Diphasia nigra (Pallas, 1766)

Diphasia nigra

Description: This hydroid is somewhat reminiscent of Diphasia alata in that the main stems are straight, robust and taper towards the apex of the colony. In life it is usually of a pale grey to red coloration, but when dried out it turns black, hence the specific name. The side branches are alternate and support alternate hydrothecae. The hydrothecae are tubular in shape and are attached to the side branch for approximately 4/5 of their length. The upper 1/5 being unattached with a slightly flared, smooth outer margin. The gonothecae are arranged on short pedicels. The female capsule is ovate in shape, and has four longitudinal lines that meet at the aperture of the capsule. The male gonothecae are much smaller than the females, and have four short, blunt spines surrounding the aperture, which are absent in females. A large, robust hydroid typically 150-200mm in height.

Habitat: A deep water circalittoral species found in moderate to strong tidal streams attached to bedrock or stable hard substrata.

Distribution: A rare species which occurs frequently on the east coast of Rathlin Island. Also known from south-west England, north-west France, the western English Channel with a single record from Northumberland.

Key Identification Features:

Distribution Map: NBN map : National Biodiversity Network mapping facility, data for UK.

WoRMS: Species record : World Register of Marine Species.

iNaturalist: Species account : iNaturalist World Species Observations database

 Picton, B.E. & Morrow, C.C. (2016). Diphasia nigra (Pallas, 1766). [In] Encyclopedia of Marine Life of Britain and Ireland. Accessed on 2024-06-24

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