G. devoniensis is a species of seaweed which was considered, until recently, synonymous with G. crenulatus; however, it has now been transferred to Ahnfeltiopsis devoniensis. This leaves G. crenulatus and G. griffithsiae as separate species in the genus Gymnogongrus.

In brief

• One record from Strangford Lough which requires confirmation
• It is to be found on the coast in the lower littoral or subtidal rocky shore
• To be found anytime, as far as is known
• It is considered a priority species because there is only one record in Northern Ireland
• Threatened by general danger to the coast which endangers all algae.

Species description: Ahnfeltiopsis devoniensis is a small red marine alga growing to only several centimetres in length from a disc-like holdfast. It forms a medium-sized flattened frond with regular dichotomous branching. The branches have parallel sides. The reproductive structures (cystocarps) are internal.

Life cycle: In Ireland, England, northern France and Spain the lifecycle appears to be a succession of diploid female plants forming spores apomictically (that is, without reduction division). However, male and female plants have been found in France and Portugal. Further research is required on this matter.

Similar species: Other algae are vaguely similar – G.crenulatus, but the reproductive structures (cystocarps) appear as external wart-like excrescences. Chondrus crispus is repeatedly branched with rounded axils and the cystocarps are usually concavo-convex swellings. Mastocarpus stellata (Gigartina stellata) has a strongly channelled frond and Phyllophora pseudoceranoides has a long terete stipe.

How to see this species: Generally found in the very lower intertidal or shallow subtidal, in silty areas protected from strong wave action. As far as it is known, it can be found anytime.

Current status: One record of G. devoniensis from Strangford Lough (F867; F868 in the Ulster Museum) was published as G. devoniensis in 1981(=Ahnfeltiopsis devoniensis). However, this was when G. devoniensis was considered a complex of more than one species.

Further research is required. There are a few records from the south of Ireland, south of England, western France and Spain.

Why is this species a priority in Northern Ireland?

• This species is very rare.

• The species has been recorded from only one site in Northern Ireland, further research is required.

Threats: Threatened by general danger to the coast which endangers all algae.

Action:

• If refound or single record confirmed, ensure that the population is maintained.

Objectives: The species is rare and further research is required. Any possible finds should be reported to the Botany Department, National Museums Northern Ireland, 153 Bangor Road, Cultra, Co. Down, BT18 0EU Tel. 028 9039 5251.

Conservation:

• Strangford Lough is designated as Ramsar, SPA, SAC, MNR and ASSI.

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

iNaturalist: Ahnfeltiopsis devoniensis at iNaturalist World Species Observations database.

WoRMS: Ahnfeltiopsis devoniensis at World Register of Marine Species. Accepted name: Ahnfeltiopsis devoniensis (Greville) P.C.Silva & DeCew, 1992. AphiaID: 145651.

Literature:

Dixon, P.S. and Irvine, L.M. (1977). Seaweeds of the British Isles. British Museum. Natural History, London.

Guiry, M.D., L.M. Irvine, L.M. and Morton, O. (1981). Notes on Irish marine algae 4. Gymnogongrus devoniensis (Goreville) Schotter (Rhodophyta). Irish Naturalists’ Journal 20: 288 – 292.

Hardy, F.G. and Guiry, M.D. (2003). A Checklist and Atlas of the Seaweeds of Britain and Ireland. British Phycological Society, London.

Maggs, C.A., Gouglas, S.E., Fenety, J. and Bird, C.J. (1992). A molecular and morphological analysis of the Gymnogongrus devoniensis (Rhodophyta) complex in the North Atlantic. Journal of Phycology 28: 214 – 232.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Rhodymeniophycidae; Gigartinales; Phyllophoraceae; Ahnfeltiopsis

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Osborne Morton (2026). Ahnfeltiopsis devoniensis. (Greville) P Silva et DeCew. [In] Priority species, Marine Biodiversity Portal NI. https://www2.habitas.org.uk/marbiop-ni/priorityaccounts.php?item=ZM5770. Accessed on 2026-07-28