Munida exilis, Ahyong, Shane T., 2007

Ahyong, Shane T., 2007, Decapod Crustacea collected by the NORFANZ Expedition: Galatheidae and Polychelidae, Zootaxa 1593, pp. 1-54 : 25-26

Munida exilis sp. nov.

( Fig. 13 , 14A )

Type material. Holotype: NIWA 28067, female (13.7 mm), West Norfolk Ridge, 34°17.09’S, 168°21.50’E, 785–800 m, TAN0308/141 #10, 2 Jun 2003. Paratypes: AM P73022, 2 females (5.7–6.1 mm pcl), southern Norfolk Ridge, 33°23.60’S, 170°12.38’E, 469–490 m, TAN0308/136#81, 1 Jun 2003; NMNZ, 1 ovigerous female (6.0 mm pcl), southern Norfolk Ridge, 33°23.41’S, 170°11.58’E, 469–526 m, TAN0308/126 #79, 31 May 2003; NMNZ, 1 male (11.4 mm), southern Norfolk Ridge, 33°23.60’S, 170°12.38’E, 469–490 m, TAN0308/136#80, 1 Jun 2003.

Diagnosis. Carapace margins with 5 spines posterior to cervical groove; frontal margins almost transverse; supraocular spines parallel; anterolateral spine extending beyond base of sinus between rostrum and supraocular spine; anterior branchial and postcervical spine absent. Rostrum spiniform. Sternite 4 anterior margin trianguloid, narrowly contiguous with third sternite; sternites 5–7 smooth. Abdominal tergite 2 with row of spines on anterior border; tergite 3 unarmed. Maximum corneal diameter half basal distance between anterolateral spines. Antennular basal segment with distomesial spine shorter than lateral. Antennal basal segment with blunt inner mesial angle; segment 2 with long mesial and lateral terminal spines, mesial overreaching distal segment of peduncle, lateral reaching midlength of segment 4. Maxilliped 3 merus extensor margin unarmed. Cheliped slender, about 3.0 times carapace length; pollex ventral margin unarmed; carpus about 6 times as long as wide. Pereopods 2–4 dactylus flexor margin with terminal 0.4 unarmed.

Description. Carapace: Transverse ridges well spaced, with few secondary striae; cervical groove distinct; with pair of distinct epigastric spines behind supraocular spines, flanked medially by 1 and laterally by 2 smaller spines, forming transverse row; parahepatic spine flanked by several small granules; anterior branchial and postcervical spine absent. Frontal margins almost transverse; rostrum spiniform, horizontal, about twice as long as supraocular spines and about half remaining carapace length. Supraocular spines parallel. Anterolateral spine slightly divergent, situated at anterolateral angle, extending beyond base of sinus between rostrum and supraocular spine. Margins of carapace anterior to cervical groove with 3 spines (including anterolateral); with 5 spines posterior to cervical groove.

Sternum: Sternite 3 transversely subquadrate. Sternite 4 with pair of striae, otherwise smooth; anterior margin trianguloid, narrowly contiguous with sternite 3. Sternites 5–7 smooth. Ridges demarcating sternites feebly granular.

Abdomen: Tergite 2 with row of 6 spines on anterior border and 1 transverse stria. Tergite 3 unarmed, with 1 transverse stria. Tergite 4 with 1 transverse stria. Tergite 5 with 1 uninterrupted anterior stria and medially interrupted posterior stria.

Eye: Large, with maximum corneal diameter half basal distance between anterolateral spines; peduncle with row of long distal setae.

Antennule: Basal segment elongate, slightly overreaching cornea; distomesial spine shorter than lateral; with 2 lateral spines, distal markedly longer than proximal.

Antenna: Basal segment with blunt inner mesial angle. Segment 2 with long mesial and lateral terminal spines, mesial overreaching distal segment of peduncle, lateral overreaching segment 3; mesial margin with or without small spine. Segments 3 and 4 unarmed.

Maxilliped 3: Ischium with small distal flexor spine. Merus as long as ischium; flexor margin with strong distal and proximal spine; extensor margin unarmed.

