Leucon (C.) grandidentatus, 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 : 36-40

Leucon (C.) grandidentatus sp. n.

( Figures 26–28 )

Material. Holotype subadult male, ZMH: K 42947 ; 30 March 2005.

Type locality. Antarctica, Peninsula , 62° 32.52’ S 64° 35.49’ W, 2525 m depth, ANDEEP III, #154-E, epibenthic sledge .

Paratypes: Peninsula: ANDEEP III #154-S: 1 ovigerous female (dissected); W Weddell Sea: ANDEEP III #110-E: 1 subadult female. ZMH: K 42948 .

Etymology. The new species is named after the large teeth at the anterior dorsomedian part of the carapace.

Diagnosis. Dorsomedian serration with seven large and 11 smaller teeth reaching posterior margin of carapace; no teeth laterally at carapace, only one ventrally at pseudorostrum.

Description. Holotype, 5.8 mm long ( Fig. 26 ).

Carapace longer than free thoracic segments; dorsomedian denticulation reaching end of carapace; anterior denticulation with seven teeth large and 11 teeth diminishing towards the posterior margin, last tooth after small gap, no teeth laterally on carapace; pseudorostral lobes long, slightly less (factor 0.4) than half of carapace measured from ocular lobe to posterior margin of carapace; directed forwards, without dorsal teeth or hair-like setae along margins but two teeth at basis of pseudorostrum; siphonal tube not longer than pseudorostrum; ocular lobe reduced; eyes missing. Antennal notch in level with anterior margin of frontal lobe, not pronounced; anterolateral margin above antennal notch, with two larger and three very small (only visible in higher magnification) teeth; anterolateral tooth not produced; anteroventral margin of carapace slightly serrate (about five to eight teeth). Integument of carapace smooth, scaly structure only on abdomen. Five free thoracic segments visible. Pleon as long as carapace and free thoracic segments combined. Pleotelson slightly longer than wide; 0.8 times as long as uropod peduncle.

Appendages: female (paratype).

Antenna 1 ( Fig. 27 , A 1 ): relative length of peduncle articles 1 to 3: 32/37/31; slightly geniculate between article 1 and 2; fringe of setae along article 1 lower margin; article 2 with few fine setae distally; accessory flagellum much longer than basal article of main flagellum; main flagellum tri-articulated; both flagella with strong simple setae terminally.

Maxilliped 2 ( Fig. 27 , Mxp2): B/R ratio 0.4, relative length of articles I to D: 7/28/32/22/10; basis with fringe of setae along and one setulate seta at distal inner margin; merus with tuft of hair-like setae at outer margin; carpus with nine setulate setae along inner margin, tuft of hair-like setae at proximal inner margin; propodus with one long setulate seta at proximal part, nine strong simple setae along inner and distal margin: dactylus with strong terminal seta, three hair-like setae subterminally, fringe of hair-like short setae at inner margin.

Maxilliped 3 ( Fig. 27 , Mxp3): B/R ratio 0.9, relative length of articles I to D: 9/20/33/20/18; basis produced distally, with one short and three long setulate setae, five setulate setae along inner margin; merus with one tooth and one long setulate seta at outer distal corner, two short setulate setae at inner margin; carpus with two short setulate setae along inner margin, one tooth at inner distal corner; propodus with one tooth, one setulate seta and two hair-like setae at outer distal corner; dactylus with terminal seta longer than dactylus, two simple setae subterminally; exopod present, basal article with three teeth.

Pereiopod 1 ( Fig. 27 , P 1 ): broken off after basis; exopod present, basal article with five teeth along outer margin.

Pereiopod 2 ( Fig. 27 , P 2 ): B/R ratio 0.7, relative length of articles I to D: 5/27/31/13/24; merus with two cuspidate setae at proximal part; carpus with two strong and three slender simple setae distally, one simple seta and one very short one proximally; dactylus with terminal seta slightly shorter than dactylus and propodus combined, terminal and three subterminal setae serrulate, one setulate and three simple setae more proximally; exopod broken off, not figured.

