Leucon (C.) longirhinus, 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 : 32-36

Leucon (C.) longirhinus sp. n.

( Figures 23–25 )

Material. Holotype non-ovigerous female, ZMH: K 42945 ; 10 March 2002.

Type locality. Antarctica, western Weddell Sea , 65° 00.85’ S 43° 03.03’ W, 4678 m depth, ANT XIX, #135, epibenthic sledge .

Paratypes: Peninsula: ANT XIX #105 : 2 non-ovigerous females (1 damaged, 1 dissected), ANT XIX #129 : 1 non-ovigerous female; E Weddell Sea: ANT XV #130: 1 juvenile male, 2 subadult females, 4 females with empty oostegites, 2 mancas; ANDEEP III #78: 1 male, 3 mancas. ZMH: K 42946 .

Etymology. The new species is named “ longirhinus ” because of the long pseudorostrum.

Diagnosis. Pseudorostrum more than half as long as remainder of carapace, with two teeth ventrally; two teeth laterally at posterior part of carapace; accessory flagellum longer than basal article of main flagellum; three to four teeth above the antennal notch; uropod endopod longer than exopod; the proportion endopod to peduncle is 0.8 to 0.9.

Description. Holotype, 4.8 mm long ( Fig. 23 ).

Carapace longer than free thoracic segments; dorsomedian line serrate with about 10 teeth up to 2/3 of the carapace; pseudorostral lobes long, 0.6 times as long as carapace measured from ocular lobe to the posterior margin, with two teeth ventrally at pseudorostrum; siphonal tube longer than pseudorostrum; ocular lobe reduced; eyes missing. Antennal notch indistinct, shallow; anterolateral tooth not pronounced, three to four teeth above antennal notch at anterolateral margin of carapace; anteroventral margin of carapace not strongly serrate.

Integument smooth and shiny, white coloured, weakly calcified. Five free thoracic segments visible. Pleon slightly longer than carapace and free thoracic segments combined. Pleotelson as long as wide, anal valves visible from above, slightly produced between uropod peduncles, 0.7 times as long as uropod peduncle.

Appendages: female (paratype).

Antenna 1 ( Fig. 24 , A 1 ): relative length of peduncle articles 1 to 3: 45/36/20; slightly geniculate between article 2 and 3; accessory flagellum longer than basal article of main flagellum; main flagellum tri-articulated; both flagella with long stout setae terminally.

Maxilliped 2 ( Fig. 24 , Mxp2): basis broken during dissection, relative length of articles I to D: 6/30/32/20/12; basis and merus with setulate seta distally; carpus with seven setulate setae along inner margin; propodus with one long setulate seta inserting proximally, eight simple setae along inner margin, one at outer distal corner; dactylus with terminal seta as long as dactylus, three setae subterminally.

Maxilliped 3 ( Fig. 24 , Mxp3): B/R ratio 0.7, relative length of articles I to D: 10/16/37/21/16; basis distally produced, with five long setulate setae, three setulate setae along inner margin; merus with long setulate seta and one tooth at outer distal corner; carpus with four setulate setae along inner margin, one tooth at inner distal corner; propodus with simple seta distally, dactylus with long terminal and two simple setae subterminally; exopod basal article with three teeth.

Pereiopod 1 ( Fig. 24 , P 1 ): B/R ratio 0.5, relative length of articles I to D: 9/15/28/31/17; basis with one simple and three setulate setae at inner margin, two setulate, two simple setae and one tooth at distal margin; ischium and merus with one hair-like seta; carpus with five hair-like setae along margins; propodus with six hair-like setae along margins; dactylus with terminal seta as long as dactylus, four strong and two hair-like setae subterminally; exopod basal article with two teeth.

Pereiopod 2 ( Fig. 25 , P 2 ): B/R ratio 0.7, relative length of articles I to D: 7/23/30/13/27; basis with few hairlike and two setulate setae along inner margin; carpus with three simple and two hair-like setae; dactylus with four setulate setae terminally and two setulate and three simple setae along margins; exopod present.

Pereiopod 3 ( Fig. 25 , P 3 ): B/R ratio 1.5, relative length of articles I to D: 18/23/32/20/7; basis with one setulate seta at distal inner third; merus with one long setulate seta at distal inner corner; carpus with four setulate setae at outer distal corner; propodus with one simple seta at outer distal corner; minute dactylus with terminal seta as long as carpus, propodus and dactylus combined; exopod present.

Pereiopod 4 ( Fig. 25 , P 4 ): B/R ratio 1.6, relative length of articles I to D: 14/24/34/20/8; basis with one simple seta distally; merus with two long setulate setae at distal corner; carpus with two long setae at inner and one long and one short at outer distal corner; propodus with one long simple seta distally; dactylus with long terminal seta, one hair-like seta subterminally.

Pereiopod 5: damaged during dissection.

Uropod ( Fig. 25 , U): peduncle with three to four simple and few hair-like setae along inner margin, shorter than rami; exopod shorter than endopod; endopod bi-articulated, basal article with six to seven cuspidate setae along inner margin, two times as long as distal article; distal article with three cuspidate setae along inner margin, terminal seta short and stout, one short seta subterminally at outer distal corner.

Remarks. The new species Leucon longirhinus is close to the species described in the following, L. grandidentatus sp. n., with respect to the long pseudorostrum, the uropod endopod being longer than the exopod and the proportion endopod to peduncle being 0.8 to 0.9 and the accessory flagellum being longer than the basal article of the main flagellum. It differs from L. grandidentatus sp. n. in the number of teeth above the antennal notch (3 to 4 in the new species, 2 in L. grandidentatus sp. n.); the length proportion of pseudorostrum to carapace measured from ocular lobe to posterior margin is 0.6 in the new species but 0.4 in L. grandidentatus sp. n. There are teeth at the basis of pereiopod 1 in L. longirhinus sp. n. (0 in L. grandidentatus sp. n.), 2 teeth under the pseudorostrum (1 in L. grandidentatus sp. n.)

The other species with a long pseudorostrum in the subgenus Crymoleucon are L. macrorhinus Fage, 1951 , L. nudirhinus Mühlenhardt-Siegel, 2005 , L. savulescui Petrescu, 1992 , L. serrulirostris Ledoyer, 1988 and L. tener Hansen, 1920 . Out of these species only L. serrulirostris has (four) ventral teeth at the pseudorostrum. In the new species the pseudorostrum is straight, no teeth at the dorsal margin of the pseudorostrum and about 10 teeth along the anterior 2/3 of the dorsomedian line of the carapace (curved pseudorostrum, seven dorsal teeth at the pseudorostrum, two teeth at the anterior part of the dorsomedian line of the carapace in L. serrulirostris ).

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 23. Leucon (C.) longirhinus sp. n., habitus holotype, non-ovigerous female, scale bar: 0.5 mm.

FIGURE 24. Leucon (C.) longirhinus sp. n., A1: antenna 1, Mxp2: maxilliped 2, Mxp3: maxilliped 3, P1: pereiopod 1; scale bars: 200 µm.

FIGURE 25. Leucon (C.) longirhinus sp. n., P2: pereiopod 2, P3: pereiopod 3, P4: pereiopod 4, U: pleotelson and uropods; scale bars: 200 µm.