Claus, 1874
Description
Marked sexual dimorphism in carapace size and shape [H.globosa-fem-lat; H.globosa-male-lat]. Female, carapace globose with both height and breadth being 70-80% of length. Rostrum small, clearly downturned. Right asymmetrical gland opening at mid-height on posterior margin. Male carapace more cylindrical, height being about half the length, width a little greater. In ventral aspect the developed shoulder vaults give slightly biconvex outline to the flanks [H.globosa-male-vent]. The rostrum is much larger than in female and straight.
Female, frontal organ differentiated, capitulum thin-walled, down-turned, stem extends to end of first podomere of first antenna [H.globosa-1]. First antenna characteristically bent, second podomere with anteriorly bent dorsal seta, four terminal sensory setae about 70% of length of "e" seta. Second antenna endopodite lacks a processus mamillaris, "a" and "b" setae on first podomere bare [H.globosa-2].
Male, frontal organ and first antenna similar to female, but capitulum and dorsal seta smaller [H.globosa-3]. Second antenna endopodite right-hand hook appendage curves smoothly throughout its length apart from two ill-defined angles, one sensory seta inserted at the base of the hook appendage [H.globosa-4].
Size
Female 2.0-2.30 mm, male 1.94-2.18 mm carapace length.
Depth range
Females and males are epipelagic, males are deep mesopelagic, all oceans. Off the British Isles it appears to be an epibenthic species associated with slope depths of around 1000 m.
Distribution North Sea
No information available.
World distribution
Known from all oceans mostly from latitudes <40°.
Remarks
Highly seasonal in its occurrences off Bermuda, which may account for its erratic appearances in more northerly waters. Bathymetric ranges of males differ greatly from those of the adult females and the juvenile stages. Off Bermuda females are common in the near surface waters between February and June; juveniles become dominant in April/May. Males occur at 600-800 m, and a few females occur at bathypelagic depths. Off southwest Ireland, adult females have been found to be common in slope waters at depths of 900-1400 m, just above the sea-bed. Müller (1906) recorded it as occurring as far north as 63°N. It is hard to reconcile these observations without further information as to whether this species is advected into the region, or has a highly seasonal life cycle.
[After Angel, 2000]