Pagurus pergranulatus ( Henderson, 1896 )

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 : 623-629

publication ID	https://doi.org/ 10.5281/zenodo.5355008
publication LSID	lsid:zoobank.org:pub:DF60AAD1-1B35-4328-9131-E3ADFC06B6AD
persistent identifier	https://treatment.plazi.org/id/03810513-FF92-0155-03C9-83FAFAC1FA54
treatment provided by	Tatiana
scientific name	Pagurus pergranulatus ( Henderson, 1896 )
status

Treatment

Pagurus pergranulatus ( Henderson, 1896) View in CoL

( Figs. 1D View Fig , 2–5 View Fig View Fig View Fig View Fig )

Eupagurus pergranulatus Henderson, 1896: 520 View in CoL [type locality: off east coast of Ceylon ( Sri Lanka), 28 fathoms]; Alcock & Anderson, 1897: pl. 31, fig. 1; Alcock, 1905b: 125, pl. 11, fig. 1.

Pagurus pergranulatus View in CoL – Gordan, 1956: 333 (bibliography); Haig & Ball, 1988: 190; Rahayu, 1996: 350; McLaughlin, 1997: 526 (key); Davie, 2002: 84; McLaughlin et al., 2010: 34 (list).

Material examined. 1 ovigerous female (sl 6.0 mm) ( ZRC 2014.0301 View Materials ), PANGLAO 2004, stn R16, Black Forest , Balicasag Island, 09°31.1'N, 123°41.3'E, 6–22 m, edge of reef platform and slope, 4 June 2004 GoogleMaps .

Description. Eleven pairs of biserial gills.

Shield ( Fig. 2A View Fig ) approximately as long as broad; anterior margins between rostrum and lateral projections gently concave; anterolateral margins sloping; posterior margin roundly truncate; dorsal surface slightly convex transversely, with longitudinal row of tufts of moderately long setae on either side of midline; paragastric grooves faint. Rostrum acutely triangular, extending as far as level of lateral projections. Lateral projections roundly triangular, with small submarginal spine. Posterior carapace (not figured), measured along midline, distinctly shorter than shield; carapace lateral lobe moderately narrow, sclerotised but not strongly calcified; cardiac sulci parallel, reaching to midlength of posterior carapace; sulci cardiobranchiales also parallel, slightly falling short of midlength of posterior carapace; median area consisting of posteromedian and posterolateral plates not calcified but weakly sclerotised, with several paired tufts of stiff setae; branchiostegite membranous, with scattered tufts of short to moderately long, stiff setae.

Ocular peduncles (including corneas) ( Fig. 2A View Fig ) moderately stout, about 0.8 times as long as shield; slightly inflated basally; cornea slightly dilated, its width about 0.4 of peduncular length; dorsal surface with longitudinal row of tufts of moderately short setae mesially. Ocular acicles narrowly subtriangular with rounded tips, separated basally by width of more than one acicle, with minute submarginal spine distally (left) or spine missing (right); dorsal surface shallowly concave. Interocular lobe partially overhung by rostrum, medially concave.

Antennular peduncles ( Fig. 2A View Fig ), when fully extended, slightly falling short of distal corneal margins. Ultimate segment about 1.3 times as long as penultimate segment, slightly widened distally in lateral view, with 1 short seta at dorsolateral distal angle. Basal segment with distolateral margin produced in rounded lobe; statocyst lobe weakly inflated, with prominent spine distally; ventromesial distal angle not produced, bearing tuft of long stiff setae.

Antennal peduncles ( Fig. 2A View Fig ) overreaching corneal bases but not reaching distal corneal margins, with supernumerary segmentation. Fifth segment with few setae laterally. Fourth segment with 1 prominent subdistal tuft of stiff setae mesially. Third segment unarmed on ventromesial distal angle, with several tufts of long stiff setae mesially. Second segment with dorsolateral distal angle slightly overreaching midlength of fourth segment, terminating in bifid spine; dorsomesial distal angle with small spine; mesial and lateral faces with short to long stiff setae. First segment with subterminal spinule on lateral face; ventrodistal margin with cluster of spinules just lateral to excretory pore. Antennal acicle overreaching base of cornea but not reaching distal corneal margin, gently arcuate, terminating in small spine obscured by long stiff setae; dorsomesial margin with several tufts of long stiff setae. Antennal flagellum about 3 times as long as shield; each article with 1 or 2 minute setae on distal margin.

