Galathea denticulata, Macpherson, Enrique & Cleva, Régis, 2010

Macpherson, Enrique & Cleva, Régis, 2010, Shallow-water squat lobsters (Crustacea, Decapoda, Galatheidae) from Mayotte (Comoros Island), La Réunion and Madagascar, with the description of a new genus and two new species, Zootaxa 2612, pp. 57-68 : 59-61

Galathea denticulata new species

( Figs. 1 , 3 E)

Material examined. Mayotte. Stn 9, ‘S’ pass, 12°51'14.06"S, 45°15'56.05"E, 0–20 m, J.-M. Bouchard, R. Cleva, J. Dumas, V. Dinhut, J. Poupin coll., 0 5 November 2009, seagrass,1 M 2.2 mm, holotype (MNHN- Ga7338). — Stn 14, La Prudente bank, 12°38'50.68"S, 44°58'41.93"E, 15–17 m, J.-M. Bouchard, V. Dinhut, J. Dumas coll., 0 9 November 2009, coral boulders on sand bottom, 1 ov. F 2.3 mm, paratype (MNHN- Ga7339).

Description. Carapace, exclusive of rostrum, 0.9 times as long as broad; dorsal surface nearly horizontal from anterior to posterior; anterior cervical groove indistinct, ridges with dense short setae; 4 ridges on gastric region, anterior 2 (first and second) ridges medially convex anteriorly, first scale-like and placed medially, with 2 epigastric spines, second uninterrupted extending laterally to second lateral spines, third and fourth ridges medially interrupted; mid-transverse ridge uninterrupted, preceded by indistinct cervical groove, followed by 2 interrupted and 2 uninterrupted transverse ridges placed alternately. Lateral margins medially convex, with 8 spines: 2 spines in front of and 6 spines behind indistinct anterior cervical groove; first anterolateral, relatively small, with accompanying small spine on hepatic region; second ventral to between first and third; 3 spines on anterior branchial region, and 3 spines on posterior branchial margin. Lateral orbital angle ending in acute spine; infra-orbital margin with a few obsolescent denticles. Rostrum broad triangular, 1.0–1.2 times as long as broad, length 0.5–0.6 that of breadth 0.4–0.5 that of carapace, dorsal surface concave, with some short setae; lateral margin with 4 small teeth.

Pterygostomian flap rugose with sparse setae, anterior margin acute.

Sternal plastron 0.9 times as long as broad, lateral limits divergent posteriorly. Sternite 3 3.0 times as broad as long, anterior margin slightly convex, with minute median notch. Sternite 4 2.5 times longer and 2.5 times broader than preceding sternite, 0.3 as long as broad; surface with several short transverse ridges bearing short setae. Following sternites smooth.

Abdominal somites 2–4 each with 2 uninterrupted transverse ridges on tergite, with or without interrupted ridge between; somite 5 and 6 each with 1 ridge. Telson 0.6 as long as broad. Two pairs of male gonopods.

Ocular peduncles 1.2–1.3 times longer than broad; eyestalk (other than cornea) with short fine setae on dorsal anterior extension; cornea not dilated.

Basal article of antennular peduncle with well-developed distolateral and distodorsal spines; distomesial spine clearly smaller than others. Ultimate article with a few short setae not in tuft on distodorsal margin.

Article 1 of antennal peduncle hardly visible from dorsal view, with depressed ventral distomesial process not reaching distal margin of article 2. Article 2 with distomesial spine smaller than distolateral, barely reaching midlength of article 3. Articles 3 and 4 unarmed.

Mxp3 basis with some small denticles on mesial ridge. Ischium with small distal spine on flexor margin; extensor margin unarmed; crista dentata with 25 denticles. Merus shorter than ischium, with 2 strong spines of subequal size on flexor margin, proximal one located at midlength, distal one at terminal end; extensor margin unarmed. Carpus spineless.

P1 3.9 (M), 3.0 (F) times postorbital carapace length, relatively slender, subcylindrical, with some short setae on all articles. Merus 1.3 (M), 1.0 (F) times length of carapace, 1.4–1.5 times as long as carpus, with numerous spines, distal ones stronger than others. Carpus 0.9 length of palm, 6.3 (M), 3.0 (F) times longer than broad lateral and mesial margins; dorsal surface with small spines; mesial margin with well-developed spines; row of small spines along lateral margin. Palm 3.2 (M), 3.5 (F) times longer than broad, lateral and mesial margins slightly divergent distally; dorsal surface with small spines; mesial and lateral margins with well-developed spines; dorsolateral row continued on to whole lateral margin of fixed finger; fixed finger with several small dorsomesial spines. Fingers 0.6 (M), 0.7 (F) as long as palm, distally touching each other with 4 intermeshing teeth, when closed.

