tiny corneous claw. Palm ( Fig. 9A, C View Fig ) subequal in length to carpus; dorsomesial margin with row of 8 tiny spines, dorsal midline with 1 small proximal spine and row of minute tubercles or spinules not extending onto fixed finger, dorsolateral margin not delimited and with irregular row of minute tubercles or spinules, dorsal surface lateral to midline without conspicuous spines; lateral and mesial surfaces with scattered short to moderately short setae; ventral surface gently convex, smooth, with sparse setae. Fixed finger with row of blunt calcareous teeth on cutting edge, terminating in small calcareous claw. Carpus ( Fig. 9A–C View Fig ) moderately widened distally, subequal in length to merus, 1.9–2.2 times longer than wide; dorsomesial margin with row of 4 or 5 small to moderately strong spines, dorsolateral surface with row of 3 or 4 moderately small spines; all surfaces with scattered short to long setae, subdistal transverse row of setae particularly prominent; ventrolateral distal angle with spinule, distomesial angle unarmed. Merus ( Fig. 9A, B, D View Fig ) with 1 small spine on dorsodistal margin mesially; dorsal surface with sparse setae; ventrolateral margin with 1 or 2 small spines on distal half; mesial surface with small spine or protuberance proximoventrally, ventromesial margin with 2 small spines, distal spine directed proximally; ventral surface with small spine medially. Ischium ( Fig. 9D View Fig ) with 2 widely spaced spinules on ventromesial margin; lateral surface unarmed or with spinule subdistally.

Left cheliped ( Fig. 10 View Fig ) without hiatus between dactylus and fixed finger. Dactylus ( Fig. 10A, C View Fig ) about 1.3 times longer than palm, with few minute proximal tubercles or spinules on dorsal surface mesially, and with short to long setae particularly numerous on mesial surface; cutting edge with row of calcareous denticles, terminating in small corneous claw. Palm ( Fig. 10A, C View Fig ) about 0.6–0.7 length of carpus; dorsomesial margin with row of 4 or 5 spinules, dorsal midline with 1 small proximal spine and row of minute tubercles, dorsolateral margin not delimited and with some minute tubercles or spinules and also with scattered short to long setae. Fixed finger with cutting edge faintly denticulate, with row of minute corneous teeth in distal 0.4, terminating in small corneous claw. Carpus ( Fig. 10A–C View Fig ) moderately widened distally, about 3.0–3.4 times longer than wide; dorsolateral margin with 3 small spines in distal half, dorsomesial margin with 4 or 5 small to moderately strong spines (distal second spine largest); ventrolateral distal angle with spinule, distomesial angle unarmed; all surfaces with scattered setae. Merus ( Fig. 10A, B, D View Fig ) with sparse setae on dorsal surface; dorsodistal margin with 1 small spine; ventrolateral margin with 2 small spines; mesial surface with 1 small, anteriorly curved spine proximoventrally, ventromesial margin with 1 or 2 spines; ventral surface with 1 small spine medially and with scattered setae. Ischium ( Fig. 10D View Fig ) with 2 widely spaced, anteriorly directed spinules on ventromesial margin; lateral surface with subdistal spinule ventrally.

Ambulatory legs ( Fig. 11 View Fig ) overreaching tip of right cheliped. Dactyli ( Fig. 11A, B, D View Fig ) 1.6–1.9 times longer than propodi, 9.8–12.0 times longer than broad, gently curved ventrally; all surfaces unarmed, but with numerous setae, particularly longer and stronger on dorsal margins. Propodi ( Fig. 11A, D View Fig ) unarmed, but with row of sparse setae on dorsal and ventral margins and scattered short setae on lateral and mesial faces. Carpi each with dorsodistal spine (spine distinctly stronger in second than in third), and 1 additional small spine slightly proximal to midlength (second, Fig. 11C View Fig ) or no additional spine (third, Fig. 11D View Fig ). Meri ( Fig. 11A, C, D View Fig ) each with 2 small spines (located at slightly distal to midlength and proximal 0.2) on dorsal margin: dorsal and ventral margins with sparse long setae, latter unarmed. Ischium with 1 subdistal spinule on ventral margin mesially (second; Fig. 11C View Fig ) or unarmed (third).

Fourth pereopods ( Fig. 8B 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, 1 or 2 minute corneous scales present distally. Fifth pereopods semichelate.

Male with right sexual tube ( Fig. 8D View Fig ) long, directed from right to left across ventral body surface and curved anteriorly, reaching to level of coxa of left third pereopod; distal part somewhat flattened, slightly widened. Left sexual tube ( Fig. 8D View Fig ) directed from left to right, reaching to anteromesial part of coxa of right fifth pereopod, twisted, markedly broadened distally. Female with unpaired left gonopore.

Anterior lobe of thoracic sternite 6 (third pereopods, Fig. 8C View Fig ) subsemicircular, slightly skewed to left, bearing some moderately long setae anteriorly. Sternite of thoracic sternite 8 (fifth pereopods) in male ( Fig. 8D View Fig ) transversely subovate, almost glabrous; that in female subcircular, with row of moderately short setae anteriorly.

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

biramous. Female with 4 unpaired, unequally biramous pleopods.

Telson ( Fig. 8E View Fig ) with shallow median cleft; terminal margin with prominently produced, spinose left exterior angle separated from faintly produced, minutely spinose right exterior angle, and with 1 or 2 minute spinules on either side of median cleft; left lateral margin forming very narrow chitinous plate, but right lateral margin simple.

Colouration. — In life ( Fig. 12 View Fig ). Ocular peduncle generally light gray-brown. Antennular peduncle also generally light gray-brown, ultimate segment with narrow white ring distally. Antennal flagellum generally white with reddish brown distal part. Chelipeds generally light gray-brown, with brown transverse markings at least on palms and carpi. Ambulatory legs generally light gray-brown; propodi whitish distally and brownish proximally.

In preservative. No iridescent sheen on shield and appendages.

Distribution. — Ryukyu Islands, Japan, and the Bohol Sea, Philippines; 4– 18 m.

Remarks. — As discussed above, Decaphyllus litoralis , new species, is similar to D. brevis , new species, and D. deliquus , new species. Differentiating characters are discussed under “ Remarks ” of respective species.

Decaphyllus litoralis is the sole representative of the genus occurring in the shallow coral reefs at depths of 4–18 m. Other known species in the genus occur at sublittoral depths greater than 50 m.

Etymology. — From the Latin litoralis (= coastal), in reference to the habitat of this new species in the shallow coral reefs, which is unique for the genus.