Galathea micra, 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 : 193-195

Galathea micra n. sp.

( Fig. 69 )

Material examined. Holotype: New Caledonia. Lagon East. Stn 872, 20°37.1'S, 165°58.10'E, 105 m, 13 January 1987: ov. F 3.7 mm (MNHN-IU-2013-8106).

Paratype: New Caledonia. Lagon East. Stn 830, 20°48.9'S, 165°19.3'E, 105–110 m, 10 January 1987: 1 ov. F 2.5 mm (MNHN-IU-2013-8108).

Etymology. From the Greek mikros, small, in reference to the small size of the species.

Description. Carapace: As long as broad; transverse ridges with numerous short fine setae, without long setae; cervical groove distinct, laterally bifurcated. Gastric region with 8 ridges; 2 epigastric ridges, anterior ridge with 4 median spines, posterior ridge scale-like; 2 protogastric uninterrupted ridges, 1 small parahepatic spine lateral to anterior ridge; 1 mesogastric uninterrupted ridge, not continuing laterally with anterior branchial ridges; 3 metagastric ridges, medially uninterrupted and not continuing laterally with anterior branchial ridges. Hepatic region unarmed. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove, followed by 5 ridges, 2 or 3 uninterrupted. Lateral margins slightly convex medially, with 7 spines: first anterolateral, well-developed, second very small but distinct, located at midlength between first spine and anteriormost spine of branchial margin, without small spine ventral to between first and second; 2 spines on anterior branchial margin, and 3 spines on posterior branchial margin. Small outer orbital spine; infraorbital margin with 1 strong spine. Rostrum triangular, twice as long as broad, length 0.5 that of, breadth 0.3 that of carapace; distance between distalmost lateral incisions 0.3 distance between proximalmost lateral incisions, dorsal surface nearly horizontal in lateral view, with some thick long plumose setae; lateral margin with 4 shallowly incised spines.

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

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

Abdomen: Somites 2–3 each with 3 or 4 uninterrupted transverse ridges on tergite, anterior ridge more elevated than posterior ridge; somite 4 with 4 ridges; somites 5 and 6 each with 2 medially interrupted ridges, posteromedian margin of somite 6 straight.

Eyes: Ocular peduncles 1.5 times longer than broad, maximum corneal diameter 0.8 rostrum width.

Antennule: Article 1 with 3 spines; well-developed distodorsal and distolateral spines, distodorsal larger; distomesial spine small; lateral margin unarmed. Ultimate article nearly 2.5 times longer than broad, with a few short fine setae not in tuft on distodorsal margin.

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

Mxp3: Basis with several denticles on mesial ridge, distalmost larger. Ischium with well-developed spine on flexor distal margin; crista dentata with 24 or 25 denticles. Merus as long as ischium; flexor margin with 2 spines, proximal clearly stronger than distal; extensor margin with small distal spine. Carpus unarmed.

P1: 4.4 times carapace length, with numerous finely setiferous scales, with scattered long thick setae. Merus 1.2 times length of carapace, twice as long as carpus, with spines arranged roughly in rows, dorsomesial and ventromesial spines stronger; distal spines prominent. Carpus 0.7 length of palm, 2.7 times as long as broad; dorsal surface with small spines arranged roughly in longitudinal rows; mesial spines slightly stronger than dorsal spines. Palm 3.8 times longer than broad, lateral and mesial margins with minute spines arranged roughly in dorsolateral and dorsomesial rows, some minute spines scattered on dorsal side. Fingers as long as palm, each finger distally with two rows of teeth, ending in incurved teeth to cross each other when closed, mesial margin of movable finger and lateral margin of fixed finger unarmed.

P2–4: Moderately long and slender, with setose striae and long setae. P2 twice carapace length. Meri successively shorter posteriorly (P3 merus 0.8 length of P2 merus, P4 merus 0.8 length of P3 merus); P2 merus 0.8 carapace length, 6 times as long as broad, 1.3 times longer than P2 propodus; P3 merus 5 times longer than broad, 1.2 times longer than P3 propodus; P4 merus 3.8 times as long as broad, as long as P4 propodus. Extensor margins of P2–3 meri with row of 8–10 proximally diminishing spines, P4 merus with 2–4 minute spines and 2 small dorsal spines; flexor margins distally ending in strong spine followed proximally by 1 or 2 small spines and several tubercles or eminences. P2–3 carpi with 5 small spines on extensor margin, 0–1 on P4; lateral surface with some small spines and acute granules sub-paralleling extensor margin on P2–4; flexor distal margin sometimes with small spine. P2, P3 and P4 propodi 6.5, 6.0 and 5.5 times as long as broad, respectively; extensor margin unarmed; flexor margin with 4 or 5 slender movable spines on P2–4. Dactyli subequal in length, distally ending in wellcurved strong spine, length half of propodi; flexor margin with 4–6 proximally diminishing teeth, terminal one prominent.

Epipods absent on pereiopods.

Remarks. Galathea micra n. sp. is characterized by the presence of one small but distinct spine between the anterolateral spine and the anteriormost branchial marginal spine on the carapace, with more than four epigastric spines, and the antennular basal article with three well-developed terminal spines. The new species resembles G. hydrae n. sp. from Mozambique, from which it can be distinguished by the absence of epipods on P 1–3 in G. micra , whereas these epipods are always present on P 1–3 in G. hydrae .

No genetic data are available for G. m i cr a.

Distribution. New Caledonia, 105– 110 m.

Figures

FIGURE 69. Galathea micra n. sp., holotype, ovigerous female, 3.7 mm, New Caledonia (MNHN-IU- 2013 - 8106). 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, right P 4, lateral view. Scale: A, F – H = 1 mm; E = 2 mm; B – D = 0.5 mm.