Catapagurus exilidigitus, Komai & Rahayu, 2021

Komai, Tomoyuki & Rahayu, Dwi Listyo, 2021, Three new species of the pagurid hermit crab genus Catapagurus A. Milne-Edwards, 1880 (Decapoda: Anomura: Paguroidea) from the Bohol Sea, the Philippines, Raffles Bulletin of Zoology 69, pp. 156-174 : 157-162

publication ID	https://doi.org/ 10.26107/RBZ-2021-0013
publication LSID	lsid:zoobank.org:pub:C6DD0960-51EE-40C6-B948-BFAEF4E9F304
persistent identifier	https://treatment.plazi.org/id/C49C2D29-4768-4620-AD49-7358E6830A0D
taxon LSID	lsid:zoobank.org:act:C49C2D29-4768-4620-AD49-7358E6830A0D
treatment provided by	Diego
scientific name	Catapagurus exilidigitus
status	sp. nov.

Treatment

Catapagurus exilidigitus , new species

( Figs. 1–4 View Fig View Fig View Fig View Fig )

Material examined. Holotype: male (sl 1.7 mm), NMCR 50801, PANGLAO 2004, stn T39 , Bohol Sea, west of Pamilacan Island, Cervera shoal, 9°30.1′N, 123°50.4′E, 100–138 m, muddy sand, trawl, 6 July 2004. GoogleMaps

Paratypes: 2 males (sl 1.5, 1.8 mm), ZRC 2021.0413 View Materials , same data as holotype GoogleMaps .

Description. Shield ( Fig. 1A View Fig ) approximately as long as broad; anterior margin between rostral lobe and lateral projections concave; anterolateral margins sloping; posterior margin roundly truncate; dorsal surface with longitudinal rows of tufts of short setae posterior to lateral projections; carapace lateral lobes very narrow, well calcified. Rostral lobe rounded, produced as far as lateral projections. Lateral projections broadly triangular, each with terminal, submarginal spinule. Posterior carapace 0.6 length of shield; posterolateral plates moderately wide anteriorly, drawn out into relatively thin bands reaching to posterior margins, posterior median plate short, only weakly calcified.

Ocular peduncles ( Fig. 1A View Fig ) moderately short (0.8 times as long as shield), stout, widened distally; corneal width 0.6 of peduncular length. Ocular acicles narrow, spike-like, slender, reaching 0.4 length of ocular peduncles, terminating acutely; widely separated basally.

Antennular peduncle ( Fig. 1A, B View Fig ) overreaching distal corneal margin by full length of ultimate article. Ultimate article 0.9 times as long as shield, 5.3 times as long as distal height, with tuft of 7 long setae at dorsodistal lateral margin and with row of some short setae on dorsal surface. Penultimate article almost glabrous. Basal article with slightly produced, acute ventrodistal margin; statocyst lobe weakly inflated in proximal half of article.

Antennal peduncle ( Fig. 1A View Fig ) overreaching distal corneal margin by 0.2–0.3 length of article 5. Articles 5 and 4 with few setae. Article 3 with few setae on unarmed ventromesial distal angle. Article 2 with produced, spiniform dorsolateral distal angle reaching midlength of article 4; dorsomesial distal angle with small spine. Article 1 with small spine at dorsolateral distal angle. Antennal acicle reaching midlength of article 5 and overreaching corneal base, terminating in spine. Flagella broken off and not preserved.

Maxilliped 3 endopod moderately stout; merus with small dorsodistal spine; ischium with crista dentata consisting of 6 small teeth; accessory tooth small, subdistal in position ( Fig. 1C View Fig ).

