Omorius curvispinus, Markhaseva & Schulz, 2007

Markhaseva, Elena L. & Schulz, Knud, 2007, New species of Brodskius, Rythabis, and Omorius (Crustacea: Calanoida) from deep Antarctic waters, Journal of Natural History 41 (13 - 16), pp. 731-750 : 743-747

publication ID	https://doi.org/ 10.1080/00222930701297772
persistent identifier	https://treatment.plazi.org/id/444A8794-7B69-FFB8-FE31-FF03FC4FFEB9
treatment provided by	Felipe
scientific name	Omorius curvispinus
status

Treatment

Genus Omorius Markhaseva and Ferrari, 2005

Omorius curvispinus sp. nov.

( Figures 8–11 View Figure 8 View Figure 9 View Figure 10 View Figure 11 )

Material examined

Holotype: adult female, poor condition, dissected, body length 1.86 mm ( ZMH K-41171). Scotia Sea, 60 ° 38 9 S, 53 ° 57 9 W, station 46-7, supranet, 30 January 2002, above the sea bed at depths of 2889–2893 m. GoogleMaps

Description

Adult female. Total length 1.86 mm; prosome about 4.6 times longer than urosome. Rostrum without filaments ( Figure 8B, C View Figure 8 ). Cephalosome and pediger 1 and pedigers 4 and 5 separate ( Figure 8A, D, E View Figure 8 ). Right posterior corner of prosome rounded with small knob ventrally ( Figure 8E View Figure 8 ), left posterior corner probably folded back ( Figure 8D View Figure 8 ). In dorsal view, genital double-somite slightly swollen at mid-length; lateral surfaces of genital double-somite with denticles; spermathecae small, oblong ( Figure 8D, E, G View Figure 8 ). Caudal rami with four terminal setae, one small dorsal and one small ventral seta ( Figure 8D, F, H View Figure 8 ).

Antennules broken ( Figure 9A View Figure 9 ), eight proximal free segments intact, armature as follows: I—3s, II–IV—6s+2ae, V—1s+1ae+?, VI—2s, VII—1s+1ae+?, VIII—2s+1ae, IX—1s+?, X– XI—2s+?.

Antenna ( Figure 9B–D View Figure 9 ): coxa with one seta; basis with two setae, one very long extending to bases of subdistal setae of endopodal segment 1; endopodal segment 1 with two setae, endopodal segment 2 with seven and eight setae. Exopod eight-segmented, with 1, 2, 2, 1, 1, 1, 1, and 3 setae; third proximal segment small, incompletely separate from second segment.

Mandible ( Figure 9E–G View Figure 9 ): gnathobase with tooth-like knob on posterior face and wide cutting edge, with eight blunt teeth and one seta; basis with three setae; exopod of five segments with 1, 1, 1, 1 and terminal setae broken; endopod segment 1 with two setae, endopod segment 2 with nine setae.

Maxillule ( Figure 9H, J View Figure 9 ): praecoxal endite with nine terminal and four posterior setae; terminal setae 1–2 and 5–9 large (from proximal to distal), setae 3–4 small and slightly curved.( Figure 9J View Figure 9 ); coxal endite with two setae; coxal epipodite with nine setae; proximal basal endite with two setae; distal basal endite with three setae; endopod with seven setae; exopod with four setae and small spinules distally.

Maxilla ( Figure 10A, B View Figure 10 ): proximal praecoxal endite with four setae and short triangular attenuation; distal endite with three setae; proximal coxal endite with three setae, distal coxal endite with three setae, one long, thick and spine-like; proximal basal endite with four setae, one thick, spine-like and one worm-like sensory seta; all endites with small spinules distally; distal basal endite plus endopod with eight sensory setae, of these five worm-like and three brush-like.

Maxilliped ( Figure 10C, D View Figure 10 ): syncoxa with one seta on praecoxal endite, two setae on middle endite (one heavily sclerotized, spine-like and strongly curved), and one seta slightly curved in proximal third on distal praecoxal endite; coxal endite with three setae; four rows of spinules present: proximally; between medial and distal praecoxal endites; adjacent to coxal endite proximally; along distal edge of coxal endite. Basis with row of spinules proximally and three medial and two distal setae. Endopod five-segmented with 4, 4, 3, 3+1 and 4 setae.

P1 ( Figure 10E View Figure 10 ): coxa with row of small denticles along distal outer edge; basis with tiny distolateral seta and mediodistal seta on anterior face; endopod one-segmented, comparatively long and extending to anterior margin of exopod segment 2, with three medial and two terminal setae; lateral lobe small and triangular lacking denticles, spinules present along distolateral edge of endopod. Exopod three-segmented, segment 1 with lateral spine, segment 2 with lateral spine and medial seta, segment 3 with lateral spine, terminal spine and three medial setae; lateral spines of exopod segments 1 and 2 covered with denticles, spine of segment 3 longest.

P2 ( Figure 11A View Figure 11 ): coxa with medial seta; basis with group of small denticles on posterior surface near base of endopod; endopod two-segmented, segment 1 with one medial seta, segment 2 with two medial, two terminal and one lateral setae and ornamented with denticles on posterior surface; exopod segments 2 and 3 detached, segment 1 with one medial and one lateral seta.

P3 ( Figure 11B View Figure 11 ): coxa with medial seta; basis with row of denticles distally; endopod segment 1 with one medial seta; exopod segment 1 with one medial and one lateral seta; exopod and endopod segments 2 and 3 detached.

P4 ( Figure 11C View Figure 11 ): coxa with medial seta; coxa and basis with large patches of denticles on posterior surface; endopod segment 1 with one medial seta and with posterior denticles; exopod segment 1 with one medial, one lateral seta and sparse posterior denticles, exopod and endopod segments 2 and 3 broken.

P5 ( Figure 9I View Figure 9 ): three-segmented, all segments with denticles on posterior surface; exopod (distal segment) with one medial spine (broken), one lateral, one short subterminal and one terminal attenuation (broken).

Male. Unknown.

Etymology

The specific name is derived from the Latin curvus meaning curved and spinus meaning spine and relates to the strongly sclerotized, spine-like curved setae of the maxillipedal syncoxa.

Remarks

Omorius curvispinus is the second species attributed to the genus. It differs from O. atypicus Markhaseva and Ferrari, 2005 (1) in a slightly greater size (1.85 versus 1.56 mm in O. atypicus ); (2) by a strongly curved seta on the medial praecoxal endite of the maxilliped (slightly curved in O. atypicus ); (3) presence of an exceptional long seta on antenna basis extending to bases of endopod segment 1 setae (much shorter in O. atypicus ); (4) oblong spermathecae (rounded); (5) genital double-somite slightly swollen at mid-length (not swollen); (6) P1 endopod with lateral lobe lacking denticles (with small denticles); (7) antenna exopod segment 3 small, partly fused to segment 2 (separate).