Bugula turbinata

Researched ByDr Harvey Tyler-WaltersData Supplied ByMarLIN
Refereed byDr Peter J. Hayward
Taxonomy
Scientific nameBugula turbinataCommon nameAn erect bryozoan
MCS CodeY250Recent SynonymsNone
PhylumBryozoaSubphylum
SuperclassClassGymnolaemata
SubclassOrderCheilostomatida
SuborderNeocheilostomatinaFamilyBugulidae
GenusBugulaSpeciesturbinata
Subspecies  
Additional InformationAll British species of Bugula die back in autumn, over-wintering as ancestrulae, colony stumps or stolons (Hayward & Ryland, 1998). Little information was found on the biology of Bugula turbinata. The following information was derived from information concerning other species of Bugula where possible.
Taxonomy References Hayward & Ryland, 1998, Howson & Picton, 1997, Ryland, 1970, Ryland, 1976
General Biology
Growth formArborescent / Arbuscular, TurfFeeding methodActive suspension feeder
Mobility/MovementPermanent attachmentEnvironmental positionEpibenthic, Epifaunal, Epilithic
Typical food typesPhytoplankton (<50µm), macroalgal spores, detritus, and bacteria.HabitAttached
BioturbatorNot relevantFlexibilityHigh (>45 degrees)
FragilityFragileSizeSmall-medium(3-10cm)
Height3-6 cmGrowth RateSee additional information
Adult dispersal potentialNoneDependencyIndependent
SociabilityColonial
Toxic/Poisonous?No
Additional InformationGrowth form
Bugula species form erect tufted growths, characterized by continuous branching. The holdfast is composed of encrusting rhizoids. The exact nature of branching and colony form varies with species, active growth occurring at the branch apices. In Bugula turbinata, the branches form spirally around a central axis (Dyrynda & Ryland, 1982; Hayward & Ryland, 1998).

Growth rates
Growth rates in bryozoans have been shown to vary with environmental conditions, especially water flow, food supply, temperature, competition for food and space, and genotype. For example:

  • Wendt (1998) reported that the length of time larvae spent in the plankton affected subsequent growth and reproduction of colonies of Bugula neritina, i.e. although specific growth rates were probably the same, colonies developing from 24 hr old larvae were 35% smaller, began reproduction about 1.5 days later and had about 50% fewer brood chambers than those growing from 1 hr larvae.
  • Wendt (1998) also noted that colonies growing on upward facing surfaces in the laboratory were about 40% smaller than colonies growing on downward facing surfaces.
Growth in numbers of zooids is exponential. Wendt (1998) reported a mean number of 74-113 zooids 14 days after larval settlement in Bugula neritina, depending on the length of time the larvae spent in the plankton. Note, however, that Bugula neritina is a warm temperate species probably only remotely related to the NE Atlantic species (P. Hayward, pers. comm.). Schneider (1963) reported that buds grew at about 12 µm /hr (a maximum of 25 µm/hr) in the laboratory. Schnieder's estimates probably represent optimal growth under laboratory conditions, however, growth in Bugula species is likely to rapid.

Feeding
The structure and function of the bryozoan lophophore was reviewed by Ryland (1976), Winston (1977), and Hayward & Ryland (1998). Ambient water flow is important for bringing food-bearing water within range of the colonies own pumping ability (McKinney, 1986), however, increased water flow reduces feeding efficiency in small colonies but not of large colonies (Okamura, 1984). Curiously, upstream zooids dominated feeding in slow flow (1-2 cm/s) and central zooids in fast flow (10-12 cm/s) (Okamura, 1984). Bryozoa probably feed on small flagellates (<50 µm), bacteria, algal spores and small pieces of abraded macroalgae (Winston, 1977; Best & Thorpe, 1994).

