Cornish Biodiversity Network  -  Supporting Wildlife Recording

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Cornish Red Data (2009)

The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.

Victorella pavida - Trembling Sea-mat

Habitat & Distribution

This species grows on submerged wood, stones, and stems of Common Reed Phragmites australis in brackish water. First discovered and described from the Surrey Canal and Victoria Docks London in 1870, it has since been lost from both of these sites. It was discovered in a brackish pool in west Cornwall in 1968 and, at the present time, this remains the only known British site for this bryozoan species. Gainey (1997) surveyed the distribution of this species at Swanpool, Falmouth, and found it to be abundant, especially so on the bases of the reeds present. A more recent survey by Evans et al. , 2003, came to similar conclusions and, in 2004, M.C. Carter completed a study on the biology and genetic diversity of this same population. Elsewhere, it seems to be common in estuarine and lagoonal habitats around Naples and in the valley of the River Po. It has also been reported from the Black Sea, the Baltic, Brazil, the eastern United States, India

and Japan.


During the summer of 1994, the pool where the species occurs became eutrophic, the water becoming very dark and smelly. Two new housing estates in the water catchment area of the pool could also reduce the salinity of the pool in the long term. Run-off from the road could carry oil into the pool and the faeces from the large numbers of water-birds attracted to the pool for food could also potentially cause eutrophication. Maintenance of brackish conditions and the prevention of pollution are obvious prerequisites for the continued existence of this species in the pool.


In 1988, it was protected by its addition to Schedule 5 of the Wildlife and Countryside Act 1981. Victorella pavida is on the UK list of Priority Species and has its own Species Action Plan.


I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.

The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.

Cornish Biodiversity Network. 2017.