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 ).