Leucon (L.) andeep, 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 : 45-48

Leucon (L.) andeep n.sp.

( Figures 32–34 )

Material. Holotype subadult male, ZMH: K 42951 ; 4 February 2002.

Type locality. Antarctica, western Weddell Sea , 60° 26.48 S 56° 04.00 W, 3954 m depth, ANT XIX, #43-E, epibenthic sledge .

Paratypes: Peninsula: ANT XIX #43 : 1 subadult male + 1 non-ovigerous female (dissected), 5 subadult males, 22 non-ovigerous females (mostly damaged), 14 mancas; W Weddell Sea: ANT XIX #46 : 1 subadult male, 2 subadult females (1 dissected), 5 mancas. ZMH: K 42952 .

Etymology. The new species is named “ andeep ” after the acronym of the Antarctic deep-sea expedition.

Diagnosis. Dorsomedian line of carapace serrate along more than half of its length with 12 teeth pointing upward, one single tooth close to the posterior margin of carapace; carapace longer than the free thoracic segments combined; ventral margin of pseudorostrum without teeth; antennal notch reaching behind the level of the anterior margin of the frontal lobe; basis of the anterior extremities like maxilliped 3, pereiopod 1 to 3 is equal in length or shorter than the rest of the appendages; uropod exopod shorter than endopod.

Description. Holotype, 4.3 mm long ( Fig.32 ).

Carapace without lateral teeth, longer than free thoracic segments, dorsomedian line serrate along more than half its length with 12 teeth pointing upward, one single tooth close to posterior margin of carapace; pseudorostral lobes meeting in front of ocular lobe, ending acute, moderately long, 0.2 times as long as carapace; siphonal tube short; ocular lobe reduced; eyes missing. Antennal notch small but distinct, behind level of anterior margin of the frontal lobe; anterolateral tooth not very pronounced; anteroventral margin of carapace serrate at least anteriorly. Integument smooth. Five free thoracic segments visible. Pleon longer than carapace and free thoracic segments combined. Pleotelson as wide as long, only slightly shorter than uropod peduncle.

Appendages: non-ovigerous female (paratype).

Antenna 1 ( Fig. 33 , A 1 ): relative length of peduncle articles 1 to 3: 46/29/25; geniculate between article 1 and 2; article 1 with simple seta at inner distal corner; article 2 with two simple setae at inner and one at outer distal corner; article 3 with one simple seta at outer and two compound setae at inner distal corner; accessory flagellum minute; main flagellum tri-articulated, basal article longest; two aesthetascs, one inserting at the penultimate, one at the terminal article; setae broken off.

Maxilliped 2 ( Fig. 33 , Mxp2): B/R ratio 0.5, relative length of articles I to D: 8/28/30/23/11; merus with one setulate setae at inner distal corner; carpus with seven setulate setae along inner margin; propodus with four simple setae along inner and three close to distal margin, one long setulate seta distally; dactylus with strong terminal seta, and seven simple setae along margin.

Maxilliped 3 ( Fig. 33 , Mxp3): B/R ratio 1.1, relative length of articles I to D: 8/21/35/21/14; basis produced at distal outer corner, with three long setulate setae, six shorter setulate setae along inner margin, fringe of setae along proximal inner margin; merus with one long setulate seta at outer distal corner and one short one at inner margin; carpus with four setae - one simple, three setulate - along inner margin, two setae - one simple, one setulate - at outer distal area; propodus with one setulate seta at proximal outer margin, two long simple setae at outer distal corner; dactylus with broken terminal seta, four simple setae subterminally; exopod present.

Pereiopod 1 ( Fig. 33 , P 1 ): broken off after basis; exopod present.

Pereiopod 2 ( Fig. 33 , P 2 ): B/R ratio 0.9, relative length of articles I to D: 5/24/32/16/24; merus and carpus with one strong tooth-like seta at outer distal corner, two setulate setae along inner margin in merus, one in carpus; dactylus with slender terminal seta, three simple setae subterminally, two simple setae along margins; exopod broken off in paratype.

