Pylopaguropsis pygmaeus, 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 : 622-626

Pylopaguropsis pygmaeus , new species

( Figs. 1–3 )

Material examined. — Holotype: ovigerous female (1.5 mm) (NMCR-39095), PANGLAO 2004, Stn. T 36, West Pamilacan Island , Cervera shoal, 9°29.3'N, 123°51.5'E, sand on echinoderms bed, 95–128 m, 4 Jul.2004.

Paratypes: 1 male (1.1 mm), 1 ovigerous female (1.2 mm) ( MNHN) ; 1 male, (1.4 mm), 1 ovigerous female (1.5 mm) ( ZRC.2013.0866), same data as holotype; 1 ovigerous female (1.4 mm), Stn. L 42, Balicasag Island , 9°31.2'N, 123°40.7'E, 80–90 m, 2 Jul.2004 ( ZRC.2013.0867) .

Description. — Thirteen pairs of biserial gills.

Shield as long as broad ( Figs.1 , 2A ); anterolateral margins sloping; anterior margin between rostrum and lateral projections weakly concave; posterior margin slightly emarginate medially; dorsal surface smooth. Rostrum prominent, moderately broadly triangular, terminating in spinule, overreaching lateral projections. Lateral projections obtusely triangular, each with small marginal spine.

Ocular peduncles ( Fig. 2A ) stout, 0.9 length of shield, slightly inflated proximally, with row of sparse setae on dorsal surface; corneas not 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. 2A ), when fully extended, overreaching distal corneal margins by about half length of ultimate peduncular segment. Ultimate segment slightly widened in dorsal view, with 3 lateral setae on distal 0.2. Penultimate segment glabrous, much shorter than ultimate segment. Basal segment with prominent spine on dorsolateral margin of statocyst lobe.

Antennal peduncles ( Fig. 2A ), when fully extended, reaching distal corneal margins. Fifth and fourth segments with few scattered setae. Third segment with prominent spine at ventromedial distal angle and 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 barely reaching base of cornea or proximal third of fifth peduncular segment, slightly arcuate; terminating acutely, with row of individual or tufts of long setae. Antennal flagellum far overreaching tips of dactyls of outstretched ambulatory legs; most articles each with several short and moderately long setae.

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

Right cheliped ( Fig. 2B, C ) much stronger than left ( Fig. 2D, E ), operculiform. Chela about 1.4 times as long as broad measured at bases of fingers. Dactyl slightly longer than palm, much longer than fixed finger, articulating strongly obliquely; dorsomesial margin with row of large spines, slightly decreasing in size distally; dorsal surface slightly convex, row of spinules in proximal half adjacent to dorsomesial margin, remaining of dorsal surface with few scattered tubercles and tufts of sparse short setae; ventral surface with scattered tubercles and few tufts of short setae; cutting edge with 2 calcareous teeth in proximal half, and 1 subdistal tooth, terminating in small corneous claw. Palm as long as or slightly shorter than carpus; dorsomesial margin with row of small spines; dorsal surface slightly convex, irregular row of moderately large spines adjacent to dorsomesial margin, scattered small spinules and sparse setae on remaining surface; dorsolateral margin delimited by row of small spines, extending onto fixed finger, increasing in size distally. Fixed finger with scattered tiny tubercles and sparse setae on dorsal surface; ventral surface with scattered tubercles and few short setae; cutting edge with 1 large calcareous tooth proximally, 1 large calcareous tooth subdistally, row of calcareous denticles distally, terminating in tiny corneous claw. Carpus ( Fig. 2B, C ) slightly longer than merus, somewhat convex ventrally, distal width about 1.4 of proximal width; dorsodistal margin with row of large spines, dorsal surface slightly convex, with irregular rows of spinules and few setae; dorsomesial margin with row of moderately strong spines; dorsolateral margin with row of spines, smaller, blunt spines proximally; mesial face with sparse tubercles, ventromesial margin with row of spines; ventral surface with acute spines. Merus ( Fig. 2C ) triangular; dorsal surface with row of low tubercles or protuberances in distal half, dorsodistal margin unarmed; lateral surface with scattered small tubercles, ventrolateral margin with row of tubercles; mesial surface smooth, ventromesial margin with row of acute spines; ventral surface weakly tuberculate. Ischium unarmed.