Biology References Hayward & Ryland, 1998, Ryland, 1967, Ryland, 1970, Ryland, 1976, Best & Thorpe, 1994, Winston, 1977, McKinney, 1986, Okamura, 1984, Schneider, 1963, Wendt, 2000, Eggleston, 1972b, Dyrynda & Ryland, 1982, Wendt, 1998
Distribution and Habitat
Distribution in Britain & IrelandA southern species predominantly found on the south and southwest coasts of England and Wales but with records from Shetland, Orkney, the north east coast, Ireland, the west coast of Scotland and St. Kilda.
Global distributionRecorded from Britain to the Mediterranean.
Biogeographic rangeNot researchedDepth rangeLower shore to ca 21m.
MigratoryNon-migratory / Resident
Distribution Additional InformationBugula turbinata has been reported on the lower shore to al least 21 m in Lundy (Hiscock, 1985b; Hayward & Ryland, 1998). Although found in a variety of wave exposed habitats, the microhabitat occupied by Bugula turbinata, under boulders, overhangs and crevices is probably protected from direct wave action. Although found in wave sheltered situations or weak tidal streams, some water flow is probably important to bring food and nutrient-laden water to the colonies and ensure an adequate supply of hard substrata. The abundance of bryozoans is positively correlated with supply of hard substrata and hence with current strength (Eggleston, 1972b; Ryland, 1976). Bugula spp. are characteristic fouling bryozoans, and may be found in the intake pipes of ships or power stations, and on ships hulls. The geographic distribution of Bugula species has been extended by transportation by shipping (Ryland, 1967). However, no information on transportation of Bugula turbinata was found.
Substratum preferencesArtificial (e.g. metal/wood/concrete), Bedrock, Large to very large boulders, Small boulders, Overhangs, Cobbles, Crevices / fissures, CavesPhysiographic preferencesOpen coast, Strait / sound, Sealoch, Ria / Voe, Enclosed coast / Embayment
Biological zoneLower Eulittoral, Sublittoral Fringe, Upper Infralittoral, Lower InfralittoralWave exposureVery Exposed, Exposed, Moderately Exposed, Sheltered, Very Sheltered
Tidal stream strength/Water flowStrong (3-6 kn), Moderately Strong (1-3 kn), Weak (<1 kn)SalinityFull (30-40 psu)
Habitat Additional Information
Distribution References Hayward & Ryland, 1998, Ryland, 1967, Ryland, 1970, Ryland, 1976, Wendt, 2000, JNCC, 1999, NBN, 2002, Eggleston, 1972b, Hiscock, 1985, Lewis, 1964, Hiscock & Mitchell, 1980, Hiscock, 1985 (b), Castric-Fey & Chassé, 1991, Castric-Fey, 1974
Reproduction/Life History
Reproductive typeProtogynous hermaphrodite Developmental mechanismLecithotrophic, Viviparous (No Care)
Reproductive SeasonEarly summer to early autumnReproductive Location
Reproductive frequencyAnnual protracted Regeneration potentialNo
Life spanInsufficient informationAge at reproductive maturity<1 year
Generation time<1 yearFecundityThe colony fecundity is likely high.
Egg/propagule sizeInsufficient informationFertilization typeInternal
Larvae/Juveniles
Larval/Juvenile dispersal potential<10mLarval settlement periodSummer and autumn
Duration of larval stage<1 day  
Additional InformationThe reproductive biology of Bugula sp. has been extensively studied and reviewed. Gametogenesis and embryology are detailed by Ryland (1976), Franzén, (1977), Dyrynda & King (1983) and Reed (1991).
The fronds of Bugula species are ephemeral, large colonies present in summer, dying back in late autumn and over-wintering as perennial, dormant, holdfasts or ancestrulae (Eggleston 1972a; Dyrynda & Ryland, 1982). Bugula species are placental ovicell brooders, producing small embryos that are brooded in conspicuous hyperstomial ovicells, increasing in size considerably during development due to nutrition derived from the inside of the ovicell, which acts as a placenta. For example, the Bugula turbinata embryo grows 33 fold in embryogenesis (Dyrynda & Ryland, 1982; Dyrynda & King, 1983).

The reproductive cycle of Bugula flabellata is summarised below and may be similar in other Bugula spp., although Eggleston (1972a) noted that the number of generations in the other species was not known.

