Lophopagurus (Australeremus) indonesiensis McLaughlin, 1997

Komai, Tomoyuki & Rahayu, Dwi Listyo, 2013, A new species of the pagurid hermit crab genus Lophopagurus McLaughlin, 1981 (Crustacea: Decapoda: Anomura) from French Polynesia, and additional record of L. indonesiensis McLaughlin, 1997 from the Philippines, Zootaxa 3691 (2), pp. 240-252 : 246-251

Lophopagurus (Australeremus) indonesiensis McLaughlin, 1997

( Figs. 4–6 )

Australeremus indonesiensis McLaughlin, 1997: 523 , figs. 24b, d–f, h, 42a–b [type locality: Kai Islands, Indonesia, 205–212 m]; Komai 1999: 27.

Lophopagurus (Australeremus) indonesiensis . — McLaughlin et al. 2010: 30 (list), 47.

Material examined. Non-type: PANGLAO 2004, stn T2, Bolod, Panglao Island, Bohol Sea, the Philippines, 09°32.4'N, 123°47.8'E, 152 m, coarse sand, 31 May 2004, 1 female (sl 1.8 mm), ZRC 2013.0723.

Comparative material. Lophopagurus (Australeremus) triserratus . RV “Tansei-maru“, KT07-31 cruise, stn L-3-200, W of Izu-ohshima Island, Izu Islands, 34°34.03’N, 139°18.36’E, 152–198 m, 27 November 2007, chain bag dredge, coll. T. Komai, 10 males (sl 1.8–2.8 mm), 7 females (sl 1.7–2.2 mm), CBM-ZC 10386.

Description of specimen from Philippines. Shield ( Fig. 4 A) about 1.3 times as long as wide; anterior margin between rostrum and lateral projections concave; posterior margin truncate; dorsal surface with longitudinal rows of tufts of short setae posterior to lateral projections; paragastric grooves defined only posteriorly. Rostrum triangular, terminating acutely. Lateral projections obtusely triangular, each with minute submarginal spine.

Ocular peduncles ( Fig. 4 A) about 0.7 times as long as shield, moderately slender, slightly inflated basally; corneas faintly dilated. Ocular acicles subtriangular, terminating subacutely, with small submarginal spine; moderately separated basally. Interocular lobe moderately developed, partially concealed by rostrum.

Antennular peduncles ( Fig. 4 A) overreaching distal corneal margins by about 0.4 length of ultimate segment. Ultimate segment with 1 long seta on dorsolateral distal angle and few much shorter setae on dorsal surface. Basal segment with moderately inflated statocyst lobe bearing prominent spine laterally.

Antennal peduncles ( Fig. 4 A) overreaching distal corneal margins by about half length of fifth segment. Fifth and fourth segments with few short setae. Third segment with unarmed ventrodistal angle. Second segment with dorsolateral distal angle produced, terminating in simple acute spine slightly falling short of midlength of fourth segment, mesial margin devoid of accessory spinules; dorsomesial distal angle with tiny spine. First segment with minute laterodistal spine; ventrodistal margin with 1 prominent projection and 1 minute spine. Antennal acicle reaching proximal 0.2 of fifth segment or slightly overreaching corneal base, terminating in small spine obscured by tuft of long setae; mesial margin with tufts of moderately short setae. Antennal flagellum overreaching right cheliped; each article with 1–3 long (2–6 article length) and 1–4 much shorter setae.

Third maxilliped relatively slender. Ischium bearing well-developed crista dentata consisting of row of corneous teeth increasing in size proximally and 1 accessory tooth. Merus and carpus unarmed. Exopod reaching midlength of carpus.

