Munidopsis bamberi, Schnabel, Kareen E. & Ahyong, Shane T., 2015

Schnabel, Kareen E. & Ahyong, Shane T., 2015, Two new species of Munidopsis (Crustacea: Anomura: Munidopsidae) from the Kermadec and Louisville ridge systems off New Zealand, Zootaxa 3995 (1), pp. 241-251 : 242-245

Munidopsis bamberi sp. nov.

( Fig. 2 )

Material examined. Holotype - male (cl 20.8 mm, pcl 16.2 mm) ( NIWA 86378) Havre trough, west of Rumble II seamount, Kermadec volcanic arc, New Zealand, 35°23.60–23.84’S, 178°13.66–13.99’E, 26 October 2012, 2890– 3000 m, stn. TAN1213/51.

Diagnosis. Carapace length (including rostrum)1.8 times as long wide; rostrum spiniform, unarmed but with slightly irregular lateral margins; minute antennal spine; lateral margins subparallel, with four prominent spines behind anterolateral spine, posteriormost at base of cervical groove; gastric region with pair of prominent epigastric spines followed by three transverse rows of three, four and two spines, respectively; anterior branchial region with two spines near lateral margins; cardiac region with three rows of submedian spines. Abdominal tergites 2–4 with spines on elevated transverse ridge, three spines on tergites 2–3, one spine on tergite 4; tergite 6 with prominent rounded lobe on mid-posterior margin. Ocular peduncle immovably fused to carapace; strong mesial eyespine only, directed straight forward. Cheliped without denticulate carina on distolateral margin. Pereopods 2 and 3 overreaching pereopod 1; dactyli not cristate. Pereopods without epipods.

Description. Carapace: Moderately convex in cross section; with a few scattered setae; length including rostrum, 1.8 times as long as wide (pcl 1.3 times width). Rostrum 0.4 pcl, slender, spiniform, unarmed, slightly deflected dorsad; dorsal surface smooth, sparsely setose; lateral margin smooth to minutely dentate. Frontal margin strongly oblique; minute antennal spine. Anterolateral spine small. Lateral margins subparallel; branchial margin with three spines anterior to cervical groove and one spine posterior to cervical groove, followed by serration. Posterior margin with four spines. Regions of carapace well defined dorsally; cervical groove distinct; anterior half with surface smooth apart from spines and a few scattered tubercles; posterior half with short, curved striae, especially on branchial regions. Gastric region with pair of prominent epigastric spines followed by three transverse rows of three, four and two spines. Anterior branchial region with two spines close to lateral margin, anterior spine placed mesiad to posterior spine, posterior spine slightly overhanging lateral margin. Posterior branchial region with two spines behind cervical groove. Cardiac region with three pairs of submedian spines: first pair directly behind cervical groove, second “pair” (left spine flanked by additional spine) on anterior ridge of low triangular, cardiac elevation, third pair placed approximately mid-way between second pair and posterior carapace margin. Overall disposition of paired submedian dorsal spines on gastric and cardiac regions forming two parallel longitudinal rows of spines. Pterygostomian flap lateral surface with short oblique striae, a few low anterior tubercles; anterior margin rounded.

Sternum: 1.1 times as wide as long; sparsely setose along margins and sternite boundaries. Sternite 3 lateral margin subacute; anterior margin with paired submedian processes; with shallow median notch; surface smooth. Sternite 4 4.3 times as wide as sternite 3; anterior margin narrowed; lateral margin shallowly concave; surface with single pair of transverse striae, otherwise smooth. Remaining sternites smooth, unarmed.

Abdomen: Sparsely setose. Tergites 2–3 each with three spines on anterior ridge and shallow transverse groove posteriorly. Tergite 4 with single median spine on anterior ridge and faint transverse groove on either side of midline. Tergite 5 unarmed; with faint transverse groove on either side of midline. Tergite 6 with prominent, rounded median posterior lobe. Telson 1.3 times as broad as long, composed of eight plates.

Eyes: smooth, immovably fused to carapace; with distinct mesial eye spine which directed straight forward. Cornea subglobular, 0.6 times as wide as peduncle.

Antennule: surface smooth other than transverse field of scattered granules at midlength; distodorsal and distolateral spines well developed, distolateral longest, overreaching remaining terminal spines; distomesial and distoventral spines small; lateral margin swollen.

Antenna: article 1, distomesial and distolateral margins each with short spine, not reaching midlength of article 2. Article 2 with distinct distolateral and small distomesial spine. Article 3 with small distolateral and more pronounced distomesial spine. Article 4 with two minute distal spines laterally and mesially.

Maxilliped 3: surface smooth, sparsely setose. Ischium with small distal extensor spine and larger distal flexor spine. Crista dentata with uniform row of 22 teeth on ischium and three teeth (median largest) on basis. Merus extensor margin with small spine in proximal quarter and distinct distal spine; flexor margin with four proximal spines, proximal two largest. Carpus, propodus and dactylus unarmed.

Pereopod 1 (cheliped): stout, 1.4 times as long as carapace (including rostrum); surface moderately spinose and setose. Ischium with small distodorsal and distoventral spines, with small scattered spines on surface. Merus with longitudinal rows of large spines, interspersed with small spines and granules; four distal spines. Carpus spinose, with four distal spines, length 0.6 times as long as that of palm. Propodal palm 1.8 times as long as high, a few scattered spines. Dactylus 1.2 times as long as palm; both fingers unarmed; occlusal margin evenly dentate, not gaping; apices with interlocking teeth. Pollex outer distal margin smooth, without carina.

