Galathea dianthus, Macpherson & Rodríguez-Flores & Machordom, 2025

Galathea dianthus sp. nov.

( Fig. 7 View FIGURE 7 )

Material examined. Holotype: New Caledonia. KOUMAC, Stn KB 641, 20°47.9’S, 164°16.4’E, 14/11/19, 36 m: ov. F 2.8 mm (MNHN-IU-2014-20098). GoogleMaps

Paratypes: KOUMAC 2019, Stn KL09, 20°37.3’S, 164°08.3’E, 15/09/2018, 67 m: 1 ov. F 3.6 mm (MNHNIU-2021-4277), 19 M 2.0– 3.5 mm, 8 ov. F 2.5–3.7 mm (MNHN-IU-2014-20100), 4 M 2.2–3.4 mm, 9 ov. F 2.6–3.5 mm, 5 F 2.0– 2.3 mm (MNHN-IU-2021-5813 to 5816, 5819), 1 ov. F 2.2 mm (MNHN-IU-2014-20099). GoogleMaps —Stn KL22, 20°26.8’S, 163°58.3’E, 16/09/2018, 47 m: 1 M 4.0 mm (MNHN-IU-2014-20155), 4 M 3.0– 3.7 mm (MNHN-IU-2021-4291), 1 ov. F 3.0 mm (MNHN-IU-2021-5817). GoogleMaps

Etymology. The name dianthus , pink, refers to the colour of the species. The name is considered as a substantive in apposition.

Description. Carapace: As long as broad; cervical groove distinct, laterally bifurcated. Gastric region with 6 transverse ridges:1 epigastric ridge medially interrupted, unarmed; 2 protogastric ridges, anterior ridge uninterrupted, extending laterally to second lateral spine, convex medially, without parahepatic spine, posterior ridge short with some long thick plumose setae; 1 mesogastric ridge uninterrupted, not extending laterally to anteriormost of branchial marginal spines; 2 metagastric ridges, anterior ridge uninterrupted, sometimes extending laterally to third lateral branchial spine, posterior ridge short. Anterior branchial region with distinct ridges. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove, followed by 5 transverse ridges, 2–3 of them uninterrupted. Lateral margins convex medially, with 8 spines: 2 spines in front of and 6 spines behind anterior cervical groove; first anterolateral, well-developed, at level of lateral limit of orbit; second, small, at midlength between anterolateral spine and anteriormost spine of branchial margin, with accompanying strong spine ventral to between first and second; 3 spines on anterior branchial region, and 3 spines on posterior branchial margin, last small. Small spine at lateral limit of orbit; infraorbital margin with strong spine. Rostrum 1.2–1.3 as long as broad, length 0.5 postorbital carapace length and breadth 0.4 that of carapace; distance between distalmost lateral incisions 0.25 distance between proximalmost lateral incisions; dorsal surface nearly horizontal in lateral view, with numerous setae; lateral margin with 4 deeply incised sharp teeth.

Pterygostomian flap rugose, with spine on anterior ridge, ridges with short setae, anterior margin ending in acute angle.

Thoracic sternum: 0.8 times as long as broad, lateral extremities gently divergent posteriorly. Sternite III with median shallow notch and some small spines on anterior margin. Sternite IV with anterior part as wide as sternite III, with some minute striae. Sternites IV–VI with a few striae on lateral sides. Sternite III ~ 1.9 × as wide as long; sternite IV nearly 3.0 × as wide as long, and 2.8 × as wide as sternite III.

Pleon: Tergites II and III each with 3 transverse ridges on tergite, anterior ridge more distinctly elevated than posterior ridge; tergite of somite V smooth; somite VI with 2 medially interrupted ridges, posteromedian margin straight. Males with G1 and G2.

Eye: Ocular peduncles 1.5 times longer than broad, maximum corneal diameter 0.6 rostrum width.

Antennule: Article 1 with 2 spines; well-developed distodorsal and distolateral spines, distodorsal larger; distomesial spine minute or obsolescent. Ultimate article with a few short fine setae, not in tuft on distodorsal margin.

Antenna: Article 1 with ventral distomesial spine reaching distal margin of article 2. Article 2 with 2 well-developed distal spines, distolateral spine shorter than distomesial and reaching midlength of article 3. Articles 3 and 4 unarmed.

Mxp3: Ischium with well-developed spine on flexor distal margin; extensor margin ending in acute angle; crista dentata with 20–21 denticles. Merus as long as ischium; flexor margin with 2 subequal spines; extensor margin with minute spines. Carpus unarmed.

P1: 2.3–2.6 times carapace length. Merus 0.8 times length of carapace, 1.4–1.6 times as long as carpus, with spines arranged roughly in rows, dorsomesial spines stronger; distal spines prominent. Carpus 0.7–0.9 length of palm, 1.3–1.5 times as long as broad; dorsal surface with some spines; mesial margin with row of well-developed spines. Palm 1.5–1.6 times longer than broad, lateral and mesial margins subparallel; a few small spines arranged roughly in dorsolateral and dorsomesial rows, a few small spines scattered on dorsal side; dorsolateral spines continuing along fixed finger. Fingers 0.7–0.9 length of palm, each finger with two rows of teeth distally spooned; movable finger with 2–3 spines along proximal half of mesial margin.

P2–4: Moderately slender. P2 1.5 times carapace length. Meri successively shorter posteriorly (P3 merus 0.8 length of P2 merus, P4 merus 0.9 length of P3 merus); P2 merus 0.5 carapace length, 3.2 times as long as broad, 1.4 times longer than P2 propodus; P3 merus 2.1 times longer than broad, 1.1 times longer than P3 propodus; P4 merus 2.4 times as long as broad, 0.9 length of P4 propodus. Extensor margin of P2–3 meri with row of 5–7 proximally diminishing spines, and 1–2 spines on P4; ventral margins distally ending in strong spine followed proximally by several tubercles or eminences; lateral sides unarmed on P2–3, with 2–3 small spines on P4. Carpi with 1–3 spines on extensor margin on P2–4; lateral surface with several acute granules sub-paralleling extensor margin; flexor distal margin ending in acute or blunt angle. P2–4 propodi 3.5–4.5 times as long as broad; extensor margin with 0–2 proximal spines; flexor margin with 6–7 slender movable spines on P2–4, terminal spines paired. Dactyli distally ending in well-curved strong spine, length 0.6–0.7 that of propodi; flexor margin with 4–5 proximally diminishing teeth, terminal tooth prominent.

Epipods on P1.

Setae: Four types of setae were observed, (1) short plumose setae, with setules along both sides of shaft, densely located on ridges of carapace and pleon, and scales of P1–4; (2) long thick simple setae, sparsely located on pleon and P1–4; (3) short thick simple setae, sparsely located on pleon and P1–4; (4) long thick plumose setae, with long setules along one side of shaft, sparsely located on P1–4.

Colour in life. Ground colour of carapace and pleon orange or light reddish, with minute red spots, more numerous on the anterior part of carapace and pereiopods. Posterior part of carapace and pleon with some dark spots.

Genetic data. COI and 16S.

Remarks. The morphologically and genetically closest relative of the new species is G. cymothoe Macpherson & Robainas-Barcia, 2015 , from Vanuatu, New Caledonia, and Chesterfield Islands, from which G. dianthus can be distinguished by the following characters:

—The epigastric and parahepatic spines on the carapace are present in G. cymothoe , whereas these spines are absent in the new species.

—The rostrum is narrower in G. cymothoe (nearly 1.8 times longer than broad) than in G. dianthus (1.2 times longer than broad).

—The genetic distances between the two species are 11.64% and 4.73% for COI and 16S, respectively.

Distribution. New Caledonia, 36– 67 m.