Pereopod 1 (cheliped): Slender, about 3.0 times carapace length; with short squamae, and acute granules or small spines; sparsely setose. Dactylus with small dorsal proximal spine and small subterminal spine; occlusal margin denticulate, with proximal gape in adult males. Propodus palm 6–7 times as long as high, longer than pollex; pollex with 2 subdistal spines. Carpus about 6 times as long as wide; sparsely spinose dorsally. Merus with irregularly distributed spines on lateral, dorsal and mesial surfaces; spines strongest distally.

Pereopod 2: Merus with 10–12 extensor and 6–8 flexor spines. Carpus with 2 extensor and 2 flexor spines. Propodus 6.3 times as long as high; extensor margin unarmed; flexor margin with 13 small movable spines. Dactylus 0.6 propodus length; flexor margin with 8 or 9 movable spines; terminal 0.4 of flexor margin unarmed.

Pereopod 3: Merus with distal extensor and 6 or 7 flexor spines. Carpus with extensor and 1 or 2 flexor spines. Propodus 6.1 times as long as high; extensor margin unarmed; flexor margin with 13 or 14 small movable spines. Dactylus 0.7 propodus length; flexor margin with 6 movable spines; terminal 0.4 unarmed.

Pereopod 4: Merus extensor margin unarmed; with 6–8 flexor spines. Carpus with distal extensor and 2 flexor spines. Propodus 6.3 times as long as high; extensor margin unarmed; flexor margin with 11 or 12 movable spines. Dactylus 0.7 propodus length; flexor margin with 5 movable spines; terminal 0.4 unarmed.

Colour in life. Base colour translucent white. Carapace ridges, rostrum, and spines orange-red. Chelipeds and walking legs pale, diffuse orange; spines orange-red.

Etymology. Named exilis (Latin) , thin, for the slender, elongated appearance of the species.

Remarks. Munida exilis sp. nov. most closely resembles M. amblytes Macpherson, 1994 , from New Caledonia, in having near-transverse frontal carapace margins with well-developed anterolateral spines, absence of anterior branchial or postcervical carapace spines, well-spaced striae, triangular sternite 4, unarmed terminal 0.4 of the flexor margin of the dactyli of the walking legs, and short distomesial spine on the basal antennular segment. The new species is readily distinguished from M. amblytes by its longer chelipeds (about three instead of about two times carapace length), parallel rather than divergent supraocular spines, longer anterolateral spines (reaching beyond the base of sinus between the rostral and supraocular spines), fewer spines on the anterior margin of abdominal tergite 2 (6 versus 8–10), and the longer outer spine on segment 2 of the antennal peduncle (reaching the midlength of segment 4 rather than apex of segment 3).

Distribution. Presently known only from localities on the southern Norfolk Ridge and West Norfolk Ridge; 469– 800 m.

Figures

FIGURE 13. Munida exilis sp. nov. A – I, female holotype, 13.7 mm, TAN 0308 / 141 (NIWA 28067). J, male paratype, 11.4 mm, TAN 0308 / 136 (NMNZ). A, dorsal view. B, right antennule, ventral view. C, right antenna, ventral view. D, right third maxilliped, lateral view. E, sternum. F, right cheliped, lateral view. G – I, right pereopods 2 – 4. J, right chela, lateral view. Scale: A, F – J = 2.0 mm; B – E = 1.0 mm.

FIGURE 14. A, Munida exilis sp. nov., male paratype, 11.4 mm, TAN 0308 / 136 (NMNZ). B, Munida howensis sp. nov., male holotype, 19.2 mm, TAN 0308 / 066 (AM). C, Munida redacta sp. nov., male holotype, 9.4 mm, TAN 0308 / 020 (AM). D, Munida rubrimana sp. nov., ovigerous female holotype, 15.0 mm, TAN 0308 / 043 (NMNZ). E, Munida tangaroa sp. nov., ovigerous female paratype, 14.1 mm, TAN 0308 / 29 (NIWA 28070).