Divacuma kurambio, Mühlenhardt-Siegel, Ute & Lavrenteva, Anna V., 2015

Mühlenhardt-Siegel, Ute & Lavrenteva, Anna V., 2015, Selected species of the family Diastylidae (Cumacea, Peracarida, Crustacea) from the deep-sea of the NW Pacific, Zootaxa 3956 (3), pp. 345-373 : 351-356

Divacuma kurambio sp. n.

( Figs 4–6 )

Material. Holotype ovigerous female, ZMH: K 44233 ; (coll. 3.8.2012);

Type locality. NW Pacific, Kurile Kamchatka abyssal plains, 46° 13.56' N 155° 33.57' E, 4859–4863 m, cruise 223 with RV “Sonne” ( KuramBio ), station #2-10 (EBS #4), gear: epibenthic sledge.

Paratypes: #9-12: 1 preparatory female; ZMH: K-44256; #10-12: 1 manca; ZMH: K 44234 ; 1 ovigerous female (dissected) ZMH: K 44235 ; #11-9: 1 manca; ZMH: K-44257

Etymology. The new species is named after the acronym of the expedition.

Diagnosis. Pleonite 6 second longest abdominal segment after pleonite 5, almost as long as pleonite 5; telson short, preanal part stout and cylindrical, postanal part short; pereiopod 5 shorter than basis of pereiopod 4; uropod exopod longer than endopod; one pair of subterminal telsonic setae, one pair of strong terminal telsonic seta.

Description. Holotype, ovigerous female (ZMH: K 44233 ), 9.7 mm long ( Fig. 4 ).

Carapace with few hair-like setae and two denticles in posterior dorsal part, 3.4 times as long as free thoracic segments; pseudorostral lobes short, directing slightly upwards; siphonal tube very little protruding; ocular lobe linguiform; eye lenses missing.

Antennal notch missing; anterolateral tooth not protruding; anteroventral margin of carapace crenulated.

Integument whitish, slightly translucent.

Five free thoracic segments visible, 0.3 times length of carapace.

Pleon long and slender, 2.4 (2.5 in dissected paratype) times as long as carapace and free thoracic segments combined; surface with small denticles and hair-like setae;

Pleonite 6 second longest abdominal segment after pleonite 5, almost as long as pleonite 5.

Telson ( Fig. 6 , U) short, 0.4 times as long as pleonite 6, concave in the middle from lateral side, preanal part stout and cylindrical, postanal part short; with two terminal setae, one pair of lateral cuspidate setae and one pair of lateral hair-like setae.

Appendages: ovigerous female, 10.3 mm long (paratype ZMH: K 44235 ).

Antenna 1 ( Fig. 5 , A1): relative length of peduncle articles 1 to 3: 41/26/33; article 1 with fringe of setae along inner margin, a pappose seta on inner distal corner and a simple seta on outer distal corner; article 2 with fringe of hair-like setae along outer margin, two long simple setae on inner distal corner; article 3 with six simple setae; accessory flagellum four-articulated, shorter than basal article of main flagellum; main flagellum four-articulated, terminal article shortest; two aesthetascs, one inserting at penultimate article, the second terminally at ultimate article; short hair-like seta inserting at first, second and third article of main flagellum.

Maxilliped 2 ( Fig. 5 , Mxp2): B/R ratio not given, basis broken during dissection, relative length of articles I to D: 7/20/32 /27/14; basis with one strong pappose seta on inner distal corner, on outer distal corner one simple and one serrate setae; merus with one strong pappose and one simple setae; carpus with five plumose setae along inner margin, two pappose setae on outer distal corner; propodus with one long and three short pappose setae, one strong seta on outer distal corner broken; dactylus with one strong terminally and two simple setae subterminally.

Maxilliped 3 ( Fig. 5 , Mxp3): B/R ratio 0.7, relative length of articles I to D: 9/19/29 /23/20; basis with fringe of hair-like setae along outer margin, five pappose setae along inner margin, three long pappose setae on outer distal corner; ischium with one pappose seta; merus with one tooth and one pappose seta on inner distal corner; carpus with two pappose setae along inner margin, three pappose setae along distal margin, one broken seta on inner distal corner; propodus with three pappose setae on inner distal corner, two simple setae distally; dactylus with one strong terminally (unguis) and two subterminally simple setae, exopod was broken off in dissected paratype.

Pereiopod 1 ( Fig. 5 , P1): B/R ratio and relative length of articles I to D not given, extremity broken after basis; basis with three denticles and 17 hair-like simple setae; exopod broken off in dissected paratype.

