Torbenella aequabilis, 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 : 122-123

Torbenella aequabilis sp. nov.

urn:lsid:zoobank.org:act:C00CBABF-A072-4153-BF27-A2FEFCDF002C

Fig. 2

Torbenella aff. calvata 2 – Machordom et al. 2022: table 2.

Etymology

From the Latin ‘ aequabilis ’, ‘equal’, in reference to the similar morphology to Torbenella crateris sp. nov.

Material examined

Holotype NEW CALEDONIA • ♀ (6.6 mm); KANACONO stn DW4785; 22°48′ S, 167°41′ E; 388–403 m depth; 29 Aug. 2016; GenBank no.: COI: OP215687 , 16S: OP196026 , PEPCK: OP252561 ; MNHNIU-2017-8750 .

Paratype NEW CALEDONIA • ♀ (6.8 mm); same collection data as for holotype; MNHN-IU-2014-13980 .

Description

CARAPACE. As long as wide. Transverse ridges usually interrupted, except several on gastric region and posterior part of carapace, with dense very short setae. Scales and secondary striae absent between main striae. Gastric region with 2 main epigastric spines, each behind supraocular spine; 4–6 additional minute spines on each side and 2–3 between median spines; several small spines at base of rostrum and in parahepatic, hepatic and anterior branchial regions; one small postcervical spine on each side. Orbit with lateral limit slightly defined. Frontal margins concave. Lateral margins slightly convex. Anterolateral spine well developed, at anterolateral angle, barely reaching level of sinus between rostrum and supraocular spines. One or 2 very small marginal spines anterior to cervical groove. Branchial margins with 4 small spines. Rostrum spiniform, 0.4 times carapace length, not exceeding end of corneae, carinated dorsally, straight, and directed slightly upwards. Supraocular spines not reaching midlength of rostral spine and falling far short of end of corneae, subparallel, directed slightly upwards. THORACIC STERNUM. Smooth, without striae, except a few on sternite 4. Anterior part of sternite 4 slightly narrower than sternite 3; anterior margin widely contiguous to sternite 3. Sternite 3 2.5 times as wide as long; sternite 4 3 times as wide as long, and 2.3 times as wide as sternite 3.

ABDOMEN. Somite 2 unarmed; somites 3–4 with 2 median spines on anterior ridge; posterior ridge of somite 4 with median small spine. Somites 2–3 each with 3 transverse ridges and several scales in addition to anterior ridge. Somite 4 with a few striae.

EYES. Eyes large, maximum corneal diameter half distance between bases of anterolateral spines.

ANTENNULE. Article 1 (distal spines excluded) about one-third carapace length, elongate, slightly exceeding end of corneae, with 2 short distal spines, mesial spine shorter than lateral spine; lateral margin unarmed, bearing numerous long plumose setae.

ANTENNA. Article 1 with prolonged, strong mesial process, slightly exceeding antennular peduncle, lateral border with numerous long plumose setae; article 2 with 2 subequal distal spines, barely reaching end of article 3; article 3 with small distomesial and distolateral spine; ultimate segment unarmed.

MXP3. Ischium about 1.5 times length of merus, distoventrally bearing spine. Merus with well-developed median spine on flexor margin, extensor margin unarmed.

P1. Squamous, with dense short setae on scales, with scattered long setae, length 3.0–3.5 times that of carapace. Merus slightly longer than carpus, armed with some mesial spines, distalmost strongest. Carpus slightly longer than palm, 3 times as long as wide, with several spines along mesial margin. Palm slightly longer than fingers, unarmed. Fingers unarmed, distally curving and crossing, ending in a sharp point.

P2–4. Moderately long and slender, squamous, with dense short setae on scales, with some long iridescent setae along extensor margins of all articles. P2 twice carapace length. Meri successively shorter posteriorly (P3 merus 0.7 length of P2 merus, P4 merus 0.7 times length of P3 merus); P2 merus as long as carapace, 5.5–6.0 times as long as wide, 1.7–1.8 times as long as P2 propodus; P3 merus 4.2–4.5 times as long as wide, 1.5 times as long as than P3 propodus; P4 merus 3.5 times as long as wide, 1.3 times as long as P4 propodus. Extensor margins of meri with row of small, proximally diminishing, spines on P2–3, distal spine only on P4; flexor margins with distal spines followed proximally by several eminences; lateral sides unarmed. Carpi with several spines on extensor margin; flexor margin ending in blunt point. Propodi 4.0–4.5 times as long as wide; extensor margin unarmed; flexor margin with 5–7 slender movable spines, without fixed distal spine. Dactyli slender, length 0.8–0.9 times that of propodi; flexor margin with 2–4 movable spinules along entire length; dactylus 6 times as long as wide.

Genetic data

Sequence data for COI, 16S and PEPCK could be included. The greatest discrimination was shown by COI, with the smallest pairwise sequence divergence of 4.86% between T. aequabilis sp. nov. and T. lupi sp. nov., and the highest (15.42%) between T. aequabilis and T. calvata . Torbenella aequabilis was a sister species of T. orbis (pp = 0.9; Fig. 7 ).

Distribution

New Caledonia, between depths of 388 and 403 m.

Remarks

The new species is morphologically closely related to T. calvata (Macpherson, 2006) and T. crateris sp. nov. from New Caledonia, having the abdominal somite 2 unarmed. Characters distinguishing these species are outlined under the account of T. crateris (see below).

Figures

Fig. 2. Torbenella aequabilis sp. nov., holotype, ♀, CL = 6.6 mm (MNHN-IU-2017-8750), New Caledonia. A. Carapace and abdomen, dorsal view. B. Sternal plastron. C. Cephalic region, showing antennular and antennal peduncles, ventral view. D. Right Mxp3, lateral view. E. Left P1, dorsal view. F. Right P2, lateral view. G. Dactylus of right P2, lateral view. H. Right P3, lateral view. I. Right P4, lateral view. Scale bar: A–B, F, H–I = 1.0 mm; C–D, G = 0.5 mm; E = 2 mm.

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