Galathea senta , 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: 278-280
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Galathea senta n. sp.
Material examined. Holotype: French Polynesia. Society islands. Moorea Island, 17.4764 °S, 149.8327 °W, 4–7 m, 10 November 2008: 1 ov. F 2.5 mm (UF 40284).
Paratypes: French Polynesia. Society islands. Moorea Island, 17.4764 °S, 149.8327 °W, 4–7 m, 10 November 2008: 1 M 2.5 mm, 1 F 2.4 mm (UF 18384), 2 M 2.2–2.8 mm (UF 16370).— Mid N coast, 12 October 2008: 1 M 3.0 mm (UF 15503), 1 M 3.1 mm (UF 15504).— 17.4756 °S, 149.8425 °E, 13–17 m, 5 December 2009: 1 ov. F 2.0 mm (UF 24183).
French Polynesia. Gambier Islands. Terevai Island, 23.1548 °S, 135.0189 °W, 23.2 m, 2 February 2013: 1 ov. F 2.0 mm (UF 35447).
French Polynesia. Austral Islands. Rapa, Stn 19, 27° 37.7 'S, 144 ° 18.7 'W, 3 m, 11 November 2002: 1 M 3.6 mm (MNHN-IU- 2013-15890).— Stn 25, 27° 38.4 'S, 144 ° 18.9 'W, 3 m, 13 November 2002: 1 M 2.9 mm (MNHN-IU- 2013-9736).— Stn 27, 27° 38.7 'S, 144 ° 18.7 'W, 6 m, 14 November 2002: 1 M 2.7 mm (MNHN-IU- 2013- 15892).— Stn 29, 27° 34.3 'S, 144 °21.0'W, 2–4 m, 15 November 2002: 2 M 2.7 –3.0 mm, 1 ov. F 3.0 mm (MNHN- IU- 2013-15891).
Pitcairn Islands. Oeno Atoll, 4 August 2008: 1 ov. F 2.5 mm (UF 5059).
New Caledonia. Lifou Island. LIFOU, Stn 1434, 20° 52.5 'S, 167 °08.1'E, 5–20 m, 6 November 2000: 2 ov. F 3.0– 3.2 mm, 3 F 2.8–3.4 mm (MNHN-IU- 2013-14366), 1 F 3.0 mm (MNHN-IU- 2013-9735).
Vanuatu. SANTO, Stn DB8, 15° 34.6 'S, 167 ° 13.8 'E, 12 m, 12 September 2006: 1 M 3.2 mm, 1 ov. F 3.4 mm (MNHN-IU- 2013-14361). Stn DB71, 15° 21.6 'S, 167 ° 12.5 'E, 7 m, 27 September 2006: 5 M 2.2–2.4 mm, 8 ov. F 2.0– 3.2 mm (MNHN-IU- 2013-14362). Stn VM69, 15° 33.4 'S, 167 ° 16.7 'E, 0–1 m, 18 October 2006: 1 ov. F 3.2 mm (MNHN-IU- 2013-14363).
Etymology. From the Latin sentis, thorn, in reference to the strong spine in the Mxp 3.
Description. Carapace. 0.9 times as long as broad; anterior cervical groove indistinct. Ridges with dense short setae, and a few scattered long and thick setae. Gastric region with 6 ridges: 1 epigastric ridge with 2 median spines, medially interrupted; 1 protogastric ridge convex medially, uninterrupted and extending laterally to first lateral spine; 2 mesogastric ridges, anterior uninterruptedly extending laterally to anteriormost of branchial marginal spines, posterior ridge short and scale-like; 2 metagastric ridges not continuing laterally to anterior branchial region; some additional scales between main ridges. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove, followed by 5 ridges. Lateral margins medially convex, with 8 spines: 2 spines in front of and 6 spines behind indistinct anterior cervical groove; first anterolateral, well-developed, behind level of lateral limit of orbit, second very small; another spine ventral to between first and second spines; 3 spines on anterior branchial region, and 3 spines on posterior branchial margin, last small. External limit of orbit unarmed, with welldeveloped spine between orbit and first anterolateral spine, infra-orbital margin with strong acute process. Rostrum broad triangular, 1.4 times as long as broad, length 0.6–0.7 that of, breadth 0.4–0.5 that of carapace; distance between distalmost lateral incisions 0.25 distance between proximalmost lateral incisions; dorsal surface nearly horizontal in lateral view; lateral margin with 4 sharp teeth.
Pterygostomian flap rugose, with 1 distinct spine on upper margin near linea anomurica, anterior margin ending in well-developed spine.
Sternum: As long as broad, lateral limits divergent posteriorly.
Abdomen: Somites 2–5 each with 2 uninterrupted transverse ridges on tergite, with or without some short scales between; somite 6 each with 2 medially interrupted ridges. Males with G 1 and G 2.
Eyes: Ocular peduncles 1.1 times longer than broad, maximum corneal diameter 0.8 rostrum width. Antennule: Article 1 with 3 well-developed distal spines, distodorsal larger. Ultimate article with a few short setae not in tuft on distodorsal margin.
