Coralliogalathea alba, 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 : 34-37

Coralliogalathea alba sp. nov.

urn:lsid:zoobank.org:act:DAFE58EC-40BA-41C5-B705-6DF4FD859843

Figs 1 , 2A , 5A

Coralliogalathea joae Rodríguez-Flores et al. 2018: 998 (in part, only Madagascar specimens).

Etymology

From the Latin ‘ albus ’, ‘white’, in reference to the colour pattern of the species.

Material examined

Holotype

SOUTHWESTERN INDIAN OCEAN – Saya de Malha Bank • ♂ (1.7 mm); SAYA stn YS12; 10°37.2′ S, 62°02.8′ E; 27 m depth; 9 Nov. 2022; MNHN-IU-2021-5806.

Paratypes

SOUTHWESTERN INDIAN OCEAN – Saya de Malha Bank • 5 ♂♂ (1.5–2.3 mm), 7 ov. ♀♀ (1.6– 2.2 mm), 2 ♀♀ (1.4–1.7 mm); SAYA stn YS12; 10°37.2′ S, 62°02.8′ E; 27 m; 9 Nov. 2022; MNHN- IU-2022-796 • 2 ov. ♀♀ (2.3–2.6 mm); SAYA stn YS14; 10°12.1′ S, 62°09.1′ E; 24 m depth; 10 Nov. 2022; MNHN-IU-2022-206, MNHN-IU-2022-834 .

Non-type material

SOUTHWESTERN INDIAN OCEAN – Saya de Malha Bank • 3 ♂♂ (1.2–1.7 mm), 1 ov. ♀ (1.7 mm), 3 ♀♀ (1.2–1.4 mm); SAYA stn YR05; 10°37.2′ S, 60°10.3′ E; 39 m depth; 6 Nov. 2022; MNHN- IU-2021-5811, MNHN-IU-2022-753 • 2 ♂♂ (1.4–1.6 mm); SAYA stn YS01; 09°55.5′ S, 60°54.2′ E; 25 m depth; 7 Nov. 2022; MNHN-IU-2022-766 • 1 ♂ (1.6 mm); SAYA stn YR16; 10°12.1′ S, 62°09.1′ E; 24 m depth; 10 Nov. 2022; MNHN-IU-2021-5808 • 1 ov. ♀ (2.2 mm); SAYA stn YB03; 10°12.1′ S, 62°09.1′ E; 27 m depth; 11 Nov. 2022; MNHN-IU-2022-812 • 4 ♀♀ (1.3–1.7 mm); SAYA stn YR26; 16°23.1′ S, 59°38.5′ E; 16 m depth; 19 Nov. 2022; MNHN-IU-2021-5809 • 1 ♂ (1.3 mm); SAYA stn YR28; 16°50′ S, 59°31.3′ E; 17 m depth; 20 Nov. 2022; MNHN-IU-2021-5820 • 1 ov. ♀ (2.8 mm); SAYA stn YR31; 16°36.1′ S, 59°30.4′ E; 30 m depth; 21 Nov. 2022; MNHN-IU-2021-5810 .

Description

CARAPACE. 0.8 times as broad as long; cervical groove shallowly distinct; ridges each with dense short plumose setae and a few long thick and plumose setae; one medially interrupted epigastric ridge; anterior gastric area slightly convex; two protogastric ridges, anterior ridge medially and laterally interrupted, posterior ridge short, arcuate, prominent, with thick plumose setae; one mesogastric ridge, usually medially interrupted, not extending to anteriormost marginal branchial spines; one uninterrupted metagastric ridge not extending to anterior branchial ridges. Anterior branchial region with several short ridges. Mid-transverse ridge uninterrupted, followed by four uninterrupted transverse ridges (including posterior ridge). Lateral margins slightly convex medially, with six spines: one anterolateral spine and five spines on branchial margin; first spine anterolateral, well developed, anterior to level of orbit, located near outer orbital spine; two spines on anterior branchial margin, and three spines on posterior branchial margin. Strong outer orbital spine. Rostrum spatulate, horizontal, 1.2–1.3 times as long as wide, length 0.6 and breadth 0.4 that of carapace; dorsal surface nearly horizontal or slightly concave in lateral view; lateral margin with four incised sharp teeth, basal pair of spines smaller than others; margin between distal two spines, and antepenultimate and penultimate spines slightly convex.

PTERYGOSTOMIAN FLAP. One distinct spine on upper margin near linea anomurica, with sparse short setae; anterior margin acute.

THORACIC STERNUM. Nearly as long as broad; lateral extremities gently divergent posteriorly. Sternite 3 broadly triangular, 1.3–1.4 times as long as wide.

PLEON. Tergites 2–4 each with uninterrupted transverse stria behind anterior ridge; tergites 5 and 6 smooth, posteromedian margin of tergite 6 straight. Ridges each with dense short simple setae.

EYES. Ocular peduncles as long as broad, maximal corneal diameter 0.6 of rostrum width.

ANTENNULE. Article 1 with two well-developed and subequal distodorsal and distolateral spines, distodorsal slightly longer; distomesial spine small.

