Atractophora is a small red alga, mucilaginous in nature and known only from a few isolated sites in the British Isles. There is only one species of this genus in the British Isles.

In brief

• This species has been found at only four localities in Northern Ireland: Rathlin Island and Ballygalley Head in County Antrim and a southern shore of Strangford Lough and Greenore Point in County Down
• It grows in the shallow sublittoral to 20m
• The best time to see it is probably July to September
• It is rare in the UK, being only of western distribution
• No threats are known save damage to the habitat.

Species description: Only the gametangial phase of the plant is known, tetransporangia are unknown. The gametangial thallus is erect, red and grows to a height of 10cm. It is attached by a small basal disc and is much branched with downgrowing filaments which enclose the axes. The spreading filaments grow irregularly in a diffuse manner.

Life cycle: The carpospores germinate and develop directly to the gametangial phase. A tetrasporangial phase is unknown.

Similar species: Many other finely-branched algae are similar such as: Antithamnion, Dasya and Spyridia. Microscopic examination is required for identification.

How to see this species: There are only four records from Northern Ireland: County Antrim, from Rathlin Island and Loughan Bay and in County Down, at Greenore Point and near the entrance of Strangford Lough. The species is to be found only in the sublittoral to 20m depth and is best looked for by scuba-diving.

Current status: It is recorded from only four sites in Northern Ireland: Rathlin Island and Ballygalley Head in County Antrim and a southern shore of Strangford Lough and Greenore Point in County Down. This is mainly a western species with records from the Inner Hebrides of Scotland, Galway and Cork in the south of Ireland, a few records from Wales and south-western England.

Why is this species a priority in Northern Ireland?

• It is scarce, with Northern Ireland being the UK stronghold for the species.

Threats: As far as is known, there is no threat and no note of any decline. Any damage to the sublittoral will endanger this species and others.

Action:

• The status of Atractophora hypnoides will be surveyed and monitored and appropriate conservation action undertaken if required.

Objectives: No relevant action.

Conservation:

• Rathlin Island is protected as a SAC and Strangford Lough as a Marine Nature Reserve.

Distribution Map from NBN: Atractophora hypnoides at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Atractophora hypnoides at iNaturalist World Species Observations database.

WoRMS: Atractophora hypnoides at World Register of Marine Species. Accepted name: Atractophora hypnoides P.Crouan & H.Crouan, 1848. AphiaID: 145767.

Literature:

Morton, O. (1994). Marine algae of Northern Ireland. Ulster Museum, Belfast.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Rhodymeniophycidae; Atractophorales; Atractophoraceae; Atractophora

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Osborne Morton (2026). Atractophora hypnoides. P.Crouan & H.Crouan, 1848. [In] Priority species, Marine Biodiversity Portal NI. https://www2.habitas.org.uk/marbiop-ni/priorityaccounts.php?item=ZM1910. Accessed on 2026-07-28