Pagurus spinossior, Komai, Tomoyuki, Reshmi, Rema & Kumar, Appukuttan Nair Biju, 2013

Komai, Tomoyuki, Reshmi, Rema & Kumar, Appukuttan Nair Biju, 2013, Rediscovery and range extension of Ciliopagurus liui Forest, 1995 and description of a new species of Pagurus Fabricius, 1775 (Crustacea: Decapoda: Anomura: Paguroidea) from the Kerala State, southwestern India, Zootaxa 3710 (5), pp. 467-484 : 475-483

Pagurus spinossior n. sp.

( Figs 6–10 )

Material examined. Holotype: off Neendakara, Kerala State, India, 08°44’N, 75°59’E, 50 m, 24 May 2011, male (sl 8.7 mm), CBM-ZC 11807.

Description. Eleven pairs of biserial gills.

Shield ( Fig. 7 A) slightly wider than long; anterior margin between rostrum and lateral projections slightly concave; anterolateral margins sloping; posterior margin truncate; dorsal surface slightly convex transversely, with tufts of short setae on either side of midline; paragastric grooves faint. Rostrum broadly rounded, reaching level of lateral projections. Lateral projections roundly triangular, with conspicuous marginal spine directed outward. Posterior carapace ( Fig. 6 ) approximately as long as shield; posteromedian plate narrow, well calcified.

Ocular peduncles (including cornea) ( Fig. 7 A) stout, increasing in width distally, about 0.6 times as long as shield; not inflated basally; cornea dilated, its width about 0.6 of peduncular length; dorsal surface with longitudinal row of tufts of stiff setae. Ocular acicles roundly subtriangular, separated basally by width of one acicle, with small submarginal spine distally; dorsal surface nearly flat. Interocular lobe clearly visible, medially concave.

Antennular peduncles ( Fig. 7 A), when fully extended, overreaching distal corneal margins by 0.7 of ultimate segment. Ultimate segment about 1.6 times as long as penultimate segment, slightly widened distally in lateral view, with row of few long setae on dorsal surface. Basal segment with distolateral margin distinctly produced as short, setose process; statocyst lobe weakly inflated, with prominent spine distolaterally; ventromesial distal angle slightly produced, bluntly pointed.

Antennal peduncles ( Fig. 7 A) slightly overreaching distal corneal margins, with supernumerary segmentation. Fifth and fourth segments with few setae distally. Third segment with small spine at ventromesial distal angle. Second segment with dorsolateral distal angle strongly produced, reaching distal margin of fourth segment, terminating in bifid, acute spine; dorsomesial distal angle with tiny spine; mesial and lateral faces with several short setae. First segment with spinule on lateral face; ventrodistal margin with 1 prominent spine lateral to excretory pore. Antennal acicle slightly overreaching distal corneal margin, slightly sinuous, terminating in small spine; dorsomesial margin with sparse tufts of long setae. Antennal flagellum about 4 times as long as shield; each article with 3 long setae (about 8 articles length) every 12–15 articles.

Mouthparts not dissected. Third maxilliped ( Fig. 7 B) moderately slender; carpus unarmed on dorsodistal margin; merus with 1 tiny spine on dorsodistal margin, unarmed on ventral margin; ischium with crista dentata consisting of clearly spaced corneous teeth increasing in size proximally, and with 1 strong accessory tooth ( Fig. 7 C); basis-ischium fusion incomplete; basis with 1 spinule on mesial margin; exopod reaching midlength of carpus.

