Trapezionida pulex, 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 pulex sp. nov.

Figs 8 , 9B

Munida leptitis : Macpherson 1996: 394, fig. 14. - Macpherson 1997: 607. - Macpherson 2000: 419. - Macpherson 2004: 263. - Baba 2005: 267 (in part). - Macpherson 2006: 318 (in part). - Baba et al. 2008: 104 (in part). - Macpherson 2013: 301 (in part). - Macpherson et al. 2020: 59. (non M. leptitis Macpherson, 1994).

Trapezionida aff. leptitis1: Machordom et al. 2022: table 2, suppl. figs S1-S6.

Material.

Holotype: New Caledonia, Exbodi Stn DW 3902, 19°53'S, 165°49'E, 410 m, 22 September 2011: male, 5.4 mm (MNHN-IU-2016-5809) . Paratypes: Indonesia, Kei Islands , Karubar Stn DW 02, 22 October 1991, 05°47'S, 132°13'E, 209-240 m: 3 males, 4.8-5.3 mm, 2 females, 3.6-4.3 mm, 1 juv. 2.4 mm (MNHN-IU-2014-14752, MNHN-IU-2016-516). Papua-New Guinea, Biopapua Stn CP3759, 14 October 2010, 03°59.690'S, 153°37.070'E, 287-352 m: 1 ovigerous female, 5.3 mm (MNHN-IU-2011-3829). - Papua Niugini Stn CP4016, 12 December 2012, 05°40'S, 148°14'E, 280-285 m: 1 female, 3.2 mm (MNHN-IU-2016-5816). - Madeep Stn DW4310, 3 May 2014, 09°50'S, 151°31'E, 390-500 m: 1 male, 4.2 mm (MNHN-IU-2016-5804). - Stn DW4311, 3 May 2014, 09°50'S, 151°32'E, 270-486 m: 1 male, 5.7 mm, 1 ovigerous female, 5.2 mm (MNHN-IU-2015-828). - Kavieng 2014 Stn DW4485, 5 September 2014, 02°26'S, 149°54'E, 240-242 m: 1 male, 3.4 mm (MNHN-IU-2014-9905) . Solomon Islands, Salomon 1 Stn CP1831, 05 October 2001, 10°12.1'S, 161°19.2'E, 135-325 m: 1 ovigerous female, 6.0 mm; (MNHN-IU-2016-2997), 3 males, 3.4-5.5 mm, 1 ovigerous female, 3.7 mm, 1 female, 5.0 mm (MNHN-IU-2014-14750) . Vanuatu, Musorstom 8 Stn CP983, 23 September 1994, 19°22'S, 169°28'E, 475-480 m: 1 male, 3.5 mm (MNHN-IU-2016-515) . New Caledonia, Chesterfield Islands , Ebisco Stn CP2620, 20 October 2005, 20°05.864'S, 160°22.318'E, 270-532 m: 1 female, 5.8 mm (MNHN-IU-2014-14714). - Kanadeep 1 Stn DW5007, 22°12'S, 159°02'E, 19 September 2017, 290- 750 m: 1 male, 5.6 mm (MNHN-IU-2013-19924) . New Caledonia, Terrasse Stn DW 3083, 24 October 2008, 22°27'S, 167°25'E, 470-570 m: 1 male, 5.2 mm (MNHN-IU-2011-4956). - Exbodi Stn CP 3927, 26 September 2011, 18°36'S, 164°20'E, 381 m: 1 ovigerous female, 4.7 mm (MNHN-IU-2016-5815). - Stn DW 3928, 26 September 2011, 18°38'S, 164°20'E, 362-402 m: 2 males, 4.5-5.2 mm (MNHN-IU-2016-5811). - Stn DW 3930, 26 September 2011, 18°37'S, 164°26'E, 448-464 m: 2 males, 5.3-6.0 mm (MNHN-IU-2011-6466). - Stn DW 3937, 27 September 2011, 18°37'S, 164°26'E, 446-604 m: 1 male, 7.8 mm (MNHN-IU-2013-1793), 2 males, 4.2-6.0 mm, 2 ovigerous females, 5.2-6.0 mm, 1 female, 3.8 mm (MNHN-IU-2011-7263). - Stn CP 3841, 10 September 2011, 22°23'S, 167°24'E, 477-503 m: 2 ovigerous females, 4.8-5.3 mm (MNHN-IU-2016-5819). - Stn DW 3847, 13 September 2011, 22°04'S, 168°41'E, 414-435 m: 1 ovigerous female, 4.4 mm (MNHN-IU-2013-1882). - Stn CP 3848, 13 September 2011, 22°03'S, 168°42'E, 430-440 m: 3 males, 4.2-5.1 mm, 4 ovigerous females, 4.4-4.7 mm (MNHN-IU-2014-18231). - Stn CP 3849, 13 September 2011, 22°03'S, 168°41'E, 360-560 m: 1 male, 6.0 mm (MNHN-IU-2016-5812). - Kanacono Stn DW 4764, 27 August 2016, 23°20'S, 168°15'E, 350-356 m: 1 male, 7.0 mm (MNHN-IU-2017-8561) . Wallis and Futuna Islands, Musorstom 7 Stn DW605, 13°21.3'S, 176°08.4'W, 335-340 m, 26 June 1992: 1 ovigerous female, 4.5 mm (MNHN-IU-2016-517), 7 males, 3.1-6.1 mm, 3 ovigerous females, 4.4-5.3 mm, 2 females, 3.6-4.0 mm (MNHN-IU-2014-14735) . Tonga, Bordau 2 CP1545, 5 June 2000, 21°17'S, 17517°W, 444-447 m: 3 males, 4.1-6.2 mm, 1 ovigerous female, 6.0 mm (MNHN-IU-2014-14739). - Stn CP1643, 21°04.54'S, 175°22.50'W, 487 m, 22 June 2000: 2 males, 5.7-6.8 mm (MNHN-IU-2014-14748), 1 female, 4.6 mm (MNHN-IU-2016-518) .

