Catapagurus fimbriatus, 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 : 162-167

Catapagurus fimbriatus , new species

( Figs. 5–8 )

Material examined. Holotype: male (sl 1.5 mm), NMCR 50802, PANGLAO 2004, stn T27 , Bohol Sea , between Panglao and Pamilacan islands, 09°33.4′N, 123°51.0′E, 106–137 m, fine sand and mud with echinoderms, trawl, 25 June 2004.

Paratype: 1 male (sl 1.4 mm), ZRC 2021.0414 , PANGLAO 2004, same data as holotype .

Remarks. There were no female specimens available for Description. Shield ( Fig. 5A ) 1.2 times broader than long; study. The present new species is assigned to Catapagurus anterior margin between rostral lobe and lateral projections without hesitation because it agrees with the generic features concave; anterolateral margins sloping; posterior margin of Catapagurus , including the gill formula consisting of 11 truncate; dorsal surface with longitudinal rows of tufts of pairs of biserial gills, the somewhat reduced crista dentata short setae on midline and posterior to lateral projections; on the maxilliped 3 ischium, the presence of a prominent carapace lateral lobes narrow, well calcified. Rostral lobe preungual process on the pereopod 4 dactyli, and the broadly and roundly triangular, usually produced as far as possession of a long sexual tube arising from the right lateral projections. Lateral projections broadly and roundly pereopod 5 coxa in males, curving exteriorly and over the triangular, each usually with terminal, submarginal spinule. lateral side of the body ( McLaughlin, 2003, 2004). Posterior carapace 0.5 length of shield; posterolateral plates moderately wide anteriorly, drawn out into relatively thin Catapagurus exilidigitus , new species, appears close to C. bands reaching to posterior margins, posterior median plate tanimbarensis McLaughlin, 1997 , presently known only short, only weakly calcified.

from the Banda Sea, Indonesia, in the general armature and slenderness of the pereopod 2 and 3 dactyli. In particular, in Ocular peduncles ( Fig. 5A ) short (0.7 times as long as these two taxa, the dorsal spiniform or bristle-like setae on the shield), stout, widened distally; corneal width 0.7 peduncular mesial surfaces of the ambulatory dactyli are relatively few length. Ocular acicles narrowly triangular, slender, reaching compared to other species in the C. misakiensis group (20 or 0.3 length of ocular peduncle, terminating acutely; widely less versus more than 30) (de Saint Laurent & McLaughlin, separated.

2000; Asakura, 2001; McLaughlin, 2002; Komai &

Antennular peduncle ( Fig. 5A, B ) overreaching distal corneal margin by full length of ultimate article. Ultimate article 0.8 times as long as shield, 5.3 times as long as distal height, with tuft of long setae at dorsodistal margin and some short setae on dorsal surface. Penultimate article with few short setae. Basal article with very slightly produced, subacute ventrodistal margin; statocyst lobe gently inflated in proximal half of lateral margin.

Antennal peduncle ( Fig. 5A ) overreaching distal corneal margin by 0.7 length of ultimate article. Articles 5 and 4 with few, scattered short setae. Article 3 with few setae on unarmed ventrodistal angle. Article 2 with produced dorsolateral distal angle reaching to or beyond base of article 4, terminating in spine; dorsomesial distal angle with prominent spine. Article 1 with small spine at dorsolateral distal angle. Antennal acicle reaching distal margin of article 4 and reaching corneal base, terminating in spine. Flagella missing.

Maxilliped 3 endopod ( Fig. 5C ) moderately stout; merus with small dorsodistal spine; ischium with crista dentata consisting of 5 small teeth; accessory tooth prominent ( Fig. 5D ).

Right cheliped ( Fig. 6A–D ) long, moderately slender. Chela elongate subovate ( Fig. 6A ), 2.7 times as long as wide. Dactylus 0.9 length of palm; weakly convex dorsal surface almost smooth and with sparse tufts of setae; dorsomesial margin not delimited, rounded; occlusal margin with 2 blunt 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, dorsal and mesial surfaces minutely granular; ventral surface nearly smooth; fixed finger with sparse tufts of setae in distal half, occlusal margin with row of low, blunt calcareous teeth over entire length. Carpus ( Fig. 6D ) slightly shorter than merus, 2.7 times as long as distal width; dorsal surface with sparse granules, dorsomesial margin delimited with row of tiny spines in distal 0.3 and of minute granules proximally, and with few setae, dorsodistal margin unarmed; dorsolateral margin delimited with irregular row of spinules, and with few setae; lateral and mesial surfaces with sparse minute granules, ventral surface nearly smooth; all with covering of tiny or minute spinules, tubercles or granules. Merus subtriangular in cross section; dorsodistal margin with small spine; dorsal surface with widely spaced short setae; mesial and lateral faces almost smooth; ventrolateral and ventromesial margins each with small distal spine; ventral surface smooth, only with few short setae. Ischium unarmed on distolateral margin. Coxa with small ventromesial distal spine ( Fig. 1E ).

