Munidopsis nias, Ahyong, 2014

Ahyong, Shane T., 2014, Deep-sea Squat Lobsters of the Munidopsis serricornis Complex in the Indo-West Pacific, with Descriptions of Six New Species (Crustacea: Decapoda: Munidopsidae), Records of the Australian Museum (Rec. Aust. Mus.) 66 (3), pp. 197-216 : 204-206

Munidopsis nias sp. nov.

Figs 4 , 5 , 9

Munidopsis (Galathodes) tridentata .—Doflein & Balss, 1913: 158 [Indonesian specimens only].

Munidopsis serricornis .—Baba & Poore, 2002: fig. 6D, 7C, 8C, 9E.

Type material. HOLOTYPE: ZMB 17506, male (cl 13.4 mm, pcl 10.0 mm), off SE Nias, Indonesia, 0°27'N 98°07'E, 646 m, Deutsche Tiefsee Expedition, stn 196, 1 February 1899 . PARATYPES: ZMB 17505, 2 ovigerous females (cl 11.9+ mm, pcl 9.4 mm; cl 11.6 mm, pcl 8.6 mm), 1 juvenile female (cl 6.0 mm, pcl 4.0 mm), collected with holotype .

Diagnosis. Rostrum broad, subquadrate, flat, medially carinate, trifid distally. Carapace unarmed dorsally; surface of dorsal half smooth; lateral margins with 4 spines (1 anterolateral, 3 branchial); posterior orbital margin transverse; outer orbital spine distinct. Abdominal tergites unarmed. Telson with 7 plates. Maxilliped 3 merus flexor margin with 1 spine. Cheliped merus with 3 longitudinal rows of prominent spines (dorsal, mesial, ventromesial). Walking leg meri and carpi distinctly spinose along extensor margin; pereopod 2 merus stout, length 2.5 times width; dactylus flexor margin with movable spines, distalmost remote from corneous unguis. Pereopods without epipods.

Description of adults. Carapace: Moderately convex from side to side; finely setose; surface of anterior half smooth, at most with very fine, short striae; surface of posterior half with fine striae. Cervical groove indistinct. Epigastric spines absent, at most a transverse row of short rugae. Posterior orbital margins transverse to slightly oblique, outer orbital spine prominent. Frontal margins oblique, slightly concave; anterolateral spine similar to outer orbital spine. Lateral margins broadly convex; carapace widest in posterior half; with 2 spines on anterior branchial margin and spine at junction of anterior and posterior branchial margins. Rostrum broad, subquadrate, 0.3–0.4 pcl; trifid distally; apex horizontal; median carina weakly indicated; lateral proximal margin straight or weakly convex. Posterior margin unarmed. Pterygostomian flap with short diagonal striae; anterior margin angular.

Sternum: Sternite 3 about one-third width of sternite 4. Posterior margin of sternite 3 broadly contiguous with anterior margin of sternite 4. Sternites smooth, sparsely setose, unarmed.

Abdomen: Tergites unarmed; surface with few scattered short setae, almost glabrous. Tergites 2–4 with elevated anterior ridge; tergites 2 and 3 also with shallow groove behind anterior ridge. Tergites 4–6 smooth; posterior margin not produced. Telson composed of 7 plates (minute central plate absent); lateral margin of midlateral plate lined with coarse, relatively stiff setae in males, non-setose in females. Uropodal endopod lateral margins setose, unarmed.

Eye: Ocular peduncle sparsely setose; movable; partially concealed by rostrum. Cornea subglobular, slightly wider than peduncle. Slender spine adjacent to lateral margin of eye.

Antennule: Basal article squat, with 2 distolateral spines, dorsal shorter; distomesial margin with short triangular tooth.

Antenna: Basal article with triangular mesial and lateral tooth, neither overreaching article 2. Article 2 with strong distolateral and distomesial spine, former reaching beyond midlength of article 3. Article 3 with mesial spine. Article 4 with triangular lateral projection. Flagellum about as long as pcl.

Maxilliped 3: Dactylus, propodus and carpus unarmed. Merus extensor margin with distal spine; flexor margin with 1 large, sharp, triangular spine. Ischium longer than wide, with acute distal flexor and extensor angles. Crista dentata with 22 or 23 denticles.

Pereopod 1 (cheliped): Elongate, 2.3 pcl in both sexes, simple golden setae, most numerous on dorsal and ventral margins; subcylindrical to ovate. Ischium with ventrodistal spine and dorsal spine. Merus with longitudinal row of 4–6 graded dorsal spines and large distal dorsal spine; mesial margin with 1 or 2 large spines, one distally at carpal articulation, one at distal one-fourth of margin (absent in female paratypes); ventromesial margin with proximal row of 3 proximal spines (first spine smallest) and strong distal spine. Carpus 1.2–1.5 times longer than wide; mesial margin with distal and subdistal spine, latter largest; dorsodistal and ventrodistal spine; occasionally with small lateral distal spine. Propodus unarmed, palm about twice as long as wide; mesial margin of palm longer than dactylus. Pollex and dactylus occlusal margins crenulated, apices with interlocking teeth. Epipod absent.

