Galathea acerata, 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 : 20-21

Galathea acerata n. sp.

( Fig. 2 )

Material examined. Holotype: Australia. Western Australia, 19°57'S, 117°42'E, 46 m, 2 June 1983: 1 M 2.6 mm ( NMV J13344 ).

Paratype: Australia. Western Australia, 19°57'S, 117°42'E, 46 m, 2 June 1983: 1 F 2.0 mm ( NMV J6778).

Etymology. From the Latin aceratus, mingled with chaff, in reference to the squamate aspect of the gastric region.

Description. Carapace: As long as broad; cervical groove, laterally bifurcated; ridges on gastric and anterior branchial regions scale-like or concentric arcs, with dense short setae and some scattered long simple setae; 2 epigastric spines present; 1 parahepatic and 1 hepatic spine on each side, 2 protogastric spines; anterior branchial region with 1 spine on each side. Mid-transverse ridge laterally interrupted, preceded by shallow cervical groove. Posterior branchial region with 4 transverse ridges, of which two extending to midline. Lateral margins slightly convex in posterior half, with 8 spines in total 2 spines in front of and 6 spines behind anterior cervical groove; first anterolateral, second small, located at midlength between anterolateral spine and anteriormost spine of branchial margin; 3 spines on anterior branchial margin, and 3 spines on posterior branchial margin; additional spine ventral to between first and second lateral spine. External limit of orbit ending in small spine; infraorbital margin with 1 spine. Rostrum triangular, 1.6 times as long as broad, 0.7 of carapace length and 0.4 of carapace breadth, nearly horizontal in lateral view; distance between distalmost lateral incisions 0.25 of distance between proximalmost lateral incisions; dorsal surface with scattered short setae; lateral margin with 4 deeply incised sharp teeth.

Pterygostomian flap rugose, with sparse short setae, anterior margin blunty angular.

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

Abdomen: Somites 2–4 each with 2 transverse ridges on tergite, anterior ridge more distinctly elevated than posterior ridge; somites 5 and 6 with short scales on each tergite, posteromedian margin of somite 6 slightly produced. Male with G1 and G2.

Eyes: Ocular peduncles 1.3 times longer than broad, maximum corneal diameter 0.7 of rostrum width.

Antennule: Article 1 with 3 well-developed distal spines, distodorsal larger; distomesial spine smaller and more slender than distolateral. Ultimate article with tuft of fine setae 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 small distomesial spine. Article 4 unarmed.

Mxp3: Ischium with well-developed distal spine on flexor margin; extensor margin with small but distinct distal spine; crista dentata with 25 or 26 denticles. Merus subequal in length to ischium; flexor margin with 2 welldeveloped, subequal spines, proximal one located at midlength, distal one at terminal end; extensor margin unarmed or with 2 small spines. Carpus unarmed.

P1: 2.7 times carapace length, with sparse long setae. Merus as long as carapace, 1.7 times as long as carpus, with spines arranged in irregular rows, mesial and distal spines prominent. Carpus 0.9 length of palm, 1.7 times as long as broad; dorsal surface with small spines arranged in irregular longitudinal rows extending onto palm; mesial margin with 3 well-developed spines, distal second largest. Palm 1.8 times longer than broad; spines arranged in irregular rows, dorsolateral row of spines continued onto whole lateral margin of fixed finger. Fingers 1.4 length of palm, each finger bearing 2 rows of teeth, distally spooned; movable finger with spines along mesial margin.

P3–4 (P2 missing): Moderately slender, with long sparse plumose setae. P3 twice carapace length. Meri successively shorter posteriorly (P4 merus 0.8 length of P3 merus); P3 merus 3.1 times longer than broad, 1.3 times longer than P3 propodus; P4 merus 2.7 times as long as broad, 1.2 length of P4 propodus; extensor margins each with row of 10 proximally diminishing spines in P3, 1 in P4; lateral surface with 3 spines in P4; flexor margins distally ending in 1 spine followed proximally by 1 spine and several tubercles or short transverse ridges or low protuberances. Carpi each with 4 spines on extensor margin in P3, unarmed in P4; lateral surfaces each with 4 spines sub-paralleling extensor margin in P3, unarmed in P4; flexor distal margin with distal spine. Propodi 3.7–4.1 times as long as broad; extensor margins unarmed; flexor margins each with 4 or 5 slender movable spines. Dactyli distally ending in well-curved strong spine, 0.6–0.7 length of propodi; flexor margins each with 4 proximally diminishing teeth with corneous spinule or robust setae.

Epipods only on P1.

Remarks. Galathea acerata n. sp. from the Western Australia is closest to G. longimana Paul’son, 1875, from the Red Sea. The two species can be distinguished by the following characters:

- The P1 fingers are clearly longer than the palm in G. acerata , whereas they are shorter than the palm in G. longimana .

- The P2–4 are more slender in G. longimana than in G. acerata . For example, the propodi are ca. 4.0 times longer than broad in G. acerata , whereas ca. 5.0 in G. longimana .

No molecular data are available from the two species. Distribution. Australia, Western Australia, 46 m.

Figures

FIGURE 2. Galathea acerata n. sp., holotype, male, 2.6 mm, Western Australia (J 13344). 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 4, lateral view; H, right P 4 dactylus, lateral view. Scale: A, E – G = 1 mm; B – D, H = 0.5 mm.