Torbenella crateris, 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 : 125-127

Torbenella crateris sp. nov.

urn:lsid:zoobank.org:act:6CBF6B31-504B-4688-8EAB-E1D94F433791

Fig. 3

Torbenella aff. calvata 1. — Machordom et al. 2022: table 2.

Etymology

The name ‘ crateris ’ refers to one of the southern hemisphere constellations (the Cup).

Material examined

Holotype

NEW CALEDONIA • ov. ♀ (7.2 mm); EXBODI stn CP3927; 18°36′ S, 164°20′ E; 381 m depth; 26 Sep. 2011; MNHN- IU-2013-1858 .

Paratypes

NEW CALEDONIA • 1 ov. ♀ (5.4 mm); EXBODI stn CP3849; 22°03′ S, 168°41′ E; 360–560 m depth; 13 Sep. 2011; MNHN-IU-2011-7609 • 2 ov. ♀♀ (6.7–8.4 mm), 1 ♀ (6.0 mm); EXBODI stn CP3927; 18°36′ S, 164°20′ E; 381 m depth; 26 Sep. 2011; MNHN-IU-2011-7921 • 1 ov. ♀ (8.8 mm); EBISCO stn DW3932; 18°32′ S, 164°21′ E; 500–1100 m depth; 27 Sep. 2011; GenBank no.: COI: OP215686 , 16S: OP196025 , 18S: OP196286 ; MNHN-IU-2011-8600 • 2 ov. ♀♀ (7.2–7.3 mm); SPANBIOS stn DW5247; 18°36.1′ S, 164°24.4′ E; 352–376 m depth; 23 Jul. 2021; MNHN-IU-2021-2960 • 1 ov. ♀ (5.3 mm); SPANBIOS stn DW5264; 20°28.6′ S, 164°49.9′ E; 332–335 m depth; 26 Jul. 2021; MNHN-IU-2020-907 • 1 ♂ (8.6 mm), 1 ♀ (3.5 mm); Chesterfield Islands, KANADEEP stn DW5026; 20º22′ S, 158º40′ E; 360–410 m depth; 21 Sep. 2017; MNHN-IU-2017-8927 , MNHN-IU-2017-2821 • 1 ♀ (3.3 mm); KANADEEP stn DW5037; 19º54′ S, 158º35’′E; 340 m depth; 22 Sep. 2017; MNHNIU-2017-2824 .

Description

CARAPACE. As long as wide. Transverse ridges laterally or medially interrupted, with dense very short setae. Few scales and secondary striae between main striae. Gastric region with 2 main epigastric spines, each behind supraocular spine; 4–6 flanking minute spines and 2–3 small spines 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,nearly reaching level of sinus between rostral and supraocular spines. One very small marginal spine directly anterior to cervical groove. Branchial margins with 4–5 small spines. Rostrum spiniform, 0.4 carapace length, not exceeding end of corneae, carinated dorsally, straight, and slightly upwards directed. Supraocular spines barely reaching midlength of rostral spine and falling 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 2.5–2.7 times as wide as long, and 2.4–2.5 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 spine small, rarely obsolescent. Somites 2–3 each with 1–2 transverse ridges 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 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 and strong mesial process, slightly exceeding antennular peduncle, lateral border with numerous long plumose setae; article 2 with 2 distal spines, distomesial spine longer than distolateral, not reaching end of article 3; article 3 with small distomesial spine, article 4 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 3.5–4.0 times that of carapace. Merus 1.2 times carapace length, slightly longer than carpus, armed with some mesial spines, distalmost strongest. Carpus slightly longer than palm, and 4 times as long as wide, with several spines along mesial margin. Palm 1.2 times as long as 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 2.0–2.5 times carapace length. Meri successively shorter posteriorly (P3 merus times 0.8 length of P2 merus, P4 merus 0.8 times length of P3 merus); P2 merus as long as carapace, 6.0 times as long as wide, 1.7–1.8 times as long as P2 propodus; P3 merus 4.5–5.0 times as long as wide, 1.5 times as long as P3 propodus; P4 merus 4.0 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 distal spine on extensor margin; flexor margin ending in blunt point. Propodi 4.5–5.0 times as long as wide; extensor margin unarmed; flexor margin with 5–6 slender movable spines, without fixed distal spine. Dactyli slender, length 0.8–0.9 times that of propodi; flexor margin with 2 movable spinules on median part; dactylus 7.0 times as long as wide.

Genetic data

sequence data could be generated for COI, the partial ribosomal 16S and 18S genes. Torbenalla crateris sp. nov. is resolved as the sister species of the clade formed by T. aequabilis sp. nov., T. lupi sp. nov., T. orbis , and T. insolita ( Fig. 7 ). High values of COI divergence were found between this new species and the rest of representative of the genus: from 10.46 % respect to T. lupi sp. nov. to 13.27% with respect to T. calvata and T. insolita . The divergence respect to T. aequabilis was slightly smaller (12.29%).

Remarks

The new species is morphologically closely related to T. calvata (Macpherson, 2006) and T. aequabilis sp. nov., having the abdominal somite 2 unarmed. The three species differs from each other in the following aspects:

The anterolateral spine of the carapace falls far short of the sinus between rostral and supraocular spines in T. calvata , whereas these spines are longer and barely reaching the level of this sinus in T. aequabilis and T. crateris .

The posterior ridge of the abdominal somite 4 has a median spine, usually small, rarely obsolescent in T. aequabilis and T. crateris , always absent in T. calvata .

The thoracic sternite 3 is clearly wider in T. calvata than in T. crateris and T. aequabilis (3.5 times vs 2.5 times as wide as long). The anterior margin of sternite 4 is wider than sternite 3 in T. calvata , whereas it is slightly narrower in T. crateris . Furthermore, the sternite 4 is 2.4–2.5 times as wide as sternite 3 in T. aequabilis and T. crateris , whereas it is only twice as wide in T. calvata .

The distolateral spine of the antennal article 2 is very strong, exceeding article 3 in T. calvata , whereas this spine is much smaller and never reaching the end of article 3 in T. aequabilis and T. crateris .

The differences between T. crateris and T. aequabilis are as follows:

The transverse ridges of the carapace are not usually interrupted except several on gastric region and posterior part of carapace in T. aequabilis , whereas all ridges are medially or laterally interrupted in T. crateris .

The abdominal somites 2–3 each bear 3 transverse ridges and several scales in addition to the anterior ridge in T. aequabilis , whereas there are only one or two additional ridges in T. crateris .

The P2–4 dactyli are more elongate in T. crateris (7 times as long as wide) than in T. aequabilis (6 times as long as wide).

Distribution

New Caledonia and Chesterfield Islands, between depths of 340 and 1100 m.

Figures

Fig. 3. Torbenella crateris sp. nov., holotype, ov. ♀, CL = 7.2 mm (MNHN-IU-2013-1858), 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. Right P1, dorsal view. F. Left P2, lateral view. G. Right P3, lateral view. H. Right P4, lateral view. Scale bar: A–B, F–H = 1.0 mm; C–D = 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.