Leucon ( Leucon ) brevirostratis, Mühlenhardt-Siegel, 2025

Leucon ( Leucon) brevirostratis sp. nov.

( Figures 23–25 View FIGURE 23 View FIGURE 24 View FIGURE 25 )

Material:

Holotype: ovigerous female ( ZMH K 64955 View Materials ) ( 16 July 2009), SW Atlantic, Argentine Basin, FS “Meteor”cruise Me 79/1 station #534, 36° 00.61'S 49° 01.54'W, 4608 m depth; gear: EBS. GoogleMaps

Paratypes:

Argentine Basin

# 532—EBS: 1 adult male, 2 subadult males, 1 juv. male, 6 non-ovigerous female; 2 mancae, 1 abdomen ( ZMH K 64994 View Materials ) .

# 533—EBS: 2 adult males, 6 subadult males, 1 juv. male, 4 ovigerous females (1 with pleon broken off), 17 non-ovigerous females, 8 mancae ( ZMH K 64995 View Materials ) .

# 534—EBS: 1 male pleon; 1 ovigerous female carapace, 3 ovigerous females, 1 ovigerous female 6.1 mm long, dissected; ( ZMH K 64956 View Materials ), 32 non-ovigerous females, 22 mancae, 5 adult males, 9 subadult males, 1 juvenile male ( ZMH K 64996 View Materials ) .

Brazil Basin

# 604—EBS: 1 adult male ( ZMH K 64997 View Materials ) .

Etymology.—The new species is named “ brevirostratis ” (Lat. brevis = short and rostratis = rostrum) because of its short pseudorostrum.

Diagnosis.—Carapace with anterior margin serrate above antennal notch, dorsomedian line serrate to end of carapace; no lateral teeth on carapace; antennal notch triangular and small; exopods of maxilliped 3, P1–P 3 in females with teeth.

Description.—Based on holotype ( Fig. 23 View FIGURE 23 ), ovigerous female, 6.5 mm long (ZMH K 64955 View Materials )

Carapace 1.1 times longer than free thoracic segments; dorsomedian line serrate with 24 teeth to the end of carapace, no lateral teeth; pseudorostral lobes 0.2 length of rest of carapace, directing slightly upwards; siphonal tube little protruding; ocular lobe reduced; eye lenses missing; antennal notch triangular, reaching backwards to level of ocular lobe; anterolateral tooth prominent; anterior margin serrate with at least 8 teeth; anteroventral margin of carapace serrate; integument whitish, roughened.

Five free thoracic segments visible, first shortest. Pleon as long as carapace and free thoracic segments combined. Pleotelson 1.1 times longer than wide.

Appendages: ovigerous female, 6.1 mm long ( Fig. 24 View FIGURE 24 ), paratype ( ZMH K 64956 View Materials )

Antenna 1 ( Fig. 24 View FIGURE 24 , A 1 View FIGURE 1 ): relative length of peduncle articles 1 to 3: 46/26/28; accessory flagellum tiny, main flagellum 3 articulated.

Maxilliped 2 ( Fig. 24 View FIGURE 24 , Mxp2): B/R ratio 0.5, relative length of articles I to D: 7/27/32/23/12;

basis with one pappose seta; ischium and merus unarmed; carpus with one pappose seta and 12 simple setae along inner margin; propodus with one strong pappose seta, 7 simple setae; dactylus one strong terminal seta, 2 simple setae sub terminally.

Maxilliped 3 ( Fig. 24 View FIGURE 24 , Mxp3): B/R ratio 1.4, relative length of articles I to D: 7/21/36/24/12;

basis with 5 pappose setae along inner margin, 4 pappose seta on distal margin; ischium unarmed; merus with 2 pappose setae; carpus with 3 teeth and one simple seta on outer margin, 6 pappose setae along inner margin; propodus with one simple and one pappose seta; dactylus with one terminal seta and 3 sub terminal simple setae; exopod present basal article serrate.

Pereiopod 1 ( Fig. 24 View FIGURE 24 , P 1 View FIGURE 1 ): B/R ratio 0.8, relative length of articles I to D: 9/18/33/23/17;

basis with 4 teeth along outer margin and 11 pappose setae on margins; ischium with one tooth; merus with one tooth, one simple seta and 2 pappose setae; carpus with 4 pappose setae and 4 simple setae; propodus with 4 simple and 3 pappose setae; dactylus with one terminal and 6 simple setae; exopod present, basal article with 5 teeth.