Pereiopod 2 ( Fig. 6 , P2): B/R ratio 0.4, relative length of articles I to D: 6/ 9/38/19 /28; long and slender extremity; all articles with hair-like simple setae, except ischium; basis with five, merus with two, carpus with five, propodus with six, dactylus with 11 laterally, three terminally; exopod present, not figured.

Pereiopod 3 ( Fig. 6 , P3): B/R ratio1.7, relative length of articles I to D: 11/29/42 /10/8; all articles with hairlike simple setae, except ischium; basis with 11, merus with three, carpus with three thin laterally and two strong distally, propodus with one strong, and dactylus with a hair-like seta medially and a strong seta terminally; rudimentary exopod present.

Pereiopod 4 ( Fig. 6 , P4): B/R ratio 2.2, relative length of articles I to D: 12/28/34 /14/12; all articles from basis to carpus with hair-like simple setae; basis with 14, ischium with one and merus with two, carpus with three and two strong distally, propodus and dactylus each with one strong simple setae; rudimentary exopod present.

Pereiopod 5 ( Fig. 6 , P5): shorter than basis of P4; B/R ratio 1.2, relative length of articles I to D: 13/25/ 37/15/ 10; all articles from basis to carpus with hair-like simple setae; basis with five, ischium with one, merus with three, carpus with one and two strong simple setae distally, propodus with one strong simple seta distally, dactylus with a hair-like seta medially and a strong seta terminally.

Uropods ( Fig. 6 , U), peduncle longer than endopod (1.5 times) but shorter than pleonite 6 (0.7 times); seven cuspidate setae along inner margin, two simple setae along outer margin; exopod 1.3 times as long as endopod, with oblique articulation between basal and distal article, nine hair-like setae along margin, one terminal and one subterminal setae; endopod three-articulated, terminal article longest, article 1 with one cuspidate and one long, hair-like seta, article 2 with one longer hair-like median and a cuspidate and a hair-like seta distally, article 3 with two longer hair-like, two hair-like subterminally and a stronger simple seta terminally.

Male unknown.

Distribution. Kurile Kamchatka abyssal plains, 4895–5397 m.

Remarks. The species resembles Divacuma tuerkayi Mühlenhardt-Siegel 2003 from the Angola Basin and the Weddell Sea ( Mühlenhardt-Siegel, 2014) with the long pleon, pleonite 6 being as long as pleonite 5, the short telson, the globose carapace and short free thoracic segments, long and slender pereiopods 1 and 2. It can be distinguished from D. tuerkayi in the characters listed in Table 2 .

Unfortunately no male was available to check the number of pleopods, which is one in the genus Divacuma . Even though no males were available to check the number of pleopods, the new species is erected for the Kurile Kamchatka deep sea based on morphological differences in the females and also because of the geographical distance between the two forms.

Figures

FIGURE 4. Divacuma kurambio n. sp.; habitus holotype (ZMH: K 44233); ovigerous female; lateral view (above), carapace in dorsal view (below); scale bar: 1 mm.

FIGURE 5. Divacuma kurambio n. sp.; dissected paratype (ZIM: K 44235); A 1: antenna 1; Mxp 2: maxilliped 2; Mxp 3: maxilliped 3; P 1: basis of pereiopod 1; scale bars: 0.5 mm (A 1, Mxp 3, P 1) and 0.1 mm (Mxp 2).

FIGURE 6. Divacuma kurambio n. sp.; dissected paratype (ZIM: K 44235); P 2: pereiopod 2; P 3: pereiopod 3; P 4: pereiopod 4; P 5: pereiopod 5; U: pleonite 6, telson and left uropod; scale bars: 0.5 mm.

Tables

TABLE 2. Comparison of the two Divacuma species (discriminating characters in bold).

	Divacuma tuerkayi	Divacuma kurambio n. sp.
Female size	8 mm	9.7 mm
Ventral margin of carapace	serrated	crenulated
Carapace to total body length	5.5	4.9
Thoracic segments visible	4	5
Length proportion, thoracic segments to carapace	0.5	0.3
Pleon length to pereion	2.9	2.5
Uropod peduncle to telson	1.9	2.1
Uropod peduncle, number of setae	5 inner, 2 outer margin	7 inner, 2 outer margin
Uropod exopod to endopod length	1.2	1.3
Uropod exopod to peduncle	0.9	0.8
Uropod endopod to peduncle	0.8	0.7
Basis of pereiopod 1, number of teeth	5 (male)	3 (female)