Deevey, 1978a
Diagnosis
One of the longer species in the genus. In the female, dorsal and ventral margins are almost parallelly curved (A. gastrodes Habitus 1); posterior margin is strongly arched and the anterior region is swollen; in ventral aspect the flanks are almost parallel for half the length, but are bluntly rounded anteriorly and taper to a shape point posteriorly (A. gastrodes Habitus 2). The males are very much shorter and the straight region of the ventral margin is inclined so that the carapace tapers strongly posteriorly (A. gastrodes Habitus 3). In neither sex can the rostrum be seen in ventral aspect (A. gastrodes Habitus 2, A. gastrodes Habitus 4). The right asymmetrical gland opens a third the height up the posterior margin (A. gastrodes Habitus 1, A. gastrodes Habitus 3), below its maximum curve. The left gland opens just below the posterior end of the hinge. The caudal furca carries eight pairs of hook setae.
Remarks
Other than the cucullata group with their strong sculpturing and carapace processes, the only Archiconchoecia species which are as large as this species are A. bifurcata and A. poulseni. It differs from the latter in having eight rather than seven claw setae on the caudal furca, and from the former by the carapace height being less than half the length (in A. bifurcata the height is almost 60% of the length). Deevey, 1978a describes other differences related to the second antenna and the setation of the fifth and sixth limbs. Neither of these similar species have been taken in UK waters.
Distribution
Discovery Collection material includes species taken over bathymetric ranges of 800-2700m from 30-60°N in the North Atlantic. There appears to be an ontogenetic migration with the juveniles occurring at shallower depths than the adults. 1, 2, 3 (R.R.S. Discovery Map).
Type specimens
Holotype, a female dissected on a slide in the National Museum of Natural History, Smithsonian Institution (NMNH 171292)
Type locality
32°10'N, 64°30'W, Station "S" in the Sargasso Sea off Bermuda; depth 1000-1500m; date 19th February 1979; a vertical tow.