Description.

Carapace: Slightly longer than broad, feebly convex, with some secondary striae and scales between main transverse ridges. Dorsal ridges with dense short setae, and numerous scattered, long, non-iridescent setae. Gastric region with four or five pairs of epigastric spines, longest pair behind supraocular spines, with intermediate pair of minute spines between large epigastric pair. One or two small hepatic and one parahepatic spine on each side, branchial dorsal and postcervical spines absent. Frontal margins transverse. Lateral margins slightly convex. First lateral spine on anterolateral angle, short, clearly not reaching level of sinus between rostrum and supraocular spines; two small spines in front of anterior branch of cervical groove; end of anterior branch of cervical groove with tuft of iridescent setae. Branchial margins straight, with five small spines, decreasing in size posteriorly. Rostrum spiniform, ~ 0.6-0.7 × length of remaining carapace, laterally carinate, slightly upwards directed. Supraocular spines short, not reaching midlength of rostrum and clearly not reaching end of cornea, subparallel, directed slightly upwards. Grooves between rostrum and supraocular spines moderately shallow. Pterygostomian region unarmed, ending in round tip.

Thoracic sternum: Approximately 0.7 × as long as wide. Maximum width of sternum at sternite VII. Surface of thoracic IV-VI sternites smooth, with a few short striae in sternite IV. Sternite IV trapezoidal; anterior margin wide and subparallel to sternite III along its entire length. Sternite III ~ 2.5-3.0 × as wide as long, sternite IV 2.5 × as wide as long, 2.5 × as wide as sternite III.

Pleon: Tergites II and III each unarmed along anterior ridge, with three uninterrupted transverse ridges on tergite behind anterior ridge, tergites IV and V each with two uninterrupted transverse ridges; ridges with some short setae and a few iridescent setae.

Eye: Cornea dilated, much wider than peduncle. Maximum corneal diameter 0.4 distance between bases of anterolateral spines.

Antennule: Article 1 more than 2.0 × as long as wide, with two well-developed distal spines, distomesial spine clearly shorter than distolateral; two lateral spines, distal much longer than proximal and nearly exceeding distolateral spine.

Antenna: Article 1 with short distomesial spine nearly reaching end of article 2. Article 2 with distomesial and distolateral spines exceeding end of article 3. Article 3 unarmed.

Mxp3: Ischium with strong distal spine on flexor margin. Merus shorter than ischium; flexor margin with two spines, proximal stronger than distal; extensor margin unarmed or with minute spine. Carpus unarmed.

P1: 2.5-2.7 (females), 3.0-3.2 (males) × carapace length, squamate, covered with numerous long plumose and iridescent setae along mesial margin of articles. Merus 1.0-1.2 length of carapace, 2.1-2.2 × as long as carpus, with some dorsal and mesial spines; distal spines strong, distomesial spine nearly reaching proximal third of carpus. Carpus 0.9-1.0 length of palm, 1.4-1.6 × as long as broad, with strong spines along mesial margin, some small spines on dorsal side. Palm 1.3-1.7 × as long as broad, with some small dorsal spines; well-developed spines along lateral and mesial margins. Fingers 1.2-1.4 × as long as palm; fixed finger with spines along lateral margin; movable finger with basal and distal spines.

