Height of column up to 20 mm, span of tentacles to 70 mm.
Base a lightly adherent disc slightly wider than column. Column cylindrical, flaring out trumpet-like just below the margin; its surface is finely rugose, due to tiny nematocyst batteries in the ectoderm. Disc wide, with the mouth on a prominent hypostome. General texture of the whole anemone is very soft and flaccid.
Tentacles: Very long, not retractile, with slight constrictions at their bases, up to about 200; in full expansion their volume probably exceeds that of the column.
Colouration: Column slightly translucent, white or pink; if ripe gonads are present these are deep orange-pink and show through the column wall. Tentacles white with a distinctive frosted appearance, especially near their tips.
In places where there is minimal water turbulence, such as sea lochs, fjords, or deep water. Attaches to rocks or various organic substrata - ascidians, worm tubes, corals (Lophelia, etc.) - from the shallow sublittoral (c. 9 m) to at least 500 m depth.
From the coasts of Scandinavia to Rockall Bank in the north-east Atlantic. Recently discovered in abundance in several sheltered localities on the west coast of Scotland.
Protanthea is an unusually active anemone, reacting strongly to various stimuli - introduction of food, local agitation of the water, etc. These reactions vary from a violent twitching or thrashing of the tentacles to sudden, complete relaxation of the musculature, so that it hangs limply from its attachment. Under certain circumstances it may shed some or all of its tentacles, particularly if lifted carelessly from the water. It is extremely sticky, adhering strongly to fingers, glassware, etc., often to the extent of causing itself physical damage. Fragments of tissue removed in this way (except tentacles) are capable of regenerating into complete anemones; otherwise asexual reproduction is not known in this species.