ANTENNA. Article 1 with strong distomesial spine reaching end of peduncle.

MXP 3. Ischium with minute spine on flexor distal margin; crista dentata with 9 or 10 denticles. Merus as long as ischium; flexor margin with one broad blunt spine; extensor margin with one distal spine. Carpus unarmed.

P1. Each article with both numerous plumose and simple setae. In males 2.5–2.8 and in females 1.6–1.8 times carapace length. Merus 0.8–1.1 length of carapace, 1.5–2.1 times as long as carpus, with some strong dorsal and dorsomesial spines and a few ventromesial spines. Carpus 0.8–1.0 length of palm, 1.3–1.7 times as long as broad; dorsal surface with some small spines; mesial row with two or three strong spines. Palm 1.3–1.5 times as long as broad, with a few spines along lateral, dorsal and mesial margins. Fingers unarmed except for opposed margins, 0.8–1.0 times as long as palm.

P2–4. Moderately short, each article with numerous plumose and simple setae. P2 1.7 times carapace length. Meri successively shorter posteriorly (P3 merus 0.9 length of P2 merus, P4 merus 0.8 length of P3 merus); P2 merus 0.6 carapace length, 2.8 times as long as broad, 1.2 times length of P2 propodus; P3 merus 3.0 times as long as broad, 1.2 times length of P3 propodus; P4 merus 2.6 times as long as broad, 1.4 length of P4 propodus. Extensor margins of meri with row of 4 to 6 proximally diminishing spines on P2–3, 0–1 spine on P4; flexor margins distally ending in small spine followed proximally by several eminences; lateral surface unarmed, with scatered scale-like ridges. Carpi with distal spine on extensor margin, unarmed on P4. P2–4 propodi 3.0–3.8 times as long as broad; extensor margin unarmed; flexor margin with 4–6 slender movable spines. P2–4 dactyli distally ending in well-curved strong spine, length 0.7–0.9 that of propodi; flexor margin with 4 proximally diminishing teeth.

COLOUR. Base colour of carapace, pleon and P1–4 white. P1–4 with some black transverse stripes.

Genetic data

COI (MNHN-IU-2021-5820, GenBank Acc. PV749085).

Remarks

The new species resembles Coralliogalathea joae from western and eastern Australia, and Papua New Guinea and Vanuatu ( Rodríguez-Flores et al. 2018), and C. viridis from Guam ( Rodríguez-Flores et al. 2024) in having four teeth on the lateral margin of the rostrum, instead of three, as seen in the rest of the species in the genus. These three species can be easily distinguished by the following differences:

– The rostrum is as long as wide or longer than wide in C. joae and C. viridis , whereas it is clearly wider than long in the new species.

– The mid-transverse ridge is medially interrupted in C. viridis whereas it is medially uninterrupted in C. joae and the new species.

– The anterior gastric area is nearly horizontal in lateral view in the new species ( Fig. 2A ), whereas it is clearly convex in lateral view in C. joae ( Fig. 2B ). The colour patterns differ in the three species: C. alba sp. nov., base colour of carapace and pleon white, without black spots; P1–4 whitish, with some black transverse stripes. Coralliogalathea viridis , base colour of carapace, pleon and pereopods light green or white, with two symmetrical black round spots behind cervical groove ( Rodríguez-Flores et al. 2024). Coralliogalathea joae , base colour of carapace and pleon brownish with darker brown markings, usually with median large white spot on anterior gastric area; P1–4 whitish to brownish with some black transverse stripes ( Rodríguez-Flores et al. 2018).

– The genetic divergences for the COI gene between C. alba sp. nov. and C. joae and C. viridis are: 9.4% for C. joae and 20.5% for C. viridis . See the sequences of C. joae and C. viridis in Rodríguez-Flores et al. (2018, 2024).

Distribution

Saya de Malha Bank, at depths of 17– 39 m.

Figures

Fig. 1. Coralliogalathea alba sp. nov., holotype, ♂, 1.7 mm (MNHN-IU-2021-5806), Saya de Malha. A. Carapace and abdomen, dorsal view. B. Sternal plastron, anterior sternites. C. Left cephalic region, showing antennular and antennal peduncles, ventral view. D. Right Mxp3, showing ischium and merus, lateral view. E. Right P1, dorsal view. F. Right P2, lateral view. G. Right P3, lateral view. H. Right P4, lateral view. Scale bar: A, E–H = 0.6 mm; B–D = 0.4 mm.

Fig. 2. Carapace, lateral view. A. Coralliogalathea alba sp. nov., holotype, ♂, 1.7 mm (MNHN- IU-2021-5806). B. C. joae Rodríguez-Flores et al., 2018, ov. ♀, 1.9 mm (MNHN-IU-2019-1561). Scale bar: 1 mm.

Fig. 5. Colours in life, dorsal view. A. Coralliogalathea alba sp. nov., paratype, ov. ♀, 2.6 mm (MNHN-IU-2022-206), Saya de Malha. B. Trapezionida pluto sp. nov., paratype, ♀, 4.4 mm (MNHN- IU-2022-331), Saya de Malha.