Pylopaguropsis similis, Komai, 2013

Komai, Dwi Listyo Rahayu Tomoyuki, 2013, Two New Species Of Pylopaguropsis Alcock (Crustacea: Decapoda: Anomura: Paguridae) From The Philippines, Raffles Bulletin of Zoology 61 (2), pp. 621-631 : 626-630

Pylopaguropsis similis , new species

( Figs. 4 , 5 )

Material examined. — Holotype, male (4.3 mm) (NMCR-39096), Balicasag Island , Philippines, coll. local fisherman, Jul.2003.

Paratypes: 1 female (8.2 mm) ( MNHN), same data as holotype ; 1 female (7.4 mm) ( ZRC.2013.0868) Pamilacan Island , Stn. P 5, 9°30.0'N, 123°54.6'E, tangle nets from local fishermen, ca. 100 m, 3 Jun.2004 .

Description. — Thirteen pairs of biserial gills.

Shield approximately as long as broad ( Fig. 4A ); anterolateral margins sloping; anterior margin between rostrum and lateral projections weakly concave; posterior margin faintly emarginate medially; dorsal surface smooth. Rostrum prominent, triangular, terminating in spinule, overreaching lateral projections. Lateral projections prominent, each with small marginal spine.

Ocular peduncles ( Fig. 4A ) about 0.9 length of shield; corneas very slightly dilated, width about 0.2 of peduncular length. Ocular acicles triangular, terminating acutely; separated basally by 0.7 basal width of 1 acicle.

Antennular peduncles ( Fig. 4A ), when fully extended, overreaching distal corneal margins by about 0.2 length of ultimate peduncular segment. Ultimate segment with few setae on dorsal surface. Penultimate segment glabrous, much shorter than ultimate segment. Basal segment with prominent spine on dorsolateral margin of statocyst lobe.

Antennal peduncles ( Fig. 4A ), when fully extended, reaching distal corneal margins. Fifth and fourth segments with few setae. Third segment with spinule at ventromedial distal angle, few setae distally. Second segment with dorsolateral distal angle strongly produced, terminating in strong spine; dorsomesial distal angle with small spine. First segment unarmed. Antennal acicle not reaching base of cornea, or reaching midlength of fifth peduncular segment; terminating acutely, with row of tufts of long setae mesially. Antennal flagellum far overreaching tips of dactyls of outstretched ambulatory legs; most articles with several short and moderately long setae.

Maxillule with external lobe of endopod weakly developed, not recurved. Third maxilliped with carpus and merus unarmed. Ischium with crista dentata and 1 accessory tooth. Basis with 2 spinules on mesial margin.

Right cheliped ( Fig. 4B, C ) much stronger than left ( Fig. 4D, E ), propodal-carpal articulation slightly twisted. Chela non-operculiform. Dactyl slightly shorter than palm, longer than fixed finger, articulating slightly obliquely; dorsomesial margin with row of prominent, corneous-tipped spines and few long setae; dorsal surface slightly convex, row of corneous-tipped spines in proximal half adjacent to dorsomesial margin, remaining dorsal surface smooth; ventral surfaces with row of strong spines; cutting edge with strong calcareous tooth medially, corneous teeth distally, terminating in corneous claw. Palm shorter than carpus; dorsomesial margin with row of strong, corneous-tipped spines and few long setae; dorsal surface with rows of strong, sometimes corneous-tipped spines, stronger and denser near dorsolateral margin; dorsolateral margin delimited by row of strong, sometimes corneous-tipped spines and few long setae, extending onto fixed finger. Fixed finger with row of spines on dorsal surface adjacent to dorsomesial margin, otherwise mostly smooth; ventral surface with rows of smaller, sometimes corneous-tipped spines; cutting edge with 1 large calcareous teeth proximally, row of calcareous denticles distally, terminating in bifid corneous claw. Carpus slightly longer than merus, somewhat convex ventrally, distal width about twice of proximal width; dorsodistal margin with row of strong spines, dorsal surface slightly convex, with row of strong, sometimes corneous-tipped spines adjacent to dorsomesial margin, irregular rows of slightly smaller spines adjacent to dorsolateral margin; dorsomesial margin with row of strong spines; dorsolateral margin with row of small spines; lateral, mesial and ventral faces each with scattered tubercles. Merus triangular; dorsal, lateral and mesial faces weakly tuberculate; ventromesial and ventrolateral margins each with row of acute spines; ventral surface tuberculate. Ischium with 2 distal spinules on ventromesial margin.