Mouthparts not dissected. Third maxilliped ( Fig. 2B View Fig ) moderately slender; dactylus shorter than propodus; carpus unarmed on dorsodistal margin; merus unarmed on dorsodistal and ventral margins; ischium with crista dentata consisting of narrowly spaced, moderately small, blunt to subacute corneous teeth, and with 3 moderately strong accessory teeth ( Fig. 2C View Fig ); basis-ischium fusion incomplete; basis with 2 denticles on mesial margin; exopod reaching distal margin of merus.

Chelipeds grossly unequal. Right cheliped ( Figs. 3A–D View Fig ) with chela 1.5 times longer than greatest width at base of dactylus, generally suboval in outline in dorsal view. Dactylus subequal in length to palm and slightly overlapped by fixed finger, slightly curved ventrally; dorsal surface with sparse, short feathered setae and prominent median row of broadbased, closely set spines or spine-like tubercles; dorsomesial margin with closely set, moderately large tubercles decreasing in size distally; space between dorsal midline and dorsomesial margin with small, low tubercles each bearing central or subdistal, slender, proximally directed and curved capsule; ventral surface with row of low, moderately large protuberances adjacent to mesial margin and tufts of moderately short stiff setae arranged in longitudinal rows; cutting edge with row of broad calcareous teeth and adjacent row of tufts of stiff setae, terminating in large calcareous claw. Palm distinctly longer than carpus; dorsomesial margin delimited by single row of moderately large, stout spines, dorsomesial distal angle somewhat produced with few small spines; dorsolateral margin delimited by small, sharp, forwardly directed spines extending onto fixed finger and decreasing in size and sharpness distally; dorsal surface convex, with numerous, small, scattered capsulate spines and row of moderately small, acute spines on proximal half of midline; vast majority of capsulate spines bifid terminally, flanking base of each capsule, sometimes bearing tuft of short to moderately long feathered setae ( Fig. 3E, F View Fig ); capsules similar to those on dactylus; mesial face with scattered, very low, small protuberances and tufts of short stiff setae; ventrolateral surface with scattered, very low, minute to small protuberances and sparse very short setae; ventral surface gently convex, with some low protuberances accompanied by tufts of long setae. Cutting edge of fixed finger with row of low calcareous teeth, terminating in large calcareous claw. Carpus slightly shorter than merus; dorsomesial margin delimited by row of large sharp spines accompanied by tufts of long stiff setae; dorsal surface with scattered, small to moderately large spines and tufts of short to long stiff setae, dorsodistal margin with row of small spines; dorsolateral margin delimited by row of small spines; lateral surface with some very low, small protuberances, all accompanied by tufts of short stiff setae, ventrolateral margin with 1 small distal spine; mesial surface shallowly concave medially, with some low protuberances, all accompanied by tufts of long stiff setae; ventral surface with distal margin strongly raised, fringed with long stiff setae. Merus unarmed on dorsodistal margin; dorsal surface glabrous; lateral surface nearly glabrous except for few tufts of short setae, ventrolateral margin with row of small sharp spines and some small, low tubercles proximally; mesial surface with sparse tufts of short setae, ventromesial margin slightly elevated, with row of closely spaced small spines or tubercles; ventral surface with some low, blister-like protuberances and tufts of moderately long setae. Ischium with tufts of short setae on all surfaces; ventromesial margin with few denticles.

