Pagurus spinulentus ( Henderson, 1888 )

Komai, Tomoyuki & Rahayu, Dwi Listyo, 2014, New records and new species of the hermit crab genus Pagurus Fabricius, 1775 (Crustacea: Decapoda: Anomura: Paguridae) from the Philippines, Raffles Bulletin of Zoology 62, pp. 620-646 : 629-636

Pagurus spinulentus ( Henderson, 1888)

( Figs. 6–9)

Eupagurus spinulentus Henderson, 1888: 68 , pl. VII, fig. 3 [type locality: off Tablas Island, Philippines, 100–115 fathoms]; Alcock, 1905b: 176 (list); Forest, 1955: 106.

Eupagurus spinolentus (sic) – Estampador, 1937: 505 (list); 1959: 54 (list).

Pagurus spinulentus – McLaughlin & Forest, 1999: 308–309, fig. 1D, J, L; Gordan, 1956: 335 (bibliography); McLaughlin et al., 2010: 33 (list).

Not Eupagurus spinulentus – Stebbing, 1920: 260; Barnard, 1950: 460. = Pagurus prideaux Leach, 1815 .

Material examined. 1 male (sl 6.3 mm) ( ZRC 2014.0302 ), PANGLAO 2004, stn B9, Napaling , Panglao Island, 09°33.1'N, 123°44.0'E, caves in reef wall, 8–10 m, 8 June 2004 ; 1 male (sl 9.9 mm) ( ZRC 2014.0303 ), Balicasag Island , coll. Nato, May 2004 ; 1 male (sl 10.9 mm), 1 ovigerous female (sl 9.4 mm) ( NMCR 39116 ), stn P3, Balicasag Island , 09°31.1'N, 123°41.5'E, ca. 100 m, coll. local fishermen, 31 May 2004 , tangle nets; 1 female (sl 5.5 mm) ( ZRC 2014.0304 ), stn P5, Pamilacan Island , 09°30.0 ' N, 123°54.6'E, ca. 100 m, coll. local fishermen, 3 June 2004 , tangle nets; 1 male (sl 11.6 mm), 2 ovigerous females (sl 8.6, 8.8 mm) ( ZRC 2014.0305 ), PN1, Balicasag Island , coll. local fisherman, 28–29 May 2004 ; 1 male (sl 10.5 mm) ( CBM-ZC 12488 ), November ; 1 female (sl 10.0 mm) ( ZRC 2014.0306 ), Balicasag Island , coll. local fishermen, November 2003 , tangle nets.

Description. Eleven pairs of biserial gills.

Shield ( Fig. 6A) slightly wider than long; anterior margin between rostrum and lateral projections gently concave; anterolateral margins sloping; lateral margin with small but distinct, anteriorly directed process; posterior margin roundly truncate; dorsal surface slightly convex transversely, with few tufts of short setae on either side of midline; paragastric grooves shallow but conspicuous. Rostrum broadly rounded, not reaching level of lateral projections, with 1 pair of tufts of short setae. Lateral projections roundly triangular, each with or without small submarginal spine. Posterior carapace (not figured) approximately as long as shield; carapace lateral lobe moderately narrow, well calcified; cardiac sulci nearly parallel in anterior part and then extending posteriorly along posterolateral margin; sulci cardiobranchiales also nearly parallel, not reaching midlength of posterior carapace; posteromedian plate and posterolateral plates well calcified, with few tufts of very short setae; branchiostegite membranous, with scattered short to moderately long setae.

Ocular peduncles (including cornea) ( Fig. 6A) stout, increasing in width distally, about 0.7 times as long as shield; not inflated basally; cornea dilated, its width about 0.4 of peduncular length; dorsal surface with few tufts of short setae mesially, but no tuft of setae at base of cornea. Ocular acicles roundly subtriangular or subovate, separated basally by width of one acicle, each with small submarginal spine distally; dorsal surface slightly concave. Interocular lobe clearly visible, medially concave.

Antennular peduncles ( Fig. 6A), when fully extended, overreaching distal corneal margins by 0.5–0.8 length of ultimate segment. Ultimate segment about twice as long as penultimate segment, slightly widened distally in lateral view; dorsal surface with one moderately long seta near dorsolateral distal angle followed by three or four widely spaced individual setae, becoming shorter proximally. Basal segment with distolateral margin produced as short, setose process; lateral surface with 1 small spine distal to well inflated statocyst lobe; ventromesial distal angle slightly produced, subacutely pointed.

