Trapezionida brachytes (Macpherson, 1994)

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 brachytes (Macpherson, 1994)

Fig. 3

Munida brachytes Macpherson 1994: 450, fig. 8. - Baba 2005: 260. - Baba et al. 2008: 89.

Trapezionida aff. apheles : Machordom et al. 2022: table 2, suppl. figs S1-S6.

Material.

Holotype: New Caledonia, Smib 5 Stn 86, 13 September 1989, 22°19.8'S, 168°42.8'E, 320 m: male, 3.7 mm (MNHN Ga 2580).

New Caledonia, Chesterfield Islands . Ebisco Stn CP 2495, 6 October 2005, 24°44.11'S, 159°42.9'E, 217-350 m: 1 male, 4.4 mm (MNHN- IU-2016-5803). - Stn DW 2526, 9 October 2005, 22°47.492'S, 159°22.890'E, 340-355 m: 1 male, 4.4 mm (MNHN-IU-2013-19882). Kanadeep 1 Stn DW 5006, 19 September 2017, 22°07'S, 159°19'E, 340-550 m: 1 ovigerous female, 4.5 mm, 1 female, 4.4 mm (MNHN-IU-2017-2519). - Stn DW 5011, 19 September 2017, 22°13'S, 159°03'E, 320-350 m: 1 male, 5.2 mm (MNHN-IU-2014-13918), 1 female, 3.7 mm (MNHN-IU-2017-2926) .

Diagnosis.

(modified from Macpherson 1994) Carapace slightly longer than broad, with a few secondary striae between main transverse ridges. Gastric region with three or four pairs of epigastric spines. Parahepatic, branchial dorsal and postcervical spines absent. Frontal margins transverse. Lateral margins slightly convex. First lateral spine slightly mesial to anterolateral angle, short, clearly not reaching level of sinus between rostrum and supraocular spines. Branchial margins with five minute spines, posterior spines sometimes obsolescent. Rostrum spiniform. Supraocular spines short, not reaching midlength of rostrum and clearly not reaching end of cornea. Surface of thoracic sternum smooth; sternite IV trapezoidal, anterior margin contiguous to sternite III along ¾ of its length. Pleomere tergites unarmed, tergites II and III each with one transverse ridge on tergite behind anterior ridge. Cornea much wider than peduncle. Antennular article 1 with two well-developed distal spines, distomesial spine as long as or shorter than distolateral. Antennal article 1 with short distomesial spine nearly reaching midlength of article 2; article 2 with distomesial and distolateral spines reaching or nearly reaching end of article 3. Extensor margin of Mxp3 merus unarmed. P1 palm with well-developed spines along lateral and mesial margins continuing along fixed and movable fingers, respectively. Extensor margins of P2-P4 meri unarmed, one distal spine only; flexor margins with some well-developed spines followed proximally by several eminences; P2-P4 dactyli slender, as long as or slightly shorter than propodi; with movable spinules along nearly entire flexor margin, with ultimate spinule near unguis (sometimes lost, as in holotype); P2 dactylus 5.5-6.3 × as long as wide; P4 merus> ½ length of P2 merus.

Genetic data.

COI, 16S.

Remarks.

Trapezionida brachytes was only known by one male collected in New Caledonia. The new material collected in New Caledonia and Chesterfield Islands agree quite well with the holotype, although the distomesial spine of the antennular article 1 is shorter than the distolateral spine (subequal in the holotype). Furthermore, the distalmost movable spinule along the flexor margin of the P2-P4 dactyli can be lost (although the insertion point is always present). Therefore, these characters should be considered with caution because these spines/spinules can be broken or regenerating in some specimens.

Morphologically and genetically the closest species of T. brachytes is T. stia (Macpherson, 1994), also known from New Caledonia and Chesterfield islands.

Trapezionida stia and T. brachytes can be distinguished by the following characters:

Pleomeres III and IV tergites have an additional ridge behind the anterior ridge in T. stia , whereas these additional ridges are absent in the new species.

P2-P4 dactyli are shorter and stouter in T. stia than in T. brachytes . The dactyli are ~ 2/3 the propodi length in T. stia , whereas they are as long as or slightly shorter than propodi in T. brachytes . The P2 dactylus is 6.1-6.3 × as long as wide in the new species, instead of 4 × in T. stia . Finally, the terminal 1/3 of the flexor margin of the dactyli are unarmed in T. stia , whereas there are spines along the entire margin in T. brachytes .

Genetically T. brachytes is different from T. stia (5.96% 16S) and (10.6% COI).

Distribution.

New Caledonia and Chesterfield Islands, between 310 and 550 m.

Figures

Figure 3. Trapezionida brachytes (Macpherson, 1994), female, 3.7 mm (MNHN-IU- 2017 - 2926), New Caledonia 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).