Gooday, A.J., Bowser, S.S. (2005). The Second Species of Gromia (Protista) from the Deep Sea: its Natural History and Association with the Pakistan Margin Oxygen Minimum Zone. Protist. 156: 113-126.

408309

Gooday, A.J., Bowser, S.S.

2005

156: 113-126.

Publication

We describe a gromiid protist Gromia pyriformis sp. nov., from bathyal depths on the Pakistan margin (NE Arabian Sea), an area characterised by a well-developed Oxygen Minimum Zone (OMZ). The new species is smaller (length usually o1mm) than the only other described deepsea gromiid species (Gromia sphaerica) or the well-known coastal species Gromia oviformis. Its identification as a gromiid is based on the test-wall ultrastructure. This includes (i) an outer wall (165—300nm thick) limited by an electron-opaque layer and perforated by pore structures which typically extend through its entire thickness, and (ii) inner ‘‘honeycomb membrane’’ structures which form a discontinuous sheet (18—20nm thick) lying parallel to the outer wall. An outermost glycocalyx (?75nm thick), not observed in other gromiid species, is also present and imparts a finely granular appearance to the outer test surface, as seen by Scanning Electron Microscopy (SEM). Numerous rod-shaped prokaryotes are attached to the exterior of the glycocalyx. Gromia pyriformis sp. nov. typically occurs above the sediment—water interface, attached to the large arborescent foraminiferan Pelosina sp. It is confined to a very narrow bathymetric zone (~1000- m water depth) in the lower portion of the OMZ, where bottom-water oxygen concentrations are ?0.2 ml l?1.

Northern Indian Ocean

Foraminifera

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