Galathea sentosa, 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 : 281-283

Galathea sentosa n. sp.

( Fig. 101 )

Material examined. Holotype: Wallis and Futuna. MUSORSTOM 7, Stn CP508, 14°19.5'S, 178°04.5'W, 245–440 m, 11 May 1992: M 4.3 mm (MNHN-IU-2013-8423).

Paratypes: Wallis and Futuna. MUSORSTOM 7, Stn CP505, 14°19.5'S, 178°04.3’W, 245–400 m, 11 May 1992: 2 M 3.5–3.7 mm, 3 ov. F 4.0– 6.3 mm (MNHN-IU-2013-8422).— Stn CP508, 14°19.5'S, 178°04.5'W, 245–440 m, 11 May 1992: 1 ov. F 4.2 mm (MNHN-IU-2013-8424).

Etymology. From the Latin sentis, thorny, in reference to the numerous spines on the carapace dorsal surface

Description. Carapace: 1.2–1.3 times as long as broad; anterior and posterior cervical grooves distinct; dorsal surface with scale-like and interrupted ridges in all regions; mid-transverse ridge scale-like, preceded by distinct cervical groove; transverse groove before cardiac spines; ridges setose and with some scattered long and thick plumose setae. Epigastric region with 6–8 small spines; 2 submedian protogastric spines, and 2 parahepatic spines on each side; 1 or 2 postcervical spines on each side and 4 or 5 cardiac spines placed side by side. Lateral margins slightly convex, with 7 spines: 2 spines in front of and 5 strong spines behind anterior cervical groove; first anterolateral, well-developed, distinctly posterior to level of lateral limit of orbit; second small, situated at midlength between anterolateral spine and anterior cervical groove, accompanying another small spine ventral to between first and second; 2 spines on anterior branchial region, and 3 spines on posterior branchial margin. External limit of orbit rounded; infra-orbital margin with 1 or 2 spines. Rostrum twice longer than broad, length 0.6 that of, breadth 0.3 that of carapace; distance between distalmost lateral incisions 0.3 distance between proximalmost lateral incisions; dorsal surface nearly horizontal in lateral view, with small setiferous ridges; lateral margin with 4 sharp teeth.

Pterygostomian flap rugose with sparse setae, anteriorly rounded; some granules on upper margin near linea anomurica.

Sternum: Plastron 1.2 times as long as broad; sternite 4 wider than following sternites.

Abdomen: Somites 2–4 each with 2 uninterrupted transverse ridges on tergite; somites 5 and 6 each with scalelike ridges; posteriormedian lobe of sominte 6 straight. Males with G1 and G2.

Eyes: Ocular peduncles 1.8 times longer than broad, maximum corneal diameter 0.6 rostrum width.

Antennule: Article 1 with 3 distal spines, 2 well-developed spines, distodorsal larger than others; distomesial spine very small but distinct; additional 2 small spine on lateral margin. Ultimate article with a few short setae not in tuft on distodorsal margin.

Antenna: Article 1 with depressed ventral distomesial process not reaching distal margin of article 2. Article 2 with small distomesial and distolateral spines, not reaching midlength of article 3. Articles 3 and 4 unarmed.

Mxp3: Ischium with spine on extensor and flexor distal margins; crista dentata with 20 or 21 denticles. Merus subequal in length to ischium, with 2 subequal spines on flexor margin; extensor margin with small distal spine. Carpus spineless.

P1: 3.4 times carapace length, with long stiff setae on striae of all articles, and some scattered long and thick plumose setae. Merus 1.5 times length of carapace, twice longer than carpus, with several rows of spines, dorsomesial row with strong spines. Carpus as long as palm, 2.6 times longer than broad, dorsal surface with row of small spines; mesial surface with well-developed spines; and some small spines along lateral margin. Palm 2.8 times longer than broad; small dorsal spines roughly in rows: mesial, dorsal and lateral. Fingers 0.8 as long as palm, each finger distally with two rows of teeth, spooned; fingers unarmed.

P2–4: relatively short, somewhat compressed, setose, sparsely with thick long plumose setae on all articles. Meri successively shorter posteriorly (P3 merus 0.8 length of P2 merus, P4 merus 0.8 length of P3 merus), equally broad on P2–4; P2 merus 0.8 carapace length, 5.0 times as long as broad, 1.5 times longer than P2 propodus; P3 merus 3.8 times as long as broad, 1.2 times length of P3 propodus; P4 merus 3.3 times as long as broad, as long as P4 propodus. Extensor margins of meri with row of 5 or 6 proximally diminishing spines on P2–4; lateral surface with 1–3 small spines on P2–4; ventrolateral margins ending in strong terminal spine proximally followed by smaller spine; flexomesial margin with 2 or 3 spines on P2–4. Carpi each with 4–6 spines on extensor margin on P2–4; lateral surface with row of 2–4 small spines or acute granules paralleling extensor row; flexor distal margins with very small distal spine. Propodi 3.7–4.6 times as long as broad; extensor margin with 1–3 proximal spines on P2–4; flexor margin with 5 or 6 movable spines. Dactyli subequal in length, 0.6–0.7 length of propodi, ending in incurved, strong, sharp spine; flexor margin with 5–7 successively diminishing teeth, terminal tooth prominent.

Epipod present only on P1.

Remarks. Galathea sentosa n. sp. closely resembles G. robusta Baba, 1990 from Madagascar and La Reunion from which it can be distinguished by the following characters:

- In G. sentosa , there are no spines on the metagastric and mesogastric regions of the carapace, whereas in G. robusta , there are two spines on each region.

- The Mxp3 merus has a well-developed extensor distal spine in G. ro b u s t a, rather than unarmed in G. sentosa . - The abdominal somites 2 or 3 each has four transverse ridges in G. robusta , instead of two ridges in G. sentosa .

- The genetic divergence between the two species are 8.5% (COI) ( Tab. 3 ).

Distribution. Wallis and Futuna islands; 245– 440 m.

Figures

FIGURE 101. Galathea sentosa n. sp., holotype, male, 4.3 mm, Wallis and Futuna (MNHN-IU- 2013 - 8423). 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, left 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; E = 2 mm; B – D = 0.5 mm.