Galathea gibbosa, Macpherson & Rodríguez-Flores & Machordom, 2025

Macpherson, Enrique, Rodríguez-Flores, Paula C. & Machordom, Annie, 2025, New species of Galathea Fabricius, 1793 and Nanogalathea Tirmizi & Javed, 1980 (Crustacea: Decapoda, Galatheidae) from the Western Pacific, Zootaxa 5570 (3), pp. 447-483 : 461-464

Galathea gibbosa sp. nov.

( Fig. 8 )

Galathea villosa Macpherson & Robainas-Barcia, 2015: 315 (in part, only specimen from Vanuatu).

Material examined. Holotype: New Caledonia. SPANBIOS, Stn DW 5230, 18°58.7’S, 163°19.4’E, 21 July 2021, 364– 368 m: ov. F 5.0 mm (MNHN-IU-2021-9124).

Paratypes: New Caledonia. SPANBIOS, Stn CP 5113, 21°10.1’S, 165°51.1’E, 28 June 2021, 260– 260 m: 1 F 6.0 mm (MNHN-IU-2021-5974). — Stn CP 5131, 20°34’S, 164°58.7’E, 01 July 2021, 354– 368 m: 1 M 5.8 mm (MNHN-IU-2021-5996). —Stn CP5132, 20°33.8’S, 164°58.4’E, 01 July 2021, 398– 431 m: 4 ov. F 4.7-6.8 mm (MNHN-IU-2016-9606). —Stn CP5200, 20°48.7’S, 165°26.1’E, 15 July 2021, 306– 452 m: 1 M 4.8 mm (MNHNIU-2021-5972), 1 M 3.4 mm (MNHN-IU-2021-1916). —Stn CP5266, 20°27.9’S, 164°50.1’E, 26 July 2021, 414– 411 m: 1 M 5.2 mm (MNHN-IU-2021-4444). —Stn DR5283, 21°24.5’S, 166°10.2’E, 29 July 2021, 365– 252 m: 1 M 4.3 mm (MNHN-IU-2021-5970).

Vanuatu. MUSORSTOM 8, Stn CP 1087, 15°10.18’S, 167°14.07’E, 6 Octuber 1994, 394– 421 m: 1 ov. F 5.0 mm (MNHN-IU-2013-15935) .

Etymology. From the Latin gibbus, humped, in reference to the hump on the protogastric area.

Description. Carapace: As long as broad; cervical groove distinct, laterally bifurcated; most ridges on gastric region interrupted or scattered scale-like ridges; epigastric region with 10–15 spines; 3–6 small hepatic spines on each side; 1–4 small parahepatic spines on each side lateral to anterior protogastric ridge; anterior protogastric ridge medially convex, with distinct elevation with 2 small median spines and 2–4 long thick iridescent setae; anterior branchial region unarmed; one small postcervical spine on each side, rarely obsolescent. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove, followed by 5–6 ridges. Lateral margins slightly convex medially, with 8 spines: 2 spines in front of and 6 spines behind anterior cervical groove; first anterolateral, well-developed, at level of orbit, second small but distinct, located at midlength between first spine and anterior cervical groove, with 2 spines ventral to between first and second; 3 spines on anterior branchial margin, and 3 spines on posterior branchial margin. Small outer orbital spine; infraorbital margin with strong spine. Rostrum lanceolate, 1.5–1.6 times as long as broad, length 0.5 that of, breadth 0.3 that of carapace; distance between distalmost lateral incisions 0.25 distance between proximalmost lateral incisions; dorsal surface nearly horizontal in lateral view, with some unirramous setae; lateral margin with 4 deeply incised sharp teeth.

Pterygostomian flap rugose, with sparse short setae, anterior margin bluntly angular.

Thoracic sternum: 0.8 × as wide as long. Sternite III with median shallow notch. Sternite IV with anterior part as wide as sternite III, with some short striae. Sternites IV–VI with a few striae. Sternite III ~ 2.3 × as wide as long; sternite IV nearly 2.8 × as wide as long, and 3.0 × as wide as sternite III.

Pleon: Tergites II and III each with 4 transverse uninterrupted ridges, anterior ridge more distinctly elevated than posterior ridge; tergite of somites IV and V with 3 ridges; somite VI with 2 scale-like ridges, posteromedian margin straight. Males with G1 and G2.

Eye: Ocular peduncles 1.5 times longer than broad, maximum corneal diameter 0.5 rostrum width.

Antennule: Article 1 with 2 well-developed distodorsal and distolateral spines, distodorsal larger; distomesial spine minute; 1–2 small spines on lateral margin. Ultimate article with a few long fine setae not in tuft on distodorsal margin.

Antenna: Article 1 with distomesial spine slightly exceeding distal margin of article 2. Article 2 with 2 well-developed subequal distal spines or distolateral spine slightly longer than distomesial and not reaching end of article 3, sometimes 1 additional small mesial spine. Articles 3 and 4 unarmed.

Mxp3: Ischium with well-developed spine on flexor distal margin; crista dentata with 20–21 denticles. Merus shorter than ischium; flexor margin with 2 spines, proximal stronger than distal; extensor margin with 1 well-developed distal spine. Carpus unarmed.

