Munidopsis spinifrons Dong, Xu, Li & Wang, 2019

Munidopsis spinifrons Dong, Xu, Li & Wang, 2019 View in CoL

[New Japanese name: Kaizan-shinkai-koshiori-ebi]

( Figs. 9–11 View FIGURE 9 View FIGURE 10 View FIGURE 11 )

Munidopsis spinifrons Dong, Xu, Li & Wang, 2019: 7 View in CoL , figs. 3B, 4, 5. –– Rodriguez-Flores et al. 2023:

Material examined. JAMSTEC 106693, 1 female (cl 29.0 mm), KM20-10 C, KM-ROV dive #131, Ritto Seamount , West Mariana Ridge, 21°42.84´N, 142°04.62´E, 2054 m, 6 December 2020, suction sampler, DNA voucher GoogleMaps .

Abbreviated description. Carapace ( Fig. 10 View FIGURE 10 , 11A View FIGURE 11 ) 1.2 times longer than broad; frontal margins oblique, with upturned antennal spines; lateral margins nearly parallel; anterolateral spines relatively short; anterior branchial margins each with 4 spines diminishing in size posteriorly, anteriormost spine strongest, directed anterolaterally; posterior branchial margin rugose, with distinct spine at base of posterior cervical groove; posterior margin unarmed; dorsal surface covered with transverse, interrupted ridges, bearing sparse long setae; gastric region elevated, with 2 strong epigastric spines; cervical groove distinct; cardiac region with distinct transverse uninterrupted ridge. Rostrum slender, 0.4 times as long as carapace, strongly upturned in distal 0.3; dorsal surface bluntly carinate; ventrolateral margins each with 2 unpaired spinules; pterygostomial flap with oblique rugae on surface.

Thoracic sternite 3 broader than anterior margin of sternite 4, divided into 2 parts by median longitudinal groove; sternite 4 narrowly elongated with longitudinal groove in anterior part; posterior part broad, surface with short scales ( Fig. 11B View FIGURE 11 ).

Pleon tergites ( Fig. 10 View FIGURE 10 ) smooth and unarmed; tergites 2–4 each with 2 transverse ridges; tergite 6 posterior margin slightly tri-lobate, median lobe not produced beyond lateral lobes. Telson ( Fig. 11C View FIGURE 11 ) 1.4 times wider than long, composed of 10 distinct plates.

Ocular peduncle ( Fig. 11A View FIGURE 11 ) slightly movable, cornea small; mesial eye-spine prominent, anterolaterally directed, reaching to midlength of rostrum; lateral eye-spine small, adjacent to cornea, followed by minute spine at base of ocular peduncle.

Antennular peduncle basal article ( Fig. 11D View FIGURE 11 ) longer than broad, distal margin bearing strong ventrolateral spine and dorsolateral spine; lateral face slightly inflated, covered with short rugae.

Antennal peduncle ( Fig. 11A View FIGURE 11 ) reaching to mid-length of rostrum; article 1 with strong distomesial and distolateral spines; article 2 armed with strong distolateral spine and small mesial spine at midlength; article 3 subrectangular, with strong distomesial and distolateral spines, with minute dorsodistal spine; article 4 unarmed.

Maxilliped 3 merus ( Fig. 11E View FIGURE 11 ) subrectangular, extensor margin with distinct distal spine followed by small tubercle; flexor margin irregularly denticulate.

Chelipeds ( Figs. 10 View FIGURE 10 , 11F–H View FIGURE 11 ) subequal, longer than carapace; ischium distal margin bearing distinct dorsolateral spine and small ventrolateral spine, ventrodistal margin anteriorly produced, with small subterminal spine; merus with short rugae on surfaces, dorsal surface armed with longitudinal row of spines (strongest on distal margin, dorsodistal margin with strong spine mesially, ventrodistal margin with strong mesial and lateral spines; carpus less than half-length of merus, mesial margin with strong subdistal spine and small median spine, dorsolateral margin with strong distal spine, ventrodistal margin produced into triangular lobe; chela 1.3 times as long as merus, twice as longer as broad; palm unarmed; fingers distally spooned and crenulated; occlusal margins sinuous, with low, triangular tooth proximally on fixed finger, and broad, low tooth medially on dactylus; distolateral margin of fixed finger with indistinct denticulate carina.

Pereopods 2–4 ( Figs. 10 View FIGURE 10 , 11J, K View FIGURE 11 ) sparsely setose, generally similar in setation and ornamentation. Pereopod 2 overreaching distal end of cheliped; merus dorsal margin armed with row of spines (distalmost spine prominent), lateral surface with short, sometimes scale-like ridges, ventral margin rugose, with strong distolateral spine; carpus with 4 prominent spines on extensor margin; propodus extensor surface bicarinate, flexor margin rugose, with pair of distal corneous spines; dactylus length approximately half-length of propodus, flexor margin straight, with 11 triangular teeth, becoming obtuse proximally, each with slender spiniform setae diminishing in length proximally. Pereopods 3 and 4 meri shorter than pereopod 2 merus, while carpus to dactylus combined lengths subequal to that of pereopod 2; pereopod 4 merus with row of small spines on dorsal margin; dactyli similar to that of pereopod 3, each with 11 triangular teeth, becoming obtuse proximally.

Epipod present only on pereopod 1.

Colouration in life. Body and appendages white; cornea of eye orange-yellow ( Fig. 10 View FIGURE 10 ).

Distribution. Previously known only from the type locality, Weijia Guyot, North-West Pacific, 1427.5 m deep ( Dong et al. 2019). Our specimen represents the second record of M. spinifrons , slightly extending horizontal and bathymetric ranges.

Habitat. The present specimen was collected from a rock bottom ( Fig. 12 View FIGURE 12 ).

Remarks. The present specimen aligns well with the original description of Munidopsis spinifrons provided by Dong et al. (2019) in all diagnostic aspects. Dong et al. (2019) discussed the differentiating characteristics between M. spinifrons and the closely related M. nitida . Furthermore, the authors indicated that M. spinifrons did not show genetic distinction from M. vrienhoeki based on COI gene sequences, despite the two taxa exhibiting distinct morphological differences. We are in agreement with Dong et al. (2019) regarding the status of M. spinifrons based on our own observations.

This study raises the number of species of Munidopsis to be recorded from waters around Japan and its EEZ to 28 (cf. Komai 2011; Komai et al. 2017; Sato & Aiba 2022).