Left cheliped ( Fig. 4A–C View Fig ) slightly overreaching base of dactylus of right cheliped, moderately compressed laterally. Chela elongate subovate in dorsal view, 2.7 times longer than greatest width at base of dactylus. Dactylus distinctly longer than palm, nearly straight with ventrally curved tip; dorsal surface sloping mesially, unarmed but with sparse tufts of short feathered setae; all surfaces with tufts of moderately short to long stiff setae; cutting edge with row of minute, subacute calcareous denticles in proximal 0.4 and row of minute, closely set corneous teeth in distal 0.6, terminating in small corneous claw. Palm about half length of carpus, subtriangular in cross section; dorsal surface elevated in midline but not forming distinct ridge or crest, with double row consisting of capsulate tubercles or small spines extending onto base of fixed finger; lateral margin with row of small acute spines; dorsolateral surface with capsulate tubercles arranged in irregular longitudinal rows and extending onto proximal half of fixed finger; dorsomesial surface sloping to mesial surface, with few low protuberances accompanied by tufts of long stiff setae; ventral surface with tufts of long setae. Fixed finger with cutting edge bearing row of minute calcareous denticles in proximal 0.7, and bearing corneous plate, fused with terminal claw, in distal 0.3. Carpus subequal in length to merus; dorsolateral margin with row of small sharp spines and low protuberances and with tufts of short feathered setae, no spine located at distal angle; dorsomesial margin with row of moderately small to large spines, 3 clustered spines located at distal angle; lateral surface with some very low protuberances accompanied by tufts of setae, ventrodistal angle produced, bearing 4 small spines; mesial surface also with very low protuberances accompanied by tufts of long stiff setae, ventrodistal angle with 1 small spine; ventral surface with prominent row of tufts of long feathered setae laterally and scattered tufts of long stiff setae on remaining part. Merus unarmed on dorsodistal margin; dorsal surface with sparse short stiff setae; lateral surface nearly glabrous except for few proximoventral tufts of setae, ventrolateral margin with row of slender, sharp spines and long stiff setae; mesial surface also nearly glabrous except for row of tufts of stiff setae adjacent to dorsal margin and few similar tufts near ventral margin, ventromesial margin with row of long setae and 3 proximal spines; ventral surface with 1 small spine medially and 1 prominent protuberance laterally. Ischium with 4 minute to tiny denticles on ventromesial margin; surfaces unarmed but with tufts of short to moderately long stiff setae.

Ambulatory legs ( Fig. 5A, D View Fig ) moderately long and stout, right second pereopod overreaching tip of extended right cheliped by half length of dactylus. Dactyli 1.0–1.3 times as long as propodi, 6.3–6.5 times longer than broad, in dorsal view nearly straight, in lateral view slightly curving ventrally; dorsal margins each with row of tufts of short to moderately long setae; lateral faces each without median sulcus; mesial faces also devoid of median sulcus, armed with 1 row (second; Fig. 5B View Fig ) or 2 rows (third; Fig. 5E View Fig ) of corneous spinules adjacent to dorsal margin; ventral margins each with row of 7 small corneous spines increasing in size distally. Propodi not narrowing distally; dorsal surfaces unarmed but with row of long stiff setae; lateral and mesial surfaces with few tufts of long stiff setae; ventral surfaces with few tufts of long stiff setae at least distally and with 1 or 2 corneous spinules on distal half, ventrodistal margins with 4 (second) or 2 (third) spinules mesially. Carpi each with small dorsodistal spine; dorsal margin with 1 additional spine at midlength (second; Fig. 5A, C View Fig ) or unarmed (third; Fig. 5D View Fig ) and with row of tufts of long stiff setae; lateral surface convex, with row of tufts of long stiff setae along midline. Meri each with row of tufts of long stiff setae on dorsal surface; lateral surface almost smooth, with few tufts of long stiff setae distally; ventral surface unarmed but with row of tufts of short to long stiff setae, ventrodistal lateral margin unarmed. Ischia unarmed but with tufts of setae on dorsal and ventral margins.

Fourth pereopods ( Fig. 2D View Fig ) semichelate, similar from right to left, but left slightly shorter than right. Dactylus slightly curved ventrally, terminating in elongate corneous claw (about half-length of corps of dactylus); distal 0.6 of opposable surface with lateral row of long corneous teeth and dense mat of setae increasing in length distally, proximal 0.4 glabrous; preungual process rod-like, reaching midlength of terminal claw. Propodal rasp consisting of about 8 rows of corneous scales. All segments with dorsal and/or ventral tufts of long stiff setae.

Thoracic sternite 3 with anterior margin nearly straight, with microscopic denticle on either side of midpoint; ventral surface with prominent tuft of setae medially. Anterior lobe of thoracic sternite 6 ( Fig. 2E View Fig ) subsemicircular, bisected by blunt transverse ridge, sloping anterior surface masked by numerous long setae. Thoracic sternite 8 divided in 2 lobes by shallow median groove, each anterolateral angle slightly produced, with prominent tuft of moderately long setae.