Antennal peduncles ( Fig. 6A) overreaching distal corneal margins by 0.2–0.3 length of fifth segment, with supernumerary segmentation. Fifth and fourth segments with some short to moderately long setae on lateral and mesial faces. Third segment with small spine at ventromesial distal angle obscured by prominent tuft of long setae. Second segment with dorsolateral distal angle strongly produced, almost reaching distal margin of fourth segment, terminating in bifid, acute spine, mesial margin of this projection with few minute spinules; dorsomesial distal angle with small spine; mesial margin with short setae. First segment with minute spinule on lateral face distally, occasionally hardly visible in dorsal view; ventrodistal margin with one prominent tooth lateral to excretory pore. Antennal acicle slightly overreaching distal corneal margin or midlength of fifth peduncular segment, gently sinuous, terminating in small spine partially obscured by tuft of long setae; dorsomesial margin with row of low, small protuberances bearing tufts of moderately long setae. Antennal flagellum exceeding 5 times of shield length; each article with two or three short to moderately long setae (1–5 articles length) every 8–12 articles.

Mouthparts not dissected. Third maxilliped ( Fig. 6B) moderately slender; carpus unarmed on dorsodistal margin; merus unarmed on distal and ventral margins; ischium with crista dentata consisting of clearly spaced corneous teeth increasing in size proximally, and with 1 strong accessory tooth ( Fig. 6C); basis-ischium fusion incomplete; basis with 1 spinule on mesial margin; exopod overreaching distal margin of carpus.

Chelipeds distinctly unequal and dissimilar. Right cheliped ( Figs.7A, B , 8A–C ) moderately stout, not particularly elongate even in males. Chela subtriangular or elongate subovate in dorsal view, about 2.0 times as long as wide; no hiatus between fingers; spines on dorsal surface acuminate, subconical, directed slightly distally, vast majority noncorneous-tipped. Dactylus subequal in length to or slightly longer than palm, nearly straight, overlapped by fixed finger distally; mesial half of dorsal surface unarmed but with longitudinal row of tufts of stiff setae, lateral half with scattered small spines and tufts of short pinnate setae; dorsomesial margin slightly delimited by single row of small spines; mesial surface with numerous small spines becoming two longitudinal rows distally and partially obscured by numerous tufts of long pinnate setae; ventral surface unarmed but with some longitudinal rows of short to moderately long pinnate setae; cutting edge with row of rounded or subtriangular calcareous teeth decreasing in size distally in proximal 0.9, and with minute corneous teeth in distal 0.1, terminating in small corneous claw. Palm about 0.8 times as long as carpus; dorsal surface gently convex, armed with numerous tiny to small spines almost scattered, and with shallow, unarmed longitudinal sulcus adjacent to dorsomesial margin; short tufts of pinnate setae (about equal in length to spines) arising anterior to bases of spines; dorsomesial margin delimited by single or double row of small spines, dorsolateral margin delimited by row of small spines decreasing in size distally; lateral surface with numerous small, simple or bifid spines becoming flattened and blunt ventrally, and with numerous tufts of long pinnate setae partially obscuring armature; mesial surface nearly flat, with numerous small spines or multispinose protuberances and tufts of moderately long stiff setae; ventral surface gently convex, with numerous small, low protuberances or tubercles, occasionally distally multidenticulate, each bearing tuft of short stiff setae. Fixed finger nearly straight, somewhat depressed dorsoventrally; dorsal surface and dorsolateral margin with small spines continued from palm; ventral surface unarmed, but with tufts of long stiff setae arranged in some longitudinal rows; cutting edge with large, rounded calcareous teeth and four or five small distal denticles, terminating in small calcareous claw. Carpus moderately widened distally, subequal in length to merus; dorsal surface with numerous scattered; small to moderately large spines extending onto sloping lateral surface and dense short to moderately short pinnate setae partially obscuring spines; shallow transverse groove present adjacent to dorsodistal margin; dorsodistal margin with row of minute to small spines; dorsomesial margin delimited by single row of moderately large spines; lateral surface with numerous small spines or spiniform tubercles partially obscured by dense pinnate setae, ventrolateral distal angle with 1 small spine; mesial surface shallowly concave in general, with scattered, numerous small spines or tubercles, partially obscured by numerous tufts of short to long pinnate setae; ventral surface convex, with numerous small tubercles obscured by dense pinnate setae, no pinhole-like foramen present (rarely shallow depression present). Merus with dorsal surface bearing irregular rows of short transverse ridges (sometimes marginally multidenticulate) becoming weak proximally, each ridge bearing tuft of short to long simple setae; dorsodistal margin with row of prominent spines decreasing in size laterally; lateral surface with sparse, minute spiniform tubercles and short, multidenticulate ridges dorsally, ventrolateral margin with row of small spines; mesial surface with scattered, minute tubercles and short vertical ridges dorsally and ventrally, and with tufts of short to moderately long setae arising from armature, ventromesial margin with row of small spines; ventral surface armed with numerous small spines and tubercles, and these armature completely or partially concealed by dense, short to moderately long pinnate setae. Ischium with row of small spiniform tubercles on ventromesial margin; ventrolateral and ventral surfaces with several spinules or minute spiniform tubercles. Coxa unarmed.

