About Flustra foliacea (Linnaeus, 1758)
Flustra foliacea is a bryozoan that is often mistaken for seaweed, as it forms an animal colony. Its fronds can grow up to 20 centimetres (7.9 inches) in height, have rounded ends, and give off a strong lemon scent. It can be distinguished from the superficially similar species Securiflustra securifrons by the distinct widening of its frond branches toward their tips. Each individual zooid in the colony is roughly rectangular, with 4–5 short spines at the distal end and 13–14 tentacles surrounding the lophophore. This species has a wide distribution across the North Atlantic Ocean, occurring along both the European and North American coasts. It is restricted to colder sublittoral waters, and its southern range limit is in northern Spain. The fronds of Flustra foliacea are frequently used as a substrate by other animals that live on them, called epibionts. These epibionts include other bryozoa such as Crista eburnea, hydroids, sessile polychaete worms, and the porcelain crab Pisidia longicornis. A number of other animals feed on Flustra foliacea: these include the sea urchins Echinus esculentus and Psammechinus miliaris, the nudibranch Crimora papillata, and the pycnogonid Achelia echinata, which feeds preferentially on this species. Flustra foliacea colonies only grow during the spring and summer, which leaves visible annual growth rings. Breeding happens between separate male and female zooids within the same colony in autumn and winter. The zooids produce outgrowths called ovicells, which hold developing embryos and are visible from October to February. Larvae are released in spring; after a short free-living period, they settle onto a substrate. In their first year, colonies grow only as an encrusting layer along the substrate surface. Loose fronds do not form until subsequent years, when two encrusting colonies meet, their contacting edges grow upward back to back to produce the fronds. The total lifespan of a Flustra foliacea colony can reach 12 years. Colonies are frequently found washed up on beaches after storms.
