Galathea machaera, 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 : 177-179

Galathea machaera n. sp.

( Fig. 63 )

Material examined. Holotype: Wallis and Futuna Islands. MUSORSTOM 7, Stn CP498, 14°18.9'S, 178°03.1'W, 105–160 m, 10 May 1992: ov. F 4.4 mm (MNHN-IU-2013-8437).

Paratypes: Wallis and Futuna Islands. MUSORSTOM 7, Stn CP498, 14°18.9'S, 178°03.1'W, 105–160 m, 10 May 1992: 1 M 5.5 mm, 1 ov. F 4.8 mm (MNHN-IU-2013-8430).

Solomon Islands. SALOMON 1, Stn DW1840, 10°17.0'S, 161°43.0'E, 97–223 m, 6 October 2001: 1 M 3.5 mm (MNHN-IU-2013-8434).

Etymology. From the Latin, machaera , sword, in reference to the shape of the rostrum.

Description. Carapace: as long as broad; ridges with a few short setae, and some long simple setae; cervical groove distinct, laterally bifurcated. No complete, uninterrupted or scale-like ridges on anterior half of carapace. Epigastric spines absent; 3 or 4 small hepatic spines on each side. Anterior branchial region with distinct ridges. Mid-transverse ridge interrupted, preceded by shallow cervical groove, followed by 5 interrupted or scale-like transverse ridges, and 1 uninterrupted ridge anterior to posterior margin; shallow transverse groove before second ridge; 1 postcervical spine on each side. Lateral margins convex medially, with 7 spines: 2 spines in front of, and 5 spines behind, anterior cervical groove; first anterolateral, well-developed, at same level of lateral limit of orbit, second, small, at midlength between anterolateral spine and anteriormost spine of branchial margin, with 1 or 2 spines ventral to between first and second; 2 spines on anterior branchial region, with several small spines ventral to marginal spines, and 3 spines on posterior branchial margin, last small. Small spine on lateral limit of orbit; infraorbital margin with 2 spines. Rostrum 2.6 times longer than broad, length 0.9 postorbital carapace length and 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 median longitudinal groove and numerous unirramous setae; lateral margins straight, with 4 deeply incised sharp teeth; ventral surface with longitudinal carina.

Pterygostomian flap rugose, with 1 spine on anterior portion, ridges with short setae, anterior margin acute.

Sternum: 0.7 times longer than broad, lateral extremities divergent posteriorly.

Abdomen: Somites 2–4 each with 3 or 4 uninterrupted or interrupted transverse ridges on tergite; somites 5 and 6 each with 2 uninterrupted ridges; posteromedian margin of somite 6 slightly convex. 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 long distal spines, distodorsal larger. Ultimate article with a few short fine setae not in tuft on distodorsal margin.

Antenna: Article 1 with strong distomesial spine exceeding distal margin of article 2. Article 2 with 2 welldeveloped distal spines, distolateral spine larger than distomesial spine and nearly reaching end of article 3. Article 3 with small distomesial spine. Article 4 unarmed.

Mxp3: Ischium with flexor and extensor margins ending in strong spine; crista dentata with 8 or 9 strong denticles. Merus as long as ischium, with 2 strong flexor spines and 2 strong extensor spines. Carpus unarmed.

P1: 2.4 times carapace length, with numerous setiferous scales, and a few scattered long setae. Merus 0.9 times carapace length, 2.2 times as long as carpus, with some spines, dorsomesial and distal spines stronger than others. Carpus 0.6 times length of palm, 1.6 times as long as broad; dorsal surface with some small spines; mesial margin with 3 spines, median clearly largest than others. Palm 2.4 times longer than broad, lateral and mesial margins slightly divergent; spines arranged roughly in dorsolateral and dorsomesial rows, and some small spines on dorsal side. Fingers 0.6 times palm length, each finger with one row of teeth, distally not spooned, fixed finger with lateral row of spines, movable finger with mesial row of spines.

P2–4: moderately long and slender, with some setose striae and sparse long simple setae. Meri successively shorter posteriorly (P3 merus 0.8 length of P2 merus, P4 merus 0.8 length of P3 merus). P2 2.0 times carapace length. P2 merus 0.8 carapace length, 5.5 times as long as broad, 1.3 times longer than P2 propodus; P3 merus 4.0 times longer than broad, 1.1 times longer than P3 propodus; P4 merus 3.0 times longer than broad, 0.9–1.0 times longer than P4 propodus. Extensor margin of P2–3 meri with row of 6 or 7 proximally diminishing spines, 3 spines on P4; flexor margin with 5 or 6 proximally diminishing spines on P2–3 and 3 or 4 on P4; lateral sides with 3 or 4 small spines on P2–4. Carpi with 4 or 5 spines on extensor margin on P2–4; lateral surface with 3 or 4 small spines sub-paralleling extensor margin on P2–4; flexor distal margin ending in small spine. P2, P3 and P4 propodi 7.5, 6.0 and 4.5 times, respectively, as long as broad; extensor margin 4 or 5 proximal spines; flexor margin with 7 or 8 slender movable spines. Dactyli distally ending in well-curved strong spine, length 0.5–0.6 that of propodi; flexor margin with 5–7 proximally diminishing teeth, terminal one prominent.

Epipods on P1–3.

Remarks. Galathea macharea n. sp. is most closely related to G. genkai Miyake & Baba, 1964 from Japan to Australia, Red Sea and Madagascar, and G. gladiola n. sp. from Vanuatu, New Caledonia and Chesterfield Islands. These three species are differentiated as follows:

- Galathea genkai has the rostrom being equal to or slightly more than 2.0 times as long as broad, versus more than 2.5 times as long in G. m a c h a e r a and G. gladiola .

- Galathea gladiola has the walking legs being longer and more slender than G. machaera . For example, the P2 is more than twice the carapace length and its merus is more than 6 times longer than broad in G. gladiola , whereas the P2 is less than twice the carapace length and the its merus is less than 6 times longer than broad in G. machaera .

The genetic divergences with G. genkai are 14.9%, (COI) and 9.3%(16S rRNA) ( Tab. 3 ). We have observed some intraspecific divergences between localities. For instance, in G. m a c h a e r a the specimens from the Solomon Islands and Wallis-Futuna have a divergence of 4.4% (COI), that recommend further analyses with additional material. Furthermore, the genetic data of G. genkai are from specimens collected in Madagascar. It would be interesting to compare with material from the type area ( Japan) in order to confirm the existence of one widely distributed species or additional species.

Distribution. Wallis and Futuna Islands, Solomon Islands; 97– 223 m.

Figures

FIGURE 63. Galathea machaera n. sp., holotype, ovigerous female, 4.4 mm, Wallis and Futuna (MNHN-IU- 2013 - 8437). 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.