Galathea imitata, 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 : 143-145

Galathea imitata n. sp.

( Figs 49 , 117 C, D)

Material examined. Holotype: Australia. Western Australia, Ningaloo Reef, 22.7415°S, 113.6836°E, 2–3 m, 15 May 2009: M 3.4 mm (QM W29208).

Paratypes: Australia. Western Australia, Ningaloo Reef, 22.7415°S, 113.6836°E, 2–3 m, 15 May 2009: 1 M 4.0 mm (UF21503); 1 ov. F 3.0 mm (UF21520).— 22.581°S, 113.7618°E, 10 m, 1 May 2009: 1 M 2.3 mm (UF21900); 1 ov. F 3.2 mm (UF21915); 1 M 2.5 mm (UF22012); 1 F 2.2 mm (UF22055).— 22.6232°S, 113.6532°E, 6–7 m, 1 May 2009: 1 M 3.6 mm (UF22483); 8 M 2.0– 3.4 mm, 4 ov. F 2.8–3.7 mm (UF23071).— 22.7691°S, 113.7046°E, 10 m, 1 May 2009: 1 F 1.9 mm (UF22557); 1 M 3.8 mm (UF28002); 1 M 3.3 mm, 1 ov. F 3.5 mm (UF28017).— 22.7415°S, 113.6836°E, 2–3 m, 2 July 2009: 1 ov. F 3.3 mm (UF23442).— 22.7691°S, 113.7046°E, 12 m, 20 May 2010: 1 ov. F 4.2 mm (UF27825); 1 M 3.4 mm (UF27826); 2 M 4.3–4.4 mm, 3 ov. F 3.5–4.3 mm (UF27835); 1 ov. F 4.5 mm (UF27895).— 22.6704°S, 113.6496°E, 2–3 m, 23 May 2010: 2 ov. F 3.2–3.4 mm (UF27729); 1 ov. F 3.2 mm (UF27744).

Etymology. From the Latin, imitatus, copy, mimic, in reference to the similarity with species of the G. aegyptiaca complex.

Description. Carapace: Slightly broader than long; anterior cervical groove indistinct. Five ridges on gastric region: 1 epigastric ridge, medially interrupted, with 2 spines; 1 protogastric ridge strongly convex medially, uninterrupted, with 1 parahepatic spine at each side; 1 mesogastric ridge, uninterruptedly extending laterally to anteriormost of branchial marginal spines; 2 metagastric ridges, anterior ridge uninterrupted and continuing laterally with anterior branchial ridges, posterior uninterrupted. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove. Posterior branchial region with 5 transverse, 3 ridges uninterrupted; second ridge with numerous long median plumose setae. Lateral margins medially convex, with 7 spines: 2 spines in front of, and 5 spines behind, indistinct 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, accompanying another spine ventral to between first and second; 2 spines on anterior branchial region, and 3 spines on posterior branchial margin, last small. External limit of orbit ending in small spine; infra-orbital margin with spine. Rostrum broad triangular, 1.3–1.5 times as long as broad, length 0.5 that of, breadth 0.4 that of carapace; distance between distalmost lateral incisions 0.25 distance between proximalmost lateral incisions dorsal surface nearly horizontal in lateral view, with some thick long plumose setae; lateral margin with 4 sharp spines. Ridges with numerous unirramous setae; some thick long plumose setae more dense on dorsal rostrum surface, between epigastric spines, and on median portion of protogastric.

Pterygostomian flap rugose, anterior margin ending in well-developed spine.

Sternum: As long as broad, lateral limits divergent posteriorly.

Abdomen: Somites 2–4 each with 2 uninterrupted transverse ridges on tergite; somite 5 and 6 each with 2 medially interrupted ridges, posteriormedian 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 well-developed distal spines, distodorsal larger. Ultimate article less than twice longer than broad, with a few short setae not in tuft on distodorsal margin.

Antenna: Article 1 with depressed ventral distomesial process slightly exceeding distal margin of peduncle. Article 2 with distomesial spine as long as distolateral, reaching midlength of article 3. Articles 3 and 4 unarmed.

Mxp3: Ischium with well-developed distal spine on flexor margin; extensor margin unarmed; crista dentata with 21–23 denticles. Merus subequal in length to ischium, with 2 strong spines of subequal size on flexor margin, proximal one located at midlength, distal one at terminal end; extensor margin with small distal spine. Carpus spineless.