Left cheliped ( Fig. 7A–D ) slender, subequal in length to right cheliped; dactyl and fixed finger nearly straight. Chela ( Fig. 7A ) 4.8 times as long as wide. Dactylus 1.8 times as long as palm; surfaces almost smooth, with sparse tufts of setae; dorsomesial margin not delimited; occlusal margin with row of tiny corneous teeth in distal half, otherwise unarmed. Palm 0.5 length of carpus, 1.8 times as long as wide; dorsomesial and dorsolateral margins not delimited, dorsal, lateral and mesial surfaces with few setae and sparse minute granules; ventral surface slightly convex, smooth; fixed finger with smooth surfaces, few scattered long setae; occlusal margin with row of minute calcareous teeth in distal half, unarmed in proximal half. Carpus ( Fig. 7D ) slightly shorter than merus, 4.0 times as long as distal width; dorsomesial margin with row of spinules and few setae, dorsolateral margin with row of granules, becoming spinulose distally, dorsal surface with few granules distally, otherwise smooth; mesial and lateral surfaces with sparse granules, ventral surface smooth. Merus with small spine on dorsodistal margin, dorsal surface with row of widely spaced setae; lateral surface with sparse granules, mesial and ventral surfaces almost smooth, ventromesial and ventrolateral distal angles each with small spine. Ischium with small spine distolaterally. Coxa with small ventromesial distal spine ( Fig. 1E ).

Pereopods 2 ( Fig. 8A–C ) considerably overreaching tips of outstretched chelipeds. Dactyli narrowly blade-shaped, 1.1 times as long as propodi; in dorsal view, straight; in lateral view, gently curved ventrally; dorsal margins each with row of moderately spaced setae, becoming longer and more stiff distally; mesial faces ( Fig. 8C ) slightly concave, each with row of about 20 moderately spaced, stiff setae adjacent to ventral margin; lateral faces and ventral margins unarmed. Propodi approximately twice length of carpi; dorsal margins and lateral surface smooth, almost glabrous; mesial surfaces each with longitudinal rows of setae adjacent to dorsal and ventral margins. Carpi 0.6 length of meri; dorsal surfaces each with row of very small spinules, strongest distally; lateral, mesial and ventral surfaces almost smooth. Meri each with 1 small dorsodistal spine; dorsal surface with 2 small subdistal spines and widely spaced stiff setae; lateral and mesial faces glabrous; ventral surfaces with few short setae, ventrolateral distal angle with small spine. Ischia unarmed.

Pereopods 3 ( Fig. 8D–G ) distinctly longer than pereopods 2. Dactyli ( Fig. 8F ) narrowly blade-shaped, 1.3 times as long as propodi; in dorsal view, straight; in lateral view, gently curved ventrally; dorsal margins each with row of numerous, closely spaced setae, becoming longer and more stiff distally; mesial faces each with row of numerous setae adjacent to ventral margin; lateral surfaces and ventral margins unarmed. Propodi ( Fig. 8E ) approximately twice length of carpi; dorsal margins unarmed; mesial surfaces each with sparse granules and row of short setae adjacent to dorsal margins; lateral surfaces smooth; ventral margins each with row of short setae in distal 0.7. Carpi ( Fig. 8E ) 0.6 length of meri; dorsal surfaces each with row of very small spinules, strongest distally; lateral surface with sparse granules medially, mesial and ventral surfaces almost smooth. Meri each with 1 small dorsodistal spine; dorsal surface with 2 small subdistal spines and irregular rows of short stiff setae mesially; lateral surface with sparse granules; mesial surface smooth; ventral surfaces slightly granulate, bearing 3 spinules in paratype, no distinct spinule in holotype, ventrolateral distal angle unarmed. Ischia unarmed.

Pereopods 4 ( Fig. 5F ) weakly semichelate; dactyli each with well developed preungual process usually far extending beyond tip of claw; propodal rasp consisting of single row of corneous scales on distal half of ventral margin, distalmost scale longest. Pereopods 5 chelate.

Males with long right sexual tube curved dorsally over pleon and reaching pleonal midline, terminating in 2 small, unequal lobes ( Fig. 5G, H ). Left coxa lacking gonopore, having row of setae on ventral surface posteriorly ( Fig. 5G ).

Thoracic sternite 6 (pereopods 3) ( Fig. 5I ) with very wide, subtrapezoidal anterior lobe, much shorter than large posterior lobe; with row of short setae on anterior margin; posterior lobe much longer than anterior lobe. Sternite 8 consisting of two small rounded lobes widely separated.