Pereiopod 2 ( Fig. 24 View FIGURE 24 , P 2 View FIGURE 2 ): B/R ratio 0.9, relative length of articles I to D: 4/25/27/15/29;

basis with 6 pappose setae; ischium with one pappose seta; merus with 4 pappose setae;

carpus with 2 simple setae; propodus unarmed; dactylus with 3 longer and 6 shorter simple setae; exopod present, basal article with 4 teeth.

Pereiopod 3 ( Fig. 25 View FIGURE 25 , P 3 View FIGURE 3 ): B/R ratio 1.8, relative length of articles I to D: 14/24/32/22/8;

basis with one simple seta and 6 pappose setae; ischium with 3 pappose setae;

merus with one pappose setae; carpus with 2 long pappose setae, one long and one short simple setae; propodus with one long simple seta distally; dactylus with one terminal simple seta; exopod present, basal article with 3 teeth.

Pereiopod 4 ( Fig. 25 View FIGURE 25 , P 4 View FIGURE 4 ): B/R ratio 1.2, relative length of articles I to D: 15/20/33/23/8;

basis with 7 pappose setae; ischium with one pappose seta; merus with 2 pappose setae; carpus with one pappose seta medially, 2 plumose setae and one simple long seta distally; propodus with one long simple seta; dactylus with one long simple seta terminally.

Pereiopod 5 ( Fig. 25 View FIGURE 25 , P 5 View FIGURE 5 ): B/R ratio 1, relative length of articles I to D: 14/22/33/24/8;

basis one simple, one pappose and one broom seta; ischium with one simple and one pappose seta; merus with one simple seta; carpus with one pappose seta, one short simple and 3 strong simple setae; propodus with one long simple seta; dactylus with one long simple seta terminally.

Uropods ( Fig. 25 View FIGURE 25 , U), peduncle slightly longer than pleonite 6, with 3 cuspidate setae along inner margin; exopod longer than endopod; endopod 2 articulated, basal article 1.4 times longer than distal article, with 7 cuspidate setae along inner margin, the distal one largest; distal article with 6 cuspidate setae along inner margin, 3 strong setae terminally.

Adult male: antero-dorsomedian line with 2 or 3 teeth (in higher magnification 17 small teeth nearly reaching hind margin), antennal notch shallow, anterior margin of carapace serrate above antennal notch; A1 accessory flagellum about half as long as basal article of main flagellum,A2 reaching beyond thoracic segments; subadult male with 2 pairs of developing pleopods: anterior margin of carapace above antennal notch serrate up to pseudorostrum tip, dorsomedian line serrate until end of carapace (26 teeth), antennal notch at level of ocular lobe; antennal notch small, triangular. Uropod exopod longer than endopod, which has 2 articles.

Distribution: Argentine and Brazil Basin, 4602 to 5188 m depth.

Remarks: There are only few species in the subgenus Leucon with this combination of characters: antennal notch ending on level with anterior margin of frontal lobe, no teeth on frontal lobe or laterally on carapace, dorsomedian serration to the hind margin of carapace as in the new species: Leucon affinis Fage 1951 from the Mediterranean ( 180–415 m depth), Leucon serratus Norman, 1879 from the Arctic region ( 2200–3200 m depth) and Leucon echinolophotus Gerken 2016 , off Enderby Land, Antarctica ( 386–400 m depth).

The new species differs from these in the following characters:

there is no gap in the dorsomedian serration on the carapace before the last tooth in the new species but there is a gap in L. affinis , L. serratus and L. echinolophotus ; the length proportion “pseudorostrum to rest of carapace” is 0.2 in the new species but 0.36 in L. affinis , 0.26 in L. serratus and 0.19 in L. echinolophotus ; the exopod of at least pereiopod 2 has 4 teeth in the new species but no teeth in L. affinis and L. echinolophotus , no information for L. serratus ;

there are 8 teeth in the new species on the anterior margin of the carapace above the antennal notch but no teeth in L. affinis , L. serratus and L. echinolophotus . The pseudorostrum of the new species is 0.2 times of carapace length and shorter than in Remyleucon hyalorostris n.g., n.sp. (see below).