Pereopods 2–4: surfaces spinose and sparsely setose. Pereopod 3 anteriorly overreaching pereopod 1 by half length of dactylus. Pereopod 2 damaged but estimated to overreach pereopod 1 by length of dactylus. Pereopod 2– 4 meri decreasing in length posteriorly with pereopod 4 merus being 0.8 times as long as that of pereopod 2. Merus about as long as propodus; with extensor and flexor margins with six or seven prominent well-spaced spines (including distal) interspersed with a few smaller spines or tubercles. Carpus with row of five prominent extensor spines and a few smaller spines, penultimate distal spine largest; with single flexor spine distally. Propodus slender (12–13 times as long as wide); extensor margin with one or two spines along proximal half and several acute tubercles; flexor margin unarmed bar minute distal pair of movable spines. Dactylus nearly straight; about 0.6 times as long as propodus; flexor margin lined with 12 or 13 small triangular teeth, each with small movable spine, distalmost proximal to base of unguis.

Epipods: absent on pereopods 1–4.

Colour in life. Uniform pale white with bright orange eyes.

Remarks. Munidopsis bamberi sp. nov. belongs to the group of species within the genus sharing a dorsally spinose carapace, a distinct mesial eye-spine, pereopods without epipods, and a cheliped without a serrated carina on the outer distal margin on the pollex that is overreached by the first walking leg: M. abyssicola Baba, 2005 , M. arietina Alcock & Anderson, 1894 , M. bairdii ( Smith, 1884) , M. chacei Kensley, 1968 , M. colombiana Pequegnat & Pequegnat, 1971 , M. echinata Osawa, Lin & Chan, 2008 , and M. tiburon Jones & Macpherson, 2007 . Among these, M. abyssicola , M. arietina , M. bairdii , M. chacei and M. tiburon differ from M. bamberi in having unarmed instead of spinose abdominal tergites 2–4. Munidopsis bamberi is closest to M. echinata (from Taiwan), agreeing in almost all respects but differing in carapace ornamentation. In M. echinata , the carapace surface is distinctly more tuberculate with fewer or less pronounced dorsal spines. In M. bamberi , the dorsal spines are all well-developed and the surrounding carapace surface has very few, if any tubercles, especially on the anterior half. In contrast, the surface of the anterior half of the carapace in M. echinata is distinctly tuberculate and the dorsal spines less pronounced. Additionally, M. echinata lacks antennal spines and the posterior row of cardiac spines present in M. bamberi . Munidopsis colombiana is readily distinguished from M. bamberi by its distinctly arcuate instead of subparallel carapace margins and much larger antennal spines (subequal to instead of much smaller that the anterolateral spines).

In New Zealand waters, M. bamberi most closely resembles Munidopsis abyssicola and M. antonii , both of which, however, differ from M. bamberi in having a smooth, unarmed abdomen ( M. bamberi has spines on tergites 2–4), in lacking distinct longitudinal submedian rows of spines on the carapace ( M. bamberi has a row of five paired submedian spines running from the gastric to the cardiac regions of the carapace). These two species also reach very large body sizes (cl> 40 mm) while the single specimen of M. bamberi is mature at a comparably small size of cl ~ 21 mm. Further collections will clarify the range of body size in this new species.

Munidopsis bamberi shares the character of spinose abdominal tergites with the New Zealand endemic M. kaiyoae Baba, 1974 , but M. kaiyoae lacks an eye spine (a mesial eye spine is present in M. bamberi ), has a smooth lateral carapace margin (a distinct row of lateral spines is present in M. bamberi ), the dorsal carapace with a pair of epigastric spines followed by a single median gastric spine and a cluster of median cardiac spines only (see above for dorsal ornamentation in M. bamberi ), and the palm of the cheliped is longer than the movable finger (the palm is shorter than the movable finger in M. bamberi ).

Munidopsis bamberi was taken from a depth of nearly 3000 m in the Havre Trough about 30 km west of the volcanically active Rumble II seamount. Notes on volcanic rocks collected at the site indicate that most were of fresh lava ( Wysoczanski et al. 2012) but the proximity of the holotype to active venting is not known.

Distribution. Known only from the Havre Trough, west of Rumble II Seamount, Kermadec Arc, New Zealand; 2890–3000 m.

Etymology. This species is named in honour of Roger Bamber, in acknowledgement of his contribution to arthropod taxonomy and systematics. Appreciation for his collegiality is extended from the NIWA Invertebrate Collection team in Wellington.

Figures

FIGURE 2. Munidopsis bamberi sp. nov., holotype male, cl 20.8 mm (NIWA 86378). A, cephalothorax and abdomen (arrows indicate antennal spines, enlarged); B, cephalothorax and abdomen, right lateral view; C, right basal antennular segment, lateral view; D, right basal antennular segment, ventral view; E, right antenna, ventral view; F, right maxilliped 3; G, right crista dentata; H, sternal plastron; I, telson; J – K, left cheliped, dorsal and lateral view; L, left cheliped fingers, mesial view; M – O, left pereopods 2 – 4. Scale bars: 4.0 mm for A, B, I – O; 2.0 mm for C – H.