Lophopagurus (Lophopagurus) minimus Komai & Rahayu, 2013, n. sp.
Creators: name: Komai, Tomoyuki
name: Rahayu, Dwi Listyo
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Paguridae
Lophopagurus
Lophopagurus minimus

description: Lophopagurus (Lophopagurus) minimus n. sp.
(Figs. 1–3)
Material examined. Holotype: ovigerous female (sl 1.3 mm), off Motu, Maeherehonae, Rangiroa Atoll, Tuamoto Archipelago, Frenth Polynesia, 14°09.29’S, 147°08.59’W, 6–12 m, outer reef slope, under rocks, 10 November 2001, coll. Gustav Paulay, FMNH 1858.
Paratype: 1 ovigerous female (sl 1.2 mm), same data as holotype, FMNH 1813.
Description. Shield (Fig. 1 A) approximately as long as wide; anterior margin between rostrum and lateral projections slightly concave; lateral margins strongly convex; dorsal surface with few tufts of short setae laterally; paragastric grooves delimited only posteriorly. Rostrum broadly triangular, extending beyond lateral projections, terminating in small spine. Lateral projections obsolete, each with 1 submarginal spinule.
Ocular peduncles (Fig. 1 A) about 0.7 times as long as shield, moderately stout, faintly constricted proximal to base of corneas, somewhat inflated basally, each with longitudinal row of tufts of short setae on dorsal surface in distal half; cornea slightly dilated; basal width distinctly greater than corneal width. Ocular acicles narrowly subtriangular, with submarginal spinule distally; moderately separated basally. Interocular lobe visible in dorsal view.
Antennular peduncles (Fig. 1 A) overreaching distal corneal margins by about 0.3 length of ultimate segments. Ultimate segment with prominent tuft of long setae on dorsolateral distal angle, dorsal surface almost glabrous. Basal segment with moderately inflated statocyst lobe bearing prominent spine laterally; ventrodistal angle slightly produced.
Antennal peduncles (Fig. 1 A) slightly falling short of distal corneal margins. Fifth and fourth segments with few stiff setae on lateral and mesial margins. Third segment with tiny spine at ventromesial distal angle. Second segment with dorsolateral distal angle produced to strong spine reaching midlength of fourth segment; mesial margin with 1 additional spinule subterminally; dorsomesial distal angle with small spine. First segment unarmed on lateral surface; ventrodistal margin strongly produced. Antennal acicle reaching corneal base, terminating in tiny spine, with row of moderately long setae dorsomesially. Antennal flagellum about 4 times as long as shield, overreaching extended right cheliped; each article with 1–3 short setae and 1 long seta every 2 articles.
Third maxilliped (Fig. 1 B) moderately stout. Ischium (Fig. 1 C) 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.
Chelipeds appreciably unequal and dissimilar. Right cheliped (Figs. 1 D, E; 2A, B) with chela subovate in dorsal view, with mesial margin of palm nearly straight and lateral margin arcuate. Dactylus subequal in length to palm, slightly curved ventrally; dorsal surface convex transversely, smooth, without median ridge; dorsomesial or mesial margin not delimited, mesial face with some tiny tubercles along midline proximally; surfaces with scattered moderately short setae; cutting edge with row of obtuse calcareous teeth, terminating in small calcareous claw. Palm slightly shorter than carpus; dorsal surface gently convex, with sparse granules and scattered short to long setae; dorsolateral margin sharply delimited by tuberculate carina extending onto fixed finger; dorsomesial margin delimited by double row of low, rounded tubercles; lateral surface smooth, with scattered short setae; mesial surface also smooth, with few long setae; ventral surface convex, with few long setae. Fixed finger broader than dactylus; cutting edge with 2 blunt calcareous teeth in proximal 0.4, smooth in distal 0.6, terminating in calcareous claw. Carpus longer than merus, distinctly widened distally; dorsomesial margin with row of 4 moderately strong spines increasing in size distally and tufts of long setae; dorsal surface smooth, with few long setae; dorsolateral margin not clearly delimited, with 1 or 2 small tubercles and tufts of long setae; mesial surface with 2 short transverse ridges bearing row of long setae in proximal half and 1 small submarginal spine adjacent to distal angle, and also with scattered long setae; lateral surface smooth, with several short to long setae dorsally; ventral surface with anterior half forming concavity to accommodate carpus when cheliped flexed, and posterior half convex, with several long setae. Merus unarmed on dorsodistal margin; dorsal surface also unarmed, glabrous; lateral surface smooth, with some long setae proximoventrally, ventrolateral margin with 2 spines distally; mesial surface smooth, glabrous, ventromesial margin unarmed, with row of numerous long setae; ventral surface slightly concave transversely, with several long setae. Ischium unarmed.
Left cheliped (Figs. 1 F; 2C, D) with chela elongate subovate in general outline. Dactylus 1.9 times as long as palm, surfaces unarmed, bearing scattered tufts of short to long setae; cutting edge with row of closely set corneous teeth, terminating in small corneous claw. Palm short, about half length of carpus, triangular in cross-section; prominently elevated dorsal midline with row of small spines or tubercles extending onto midlength of fixed finger; lateral margin delimited by row of blunt small tubercles, extending onto midlength of fixed finger; dorsomesial margin not delimited; mesial surface smooth, with scattered long setae; ventral surface slightly convex, with scattered long setae. Cutting edge of fixed finger with row of corneous teeth and few tiny, sharp calcareous teeth in distal half. Carpus slightly widened distally, subequal in length to merus; dorsolateral margin with row of 3 prominent spines in distal half, dorsomesial margin with row of 2 spines in distal 0.3, both margins with tufts of long stiff setae; dorsodistal margin with 1 additional minute spine laterally; lateral surface with few tufts of long setae dorsally, otherwise glabrous, ventrolateral margin denticulate; mesial surface smooth, with long setae in distal half and 2 short transverse ridges bearing setae in posterior half dorsally, ventromesial margin strongly convex, unarmed; anterior half of ventral surface forming concavity, posterior half with several long setae. Merus unarmed on dorsodistal margin; dorsal surface almost glabrous; lateral surface glabrous, nearly straight with row of 3 prominent spines and 1 or 2 low protuberances; mesial surface also smooth, with few setae ventrally, ventromesial margin with 2 small spines proximally; ventral surface with several long setae. Ischium unarmed, with short to long setae dorsally and ventrally.