Chelipeds distinctly unequal and dissimilar ( Fig. 6 ). Right cheliped ( Figs. 8 A, B; 9A–C) moderately stout, not particularly elongate. Chela subovate in dorsal view, about 2.0 times as long as wide; no hiatus between fingers; spines on dorsal surface subconical, usually corneous-tipped. Dactylus subequal in length to palm, nearly straight, overlapped by fixed finger distally; dorsal surface with longitudinal row of small spines on midline, dorsomesial margin delimited by double row of small to moderately large spines; all surfaces with scattered tufts of short to moderately long setae, mesial surface with row of small spines becoming double row proximally; cutting edge with row of low, rounded calcareous teeth in proximal 0.8, and with row of minute corneous teeth in distal 0.2, terminating in small corneous claw. Palm about 0.8 times as long as carpus; dorsal surface gently convex, armed with numerous small to large spines arranged in about 10 irregular longitudinal rows and tufts of long stiff setae each arising at just anterior to base of spine; dorsomesial margin delimited by double row of small to large spines, dorsolateral margin not clearly delimited; lateral surface with numerous scattered small spines or tubercles and tufts of short to long stiff setae; mesial face flat, perpendicular, with numerous, closely spaced small spiniform tubercles and sparse stiff setae; ventral surface gently convex, with scattered small, low tubercles or protuberances, each bearing tufts of stiff setae. Fixed finger nearly straight, somewhat depressed dorsoventrally, dorsal surface and dorsolateral margin with longitudinal rows of large spines continued from palm, ventral surface unarmed, with tufts of long stiff setae arranged in some longitudinal rows; cutting edge with low, blunt calcareous teeth in proximal half, faintly crenulate in distal half, terminating in minute corneous claw. Carpus moderately widened distally, subequal in length to merus; dorsal surface covered with scattered numerous small spines or spiniform tubercles and tufts of long stiff setae, dorsodistal margin with row of tiny spines, dorsolateral margin not delimited; dorsomesial margin with double row of large spines; lateral surface armed with numerous small spines or spiniform tubercles and tufts of stiff setae continuing from dorsal surface; mesial surface also with scattered numerous small tubercles or spines and tufts of long stiff setae; ventral surface convex, with numerous long setae mesially, devoid of even trace of shallow depression or foramen ( Fig. 9 C). Merus with irregular rows of short transverse ridges (sometimes marginally multidenticulate) becoming weak proximally, each ridge bearing tuft of short to long stiff setae; dorsodistal margin with 4 prominent spines decreasing in size laterally; lateral surface with short, multidenticulate ridges in dorsal half (becoming weak proximally), nearly smooth in ventral half, ventrolateral margin with row of large spines becoming smaller proximally; mesial surface generally with scattered minute, low tubercles and tufts of short setae, and ventrally with several multidenticulate tubercles, ventromesial margin with row of small tubercles; ventral surface armed with numerous small spines and tubercles, and tufts of moderately long stiff setae. Ischium with row of small spiniform tubercles on ventromesial margin; ventrolateral distal angle with 2 small spines, lateral surface with some small tubercles. Coxa unarmed.

Left cheliped ( Fig. 9 D–F) moderately slender. Chela about 2.4 times as long as wide (greatest width at base of dactylus), with numerous tufts of short to long setae on surfaces; no hiatus between fingers. Dactylus approximately twice longer than palm; dorsal surface with partially double row of large slender spines decreasing in size on midline; mesial surface with row of small spines or tubercles, becoming double row proximally, on midline; ventral surface unarmed; cutting edge with row of small, slender corneous teeth, terminating in moderately large corneous claw. Palm about half length of carpus; dorsal surface slightly convex transversely, armed with large slender spines arranged in 5 irregular longitudinal rows; dorsomesial margin with partially double row of large spines; dorsolateral or lateral margin not clearly delimited, but with row of large spines extending onto fixed finger; mesial surface armed with numerous, closely spaced small spines or tubercles; ventral surface with scattered low protuberances and lateral spiniform tubercles; cutting edge of fixed finger with row of small, rounded calcareous teeth interspersed by sets of 2–5 partially fused small corneous teeth, terminating in moderately small corneous claw. Carpus slightly shorter than merus, with tufts of short to long stiff setae each arising from armature on every surface; dorsal surface very narrow, dorsolateral margin with row of large spines, dorsomesial margin with row of small spines or tubercles becoming smaller and lower proximally; lateral surface with numerous small spines or tubercles, ventrolateral distal angle with moderately large spine; mesial surface with low protuberances of various size, becoming spiniform tubercles or small spines distally; ventral surface slightly convex, with scattered small tubercles, devoid of even trace of depression or foramen. Merus with short, sometimes multidenticulate transverse ridges on dorsal surface, dorsodistal margin with 1 prominent spine; lateral surface with small, multidenticulate ridges or tubercles, particularly conspicuous on ventral side, and tufts of short to moderately long setae, ventrolateral distal margin with 4 spines; mesial surface with low protuberances dorsally and multidenticulate tubercles ventrally, and with few tufts of stiff setae, ventromesial distal margin with row of tiny tubercles; ventral surface slightly convex, with numerous small spines or tubercles and tufts of moderately long stiff setae. Ischium with row of tiny spines or tubercles on ventromesial margin; ventrolateral angle with cluster of 4 small spines, lateral surface also with cluster of tiny tubercles. Coxa unarmed.