Pereopods 2–4: Slightly compressed; decreasing in length posteriorly; with scattered, setose striae. Merus stout; length about 2.4 times width (pereopod 2) to 2.0 (pereopod 4); extensor margin with 4 or 5 (pereopods 2 and 3) and 2 or 3 (pereopod 4) slender, obliquely directed spines and slender distal spine; flexor margin irregular, with distal spine. Carpus with distal extensor spine and row of 2 or 3 slender spines and several minute spines or serrations; with low, irregular, dorsal carina terminating in spine. Propodus extensor unarmed; flexor margin with movable spine at distal one-fourth and paired movable spines distally adjacent to dactylar articulation. Dactylus about two-thirds propodus length; extensor margin with scattered setae, unarmed; flexor margin with 7 or 8 low triangular teeth, each bearing corneous movable spine, without slender movable spine at base of unguis. Epipods absent.

Egg diameter: 1.2 mm.

Colour in life. Unknown.

Etymology. Named after the type locality, Nias, Indonesia; used as a noun in apposition.

Remarks. Records of Munidopsis tridentata from off Sumatra, Indonesia (Doflein & Balss, 1913) collected by the Valdivia, are referrable to M. nias sp. nov. Munidopsis nias sp. nov. is most similar to M. acuminata Benedict, 1902 (type locality: western Atlantic, off South Carolina) and M. pubescens Macpherson, 2007 (type locality: Madagascar) in sharing the broad, subquadrate, distally tridentate rostrum; unarmed dorsal surface of the carapace and abdomen; seven telson plates; short, squat, pereopods 2–4 with the length of the pereopod 2 merus not more than 2.5 times the width (versus about 3–4 times width) and two distal spines on the carpus. The new species differs from M. acuminata in lacking the epipod on the cheliped, having a straight or convex rather than slightly concave dorsal margin on the cheliped dactylus ( Fig 4A , 5A, B ) and the smooth versus rugose surface on the anterior half of the carapace. Munidopsis nias differs from M. pubescens in the smooth versus rugose anterior carapace surface, having a row of prominent spines on the extensor margin of the carpus of pereopods 2–4, a row of dorsal spines on the merus of the chelipeds and more extensive striation on the branchial regions of the carapace.

Variation in the type series of M. nias is slight, the main adult difference being in the number of mesial spines on the cheliped merus: two in the male holotype, one in the female paratypes. The juvenile female (pcl 4.0 mm) ( Fig. 5A ) has rudimentary pleopods and differs chiefly from the adults in having relatively more pronounced carapace spines, proportionally shorter chelipeds (twice pcl), fewer mesial and ventromesial spines on the merus of the chelipeds, and a proportionally shorter cheliped palm (slightly shorter than the dactylus versus longer in adults).

In addition to Indonesian material identified here as M. nias sp. nov., Doflein & Balss (1913) also reported material from off East Africa under the name M. tridentata . Given the strong similarities between M. nias and M. pubescens, Doflein & Balss’ (1913) East African records are probably referable to the latter species. Baba & Poore’s (2002: fig. 6D, 7C, 8C, 9E) record of M. serricornis from off Nias, Indonesia (Valdivia stn 198, 677 m), is referrable to M. nias . Material reported by Laurie (1926) as M. tridentata from Saya de Malha could not be located for the present study (Matt Lowe, pers. com., UMC), but are tentatively referred to M. pubescens Macpherson, 2007 , described from Madagascar. Laurie’s (1926) account was brief, but consistent with M. pubescens : the extensor margins of the meri of the walking legs are spinose, the carpi of the walking legs have two distal spines and only a single longitudinal row of spines on the cheliped merus (always two or three rows in M. nias ). The Saya de Malha specimens probably also lacked epigastric spines as in M. pubescens ; were epigastric spines present, they would almost certainly have been mentioned given Laurie’s (1926) succinct but detailed account of carapace and pereopodal spination. Saya de Malha is also geographically adjacent to the type locality of M. pubescens , Madagascar.

Distribution. Presently known only from the eastern Indian Ocean between Nias (Sumatra, Indonesia) and the Nicobar Islands; 646– 805 m.

Figures

Figure 4. Munidopsis nias sp. nov., male holotype, cl 13.4 mm, pcl 10.0 mm (ZMB 17506). (A) cephalothorax and abdomen, dorsal; (B) carapace, right lateral view; (C) right antenna and antennule, ventral view; (D) right basal antennular article, lateral view; (E) right maxilliped 3; (F) right crista dentata; (G) right cheliped dorsal view; (H) right cheliped carpus and ischiomerus, ventral view; (I) right cheliped finger tips, ventral view; (J) right pereopod 2, dorsal view; (K) right pereopod 3, dorsal view; (L) left pereopod 4, dorsal view; (M) telson; (N) sternal plastron. Scale: A, B, G–L = 2.0 mm; C–F, M, N = 1.0 mm.

Figure 5.Munidopsis nias sp.nov., female paratypes (ZMB 17506), right cheliped. (A) pcl 4.0 mm; (B) pcl 9.4 mm. Scale = 1.0 mm.