Ambulatory legs (Fig. 3 A–D) generally similar from right to left, moderately slender. Dactyli slightly curved ventrally in lateral view, nearly straight in dorsal view, about 1.1 times as long as propodi, 6.5–7.0 times as long as wide; dorsal margins each with sparse row of tufts of moderately short setae; lateral and mesial surfaces without sulcus or groove, mesial surfaces unarmed (second) (Fig. 3 B) or 2 minute spinules adjacent to dorsal margin (third) (Fig. 3 D); ventral margins each with row of 6 or 7 slender corneous spines. Propodi with row of tufts of long setae on dorsal margin, 4.3–4.5 times as long as wide; lateral and mesial faces with few short setae (second) or glabrous (third); ventral margins with row of moderately long setae (second) or with very short setae (third); ventrodistal margins each with pair of corneous spines. Carpi each with small dorsodistal spine (second) or unarmed (third); dorsal margins each with row of tufts of long setae; ventral surfaces with few setae. Meri each with row of moderately long setae on dorsal margins; lateral and mesial faces smooth; ventral margins each with tufts of long setae (setae longer in second than in third), second with ventrolateral distal spine and 1 ventral spine located at distal one-third, third unarmed. Female with unpaired left gonopore (Fig. 1 H).
Fourth pereopods (Fig. 1 G) semichelate. Dactyli each with row of relatively long corneous teeth on ventral margins; no preungual process. Propodi with rasp consisting of single row of corneous scales.
Sixth thoracic sternite (Fig. 1 H) with anterior lobe subrectangular, slightly skewed to left; sparse short setae on anterior margin. Eighth thoracic sternite (Fig. 1 E) with two narrowly spaced rounded lobes (concealed by first pleopods), with few short setae.
Pleon dextrally twisted. Female with paired first pleopods modified as gonopods (Fig. 1 I), protopod and ramus distinctly articulated; unpaired, left second to fifth pleopods present, second and third subequally biramous, fourth and fifth not reduced in size, uniramous. Uropods strongly asymmetrical. Telson (Fig. 1 J) with shallow lateral indentations; terminal margins slightly oblique, each with 3 or 4 spinules; posterolateral margins forming thin chitinous plates.
Coloration in life. Not Known.
Distribution. Known only from the type locality, Tuamotu Archipelago, 6–12 m deep.
Remarks. Although no male specimens are available for study, the present new species is assigned to the genus Lophopagurus with little hesitation because of the possession of 11 pairs of biserial gills, the occurrence of paired first pleopods in females and the similarities in the general structure of both chelipeds. Lophopagurus (Lophopagurus) minimus n. sp. appears closest to L. (L.) nanus known from southeastern Australia and Tasmania in carpi of second pereopods bearing only a dorsodistal spine and the flat lateral surface of the dactylus of the left third pereopod. However, the new species is easily distinguished from the latter species by many morphological characters (cf. McLaughlin & Gunn 1994). The ocular peduncles are basally inflated in L. minimus n. sp., but such inflation is not seen in the ocular peduncles of L. nanus. The dactylus of the right cheliped is unarmed on the dorsal surface in L. minimus n. sp., whereas there is a single or double row of tubercles or protuberances along the midline in L. nanus; the dorsomesial margin is not delimited in L. minimus n. sp., rather than sharply delimited by row of small tubercles in L. nanus. The dorsal surface of the right palm bears only sparse, minute tubercles in L. minimus n. sp., whereas it is armed with a longitudinal row of small tubercles laterad to the midline as well as scattered minute tubercles in L. nanus. The carpus of the right cheliped has only one dorsomesial row of spines in L. minimus n. sp., rather than two dorsomesial rows of spines in L. nanus. The propodi of the ambulatory legs are each armed only with a pair of corneous spines on the distoventral margin in L. minimus, but there is a row of minute corneous spines on ventral margins of each propodus, in addition to two or three spines on the distoventral margin, in L. nanus.
Lophopagurus minimus n. sp. is the smallest representative of the genus, measuring only 1.2–1.3 mm in the shield length in ovigerous females. De Saint Laurent & McLaughlin (2000) ranked L. (L.) pumilus as the smallest species (measuring 1.4–3.9 mm in the shield length in ovigerous females) in the genus known at the time. This new species also represents the first representative of the subgenus Lophopagurus occurring in tropical waters. Other seven known species in the subgenus are distributed in New Zealand (L. crenatus, L. foresti, L. nodulosus, L. lacertosus, L. pumilus and L. thompsoni) or southeastern Australia and Tasmania (L. nanus).
Etymology. The specific name from the Latin minimus, meaning smallest, reflecting the small size of this species.
description: Published as part of 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, pp. 240-252 in Zootaxa 3691 (2) on pages 241-246, DOI: 10.11646/zootaxa.3691.2.4, http://zenodo.org/record/222829