Munidopsis spiridonovi, 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 : 210-213

Munidopsis spiridonovi sp. nov.

Figs 7 –9

Type material. HOLOTYPE: AM P92562, female (cl 18.2 mm, pcl 12.8 mm), Coco-de-Mer Ridge, 01°06.5'N 56°28.7'E, 1280–1380 m, Cruise 36, stn 3779, 1280– 1380 m, RV Akademik Kurchatov, 4 May 1983 . PARATYPE: ZMM, male (cl 18.8 mm, pcl 13.1 mm), collected with holotype.

Other material examined.— Southeast Indian Ridge, Indian Ocean: MNHN IU-2011-5083 , 2 juvenile females (cl 8.2 mm, pcl 5.7 mm; cl 8.1 mm, pcl 5.7 mm), nearAmsterdam Island, 37°47.20'S 77°38.98'E, 940–1680 m , JASUS CP7 , MD 50, 9 July 1986.

Diagnosis. Rostrum broad, flat, medially carinate, trifid distally. Carapace with pair of epigastric spines, otherwise unarmed dorsally; surface of dorsal half with granules and short rugae; lateral margins with 4 spines (1 anterolateral, 3 branchial); posterior orbital margin transverse; outer orbital spine distinct. Abdominal tergites unarmed. Telson with 8 plates. Maxilliped 3 merus flexor margin with 3 spines. Cheliped carpus length more than twice width, dorsal surface with row of spines; merus with 3 longitudinal rows of prominent spines (dorsal, mesial, ventromesial). Walking leg meri distinctly spinose along extensor margin; dactylus flexor margin lined with movable spines, distalmost at base of corneous unguis. Pereopods without epipods.

Description of adults. Carapace: Moderately convex from side to side; covered with short, fine setae; surface of anterior half with granules and short rugae; surface of posterior half with short rugae and distinct striae. Cervical groove indistinct. Pair of epigastric spines. 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; with 2 spines on anterior branchial margin and spine at junction of anterior and posterior branchial margins. Rostrum broad, 0.4 pcl; trifid distally; apex horizontal or slightly deflected dorsally; median carina distinct; lateral proximal margin convex. Posterior margin unarmed, medially emarginated. Pterygostomian flap with short diagonal striae; anterior margin blunt, angular.

Sternum: Sternite 3 about 0.3 width of sternite 4. Posterior margin of sternite 3 contiguous with anterior margin of sternite 4. Sternites smooth, sparsely setose, unarmed.

Abdomen: Tergites with short, fine, scattered setae, without spines. Tergites 2–4 with elevated anterior ridge; tergites 2 and 3 also with shallow groove behind anterior ridge. Tergites 4 and 5 with shallow, medially interrupted, transverse groove. Tergite 6 smooth; posterior margin not strongly produced. Telson composed of 8 plates (minute central plate present); lateral margin of midlateral plate lined with coarse, relatively stiff setae in males, distally setose in females. Uropodal endopod lateral margins setose, unarmed.

Eye: Ocular peduncle unarmed, sparsely setose; movable; partially concealed by rostrum. Cornea subglobular, slightly wider than peduncle. Small, 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 spine, reaching midlength but not apex of article 3. Article 3 with distomesial spine. Article 4 unarmed. Flagellum slightly shorter than pcl.

Maxilliped 3: Dactylus, propodus and carpus unarmed. Merus extensor margin with 2 small, blunt to acute tubercles and distal spine; flexor margin with 2 large triangular spines proximally and 1 or 2 smaller spines distally. Ischium longer than wide, with distal flexor and extensor spine.

Pereopod 1 (cheliped): Cheliped elongate, 3.7 pcl (male paratype), 3.6 pcl (female holotype); with tufts of long, simple golden setae, most numerous on mesial and lateral margins; subcylindrical to ovate. Ischium with ventrodistal spine and dorsal spine. Merus with row of 8 or 9 strong, graded dorsal spines, largest distally; mesial margin with distal row of 3 or 4 mesial spines, largest distally at carpal articulation; ventromesial margin with longitudinal row of 3 strong spines proximally and distal spine. Carpus 2.1–2.3 times longer than wide; mesial margin with distal and subdistal spine, latter largest; distodorsal spine followed by longitudinal row of 1–5 (usually 3 or more) dorsal spines; distoventral spine. Propodus unarmed, palm 2.8–3.1 times as long as wide; mesial margin of palm about 1.5 times longer than dactylus. Pollex and dactylus occlusal margins crenulated, apices with interlocking teeth; pollex occlusal margin with proximal gape (more pronounced in male) and low tooth slightly distal to midlength; dactylus occlusal margin with proximal swelling, forming subquadrate tooth on male. Epipod absent.

