Galathea sayaensis, Macpherson & Machordom, 2025

Macpherson, Enrique & Machordom, Annie, 2025, Squat lobsters (Decapoda: Chirostyloidea and Galatheoidea) from Saya de Malha Bank, SW Indian Ocean, with the descriptions of three new species, European Journal of Taxonomy 1012, pp. 27-48 : 37-40

Galathea sayaensis sp. nov.

urn:lsid:zoobank.org:act:A7D03ED9-1A2E-4708-B688-4EE59FAD87E3

Fig. 3

Etymology

The species is named after the type locality (Saya de Malha Bank).

Material examined

Holotype

SOUTHWESTERN INDIAN OCEAN – Saya de Malha Bank • ♀ (2.4 mm); SAYA stn CP5419; 10°16′ S, 61°47.4′ E; 80 m depth; 10 Nov. 2022; MNHN-IU-2021-5797.

Description

CARAPACE. Slightly longer than broad; anterior and posterior cervical grooves distinct; dorsal surface with scale-like and interrupted ridges in all regions; mid-transverse ridge interrupted medially and laterally, preceded by posterior cervical groove; transverse groove anterior to row of cardiac spines; ridges not densely setose, with short plumose setae and with some long and thick plumose setae on protogastric and cardiac ridges. Epigastric region with 8 small spines; two submedian protogastric spines, two parahepatic spines, one lateral mesogastric and two median metagastric spines on each side; one anterior branchial spine, one postcervical spine on each side of mid-transverse ridge, one or three branchial dorsal spines on each side near branchial margin; seven small median cardiac spines. Lateral margins slightly convex, with seven spines: 2 spines in front of and 5 strong spines behind anterior cervical groove; first anterolateral, well developed, distinctly posterior to level of lateral limit of orbit; second small, situated at midlength between anterolateral spine and anterior cervical groove, accompanying another spine ventral to between first and second; 2 spines on anterior branchial region, and 3 spines on posterior branchial margin. Outer orbital angle rounded; infra-orbital margin with one spine. Rostrum 1.9 times as long as broad, length and breadth 0.6 and 0.4 that of carapace, respectively; distance between distalmost lateral incisions 0.4 that between proximalmost lateral incisions; dorsal surface nearly horizontal in lateral view, with minute setiferous ridges; lateral margin with four sharp teeth and a minute distal tooth.

PTERYGOSTOMIAN FLAP. Rugose with sparse setae, anteriorly rounded; some granules on upper margin near linea anomurica.

THORACIC STERNUM. 1.2 times as long as wide. Sternite 3 with median shallow notch on anterior margin. Sternite 4 nearly as wide as following sternites, with anterior margin slightly wider than sternite 3; surface with some short striae. Sternites 4–6 wih a few striae. Sternite 3 2.1 times as wide as long; sternite 4 nearly 2.1 times as wide as long, and 3.2 times as wide as sternite 3.

PLEON. Tergites 2–4 each with 2 or 3 transverse ridges and, with some additional scales, anterior ridge more distinctly elevated than posterior ridges; tergite of somite 5 with medially interrupted ridge; somite 6 with two scale-like ridges, posteromedian margin straight.

EYE. Ocular peduncles 1.8 times as long as wide, maximum corneal diameter 0.8 rostrum width.

ANTENNULE. Article 1 with 3 distal spines, including 2 well-developed spines laterally, distodorsal spine larger than others, distomesial spine small but distinct; 2 small spines on lateral margin. Ultimate article with a few short setae not in tuft on distodorsal margin.

ANTENNA. Article 1 with distomesial spine reaching distal margin of article 2. Article 2 with subequal small distomesial and distolateral spines, not reaching midlength of article 3. Articles 3 and 4 unarmed.

MXP 3. Ischium with one spine on extensor and flexor distal margins; crista dentata with 15–17 denticles. Merus subequal in length to ischium, with 4 spines on flexor margin, proximal 2 spines larger than remaining spines; extensor margin with small distal spine. Carpus with 3 acute prominences along extensor margin.

