Bathycalanus bucklinae n. sp.

(Fig. 46, 77–80)

Type locality. 25.082o S, 9.584o W.

Material examined. ANTXXIV/1, Stn 8, MOC10, 2062– 2990 m, 1♀ (11.2 mm), holotype.

Type specimens. Deposited in the collection of the National Institute of Water and Atmospheric Research, New Zealand: Holotype female: NIWA 85233 (1 vial, 2 slides).

Morphological description. Following description based on holotype specimen from ANTXXIV/1, Stn 8. As for genus with following specific level features.

Female (Fig. 77 A–E). Total length 11.2 mm. Anterior margin of head in dorsal view produced into rounded protrusion dorsal to base of rostrum and extending into pair of small divergent spine-like processes. In dorsal view, posterior border of pedigerous somite 5 extending into transparent, asymmetrical lappets, slightly longer on right. Genital double-somite symmetrical in dorsal view, widest at about anterior one third, 1.21 times longer than wide, seminal receptacles not observed.

Antennule (Fig. 78) extending beyond caudal rami by about 4 segments. Lengths of antennule segments (µm) as follows. Measurements taken along posterior border of each segment but two (posterior (shortest) and anterior) measurements taken of ancestral segment I. I (320, 655); II–IV (399); V (209); VI (266); VII (330); VIII (367); IX (367); X–XI (695); XII (525); XIII (530); XIV (650); XV (818); XVI (916); XVII (978); XVIII (1071); XIX (1101); XX (1278); XXI (1296); XXII (897); XXIII (855); XXIV (934); XXV (877); XXVI (458); XXVII (823); XXVIII (47). Anterior and posterior borders of ancestral segments XVI–XXI smooth. Hair sensillum on ancestral segment II not accompanied by macula cribrosa (Fig. 78 E).

Antenna (Fig. 79 A) exopod segment IV with short seta extending to distal border of segment VIII and bearing short setules.

Maxillule (Fig. 79 D) praecoxal arthrite with 13 setae including 2 on posterior surface and 2 setae on anterior surface, one of them small; coxal endite without setae, basal endites 1 and 2 with 2 and 4 setae respectively; endopod segments with 2 (subequal), 2 (subequal), 5+1 smaller anterior surface seta.

Maxilliped (Fig. 79 F) syncoxal endite 4 longest, toothed seta extending half way along endopod segment 2.

Leg 1 (Fig. 77 F) exopod with articulation between exopod segments 2 and 3 well developed; distolateral corner of endopod segment 1 bilobed.

Male. Unknown.

Etymology. This species is named for Professor Ann Bucklin, University of Connecticut, who conceived and led the CMarZ programme.

Distribution. Bathycalanus bucklinae n. sp. is an upper abyssopelagic species taken from the type locality south of the Walvis Ridge over the Namibia Abyssal Plane in the South Atlantic at greater than 2000 m depth (Fig. 46, Table 1).

Species comparisons. This species is related to Ba. richardi in that it has a pair of small anterior spine-like processes on the head. Nevertheless, Ba. bucklinae can be distinguished from any other Bathycalanus species by a combination of having 1) pedigerous somite 5 with long asymmetrical posterolateral lappets; 2) body somites smooth and without pustules; 3) a genital double-somite with its widest part, in dorsal view, at one third the distance from the anterior border; 4) female antennule ancestral segment II hair sensillum not accompanied by macula cribrosa; and 5) 4 setae on the second basal endite of the maxillule (Table 10).