Munida alba, Liu & Li & Lin, 2020

Liu, Xinming, Li, Xinzheng & Lin, Rongcheng, 2020, A new squat lobster species of the genus Munida Leach, 1820 (Crustacea: Anomura: Galatheoidea: Munididae) from hydrothermal vents on the Eastern Pacific Rise, Zootaxa 4743 (1), pp. 131-136 : 132-135

Munida alba sp. nov.

Material examined. HOLOTYPE: TIO-21III-S6-TVG2-C(8), ♂ (cl 13.2 mm, pcl 9.4 mm), Eastern Pacific Rise , hydrothermal vent field, 1.23º S 101.49° W, 1444 m, 28 Oct. 2009, benthic grab, RV Dayangyihao.

Description. Carapace (excluding rostrum) 1.3 × longer than wide; main transverse ridges with dense, short non-iridescent setae, some ridges interrupted as illustrated; few secondary striae between main transverse ridges; most ridges and striae with setae. Anterior gastric region elevated, with pair of 4 blunt spines and scattered tiny granules laterally. No spines on other dorsal regions. Hepatic region depressed. Lateral margins slightly convex in general. Anterolateral spines not reaching level of sinus between rostrum and supraocular spine. Hepatic margins strongly convex, each with spine smaller than anterolateral spine. Branchial margins each with 5 spines, decreasing in size posteriorly. Frontal margins slightly oblique. Rostrum spiniform, almost half pcl, slightly curving dorsad on distal part. Supraocular spines relatively short and stout, slightly diverging anteriorly, slightly ascending in lateral view, reaching base of corneas, about 0.4 length of rostrum ( Figs. 1A , 2G ). Pterygostomial flap pointed anteriorly, with minute granule; lateral face rugose with scattered obliquely transverse ridges.

Thoracic sternal plastron distinctly widened posteriorly, smooth, without striae. Third thoracic sternite about 2.3 × wider than long, much wider than anterior width of fourth sternite, Fourth sternites broadly triangular, with posterior portion deeply concave. Transverse ridges between sternites nearly smooth, with row of short setae ( Fig. 2G ).

Abdominal somites unarmed. Second to fourth abdominal tergites with 2 elevated transverse ridges. Second abdominal somite slightly narrower than third somite; transverse ridges nearly smooth. Sixth abdominal somite with undulated ridge on posterior portion. Telson 1.4 × as wide as long; median suture clearly delimited ( Figs. 1A, F ).

Eyes small; corneas not dilated, corneal width equal with basal width of ocular peduncle and distance between sinus formed by supraocular and rostral spines ( Fig. 1A ).

Basal segment of antennule (distal spines excluded) about 0.4 × pcl, nearly reaching end of rostrum, with 2 distal spines, mesial spine about half length of lateral spine; lateral margin with 2 spines, distal spine 2.8 × length of proximal spine, slightly overreaching distolateral spine ( Fig. 1C ).

First segment of antennal peduncle with moderately long distomesial spine nearly reaching distal margin of second segment; second segment with 1 small spine each at disomesial angle, with 1 strong spine at distolateral angle overreaching midlength of third segment. Third to fourth segment unarmed. ( Fig. 1D )

Third maxilliped with setae mostly on flexor margin of segments. Ischium about 2.5 × length of merus measured along extensor margin, with crista dentata of numerous minute teeth. Merus with a single well-developed spine arising at about midlength of flexor margin ( Fig. 2F ).

Right cheliped (first pereopod, P1) missing. Left P1 intact, about 2 × pcl. Merus with row of 6 spines on dorsal surface laterally, spines increasing in size distally, dostalmost spine strongest and clearly diverging; dorsomesial margin with 2 spines distally, spine at distomesial angle larger; lateral face with spinulose tubercles ventrally and with 1 strong spine at ventrodistal angle; ventromesial margin with 3 strong spines (spines increasing in size distally, distalmost spine much stronger than others and distinctly diverging); ventral surface smooth. Carpus twice as long as wide; about 0.8 × as long as palm; dorsal surface with 4 small spines along midline; dorsomesial margin with 3 strong spines (distal spine strongest), ventromesial margin with 3 spines; mesial face with short setae; ventral face smooth, with only 1 spine at ventral angle. Palm about 2 × longer than wide; dorsal surface with row of 4 moderately small spines mesial to midline; lateral margin with row of 6 spines (2 spines on pollex); dorsomesial margin with 3 spines increasing in size distally; ventromesial margin with 4 spines; dorsal and ventral surfaces with dense short setae. Pollex with 3 small, triangular teeth on cutting edge. Dactylus as long as palm, terminating in sharp, curved claw crossing tip of pollex; mesial margin unarmed ( Fig. 1E ).

