Kyphocalanus

Kyphocalanus sp. 1.

( Figs 6–8 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

Material examined. Dissected adult female, body length 1.82 mm. Collected on 28 July 2000, above the sea bed at abyssal depths ( 5390m) in the South Atlantic ( 16º18’S 05º27’E).

Specimen is deposited at the Zoological Museum Hamburg ( ZMH), University of Hamburg.

Description. Female. Prosome 5.1 times as long as urosome.

Rostrum with two strong rami ( Fig. 6 View FIGURE 6 A–B). Cephalosome and somite 1 and somites 4 and 5 of prosome separate; posterior corners as triangular lobes ( Fig. 6 View FIGURE 6 A, C-D). Genital double-somite with attached spermatophore. Caudal rami with 4 terminal setae, 2 lateral broken, and 1 ventral seta, dorsal seta not located.

Antennule broken posterior to ancestral segment XII. Setation as in type species.

Antenna ( Fig. 7 View FIGURE 7 A) coxa with 1 seta, basis without seta, exopod of 8 free segments with 0, 1, 1, 1, 1, 1, 1, and 3 setae, about 2.3 times as long as endopod; first endopodal segment without seta, second with 3 plus 6 setae. Mandible ( Fig. 7 View FIGURE 7 B), gnathobase long and slender, cutting edge with 4 larger, acute teeth and a row of small teeth plus dorsal seta; basis with 2 setae, proximal one with basal part knife handle-like; exopod 5-segmented with 5 setae, distal one distinctly smaller; endopod segment 1 without setae, segment 2 with 9 setae.

Maxillule ( Fig. 7 View FIGURE 7 C), praecoxal endite with 3 terminal setae; coxal endite with 2 setae; proximal basal endite without seta, distal basal endite with 1 seta; endopod with 5 setae; exopod with 7 setae; coxal epipodite with 9 setae.

Maxilla ( Fig. 8 View FIGURE 8 A–B), proximal praecoxal endite with 2 setae; distal praecoxal endite with 2 setae; proximal coxal endite with 1 seta; distal coxal endite with 2 setae; proximal basal endite with 1 spine; distal basal endite plus endopod with 8 long and thick worm-like sensory setae.

Maxilliped ( Fig. 7 View FIGURE 7 D), syncoxa with 1 worm-like, comparably thin and short sensory seta on proximal praecoxal lobe, 2 long and thick worm-like setae setae on middle lobe, distal praecoxal lobe without setae; coxal lobe with 1 seta. Basis with 3 setae. Endopod of six segments with 2, 4, 2, 2, 2+1, and 4 setae.

Swimming legs. P1 ( Fig. 8 View FIGURE 8 C), basis with medial distal seta significantly curved with setules; endopod 1- segmented without lateral lobe; exopod segments 1, 2, and 3 with lateral spines, the proximal spine is the longest, distal spine is the shortest; spine of exopod segment 1 exceeding base of following spine, spine of exopod segment 2 not reaching base of following spine.

P2–P4 broken.

P5 3-segmented, exopod with 1 terminal attenuation and 1 subterminal inner spine, inner spine about three times length of terminal attenuation; spinules present only on right and left coxa distolaterally.

Remarks. Kyphocalanus sp.1 differs from the type species in: i) smaller size (1.82 mm vs 2.24 mm in K. atlanticus ); ii) shorter endopod of antenna (length ratio of exopod and endopod as 2.3:1, vs 1.8 in K. atlanticus ); iii) 3 setae on inner lobe of antenna endopod segment 2 ( vs 4 setae in K. atlanticus ); iv) 1 seta on maxilla proximal coxal endite ( vs 2 setae in K. atlanticus ); v) P1 lateral spine of exopod segment 1 the longest compared to those of exopod segments 2 and 3 ( vs this spine is the shortest in K. atlanticus ); vi) spinules present only on the right coxa of P5 ( vs spinules present on coxa, basis and exopod of P 5 in K. atlanticus ).