Karstarma vulcan Poupin & Crestey & Guelte 2018
- Cave-dwelling crabs of the genus Karstarma from lava tubes of the volcano ‘ Piton de la Fournaise’, in Réunion Island, with description of a new species and redescription of Karstarma jacksoni (Balss, 1934) from Christmas Island (Decapoda, Brachyura, Sesarmidae)
- Karstarma vulcan
Diagnosis. Carapace (Fig. 1 A – C) approximately trapezoidal, maximum width across base of second and third ambulatory legs, width 1.2 times length; dorsal surface gently convex, slightly uneven, minutely pitted, not setose with only scattered short setae more abundant on posterolateral regions, regions poorly marked except for epigastric and urogastric grooves, posterolateral regions with a few faint oblique striae. Lateral margins of carapace sub-parallel, diverging weakly posteriorly. Anterolateral margin with 2 main teeth including external orbital angle (Fig. 9 A, B); first tooth (external orbital angle) blunt, directed inwards at angle of ~ 40 °; second tooth with blunt tip separated from former tooth by shallow cleft; third tooth poorly marked, separated from second tooth by minute notch, or absent, tip of second tooth placed closer to tip of first tooth than third. FIGURE 1. Karstarma vulcan sp. nov., holotype, male, 16.2 × 18.9 mm (MNHN-IU- 2013 - 7243). A) dorsal habitus; B – D) carapace and chelae, dorsal, ventral, frontal views respectively; E) buccal cavern, third maxilliped and pterygostomian area (scale bars 10 mm). Front (Fig. 1 D) deflected at almost 90 °, 0.4 times fronto-orbital width (measured between tip of anterolateral teeth), 2.2 – 2.4 wider than high, frontal margin minutely granulated, slightly sinuous with a large median V-shaped notch, postfrontal cristae composed of two large protuberances placed transversely between base of ocular peduncles on each side of epigastric groove. Supraorbital margin widely U-shaped, eyes well developed, cornea pigmented as wide as ocular peduncle; infraorbital margin composed of strong ridge with transverse granulation ventrally and line of short curved setae dorsally. Epistome obtusely triangular on upper side, lower side with 1 median, 2 lateral triangular projections. Branchiostegite (Fig. 1 D, E) covered with reticulate uniform network of short setae. Third maxilliped ischium (Fig. 1 E) slightly longer than merus, median groove with row of setae, merus with oblique crest adjacent to inner margin, exopod with flagellum as long as width of merus. Chelipeds of male (Figs. 1 A – D, 2 A, B, E) symmetrical; merus triangular in cross-section, all margins denticulated, inner face (Fig. 2 E) with longitudinal row of pubescence, inner ventral margin with about 10 denticles on proximal ¾ and a denticulated flange on distal ¼, outer face with transverse striae furnished with short setae; carpus rounded, unarmed, dorsal face with short setiferous striae; chela much higher than in female, 2 times as long as high, inner and outer faces of palm inflated, coarsely granulated, larger granules of inner face disposed on a salient transverse ridge that rubs against the infraorbital margin (‘ stridulating’ mechanism; see remarks under K. jacksoni), upper and lower margins rounded, unarmed, cutting edges of fingers not gaping when fingers closed, with 8 – 12 large sub-triangular teeth of unequal sizes all along margin; tip of fingers corneous, hoof-like; movable finger 1.2 as long as palm, dorsal margin with granules. Chelipeds of female symmetrical; inner ventral margin of merus minutely denticulated, without distal flange (Fig. 2 F); chela (Fig. 2 C, D) much elongated than in male, 2.8 – 3.0 as long as high, inner and outer face of palm moderately inflated sparsely pitted, upper and lower margins rounded, unarmed, cutting edges of fingers not gaping when fingers closed, with minute sub-equal triangular teeth on proximal ¾, unarmed on distal ¼, tip of fingers corneous, hoof-like, incurved, movable finger 1.4 as long as palm. Ambulatory legs 1 – 4 (P 2 – P 5) (Fig. 2 G – M) long, third leg longest 3.1 – 3.4 and 2.6 – 2.8 as long as CL and CW, respectively, tufts of setae present between coxae of ambulatory legs 1, 2 and 2, 3 (Fig. 1 C); outer faces of meri with short striae (reduced in females), with median rounded carina in distal half separating dorsal and ventral sulci (more pronounced in leg 3), upper and lower margins carinated, unarmed, length to width ratios of meri of legs 2, 3, 3.8 – 4.1, 3.9 – 4.6, respectively; carpi 0.4 – 0.6 meri length, unarmed, outer faces with 2 longitudinal carinae, lower one finely granulated; propodi 0.6 – 0.7 meri length, unarmed, furnished with longitudinal rows of long stiff setae on upper and lower margins and on inner / outer faces (1 or 2 rows on each face), outer faces flat and smooth, mat of setae (Fig. 1 K, L) present on distal lower margin of legs 1, 2 in males only; dactyli sub-cylindrical, unarmed, as long or slightly longer (1.1) than propodi, gently curved in distal third, with similar longitudinal rows of setae than on propodi, terminating in corneous claws. Male pleon (Fig. 1 C), sub-triangular, telson rounded at tip, as high as wide; 6 th somite the highest, trapezoidal, anterior margin sinuous lateral margins convex; somites 3 – 5 elongated, somite 5 3.5 as long as high, somites 1 – 3 the longest, somite 3 not reaching base of P 5 coxae. G 1 (Fig. 10 A, C), stout, distal part directed outward at an angle of about 90 °, terminating in chitinous tip. G 2 (Fig. 10 B) approximately half as long as G 1, barely curved, with Ushaped corneous extremity. Female pleon rounded, about 1.5 – 1.6 as wide as long, lateral margins markedly convex, maximum width between somites 4, 5, telson sub-triangular, rounded at tip, somite 6 the highest, somites 4, 5 largest of similar height. Vulva (Fig. 10 G) on sternite 6, with broad sternal rim covered with folded central operculum. Size. From 13.0 × 16.5 mm to 16.2 × 18.9 mm.
Etymology. This new species is named after ‘ Vulcan’ (used as an appositive noun) the ancient Roman god of fire, including fire of volcanoes, in allusion to the crab’s being discovered in the lava tubes of the volcano ‘ Piton de la Fournaise’.
Material examined. Holotype: male 16.2 × 18.9 mm (MNHN-IU- 2013 - 7243), lava tube ‘ Brûlé des Citrons Galets’, Le Tremblet, Saint Philippe, Réunion Island, coll. N. Crestey and J. - P. Le Guelte, 16 March 2018. Paratypes (same data as holotype): 1 female 13.7 × 16.9 mm (MNHN-IU- 2013 - 7240), 1 female 13.1 × 16.5 mm (MHNH-IU- 2013 - 7241), coll. N. Crestey and J. - P. Le Guelte, 16 November 2017. Additional observations. In situ photographs (no specimens collected) from lava tubes: ‘ Grotte au Trésor’, photograph Christopher Lauret, 3 March 2016; ‘ Coulée de 2004 ’, photograph F. Leveneur, 30 August 2014 and Julien Dez, 14 February 2018; ‘ Grotte des Hirondelles’, photograph François Martel-Asselin, 2 May 2010. Type locality. Lava tube ‘ Brûlé des Citrons Galets’, Le Tremblet, Saint Philippe, Réunion Island.