Leucon (Leucon) quattuormulierum, 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 : 40-44

Leucon (Leucon) quattuormulierum sp. n.

( Figures 29–31 )

Material. Holotype non-ovigerous female, ZMH: K 42949 ; 30 January 2002.

Type locality. Antarctica, western Weddell Sea , 60° 39.19’ S 53° 56.85’ W, 2893 m depth, ANT XIX, #46-S, epibenthic sledge .

Paratypes: Peninsula: ANT XIX #42 : 81 subadult males, 5 adult males, 201 subadult females, 16 ovigerous females, 92 mancas (2 males and 1 female dissected) + 12 specimens for molecular genetics; ANDEEP III #154: 1 damaged female; W Weddell Sea: ANT XIX #46 : 5 non-ovigerous females (1 dissected), 4 mancas. ZMH: K 42950 .

Etymology. The new species is named after four colleagues who tirelessly sampled during the ANDEEP expeditions: Angelika Brandt, Brigitte Ebbe, Kathrin Linse and Gisela Weigel.

Diagnosis. Anterior ¾ of the dorsomedian line of carapace serrate, with 14 teeth directing forwards and getting successively smaller; no lateral teeth at carapace; two teeth ventrally on pseudorostrum; antennal notch shallow, reaching backwards to level of anterior margin of frontal lobe; the basis of the anterior extremities (maxilliped 3, pereiopods 1 to 3) is clearly longer than the rest of the appendages; pleotelson slightly produced between uropod peduncles.

Description. Holotype, 5.4 mm long ( Fig. 29 ).

Carapace longer than free thoracic segments combined; anterior ¾ of the dorsomedian line serrate with 10 large and four smaller teeth (only visible in higher magnification), no tooth close to the posterior margin of carapace, no lateral teeth on carapace; pseudorostral lobes meeting in front of ocular lobe, two teeth ventrally on pseudorostrum; siphonal tube short; ocular lobe reduced; eyes missing. Antennal notch shallow, reaching backwards to level of anterior margin of frontal lobe; anterolateral tooth not pronounced, but clearly discernable; anteroventral margin of carapace serrate. Integument smooth. Five free thoracic segments visible. Pleon longer than carapace and free thoracic segments combined. Pleotelson slightly longer than wide, slightly produced between uropod peduncles; 0.9 times as long as uropod peduncle; anal valves visible from above.

Appendages: male (paratype).

Antenna 1 ( Fig. 30 , A 1 ): relative length of peduncle articles 1 to 3 not given, article 1 broken; geniculated between article 1 and 2; article 2 distally with two simple setae, article 3 with three broom setae and one simple seta; accessory flagellum minute; main flagellum tri-articulated, two aesthetascs, one inserting at the penultimate article, one inserting at the terminal article.

Maxilliped 2 ( Fig. 30 , Mxp2): B/R ratio 0.6, relative length of articles I to D: 9/26/31/21/13; basis with strong setulate seta at inner distal corner; merus with tooth and one strong setulate seta at inner margin, outer margin with fringe of hair-like setae; carpus with seven setulate setae along inner margin; propodus with seven simple setae along inner margin, one long setulate seta inserting at proximal third of the article; dactylus with strong terminal seta, one hair-like and two simple setae subterminally.

Maxilliped 3 ( Fig. 30 , Mxp3): B/R ratio 1.5, relative length of articles I to D: 8/19/34/24/15; basis produced distally, with one short and three long setulate setae, six setulate setae along inner margin; merus with one long setulate seta at outer distal corner, one short setulate seta at inner margin; carpus with three short setulate setae along inner and outer margin; propodus with two setulate and four simple setae at distal margin; dactylus with terminal seta longer than dactylus, two simple setae subterminally; exopod present.

Pereiopod 1 ( Fig. 30 , P 1 ): B/R ratio 0.5, relative length of articles I to D: 7/15/28/27/23; basis with seven setulate setae along inner margin and two strong tooth-like setae at distal margin; carpus with two short simple setae at distal margin; propodus with one simple seta at proximal third, three simple setae distally; dactylus with three simple setae along margin, terminal seta short (broken?), four simple setae subterminally; exopod present.

Pereiopod 2 ( Fig. 30 , P 2 ): B/R ratio 1.4, relative length of articles I to D: 4/26/26/17/28; basis with six setulate setae along inner margin, two small ones distally; ischium minute; merus with one setulate and one simple seta at outer margin, three setulate and one short simple seta along distal margin; carpus with one strong and two short simple setae distally; dactylus with three simple setae distally, terminal seta broken off (?); exopod present.