Pereiopod 3 ( Fig. 28 , P 3 ): B/R ratio 1.3, relative length of articles I to D: 24/22/29/20/5; basis with broken seta; ischium with two simple setae, one of them broken; merus with one simple and one setulate seta; carpus with three long setulate setae; propodus with one long simple seta; dactylus with terminal seta broken off; exopod present, broken off (not figured).

Pereiopod 4 ( Fig. 28 , P 4 ): B/R ratio 1.4, relative length of articles I to D: 33/23/26/13/5; setae at basis mostly damaged; ischium damaged during dissection, with one long setulate seta; merus with two setulate setae; carpus with one long and one short setulate seta at outer distal corner; propodus with one long simple seta distally; minute dactylus with long terminal seta.

Pereiopod 5 ( Fig. 28 , P 5 ): B/R ratio 1.4, relative length of articles I to D: 25/27/27/18/3; basis with one long setulate seta at distal margin, ischium with one long setulate seta at distal corner; merus with two long setulate setae at distal margin; carpus with three long setulate setae at distal and one at proximal area; propodus with one long simple seta distally; minute dactylus with terminal seta longer than carpus to dactylus combined.

Uropod ( Fig. 28 , U): peduncle shorter than endopod, with one short seta at inner margin; exopod shorter than endopod; endopod bi-articulated, basal article with six strong cuspidate setae along inner margin, 2.5 times as long as distal article; distal article with five strong cuspidate setae along inner margin, terminal seta short and stout, one slender and one short simple seta subterminally.

Female ( Fig. 26 ): With less dorsomedian teeth, one very small tooth ventrally on pseudorostrum.

Remarks. There are five species in the subgenus Crymoleucon with a very long pseudorostrum, as mentioned above: L. macrorhinus (Mediterranean) , L. serrulirostris ( Mozambique Channel), L. tener (northern Atlantic), L. savulescui (Peru-Chile Trench) and L. nudirhinus ( Angola Basin).The first three mentioned species differ from the new species in the presence of teeth or long setae at the pseudorostrum or at the carapace respectively. The species most similar to the new species are L. savulescui , which differs from the new species in having the dorsomedian serration in a double row, and L. nudirhinus . In fact the new species is very similar to L. nudirhinus , having a long unarmed pseudorostrum and the length proportion of basis to carpus of pereiopod 2 being 2.2 in the new species and 2.1 in L. nudirhinus ; even the length proportions of the uropods are similar in both species.

However, the new species differs in some characters from L. nudirhinus : the dorsomedian serration reaches the posterior margin of the carapace in the new species (male) (only to the middle of the carapace in L. nudihinus female); the teeth of the dorsomedian line are much larger in the new species than in L. nudirhinus ; the maxilliped 3 basal article of exopod has three teeth, merus and carpus have one tooth each in the new species (no teeth in the Angola Basin species) and the armature of the females’ uropods is different: only one seta at the inner margin of the peduncle (three setae in L. nudirhinus ); the basal article of endopod has six setae at the inner margin (five in L. nudirhinus ); and five setae along the inner margin of the distal article (one seta in L. nudirhinus ). The differences to the species described before, L. longirhinus sp. n., are given above.

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 26. Leucon (C.) grandidentatus sp. n., habitus holotype, subadult male (below), scale bar: 0.5 mm, dissected female, paratype (above).

FIGURE 27. Leucon (C.) grandidentatus sp. n., A1: antenna 1, Mxp2: maxilliped 2, Mxp3: maxilliped 3, P1: pereiopod 1 (broken at basis), P2: pereiopod 2; scale bars: 100 µm (Mxp2) and 200 µm (A1, Mxp3, P1, P2).

FIGURE 28. Leucon (C.) grandidentatus sp. n., P3: pereiopod 3, P4: pereiopod 4, P5: pereiopod 5, U: pleotelson and right uropod; scale bars: 100 µm (P5) and 200 µm (P3, P4, U).