Leucon (Leucon) paravasilei, Mühlenhardt-Siegel, 2025

Leucon View in CoL ( L.) paravasilei sp. nov.

( Figures 26–29 View FIGURE 26 View FIGURE 27 View FIGURE 28 View FIGURE 29 )

Material:

Holotype non-ovigerous female, ZMH: K 64957 View Materials ( 16 July 2009); SW Atlantic, Argentine Basin, FS “Meteor” cruise Me 79- 1, station # 534, 49° 01.54'W 36° 00.61'S, 4608 m depth, gear: EBS. GoogleMaps

Paratypes:

Argentine Basin

# 533—EBS: 1 non-ovigerous female ( ZMH K 65768 View Materials ) .

#534—EBS: 1 sub adult male (figured; ZMH K 64959 View Materials ), 1 sub adult male (2 pairs of developing pleopods; dissected; ZMH K 64958 View Materials ), 1 cephalothorax, damaged; 1 non-ovigerous female (only carapace plus thoracic segments) (ZMH K 64999 View Materials ).

Brazil Basin

#604—EBS: 1 manca, 1 ad male (pleon broken off) (ZMH K 65000 View Materials ).

#609—EBS: 2 non-ovigerous females (ZMH K 65001 View Materials ).

Etymology.—The new species is named “ paravasilei ” because of the resemblance to Leucon vasilei Petrescu 1994 , described for the south eastern Pacific off central Chile ( 3279 m depth) waters.

Diagnosis.—Carapace dorsomedian line with 2–3 teeth anterior and 8–10 teeth posterior to the gap, several teeth laterally above frontal lobe fissure, occasionally one tooth below frontal lobe fissure; pseudorostral lobes directed straight forward, without teeth above or below, 0.3 of rest of carapace.

Description.—based on holotype, non-ovigerous female ( Fig. 26 View FIGURE 26 ), 5.7 mm long, ZMH K 64957 View Materials ).

Carapace dorsomedially with 2 teeth anterior and 10 teeth posterior to the gap, several teeth laterally above frontal lobe fissure, occasionally one tooth below frontal lobe fissure; pseudorostral lobes directing straight forward, without teeth above or below, 0.3 of rest of carapace; siphonal tube little protruding; ocular lobe reduced; eye lenses missing. Antennal notch reaching backwards to level of ocular lobe; anterolateral tooth produced; anteroventral margin of carapace smooth; integument whitish, smooth.

Five free thoracic segments visible, first shortest; as long as carapace (including pseudorostrum). Pleon approximately as long as carapace plus free thoracic segments.

Pleotelson as wide as long, anal valves little protruding.

Appendages: subadult male, 5.4 mm long, paratype ( ZMH K 64958 View Materials ) .

Antenna 1 ( Fig. 27 View FIGURE 27 , A 1 View FIGURE 1 ): relative length of peduncle articles 1 to 3:37/37/25; accessory flagellum very short, main flagellum broken after second article.

Maxilliped 2 ( Fig. 25 View FIGURE 25 , Mxp2): B/R ratio not given, basis broken during dissection, relative length of articles I to D: 5/28/35/18/14; basis with one pappose seta on inner distal corner; ischium unarmed; merus with one pappose seta and 4 simple setae; carpus with 12 simple setae; propodus with one strong pappose seta and 11 simple setae along inner and distal margin; dactylus with one strong simple seta terminally, 4 simple setae sub terminally.

Maxilliped 3 ( Fig. 27 View FIGURE 27 , Mxp2): B/R ratio 0.8, relative length of articles I to D: 7/19/36/23/16;

basis distal outer edge dilated, with 3 strong pappose setae, 4 pappose setae along inner margin; ischium unarmed; merus with 2 pappose setae on inner margin, one strong pappose seta on outer distal edge; carpus with 3 pappose setae on inner margin; propodus with 2 simple setae on inner margin, 3 pappose setae on outer distal corner; dactylus with 4 simple setae on distal margin; exopod present.

Pereiopod 1 ( Fig. 27 View FIGURE 27 , P 1 View FIGURE 1 ): B/R ratio and relative length of articles I to D not given, broken after basis; basis with 6 pappose setae and 2 short, strong setae each with 6 setulae

Pereiopod 2 ( Fig. 27 View FIGURE 27 , P 2 View FIGURE 2 ): B/R ratio 1.2, relative length of articles I to D: 5/24/27/19/25;

basis with 9 pappose setae; ischium with one pappose seta; merus with 2 pappose setae and one simple seta; carpus with one pappose seta and 4 simple setae; propodus unarmed;

dactylus with 2 plumose and 7 simple setae; exopod present.

Pereiopod 3 ( Fig. 28 View FIGURE 28 , P 3 View FIGURE 3 ): B/R ratio 3.0, relative length of articles I to D: 16/28/28/20/8;

basis with 13 pappose setae; ischium with one simple seta; merus with one simple seta;

carpus with 2 pappose setae; propodus with one simple seta; dactylus fused with terminal seta; exopod present.

Pereiopod 4 ( Fig. 28 View FIGURE 28 , P 4 View FIGURE 4 ): B/R ratio 1.6, relative length of articles I to D: 22/23/27/20/8;

basis with 9 pappose setae; ischium with one pappose seta; merus with one simple seta and 2 pappose setae; carpus with 2 pappose setae on outer distal corner; propodus with one simple seta; dactylus with one simple seta terminally; exopod present.

Pereiopod 5 ( Fig. 28 View FIGURE 28 , P 5 View FIGURE 5 ): B/R ratio 1.3, relative length of articles I to D: 20/25/25/20/9;

basis with 5 pappose setae; ischium with 2 long simple setae; merus with one simple seta; carpus with one simple and 2 serrulate setae; propodus with one long and one shorter simple setae; dactylus with strong terminal seta.

Uropods ( Fig. 28 View FIGURE 28 , U), peduncle with 2 simple setae along inner margin, subequal in length to pleonite 6; exopod longer then endopod; endopod 2-articulated, first article as long as peduncle, with 6 simple setae along inner margin; second article with 3 cuspidate-serrulate setae along inner margin, one strong terminally serrate seta; 0.4 times in length of article 1.

Subadult male with developing 2 pairs of pleopods ( Fig. 29 View FIGURE 29 ), 6.1 mm long (ZMH K 64959 View Materials ); no dorsomediane serration; 3 teeth laterally above frontal lobe fissure; antennal notch shallow, with 3 teeth at base of pseudorostrum; exopods of pereiopods with basis dilated.

Distribution: Argentine and Brazil Basins, 4608 to 5180 m depth.

Remarks: The new species has the uropod endopod longer than the exopod, and the anterior tip and ventral margin of the pseudorostrum smooth as in L. vasilei Petrescu 1994 . However, in L. vasilei there is only one tooth dorsomedially in the frontal lobe area and a pair of teeth on the pseudorostral lobe base, whereas in the new species both sexes have 3 teeth above the frontal lobe fissure. The uropod exopod reaches the articulation of the first article of the endopod in L. vasilei (beyond articulation in the new species).