Left cheliped ( Fig. 8D–G ) moderately slender. Chela about 2.4–2.6 times as long as wide (greatest width at base of dactylus); no hiatus between fingers. Dactylus about 1.8 times as long as palm; surfaces with tufts of short to long pinnate setae partially obscuring armature; dorsal surface with partially double row of small spines on midline; mesial surface with numerous smaller spines, becoming two rows distally; ventral surface unarmed; cutting edge with row of small, slender corneous teeth on at least distal 0.7, terminating in moderately large corneous claw. Palm about half length of carpus; dorsal surface gently convex transversely with slightly elevated midline, armed with numerous small spines arranged in several irregular longitudinal rows, median row particularly conspicuous, and tufts of short pinnate setae arising distal to bases of spines; dorsomesial margin delimited by single row of small spines; dorsolateral margin delimited by row of small spines extending onto fixed finger; lateral surface with numerous small spines and multidenticulate protuberances and tufts of long simple setae; mesial surface with 2 rows of small spines dorsally and several multispinose protuberances ventrally, partially obscured by tufts of simple or pinnate setae; ventral surface gently convex, with low protuberances and tufts of long setae. Fixed finger with numerous small spines on dorsal surface, extending from palm; ventral surface with tufts of long simple setae arranged in 3 longitudinal rows; cutting edge of fixed finger with row of small, subacute calcareous teeth over entire length, terminating in small corneous claw. Carpus subequal in length to merus; surfaces with numerous tufts of short to long pinnate setae partially obscuring armature (setae on dorsolateral margin particularly long); dorsal surface very narrow, sloping mesially, with some minute spines; dorsolateral margin somewhat elevated, with partially double row of moderately large spines extending onto distal margin; dorsomesial margin with row of small spines; lateral surface with numerous small, simple or bifid spines, ventrolateral distal angle with tiny spine; mesial surface with numerous small simple or multifid spines; ventral surface nearly flat transversely, with scattered small tubercles, devoid of trace of depression or foramen. Merus with short, occasionally multidenticulate, transverse ridges and tufts of long simple setae on dorsal surface, dorsodistal margin with two or three prominent spines; lateral surface with small, multidenticulate ridges or minute tubercles, particularly conspicuous on ventral side, and with tufts of short to moderately long simple setae arising from armature, ventrolateral distal margin with row of moderately small spines; mesial surface with scattered, short vertical ridges (particularly conspicuous and multidenticulate on ventral side), and with tufts of simple setae, ventromesial distal margin with row of small spines or spiniform tubercles; ventral surface slightly convex, with numerous small spines or tubercles and tufts of moderately long simple setae. Ischium with row of tiny spines or denticles on ventromesial margin; lateral surface with vertical row of minute denticles adjacent to distal margin; ventral surface smooth, unarmed. Coxa unarmed.

