Ivell’s Sea Anemone — Edwardsia ivelli

Widewater Lagoon Local Nature Reserve · TQ 196 041

Edwardsia ivelli, known as Ivell’s sea anemone, is one of the rarest animals in the world. It was first discovered at Widewater Lagoon by Professor Richard Ivell in 1973 — the only site at which it has ever been recorded. A small, worm-like species that lives buried in the lagoon sediment with only its tentacles exposed, it was last confirmed present in 1983. It has not been found since, and is listed as critically endangered, with some authorities considering it possibly extinct.

The photograph below is believed to be the only known image of a living specimen. The animal is half-buried in the sandy sediment, and is difficult to make out without knowing what to look for — the pale, translucent disc of tentacles is visible near the centre of the image.

In the early 2000s, volunteers from the Friends of Widewater assisted Professor Ivell in a renewed search of the lagoon sediment in the hope of relocating the anemone. Despite collecting and examining a great many samples, no specimens were found. It was a near-impossible task — Richard Ivell must simply have struck lucky that one time. The species is rarely discussed now, and most of the current Friends group members have no recollection of those searches. The lagoon is closely surrounded by housing, and diffuse run-off — fertilisers, detergents, road drainage — has altered the water chemistry over the decades. Even the garden lawns nearby always looked rather too green to be unfertilised. — Ray Hamblett, Friends of Widewater

Edwardsia ivelli — the only known photograph

Edwardsia ivelli

Ivell’s Sea Anemone

Widewater Lagoon, Lancing
First discovered: 1973 (Prof. Richard Ivell)
Last confirmed record: 1983

This is believed to be the only known photograph of a living specimen of Edwardsia ivelli. The animal is partially buried in the lagoon sediment; the pale tentacle disc is visible near the centre of the image. Attempts to refind the species in the summer of 2002 were unsuccessful.

A separate later finding — Haliplanella lineata

Subsequent research at a nearby location in the lagoon (TQ 202 043) identified a different species of miniature sea anemone: Haliplanella lineata, characterised by distinctive orange stripes not found on other British sea anemones. The specimens discovered were dwarf forms, only 2mm in height and 3mm in diameter. This is an introduced (non-native) species that inhabits harbours, estuaries and occasionally lagoons where salinity is below full seawater strength; it is unrelated to Edwardsia ivelli.

This finding is recorded here separately to avoid any confusion with the original Edwardsia ivelli record. The two are distinct species found at different locations within the lagoon.

Report: Dan Metcalfe, University of Brighton · BMLSS Sea Anemones · Haliplanella lineata — BioMar

The aquatic life of Widewater Lagoon is covered in detail on Andy Horton’s Widewater Lagoon page.