Pereopods 2–4: Slightly compressed; decreasing in length posteriorly; with scattered, setose striae. Merus elongate; length 4.0–4.1 times width (pereopod 2) to 3.1 (pereopod 4); extensor margin lined with prominent upright spines, longest on pereopod 2, shortest on pereopod 4; distal extensor margin with large distal spine; flexor margin serrated, 1 or 2 occasionally forming short spine in addition to strong distal spine. Carpus with row of 4 or 5 extensor spines (pereopod 2), 1 or 2 extensor spines (pereopod 3), 1 distal extensor spine and serrated margin (pereopod 4); low, irregular, dorsal carina. Propodus extensor margin irregular, unarmed; flexor margin with movable spine at distal one-fourth and paired movable spines distally adjacent to dactylar articulation. Dactylus about 0.6 propodus length; extensor margin with scattered setae, unarmed; flexor margin with 10–12 low triangular teeth, each bearing corneous movable spine, distalmost movable spine at base of corneous unguis. Epipods absent.

Egg diameter: 1.3 mm.

Colour in life. Unknown.

Etymology. Named for Vassily Spiridonov, for kindly making material available for study and for his important contributions to decapod systematics.

Remarks. Among the serricornis -complex species, Munidopsis spiridonovi sp. nov. is closest to M. pyrochela sp. nov. and the western Atlantic M. transtridens in sharing a pair of epigastric spines, spinose extensor margins of the walking leg meri, and a prominent mesial spine on the cheliped carpus. Adult M. spiridonovi differs from M. pyrochela in having more elongate chelipeds, with the carpi armed with a row of dorsal spines, and carpal length more than twice width versus less than twice width. The cheliped length of adult M. spiridonovi exceeds 3.6 pcl whereas the chelipeds of M. pyrochela do not exceed 3.0 pcl. Munidopsis spiridonovi is very similar to M. transtridens in proportions and spination of the cheliped carpus (according to Mayo, 1974), but differs in having a markedly less setose carapace (sparse, short scarcely visible setae versus long prominent setae) and more elongate chelipeds in adults. The proportional length of the cheliped palm in adult M. spiridonovi is about 1.5 times dactyl length (versus 1.3 or less in M. transtridens ), the cheliped merus is distinctly longer than pcl (almost as long as cl) rather than being about as long as pcl, and the cheliped length is greater than 3.6 pcl compared to about 3.0 pcl.

Variation between the male and female type specimens is slight, being most marked in the sexually dimorphic chelae in which the male cheliped fingers have a distinct versus slight gape ( Fig. 7A, 8L ). The carpus of the cheliped of the holotype has a dorsal row of two spines on the right side, four on the left ( Fig. 8A, J ). The male paratype has six dorsal carpal spines. The merus of maxilliped 3 is armed with three flexor spines, of which the distalmost ranges from smaller than to as large as the other two spines ( Fig. 7E, 8K ). The two juvenile females from the Southeast Indian Ridge ( Fig. 8A–J ), although lacking the row of carpal spines on the cheliped, are presently assigned to M. spiridonovi . They agree well with the adults in almost all features, but have a row of raised angular, dorsal prominences on the cheliped carpus rather than spines, an unarmed carpal extensor margin (excluding the distal spine) on pereopod 2, less prominent meral extensor spines on the walking legs, and a proportionally shorter cheliped in which the length is about 2.5 pcl with merus slightly shorter than pcl and palm about 1.2 times dactylus length. Although these juveniles potentially represent a different species in which diagnostic characters are yet to be fully expressed, each of the aforementioned differences between adults and juveniles are consistent with expected allometric changes in M. spiridonovi , and parallel changes in M. transtridens , which may also have a dorsal row of carpal spines on the cheliped in adults ( Pequegnat & Pequegnat, 1971; Mayo, 1974; Tavares et al., 2008).

Distribution. Western Indian Ocean from seamounts on the Coco-de-Mer Ridge and the Southeast Indian Ridge, near Amsterdam Island; 940–1680 m.

Figures

Figure 8. Munidopsis spiridonovi sp. nov. A–K: juvenile female, cl 8.2 mm, pcl 5.7 mm (MNHN IU-2011-5083). L–M, male paratype, cl 18.8 mm, pcl 13.1 mm (MMZ).(A) dorsal habitus; (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 ischiomerus, lateral view; (H) right carpus and ischiomerus, mesial view; (I) sternal plastron; (J) telson; (K) right maxilliped 3 carpus and merus; (L) right cheliped carpus to dactylus. Scale: A, B, G, H, J = 1.0 mm; C–F, I = 0.5 mm; L–M = 2.3 mm.