Trapezionida microtes, Macpherson & Rodríguez-Flores & Machordom, 2024

Macpherson, Enrique, Rodriguez-Flores, Paula C. & Machordom, Annie, 2024, DNA barcoding and morphology revealed the existence of seven new species of squat lobsters in the family Munididae (Decapoda, Galatheoidea) in the southwestern Pacific, ZooKeys 1188, pp. 91-123 : 91

Trapezionida microtes sp. nov.

Fig. 7

Trapezionida pumila : Machordom et al. 2022: table 2, suppl. figs S1-S6 (non T. pumilla Macpherson, 2004).

Material.

Holotype: Vanuatu. Santo Stn AT 9, 17 September 2006, 15°41.5'S, 167°01.3'E, 481 m: ovigerous female, 3.4 mm (MNHN-IU-2017-1337) . Paratypes: Philippines. Musorstom 2 Stn DG 32, 24 November 1980, 13°40'N, 120°54'E, 192-220 m: 1 male, 2.0 mm, 2 ovigerous females, 2.3-2.4 mm, 1 female, 2.1 mm (MNHN-IU-2014-13975) . New Caledonia. Halipro 2 Stn BT 94, 24 November 1996, 23°33'S, 167°42'E, 448-880 m: 1 male, 3.0 mm (MNHN-IU-2014-13978). - Lithist Stn DW 1, 10 August 1999, 23°37.4'S, 167°42.07'E, 440 m: 1 ovigerous female, 3.3 mm (MNHN-IU-2014-13979) .

Description.

Carapace: Slightly longer than broad, with a few scales between main transverse ridges in epigastric and anterior branchial areas. Ridges with very short setae. Gastric region with five pairs of epigastric spines, longest pair behind supraocular spines, one pair between longest pair. One parahepatic spine on each side. Frontal margins transverse. Lateral margins subparallel and convergent posteriorly. First lateral spine at anterolateral angle, well-developed, not reaching level of sinus between rostrum and supraocular spines. Branchial margin with four small spines. Rostrum slightly triangular, ~ 0.5 × length of remaining carapace, slightly upwards directed, dorsally carinated. Supraocular spines short, not reaching midlength of rostrum and clearly not reaching end of cornea, subparallel. Pterygostomian region unarmed, ending in a round tip.

Thoracic sternum: 0.8 × as long as wide. Surface of thoracic sternites IV-VI smooth, only a few short scales on sternite IV. Sternite III 3.5 × as wide as long. Sternite IV trapezoidal, anterior margin contiguous to sternite III along ¾ of its length; 2.5 × as wide as long, and 2.3 × as wide as sternite III.

Pleon: Ridges of pleomeres unarmed; tergites II and III each with one or two uninterrupted transverse ridges on tergite behind anterior ridge: tergites IV and V with anterior ridge only; posteromedian margin of tergite VI straight.

Eye: Ocular peduncle longer than broad, cornea dilated, maximum corneal diameter 0.3 distance between bases of anterolateral spines.

Antennule: Article 1 (distal spines excluded) ~ 0.3 × carapace length, 2.0 × as long as wide (excluding spines), not overreaching end of cornea, with two distal spines, mesial spine shorter than lateral; two spines on lateral margin, proximal one short, located at midlength of segment, distal one long, not reaching end of distolateral spines.

Antenna: Article 1 with short distomesial spine not exceeding end of article 2. Article 2 with distomesial and distolateral subequal spins, not reaching end of article 3. Article 3 with distomesial spine.

Mxp3: Ischium with well-developed spine on flexor distal margin. Merus slightly shorter than ischium; flexor margin with two spines, median slightly stronger than distal spine; extensor margin with minute distal spine. Carpus unarmed.

P1: 2.5 × carapace length, with scattered long setae and some short setae on spines and scales. Merus 0.9 × carapace length, 2.0 × as long as carpus, with some dorsal and mesial spines; distal spines strong, distomesial spine barely reaching proximal fourth of carpus. Carpus as long as palm, 2.0 × as long as broad, with spines along mesial and dorsal sides. Palm 2.0 × as long as broad, with row of minute dorsal spines; one row of spines along mesial and lateral margins. Fingers unarmed, 1.3 × length of palm.

P2-P4: Long and slender, with some short setae and some scattered iridescent setae along extensor margins of all articles. P2 2.2 × carapace length. Meri shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.7 × length of P3 merus); P2 merus 0.9 × carapace length, 6.0 × as long as broad, 1.4 × as long as P2 propodus; P3 merus 5.5 × as long as broad, 1.2 × as long as P3 propodus. Extensor margins of meri with row of 10-12 proximally diminishing spines on P2-P3, only distal spine on P4; flexor margins with three or four spines followed proximally by several eminences on P2-P3, only distal spine on P4; lateral sides unarmed. Carpi with one or two spines on extensor margin; lateral surface with several granules sub-paralleling extensor margin; flexor margin with well-developed distal spine. Propodi 6.0 (P2), 5.5 (P3), 4.2 (P4) × as long as broad; extensor margin unarmed; flexor margin with four or five five slender movable spines, one fixed minute distal spine. Dactyli slender, length 0.6-0.7 that of propodi; flexor margin with eight or nine movable spinules along entire border, with ultimate spinule at base of unguis; P2 dactylus 5.0 × as long as wide. P4 merocarpal articulation reaching anterior end of cervical groove; P4 merus> ½ length of P2 merus.

Genetic data.

COI, 16S.

Etymology.

From the Greek, mikros, small, in reference to the small size of the species.

Remarks.

Trapezionida microtes belongs to the group of species having four spines on the branchial lateral margins of the carapace, rostrum narrowly triangular (not spiniform), short supraocular spines, thoracic sternites smooth, moderately large eyes, pleomere II tergite unarmed, and the distomesial spine of the antennular article 1 smaller than the distolateral spine.

The new species is closely related to T. alonsoi (Macpherson, 1994) from New Caledonia area and T. pumilla (Macpherson, 2004) from Tonga. However, T. microtes is easily distinguished from these species by several characters:

The branchial lateral margin has four spines in the new species, whereas it is armed with five spines (rarely three or four) in T. alonsoi and T. pumilla .

The extensor margin of the Mxp3 merus has a distal spine in T. alonsoi and T. pumilla , whereas it is unarmed in the new species.

The P2-P4 dactyli are clearly more slender in T. microtes than in T. alonsoi : 5.0 × vs. 2.5 × as long as wide.

Genetically T. microtes showed high divergence values with T. alonsoi (6.43% COI, 3.77% 16S). No genetic data is available for T. pumilla .

The new species is also close to T. trigonocornus from Japan ( Komai 2012). However, the dorsal surface of the carapace has branchial dorsal and postcervical spines in T. trigonocornus , whereas these spines are absent in the new species. No genetic data is available for T. trigonocornus .

Distribution.

Vanuatu, New Caledonia, at 192-880 m.

Figures

Figure 7. Trapezionida microtes sp. nov., ovigerous female holotype, 3.4 mm (MNHN-IU- 2017 - 1337), Vanuatu A carapace and pleon, dorsal view B sternal plastron C cephalic region, showing antennular and antennal peduncles, ventral view D right Mxp 3 ischium and merus, lateral view E right P 1, dorsal view F right P 2, lateral view G dactylus of right P 2, lateral view H right P 3, lateral view I right P 4, lateral view. Scale bars: 1.0 mm (A, E, F, H, I); 0.5 mm (B, C, D, G).