Leucon (C.) parantarcticus, Mühlenhardt-Siegel, 2011

Mühlenhardt-Siegel, Ute, 2011, New and known species of the family Leuconidae (Cumacea, Peracarida) from Antarctic deep-sea basins 3117, Zootaxa 3117 (1), pp. 1-68 : 25-28

Leucon (C.) parantarcticus sp. n.

( Figures 17–19 )

Material. Holotype subadult male, ZMH: K 42941 ; 9 February 1998.

Type locality. Antarctica, south-eastern Weddell Sea , 74° 31.72’ S 27° 12.80’ W, 2119 m depth, ANT XV, #133, epibenthic sledge .

Paratypes: E Weddell Sea: ANT XV #89: 1 female (dissected), 5 non-ovigerous females, 1 manca, 2 subadult males; ANT XV #114: 1 female (dissected), 1 non-ovigerous female, 1 subadult male; ANT XV #133: 1 female with developing oostegites, 1 subadult male; ANT XV #142: 1 female (dissected), 1 manca; ANT XV #145: 2 subadult females; ANT XV #272: 1 female (dissected), 2 females with oostegites, slightly damaged. ZMH K 42942 .

Etymology. The name of the new species is a composistion of “para” (Gr.: situated near) and “antarcticus”, the species it resembles the most.

Diagnosis. Leuconid with long uninterrupted dorsomedian serration with 18 teeth up to posterior carapace margin; no lateral tooth either at frontal or at pseudorostral lobes; antennal notch reaching not beyond level of anterior margin of frontal lobe; accessory flagellum of antenna 1 longer than basal article of main flagellum.

Description. Holotype, 3.9 mm long ( Fig. 17 ).

Carapace with 18 dorsomedian teeth up to posterior end, longer than free thoracic segments; pseudorostral lobes meeting in front of ocular lobe, 0.3 times as long as carapace measured from ocular lobe to posterior margin; siphonal tube not protruding; ocular lobe reduced; eyes missing. Antennal notch not reaching beyond level of anterior margin of frontal lobe; anterolateral tooth slightly rounded, first tooth of anteroventral margin longer; anteroventral margin of carapace serrate. Integument with scaly structure, visible at higher magnification. Five free thoracic segments visible. Pleon slightly shorter than carapace and free thoracic segments combined. Pleotelson slightly longer than wide, 0.8 times as long as uropod peduncle, anal valves visible in dorsal view.

Appendages: female (paratype, ANT XV #89 ) .

Antenna 1 ( Fig. 18 , A 1 ): relative length of peduncle articles 1 to 3 not given, article 1 broken;

accessory flagellum longer than basal article of main flagellum, with two strong terminal setae; main flagellum tri-articulated, second article longest, two aesthetascs, one inserting at penultimate, the other at terminal article.

Maxilliped 2 ( Fig. 18 , Mxp2): B/R ratio 0.7, relative length of articles I to D: 6/28/33/22/11; strong setulate seta at distal margin of basis and merus; carpus with six setulate setae along inner margin; propodus with long setulate seta inserting at proximal third; terminal seta longer than dactylus.

Maxilliped 3 ( Fig. 18 , Mxp3): B/R ratio 1.4, relative length of articles I to D: 11/27/29/21/13; basis with five short setulate setae, distally produced and with three long setulate setae at outer distal corner; merus with long setulate seta at outer distal corner; carpus with three short setulate setae along inner margin, one longer setulate seta at outer distal corner; propodus with two setulate setae along distal margin; dactylus with terminal seta longer than article, three simple setae subterminally; exopod present.

Pereiopod 1 ( Fig. 18 , P 1 ): B/R ratio 0.9, relative length of articles I to D: 11/21/27/25/16; basis with five setulate setae along inner margin, four strong simple setae along distal margin; ischium to propodus with short simple setae; dactylus with terminal seta equal in length to article, three subterminal simple setae; exopod present.