P2–4 relatively slender, somewhat compressed, sparsely furnished with long setae on all articles. Meri successively shorter posteriorly (P3 merus 0.9 length of P2 merus, P4 merus 0.7 length of P3 merus), equally broad on P2–4; P2 merus 0.9 carapace length, 3.7 times as long as broad, 1.6 times longer than P2 propodus; P3 merus 3.2–3.4 times as long as broad, 1.2 times length of P3 propodus; P4 merus 2.7–3.0 times as long as broad, 1.0–1.1 length of P4 propodus. Dorsal margins with row of small proximally diminishing spines on P2–3, unarmed on P4; dorsolateral surface unarmed on P2–4; ventrolateral margins with well-developed terminal spine on P2–3, unarmed on P4 merus. Carpi with 5 small spines on P2 and unarmed on P3–4; dorsolateral surface rugose; flexor margin with very small distal spine. Propodi subequal in length on P2 and P4, slightly longer on P3, each 4.5–5.0 times as long as broad; extensor margin unarmed; flexor margin with 5 or 6 movable spines, terminal one paired with another smaller spine mesial to it. Dactyli subequal in length, 0.4–0.6 times length of propodi, ending in incurved, strong, sharp spine; flexor margin with prominent triangular terminal tooth preceded by obsolescent 3 or 4 obsolescent teeth, each with seta-like movable spine.

Epipods present on P1 (minute in holotype), absent on P2–3.

Coloration. Base color light orange, anterior part of carapace bluish. P1 light orange, with red and white stripes on distal part of P1 palm. P2–4 propodi and dactyli with transverse red and white stripes.

Etymology. From the Latin denticulatus (with small teeth), in reference to the armature of the rostrum, with small teeth on each lateral margin.

Remarks. The new species belongs to the group of Galathea with laterally uninterrupted stria between the anteriormost branchial marginal spines directly behind the anterior cervical groove, a pair of epigastric spines, the pterygostomian flap without spines on the upper margin, no plumose setae on carapace and abdomen, and epipods only on P1.

Galathea denticulata is closely related to G. amamiensis Miyake & Baba, 1966 (see above). However, the two species can be easily distinguished by the following characters:

1. The lateral margin of the rostrum bears small teeth in G. denticulata , whereas these teeth are clearly stronger in G. amamiensis .

2. The stria between the anteriormost branchial marginal spines directly behind the anterior cervical groove is medially interrupted in G. denticulata , whereas it is uninterrupted in G. amamiensis .

3. The parahepatic spine on each side of the second stria is absent in G. denticulata , whereas it is present in G. amamiensis .

4. The P1 carpus is 3.0–6.0 times longer than broad in the new species, 2.0–2.3 times longer in G. amamiensis .

5. I n G. amamiensis , there is no spine between the anterolateral spine and the end of the anterior cervical groove, and no spine on the hepatic region. Both spines are present in the new species.

Distribution. Only known from Mayotte, at 0–20 m, on coral boulders on sand.

Figures

FIGURE 1. Galathea denticulata new species, holotype, male, 2.2 mm, Mayotte, Stn 9 (MNHN-Ga 7338). A, carapace and abdomen, dorsal view; B, pterygostomian flap, lateral; C, sternal plastron; D, left cephalic region, showing antennular and antennal peduncles, ventral view; E, right Mxp 3, lateral view; F, right P 1, dorsal view; G, right P 2, lateral view; H, right P 3, lateral view; I, right P 4, lateral view. Scale, 1 mm.

FIGURE 3. A, Galathea aegyptiaca Paul’son, 1875, Madagascar, Nosy Be, ov. F 3.6 mm (UF 14013), dorsal view. B, Galathea aegyptiaca Paul’son, 1875, Madagascar, Nosy Be, M 3.0 mm (UF 14576), dorsal view. C, Galathea mauritiana Bouvier, 1914, Madagascar, Nosy Be, ov. F 3.6 mm (UF 14334), dorsal view. D, Galathea mauritiana Bouvier, 1914, Mayotte, ov. F 3.2 mm (MNHN-Ga 7335), dorsal view. E, Galathea denticulata new species, Mayotte, holotype, M 2.2 mm (MNHN-Ga 7338), dorsal view. F, Galathea spinosorostris Dana, 1852, Mayotte, M 3.2 mm (MNHN-Ga 7340), dorsal view. G, Galathea tanegashimae Baba, 1969, Madagascar, Nosy Be, M 3.8 mm (UF 14413), dorsal view. H, Galathea tanegashimae Baba, 1969, Mayotte, ov. F 3.7 mm (MNHN-Ga 7342), dorsal view. I, Galathea ternatensis De Man, 1902, Madagascar, Nosy Be, F 4.0 mm (UF 12554), dorsal view. J, Galathea ternatensis De Man, 1902, Madagascar, Nosy Be, F 3.4 mm (UF 14630), dorsal view. K, Macrothea bouchardi new species, Mayotte, holotype, M 3.5 mm (MNHN-Ga 7350), dorsal view. L, Sadayoshia edwardsii (Miers, 1884), Mayotte, M 4.6 mm (MNHN-Ga 7351). Photographs: Madagascar, G. Paulay; Mayotte, J. Poupin & R. Cleva.