Ambulatory legs ( Fig. 9A, F ) moderately long and slender in general, right second pereopod overreaching tip of extended right cheliped by half length of dactylus. Dactyli elongate, 1.6–1.8 times as long as propodi, 10.0–15.0 times longer than broad, in dorsal view slightly twisted, in lateral view gently curving ventrally; dorsal margins each with row of spinules or denticles in proximal 0.5–0.7 (those on left third smaller than on other legs) and with short to moderately short bristle-like stiff setae becoming shorter proximally (proximal setae interspersing spinules or denticles); lateral faces each with shallow median sulcus in proximal 0.3 and single row of short to moderately short bristle-like setae ventral to midline (these setae closely set in distal part, becoming more widely spaced and shorter toward proximal); mesial faces ( Fig. 9B, G ) each with widely spaced tufts of very short stiff setae dorsally and partially double row of moderately short, closely spaced bristle-like stiff setae ventrally ( Fig. 9C ; in third pereopods, proximal setae becoming widely spaced and shorter, showing like corneous spinules); ventral margins each with row of about 30–40 minute, slender, corneous spinules, these spinules closely spaced, partially overlap in distal part ( Fig. 9C ), becoming more widely spaced towards proximal end. Propodi somewhat narrowing distally; dorsal surfaces each with single or double row of small spines and sparse, short pinnate setae, dorsodistal margin with 1 spine (second) or unarmed (third); lateral surfaces with minute sharp granules dorsally and minute pits, these occasionally with tufts or single minute setae; mesial surfaces ( Fig. 9D, H ) almost glabrous, with several spinulose tubercles dorsally; ventral surfaces with scattered, minute spinulose tubercles or minute protuberances bearing minute setae (second) or almost smooth (third). Carpi each with row of small to moderately large spines decreasing in size proximally; lateral faces with scattered tufts of very short setae arising from very low, minute protuberances or minute pits. Dorsal surfaces of meri each with spinulose transverse ridges (second) or low, nonspinulose transverse ridges (third), and tufts of moderately long pinnate setae arising from these ornamentations; lateral and mesial faces almost glabrous; ventrolateral margins each with row of minute to small spines on distal 0.6 (second) or only with small distal spine (third), ventral surfaces with scattered small spines or tubercles extending to mesial faces (in second pereopods, armature more numerous in right than in left; Fig. 9E ), or some minute tubercles (third), all with tufts of moderately long pinnate setae. Ischia each with tiny tubercles ventromesially (second) or nearly smooth (third); short simple or pinnate setae on dorsal and ventral margins. Female with paired gonopores on coxae of third pereopods.

Fourth pereopods ( Fig. 6D) semichelate, stiff long setae on dorsal margins of dactyli to meri and ventral margin of meri. Dactyli strongly arcuate, terminating in small corneous claw, each with row of minute, closely spaced corneous teeth on ventral margin; no preungual process. Propodal rasp consisting of three to five rows of corneous scales.

Fifth pereopods chelate. Coxae ( Fig. 6E) of males each with gonopore partially masked by tuft of setae.

Thoracic sternite 3 with anterior margin nearly straight, with pair of minute denticles on either side of midpoint; ventral surface with prominent tuft of setae medially. Anterior lobe of thoracic sternite 6 ( Fig. 6F) broadly triangular, distinctly wider than long, skewed to left, armed anteriorly with one to three small spines or denticles and subdistal tuft of moderately long setae. Thoracic sternite 8 ( Fig. 6E) vertically compressed, weakly divided in two slightly asymmetrical lobes; anterior margin with row of moderately short setae, each anterolateral angle slightly produced.

Pleon dextrally twisted. Male with 3 (third to fifth) unpaired, very unequally biramous left pleopods (endopods greatly reduced, bud-like). Female with 4 (second to fifth) unpaired, unequally biramous left pleopods (in fifth, endopod greatly reduced, bud-like). Uropods markedly asymmetrical; protopods unarmed.

Telson ( Fig. 6G–I) with distinct lateral indentations; posterior lobes rounded, slightly unequal, median cleft V-shaped, each terminal margin with row of small to strong, corneous-tipped spines sometimes extending onto lateral margin (3–10 main spines on left, 3–9 on right, and some additional spinules on both lateral margins).

Coloration. In preservative. Entirely light grayish brown.

Distribution. Known only from the Philippines, at depths of 100– 207 m. The collection data from stn B9 (depths 8–10 m) for one male specimen (ZRC 2014.0302) is questionable.

