BIOTIC Species Information for Electra pilosa
|Researched by||Dr Harvey Tyler-Walters||Data supplied by||MarLIN|
|Refereed by||Dr Peter J. Hayward|
|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|
|Reproduction Preferences 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).
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).
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).
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).
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,|