Goniopugettia tanakae Sakai, 1986

Goniopugettia tanakae Sakai, 1986 View in CoL

( Figures 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

Goniopugettia tanakae Sakai, 1986: 2 View in CoL .— Ng et al. 2017: 144, figs. 1–3.

Material examined. JAMSTEC 106776, 1 male (24.0 × 15.6 mm), R / V Kaimei , KM20-10 C cruise, KM-ROV dive #132, Ritto Seamount, northern West Mariana Ridge, 21°48.72'N, 142°02.68'E, 666 m, staying on a colony of primnoid coral, suction sampler, 8 December 2020 GoogleMaps .

Supplemental description. Carapace ( Fig. 1 View FIGURE 1 ) and cephalic appendages similar to female holotype redescribed by Ng et al. (2017), except for proportionally broader carapace (1.5 times as long as broad). Male chelipeds ( Figs. 1 View FIGURE 1 , 2A–C View FIGURE 2 ) equal in length and similar in shape, almost glabrous. Ischium with lower distal angle produced into small tubercle. Merus trigonal in cross-section with blunt longitudinal ridges, with small tubercle on upper distal end; upper margin with few small blunt tubercles proximally; outer surface with low, obtuse median ridge, slightly rugose; lower outer ridge with 1 blunt tubercle. Carpus short, with 2 blunt crests on dorsal surface; outer surface with low tubercle medially; inner lower margin bluntly ridged. Chela 2.3 times as long as wide, somewhat compressed; lower margin slightly notched at base of fixed finger. Palm subrectangular, 1.3 times as long as wide; upper margin forming blunt ridge over entire length; outer and inner surfaces gently convex, with scattered minute punctae; lower margin rounded; fixed finger not deflexed, slightly sinuous, terminating in subacute tip, occlusal margin with row of small blunt teeth in distal half. Dactylus subequal in length to palm, curved proximally, terminating in bunt tip meeting tip of fixed finger, occlusal margin with row of blunt teeth on distal 0.7 length; wide hiatus between fingers.

Thoracic sternum ( Fig. 3 View FIGURE 3 ) covered with short pubescence. Sternites 1 and 2 completely fused, forming small triangular plate, partially fused with sternite 3 with faint transverse suture. Fused third and fourth sternites with deep depression posteriorly bifurcate into 2 grooves extending nearly to level of anterior end of sterno-pleonal cavity; lateral margins concave at articulation with coxae of chelipeds. Fifth to seven sternites grooved along sutures.

Pleon ( Figs. 2D View FIGURE 2 , 3 View FIGURE 3 ) narrowly triangular, surface covered with dense short pubescence, with 6 free somites + telson, midline of each somite elevated into low protuberance or tubercle. Third and fourth somites trapezoidal. Fifth and sixth somites subrectangular, subequal in length. Telson triangular, subequal in length to somite 6, with almost straight lateral margins.

First gonopod ( Fig. 2E–H View FIGURE 2 ) slightly curved outward; distal part styliform with acutely pointed tip located at distolateral portion. Second gonopod ( Fig. 2I View FIGURE 2 ) short, about a quarter length of G1, tapering to weakly bilobed tip, no distal segment or flagellum.

Colouration in life. Carapace with raised areas pinkish red, non-raised areas paler; chelipeds generally pinkish red, fingers whitish; ambulatory legs pale pinkish brown ( Fig. 1 View FIGURE 1 ).

Genetic data. COI gene: LC856569 View Materials (654 bp); 16S rRNA gene: LC856565 View Materials (557 bp) .

Remarks. The present male specimen agrees well with the female holotype in the characteristic morphology of the carapace (see above). Now male characteristics of the species are clarified (see above supplemental description).

We have generated sequences of the COI and 16S rRNA genes of Goniopugettia tanakae for the first time. In the BLAST search, there were no sequences showing close similarities (>90%) to that of G. tanakae ; the 16S rRNA gene sequence had 95–96% similarity to sequences of Oxypleurodon difficilis ( Guinot & Richer de Forges, 1985) ( MZ424942 View Materials , MZ424943 View Materials , MZ424945 View Materials : Muñoz et al. 2021).

Distribution. Known with certainty from Ritto Seamount, West Mariana Ridge, 666 m deep (this study).