Left cheliped ( Fig. 4D, E ) slender, propodal-carpal articulation twisted. Dactylus approximately as long as palm; dorsomesial margin with double row of strong spines and few long setae, dorsal surface smooth; cutting edges with row of corneous teeth, terminating in small corneous claw. Palm about half length of carpus; dorsomesial margin with row of strong corneous-tipped spines and few long setae, dorsal surface with rows of strong corneous-tipped spines and few long setae, dorsolateral margin delimited by row of strong spines extending onto fixed finger; ventral surface with scattered tubercles. Fixed finger with row of strong spines on dorsal surface not reaching to tip; cutting edge with row of small calcareous teeth terminating in small, bifid corneous claw. Carpus approximately as long as merus; dorsomesial margin with row of moderately strong spines and few long setae; dorsal surface with row of spines; lateral face slightly concave with scattered tubercle and few setae; mesial face with scattered tubercles. Dorsal margin of merus smooth, unarmed, dorsodistal margin unarmed; lateral and mesial surfaces with few tubercles, ventrolateral and ventromesial margins each with row of strong spines. Ischium with row of spinule on ventromesial margin.

Second and third pereopods ( Fig. 5A–D ) similar from right to left. Dactyli slightly twisted in dorsal view, about 1.5 length (second) or 1.6 length (third) of propodi; dorsal margins each with row of sparse long setae, lateral faces each with shallow longitudinal sulcus medially; mesial face with row of 9–10 (16–17 in paratypes) corneous spines dorsally, shallow longitudinal sulcus medially; ventral margins each with row of 10–12 (14–16 in paratypes) corneous spines. Propodi each with sparse row of long setae on dorsal margin; ventral margins each with 1–4 small spinules. Carpi each with small dorsodistal spine and tuft of long setae on dorsal margin, dorsal surfaces otherwise unarmed. Meri unarmed, with sparse setae on dorsal and ventral margins. Ischia unarmed. Fourth pereopods ( Fig. 5E ) semichelate, dactyli bearing row of minute denticles on ventral margin, lacking preungual process; propodal rasp consisting of 2 rows of scales. Fifth pereopods chelate.

Sternite of third pereopod (sixth thoracomere) ( Fig. 4F ) with anterior lobe subrectangular.

Pleon of male with 2 unpaired, unequally biramous pleopods (left third and fifth pleopods), fourth pleopod absent.

Telson ( Fig. 5F ) with shallow but distinct lateral indentations; posterior lobe divided by shallow median cleft, left lobe longer than right; terminal margins oblique, left lobe with 2–6 spinules, right lobe with 4–6 spinules.

Colouration in life. — Not known.

Etymology. — From the Latin similis (= similar), in reference to the superficial similarity to several members of the genus Pagurus .

Remarks. — Without examining the gill formula and the first pleopods in female specimens, this new species can be easily mistaken for species of the genus Pagurus Fabricius, 1775 because of the non-operculiform, spinose chelipeds.

This new species is referred to the P. teevana species group in having similar third pereopods, and most closely resembles P. bellula Osawa & Okuno, 2007 , P. furusei Asakura, 2000 , P. laevispinosa McLaughlin & Haig, 1989 , and P. vicina Komai & Osawa, 2004 in having non-operculiform, spinose or tuberculate chelae. Nevertheless, acute, corneous-tipped spines on the right chela, the absence of additional dorsal spines or spinules on the carpi of the second pereopods, and the possession of two rows of corneous scales in the propodal rasp of the fourth pereopod immediately distinguish P. similis , new species, from those four species. In those four species, the armature on the dorsal surface of the right palm consists of blunt tubercles ( P. bellula and P. vicina ) or subacute, non-corneous-tipped spines ( P. furusei and P. laevispinosa ); the carpi of the second pereopods bear one to three dorsal spines or spinules in addition to the dorsodistal spine; and the propodal rasp of the fourth pereopod consists only of a partial row of corneous scales. Furthermore, the absence of a longitudinal groove on the right chela adjacent to the dorsolateral margin differentiates the new species from P. bellula , P. laevispinosa , and P. vicina .

In having a spinose chela of the left cheliped, P. rahayuae is also comparable with the present new species and the four above mentioned species. However, P. rahayuae is immediately distinguished from the present new species in having blunt, various-sized tubercles on the right chela and the possession of a dorsal row of strong spines on the carpi of the second pereopods.

As only one male specimen is present, it is not clear if the lack of the fourth pleopod is normal or aberrant. Nevertheless, it is possible that the missing pleopod is a result of damage or poor preservation condition of the specimen.

Distribution. — So far known only from the Philippines; about 100 m deep.

Figures

Fig. 4. Pylopaguropsis similis, new species, holotype, male (sl 4.3 mm), PANGLAO 2004, Balicasag, NMCR. A, shield and cephalic appendages, dorsal view; B, right cheliped, dorsal view; C, right cheliped, mesial view; D, left cheliped dorsal view; E, left cheliped, mesial view; F, anterior lobe of sternite of third pereopod. Scale bars = 1 mm. Setae partially omitted.

Fig. 5. Pylopaguropsis similis, new species, holotype, fmale (sl 4.3 mm), PANGLAO 2004, Balicasag, NMCR. A, left second pereopod, lateral view; B, left second pereopod, mesial view; C, left third pereopod, lateral view; D, right third pereopod, mesial view; E, left fourth pereopod, lateral view; F, telson. Scale bars = 1 mm. Setae partially omitted.