Pereiopod 3 ( Fig. 34 , P 3 ): B/R ratio 1.3, relative length of articles I to D: 15/30/26/21/8; basis with three setulate setae along inner margin, one at outer distal corner, one hair-like seta at inner distal corner; merus with simple seta at outer distal corner; carpus with hair-like seta at inner distal corner; propodus with one hair-like and two strong but unfortunately broken setae at distal margin; dactylus minute, with only one hair-like seta visible, terminal seta broken off; exopod present.

Pereiopod 4 ( Fig. 34 , P 4 ): B/R ratio 1.3, relative length of articles I to D: 12/33/37/15/4; basis with four simple and four setulate setae, one of them at distal corner; ischium with two simple setae at distal margin; carpus with one long and strong simple seta at outer distal corner, propodus with one strong simple seta; minute dactylus with strong terminal and one hair-like seta.

Pereiopod 5 ( Fig. 34 , P 5 ): B/R ratio 0.9, relative length of articles I to D: 21/26/29/18/5; basis with one setulate and two simple setae; ischium with two simple setae; merus with one simple seta at outer distal corner; carpus with two longer simple setae and one setulate seta at distal margin; dactylus with long and strong terminal seta.

Uropod ( Fig. 34 , U): Peduncle shorter than endopod, inner margin with four stout setae; exopod slightly shorter than endopod; endopod bi-articulated, basal article with six stout cuspidate setae along inner margin, 2.9 times as long as distal article; distal article with six stout cuspidate setae along inner margin, two longer stout setae terminally, one slender and one short seta subterminally.

Remarks. The new species is close to L. (L.) adelae ( South Georgia) with respect to the position of the antennal notch lying behind the level of the anterior margin of the frontal lobe, the thorax being shorter than the abdomen, the absence of teeth at the basal articles of the maxilliped 3 and pereiopod 1, and the presence of the ischium of pereiopod 2. It differs from L. adelae in the carapace being longer than the free thoracic segments in the new species (equal in length in L. adelae ), the ventral margin of pseudorostrum having no teeth (three teeth in L. adelae ), no ridge ending with a denticle in the anterior third of carapace (with ridge and denticle in L. adelae ), antenna 1 having a geniculation between article 1 and 2 (no geniculation in L. adelae ), the uropod exopod being shorter than the endopod (longer than endopod in L. adelae ), and having more setae along the inner margins of the endopod articles in the new species than in L. adelae .

L. (L.) andeep sp. n. is close to L. (L.) quattuormulierum sp. n., but it differs from this species in the following characters: serration of dorsomedian line is shorter (longer in L. (L.) quattuormulierum sp. n.); deeper antennal notch (shallower in L. (L.) quattuormulierum sp. n.); no ventral teeth at pseudorostrum (two teeth ventrally at pseudorostrum in L. (L.) quattuormulierum sp. n.); uropod exopod equal in length to endopod (exopod shorter than endopod in L. (L.) quattuormulierum sp. n.); one single tooth close to the posterior margin of the carapace (no tooth close to the posterior margin in L. (L.) quattuormulierum sp. n.); the basis of the anterior extremities (maxilliped 3, pereiopods 1 to 3) is equal in length or shorter than the rest of the appendages in L. (L.) andeep sp. n., but clearly longer in L. (L.) quattuormulierum sp. n.

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 32. Leucon (L.) andeep sp. n., habitus holotype, subadult male, scale bar: 0.5 mm.

FIGURE 33. Leucon (L.) andeep sp. n., A1: antenna 1, Mxp2: maxilliped 2, Mxp3: maxilliped 3, P1: pereiopod 1 (broken after basis), P2: pereiopod 2; scale bars: 100 µm (A1, Mxp3) and 200 µm (Mxp2, P1, P2).

FIGURE 34. Leucon (L.) andeep sp. n., P3: pereiopod 3, P4: pereiopod 4, P5: pereiopod 5, U: pleotelson and left uropod; scale bars: 100 µm (P4) and 200 µm (P3, P5, U).