Leafy Bryozoans and Other Bryozoan Species in General Play an Important Role in Marine Ecosystems
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These wash up on the shoreline looking like Flustra foliacea clumps of seaweed. Class: Gymnolaemata Order: Cheilostomata Family: Flustridae Genus: Flustra Distribution Flustra foliacea has a wide It is common to the coastal areas of northern Europe especially distribution in the North in the North Sea. Countries include Britain, Ireland, Belgium, Atlantic Ocean, on both the Netherlands, and France. It does not continue any further south European and American than northern Spain. In Canada it is in Nova Scotian waters, sides. including the Bay of Fundy and the Minas Basin. Habitat It most frequently occurs between 10-20 m water depths. It is This is a cold water species. typically found on the upper faces of moderately wave-exposed It prefers high salinity bedrock or boulders subjected to moderately strong tidal waters, but can also found streams. These rocky patches may be interspersed with gravelly in areas with lower salinity. sand patches, causing a scouring effect. Most Bryozoans live in It occupies sublittoral salt water, and of the 20 or so freshwater species found in North (below low tide) areas. America, most are found in warm-water regions attached to plants, logs, rocks and other firm substrates. Food This species is an active This is a colonial animal composed of various types of zooids. A suspension feeder. They zooid is a single animal that is part of the colony. The basic consume phytoplankton, zooids are the feeding ones, called the autozooid. Each of these detritus, and dissolved has a mouth and a feeding structure, the lophophore, which is organic matter. covered in ciliated tentacles. It is protruded into the sea water, and beating of its cilia creates a feeding current which draws Reproduction plankton towards the mouth. They are hermaphrodites. They can produce both The larvae of F. foliacea are large non-feeding (coronate) larvae, sperm and eggs. Sperm is which lack a shell and have a densely ciliated belt (the corona) spawned, whereas eggs are for locomotion. They have a very short dispersal distance. After usually harboured inside the release, the larvae settle within minutes or hours in the vicinity body wall. The eggs are of release. They metamorphose and develop into being the first internally fertilized by zooid of the new colony, the 'ancestrula'. sperm coming back in on Asexual reproduction also occurs by budding off new zooids as lophophore feeding the colony grows, and is the main way by which a colony currents. Fertile eggs expands in size. Also, if a piece of a bryozoan colony breaks off, develop into larvae which the piece can continue to grow and will form a new colony the are released into the water. following summer. Development Flustra foliacea colonies grow in spring and summer. For the first The first 'ancestrula' zooid year, colonies grow only along the surface (encrusting), with buds out, creating many loose fronds only being formed in subsequent years. These are additional zooids which produced when two encrusting colonies meet, and the two edges form encrusting mats, that make contact begin to grow upwards, back to back. The spreading out over the fronds now begin to develop. Annual growth rings are visible. bedrock substrate. The rate of growth is 1-6 cm per year. The total lifespan of a colony may reach 12 years. Characteristics The name ‘bryozoan’ Colonies can be between 6 and 20 cm in height. comes from the Greek bryo They are formed into bushy clumps. The fronds meaning 'moss' and zoan are light grey to brown in colour. They are meaning 'animal'. They are broadly lobed, and strap-like. They have a distinct highly complex colonial smell of lemons and are often mistaken for animals constructed of seaweed. The zooids themselves are on both sides individual 'zooids', all of the fronds. They are tongue shaped, 0.2-0.28 connected by living tissue. mm wide and 0.4 mm long and they have 4 to 5 club-like spines at the broad end of each zooid. Adaptations As many as 10,000 There is a division of labour within a colony, (cyphonautes) larvae can be specific functions (other than feeding) are released from a single assigned to different individuals; brooding Flustra colony. The zooids zooids (gonozooids), defence zooids), are polymorphic, having anchoring the colony etc. The zooids are different functions to protected within a cup - or box-shaped perform. The majority of exoskeleton of calcified chitinous tissue. zooids are specialised for Further protection is provided by their feeding (autozooids). spines. They have the ability to withdraw their (feeding) tentacles and lophophores very quickly when alarmed. Status/Threats Bryozoans are eaten by a variety of grazing animals, Dredging has a drastic effect on colonies. such as sea urchins and various molluscs. Although considered a nuisance species in some areas the Leafy bryozoans and other bryozoan species in general play an important role in marine ecosystems. They filter a lot of Sightings in Nova Scotia seawater. They provide food It is frequently found for other marine animals. washed up on beaches after They also give shelter within storms. They are quite their fronds to many other common around Nova small organisms in creating Scotia. living habitats. .