Left cheliped ( Fig. 2D, E ) slender, propodal-carpal articulation twisted. Dactyl approximately as long as palm; dorsal surface with sparse setae, tiny spine proximally adjacent to dorsolateral margin; cutting edge with row of small calcareous teeth distally, terminating in small corneous claw. Palm about 0.7 length of carpus; dorsal surface with sparse tubercles and setae, dorsomesial margin with row of small spines. Fixed finger with sparse setae on dorsal surface; cutting edge with small calcareous teeth, terminating in small, bifid, corneous claw. Carpus about as long as merus; dorsomesial margin with row of strong spines and few setae; dorsal surface with irregular row of small spines and scattered setae, dorsodistal margin with moderately large spines; dorsolateral margin unarmed. Merus with low protuberances on dorsal surface, dorsodistal margin unarmed; lateral surface smooth, with few short setae, ventrolateral margin with row of moderately strong spines; mesial surface with few short setae, ventromesial margin with row of slightly smaller spines. Ischium unarmed.

Second and left third pereopods generally similar, right third pereopod slightly larger than left. Second pereopods ( Figs. 3A–D ) with dactyli about 1.4 length of propodi; dorsal margins each with row of long stiff setae, becoming bristle in right second pereopod, ventral margins each with 6 corneous spines, terminating in moderately large claw; mesial surfaces each with 2 corneous spines distally; shallow, narrow median sulcus on right pereopod. Propodi each with small corneous ventrodistal spine, dorsal margins each with sparse long setae. Carpi each with dorsodistal spine and 2 proximal spines, and sparse long setae. Meri each with 2 subdistal spines on ventral margin.

Left third pereopod ( Fig. 3E, F ) with dactyl 1.2 length of propodus, slightly twisted in dorsal view; dorsal margin with row of sparse long stiff setae, becoming bristle distally; ventral margin with row of 6 corneous spines, terminating in large corneous claw; lateral face with row of setae on midline, mesial face with median row of corneous spines and setae. Propodus with 1 corneous spine on ventrodistal margin, dorsal and ventral margins each with row of sparse long setae. Carpus with small dorsodistal spine and few setae on dorsal margin. Merus unarmed, with sparse setae on dorsal and ventral margins.

Right third pereopod ( Fig. 3G, H ) with dactyl about 1.5 length of propodus, slightly twisted in dorsal view; dorsal margin with row of long setae, becoming bristles distally; lateral face with wide, shallow longitudinal sulcus; mesial face with median row of corneous spines in distal half; ventral margin with row of 7 corneous spines. Propodus with row of long setae on dorsal margin; ventrodistal margin with 2 strong and 1 weak corneous spines; lateral face concave with low, narrow longitudinal ridge on midline; mesial face with median row of setae. Carpus with 2 small dorsodistal spines and sparse long setae on dorsal margin. Merus unarmed, with sparse setae on dorsal and ventral margins. Ischium unarmed.

Fourth pereopods ( Fig. 2F ) semichelate, lacking preungual process on dactyl. Dactyl with row of minute denticles on ventral margin. Propodal rasp consisting of 1 row of scales. Fifth pereopods chelate.

Sternite of third pereopod (sixth thoracomere) with anterior lobe subrectangular ( Fig. 2H ).

Telson ( Fig. 2G ) with very shallow lateral indentations; posterior lobe divided by shallow median cleft, left lobe slightly longer than right; terminal margins oblique, each with 4 prominent spines and few long setae.

Colouration in life. — (See Fig. 1 ). Shield cream or whitish, with several red spots on rostrum and dorsal surface; ocular peduncle, with longitudinal red stripes mesially and laterally on cream background, dorsal surface with slightly wider reddish orange longitudinal stripe. Antennular peduncle pinkish. Right cheliped generally cream with few red dots on dactyl and fixed finger proximally, and on outer surface of palm. Left cheliped also generally cream with longitudinal red stripes on dorsal surface of fixed finger and dorsodistal margin of palm extending onto carpus and merus. Second and third pereopods generally cream, with red longitudinal stripes, continuing or interrupted, on dorsal, lateral and mesial faces of dactyli to meri.

Etymology. — From the Latin pygmaeus , (= small, little), alluding to the small size of the individuals of this species. Used as a noun in apposition.

