Galathea ceti, 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 : 79-81

Galathea ceti n.sp.

( Fig. 23 )

Material examined. Holotype: New Caledonia. Lagon. Stn DW1235, 22°24.08'S, 166°55.44'E, 51 m, 9 March 1993: M 4.0 mm (MNHN-IU-2013-8354).

Paratypes: Papua New Guinea. PAPUA NIUGINI Stn PR42, 05°10.2'S, 145°50.3'E, 0 m, 15 November 2012: 1 F 1.6 mm (MNHN-IU-2013-8368).—Stn PP13, 05°15'S, 145°48'E, 120 m, 30 December 2012: 2 ov. F 3.2–3.3 mm (MNHN-IU-2013-8369).

Etymology. The name Cetus , the sea monster, refers to one of the southern constellations.

Description. Carapace: as long as broad; transverse ridges with dense short setae, and some scattered long plumose setae (more numerous in Papua New Guinea paratypes, than in the holotype); cervical groove distinct, laterally bifurcated. Gastric region with 6 transverse ridges: 1 epigastric ridge with 2 median spines, medially interrupted; 2 protogastric ridges, anterior one medially interrupted, with 1 parahepatic spine on each side, posterior ridge short, with some thick long plumose setae; 1 mesogastric ridge uninterrupted but not extending laterally to anteriormost of branchial marginal spines; 2 metagastric ridges, anterior uninterrupted and extending laterally to anterior branchial ridges, posterior ridge moderately short. Hepatic region with small spine. Anterior branchial region with distinct ridges. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove, followed by 5 ridges. Lateral margins well 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 small spine ventral to between first and second; 2 spines on anterior branchial region, and 3 spines on posterior branchial margin, last small. Small spine on lateral limit of orbit; infraorbital margin with strong spine. Rostrum 1.5 as long as broad, length 0.6 postorbital carapace length and breadth 0.4 that of carapace; distance between distalmost lateral incisions 0.4 distance between proximalmost lateral incisions; dorsal surface nearly horizontal in lateral view, with numerous short unirramous setae; lateral margin with 4 deeply incised sharp teeth.

Pterygostomian flap rugose, unarmed, ridges with short setae, anterior margin acute.

Sternum: 0.9 times as long as broad, lateral extremities gently divergent posteriorly.

Abdomen: Somites 2–3 each with 2 uninterrupted transverse ridges on tergite; somite 4 with posterior ridge medially interrupted; somites 5 and 6 each smooth. 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 distal spines, distodorsal larger, distomesial spine smaller than others. Ultimate article with tuft of setae on distodorsal margin.

Antenna: Article 1 with strong distomesial spine exceeding distal margin of article 2. Article 2 with 2 welldeveloped subequal distal spines, nearly reaching midlength of article 3. Articles 3 and 4 unarmed.

Mxp3: Ischium with flexor and extensor margins ending in acute angle; crista dentata with 17 denticles. Merus as long as ischium; flexor margin with 3 spines, proximal stronger than others; extensor margin with small distal spine.

P1: 2.7 times carapace length, with numerous setiferous scales, and a few scattered long setae. Merus as long as carapace, 1.5 times as long as carpus, with some spines, dorsomesial and distal spines stronger than others. Carpus 0.8 length of palm, 1.5 times as long as broad; dorsal surface with some small spines; mesial margin with 3 spines, second clearly stronger than others. Palm 1.4 times longer than broad, lateral and mesial margins slightly convex; spines arranged roughly in dorsolateral and dorsomesial rows, and some small spines on dorsal side. Fingers 0.8 times palm length, each finger distally with two rows of teeth, spooned; fixed finger with spines along lateral margin; movable finger unarmed.

P2–4 (P2 missing in holotype): moderately long and slender, with some setose striae and sparse long plumose setae. P2 1.7 times carapace length, P3 merus 0.9 length of P2 merus, P4 merus 0.8 length of P3 merus. P2 merus 0.6 carapace length, 3.5 times as long as broad, 1.4 times longer than P2 propodus. Extensor margin with row of 8 proximally diminishing spines on P2–3, unarmed on P4; ventral margins distally ending in spine; lateral sides unarmed on P2–3, with 3 spines on P4. Carpi with 4 spines on extensor margin on P2–3, 1 small distal spine on P4; lateral surface with 3 or 4 spines or acute granules sub-paralleling extensor margin; flexor distal margin acute. Propodi 3.7–4.3 times as long as broad; extensor margin with 2 or 3 minute proximal spines; flexor margin with 4 movable spines. Dactyli distally ending in well-curved strong spine, length 0.6–0.7 that of propodi; flexor margin with 4 proximally diminishing teeth, terminal one prominent.

Epipods absent on pereiopods.

Remarks. Galathea ceti resembles to G. anouchkae n. sp. from New Caledonia, Chesterfield Islands, Vanuatu and Fiji, and G. erythrina n. sp. from the Red Sea. G. ce t i can be distinguished from the other species by the the size of the spines on the flexor margin of the Mxp3 merus, being the proximal spine clearly stronger than the distal spine in G. ceti instead of subequal in the other species.

The genetic divergence with G. anouchkae is 14.1% (COI) and 6.7% (16S rRNA).

Distribution. Papua New Guinea, New Caledonia, 0– 51 m.

Figures

FIGURE 23. Galathea ceti n. sp., holotype, male, 4.0 mm, New Caledonia (MNHN-IU- 2013 - 8354). 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 3, lateral view; G, left P 4, lateral view. Scale: A, F, G = 1 mm; E = 2 mm; B – D = 0.5 mm.