Zooids are protogynous hermaphrodites, developing eggs then sperm. Gametogenesis begins as the new zooid has formed. Egg maturation, ovulation and transfer of a single egg to the ovicell occurs halfway through the life of the first polypide. Embryogenesis continues through to the life of the second polypide, and larvae are released prior to ovulation of the next egg, taking about 3 weeks in July at Oxwich Point, Swansea. Sperm are produced after the egg has transferred to the ovicell, during the last half of the first polypide's life, and are released through the terminal pore in the tips of the tentacles (Dyrynda & Ryland, 1982). Fertilization probably occurs at ovulation, within the zooid (internal fertilization) (Dyrynda & Ryland, 1982; Reed, 1991). Once completed the cycle is repeated. Dyrynda & Ryland (1982) reported 4 cycles of polypides within zooids, after which frond death is simultaneous. Zooids may be found at different stages all the length of the frond (Eggleston, 1972a; Dyrynda & Ryland, 1982).

In bryozoans, released sperm are entrained by the tentacles of feeding polypides and may not disperse far, resulting in self-fertilization. However, genetic cross-fertilization is assumed in oviparous and brooding bryozoans based partly on the proximity of other colonies and genetic data, although there is evidence of self fertilization (Reed, 1991; Hayward & Ryland, 1998).

Overall, Bugula flabellata exhibits two generations of ephemeral fronds each summer. Each fronds begins to produce larvae soon after initiation, within 1 month. At Oxwich, Swansea, the first frond generation appeared in June and died in August, the second generation arising in August and dying back in late October (Dyrynda & Ryland, 1982). In the Isle of Man, Eggleston (1972c) noted rapid growth in March, with eggs and embryos by May, dying back in September, with a second generation in mid September to late October. Eggleston (1972a) also noted that offspring of the first generation grew rapidly and contributed to the second generation.

Ryland (1970) noted that in British waters bryozoan reproduction was generally maximal in late summer, declining into autumn. Dyrynda & Ryland (1982) concluded that Bugula flabellata was adapted to rapid growth and reproduction (r-selected), taking advantage of the spring/summer phytoplankton bloom and more favourable (less stormy) conditions.

Fecundity
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) and is probably high.
Longevity
The fronds of Bugula sp. are ephemeral, surviving about 3-4 months but producing two frond generations in summer before dying back in winter. However, the holdfasts are probably perennial (Dyrynda & Ryland, 1982). No information concerning the longevity of holdfasts was found.

Dispersal
The lecithotrophic coronate larva of Bugula species is free-swimming for a short period of time (<1 to 36 hrs) and colonies developing from later settling larvae (24 hr old) have significantly reduced growth and reproduction (Wendt, 1998, 2000). Therefore, dispersal is likely to be limited, resulting in poor gene flow and population subdivision( Wendt, 1998).
Bugula species are common members of the fouling community of shipping and harbour installations but are far less abundant on buoys (Ryland, 1967). Keough & Chernoff (1987) noted that post settlement mortality of Bugula neritina was high, ca 70% in the first week after settlement on a Florida seagrass bed. Populations showed substantial spatial and temporal variation and Keough & Chernoff (1987) concluded that this variation was due to poor dispersal by the lecithotrophic larvae. Similarly, Castric-Fey (1974) noted that Bugula turbinata, Bugula plumosa and Bugula calathus did not recruit to settlement plates after ca two years in the subtidal even though present on the surrounding bedrock. Ryland (1976) reported that significant settlement in bryozoans was only found near a reservoir of breeding colonies. The short larval life and large numbers of larvae produced probably results in good local but poor long-range dispersal depending on the hydrographic regime.
Reproduction References Hayward & Ryland, 1998, Ryland, 1967, Ryland, 1970, Ryland, 1976, Wendt & Woollacott, 1999, Wendt, 2000, Dyrynda & Ryland, 1982, Dyrynda & King, 1983, Franzén, 1977, Wendt, 1998, Keough & Chernoff, 1987, Eggleston, 1972a, Castric-Fey, 1974