Leucon (M.) complexus, 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 : 52-57

Leucon (M.) complexus sp. n.

( Figures 38–40 )

Material. Holotype ovigerous female, ZMH: K 42955 ; 27 February 2005.

Type locality. Antarctica, eastern Weddell Sea , 86° 03.84’ S 20° 31.39’ W, 4928 m depth, ANDEEP III, #88-E, epibenthic sledge .

Paratypes: Peninsula: ANT XIX #99 : 1 subadult male; ANDEEP III #154: 1 subadult female, damaged; W Weddell Sea: ANT XIX #134 : 1 subadult female, heavily damaged; ANT XIX #136 : 1subadult female (two pieces); ANT XIX #137 : 1 female, heavily damaged; ANDEEP III #94: 1 subadult male; ANDEEP III #102: 1 subadult female, 1 manca; ANDEEP III #121: 1 subadult male, 1 ovigerous female, 5 subadult females (1 dissected), 1 manca; ANDEEP III #142: 1 subadult male, 2 ovigerous females, 1 subadult female (broken), 2 mancas; E Weddell Sea: ANDEEP III #78: 1 subadult male, 2 subadult females, 2 mancas; ANDEEP III #80: 1 subadult female (dissected); Cape Basin: ANDEEP III #16: 2 subadult males, 3 non-ovigerous females (1 dissected), 3 mancas. ZMH: K 42956 .

Etymology. The new species is named “ complexus ” to indicate the possibility of a species complex owing to the variability in the number of teeth dorsally and ventrally at the pseudorostrum as well as along the dorsomedian line.

Diagnosis. Few dorsomedian teeth and up to 11 small teeth anterolaterally on carapace; teeth dorsally and ventrally at pseudorostrum.

Description. Holotype, 6.7 mm long ( Fig. 38 ).

Carapace slightly shorter than free thoracic segments, three dorsomedian teeth, anterolaterally at least 11 small teeth; pseudorostral lobes meeting in front of ocular lobe, 0.4 times as long as carapace, with five dorsal and two ventral pairs of teeth at pseudorostral margins; three teeth laterally at pseudorostrum but often broken off; siphonal tube long; ocular lobe reduced, eyes missing. Antennal notch small, with three large teeth at anterolateral margin above antennal notch; anterolateral tooth not defined but three small teeth instead; anteroventral margin of carapace serrate. Integument with scaly structure in higher magnification. Five free thoracic segments visible. Pleon longer than carapace and free thoracic segments combined. Pleotelson wider than long, 0.7 times as long as uropod peduncle; anal valves visible from above.

Appendages: female (paratype, ANDEEP III # 121 -E) .

Antenna 1( Fig. 39 , A 1 ): relative length of peduncle articles 1 to 3: 26/38/36; long setulate setae: one at article 2, four at article 3; accessory flagellum equal in length to basal article of main flagellum, with three long simple setae at distal margin; main flagellum tri-articulated, with four long simple setae at distal article.

Maxilliped 2 ( Fig. 39 , Mxp2): B/R ratio 0.4, relative length of articles I to D: 5/27/32/21/14; basis and merus with one strong setulate seta at inner distal corner; carpus with five pairs of setulate seta along inner margin, two setulate setae along distal margin; propodus with seven simple setae along inner and distal margin, one setulate seta at outer distal corner; dactylus with terminal seta longer than dactylus, one setulate seta at outer half.

Maxilliped 3 ( Fig. 39 , Mxp3): B/R ratio 0.6, relative length of articles I to D: 9/21/26/21/23; basis with two teeth along distal inner margin, four setulate setae along inner margin, two long setulate setae at outer distal corner; ischium with one strong tooth at inner margin; merus with one tooth at inner and two teeth along outer margin, one very long setulate seta at outer distal corner; carpus with five setulate setae along inner margin; propodus with two setulate setae at distal margin; dactylus with five simple setae at terminal margin and two setulate setae at outer half; exopod with one tooth distally at basal article.

Pereiopod 1( Fig. 39 , P 1 ): B/R ratio 0.3, relative length of articles I to D: 9/13/31/35/13; basis with four setulate setae and one tooth along inner margin, one simple and one setulate seta at outer distal corner; merus with two setulate setae and one tooth at outer margin, one short simple seta at inner margin; carpus with two simple and two setulate setae along outer, three simple setae along inner margin; propodus with one setulate and three simple setae along inner margin, one setulate, one hair-like and three simple setae along outer margin; dactylus with three strong simple setae along inner margin, one terminal and one subterminal strong seta, two hair-like setae at outer distal third; exopod with one tooth distally at basal article.