Right cheliped ( Figs. 4 B; 5A, B) with dactylus slightly shorter than palm; dorsal surface with row of few minute tubercles on dorsal midline; dorsomesial margin with row of small spines or tubercles decreasing in size distally; cutting edge with row of bluntly triangular calcareous teeth, terminating in small corneous claw. Palm subrectangular in general outline, slightly widened distally, about 0.8 times as long as carpus; dorsomesial, dorsolateral and dorsoproximal margins each with blunt or spine-like tubercles entirely circumscribing palm and fixed finger, dorsal surface of palm slightly convex, with scattered small tubercles. Fixed finger with strongly arcuate dorsolateral margin; cutting edge with row of bluntly triangular calcareous teeth, terminating in small corneous claw. Carpus slightly longer than merus; dorsomesial margin with row of small spines (including one at dorsomesial distal angle) and tufts or single, short to long stiff setae, dorsolateral margin also with row of small spines and tufts of stiff setae; mesial surface with tufts of stiff setae dorsally, ventromesial margin unarmed; lateral surface with few stiff setae dorsally, ventrolateral margin unarmed; ventral surface gently convex, with scattered short to long setae. Merus with 1 dorsodistal spine; dorsal surface with row of short to long setae; mesial and lateral surfaces almost glabrous, ventromesial margin with 1 small spine far proximal to distal angle, ventrolateral margin unarmed; ventral surface with scattered short to long setae. Ischium unarmed.

Left cheliped ( Figs. 4 C, D; 5C, D) with propodal-carpal articulation about 40° clockwise from horizontal plane, generally compressed laterally. Chela flattened, with broadly arcuate lateral margin. Dactylus straight, about 1.3 times as long as palm; surfaces unarmed, with sparse tufts of short to long setae; cutting edge with row of small corneous teeth in distal half, terminating in small corneous claw. Palm about half length of carpus; dorsolateral margin of palm and fixed finger carinae, armed with row of small spines; dorsal surface generally flattened, armed with some minute, indistinct tubercles lateral to midline; dorsomesial margin not delimited; ventral surface slightly convex; all surfaces with sparse short to long setae. Fixed finger about 2 times wider than dactylus; cutting edge with row of minute calcareous teeth, terminating in small corneous claw. Carpus acutely triangular in cross section, subequal in length to carpus; dorsal margin with row of strong spines and tufts of stiff moderately short setae, distal margin without conspicuous spines; mesial surface with scattered tufts of long stiff setae, with 1 tubercles near ventrodistal angle; lateral surface with scattered very short setae; ventral surface with scattered long setae. Merus unarmed on distal margin; dorsal surface with row of tufts of short setae laterally; mesial surface with few tufts of short setae dorsally, ventromesial margin with 1 small spine far proximal to distal angle and row of long setae; lateral surface glabrous, ventrolateral margin unarmed; ventral surface scattered long setae. Ischium unarmed, with setae dorsally and ventrally.

Ambulatory legs ( Fig. 6A–D ) generally similar from right to left, relatively slender. Dactyli slightly curved ventrally in lateral view, nearly straight in dorsal view, 1.1–1.2 times as long as propodi and 9.0–10.0 times longer than wide; dorsal margins each with tufts (second) or single (third) long setae; mesial faces each 1 subterminal corneous spinule near dorsal margin (second; Fig. 6B ) or with row of 4 widely spaced corneous spinules near dorsal margin (third; Fig. 6D ); ventral margins each with 7–9 slender corneous spines. Propodi about 5.6 times longer than wide; dorsal and ventral surfaces with row of short to long setae, ventral surface unarmed except for 1 small corneous spine on distal margin. Carpi each with minute dorsodistal spine (second) or unarmed on dorsal surface; dorsal and ventral surfaces each with sparse long setae. Meri each with row of setae on dorsal and ventral surfaces (ventral setae much longer than dorsal setae), ventral surfaces spineless. Ischia unarmed, with setae on dorsal and ventral margins. Female with paired gonopores.

Fourth pereopods semichelate. Dactyli each with row of minute corneous teeth on ventral margins; no preungual process. Propodi with rasp consisting of single row of corneous scales.

Sixth thoracic sternite ( Fig. 4 E) with anterior lobe small, narrowly subsemiovate, bearing long anterior setae. Eighth thoracic sternite with two narrowly separated rounded lobes, with few short setae (concealed by first pleopods).