Ambulatory legs ( Figs. 6 , 10 A, B, E) moderately long and slender, right second pereopod overreaching tip of extended right cheliped by half length of dactylus. Dactyli 1.7–1.8 times as long as propodi, 11.0–12.0 times longer than broad, in dorsal view slightly twisted, in lateral view gently curving ventrally; dorsal margins each with row of numerous bristle-like setae, but without conspicuous spines or spinules; lateral faces each with shallow median sulcus and single or double row of long stiff setae decreasing in length distally; mesial faces also shallowly sulcate medially, with row of tufts of long bristle-like setae (dorsal) and row of bristle-like setae (ventral) flanking median sulcus (second) or only with row of bristle-like setae ventral to median sulcus ( Fig. 10 C, F); ventral margins each with row of 25–30 minute slender corneous spinules ( Fig. 10 D). Propodi distinctly longer than carpi, somewhat narrowing distally; dorsal surfaces each with double row of small spines and tufts of moderately short setae, dorsodistal margin with 1 spine (second) or unarmed (third); lateral surfaces with sparse tufts of short setae; mesial surfaces almost glabrous; ventral surfaces each with 2 rows of tufts or single setae, without corneous spinules. Carpi each with row of moderately large spines decreasing in size proximally; lateral faces with some scattered tufts of short setae. Dorsal surfaces of meri each with multidenticulate transverse ridges and minute tubercles, and tufts of setae arising from these ornamentations (second) or with very low protuberances bearing tufts of setae (third); lateral and mesial faces almost glabrous except for few tufts of short setae; ventrolateral distal margins each with 1 or 2 tiny spines (second) or unarmed (third), ventral surfaces each with 2 or 3 irregular rows of small spines or tubercles (second, armature more numerous in right than in left), single row of small tubercles (right third), or unarmed (left third), all with tufts of long stiff setae. Ischia unarmed, each with moderately short setae on dorsal and ventral margins.

Fourth pereopods ( Fig. 7 D) semichelate, stiff long setae on dorsal margins of dactyli to meri and ventral margin of meri. Dactyli gently curved, terminating in prominent corneous claw, each with row of minute, closely spaced corneous teeth on ventral margin; no preungual process. Propodal rasp consisting of 3 or 4 rows of corneous scales.

Fifth pereopods chelate. Coxae ( Fig. 7 F) each with gonopore partially masked by tuft of setae.

Thoracic sternite 3 with anterior margin nearly straight, with pair of spinule on either side of midpoint; ventral surface with prominent tuft of setae medially. Anterior lobe of thoracic sternite 6 ( Fig. 7 E) triangular, approximately as long as wide, distinctly skewed to left, terminating anteriorly in 2 small spines and with 2 additional small spines on either side of apex and with some stiff setae subdistally. Thoracic sternite 8 ( Fig. 7 F) divided in two similar lobes by shallow median groove, each anterolateral angle slightly produced.

Pleon dextrally twisted ( Fig. 6 ). Male with 3 unpaired, very unequally biramous left pleopods (third to fifth pleopods). Uropods markedly asymmetrical; protopods unarmed.

Telson ( Fig. 7 G) with distinct lateral indentations; posterior lobes rounded, slightly unequal, median cleft Vshaped, each terminal margin with row of small corneous spines extending onto lateral margin (15 on left, 13 on right).

Coloration in formalin ( Fig. 6 ). Shield, antennae, chelipeds and ambulatory legs generally light tan. Ocular peduncles with purple tint distally. Ambulatory legs with tinge of pale brown on distal and proximal parts of propodi and meri and ventral parts of carpi.

Distribution. Known only from the type locality, off Neendakara, Kerala State, at a depth of 50 m.

Biocoenoses. At the time of capture, the specimen was naked.