P2-P4: Moderately long and slender, with numerous iridescent setae along extensor margin of articles. P2 1.9-2.0 × carapace length. Meri shorter posteriorly (P3 merus 0.8-0.9 length of P2 merus, P4 merus 0.7-0.8 length of P3 merus); P2 merus 0.7-0.8 length of carapace, 4.8-4.9 × as long as broad, 1.3-1.4 × as long as P2 propodus; P3 merus 4.8-4.2 × as long as broad, 1.2-1.3 × as long as P3 propodus; P4 merus 3.5-3.7 × as long as broad, 1.1-1.2 × length of P4 propodus. Extensor margins of P2-P4 meri with row of spines, decreasing in size proximally; flexor margins with some well-developed spines followed proximally by several eminences; lateral sides unarmed. Carpi with three or four spines on extensor margin of P2-P3, unarmed on P4; lateral surface with several granules sub-paralleling extensor margin on P2-P4; flexor margin with distal spine. Propodi 4.0-4.7 × as long as broad; extensor margin unarmed; flexor margin with nine or ten slender movable spines on P2-P4, distal end with one fixed spine. Dactyli slender, slightly shorter than propodi; flexor margin with 7-9 movable spinules, with ultimate spinule at base of unguis, penultimate spine much closer to antepenultimate than to ultimate spine; P2 dactylus 3.7-4.5 × as long as wide. P4 merocarpal articulation not reaching anterior end of cervical groove; P4 merus ~ ½ length of P2 merus.

Colour in life.

Ground colour of carapace and pleomere tergites pale orange. Rostrum orange, supraocular spines whitish. Transverse whitish stripes on median and posterior parts of carapace. Median and lateral parts of pleomere tergites with orange spots. P1-P4 pale orange without transverse stripes; P1 with a few dorso-median red spots; distal portion of fingers whitish. P2-P4 dactyli whitish (Fig. 9B ).

Genetic data.

COI, 16S.

Etymology.

From the Latin, Trapezionida pulex , flea, in reference to the small size of the species.

Remarks.

The new species is morphologically very close to T. leptitis (Macpherson, 1994) (see above), whichwas described from specimens collected in New Caledonia, and it was found later off Wallis and Futuna area, Taiwan, Indonesia, Papua-New Guinea, Vanuatu, Fiji, Tonga, and French Polynesia (see Macpherson et al. 2020 and references cited therein). Nevertheless, some slight morphological differences among specimens suggest the existence of a complex of cryptic species with overlapping distribution ranges. The molecular analysis of specimens from the different localities has demonstrated the existence of two species, T. leptitis and T. pulex . Both species are genetically distinct, although only separated morphologically by slight differences.

Both species can be differentiated by the following aspects:

The thoracic sternite III is more slender in T. leptitis than in T. pulex (3.5-4.5 × as wide as long in T. leptitis and 2.5-3.0 × in T. pulex ).

The P2-P4 are more slender in T. pulex than in T. leptitis . The propodi are 5.3-5.7 × as long as broad and the dactyli 5.0 × as long as broad in T. pulex . These values are 4.0-4.6 and 3.7-4.5 ×, respectively, in T. leptitis .

The colour patterns of both species are different. For instance, the dorsal surface of the P1 has numerous red spots in T. leptitis , whereas these spots are very few in T. pulex .

Genetically the new species is different from T. leptitis : 7.44% 16S and 13.54% COI.

Distribution.

The species is found in Indonesia, Vanuatu, Loyalty Islands, New Caledonia, Wallis and Futuna Islands, Fiji, Tonga, and French Polynesia. The depth range of these specimens is 135-750 m.

Figures

Figure 8. Trapezionida pulex sp. nov., male holotype, 5.4 mm (MNHN-IU- 2016 - 5809), 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 left P 2, lateral view G dactylus of left P 2, lateral view H left P 3, lateral view I left P 4, lateral view. Scale bars: 1.0 mm (A, E, F, H, I); 0.5 mm (B, C, D, G).

Figure 9. Colour in life A Trapezionida macilenta sp. nov., male holotype, 5.7 mm (MNHN-IU- 2013 - 1094), Papua-New Guinea B Trapezionida pulex sp. nov., ovigerous female paratype, 4.4 mm (MNHN-IU- 2013 - 1882), New Caledonia.