Pleon slightly flexed, more than twice length of carapace. Female with paired first pleopods modified as gonopods ( Fig. 4 F), protopod and ramus apparently fused; unpaired, left second to fifth pleopods present, second and third subequally biramous, fourth and fifth not reduced in size, uniramous. Uropods symmetrical. Telson ( Fig. 4 G) with shallow lateral indentations; posterior lobes with shallow median cleft, terminal margins slightly oblique, armed with 3 (left) or 5 (right) small spines; posterolateral margins rounded, not forming chitinous plates.

Distribution. Previously known only from the Banda Sea, Indonesia, 205– 289 m. The present specimen represents the first record of this species from outside Indonesia.

Remarks. McLaughlin (1997) indicated close similarities between her new taxon Lophopagurus indonesiensis and L. triserratus (as Australeremus triserratus ), and differentiated these two taxa using only the dorsal armature of the right chela, i.e., a median row of large spines is absent in L. indonesiensis versus present in L. triserratus . Komai (1999) demonstrated that the armature of the right chela is considerably variable in L. triserratus (as Australeremus triserratus ), in particular, the dorsal spines or tubercles are sometimes almost absent according to individuals. Therefore, Komai (1999) questioned the validity of L. indonesiensis . During this study, we have compared the present specimen with 17 topotypic specimens of L. triserratus from the Sagami Sea, Japan, and noticed that the ambulatory legs are constantly slenderer in the Philippine specimen than in the Japanese specimens, as illustrated ( Fig. 6A versus 6E). For example, the length/width ratio of dactyli and propodi of the second pereopods are about 9.0 times and 5.6 times as long as wide, respectively, in the Philippine specimen, whereas 6.5–7.0 times and 4.0–4.5 times in the Japanese specimens. The original figure of McLaughlin (1997: fig. 24e) clearly depicts similarly slender right second pereopod of L. indonesiensis . The weak armature on the right chela, particularly the absence of a distinctly delimited median row of spines or tubercles, also agrees with the type description of L. indonesiensis . Therefore, we came to a conclusion that L. (Australeremus) indonesiensis is a valid taxon, distinct from L. (A.) triserratus .

The present specimen differs from the type description by McLaughlin (1997) in the less pronounced armature of the right cheliped and the more clearly indicated lateral indentations of the telson, but these traits are substantially variable intraspecifically in species of Lophopagurus (McLaughlin & Gunn 1994; Komai 1999; de Saint Laurent & McLaughlin 2000), and consequently, do not provide diagnostic significance.

Figures

FIGURE 4. Lophopagurus (Australeremus) indonesiensis (McLaughlin, 1997), female (sl 1.8 mm), ZRC 2013.0723. A, shield and cephalic appendages, dorsal view; B, chela and carpus of right cheliped, dorsal view; C, chela of left cheliped, dorsomesial view (perpendicular to horizontal plane of surface); D, carpus of left cheliped, dorsal view; E, sixth thoracic sternite, ventral view; F, paired first pleopods, ventral view; G, telson, dorsal view. Scale bars: 0.5 mm.

FIGURE 5. Lophopagurus (Australeremus) indonesiensis (McLaughlin, 1997), female (sl 1.8 mm), ZRC 2013.0723. A, right cheliped, mesial view; B, same, lateral view; C, left cheliped, mesial view; D, same, lateral view. Scale bar: 0.5 mm.

FIGURE 6. A – D, Lophopagurus (Australeremus) indonesiensis (McLaughlin, 1997), female (sl 1.8 mm), ZRC 2013.0723; E, Lophopagurus (Australeremus) triserratus (Ortmann, 1892), female (sl 1.7 mm), CBM-ZC 10386. A, E, right second pereopod, lateral view; B, dactylus of right second pereopod, mesial view; C, left third pereopod, lateral view; D, same, dactylus, mesial view. Scale bar: 0.5 mm.