Pereiopod 2 ( Fig. 18 , P 2 ): B/R ratio 0.9, relative length of articles I to D: 7/24/27/16/26; basis with one strong distal simple seta and three setulate setae; merus with simple seta and three setulate setae; carpus with one setulate seta and two simple setae along outer margin and two simple setae at inner distal corner; dactylus with two long and three short simple setae terminally and three shorter at half; exopod present.

Pereiopod 3 ( Fig. 19 , P 3 ): B/R ratio 1.8, relative length of articles I to D: 17/20/35/24/4; ischium with two long simple setae along distal margin; merus with two simple setae distally; carpus with one short simple seta at distal and inner margin; propodus with one long simple seta; dactylus minute, terminal seta slightly shorter than carpus to dactylus combined; exopod present.

Pereiopod 4 ( Fig. 19 , P 4 ): B/R ratio 1.3, relative length of articles I to D: 13/28/32/19/8; basis with few short setulate setae; merus with two long simple setae; carpus with two shorter and two long simple setae; propodus with one long simple seta; dactylus minute, with long terminal seta.

Pereiopod 5 ( Fig. 19 , P 5 ): B/R ratio 0.9, relative length of articles I to D: 20/21/33/20/7; basis with one simple and two setulate setae distally; ischium, carpus and propodus with two simple setae at distal corner; dactylus minute, terminal seta long.

Uropod ( Fig. 19 , U): peduncle slightly longer than endopod, with six setae along inner margin; exopod slightly shorter than endopod; endopod bi-articulated, basal article with seven cuspidate setae along inner margin, 2.4 times as long as distal article; distal article with three cuspidate setae along inner margin, terminal seta long, one semilong seta subterminally.

Remarks. The new species is at first glance very similar to Leucon (C.) antarcticus , particularly in terms of the long and uninterrupted dorsomedian serration, the number of setae along the inner margin of the uropod peduncle and the accessory flagellum of antenna 1 being longer than the basal article of the main flagellum. However, in contrast to L. antarcticus , all the specimens investigated have no lateral tooth at the carapace, neither at frontal nor at pseudorostral lobe.

Figures

FIGURE 1. Leucon (A.) polarsterni Ledoyer, 1993, subadult female habitus, 5.5 mm long.

FIGURE 2. Leucon (A.) polarsterni Ledoyer, 1993, A1: antenna 1, Mxp2: maxilliped 2, Mxp3: maxilliped 3, P1: pereiopod 1, P2: pereiopod 2; scale bars 100 µm (A1, Mxp2, Mxp3) and 200 µm (P1, P2).

FIGURE 3. Leucon (A.) polarsterni Ledoyer, 1993, P3: pereiopod 3, P4: pereiopod 4, P5: pereiopod 5, U: pleotelson and uropods; scale bars 100 µm (P3, P4, P5) and 200 µm (U).

FIGURE 4. Leucon (A.) polarsterni Ledoyer, 1993, SEM photos, habitus female (above left), carapace (above right, middle left), uropods (middle right), endopod’s terminal seta (below).

FIGURE 5. Leucon (C.) antarcticus Zimmer, 1907, non-ovigerous female habitus, 3.5 mm long.

FIGURE 17. Leucon (C.) parantarcticus sp. n., habitus holotype, subadult male, scale bar: 0.5 mm.

FIGURE 18. Leucon (C.) parantarcticus sp. n., A1: antenna 1, Mxp2: maxilliped 2, Mxp3: maxilliped 3, P1: pereiopod 1, P2: pereiopod 2; scale bars: 50 µm (A1) and 100 µm (Mxp2, Mxp3, P1, P2).

FIGURE 19. Leucon (C.) parantarcticus sp. n., P3: pereiopod 3, P4: pereiopod 4, P5: pereiopod 5, U: pleotelson and uropods; scale bars: 50 µm (P5) and 100 µm (P3, P4, U).