Pleon in males with 3 unpaired, uniramous pleopods (pleopods 3–5); females unknown. Uropodal protopods not protruding posteriorly.

Telson ( Fig. 5J ) with lateral indentations suggesting separation of anterior and posterior portions; triangular posterior lobes separated by very wide, trapezoidal medial cleft, each terminating in subacute tip; oblique terminal margins unarmed.

Colouration in life. Not known.

Distribution. Presently known only from the Bohol Sea, central Philippines; at depths of 77– 137 m.

Remarks. There were no female specimens available for study. None of the two types is intact: in the holotype, the entire pleon is missing; in the paratype, both chelipeds and pereopods 2 are missing. Nevertheless, the new species is assigned to Catapagurus without hesitation because it agrees with the generic features, including the gill formula consisting of 11 pairs of biserial gills, the somewhat reduced crista dentata on the maxilliped 3 ischium, the presence of a prominent preungual process on the pereopods 4 dactyli and the possession of a long sexual tube arising from the right pereopod 5 coxa, curving exteriorly and over the lateral side of the body ( McLaughlin, 2003, 2004).

Catapagurus fimbriatus , new species, is readily distinguished from all other congeneric species in the characteristic setation of the pereopod 3 dactyli and propodi: the dactylus has a row of dense setae on the dorsal margin and on the mesial face adjacent to the ventral margin; the merus is also provided with setal rows on the mesial face adjacent to the dorsal margin and on the distal 0.7 of the ventral margin. Such setation is not seen in the 24 other species in the genus ( McLaughlin, 1997, 2002, 2004; Hogarth et al., 1998; de Saint Laurent & McLaughlin, 2000; Asakura, 2001; Komai & Osawa, 2009; Nucci & Melo, 2012; this study). The shape of the ambulatory dactyli of the present new species is also notable: the dactyli are slender as in species referred to the C. misakiensis species group as diagnosed by Asakura (2001; as C. japonicus group), but in this new species the shape is similar to the blade-shaped dactyli with shallow concave mesial faces of the C. ensifer species of Asakura (2001). As a result, this new species appears to be intermediate between the two species groups as proposed by Asakura (2001), and cannot be satisfactorily placed in either.

Etymology. The Latin fimbriatus (= fringed) refers to the characteristic setation of the ambulatory dactyli of the new species.

Figures

Fig. 5. Catapagurus fimbriatus, new species. A–I, holotype, male (sl 1.5 mm), NMCR 50802; J, paratype, male (1.4 mm), ZRC 2021.0414. A, shield, carapace lateral lobes and cephalic appendages, dorsal view; B, left antennule, ultimate article of peduncle and flagella, lateral view; C, left maxilliped 3, endopod, lateral view; D, ischium, ventral view; E, coxae of chelipeds, ventral view; F, left pereopod 4, lateral view; G, coxae of pereopods 5 and thoracic sternite 8, ventral view; H, distal part of right sexual tube, dorsal view; I, thoracic sternite 6, ventral view; J, telson, dorsal view.

Fig. 6. Catapagurus fimbriatus, new species, holotype, male (sl 1.5 mm), NMCR 50802. A, chela of right cheliped, dorsal view; B, right cheliped, mesial view; C, same, lateral view; D, carpus of right cheliped, dorsal view.

Fig. 7. Catapagurus fimbriatus, new species, holotype, male (sl 1.5 mm), NMCR 50802. A, chela of left cheliped, dorsal view; B, left cheliped, mesial view; C, same, lateral view; D, carpus of left cheliped, dorsal view.

Fig. 8. Catapagurus fimbriatus, new species. A–F, holotype, male (sl 1.5 mm), NMCR 50802; G, paratype, male (sl 1.4 mm), ZRC 2021.0414. A, right pereopod 2, lateral view; B, same, propodus and carpus, mesial view; C, same, dactylus, mesial view; D, left pereopod 3, lateral view; E, same, propodus and carpus, mesial view; F, same, dactylus, mesial view. G, left pereopod 3, merus, lateral view.

Fig. 1. Catapagurus exilidigitus, new species, holotype, male (sl 1.7 mm), NMCR 50801. A, shield, carapace lateral lobes and cephalic appendages, dorsal view; B, left antennule, ultimate article of peduncle and flagella, lateral view; C, left maxilliped 3, ischium and basis, ventral view; D, right pereopod 4, lateral view; E, coxae of pereopods 5 and thoracic sternite 8, ventral view; F, distal part of right sexual tube, dorsal view; G, thoracic sternite 6, ventral view; H, telson, dorsal view.