Antenna: Article 1 with depressed ventral distomesial process slightly exceeding distal margin of article 2. Article 2 with distolateral spine larger than distomesial, nearly reaching end of article 3. Article 3 with distinct distomesial spine. Article 4 unarmed.
Mxp 3: Ischium with well-developed distal spine on flexor margin; extensor margin unarmed; crista dentata with 18–24 denticles. Merus shorter than ischium, with strong proximal spine on flexor margin, located at midlength, and exceeding distal margin of merus; distal spine obsolescent; extensor margin with distal spine. Carpus spineless.
P 1. 2.6–2.8 times carapace length, relatively slender, subcylindrical, with numerous short setae and some long setae on dorsal surface and along lateral and mesial margins of all articles. Merus as long as carapace, 1.7 times as long as carpus, with rows of spines, mesial and distal spines strong. Carpus 0.9 length of palm, 1.3–1.7 times longer than broad, lateral and mesial margins subparallel, dorsal surface with small spines; mesial surface with row of 3 or 4 well-developed spines; and row of small spines along lateral margin. Palm 1.5–1.7 times longer than broad; spines roughly in rows on dorsal, mesial and lateral; lateral row continued on to whole lateral margin of fixed finger; mesial row continuing along mesial margin of movable finger. Fingers 0.8–0.9 as long as palm, each finger distally with two rows of teeth, spooned.
P 2–4: Relatively slender, somewhat compressed, moderately setose, sparsely with long setae on all articles. P 2 2.5 times carapace length. Meri successively shorter posteriorly (P 3 merus 0.8 length of P 2 merus, P 4 merus 0.8 length of P 3 merus), equally broad on P 2–4; P 2 merus 0.9 carapace length, 3.5 times as long as broad, 1.7 times longer than P 2 propodus; P 3 merus 3.0 times as long as broad, 1.5 times length of P 3 propodus; P 4 merus 3.0 times as long as broad, 1.5 length of P 4 propodus. Extensor margins with row of 9 proximally diminishing spines on P 2–3, unarmed on P 4; lateral surface unarmed on P 2–3, row of 4 proximally diminishing spines on P 4; 2 welldeveloped spines on terminal flexolateral margin, sometimes obsolescent in P 4; flexomesial margin with terminal spine on P 2 only. Carpi with 4 or 5 spines on extensor margin; lateral surface with row of 2 or 3 small spines or acute granules paralleling extensor row; flexor distal margin ending in acute angle. Propodi 3.9 (P 2), 3.3 (P 3), 2.7–3.5 (P 4) times as long as broad; extensor margin with 3 proximal spines on P 2–3, unarmed on P 4; flexor margin with 4 slender movable spines on P 2 –3, 3 on P 4; lateral sides unarmed. Dactyli 0.7–0.8 length of propodi, ending in incurved, strong, sharp spine; flexor margin with prominent triangular terminal tooth preceded by obsolescent 4 teeth.
Epipods absent on pereiopods.
Coloration. Ground color of carapace, abdominal somites 2–4 and pereopods light brownish or pale, with darker transverse ridges and numerous darker minute spots. P 1 palm with whitish flecks, without distal black spot. P 2–4 with brownish and whitish bands.
Remarks. The new species resembles G. mauritiana and other species characterized by the pterygostomian flap with one or two spines on the upper margin near the linea anomurica, and an uninterrupted mesogastric ridge between the anteriormost branchial marginal spines ( Galathea aequata n. sp., G. a ci s n. sp. and G. ahyongi n. sp.).
Galathea senta is easily differentiated from these species by the following features:?
The Mxp 3 merus has one strong proximal spine on the flexor margin, not reaching distal margin of the merus in G. mauritiana , G. ahyongi , G. acis and G. aequata , whereas this spine is very long, and clearly exceeds the distal margin in G. senta .
The walking legs (P 2–4) are more slender in t he other species than in G. s e n t a. For instance, the P 2 propodus is 4.0 times longer than broad in G. mauritiana , whereas it is 3.0 times in G. senta .
The color patterns are different in both groups. There is one distinct black spot on the distal part of the P 1 palm in G. mauritiana-G. acis-G. aequata-G. ahyongi , whereas this spot is absent in G. s en t a.
The genetic divergences between G. s e n t a and the other four species are always higher than 16.3 % ( COI,) and 9.8 % (16 S rRNA, only available for G. a c i s) ( Tab. 1).
The specimens collected in Taiwan and identified as G. mauritiana ( Baba et al. 2009) agree quite well with the new species (e.g. the Mxp 3 merus has a strong median spine on the flexor margin, exceeding distal margin of merus, and the distal part of the black spot on the P 1 palm is absent). Therefore, we have considered that this material belongs to G. s en t a.
Distribution. French Polynesia, Gambier, Society and Austral Islands, Pitcairn Island, Taiwan, Vanuatu and New Caledonia; 0– 23 m.
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