Leucon (Macrauloleucon) weigmanni, 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 : 48-52

Leucon (Macrauloleucon) weigmanni sp. n.

( Figures 35–37 )

Material. Holotype non-ovigerous female, ZMH: K 42953 ; 27 January 2002.

Type locality. Antarctica, Peninsula , 59° 39.88’ S 57° 35.94 W, 3690 m depth, ANT XIX, #42, epibenthic sledge .

Paratypes: Peninsula: ANT XIX #42 : 3 ovigerous females, 2 small (4 mm) non-ovigerous females, 1 manca; ANT XIX #114 : 2 females (1 dissected); W Weddell Sea: ANDEEP III #121: 2 non-ovigerous females, 3 mancas; E Weddell Sea: ANT XV #133: 1 manca, ANDEEP III #78: 1 male (broken), 2 subadult females, 2 mancas. ZMH: K 42954 .

Additional material. ANDEEP III #121: 1 subadult male, 2 ovigerous females, 2 non-ovigerous females (with postero-lateral teeth on pereionites).

Etymology. The new species is named after my dear colleague Simon Weigmann, with many thanks for his valuable help.

Diagnosis. Five to seven teeth at dorsomedian line of carapace; a maximum of three teeth laterally on carapace; two tiny teeth on pseudorostrum; posterior margin of free thoracic segments smooth; article 3 of first antenna peduncle shorter than article 2.

Description. Holotype, 5.1 mm long ( Fig. 35 ).

Carapace including pseudorostral lobes 1.4 times as long as free thoracic segments, with about nine tiny teeth at anterolateral sides, dorsomedian line in anterior fourth with five to seven teeth; pseudorostral lobes meeting in front of ocular lobe, 0.2 times as long as carapace, with one to two small teeth on dorsal margin, at least one long hair-like seta at terminal end; siphonal tube long; ocular lobe reduced; eyes missing. Antennal notch small, anterolateral margin above the antennal notch heavily serrate with five teeth; anterolateral tooth blunt, not produced; anteroventral margin of carapace serrate. Integument brittle, scaly structure in higher magnification. Five free thoracic segments visible. Pleon only slightly shorter than carapace and free thoracic segments combined. Pleotelson wider than long, 0.5 times as long as uropod peduncle, anal valves visible from above.

Appendages: ovigerous female (paratype).

Antenna 1 ( Fig. 36 , A 1 ): relative length of peduncle articles 1 to 3: 24/42/34; geniculate between article 2 and 3; article 2 with one setulate seta; article 3 with two setulate setae at distal margin; accessory flagellum as long as basal article of main flagellum; main flagellum tri-articulated, second article of main flagellum with one long and one short simple seta at distal margin, one aesthetasc, terminal article with three long and two shorter simple setae and one aesthetasc.

Maxilliped 2 ( Fig. 36 , Mxp2): B/R ratio 0.4, relative length of articles I to D: 10/28/30/19/13; basis (broken) with one strong setulate seta at distal margin; merus with one setulate seta at inner margin and row of hair-like setae along outer margin; carpus with eight setulate setae along inner margin and one long setulate seta at distal corner; propodus with four simple setae along inner and distal margin; dactylus with strong and short terminal seta and two simple setae subterminally.

Maxilliped 3 ( Fig. 36 , Mxp3): B/R ratio 0.8, relative length of articles I to D: 7/18/30/23/21; basis distally produced, with four long setulate setae, five setulate setae and one tooth along inner margin; ischium with one tooth at inner margin; merus with two teeth and one very long setulate seta at outer margin, along inner margin two fine setulate setae; carpus with five fine setulate setae along inner margin, distally one tooth, one moderately long simple seta and one tooth at outer distal corner; propodus with three setulate setae at inner margin, one simple seta at outer distal corner; dactylus with terminal seta longer than dactylus, two simple setae subterminally; exopod present.

