Galathea bracteosa, 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 : 67-70

Galathea bracteosa n. sp.

( Fig. 18 )

Material examined. Holotype: French Polynesia. Austral Islands. BENTHAUS, Stn DW1968, 23°22.88'S, 150°43.52'W, 100–120 m, 20 November 2002: 1 M 3.1 mm (MNHN-IU-2013-9720).

Paratypes: French Polynesia. Austral Islands. BENTHAUS, Stn DW1880, 27°54.8'S, 143°29.45'W, 90–94 m, 6 November 2002: 1 ov. F 2.3 mm (MNHN-IU-2013-9723).—Stn DW1888, 27°51.38'S, 143°31.42'W, 100–120 m, 6 November 2002: 2 M 2.1–2.5 mm, 1 F 2.5 mm (MNHN-IU-2013-15884).— Stn DW1894, 27°40.13'S, 144°21.51'W, 100 m, 8 November 2002: 1 M 2.5 mm (MNHN-IU-2013-9724).—Stn DW1968, 23°22.88'S, 150°43.52'W, 100–120 m, 20 November 2002: 3 M 2.5–3.1 mm, 2 ov. F 2.6–3.2 mm, 1 F 1.7 mm (MNHN-IU- 2013-15883); 1 ov. F 2.7 mm (MNHN-IU-2013-9722); 1 M 2.4 mm (MNHN-IU-2013-9905).—Stn DW1985, 23°26.35'S, 150°44.22'W, 100–107 m, 21 November 2002: 1 M 2.4 mm (MNHN-IU-2013-9721), 1 M 2.5 mm (MNHN-IU-2010-9904).—Stn DW1997, 22°29.14'S, 151°22.30'W, 700–1350 m, 23 November 2002: 1 M 2.8 mm, 2 ov. F 2.5–3.0 mm (MNHN-IU-2013-15885).

Etymology. From the Latin bractea, scale, in reference to the numerous scale-like ridges on the carapace.

Description. Carapace: As long as broad; ridges with short fine setae, with a few scattered long plumose setae; cervical groove very shallow, laterally bifurcated into anterior and posterior parts; gastric and anterior branchial regions only with interrupted transverse or scale-like ridges; 2 epigastric spines and 1 small hepatic spine on each side; mid-transverse ridge uninterrupted, followed by 4 transverse ridges, 2 of them uninterrupted. Lateral margins convex medially, with 6 spines: 1 spine in front of and 5 spines behind anterior cervical groove; first (anterolateral) accompanying additional spine ventral to between first and lateral end of anterior cervical groove; 2 spines on anterior branchial margin, and 3 spines on posterior branchial margin. External limit of orbit ending in minute spine; infraorbital margin with 1 spine. Rostrum broadly triangular, 1.6 times as long as broad, length 0.6 of postorbital carapace length and breadth 0.3 of carapace width, nearly horizontal in lateral view; distance between distalmost lateral incisions 0.25 of distance between proximalmost lateral incisions; dorsal surface with some short setae; lateral margin with 4 deeply incised sharp teeth.

Pterygostomian flap rugose, 1 facial spine on anterior part, anterior margin spiniform.

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

Abdomen: Somites 2–4 with 2 transverse ridges, anterior ridge more distinctly elevated than posterior ridge; somite 5 smooth, with 1 anterior ridge; tergite of somite 6 smooth or with some scale-like ridges, posteromedian margin nearly straight. Males with G1 and G2.

Eyes: Ocular peduncles 1.3 times longer than broad, maximum corneal diameter 0.7 rostrum width.

Antennule: Article 1 with 3 well-developed spines, distodorsal larger; distomesial spine slightly smaller than distoventral. Ultimate article with a few short fine setae on distodorsal margin.

Antenna: Article 1 with distomesial spine nearly reaching end of article 2. Article 2 with 2 subequal distal spines, reaching midlength of article 3. Articles 3–4 unarmed.

Mxp3: Ischium with well-developed distal spine on flexor margin; extensor and flexor margins ending in spine; crista dentata with 17–20 denticles. Merus as long as ischium; flexor margin with 2 spines, proximal one located at midlength and larger than distal one; extensor margin with small distal spine. Carpus unarmed.

P1: 3 times carapace length, relatively slender. Merus 1.1 times length of carapace, 1.3 times as long as carpus, with spines arranged in longitudinal rows, distal spines prominent. Carpus 0.9 length of palm, 1.7 times as long as broad; dorsal surface with small spines arranged in longitudinal double row; mesial margin with 3 or 4 strong spines, distal second strongest. Palm 1.6 times longer than broad, lateral and mesial margins subparallel; spines arranged in longitudinal rows; dorsolateral row extending onto nearly tip of fixed finger. Fingers 0.8 length of palm, each finger distally with 2 rows of teeth and spooned; movable finger with row of small mesial spines.

P2–4: moderately slender, with setose striae and sparse long plumose setae. P2 1.8 times carapace length. Meri successively shorter posteriorly (P3 merus 0.8 length of P3 merus, P4 merus 0.8 length of P3 merus); P2 merus 0.7 of carapace length, 4.0 times as long as broad, 1.5 times longer than P2 propodus; extensor margins each with row of 7–9 proximally diminishing spines in P2–3, 1 small distal spine in P4; ventral margins distally ending in strong spine followed proximally by 0–1 spines and several low protuberances, lateral surfaces unarmed. Carpi each with 4 spines on extensor margin in P2; 0–1 spines in P3–4; lateral surfaces each with 2 or 3 spines or acute granules sub-paralleling extensor margin; flexor distal margins acute. Propodi 4.0–4.8 times as long as broad; extensor margin with 3 proximal spines in P2, unarmed in P3–4; flexor margins each with 5 slender movable spines. Dactyli distally ending in noticeably curved strong spine, 0.6 times as long as propodi; flexor margins each with 5 or 6 proximally diminishing teeth, terminal one prominent.

Epipods only on P1.

Remarks. Galathea bracteosa belongs to the group of species with scale-like ridges on the gastric region and without dorsal spines on the anterior branchial regions. The closest relatives are G. bimaculata Miyake & Baba, 1966 from Japan to New Caledonia and Western Australia, G. ploto n. sp. from New Caledonia, and G. p s i l a n. sp. from New Caledonia. G. bracteosa is easily differentiated by the presence of a facial spine on the pterygostomian flap that is always absent in the other species.

The genetic divergences among G. bracteosa with these three species are always higher than 14.2% (COI) and 6.1% (16S rRNA) ( Tab. 3 ).

Distribution. French Polynesia, Austral Islands, 90– 120 m. The specimens from Station DW1997 (700–1350 m) should be considered with caution.

Figures

FIGURE 18. Galathea bracteosa n. sp., holotype, male, 3.1 mm, French Polynesia (MNHN-IU- 2013 - 9720). A, carapace and abdomen, dorsal view; B, thoracic sternites 3 and 4; 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 2, lateral view; G, right P 3, lateral view; H, right P 4, lateral view. Scale: A, E – H = 1 mm; B – D = 0.5 mm.