Deevey, 1978a
Diagnosis
Small subrectangular species (A. versicula Habitus 1, A. versicula Habitus 3). Dorsal and ventral margins almost parallel before curving symmetrically to form the posterior margin. Rostrum down-turned in both sexes. In ventral aspect, the maximum width is level with the insertions of the adductor muscles and carapace tapers both anteriorly and posteriorly (A. versicula Habitus 2, A. versicula Habitus 4). Clear sculpturing of fine striae parallel the ventral edge, are vertical round the sides of the rostrum, but are obliquely longitudinal along the dorsal margin. Right asymmetrical gland opening two-fifths the way down the posterior margin, and the left one-fifth. The frontal organ is unsegmented in both sexes, curves slightly downwards and usually terminates in a fine point which may have secondary spinules at its tip (A. versicula 1, A. versicula 3). First antennae with long reflexed sensory setae. Second antenna endopodite of both sexes with long hirsute "a" and "b" setae (A. versicula 2, A. versicula 4). The caudal furca has six pairs of rather straight spine setae.
Remarks
Together with A. striata , this species forms a separate species grouping which possibly merits generic status. Its description, from material collected in the Pacific sector of the Southern Ocean, and subsequent identification from deep water in the Atlantic, suggests that there is a widespread faunistic link between the abyssopelagic waters of all the oceans.
Distribution
Described from the Southern Ocean; taken from the equator to 49°N in the North Atlantic, whenever sampling has been carried out at depths greater than 2000-2500m. 1 (R.R.S. Discovery Map).
Type specimens
Holotype, a male dissected on slides. National Museum of Natural History, Smithsonian Institution (NMNH 169061)
Type locality
39°56'S, 107°24'W, Eltanin sample 1375; depth 1000-2000m; date 10th December 1965; gear a Bébathypelagic plankton sampler.