Remarks. Pagurus spinossior n. sp. appears closest to P. spinulentus , the latter is so far represented only by the holotype from the Philippines (McLaughlin & Forest 1999). The two species share many diagnostic characters, including the rounded rostrum, dilated corneas, long antennal peduncle and acicle reaching beyond the distal corneal margin, the strongly produced dorsolateral distal angle of the second segment of the antennal peduncle, the generally strongly spinose chelipeds, the clearly defined, strongly spinose mesial surface of the palm of the right cheliped, and the dorsally spinose or spinulose propodi and carpi of the ambulatory legs. Nevertheless, the new species can be easily distinguished from P. spinulentus by the following characters (cf. Henderson 1888; McLaughlin & Forest 1999): (1) the carpus of the right cheliped is devoid of a ventral foramen in P. spinossior n. sp., but in P. spinulentus , it bears a moderately large median foramen, though an actual opening is not present; (2) the ventrodistal margins of the meri of the chelipeds do not have any prominent setation in P. spinossior n. sp., whereas they each carry a dense fringe of pinnate setae in P. spinulentus ; (3) the dactyli of the second pereopods are smooth on the dorsal surface in P. spinossior n. sp., rather than spinulose in P. spinulentus ; (4) setae on the chelipeds and ambulatory legs consist only of simple setae in P. spinossior n. sp., but they are a mixture of simple and pinnate setae in P. spinulentus ; (5) the anterior lobe of thoracic sternite 6 is approximately as long as wide in the new species, rather than distinctly wider than long in P. spinulentus ; (6) spines on the posterior lobes of the telson are more numerous in P. spinossior n. sp. than in P. spinulentu s (15 on left and 13 on right versus nine on both sides).

Pagurus cavicarpus (Paul’son, 1875), a species known also from Indian waters (Alcock 1905, as Eupagurus carpoforaminatus var. nephromma Alcock, 1905 ; McLaughlin & Forest 1999), is also substantially similar to the present new species, but the former differs from the latter in the short dorsolateral distal angle of the second segment of the antennal peduncle, the presence of a deep ventral foramen on each carpus of chelipeds, distinctly weaker spines on the palms of the chelipeds, spinulose dorsal margins of the second pereopods, and fewer marginal spines on the posterior lobes of the telson (McLaughlin & Forest 1999).

From waters around India, the following seven species of Pagurus have been recorded (Alcock 1905; Sankolli 1961): Pagurus carpoforaminatus (Alcock, 1905) , P. cavicarpus (Paul’son, 1875), P. hirtimanus (Miers, 1880) , P. investigatoris (Alcock, 1905) , P. kulkarnii Sankolli, 1961 , P. macardlei (Alcock, 1905) , and P. pergranulatus (Henderson, 1896) . The present new species is the eighth of the genus known from India.

Etymology. The specific epithet “ spinossior ” (= most spinose) refers to the strong armature on the chelipeds of this new species.

Figures

FIGURE 6. Pagurus spinossior n. sp., holotype, male (sl 8.7 mm), CBM-ZC 11807, entire animal in dorsal view, showing coloration in formalin preservative.

FIGURE 7. Pagurus spinossior n. sp., holotype, male (sl 8.7 mm), CBM-ZC 11807. A, shield and cephalic appendages, dorsal view; B, left third maxilliped, lateral view; C, same, ischium, ventral view, showing crista dentata and accessory tooth; D, dactylus to carpus of left fourth pereopod, lateral view; E, sixth thoracic sternite, ventral view; F, coxae of fifth pereopods and eighth thoracic sternite, ventral view. Scale bars: 5 mm for A; 2 mm for B, D – F; 1 mm for C.

FIGURE 8. Pagurus spinossior n. sp., holotype, male (sl 8.7 mm), CBM-ZC 11807. A, right cheliped, mesial view (setae omitted); B, same, lateral view. Scale bar: 2 mm.

FIGURE 9. Pagurus spinossior n. sp., holotype, male (sl 8.7 mm), CBM-ZC 11807. A, right chela, dorsal view (setae omitted); B, carpus of right cheliped, dorsal view; C, same, ventral view; D, chela and carpus of left cheliped, dorsal view; E, left cheliped, mesial view; F, same, lateral view. Scale bar: 2 mm.

FIGURE 10. Pagurus spinossior n. sp., holotype, male (sl 8.7 mm), CBM-ZC 11807. A, right second pereopod, lateral view; B, same, mesial view (setae omitted except for mesial setae on dactylus); C, same, dactylus, mesial view, only mesial setae shown; D, same, distal part, mesial view; E, left third pereopod, lateral view; F, same, dactylus, mesial view, only mesial setae shown. Scale bars: 5 mm for A – C, E, F; 1 mm for D.