Pleon dextrally twisted ( Fig. 1D View Fig ). Female second to fifth pleopods greatly unequally biramous with much elongate exopods; length fourth>fifth>third>second.

Telson ( Fig. 2F View Fig ) with distinct lateral indentations; posterior lobes strongly produced, rounded, unequal, median cleft very deep; each terminal margin with partially double row of numerous slender spines extending onto lateral margin.

Coloration in life. Fig. 1D View Fig . Shield mottled pale purple and white, with complex pattern of thin lines of dark purple. Ocular peduncles basically whitish; narrow tan ring at base of cornea and broad orange band medially; cornea mottled silver. Antennular peduncles orange, ultimate segment with white distal and proximal rings, penultimate segment with white distal ring. Antennal peduncle generally pale purple; second segment with 3 dark purple longitudinal stripes on dorsal surface; flagellum with alternating bands of purple (3 or 4 articles length) and white (1 or 2 articles length). Right cheliped mottled purple and white in general; mesial surfaces of carpus and merus with irregular patterns of purple on white background. Left cheliped with thin purple lines on white background on chela, carpus and merus. Ambulatory legs with thin purple lines on propodi, carpi, meri and ischia; dactyli each with 1 purple median line and 2 broad purple bands (1 subdistal and 1 proximal). Narrow purple lines on chelipeds and ambulatory legs usually not reaching ends of segments, somewhat irregular in form, occasionally broadening and becoming thinner again on each segment.

Distribution. Sri Lanka, Andaman Islands, Peninsular Malaysia, Indonesia (Seram), Australia (Queensland), at depths of 15– 100 m. Newly recorded from the Philippines, at depths of 6– 22 m.

Remarks. The presence of capsules on the chelae is known in eight species in Pagurus , viz., P. capsularis McLaughlin, 1997 , P. hirtimanus , P. japonicus ( Stimpson, 1858) , P. pergranulatus , P. rubrior Komai, 2003b , P. similis ( Ortmann, 1892) , P. sinuatus ( Stimpson, 1858) , and P. tabataorum Osawa, 2012 ( McLaughlin, 1997; Komai, 2003b; Osawa, 2012). All the eight species exclusively occur in the Indo- West Pacific region. Osawa (2012) suggested that these species are phylogenetically related based on this possibly synapomorphic character, although no informal species group has been proposed for them. These species also share a rather uncommon feature in the genus, the possession of a left unpaired second pleopod in males ( Komai, 2003b; personal observation).

Although no detailed morphological description in modern standard has been published for P. pergranulatus , the present specimen generally agrees with the previous descriptions by Henderson (1896) and Alcock (1905b) except for the ventromesial margin of the merus of the right cheliped, which develops into a distinct, somewhat wing-like, ventrally produced lobe and bears a dense tuft of setae. However, no such development of a distinct ventromesial lobe of the merus of the right cheliped is seen in our female specimen. Komai (2003b) showed that the structure of the ventral part of the merus of the right cheliped could be sexually dimorphic in P. japonicus , P. rubrior and P. similis , and it is reasonable to consider that the discrepancy could be attributable to sexual difference also in P. pergranulatus . The coloration in life of our specimen also agrees well with the description given by Haig & Ball (1988).

Pagurus pergranulatus is immediately distinguished from the other seven related species shown above by the characteristic armature of the right palm: the dorsomesial distal angle of the right palm is somewhat produced; vast majority of the capsulate spines on the dorsal surface are distally bifid. In the other seven species, the distomesial margin of the right palm is not produced; capsulate tubercles on the dorsal surface are variable in the shape, but never bifid in the six species other than P. tabataorum . P. tabataorum has transverse scutes but no spines on chelae. The coloration in life of P. pergranulatus is also quite characteristic, particularly in having thin lines or stripes of dark purple on the shield, chelipeds and ambulatory legs. No such lines or stripes are seen in the other seven species (cf. Miyake, 1982 for P. japonicus ; McLaughlin, 1997 for P. capsularis ; Komai, 2003b for P. rubrior and P. similis ; Poore, 2004 for P. sinuatus ; McLaughlin et al., 2010 for P. hirtimanus ; Osawa, 2012 for P. tabataorum ).