Remarks. Pagurus spinulentus was originally described on the basis of a single ovigerous female from off Tablas Island, the Philippines, at depths of 100–115 fathoms (= 180–207 m) ( Henderson, 1888; as Eupagurus ). Since the original description, Stebbing (1920) and Barnard (1950) recorded the species from South Africa, but Forest (1955) concluded that the South African specimens actually represent P. prideaux Leach, 1815 after comparing with the holotype of P. spinulentus . McLaughlin & Forest (1999) clarified differentiating characters between P. cavicarpus and P. spinulentus , and published figures of some selected parts of the holotype of P. spinulentus . Komai et al. (2013) discussed differentiating characters between their new species P. spinossior and P. spinulentus , but their comparison was only based on the published accounts on the holotype of P. spinulentus . Other references of P. spinulentus ( Alcock, 1905b; Estampador, 1937, 1959; Gordan, 1956; McLaughlin et al., 2010) are faunal or bibliographic listings. Consequently, the present material represents the rediscovery of the species since the original description.

The present 10 specimens agree well with the account of P. spinulentus by McLaughlin & Forest (1999). McLaughlin & Forest (1999) noted that the median ventral foramen on the carpus of the right cheliped in the holotype of P. spinulentus was not depressed, nor is an actual opening present. In seven of the eight right chelipeds available for examination, there is no trace of such a depression; only one specimen (male, sl 6.3 mm, stn B9) has a very shallow, uncalcified depression on the ventral surface of the carpus of the right cheliped. It is reasonable to consider that this species normally lacks the ventral foramen.

As discussed by Komai et al. (2013), Pagurus spinulentus appears closest to P. spinossior . Komai et al. (2013) cited five characters to differentiate the two species, but the present study demonstrates that the presence or absence of a ventral depression on the right cheliped carpus is not valid as distinguishing character. Other characters (the setation of ventrodistal margins of cheliped meri, the dorsal armature of dactyli of second pereopods, the general setation of chelipeds and ambulatory legs, and the shape of the anterior lobe of thoracic sternite 6) are still valid. Furthermore, the armature of chelae is generally weaker in P. spinulentus than in P. spinossior .

McLaughlin & Forest (1999) cited five characters to differentiate P. spinulentus from P. cavicarpus , viz., the strength of the dorsolateral distal angle of the second segment of the antennal peduncle, the armature of the mesial surface of the dactylus and palm of the right cheliped, the armature of the dorsal surface of the carpus of the left cheliped, the setation of the ventrodistal margins of cheliped meri, and the general setation of the chelipeds and ambulatory legs. Our examination of the present newly collected specimens confirms the validity of these characters. In addition to them, the shape of the anterior lobe of sixth thoracic sternite 6 is useful to distinguish the two species: in P. spinulentus , the anterior lobe is strongly widened proximally with the basal width being greater than the length, whereas in P. cavicarpus , it is distinctly longer than wide ( McLaughlin & Forest, 1999). As noted by McLaughlin & Forest (1999), the right cheliped carpus usually has a pinhole-like foramen on the ventral surface in P. cavicarpus , which is always absent in P. spinulentus .

Figures

Fig. 7. Pagurus spinulentus (Henderson, 1888). A, B, Balicasag Island, male (sl 9.9 mm), ZRC 2014.0303. A, right cheliped, mesial view (setae omitted); B, same lateral view. Scale bar = 5 mm.

Fig. 8. Pagurus spinulentus (Henderson, 1888). A–G, Balicasag Island, male (sl 9.9 mm), ZRC 2014.0303. A, chela of right cheliped, dorsal view (setae omitted); B, carpus of right cheliped, dorsal view (setae omitted); C, same, ventral view; D, chela of left cheliped, dorsal view (setae omitted); E, left cheliped, mesial view; F, same, lateral view; G, carpus of left cheliped, dorsal view. Scale bar = 5 mm.

Fig. 9. Pagurus spinulentus (Henderson, 1888). A–H, Balicasag Island, male (sl 9.9 mm), ZRC 2014.0303.A, right second pereopod, lateral view; B, same, dactylus, mesial view (only mesial setae shown); C, same, distal part, ventral view; D, same, propodus and carpus, mesial view (setae omitted); E, same, merus, mesial view (setae omitted); F, left third pereopod, lateral view (claw of dactylus broken off); G, same, dactylus, mesial view; H, same, propodus and carpus, mesial view (setae omitted). Scale bars = 5 mm for A, B, D–H; 1 mm for C.