Pereiopod 3 ( Fig. 31 , P 3 ): B/R ratio 2.0, relative length of articles I to D: 13/26/29/26/6; basis with row of eight setulate setae along inner margin and three setulate setae along distal margin; merus with one simple seta at outer distal corner; carpus with one short and one long simple seta, the latter at distal margin; propodus with one long simple seta at distal margin; dactylus with terminal seta longer than propodus and dactylus combined; exopod present.

Pereiopod 4 ( Fig. 31 , P 4 ): B/R ratio 1.4, relative length of articles I to D: 9/31/31/22/6; basis with two simple setae distally; merus with one simple seta at inner distal corner; carpus with one simple seta at outer margin and two long simple setae distally; propodus with one simple seta distally; dactylus with terminal seta slightly shorter than carpus to dactylus combined; exopod present.

Pereiopod 5 ( Fig. 31 , P 5 ): B/R ratio 1.0, relative length of articles I to D: 13/29/33/23/6; basis with three setulate setae along margins; merus with two simple setae along inner margin; carpus with two long and strong simple setae at outer distal corner; propodus with one strong simple seta at outer distal corner; dactylus minute, with terminal seta longer than propodus and dactylus combined.

Uropod ( Fig. 31 , U): peduncle longer than rami, with five setae along inner margin; exopod equal in length to endopod; endopod bi-articulated; basal article with eight stout cuspidate setae along inner margin and one at outer distal corner, 2.4 times as long as distal article; distal article with six strong cuspidate setae along inner margin and one at outer distal corner, terminal seta strong, a slender seta subterminally.

Subadult male: With two developing pairs of pleopods; similar to female but with fewer dorsomedian teeth.

Adult male: With antenna 2 reaching beyond free thoracic segments, no dorsomedian serration.

Remarks. The new species differs from the two other species of Leucon (Leucon) from the Southern Ocean L. adelae Petrescu, 1991 and L. assimilis, Sars 1887 in the following characters:

L. adelae has a ridge ending in a denticle laterally at the carapace (the new species has neither ridge nor denticle); the antennal notch ends behind the level of the anterior margin of the frontal lobe (in the new species the antennal notch is not behind the anterior margin of the frontal lobe); the dorsomedian line of the carapace has no serration, but only one tooth (a dorsomedian serration with 14 teeth is present in the new species).

L. assimilis has the dorsomedian line of the carapace serrate up to the end of the carapace with an interruption close to the hind margin and four lateral teeth at the lower margin of the frontal lobe (the new species has the dorsomedian line only serrate up to ¾ of the carapace and no lateral teeth).

The new species L. quattuormulierum is close to L. (L.) andeep sp. n. (described in the following), but it differs in the following characters: the serration at the dorsomedian line of the carapace is a slightly longer than in L. (L.) andeep sp. n.; the shape of the antennal notch is open and it reaches to the level of the anterior margin of the frontal lobe in L. quattuormulierum sp. n., but in L. (L.) andeep sp. n. it is behind the level of the anterior margin of the frontal lobe; the new species has ventral teeth on the pseudorostrum and L. (L.) andeep sp. n. does not; the uropod exopod is shorter than the endopod in L. (L.) andeep sp. n., but equal in length in the new species; it has no tooth close to the posterior margin of the carapace like in L. (L.) andeep sp. n. The basis of the anterior extremities like maxilliped 3, pereiopods 1 to 3 is clearly longer than the rest of the appendages in L. quattuormulierum sp. n., but equal or shorter in L. (L.) andeep 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 29. Leucon (L.) quattuormulierum sp. n., habitus holotype, non-ovigerous female, scale bar: 0.5 mm.

FIGURE 30. Leucon (L.) quattuormulierum sp. n., A1: antenna 1, Mxp2: maxilliped 2, Mxp3: maxilliped 3, P1: pereiopod 1, P2: pereiopod 2; scale bars: 100 µm (A1, Mxp2) and 200 µm (Mxp3, P1, P2).

FIGURE 31. Leucon (L.) quattuormulierum sp. n., P3: pereiopod 3, P4: pereiopod 4, P5: pereiopod 5, U: pleotelson and right uropod; scale bars: 100 µm (U) and 200 µm (P3, P4, P5).