Galathea eridani, 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 : 104-105

Galathea eridani n. sp.

( Fig. 33 )

Material examined. Holotype: Mozambique. MAINBAZA, Stn DW3168, 26°11.93’S, 35°02.85’E, 87–90 m, 16 April 2009: M 3.8 mm (MNHN-IU-2013-13217).

Paratypes: New Caledonia. Lagon Est, Stn 899, 20°14.2'S, 164°25.15'E, 16 m, 14 January 1987: 1 M 3.0 mm (MNHN-IU-2013-13980).

Etymology. The name Erudanus, the River, refers to one of the southern constellations.

Description. Carapace: As long as broad; transverse ridges with dense very short setae, without long setae; cervical groove distinct, laterally bifurcated. Gastric region with 5 transverse ridges: 1 epigastric ridge medially interrupted, with 2 spines; 2 mesogastric ridges, anterior ridge uninterrupted, not extending laterally to anteriormost branchial spines, posterior one short; 2 metagastric ridges not extending laterally to anterior branchial ridges. Anterior branchial region with distinct ridges. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove, followed by 4 ridges, 1 or 2 of them uninterrupted, shallow groove preceeding posterior uninterrupted ridge. Lateral margins slightly convex, with 8 spines: 2 spines in front of and 6 spines behind anterior cervical groove; first anterolateral, well-developed, at same level of lateral limit of orbit, second small, with spine ventral to between first and second spines; 3 spines on anterior branchial region, and 3 spines on posterior branchial margin, last small. Well-developed spine on lateral limit of orbit; infraorbital margin with strong spine. Rostrum 1.3 as long as broad, length 0.6 postorbital carapace length and breadth 0.4 that of carapace; distance between distalmost lateral incisions 0.3 distance between proximalmost lateral incisions; dorsal surface nearly horizontal in lateral view, with some short setae; lateral margin with 4 deeply incised sharp teeth.

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

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

Abdomen: Somites 2–3 with 2 transverse uninterrupted ridges; somites 4–6 each with uninterrupted anterior ridge and 1 or 2 medially interrupted ridges; posteromedian margin of somite 6 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 distal spines, distodorsal larger, distomesial spine slightly smaller. Ultimate article with a few short fine setae not in tuft on distodorsal margin.

Antenna: Article 1 with ventral distomesial spine reaching distal margin of article 2. Article 2 with 2 subequal distal spines, exceeding midlength of article 3. Article 3 with distomesial spine. Article 4 unarmed.

Mxp3: Ischium with small spine on flexor and extensor distal margins; crista dentata with 20 or 21 denticles. Merus as long as ischium; flexor margin with 2 subequal well-developed spines; extensor margin with 3 spines. Carpus unarmed, rugose along extensor margin.

P1: 3.0 times carapace length, covered with finely setiferous scales, with scattered long non-iridescent setae. Merus 1.2 times length of carapace, 1.5–1.6 times as long as carpus, with spines arranged roughly in rows, dorsomesial spines stronger; distal spines prominent. Carpus as long as palm, 1.8 times as long as broad; dorsal and lateral surfaces with some spines; mesial margin with some spines (distal second strong). Palm 1.8–2.0 times longer than broad, lateral and mesial margins subparallel; spines arranged roughly in dorsolateral and dorsomesial rows; dorsolateral row continuing along entire fixed finger; a few small spines scattered on dorsal side. Fingers 0.8 length of palm, each finger with two rows of teeth, distally spooned; movable finger unarmed.

P2–4: moderately slender, with setose striae and sparse long setae (setae non-iridescent). P2 twice carapace length. Meri successively shorter posteriorly (P3 merus 0.9 length of P3 merus, P4 merus 0.7 length of P2 merus); P2 merus 0.8 carapace length, 3.7 times as long as broad, 1.7 times longer than P2 propodus; P3 merus 3.3 times as long as broad, 1.5 times longer than P3 propodus; P4 merus 2.5 times as long as broad, 1.2 times longer than P2 propodus. Extensor margin of P2–3 meri with row of 9 or 10 proximally diminishing spines, 3 spines on P4; ventral margins distally ending in strong spine followed proximally by 0–1 spines and several eminences; lateral sides with 3 spines on P4. Carpi with 4–6 spines on extensor margin on P2–3, 2 spines on P4; lateral surface with 1–3 small spines or acute granules sub-paralleling extensor margin; flexor distal margin acute. P2–4 propodi 3.5–3.8 times as long as broad; extensor margin with 3-4 proximal spines on P2–4; flexor margin with 4–6 slender movable spines. Dactyli distally ending in well-curved strong spine, length 0.5–0.6 that of propodi; flexor margin with 4 proximally diminishing teeth, terminal one prominent.

Epipods present on P1.

Remarks. The present new species is close to G. atua n. sp. from the French Polynesia but the two can be easily distinguished by the following characters:

- The anterior branchial margin has three spines in G. eridani , instead of two spines in G. a t u a. - The Mxp3 merus has two or three spines on the extensor margin in G. eridani , whereas this margin is unarmed or has at most one distal spine in G. atua .

- The P2–4 propodi are less than 4 times longer than broad in G. eridani , rather than more than 4 times longer than broad in G. a t u a.

The new species is also close to G. m a r i a e n. sp. from the French Polynesia, New Caledonia and Maldive Islands, and G. whiteleggi Grant & McCulloch, 1906 from Australia (see Remarks for these species). The specimens from the two far distant localities are similar, without clear morphological differences. Unfortunately no molecular sequences are available.

Distribution. Mozambique, New Caledonia; 16– 90 m.

Figures

FIGURE 33. Galathea eridani n. sp., holotype, male, 3.8 mm, Mozambique (MNHN-IU- 2013 - 13217). 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, left P 4, lateral view. Scale: A, F – H = 1 mm; E = 2.0 mm; B – D = 0.5 mm.