Right cheliped ( Fig. 2A–D View Fig ) long, moderately stout. Chela ( Fig. 2A View Fig ) elongate subovate, 2.6 times as long as wide. Dactylus 0.7 length of palm; weakly convex dorsal surface almost smooth and with tufts of setae dorsomesially; dorsomesial margin not delimited, rounded; mesial face with scattered granules; ventral surface with some tufts of long setae; occlusal margin with 2 obtuse calcareous teeth, slightly overlapped by fixed finger. Palm subequal in length to carpus, 1.6 times as long as wide; dorsomesial and dorsolateral margins not delimited, convex dorsal surface almost smooth except for granulate dorsolateral part; lateral and mesial faces granulate; ventral surface gently convex, with scattered tufts of moderately long setae; fixed finger with 2 rows of short setae on dorsal surface, occlusal margin with low, broad calcareous tooth proximal to midlength, unarmed in distal half. Carpus ( Fig. 2D View Fig ) subequal in length to merus, widened distally, 2.2 times as long as distal width; dorsomesial and dorsolateral margins each delimited with row of tiny spines, strongest distally, and with few bristlelike setae proximally, dorsal surface almost smooth with few granules; lateral surface with scattered granules; mesial face almost smooth except for some granules adjacent to dorsal margin, ventromesial distal angle with tiny spine; ventral surface gently convex, smooth. Merus subtriangular in cross section; dorsodistal margin without spine, but with few bristle-like setae; dorsal surface with widely spaced stiff setae; lateral surface with sparse granules, gently convex ventrolateral margin without conspicuous spines; mesial surface almost glabrous except for few short stiff setae, weakly convex ventromesial margin with small distal spine; ventral surface with sparse granules. Ischium unarmed. Coxa unarmed on ventromesial angle.

Left cheliped ( Fig. 3A–D View Fig ) slender, shorter than right cheliped; dactyl and fixed finger slightly curved ventrally. Chela ( Fig. 3A View Fig ) 5.0 times as long as wide. Dactylus 1.5 times as long as palm, terminating in small, curved corneous claw; surfaces almost smooth, with sparse setae; dorsomesial margin not delimited; occlusal margin with row of minute corneous teeth almost over entire length. Palm 0.5 length of carpus, 2.0 times as long as wide; dorsomesial and dorsolateral margins not delimited, transversely convex dorsal surface with sparse granules; ventral surface slightly convex, smooth; fixed finger smooth on surfaces, terminating in small, curved corneous claw, with sparse short setae; occlusal margin with row of minute corneous teeth. Carpus ( Fig. 3D View Fig ) slightly longer than merus; dorsomesial and dorsolateral margins each with row of tiny spines, strongest distally, dorsal surface almost smooth; lateral surface with sparse granules; mesial surface nearly smooth except for granulate ventral part, granules extending onto slightly convex ventral surface. Merus dorsodistal margin unarmed; dorsal surface with several setae; lateral surface with sparse granules, particularly on ventral part, gently convex ventral margin unarmed; mesial surface almost smooth, with row of stiff setae adjacent to ventromesial margin, gently convex ventromesial margin with 3 tiny spines on distal margin; ventral surface granulates. Ischium unarmed. Coxa unarmed on ventromesial angle.

Pereopods 2 ( Fig. 4A, B View Fig ) slender, overreaching tips of outstretched chelipeds. Dactyli ( Fig. 4B View Fig ) very slender (about 23 times as long as wide), 1.4 times as long as propodi; in dorsal view, straight; in lateral view, slightly curved ventrally; dorsal margins each with row of moderately spaced bristlelike or spiniform setae, becoming longer distally; mesial faces each with row of 9 moderately spaced, spiniform or bristle-like setae extending near ventral margin to midline toward distal; lateral surfaces and ventral margins unarmed. Propodi slightly more than twice length of carpi; dorsal and ventral margins granulate, former with few stiff setae subdistally; lateral and mesial surfaces smooth; ventrodistal margin with 1 spiniform seta. Carpi short, about half-length of meri; dorsal surfaces each with row of spinules, strongest distally; lateral surface with few granules, mesial and ventral surfaces almost smooth. Meri each with 1 small dorsodistal spine; dorsal surface with few low transverse ridges and moderately spaced bristle-like setae, but without spines; lateral and mesial surfaces smooth except for granulate ventral parts; ventral surfaces granulate, ventrolateral distal angle with minute spine. Ischia unarmed.