Second to fourth pereopods (P2–4) moderately long and slender, decreasing in length posteriorly. P2 about 2 × pcl; merus as long as carapace, dorsal margin with row of 7 spines, spine at dorsoldistal angle prominent but other spines small, ventral margin with 7 spines, spine at ventrodistal angle largest, lateral and ventral surfaces smooth; carpus with 1 strong extensor distal spine and 1 flexor distal spine, lateral surface nearly smooth; propodus with row of 5 movable spines on flexor margin, extensor margin unarmed; dactylus about half length of propodus, slightly curved distally, with 6 movable spines on flexor margin. P3 about 1.9 × pcl; merus about 0.9 × length of P2 merus, with 9 spines (2 spines much smaller) on dorsal margin and 7 spines on ventral margin; carpus with 1 strong extensor distal spine and 1 flexor distal spine; propodus with 5 moveable spines on flexor margin; dactylus with 9 movable spines on flexor margin. P4 about 1.7 × pcl; merus about 0.7 × length of P2 merus, with 1 strong dorsodistal spine and 5 spines on ventral margin; carpus with extensor and flexor distal spines; propodus with 4 movable spines on flexor margin; dactylus with 9 movable spinules on flexor margin ( Fig. 2 A–C).

Fifth pereopod length about 0.8 × pcl; all segments unarmed; chela elongate, bearing numerous short setae on extensor and flexor faces ( Fig. 2D, E ).

Coloration. Entirely whitish ( Fig. 3 ).

Etymology. From the Latin, alba , white, referring the fresh coloration of the species.

Remarks. Munida alba sp. nov. closely resembles M. ampliantennulata Komai, 2011 and M. watatsumi Komai, 2014 in the well-developed anterolateral spine and five branchial marginal spines of the carapace, the frontal margins of the carapace being oblique rather than transverse, the absence of spines on the anterior transverse ridge of the second abdominal somite, the small, non-dilated eyes (the corneal width is equal to or less than the distance between the sinus formed by the supraocular and rostral spines), and the palm of the cheliped having a row of small but distinct spines on the dorsal midline. However, M. alba sp. nov. is distinguished from M. ampliantennulata by the following features: 1) a single strong spine is present on the flexor margin of the merus of the third maxilliped (2 spines in M. ampliantennulata ); 2) cheliped pollex with 3 small, triangular teeth on the cutting edge and two distinct spines are present on the lateral margin (cutting edge faintly denticulate in proximal 0.8, with row of minute teeth in distal 0.2, a few minute spines are present on the lateral margin of the pollex in M. ampliantennulata ); 3) rostrum about half pcl (0.3 pcl in M. ampliantennulata ); 4) third segment of antennal peduncle unarmed (with minute spine at distolateral angle in M. ampliantennulata ); and 5) the palm of the cheliped is longer than the carpus and lacks spines on mesial face (palm is subequal in the length to the carpus and with one or two spines on the mesial face in M. ampliantennulata ).

Munida alba sp. nov. is distinguished from M. watatsumi by: 1) a single strong spine is present on the flexor margin of the merus of the third maxilliped (2 spines in M. watatsumi ); 2) cheliped pollex with 3 small, triangular teeth on cutting edge (versus row of minute rounded denticles in M. watatsumi ); 3) the third segment of the antennal peduncle is unarmed (with minute spine at distolateral angle in M. watatsumi )

Munida magniantennulata is also similar to M. alba sp. nov. However, the new species is distinguished from M. magniantennulata by: 1) the less convex anterolateral margin of the carapace; 2) the spine on the first segment of antennal peduncle overreaches the midlength of the second segment (short spine in M. magniantennulata ); 3) the possession of only one spine on the flexor margin of the third maxilliped merus (three spines present in M. magniantennulata ); 4) two distinct spines are present on the lateral margin of the cheliped pollex (without conspicuous spines in M. magniantennulata ).

Figures

FIGURE 1. Munida alba sp. nov., holotype, ♀ (pcl 9.4 mm): A, carapace and abdomen and cephalic appendages, dorsal view; B, sternal plastron, ventral view; C, basal segment of right antennule, ventral view (setae omitted); D, right antenna, ventral view; E, left P1, dorsal view (setae omitted); F, sixth abdominal somite, telson, and uropods (setae on the telson and uropods omitted). Scale bar: 3 mm for A, B, E; 1 mm for C, D, F.

FIGURE 2. Munida alba sp. nov., holotype, ♀ (pcl 9.4 mm): A, left P2, lateral view; B, left P3, lateral view (setae omitted); C, left P4, lateral view (setae omitted); D, left P5, lateral view (setae omitted); E, dactylus of right P5, ventral view; F, right third maxilliped, external view; G, anterior part of carapace, lateral view. Scale bar: 4 mm for A, B, C, D; 0.8 mm for E; 2 mm for F; 3 mm for G.

FIGURE 3. Munida alba sp. nov., holotype, ♀ (pcl 9.4 mm). Fresh coloration, dorsal and ventral view.