Electra pilosa

Researched By	Dr Harvey Tyler-Walters	Data Supplied By	MarLIN
Refereed by	Dr Peter J. Hayward
Taxonomy
Scientific name	Electra pilosa	Common name	A sea mat
MCS Code	Y178	Recent Synonyms	None
Phylum	Bryozoa	Subphylum
Superclass		Class	Gymnolaemata
Subclass		Order	Cheilostomatida
Suborder	Malacostegina	Family	Electridae
Genus	Electra	Species	pilosa
Subspecies
Additional Information	Colonies of Electra pilosa growing on erect substrata (e.g. a hydroid) may continue to grow lengthways once they have used up the available substratum, forming narrow, bilaminar fronds of zooids side by side, once described as Electra verticillata. Colonies growing on small pieces of substratum (e.g. a shell) occasionally enclose the substratum forming an unattached spherical colony, 3-7cm in diameter (Hayward & Ryland, 1998).
Taxonomy References	Howson & Picton, 1997, Hayward & Ryland, 1995b, Hayward & Ryland, 1998, Ryland, 1967, Ryland, 1976, Ryland, 1970
General Biology
Growth form	Crustose hard	Feeding method	Active suspension feeder
Mobility/Movement	Permanent attachment	Environmental position	Epifaunal, Epilithic, Epiphytic, Epizoic, Epibenthic
Typical food types	Phytoplankton, algal spores.	Habit	Attached
Bioturbator	Not relevant	Flexibility	None (< 10 degrees)
Fragility	Fragile	Size	Small-medium(3-10cm)
Height		Growth Rate	Specific growth rate 0.08 / day
Adult dispersal potential	10-100m	Dependency	Independent
Sociability	Colonial
Toxic/Poisonous?	No
Additional Information	Growth form Electra pilosa displays a variety of growth forms, such as, stellate patches on flat substrata, cylindrical growths around algae to narrow tufts, and narrow bilaminar fronds or occasionally as spherical masses around small substrata, described earlier (see Ryland, 1967, 1976; and Silén, 1987 for reviews). The median proximal spine may become greatly elongated in response to overgrowth by colonies of other bryozoans (Stebbing, 1973; Ryland, 1976) or in response to wave related abrasion by algae (Bayer et al., 1997). The extended spine may protect the feeding polypide from physical or mechanical disturbance (Bayer et al., 1997). Growth rates Growth rates in bryozoans have been shown to be vary with environmental conditions, especially water flow, food supply, temperature, competition for food and space, and genotype. For example: Best & Thorpe (1986) reported that feeding rate increased with increasing food concentration; Bayer et al. (1994) noted that variation in growth rates between colonies due to genotype was greater than that due to food ration; Okamura (1988) reported that in epiphytic communities, feeding rate increased with increasing flow (from 0.01-0.02 m/sec to 0.1-0.12m/s) but was reduced by competing bryozoan communities (Alcyonidium sp. or Flustrellidra hispida) in slow flow but enhanced by them in fast flow conditions; and bryozoans studied (inc. Electra pilosa) in natural currents in the Menai Strait, fed adequately and maintained growth even in very high current flows (Hermansen, et al., 2001). Although growth rates increased with temperature, zooid size decreased, which may be due to increased metabolic costs at higher temperature (Menon, 1972; Ryland, 1976; Hunter & Hughes, 1994). In the Menai Straits larger zooids are produced in spring at times of peak phytoplankton primary productivity but mean zooid size decreased as temperatures increased in summer (Okamura, 1987 cited in Hunter & Hughes, 1994). Growth rates of 0.1-0.12 µ /day were reported, irrespective of flow regime, and genotype, while natural population were reported to grow at ca 0.08 µ/ day (Hermansen et al., 2001). Feeding The structure and function of the bryozoan lophophore was reviewed by Ryland (1976), Winston, (1977) and Hayward & Ryland (1998). Best & Thorpe (1994) suggested that intertidal Bryozoa would probably be able to feed on small flagellates, bacteria, algal spores and small pieces of abraded macroalgae. Allergenic response Electra pilosa and other bryozoans have been reported to cause dermatitis and occupational eczema in fishermen (Ryland, 1967; Jeanmougin et al., 1987 summary only).
Biology References	Hayward & Ryland, 1995b, Hayward & Ryland, 1998, Ryland, 1967, Jeanmougin et al, 1987, Stebbing, 1973, Ryland, 1976, Bayer et al., 1997, Best & Thorpe, 1986, Bayer et al., 1994, Silén, 1987, Hermansen et al., 2001, Okamura, 1988, Ryland, 1977, Menon, 1972, Hunter & Hughes, 1994, Ryland, 1970, Best & Thorpe, 1994, Winston, 1977
Distribution and Habitat
Distribution in Britain & Ireland	Common on all coasts of the British Isles, although under recorded on parts of the east coast.
Global distribution	Common in all temperate seas.
Biogeographic range	Not researched	Depth range	Intertidal to at least 50m
Migratory	Non-migratory / Resident
Distribution Additional Information	Electra pilosa may be found on most substrata, and is part of the epiphytic fauna of macroalgae such as %Fucus serratus% in the intertidal and the stipes or holdfasts of laminarians in the subtidal. Electra pilosa may also be found encrusting the shells of shellfish such as mussels. It is also a common member of the fouling community (Ryland, 1967). The abundance of bryozoans is positively correlated with supply of hard substrata and hence with current strength (Eggleston, 1972b; Ryland, 1976). Similarly, the abundance of Electra pilosa increased with increasing fucoid density and surface area (O'Connor et al., 1979).
