Galathea nuda, Macpherson, Enrique & Robainas-Barcia, Aymee, 2015

Macpherson, Enrique & Robainas-Barcia, Aymee, 2015, Species of the genus Galathea Fabricius, 1793 (Crustacea, Decapoda, Galatheidae) from the Indian and Pacific Oceans, with descriptions of 92 new species, Zootaxa 3913 (1), pp. 1-335 : 202-204

Galathea nuda n.sp.

( Fig. 73 )

Material examined. Holotype: French Polynesia. Austral Islands. BENTHAUS, Stn DW1985, 23°26.35'S, 150°44.22'W, 100–107 m, 21 November 2002: ov. F 3.0 mm (MNHN-IU-2013-8329).

Paratypes: French Polynesia. Austral Islands. BENTHAUS, Stn DW1927, 24°39.03'S, 146°01.58'W, 95–105 m, 13 November 2002: 1 M 3.1 mm (MNHN-IU-2013-8328).—Stn DW1947, 23°48.51'S, 147°53.47'W, 120–150 m, 17 November 2002: 1 M 3.9 mm, 1 larvae (MNHN-IU-2013-8330).—Stn DW1985, 23°26.35'S, 150°44.22'W, 100–107 m, 21 November 2002: 1 ov. F 2.7 mm (MNHN-IU-2013-8331), 1 ov. F 2.7 mm (MNHN-IU-2013-8332), 1 F 2.5 mm (MNHN-IU-2013-8333).

New Caledonia. Chesterfield Islands. CHALCAL 84, Stn D3, 21°14.00'S, 162°16.40'E, 120–150 m, 13 July 1984: 1 ov. F 2.7 mm (MNHN-IU-2013-8327).

Etymology. From the Latin, nudus, bare, in reference to the smooth carapace surface.

Description. Carapace: 1.1 times longer than broad. Dorsal surface lacking distinct long transverse ridges, except a few scattered scale-like and short ridges, uninterrupted mid-transverse and posterior ridges. Midtransverse ridge preceded by shallow cervical groove; ridges with numerous short setae, and a few long setae. Epigastric region with 2 or 3 pairs of spines. Anterior branch of cervical groove nearly indistinct. Lateral margins slightly convex medially, with 6 spines: 1 spine in front of and 5 spines behind anterior cervical groove; first anterolateral, well-developed, at level of lateral limit of orbit, with accompanying spine ventral to between first and end of anteriormost spine of branchial margin; 2 spines on anterior branchial region, and 2 or 3 spines on posterior branchial margin, last small. Well-developed spine on lateral limit of orbit; infraorbital margin with strong spine. Rostrum 1.7 as long as broad, length 0.7 postorbital carapace length and breadth 0.4 that of carapace; distance between distalmost lateral incisions 0.25 distance between proximalmost lateral incisions; dorsal surface nearly horizontal in lateral view, slightly concave, with some short setae; lateral margin with 4 deeply incised sharp teeth.

Pterygostomian flap rugose, ridges with short setae, anterior margin ending in acute angle.

Sternum: As long as broad, lateral extremities gently divergent posteriorly.

Abdomen: Somites 2–4 each with 1 anterior uninterrupted transverse ridges on tergite; somites 5 and 6 smooth. Telson completely subdivided, with 7 plates. Males with G1 and G2.

Eyes: Ocular peduncles 1.3 times longer than broad, maximum corneal diameter 0.6 rostrum width.

Antennule: Article 1 with 3 spines; well-developed distodorsal and distolateral spines, distodorsal larger than others. Ultimate article with a few long fine setae not in tuft on distodorsal margin.

Antenna: Article 1 with ventral distomesial spine overreaching distal margin of article 2. Article 2 with 2 welldeveloped distal spines, distolateral spine longer than distomesial and exceeding midlength of article 3. Article 3 with small distomesial spine. Article 4 unarmed.

Mxp3: Ischium with well-developed spine on flexor distal margin; extensor margin ending in acute angle; crista dentata with 19–21 denticles. Merus as long as ischium; flexor margin with 2 subequal spines, proximal longer than distal; extensor margin with small distal spine. Carpus unarmed, with several granules on extensor margin.

P1: 2.6 times carapace length, covered with finely setiferous scales, with scattered long plumose setae. Merus 0.9 times length of carapace, 1.5 times as long as carpus, with spines arranged roughly in rows, dorsomesial spines stronger; distal spines prominent. Carpus 0.9 length of palm, 1.8 times as long as broad; dorsal surface with some small spines; mesial margin with row of well-developed spines. Palm 1.6 times longer than broad, lateral and mesial margins subparallel; a few small spines arranged roughly in dorsolateral and dorsomesial rows, some small spines scattered on dorsal side; dorsolateral spines continuing along fixed finger. Fingers as long as palm, each finger distally with two rows of teeth, spooned; 2 or 3 proximal dorsomesial spines along movable finger.

P2–4: Moderately slender, with setose striae and some long plumose setae. P2 1.8 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 carapace length, 3.6 times as long as broad, 1.7 times longer than P2 propodus; P3 merus 3.3 times longer than broad, 1.4 times longer than P3 propodus; P4 merus 2.9 times as long as broad, 1.1 length of P4 propodus. Extensor margin of P2–3 meri with row of 7 or 8 proximally diminishing spines, and 5 spines on P4; ventral margins distally ending in strong spine followed proximally by several tubercles or eminences; lateral sides unarmed on P2–4. Carpi with 5 or 6 spines on extensor margin on P2–3, unarmed on P4; lateral surface with 2–4 spines or acute granules sub-paralleling extensor margin on P2–4; flexor distal margin ending in acute angle. P2–4 propodi 2.8–3.3 times as long as broad; extensor margin with 3 or 4 proximal spines; flexor margin with 5 or 6 slender movable spines on P2–4. Dactyli distally ending in well-curved strong spine, length 0.8–0.9 that of propodi; flexor margin with 4 or 5 proximally diminishing teeth, terminal one prominent.

Epipods present only on P1.

Remarks. The new species belongs to the group of species with the ridges on the dorsal carapace surface mostly obsolescent. The group contains three species: G. kuboi Miyake & Baba, 1967 from Japan, Philippines, and Indonesia, G. nuda n. sp. and G. setigera n. sp. from Indonesia (see Remarks of G. s e t i g er a).

The genetic divergences with other species are always higher than 12.8% (COI, the closest is G. eulimene n. sp.) and 4.4% (16S rRNA, the closest is G. autahi n. sp.) ( Tab. 2 ).

Distribution. French Polynesia (Austral Islands), Chesterfield Islands; 95– 150 m.

Figures

FIGURE 73. Galathea nuda n. sp., holotype, ovigerous female, 3.0 mm, French Polynesia (MNHN-IU- 2013 - 8329). A, carapace and abdomen, dorsal view; B, sternal plastron; C, left part of cephalothorax, ventral view, showing antennular and antennal peduncles, and anterior part of pterygostomian flap; D, ischium, merus and carpus of right Mxp 3, lateral view; E, right P 1, dorsal view; F, right P 1 fingers, ventral view; G, right P 2, lateral view; H, right P 3, lateral view; I, right P 4, lateral view. Scale: A, E, G, H, I = 1 mm; B – D, F = 0.5 mm.