Pereiopod 2 ( Fig. 40 , P 2 ): B/R ratio 0.7, relative length of articles I to D: 4/15/40/13/29; basis with row of five tiny teeth along inner margin; merus with two setulate setae and two tiny teeth along outer margin; carpus with two setulate setae each at outer proximal and inner distal margin and one setulate seta at distal margin; articulation carpus-propodus broken in paratype; dactylus with long terminal and three shorter subterminal setae, two simple setae along inner margin and one setulate seta more proximally at inner and outer margin; exopod present.

Pereiopod 3 ( Fig. 40 , P 3 ): B/R ratio 1.6, relative length of articles I to D: 13/32/28/13/13; basis with three setulate setae along inner margin; ischium and merus with long setulate seta at distal inner corner; carpus with long simple seta at outer and inner distal corner, one shorter simple seta at outer distal margin; propodus with one long simple seta at inner distal corner; dactylus with terminal seta slightly longer than carpus, merus and dactylus combined; exopod present.

Pereiopod 4 ( Fig. 40 , P 4 ): B/R ratio 0.8, relative length of articles I to D: 17/26/26/19/12; ischium with setulate and simple seta at inner distal region; merus with simple seta at half of inner margin; carpus with three long setulate setae along outer margin; propodus with one long simple seta at outer distal corner; dactylus with terminal seta as long as carpus, propodus and dactylus combined.

Pereiopod 5 ( Fig. 40 , P 5 ): B/R ratio 0.9, relative length of articles I to D: 5/21/28/31/15; basis with two setulate setae along inner margin; carpus with one setulate, one simple and one hair-like seta along inner margin; propodus with three long and strong setulate setae along outer margin and one hair-like seta at distal margin; dactylus with terminal seta longer than carpus, propodus and dactylus combined.

Uropod ( Fig. 40 , U): Peduncle shorter than rami, with four short cuspidate setae along inner margin; exopod similar in length to endopod; endopod bi-articulated, basal article with three setae along inner margin and one hairlike seta at outer distal corner, 2.5 times as long as distal article; distal article with one shallow tooth, two short cuspidate setae along inner margin, one strong terminal seta and a long simple seta subterminally.

Male: similar to female, but with more (three larger, four smaller) dorsomedian teeth than in ovigerous female; few (three) tiny teeth laterally at anterior part of carapace.

Remarks. Most of the known Leucon (Macrauloleucon) species, e.g. the known Macrauloleucon species from Antarctic regions L. (M.) weddelli Ledoyer, 1993 and L. (M.) parasiphonatus Mühlenhardt-Siegel, 1994 , do not have ventral teeth along the pseudorostrum. The new species has one or two ventral teeth like L. (M.) spinulosus Hansen, 1920 from the Arctic region and resembles that species also in having the accessory flagellum of the first antenna equal in length to the basal article of the main flagellum. L. (M.) brigittehilbigae Mühlenhardt-Siegel, 2005 and L. (M.) dentirostris Mühlenhardt-Siegel, 2005 (both from the Angola Basin) have 3 or 4 ventral teeth respectively and differ from the new species in the accessory flagellum being shorter than the basal article of the main flagellum. The new species differs from L. spinulosus in:

● having only few dorsomedian teeth at the carapace (dorsomedian anterior third serrate in L. spinulosus ); ● the anterior margins of the free thoracic segments 1 to 3 being unserrate in the new species (with serrations in

L. spinulosus , at least in the figure given by Hansen, 1920, but not in the figures given by Petrescu, 1994 for the specimens from the Peru Basin); ● the article 3 of the first antenna being shorter than article 2 in the new species (longer in L. spinulosus ).

The new species has a wide distribution from the Cape Basin, eastern and western Weddell Sea to the Antarctic Peninsula region. There is a variation in the number of teeth dorsally (two, three and four) and ventrally (one or two) on the pseudorostrum, at the articles of pereiopod 1 and maxilliped 3 and along the dorsomedian line (four large, two small in one female from the Peninsula; two large - in some specimens additionally five small - in the Weddell Sea specimens, six small in the Cape Basin specimens). The new species may be a species complex of very similar species, or the difference in the number of teeth is due to the sexual and age differences of the various specimens.

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 38. Leucon (M.) complexus sp. n., habitus holotype, ovigerous female, scale bar: 0.5 mm.

FIGURE 39. Leucon (M.) complexus sp. n., A1: antenna 1, Mxp2: maxilliped 2, Mxp3: maxilliped 3, P1: pereiopod 1; scale bars: 100 µm (A1, Mxp2,) and 200 µm (Mxp3, P1).

FIGURE 40. Leucon (M.) complexus sp. n., P2: pereiopod 2, P3: pereiopod 3, P4: pereiopod 4, P5: pereiopod 5, U: pleotelson and uropods; scale bars: 100 µm (P3, P5) and 200 µm (P2, P4, U).