Bathycalanus eximius Markhaseva 1983

Bathycalanus eximius Markhaseva, 1983

(Fig. 46)

Bathycalanus eximius Markhaseva, 1983, pp 197–198, fig. 87.

Type locality. Kurile-Kamchatka Trench.

Material examined. Dr Elena Markhaseva, Institute of Zoology, St Petersberg, Russia, kindly re-examined the holotype material of this species and has augmented her original description with the following additional observations.

Morphological description. As for genus with following specific level features.

Female. Total length 11.9 mm. Anterior margin of head in dorsal view with low projection bearing pair of small spine-like processes. In lateral view posterior corners of pedigerous somite 5 symmetrical, rounded, but slightly pointed in dorsal view. Genital double-somite markedly swollen and symmetrical in dorsal view, wider than long, with lateral surfaces ornamented with large spinules.

Antennule extending beyond caudal rami by 4–6 segments. Anterior and posterior borders of ancestral segments XVI–XXI smooth.

Antenna exopod ancestral segment III with small seta and segment IV with short seta extending beyond segment VIII, no sign of setae on ancestral segments I and II.

Maxillule praecoxal arthrite with 14 setae including 3 on posterior surface and 1 longer and 1 smaller on anterior surface; coxal endite without setae, basal endites 1 and 2 with 2 and 4/5 setae respectively; endopod segments with 2, 2, 5+1 small anterior surface seta; basal exite with 1 seta, epipodite with 7 long and 2 short, reduced setae.

Maxilliped syncoxa endite 4 longest seta extending beyond distal border of endopod segment 2; endopod segments 2–6 with 4 (including 3 small), 3 (including 2 small), 3 (including 2 small) + 1, 4 setae (2 large and 2 very small of which one on outer border), respectively.

Leg 1 exopod segment 3 with 1 outer border spine.

Male. Unknown

Distribution. Bathycalanus eximius is probably a deep abyssopelagic species and is known only from the Kurile-Kamchatka Trench in a haul with 7040 metres of wire out at approximately 5000 m depth.

Species comparisons. Bathycalanus eximius is distinguished from all other Bathycalanus by (Table 10): 1) having a very swollen genital double-somite bearing lateral spinules; and 2) having the second basal endite of the maxillule with 4 setae.