P1: 3.4 (females) to 4.0 times (males) carapace length. Ischium with some ventral spines. Merus 1.3 times length of carapace, 1.5–2.0 times as long as carpus, with spines arranged roughly in rows, dorsomesial spines stronger; distal spines prominent. Carpus 0.7–0.8 length of palm, 2.7–3.5 times as long as broad; dorsal surface with small spines arranged roughly in longitudinal rows; mesial row of well-developed spines. Palm 2.8–3.3 times longer than broad, lateral and mesial margins with small spines arranged roughly in dorsolateral and dorsomesial rows, some small spines scattered on dorsal side. Fingers 0.7–0.8 length of palm, each finger distally with two rows of teeth, spooned; mesial margin of movable finger and lateral margin of fixed finger unarmed.

P2–4: Moderately long and slender. P2 2.0 times carapace length. Meri successively shorter posteriorly (P3 merus 0.9 length of P2 merus, P4 merus 0.8 length of P3 merus); P2 merus 0.7–0.9 carapace length, 4.0 times as long as broad, 1.2–1.4 times longer than P2 propodus; P3 merus 4.2 times longer than broad, 1.1–1.2 times longer than P3 propodus; P4 merus 3.1 times as long as broad, 1.1 length of P4 propodus. Extensor margins of meri with row of 8–10 proximally diminishing spines on P2–3, 3–5 spines on P4; flexor margins distally ending in strong spine followed proximally by 1–4 small spines and several tubercles or eminences; lateral sides with some minute spines on P2–4. Carpi with 5–8 spines on extensor margin, distalmost longer than distal second; lateral surface with small spines and acute granules sub-paralleling extensor margin on P2–4; flexor distal margin with small spine. Propodi 5.2–6.0 times as long as broad; extensor margin with 5–8 small proximal spines on P2–4, terminal spines paired; flexor margin with 5–7 slender movable spines on P2–4. Dactyli distally ending in well-curved strong spine, length 0.5–0.6 that of propodi; flexor margin with 5–6 proximally diminishing teeth, terminal tooth prominent.

Epipods on P1.

Setae: Three types of setae were observed, (1) short simple iridescent setae, sometimes with minute setules along both sides of first half of shaft, densely located on ridges of carapace and pleon, and scales of P1–4; (2) long thick iridescent plumose setae, with setules along both sides of shaft and reaching nearly to end of shaft, sparsely located on carapace, pleon, and P1–4; (3) long thick iridescent simple setae, sparsely located on carapace, pleon and P1–4.

Genetic data. COI and 16S.

Remarks. Galathea gibbosa sp. nov. belongs to the group of species characterized by the presence of more than 4 epigastric spines and often with spinules on hepatic and branchial regions, the lateral margin of the carapace has one small but distinct spine between the anterolateral spine and the anteriormost branchial marginal spine, and the antennular article 1 has 2 well-developed terminal spines, being the distomesial spine very small or obsolescent, e.g., G. pascualae Macpherson & Robainas-Barcia, 2015 , G. crinita Macpherson & Robainas-Barcia, 2015 , G. pubescens Stimpson, 1858 , G. scolopia Macpherson & Robainas-Barcia, 2015 , G. tagaloa Macpherson & Robainas-Barcia, 2015 from the central and western Pacific, and G. villosa Macpherson & Robainas-Barcia, 2015 from Madagascar and Mozambique.

The morphologically and genetically closest species is G. villosa and both species can be distinguished by the anterior protogastric ridge, with a median prominent convexity with 2 small median spines having some long and thick setae in the new species, whereas this ridge is not prominent, unarmed and without long thick setae in G. villosa . This morphological difference is also distinguishing the new species from G. pascualae and G. tagaloa .

The new species is easily distinguished from G. pubescens and G. crinita by the absence of numerous anterior branchial and postcervical spines, which are present in G. pubescens and G. crinita . Galathea gibbosa is also different from G. scolopia by the shape of the rostrum, extremely narrow in G. scolopia and relatively broad in the new species.

The genetic divergences between G. gibbosa and other related species are, for COI: 3.91%, 7.42%, 7.73%, and 12.56% for G. villosa , G. crinita , G. pubescens , and G. scolopia , respectively. For 16S, we only have reliable data respect to G. crinita (1.02%) and G. scolopia (1.73%).

Distribution. New Caledonia and Vanuatu, 252– 452 m.

Figures

FIGURE 8. Galathea gibbosa sp. nov., holotype, ovigerous female, 5.0 mm, MNHN-IU-2021-9124, New Caledonia. A, Carapace and pleon, dorsal view; B, Sternal plastron, sternites 3 and 4; C, Cephalic region, showing antennular and antennal peduncles, ventral view; D, Right Mxp3, lateral view; E, Right P1, dorsal view; F, Right P2, lateral view; G, Dactylus P2, lateral view; H, Right P3, lateral view; I, Right P4, lateral view. Scale bar: A, E, F, H, I = 1.0 mm; B–D, G = 0.5 mm.