Rupertina stabilis occupies a depth restricted biotope of suspension feeding animals situated at the Norwegian continental margin. It extends from the Voring plateau northwards for at least 200-300 km, in depths between 600 and 800 m. This slope position is known for relatively strong bottom currents and shifting watermass boundaries. The species is attached to hard substrates, mainly stones or hydroid stalks and obviously prefers an elevated position. It is building a permanent cyst of sponge spicules and debris at the apertural region. The spicules are used to support a pseudopodial network similar to that described from Halyphysema (Lipps 1983). It is believed to serve as a filter apparatus. A review of known occurrences in the Atlantic is given, suggesting a temperature adaption of the species ranging from 0°C to a maximum of 8°C. Specimens were successfully cultured for about 2-3 weeks.
