Leucon (C.) weddellensis, 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 : 28-32

Leucon (C.) weddellensis sp. n.

( Figures 20–22 )

Material. Holotype subadult male, ZMH: K 42943 ; 6. February 1998.

Type locality. Antarctica, south-eastern Weddell Sea , 73° 34.77’ S 22° 38.29’ W, 938 m depth, ANT XV, #107, epibenthic sledge .

Paratypes: E Weddell Sea: ANT XV #107: 2 subadult males, 1 subadult female, 3 mancas; ANT XV #130: 2 subadult males, 3 females with oostegites, 11 non-ovigerous females (1 dissected), 7 mancas; ANDEEP III #80: 1 ovigerous female (dissected), 1 subadult female (damaged). ZMH K 42944 .

Etymology. The new species is named after the type locality, the Weddell Sea.

Diagnosis. Row of dosomedian teeth almost to end of carapace with 19 teeth in males; one lateral carapace tooth each at frontal and pseudorostral lobe; one seta at inner margin of uropod peduncle; first (basal) article of endopod 3.4 times as long as distal article; accessory flagellum of antenna 1 almost as long as basal article of main flagellum.

Description. Holotype, 3.3 mm long ( Fig. 20 ).

Carapace with two small and indistinct lateral teeth, one on each, frontal and pseudorostral lobe; dorsomedian row of 19 teeth extending from anterior margin of frontal lobe to close to the posterior margin of carapace; pseudorostral lobes meeting in front of ocular lobe, directed forwards, 0.2 times as long as carapace measured from anterior margin of frontal lobe to posterior dorsal margin of carapace; siphonal tube not protruding; ocular lobe rudimentary; eyes missing. Antennal notch reaching beyond level of anterior margin of frontal lobe; anterolateral tooth acute; anteroventral margin of carapace serrate. Integument white, very weak scaly structure. Five free thoracic segments visible. Pleon slightly shorter than carapace and free thoracic segments combined. Pleotelson slightly wider than long, 0.8 times as long as uropod peduncle.

Appendages: female (paratype).

Antenna 1 ( Fig. 21 , A 1 ): relative length of peduncle articles 1 to 3: 44/27/29; geniculate between article 1 and 2, long setulate seta at article 2; accessory flagellum almost as long as basal article of main flagellum; main flagellum tri-articulated, two aesthetascs, one inserting at penultimate, one at terminal article.

Maxilliped 2 ( Fig. 21 , Mxp2): B/R ratio 0.6, relative length of articles I to D: 7/29/29/22/14; merus with long setulate setae, one inserting proximally, one at inner distal corner; carpus with six setulate setae along inner margin; propodus with five simple setae along inner margin and three along distal margin; dactylus with long setulate seta inserting proximally, three simple setae, terminal seta short and stout, one hair-like seta subterminally.

Maxilliped 3 ( Fig. 21 , Mxp3): B/R ratio 1.8, relative length of articles I to D: 8/23/40/21/8; basis with two teeth at outer margin, distally produced, with three long setulate setae at outer distal corner; merus with setulate seta at outer distal corner; carpus with three short setulate setae along inner margin; propodus with two simple setae at outer distal corner; dactylus with one terminal seta, two simple and one setulate seta subterminally; exopod basal article with two teeth.

Pereiopod 1 ( Fig. 21 , P 1 ): B/R ratio 0.6, relative length of articles I to D: 9/16/38/25/12; basis with four setulate setae: two along inner and two at distal margin; ischium with setulate seta; merus with one short simple and one fine setulate seta; carpus with hair-like seta at inner distal third and fine setulate seta at outer distal corner; propodus with hair-like setae at inner and distal margin; dactylus with two long simple setae terminally, two short simple setae subterminally; exopod present.

Pereiopod 2 ( Fig. 21 , P 2 ): B/R ratio 0.8, relative length of articles I to D: 3/22/33/15/27; basis with two hairlike setae at distal third; ischium minute; merus with two setulate setae at inner distal corner; carpus with four simple and three setulate setae; dactylus with two simple setae at margins, one stout terminal and two long simple setae subterminally; exopod present.

Pereiopod 3 ( Fig. 22 , P 3 ): B/R ratio 1.6, relative length of articles I to D: 10/21/41/21/8; setae along basis mostly broken off; one setulate seta distally at ischium to carpus; propodus with setulate seta at outer margin, simple seta distally; dactylus with stout terminal seta.

Pereiopod 4 ( Fig. 22 , P 4 ): B/R ratio 1.0, relative length of articles I to D: 12/16/33/22/16; merus with setulate seta at distal margin; carpus with one long and one short simple seta distally; propodus with setulate seta at outer margin and two simple setae distally; dactylus with terminal seta longer than dactylus.

Pereiopod 5: broken off.

Uropod ( Fig. 22 , U): Peduncle shorter than rami, with one seta at inner margin; exopod as long as endopod; endopod bi-articulated, proximal article 3.4 times as long as distal article, with five cuspidate setae along inner margin, distal article with one short seta at inner margin, one long and three stout terminal setae.

Female: The non-ovigerous females in the samples do not have any lateral carapace teeth, neither on frontal nor on pseudorostral lobe.

Remarks. The new species L. weddellensis is close to L. antarcticus and L. breidensis in terms of habitus shape and a long serrate dorsomedian line on the carapace. However, the extremities seem to be more slender in the new species than in L. antarcticus .

A comparison is given for the following characters: The row of dosomedian teeth almost reaches the end of the carapace with 19 teeth in males ( L. antarcticus with 22 teeth, L. breidensis with 12 teeth); one lateral carapace tooth at frontal and pseudorostral lobe (one or two teeth at both lobes in L. antarcticus , no teeth in L. breidensis ); number of setae at inner margin of uropod peduncle is one in the new species (six in L. antarcticus and breidensis ); first (basal) article of endopod is 3.4 times as long as distal article (2.1 times in L. antarcticus , nearly 3 in L. breidensis ); accessory flagellum of antenna 1 is almost as long as basal article of main flagellum (longer in L. antarcticus and L. breidensis ). In addition, L. breidensis has small teeth on the inner side of the anterolateral angle, whereas L. antarcticus and the new species L. weddellensis do not have such teeth.

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 20. Leucon (C.) weddelensis sp. n., habitus holotype, subadult male, scale bar: 0.5 mm.

FIGURE 21. Leucon (C.) weddelensis sp. n., A1: antenna 1, Mxp2: maxilliped 2, Mxp3: maxilliped 3, P1: pereiopod 1 (slightly damaged), P2: pereiopod 2; scale bars: 50 µm (Mxp2), 100 µm (A1), 200 µm Mxp3, P1, P2).

FIGURE 22. Leucon (C.) weddelensis sp. n., P3: pereiopod 3, P4: pereiopod 4, U: pleotelson and uropods; scale bars: 100 µm (P3, U) and 200 µm (P4).