Leucon ( Alytoleucon ) argentinensis, Mühlenhardt-Siegel, 2025

Mühlenhardt-Siegel, Ute, 2025, The cumacean family Leuconidae in the south-west Atlantic deep-sea basins obtained during the cruise DIVA 3 with RV Meteor (cruise No. M 79 / 1), Zootaxa 5716 (2), pp. 151-206 : 171-177

publication ID	https://doi.org/10.11646/zootaxa.5716.2.1
publication LSID	lsid:zoobank.org:pub:17F5F026-7451-46B5-8838-C1D5561C04FA
persistent identifier	https://treatment.plazi.org/id/9F2B0602-AF18-FFED-72DA-B0F92BD896B4
treatment provided by	Plazi
scientific name	Leucon ( Alytoleucon ) argentinensis
status	sp. nov.

Treatment

Leucon ( Alytoleucon) argentinensis sp. nov.

( Figures 13–16 View FIGURE 13 View FIGURE 14 View FIGURE 15 View FIGURE 16 )

Material:

Holotype: ovigerous female ( ZMH K 64950 View Materials ) ( 15 July 2009); SW Atlantic, Argentine Basin, station #533, 36° 00.20'S 49° 01.96'W; 4602 m depth; gear: EBS. GoogleMaps

Paratypes: Argentine Basin : #532—EBS: 1 adult male (was dried), 53 subadult males, 1 male carapace, 61 non-ovigerous females, 9 preparatory females, 7

ovigerous females, 19 mancae, 9 damaged/carapaces only ( ZMH K 64978 View Materials ). #533—EBS: 3 adult males (1 figured, 1 with pleon missing after pleonite 3), 61 subadult males, 94 ovigerous females (1 figured,

1 dissected, ZMH K 64951 View Materials ), 412 non-ovigerous females, 111 mancae/juveniles, 18 carapaces only ( ZMH K 64979 View Materials ). #534—EBS: 1 adult male ( ZMH K 64952 View Materials , special vial), 100 subadult males, 320 ovigerous females, 314 non-ovigerous females ,

22 juveniles, 30 mancae, 149 carapaces only/badly damaged specimens ( ZMH K 64980 View Materials ) .

Etymology.—The new species is named after the locality of distribution, the Argentine Basin.

Diagnosis.—Carapace dorsomedian line serrate (17 teeth) to the hind margin; A1 rather stout, peduncle articles almost equal in length; antennal notch with small extra tooth in sinus, sinus reaching beyond level of frontal lobe anterior margin.

Description.—Based on holotype, ovigerous female ( Fig. 13 View FIGURE 13 ), 4.7 mm long (ZMH K 64950 View Materials ).

Carapace 1.2 times longer than free thoracic segments; dorsomedian line serrate (17 teeth) up to hind margin; pseudorostral lobes 0.3 times of remaining carapace length, meeting in front of ocular lobe, ventral margin finely serrate; siphonal tube not protruding in holotype; anterolateral tooth developed; ventral margin of carapace serrate ocular lobe small; eye lenses missing. Antennal notch round, with small extra tooth in sinus, sinus reaching beyond level of frontal lobe anterior margin; integument smooth, whitish.

Five free thoracic segments visible.

Pleon subequal in length to carapace + pereion.

Pleotelson 1.2 times longer than wide; 0.8 times of uropod peduncle; anal valves visible in dorsal view.

Appendages: ovigerous female, 4.3 mm long ( paratype ZMH K 64951 View Materials )

Antenna 1 ( Fig. 14 View FIGURE 14 , A 1a and A1b View FIGURE 1 ): relative length of peduncle articles 1 to 3: 37/33/30 (35/34/ 32 in another ovigerous female); second article with 4 broom-like setae and 3 simple setae; third article with one simple seta; accessory flagellum half as long as basal article of main flagellum; main flagellum 3-articulated, armatures broken off.

Maxilliped 2 ( Fig. 14 View FIGURE 14 , Mxp2): B/R ratio 0.2, relative length of articles I to D: 6/25/45/18/6; basis and ischium unarmed; merus with one plumose seta; carpus with 9 setulate setae; propodus with 10 simple setae along inner margin, one simple seta on outer distal corner; dactylus with one strong simple seta terminally, 4 simple setae sub terminally; rudimentary oostegite with 4 strong setae.