Remarks. — Pylopaguropsis pygmaeus , new species, is assigned to the P. magnimanus ( Henderson, 1896) species group (cf. McLaughlin & Haig, 1989) based on the appreciably dissimilar third pereopods with the right propodus and dactyl being appreciably broader than the left and sculptured on the lateral faces. Morphologically, it appears close to P. keijii McLaughlin & Haig, 1989 , P. lemaitrei Asakura & Pauly, 2003 , P. lewinsoni McLaughlin & Haig, 1989 and P. zebra ( Henderson, 1893) . Pylopaguropsis pygmaeus , new species, differs from the latter four species in the non-dilated cornea and the different armature of the left chela. In P. keijii , P. lemaitrei , P. lewinsohni and P. zebra , the cornea is slightly dilated. The left chela is armed with a dorsomesial row of tiny spines in P. pygmaeus ; it is devoid of armature in P. keijii , P. lemaitrei , and P. zebra ; in P. lewinsohni , there are a few minute spinulose tubercles on the dorsal surface of the palm. The appreciably basally inflated ocular peduncles immediately distinguish P. keijii and P. lemaitrei from the new species, as well as P. lewinsohni and P. zebra . The sculpture of the lateral surface of the propodus of the right third pereopod is most pronounced in P. lewinsohni and P. lemaitrei and has three longitudinal sulci. In P. pygmaeus , new species, P. keijii , and P. zebra , there is only one longitudinal sulcus or concavity on the lateral surface of the propodus of the right third pereopod. The carpus of the left cheliped is armed at least with a dorsomesial row of spines in P. lewinsohni , P. pygmaeus , new species, and P. zebra , whereas it bears only a dorsodistal spine in P. keijii and P. lemaitrei . The dactyli of the ambulatory legs bear fewer ventral spines in P. pygmaeus than in the other four species (six or seven versus seven to 12). The terminal margins of the telson are oblique and armed with three or four prominent spines in P. pygmaeus , new species, whereas they are nearly horizontal or slightly oblique in P. lewinsohni and P. zebra , and similarly oblique, but having more numerous spines (five or more) on the left margin in P. keijii and P. lemaitrei . Furthermore, P. pygmaeus is one of the smallest species in the genus. The largest specimen examined, an ovigerous female, measures 1.5 mm in shield length. The other four species mentioned herein attain at least 3.0 mm in shield length.

Although the presence of a preungual process on the dactyl of the fourth pereopod has been described in many species of Pylopaguropsis (McLaughlin & Haig, 1989; Asakura, 2000), we confirmed that the preungual process is absent in P. pygmaeus , new species. In P. keijii and P. zebra the fourth pereopod has a preungual process (McLaughlin & Haig, 1989). Although Asakura (2000) stated that there was a small preungual process in P. keijii , but his figure does not show the presence of such a process ( Asakura, 2000: Fig. 7J). In describing P. lemaitrei Asakura & Pauly (2003) stated that there was no preungual process on its fourth pereopod. However, considering the close resemblance between P. keijii and P. lemaitrei , it is advisable to reexamine if the preungual process is really absent in P. lemaitrei .

The colour in life is also quite different among the five species. In P. pygmaeus , the ocular peduncles are cream with red longitudinal stripes; the left cheliped and ambulatory legs are whitish cream with red longitudinal stripes. In P. keijii , the ocular peduncles are light purple with dark purple longitudinal stripes on the dorsal surfaces; the chelipeds and ambulatory legs are deep magenta ( Asakura, 2000). In P. lemaitrei , the ocular peduncles are purple or magenta, without distinct longitudinal stripes; the left chelipeds and ambulatory legs are purple or deep magenta, being devoid of longitudinal stripes ( Asakura, 2003). In P. lewinsohni , the ocular peduncles are purple, without distinct longitudinal stripes; the left chelipeds and ambulatory legs have reddish purple and thin white longitudinal stripes (Okuno &Arima, 2004; Okuno et al., 2006). In P. zebra , the ocular peduncles are purplish, without longitudinal stripes; the carpi and meri of the chelipeds and ambulatory legs have red and white longitudinal stripes ( McLaughlin et al., 2007).

Distribution. — Pamilacan and Balicasag Islands, Bohol, the Philippines; 80– 128 m.

Figures

Fig.1. Pylopaguropsis pygmaeus, new species, paratypes.A, female (sl 1.2 mm), PANGLAO 2004, stn T 36, MNHN; B, female (sl 1.5 mm), PANGLAO 2004, stn T 36, ZRC 2013.0866.

Fig. 2. Pylopaguropsis pygmaeus, new species, holotype, female (sl 1.5 mm), PANGLAO 2004, stn T 36, NMCR. A, shield and cephalic appendages, dorsal view; B, right cheliped, dorsal view; C, right cheliped, mesial view; D, left cheliped lateral view; E, left cheliped dorsal view; F, left fourth pereopod, lateral view; G, telson, dorsal view; H, anterior lobe of sternite of third pereopod. Scale bars = 1 mm (A–C), 0.5 mm (D–H). Setae partially omitted.

Fig. 3. Pylopaguropsis pygmaeus, new species, holotype, female (sl 1.5 mm), PANGLAO 2004, stn T39, NMCR. A, left second pereopod, mesial view; B, left second pereopod, lateral view; C, right second pereopod, lateral view; D, right second pereopod, mesial view; E, left third pereopod, mesial view; F, left third pereopod, lateral view; G, right third pereopod, lateral view; H, right third pereopod, mesial view. Scale bars = 1 mm. Setae partially omitted.