Gandalfus puia, Mclay, Colin, 2007

Mclay, Colin, 2007, New crabs from hydrothermal vents of the Kermadec Ridge submarine volcanoes, New Zealand: Gandalfus gen. nov. (Bythograeidae) and Xenograpsus (Varunidae) (Decapoda: Brachyura), Zootaxa 1524, pp. 1-22 : 5-8

Gandalfus puia sp. nov.

( Figs. 1 A–F, 2A–G, 3A–B, 4A–B, 5A–D)

Type material. Holotype: male, 24.3 x 15.5 mm, Rumble III, 35º44.22–44.04’S, 178º29.72–29.63’E, 270– 239 m, stn TAN0107/128, 21.05.2001, NZOI Z10782 ( NIWA 27855); Paratypes: 1 female 41.1 x 26.2 mm, Brothers Seamount, 34º51.56’W, 179º03.53’E, 1604 m, JAMSTEC, stn Z15262 , 26.10.2004 ( NIWA 27407); 1 female, 36.5 x 22.1 mm, Brothers Seamount, 34º51.70’S, 179º3.58’E, 1647 m, stn KOK0506/32, 0 2.05.2005 ( NIWA 18019); 1 male, 33.4 x 21.9 mm, Macauley Caldera, Kermadec Islands, 30º12.78’S, 181º33.04’E, 337 m, 12.04.2005 ( NIWA 18017).

Other material. 1 male, 36.7 x 22.6 mm (damaged), 1 male, 18.0 x 11.6 mm, Macauley Caldera, Kermadec Islands, 30º12.78’S, 181º33.04’E, 337 m, stn KOK0505/22, 12.04.2005 ( NIWA 18018).

Etymology. The specific name “ puia ” is the Maori word for volcano or geothermal spring, in reference to the fact that the type locality is on top of an underwater volcano near the Kermadec Islands, New Zealand; used as a noun in apposition.

Description. Carapace 1.53–1.65 times wider than long (length/width = 0.61–0.64), elliptical in outline, surface flat, coarsely granular especially on anterior half, convex along anterior-posterior axis, more steeply sloped in front than behind. Regions not well defined; cardiac-gastric regions marked by shallow U-shaped groove. Dorsal frontal margin almost straight, 0.19CW; small median lobe slightly prominent, adorned with 3 small granules; lateral margin granulate, concave, forming supra-orbital notch before merging with frontal region of carapace. Shallow median groove extending posteriorly from frontal margin. Anterolateral margins curved, convex, bearing granules that continue onto sub-branchial surface. Posterolateral margins convergent, posterior carapace margin sinuous, adorned by granular ridge. Sub-hepatic region without setae, Epimeral line well marked.

Front not projecting from anterior margin; orbits not visible dorsally; sub-orbital areas only slightly visible. Orbital region smooth, elongate, 0.4CW; interantennular septum incomplete, left-right division marked by small dorsal and ventral keels; posterior wall formed by immovable eyestalk, cornea vestigial, unpigmented, without facets and mostly concealed by lateral wall of orbit and overlying third article of antenna; floor of orbit formed by basal articles of antennule and antenna and lobe from carapace edge. All articles of antennule mobile; first (urinal) article of antenna fixed, second article with limited mobility, third and fourth articles mobile. Antennules and antennae folded horizontally; antennule filling most of orbit, almost meeting antennal peduncle; antenna filling supraorbital notch. Mesial antennular flagellum shorter than lateral flagellum. Antennal flagellum 0.8 length of dorsal frontal margin.

Epistome dorsal surface marked by ridge at lower border of orbit, almost vanishing at midline, edge not projecting, marked by row of granules, gently sinuous about midline; pterygostomial areas of mouth-field granulate.

Third maxilliped endopod ischia not touching when closed, 1.6 times longer than wide, strongly marked groove running alongside medial border; merus about as long as wide, half as long as ischium, medial border sinuous to accommodate palp which is inserted at tip of merus; carpus and propodus slightly longer than merus; dactyl slightly longer than ischium, inner margins of propodus and dactyl bearing a dense fringe of setae. Exopod longer than endopod ischium, terminating in small medial exterior lobe and hidden cristate lobe beside insertion of palp. On ventral surface, proximal surfaces of pereopods densely setose, especially in female, extending onto sternal surface. Margins of female abdomen densely fringed with setae.

Chelipeds distinctly longer than walking legs; merus triangular in cross section, corners granulate granules larger on anterior border. Chelipeds dimorphic, right (crusher) stouter than left (cutter); fingers excavated, gaping on right (touching only at tips), occluding on left; both fingers armed with several proximal teeth of variable size including one larger tooth at midlength of fixed fingers. Both left and right dactyli close behind tip of fixed finger. Ratio of propodus depth/length always greater on right (0.43–0.50) than on left (0.41–0.44) cheliped. Ratio of male cheliped propodus length/carapace width greater in male (0.92) than similar sized female (0.65).

Walking legs (P2-P5) shorter than chelipeds; second pair longest; carpi, propodi and dactyli fringed with long setae with a felt of short stiff setae on dorsal and ventral margins. Dactyli stout, terminating in sharp claw.

Abdomen of six free segments, third segment widest (0.3CW in male; 0.4CW in mature female); locking mechanism in male consisting of tubercle on sternite 5, near confluence of sutures 4/5 and 5/6, fitting into pit on posterolateral corners of last abdominal segment. Mature female without abdominal locking mechanism.

Male telson 1.4 x as wide as long, female 1.67, posterior border rounded. Sternal sutures from 4/5 to 7/8 not meeting in mid-line.

First male gonopod slender, stout, curved; with approximately 15 small spines and reaching anterior edge of abdominal cavity. Second male gonopod as long as first with notch at midlength and 15–20 small, marginal spines; tip flattened. Female gonopore slit-like 0.4 x 0.3 mm (female CW = 36.5 mm), oriented along anteriorposterior body axis, not operculate.

Colour. The male, 18.0 x 11.6 mm, is either recently moulted or lived at some distance from the vent: it is pale yellow/cream ground colour, fingers pale brown, setae on legs a darker brown. Other specimens are coated with a brown ferric precipitate. These colours were observed on the specimens examined and in photos taken at the time of collection.

Figures

FIGURE 1. Gandalfus puia sp. nov., holotype male, 24.3 x 15.5 mm, Rumble III (NZOI stn Z 10782). A, Dorsal view carapace (scale bar = 4 mm). B, magnified right anterolateral margin (scale bar = 2 mm). C, outer face right cheliped (scale bar = 4 mm). D, outer face left cheliped (scale bar = 4 mm). E, dorsal view right cheliped (scale bar = 4 mm). F, third maxillipeds (scale bar = 2 mm).