P1. 4.5 times carapace length, with scattered long setae and some short setae on spines and scales. Merus 1.7 times carapace length, twice as long as carpus, with rows of mesial, dorsal and lateral spines; distal spines strong, distomesial spine barely reaching proximal fourth of carpus. Carpus 0.8 palm length, 3.6 times as long as broad, with rows of spines along mesial and dorsal surfaces. Palm 4.3 times as long as broad, with rows of mesial, dorsal and lateral spines. Fingers 0.8 lengtht of palm, unarmed except opposed margins. Epipods present.

P2 AND 4 (P3 lost). Slender, somewhat compressed laterally, sparsely setose with some simple setae and some scattered thick long plumose setae on all articles. Meri shorter posteriorly (P4 merus 0.6 length of P2 merus), equally broad; P2 merus 0.9 carapace length, 5.3 times as long as broad, 1.3 times as long as P2 propodus; P4 merus 3.0 times as long as broad, 0.8 length of P4 propodus. Extensor margins of meri with row of 9 proximally diminishing spines on P2 and 5 spines on P4; lateral surface with 2 or 3 small spines; lateroflexor margins each ending in strong terminal spine proximally followed by smaller spines; mesioflexor margin with 4 spines on P2 and unarmed on P4. Carpi each with 3 or 4 spines on extensor margin on P2 and P4; lateral surface with row of small spines or acute granules paralleling extensor row; distoflexor margins each with small distal spine. Propodi 5.5–6.0 times as long as broad; extensor margin with three or four spines on proximal half; flexor margin with five or six movable spines. Dactyli subequal in length, 0.6 length of propodi, each ending in curved, strong, sharp spine; flexor margin with six proximally diminishing teeth, terminal tooth prominent. Epipods absent.

SETAE. Three types of setae were observed on carapace, pleon, and pereopods, (1) moderately short plumose setae, with minute setules along both sides of proximal half of each shaft, not dense, located on ridges of carapace and pleon, and scales of P1–4; (2) long thick plumose setae, with setules along one side of each shaft, distally forming a tuft, sparsely located on carapace, around protogastric and cardiac spines, pleon, and P1–4; (3) long thick simple setae, sparsely located on carapace, pleon and pereopods.

Remarks

The new species belongs to the group of species having the carapace with median protogastric and cardiac spines, and the antennular article 1 with a very small distomesial spine. This group contains five species: G. bicornis Macpherson et al., 2025 , from New Caledonia, G. echinata Macpherson, 2012 , from New Caledonia, G. robusta Baba, 1990 , from Madagascar and La Réunion, G. sentosa Macpherson & Robainas-Barcia, 2015 , from Wallis and Futuna, and the new species. However, only two species have spines on the metagastric región: G. robusta and the new species. Both species can be distinguished by the following characters:

– The metagastric region of the carapace is armed with two median spines in G. robusta , whereas it has four spines in the new species. Furthermore, the branchial region has one–three dorsolateral spines in G. sayaensis sp. nov., whereas these spines are absent in G. robusta .

– The corneae are narrower in G. robusta than in the new species.

– The thoracic sternite 3 is clearly wider than long in the new species, whereas it is slightly longer than wide in G. robusta .

Distribution

Saya de Malha Bank, at a depth of 80 m.

Figures

Fig. 3. Galathea sayaensis sp. nov., holotype, ♀, 2.4 mm (MNHN-IU-2021-5797), Saya de Malha. A. Carapace and abdomen, dorsal view. B. Sternal plastron. C. Left cephalic region, showing antennular and antennal peduncles, ventral view. D. Right Mxp3, showing ischium and merus, lateral view. E. Right P1, merus and carpus, dorsal view. F. Right P1, palm and fingers, dorsal view. G. Right P2, lateral view. H. Right P4, lateral view. Scale bar: A–B, E–H = 0.6 mm; C–D = 0.3 mm.