Galathea argus, 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 : 46-48

Galathea argus n.sp.

( Fig. 11 )

Galathea balssi . —Poore et al., 2008: 19 (SW Australia, 100–382 m).

Material examined. Holotype: Australia. Western Australia. 20°59.05'S, 114°54.25'E, 100–101 m, 13 December 2005: 1 ov. F 3.7 mm ( J55127 ).

Etymology. From Argo , Jason’s ship; also one of the southern hemisphere constallations.

Description. Carapace: As long as broad; transverse ridges with dense short setae, without long setae; cervical groove distinct, laterally bifurcated into anterior and posterior parts. Gastric region with 9 transverse ridges: 2 epigastric ridges, anterior one medially convex and interrupted, with 3 spines (2 epigastric spines and 1 extra spine lateral to right epigastric spine), posterior ridge interrupted; 2 protogastric ridges, anterior ridge uninterrupted, medially convex, with 1 parahepatic spine on each side, posterior ridge interrupted; 2 mesogastric ridges, anterior ridge uninterrupted but not extending laterally to anteriormost branchial marginal spines, posterior ridge interrupted; 3 metagastric ridges, anterior ridge uninterrupted, continuing laterally to anteriorbranchial ridges, posteriormost ridge short. Each hepatic region with 1 spine. Anterior branchial region with distinct ridges. Midtransverse ridge uninterrupted, preceded by cervical groove, usually followed by 6 ridges, including 2 uninterrupted ridges. Lateral margins slightly convex medially, with 7 (right) or 8 (left) spines: 2 spines in front of and 5 or 6 spines behind anterior cervical groove; first (anterolateral) well-developed, at same level of lateral limit of orbit; second, small, located at midlength between anterolateral spine and anteriormost spine of branchial margin, with additional small spine ventral to between first and second spines; 2 spines on anterior branchial margin, and 3 or 4 spines on posterior branchial margin, last on right side small. Lateral limit of orbit with small spine; infraorbital margin with strong spine. Rostrum 1.9 times as long as broad, length 0.6 of postorbital carapace length and breadth 0.3 of carapace width; distance between distalmost lateral incisions 0.35 of distance between proximalmost lateral incisions; dorsal surface nearly horizontal in lateral view, with numerous small scale-like setose ridges; lateral margin with 4 deeply incised teeth.

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

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

Abdomen: Somites 2–3 each with 4 uninterrupted transverse ridges on tergite; somite 4 with 3 transverse ridges; somites 5 and 6 each with 2 medially interrupted ridges, posteromedian margin of somite 6 slightly convex. Males with G1 and G2.

Eyes: Ocular peduncles 1.4 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 some fine setae, not in tuft, on distodorsal margin.

Antenna: Article 1 with distomesial spine exceeding distal margin of article 2. Article 2 with 2 well-developed distal spines, distolateral spine longer than distomesial, and exceeding midlength of article 3. Article 3 with distomesial spine; article 4 unarmed.

Mxp3: Ischium with flexor margin ending in spine; crista dentata with 20–21 denticles. Merus as long as ischium; flexor margin with 2 subequal spines; extensor margin with 2 small spines. Carpus unarmed.

P1: 3 times carapace length, with numerous setiferous scales, and some scattered long, non-plumose setae. Merus 1.3 times carapace length, 2.7 times as long as carpus, with some spines, dorsomesial and distal spines stronger than others. Carpus 0.7 length of palm, 2.2 times as long as broad; dorsal surface with some small spines; mesial margin with row of spines, distal slightly stronger than others. Palm 3.7 times longer than broad, lateral and mesial margins slightly divergent; small spines arranged in dorsal, dorsolateral and dorsomesial rows. Fingers 0.7 times of palm length, each finger distally with 2 rows of teeth, spooned; lateral margin of fixed finger and mesial margin of movable finger unarmed.

P2–4: long and slender, with some setose striae and some long non-plumose setae. P2 2.1 times carapace length. Meri successively shorter posteriorly (P3 merus 0.9 length of P2 merus, P4 merus 0.7 length of P3 merus); P2 merus 0.8 carapace length, 4.8 times as long as broad, 1.4 times longer than P2 propodus; P3 3.5 times as long as broad, 1.2 times longer than P3 propodus; P4 merus 3 times as long as broad, 0.9 times longer than P4 propodus; extensor margins each with row of 9 proximally diminishing spines in P2–3, 3 spines in P4; ventral margins distally ending in strong spine, lateral sides with 3 small spines in P4. Carpi each with 4 or 5 spines on extensor margin in P2–3, 1 distal spine in P4; lateral surfaces each with 4 or 5 small spines or acute granules sub-paralleling extensor margin; flexor distal margins acute. Propodi 5.3–5.5 times as long as broad; extensor margins unarmed; flexor margins each with 5 or 6 movable spines. Dactyli distally ending in noticeably curved strong spine, 0.6 times as long as propodi; flexor margins each with 6 or 7 proximally diminishing teeth, terminal one prominent.

Epipods absent on pereiopods.

Remarks. Galathea argus most closely resembles G. t a g a ro n. sp. and G. consobrina De Man 1902 (see the differences in Remarks of G. consobrina ). No molecular data are available from G. a rg u s.

Distribution. Western Australia, 100– 101 m.

Figures

FIGURE 11. Galathea argus n. sp., holotype, ovigerous female, 3.7 mm, Western Australia (J 55127). 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, left P 1, dorsal view; F, left P 2, lateral view; G, left P 3, lateral view; H, right P 4, lateral view. Scale: A, E – H = 1 mm; B – D = 0.5 mm.