Maxilliped 3 ( Fig. 14 View FIGURE 14 , Mxp3): B/R ratio 1.6, relative length of articles I to D: 8/26/26/26/13;

basis with 3 fine plumose setae, 3 plumose seta on outer distal corner; ischium unarmed; merus with one strong plumose seta; carpus with 3 plumose setae; propodus with 3 plumose setae; dactylus with 6 simple setae terminally; exopod present.

Pereiopod 1 ( Fig. 14 View FIGURE 14 , P 1 View FIGURE 1 ): B/R ratio 0.6, relative length of articles I to D: 9/17/27/26/21;

basis with 13 plumose setae and one simple seta; ischium and merus unarmed; carpus with 2 simple setae; propodus with 4 simple setae; dactylus with one terminal seta and 4 simple setae sub terminally, one simple seta on outer margin; exopod present.

Pereiopod 2 ( Fig. 14 View FIGURE 14 , P 2 View FIGURE 2 ): B/R ratio 0.8, relative length of articles I to D: 6/21/30/15/28;

basis with 4 plumose setae; ischium unarmed; merus with one simple seta and 2 plumose setae; carpus with 2 simple setae; propodus unarmed; dactylus tapering, with one terminal seta, 3 strong simple setae sub terminally, 2 thin simple setae on margins; exopod present.

Pereiopod 3 ( Fig. 15 View FIGURE 15 , P 3 View FIGURE 3 ): B/R ratio and relative length of articles I to D not given, extremity damaged after merus; basis with 5 plumose setae; ischium with one simple seta; merus with 2 simple setae; exopod present.

Pereiopod 4 ( Fig. 15 View FIGURE 15 , P 4 View FIGURE 4 ): B/R ratio 1.1, relative length of articles I to D: 18/25/29/20/7;

basis with 4 plumose and 2 simple setae; ischium with 2 simple setae; merus with one stronger and one thin simple seta; carpus with 2 strong and 2 thin simple setae; propodus with one strong simple seta; dactylus with one strong and one thin seta terminally.

Pereiopod 5 ( Fig. 15 View FIGURE 15 , P 5 View FIGURE 5 ): B/R ratio 1.0, relative length of articles I to D: 16/22/30/24/8;

basis with 2 plumose and 2 simple setae; ischium with one strong and 2 thin simple setae; merus with one strong and one thin simple setae; carpus with 2 strong simple setae on outer distal corner; propodus with one strong simple seta; dactylus with one strong and one thin simple seta.

Uropods ( Fig. 15 View FIGURE 15 , U), peduncle 1.2 times longer than endopod and 1.3 times longer than pleonite 6, with 4 cuspidate setae along inner margin; exopod sub equal in length to endopod (measured without terminal seta); endopod 2-articulated, basal article 3.6 times longer than distal article, with 8 (or 9?) cuspidate setae along inner margin; distal article with 4 simple setae along inner margin, the penultimate one longer than the other, terminal seta fused to distal article.

Adult male, ZMH K 64952 View Materials ( Fig. 16 View FIGURE 16 ), similar to female besides the sexual dimorphisms: shorter pseudorostrum, antennal notch shallower than in female; stronger basis of extremities; exopod present on pereiopod 4; 2 pairs of pleopods, pleonites 1 and 2 with 1 tooth on ventrolateral margin; A2 reaching beyond pleonite 3.

Distribution: Argentine Basin, 4602–4608 m depth.

Remarks: The new species is similar to Leucon ( A.) medius Bishop, 1982 from Brazil, 1000–1580 m depth (see Table 3). Both have lateral conical teeth in male on pleonites 1 and 2, lateral to the insertion of the pleopods. However, there are a few slight differences between the species. The A 1 in the female of the new species is stouter and shorter (fig. 14, A1a) than in L. medius ; the A1 of a different and ovigerous female from the present samples is not as slender as in L. medius . There are 17–20 strong dorsomedian teeth in ovigerous females to the hind margin of the carapace in the new species but only a weak undulation in L. medius . The antennal notch of the new species is rounded and reaches beyond the frontal line of the frontal lobe, but it is triangular in L. medius and ends at the level of the frontal lobe.