Substratum preferences	Bedrock, Large to very large boulders, Small boulders, Cobbles, Algae, Other species (see additional information), Artificial (e.g. metal/wood/concrete), Seagrass, Under boulders, Caves, Overhangs	Physiographic preferences	Open coast, Strait / sound, Sealoch, Ria / Voe, Estuary, Enclosed coast / Embayment
Biological zone	Mid Eulittoral, Lower Eulittoral, Sublittoral Fringe, Upper Infralittoral, Lower Infralittoral	Wave exposure	Moderately Exposed, Sheltered
Tidal stream strength/Water flow	Strong (3-6 kn), Moderately Strong (1-3 kn), Weak (<1 kn)	Salinity	Full (30-40 psu)
Habitat Additional Information
AMBI Group (Borja et al., 2000)	II
Distribution References	Hayward & Ryland, 1995b, Hayward & Ryland, 1998, Bruce et al., 1963, Ryland, 1967, Ryland, 1976, Ryland, 1977, Moore, 1973c, Ryland, 1970, O'Connor et al., 1979, Gontar & Denisenko, 1989
Reproduction/Life History
Reproductive type	Budding, Permanent hermaphrodite	Developmental mechanism	Planktotrophic
Reproductive Season	August to September	Reproductive Location	Water column
Reproductive frequency	Annual episodic	Regeneration potential	No
Life span	Insufficient information	Age at reproductive maturity	Insufficient information
Generation time	<1 year	Fecundity	Up to ca 30 oocytes
Egg/propagule size	121-145 µm	Fertilization type	Internal
Larvae/Juveniles Larval/Juvenile dispersal potential >10km Larval settlement period Duration of larval stage See additional information
Additional Information	Reproduction Bryozoan colonies are hermaphrodite, however, zooids may be monoecious, dioecious, protandrous or protogynous, depending on species (Hayward & Ryland, 1998). Sperm are shed from pores in the polypide tentacles of male zooids (Hayward & Ryland, 1998). In Electra pilosa maternal lophophores may actively collect sperm (Temkin, 1996). The ovaries produce up to 31 oocytes of 121-145 µm in diameter, which are released into the coelomic cavity. Temkin (1996) has shown recently that fertilization is internal, rather than external as thought previously (see Reed, 1991). Eggs come into contact with sperm (either as aggregates or singly) in the coelomic cavity, fertilization occurring at or near ovulation (Temkin, 1996). Embryos are shed into the water column and develop into planktonic cyphonautes larvae (Ryland, 1976; Reed, 1991; Hayward & Ryland, 1998). Entrainment of released sperm by the tentacles of feeding polypides in bryozoans, may reduce dispersal, resulting in self-fertilization (Temkin, 1996). Fecundity Individual zooids may produce up to 31 eggs and potentially the same number of embryos (with a fertilization efficiency of 83-100%) (Temkin, 1994), although Hyman (1959) reported a maximum of 17 eggs being released. However, while each individual zooid is not prolific, the fecundity of the colony is probably directly proportional to the number of functional zooids (Bayer et al., 1994). Reproductive season Colonies containing eggs and sperm are present in August and September and cyphonautes larvae are present in the plankton throughout the year (Hayward & Ryland, 1998). Electra pilosa was reported to settle between April and the end of November, with peaks in May/June and July to August (Ryland, 1967). Longevity Bayer et al. (1994) reported that colonies of Electra pilosa maintained in the laboratory died from the inside out, i.e. after several months the central part of the colony generally began to die. They noted that longevity data for Electra pilosa colonies was not available. However, although Electra pilosa colonies could probably survive for several years, it is probably adapted to ephemeral habitats, capable of rapid growth and reproduction of numerous offspring (r-selected). Recruitment Bryozoan larvae are probably sensitive to surface contour, chemistry and the proximity of conspecific colonies. However, Hayward & Ryland (1998) suggested that larval behaviour at settlement is only of prime importance to species occupying ephemeral habitats. For example, Electra pilosa larvae tend to orientate themselves with water flow along Fucus serratus fronds (the trend increasing with wave action) (Ryland, 1977), prefer to settle at the distal ends of the fronds and on the concave surfaces of the seaweed (Seed, 1985). (Eggleston, 1972b) demonstrated that the number and abundance of species of bryozoan increased with increased current strength, primarily due to a resultant increase in the availability of stable, hard substrata (Eggleston, 1972b; Ryland, 1976). Ryland (1976) reported that significant settlement in bryozoans was only found near a reservoir of breeding colonies. Ryland (1977) suggested that marine bryozoan larvae tend to settle on the underside of submerged structures or in shaded habitats, possibly due to avoidance of accumulated sediment or competition from algae. However, Electra pilosa larvae have an extended planktonic life and this species is a common member of fouling communities, and occurs on buoys where many other species of bryozoa are unable to colonize (Ryland, 1967). Therefore, Electra pilosa probably exhibits good dispersal and potentially very rapid recruitment.
Reproduction References	Hayward & Ryland, 1998, Ryland, 1967, Ryland, 1976, Bayer et al., 1994, Ryland, 1977, Nielsen, 1990, Reed, 1991, Seed, 1985, Ryland, 1970