P1: 2.4 times carapace length, relatively slender, subcylindrical, with numerous short setae and some scattered long plumose setae on dorsal surface and along lateral and mesial margins of all articles. Merus 0.9 times length of carapace, 1.6 times as long as carpus, with rows of spines, mesial and distal spines strong. Carpus 0.8 length of palm, 1.8 times longer than broad, lateral and mesial margins subparallel, dorsal surface with small spines in longitudinal row; mesial surface with row of well-developed spines; and row of small spines along lateral margin. Palm 2.0–2.2 times longer than broad, lateral and mesial margins slightly divergent; spines roughly in rows on dorsal, mesial and lateral; lateral row continued on to whole lateral margin of fixed finger. Fingers 0.8 as long as palm, each finger distally with two rows of teeth, spooned; mesial margin of movable finger with some spines.

P2–4: Relatively slender, moderately setose, sparsely with long non-plumose and plumose setae on all articles. P2 1.6 times carapace length. P2–3 meri subequal in length, P4 merus 0.8 length of P3 merus. P2 merus 0.6 carapace length, 2.5 times as long as broad, 1.5 times longer than P2 propodus; P3 merus 2.5 times as long as broad, 1.3 times length of P3 propodus; P4 merus 2.4 times as long as broad, 1.3 length of P4 propodus. Extensor margins with row of 8 or 9 proximally diminishing spines on P2–3, only distal spine on P4; lateral surface unarmed on P2–3, row of 2–4 spines on P4; flexolateral and flexomesial margins with strong terminal spine on P2–4; additional flexolateral spine on P2 only. Carpi with 4 or 5 spines on extensor margin; lateral surface with row of 2 or 3 small spines paralleling extensor row; flexor distal margins with small spine. Propodi subequal in length on P3 and P4, slightly shorter on P2, each 3.5–3.8 times as long as broad; extensor margin with 1–3 proximal spines on P2-4; flexor margin with 4 slender movable spine on P2–4; 1 proximal spine on lateral side of P4, unarmed on P2–3. Dactyli subequal in length, 0.6–0.7 length of propodi, ending in incurved, strong, sharp spine; flexor margin with prominent triangular terminal tooth preceded by obsolescent 5 teeth.

Epipods present only on P1.

Coloration. Base color light brown. Rostrum and anterior portion of carapace reddish or light brown. Long plumose setae on carapace reddish, those on abdominal somites whitish. Abdominal somites with some whitish spots. P1 with whitish and brownish bands, base of fingers bluish. P2–4 with with whitish and brownish bands, each merus with orange distal spot.

Remarks. Galathea imitata n. sp. resembles G. aegyptiaca Paul’son, 1875 (see Remarks for G. aegyptiaca ), G. corbariae n. sp. and G. homologa n. sp. G. imitata is easily differentiated from G. c o r b a r i a e and G. homologa by the shape of the P2–3 meri. These meri are 2.5 times longer than broad in G. imitata , instead of being equal or more than 3 times longer than broad in G. corbariae and G. homologa .

The genetic divergences between G. imitata and the other related species are quite large (13.1–16.6% COI, 6.1–7.6% 16S rRNA, see Tab. 1).

Distribution. Western Australia (Ningaloo Reef), 2–10 m, associated with Pocillopora sp.

Figures

FIGURE 49. Galathea imitata n. sp., holotype, male, 3.4 mm, Western Australia (QM W 29208). 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, E – H = 1 mm; B – D = 0.5 mm.

FIGURE 117. Dorsal view. A, Galathea halia n. sp., Vanuatu, ovigerous female 3.2 mm (MNHN-IU- 2013 - 8110). B, Galathea halia n. sp., Vanuatu, ovigerous female 3.2 mm (MNHN-IU- 2013 - 13528). C, Galathea imitata n. sp., Western Australia, ovigerous female 3.2 mm (UF 21915). D, Galathea imitata n. sp., Western Australia, male 3.6 mm (UF 22483). E, Galathea inconspicua Henderson, 1885, Vanuatu, male 5.1 mm (MNHN-IU- 2013 - 8507). F, Galathea inflata Potts, 1915, Papua New Guinea, ovigerous female 6.3 mm (MNHN-IU- 2013 - 509). G, Galathea lemniscata n. sp., New Caledonia, Chesterfield islands, holotype, female 4.8 mm (MNHN-IU- 2013 - 15873). H, Galathea leporis n. sp., Papua New Guinea, male 4.3 mm (MNHN-IU- 2013 - 370). I, Galathea longioculata n. sp., Vanuatu, holotype, female 4.8 mm (MNHN- IU- 2013 - 15979).