Water rock-bristle  (Seligeria carniolica)

Classified as Critically Endangered in Great Britain (2).

This minute dark green moss is very distinctive. The tapering leaves have very broad bases and long, narrow tips (2).

Water rock-bristle has only ever been recorded from two places in Britain. It is thought have been lost from the only Scottish site as a result of a fall of the stream bank on which it grew (2). It still persists in small numbers at a site in south Northumberland (2). This moss is endemic to Europe, but is endangered, and is known from single sites in the following countries: Austria, Germany, France, Norway, Romania, Sweden, and Switzerland. It is also known from three sites in the former Yugoslavia (1) (2).

This moss grows on permanently or periodically moist and shaded calcareous sandstone or limestone by the side of streams (1). It is found at altitudes of 150 to 250 metres (2). All of the sites that support this species are thought to have stayed free of ice during the last ice age; it is therefore thought that water rock-bristle may be a 'pre-glacial relict'; a relict species from before the ice age (2).

Little is known of the biology of this species. Mosses, hornworts and liverworts form a group of plants called bryophytes (2). Bryophytes lack many of the more complex structures of the higher plants, such as a vascular system, and flowers. They do not have roots, instead they have structures called 'rhizoids' which absorb water and anchor the plant to the substrate. All bryophytes have an interesting life cycle consisting of two main parts, called the gametophyte and sporophyte generations (3). Plants that are in the gametophyte stage can reproduce sexually. Male organs (antheridia) produce male sex cells or gametes called antherozoids, which actually move to the female sex organs (archegonia) (3) through water droplets. Fertilisation occurs and a plant develops called a 'sporophyte', which remains attached to the plant. The sporophyte releases spores from within a capsule; the spores disperse and develop into a new gametophyte stage plant (3).

Potential threats include changes in the catchment area, which could affect the chemistry of the water, such as agricultural run-off, over grazing or the growth or planting of forests (2). Felling of or disturbance to streamside trees could remove shade and affect the humidity of the site; further threats are drought and botanical collecting (2).

A Species Action Plan has been produced for this moss under the UK Biodiversity Action Plan. This plan aims to maintain the populations at the single remaining site, and to increase its extent if possible (1). The Northumberland site is not a Site of Special Scientific Interest (SSSI), but it has been suggested that the site is notified as an SSSI to help to ensure the long-term survival of the species (1).

View the UK BAP Species Action Plan on-line at:
http://www.ukbap.org.uk