Pereiopod 1 ( Fig. 36 , P 1 ): B/R ratio 0.2, relative length of articles I to D: 7/15/30/36/13; basis with two setulate and two hair-like setae; ischium with one setulate at outer distal and one hair-like seta at inner distal corner; merus with one long setulate seta at outer distal corner; carpus with few hair-like setae along margins, distally with two setulate setae; propodus with four setulate setae: one at the proximal outer and one at the distal inner margin, two along the inner and outer margins, two hair-like setae in a short distance to the setulate seta at the inner margin; dactylus with three simple setae along distal inner margin, terminal seta longer than dactylus, two simple setae subterminally; exopod present.

Pereiopod 2 ( Fig. 36 , P 2 ): B/R ratio 0.6, relative length of articles I to D: 2/14/50/14/21; basis with three setulate setae along inner margin; ischium hardly detectable; merus with one setulate seta at outer margin; carpus with two setulate setae along outer margin, one setulate and one hair-like seta along inner margin, two longer simple setae at distal margin; dactylus with five simple setae at distal margin, longer than dactylus, two shorter simple setae along inner and outer margins; exopod present.

Pereiopod 3 ( Fig. 37 , P 3 ): B/R ratio 1.4, relative length of articles I to D: 12/33/28/19/7; ischium with long setulate seta at inner distal corner; merus with one micro-setulate and one short simple seta at inner margin; carpus with one long simple seta at outer proximal margin, two long simple setae at outer distal corner; propodus with long simple seta at outer distal corner; dactylus with terminal seta (broken off) and two fine setae subterminally.

Pereiopod 4: damaged, not figured.

Pereiopod 5 ( Fig. 37 , P 5 ): Length proportions not given due to artefact of curvature; long simple setae at carpus and propodus distal parts; dactylus with terminal seta (broken off) and two fine setae subterminally.

Uropod ( Fig. 37 , U): Peduncle shorter than rami, three stout cuspidate setae along inner margin; exopod slightly longer than endopod; endopod bi-articulated, basal article 1.8 times as long as distal article, seven strong cuspidate setae along inner margin; distal article with two strong cuspidate setae along inner margin; terminal seta short and stout, long simple seta subterminally.

Remarks. The new species Leucon (M.) weigmanni is similar to Leucon (M.) weddelli Ledoyer, 1993 with respect to the short serration of the dorsomedian line of the carapace and the teeth at the lateral sides of the carapace. However, in the new species there are up to twelve tiny teeth on the carapace side (seven in L. weddelli ) and three to eight at the dorsomedian line (two in L. weddelli ). The new species has two tiny teeth on the pseudorostrum, which is not armed in L. weddelli . L. weddelli has tiny teeth at the posterior margin of the free thoracic segments, which are mostly not present in the new species.

The new species is also similar to the species L. (M.) complexus sp. n. (described in the following), but this species does have ventral teeth along the pseudorostrum, and L. (M.) weigmanni sp. n. does not.

The number of teeth varies in L. (M.) weigmanni sp. n.:

● in the dorsomedian line of the carapace: Peninsula and western Weddell Sea: 3 (young) - 8 (ovigerous and non-ovigerous) in females, 6–9 in juvenile males; eastern Weddell Sea: 7–8 in females and young males;

● number of teeth on the pseudorostrum: Peninsula: 2–4 in females, 2 in juvenile males; western Weddell Sea: 2–4 in females, 1 in juvenile males; eastern Weddell Sea: 2–3 in females, 2–4 in males;

● number of teeth at the anterolateral margin of the carapace above the antennal notch Peninsula: 3–6 in males and females; western Weddell Sea: 2–4 in males and females; eastern Weddell Sea: 2–4 in males and females.

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

FIGURE 35. Leucon (M.) weigmanni sp. n., habitus holotype, non-ovigerous female, scale bar: 0.5 mm.

FIGURE 36. Leucon (M.) weigmanni sp. n., 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 37. Leucon (M.) weigmanni sp. n., P3: pereiopod 3, P5: pereiopod 5, U: pleotelson and right uropod; scale bars: 100 µm (P3, P5) and 200 µm (U).