Pereopods 3 ( Fig. 4C, D View Fig ) generally similar to pereopods 2. Dactyli ( Fig. 4D View Fig ) 26 times as long as wide, 1.5 times as long as propodi; dorsal margins each with row of moderately spaced bristle-like or spiniform setae, becoming longer distally; mesial faces each with row of about 10 moderately spaced spiniform setae extending near ventral margin to midline toward distal; lateral surfaces and ventral margins unarmed. Propodi about twice length of carpi; dorsal margins faintly granulate, ventral margins nearly smooth; lateral and mesial surfaces also smooth; ventrodistal margin with 1 spiniform seta. Carpi short, about half-length of meri; dorsal surfaces each with row of spinules, strongest distally; lateral, mesial and ventral surfaces almost smooth. Meri unarmed on dorsodistal margin, but with bristle-like seta; dorsal surface with 2 low transverse ridges and bristle-like setae subdistally, remainder with irregular rows of bristlelike or stiff setae; lateral and mesial surfaces smooth; ventral surfaces granulate, ventrolateral distal angle unarmed. Ischia longer than those of pereopods 2, unarmed.

Pereopods 4 ( Fig. 1D View Fig ) weakly semichelate; dactyli each with well developed preungual process far extending beyond tip of corneous claw; propodal rasp consisting of single row of corneous scales on distal 0.8 of ventral margin. Pereopods 5 chelate.

Males with long right sexual tube (right pereopod 5 coxa) curved dorsally over pleon and reaching pleonal midline, terminus simple, with few minute setae ( Fig. 1F View Fig ). Left pereopod 5 coxa with small, papilla-like protrusion from gonopore, circumscribed by short setae ( Fig. 1F View Fig ).

Thoracic sternite 6 (pereopods 3) ( Fig. 1G View Fig ) with moderately wide, subsemicircular anterior lobe, much shorter than large posterior lobe; posterior lobe distinctly longer than anterior lobe. Sternite 8 (pereopods 5) ( Fig. 1E View Fig ) consisting of two small rounded lobes moderately separated.

Pleon in males with small, uniramous unpaired left pleopods 3 and 4, no pleopod 5; females unknown. Uropodal protopods not protruding posteriorly.

Telson ( Fig. 1H View Fig ) with lateral indentations suggesting separation of anterior and posterior portions; triangular posterior lobes separated by moderately deep U-shaped median cleft, each terminating in subacute tip; oblique terminal margins unarmed, with few minute setae on right margin.

Colouration in life. Not known.

Distribution. Presently known only from the Bohol Sea, central Philippines, at depths of 100– 138 m.

Takeda, 2006; McLaughlin & Rahayu, 2008). Catapagurus exilidigitus , new species, is primarily distinguished from C. tanimbarensis by the telson with a wide, U-shaped median cleft ( Fig. 1H View Fig ) (versus telson with a narrow, slit-like V-shaped median cleft; McLaughlin, 1997: fig. 18i, k, m). Other differentiating characters are: (1) the ultimate article of the antennular peduncle is relatively longer in C. exilidigitus , new species, than in C. tanimbarensis (0.9 times as long as the shield versus about 0.7 times) ( Fig. 1A, B View Fig versus McLaughlin, 1997: fig. 18a, b); the meri of chelipeds are unarmed on the dorsodistal margins in C. exilidigitus , new species ( Figs. 2 View Fig , 3 View Fig ), whereas armed with one or more dorsodistal spine(s) in C. tanimbarensis (cf. McLaughlin, 1997: 499; fig. 18c); the ambulatory dactyli are more elongate and slender in C. exilidigitus , new species, than in C. tanimbarensis (1.4–1.5 times as long as the propodus; more than 20 times as long as wide in C. exilidigitus , new species, cf. Fig. 4 View Fig ; versus 1.0–1.25 times as long as the propodus and less than 15 times as long as wide in C. tanimbarensis , cf. McLaughlin, 1997: fig. 18d–f; Asakura, 2001: fig. 37F); the pereopod 2 meri are only armed with a dorsodistal spine in C. exilidigitus , new species (cf. Fig. 4A View Fig ), rather than armed with subdistal spines on the dorsal surface in addition to the dorsodistal spine in C. tanimbarensis (cf. McLaughlin, 1997: fig. 18d).