Obelia

A Robust genera from the “Other: Cnidaria” group, mostly found in Cobbles

Cobbles

Robust

Other: Cnidaria

Genera Characteristics Recorded Traits Possible Values
Size in cm
  • >20 cm
  • <1 cm
  • 1-10 cm
  • 11-20 cm
  • >20 cm
Genera Characteristics Recorded Traits Possible Values
Motility (Adult)
  • Sedentary
  • Adult
  • Short Range Mobility
  • Sedentary

“Sedentary”

Motility (Larval)
  • Long Term Planktonic
  • Brooded or Laid Eggs
  • Long Term Planktonic
  • Short Term Planktonic
  • Brooded or Laid Eggs

“Long Term Planktonic” “Brooded or Laid Eggs”

Lifespan
  • 3-10 years (Estimated)
  • >10 years
  • 3-10 years
  • 1-2 years
  • <1 year

estimated

Maturity
  • <1 year
  • >4 years
  • 3-4 years
  • 1-2 years
  • <1 year
Fecundity
  • 1000 - 10000
  • 10000 - 1 million
  • 1 - 10
  • 10 - 100
  • 100 - 1000
  • 1000 - 10000
  • 10000 - 1 million
  • > 1 million

Image: Obelia © John Ryland

Vulnerability

Obelia is a medium-large foliose hydroid belonging to the Family Campanulariidae. Colonies reach 20-50cm in height & are attached to rocks & boulders on the seabed, as well as to stones & shells provided the substratum is stable. The polyps feed by capturing zooplankton from the water column by special cells (nematocysts). The colonies are sessile & are vulnerable to both dredging & probably to deposition of sediment mobilised during the dredging process.
 

Recoverability

Obelia is a relatively long-lived genus with a rapid growth & regeneration ability in the hydroid stage. This stage produces flattened male & female medusae by asexual budding from March-July. The medusoid stage lasts about 7-30 days in the plankton before eggs of about 0.2mm develop in the female. Between 10,000 and 40,000 eggs are reported to be produced. These are fertilised externally by the male & develop into a planula larva of 1-2mm length. This then settles after a period of 5-21 days. The widespread dispersal potential & rapid growth of the colonial phase of this genus suggests that it has a high recoverability following disturbance.

 

References

  • Biology

    • Berrill, 1949
    • Boero, 1984
    • Brault & Bourget, 1985
    • Calder, 1990
    • Cornelius, 1992
    • Cornelius, 1995a
    • Cornelius, 1995b
    • Crowell, 1953
    • Hammett & Hammett, 1945
    • Hammett, 1943
    • Hammett, 1951a
    • Hammett, 1951b
    • Hammett, 1951c
    • Hammett, 1951d
    • Hammett, 1951e
    • Judge & Craig, 1997
    • King, 1974
    • Kosevich & Marfenin, 1986
    • Lauckner, 1980
    • Marfenin, 1997
    • Salvini-Plawen, 1972
    • Standing, 1976
    • Stepanjants, 1998
  • Taxonomy

    • Cornelius, 1990a
    • Cornelius, 1995a
    • Cornelius, 1995b
    • Howson & Picton, 1997
    • Stepanjants, 1998
  • Distribution

    • Berrill, 1948
    • Boero & Bouillon, 1993
    • Boero & Fresi, 1986
    • Boero, 1984
    • Bourget et al., (in press)
    • Cornelius, 1992
    • Cornelius, 1995b
    • Hiscock, 1983
    • Hunter, 1989
    • JNCC, 1999
    • Judge & Craig, 1997
    • NBN, 2002
    • Picton & Costello, 1998
    • Riedl, 1971
    • Sommer, 1992
    • Stepanjants, 1998
    • