Heteronida ceres, Macpherson & Rodríguez-Flores & Machordom, 2023

Macpherson, Enrique, Rodríguez-Flores, Paula C. & Machordom, Annie, 2023, Integrative approach to describe new species of squat lobsters of the genera Heteronida Baba & de Saint Laurent, 1996 and Torbenella Baba, 2008 (Decapoda, Munididae) from the Southwestern Pacific Ocean, European Journal of Taxonomy 860 (1), pp. 116-140 : 119-122

Heteronida ceres sp. nov.

urn:lsid:zoobank.org:act:A70F2B16-2C5B-47C7-AF0F-C938898D8AA8

Figs 1 , 6A

Heteronida aff. aspinirostris – Machordom et al. 2022: table 2.

Etymology

The name ‘ ceres ’ (Roman goddess of grains and agriculture) refers to the numerous granules covering the carapace, abdomen, and pereopods.

Material examined

Holotype NEW CALEDONIA • ♂ (3.5 mm); EXBODI stn CP3927; 18°36′ S, 164°20′ E; 381 m depth; 26 Sep. 2011; MNHN-IU-2013-1847 .

Paratypes WALLIS AND FUTUNA • 1 ov ♀ (3.1 mm); MUSORSTOM 7 stn DW610; 13°22.5′ S, 176°08.9′ W; 286 m depth; 26 May 1992; MNHN-IU-2017-8968 .

TONGA • 1 ov. ♀ (3.5 mm); BORDAU 2 stn DW1586; 18°34.20′ S, 173°54.93′ W; 400–487 m depth; 13 Jun. 2000; GenBank no.: PEPCK: OP252460 ; MNHN-IU-2013-19955 .

Description

CARAPACE. Slightly longer than wide, greatest width measured behind end of anterior cervical groove; dorsal surface densely granulate. Gastric region with strong median process anteriorly blunted, not produced, height less than one-fifth that of carapace (measured in lateral view between dorsal surface and linea anomurica). Cardiac region with somewhat elevated transverse ridge preceded by distinct cervical groove. One low process on each branchial area, near posterolateral angle. Front margins strongly concave. Anterolateral spines strong, blunt, horizontal, directed straight forward, not reaching anterior margin of rostrum. Lateral branchial margins somewhat convex, convergent behind end of posterior cervical groove, with a few small processes, minute anteriormost process bluntly, produced laterally. Rostrum much wider than long, horizontal, dorsal surface with weak median carina; rostral spine absent or obsolescent. Lateral margins convergent anteriorly, ending in minute or obsolescent supraocular spines; anterior margin transverse.

THORACIC STERNUM. Sternal plastron 0.7 as long as wide, successively broadened posteriorly. Sternite 3 having anterior margin slightly convex, surface depressed medially, width slightly less than half that of sternite 4; anterior margin of sternite 4 contiguous with entire posterior margin of sternite 3, surface depressed medially

ABDOMEN. Abdominal somites 2–3 each with low process flanking median process. Telson subdivided into 7 platelets.

EYES. Cornea strongly dilated, without eyelashes; dorsal surface of peduncle granulate.

ANTENNULE. Antennular article 1 squamate, with 2 distal spines (distolateral larger than distomesial), and 1 minute lateral spine.

ANTENNA. Squamate. Article 1 with stout distomesial process not reaching end of article 2; article 2 elongate, longer than wide, with distomesial and distolateral spines, distomesial larger, not reaching end of article 3; articles 3 and 4 unarmed.

MXP3. Ischium 1.5 times as long as merus, with rounded distal process on each of flexor and extensor margins; merus with strong distal spine on extensor margin, a few acute granules on flexor border.

P1.1.4–1.7 times as long as carapace, squamate, subcylindrical; merus and carpus with small distomesial spine; palm 1.3–1.4 times as long as fingers.

P2–4. Squamate; P2 exceeding P1 carpus. Meri successively shorter posteriorly; extensor margin moderately cristate, with blunt distal spine; flexor margin granulate. Extensor margin of carpi tuberculate, with blunt distal spine. Propodi occasionally somewhat widened distally; flexor margin with movable distal spine; length 0.6 that of merus, as long as or slightly shorter than dactylus on P2, slightly longer than dactylus on P3 and P4. Dactyli slender, somewhat curved; flexor margin with 5–9 minute spines, distal one rather close to tip; extensor margin with plumose setae.

COLOUR. Body and P1–P4 light orange.

Genetic data

Unfortunately, there is no data for the most common and variable markers (COI, 16S). Sequence data was only available for 18S and PEPCK. These genes were almost not variable within the genus Heteronida . The maximum divergence values found were for 18S, but for PEPCK H. ceres sp. nov. did not show any clear divergence when compared to the other species, except for H. clivicola . The new species is different from H. barunae with 1.84% and from H. aspinirostris with 0.15% sequence divergence for 18S, and from H. clivicola up to 0.32% for 18S and 0.17% for PEPCK. In any case, H. ceres sp. nov. forms a well-supported clade (pp = 1) with the other species of the genus Heteronida ( Fig. 7 ).

Remarks

The new species is closely related to H. aspinirostris ( Khodkina, 1981) , but it differs in the following features:

– The dorsal carapace surface is densely granulated in the new species, whereas it is finely granulated, and not densely so in H. aspinirostris .

– The gastric process is low and not anteriorly produced in H. ceres sp. nov., whereas it is prominently high and anteriorly produced in H. aspinirostris .

– The rostral and supraocular spines are obsolescent in the new species, whereas these spines are distinct in H. aspinirostris .

The abdominal processes are stronger in H. aspinirostris than in H. ceres sp. nov.

Distribution

New Caledonia, Wallis and Futuna and Tonga, between depths of 286 and 487 m.

Figures

Fig. 1. Heteronida ceres sp. nov., holotype, ♂, CL = 3.5 mm (MNHN-IU-2013-1847), New Caledonia. A. Carapace and abdomen, dorsal view. B. Carapace and abdomen, lateral view. C. Sternal plastron. D. Cephalic region, showing antennular and antennal peduncles, ventral view. E. Right Mxp3, lateral view.F. Right P1, dorsal view. G. Right P2, lateral view. H. Left P3, lateral view. I. Left P4, lateral view. Scale bar: A–C, F–I = 1.0 mm; D–E = 0.5 mm.

Fig. 6. Dorsal view. Colours in life. A. Heteronida ceres sp. nov., holotype, ♂, CL = 3.5 mm, New Caledonia, EXBODI, stn CP3927. B. Torbenella insolita (Macpherson, 2004), ov. ♀, CL = 7.2 mm, New Caledonia. EXBODI, stn CP3927.

Fig. 7. Bayesian phylogenetic inference based on four concatenated gene fragments (COI, 16S, 18S and PEPCK). Numbers on branches indicated the posterior probability supports.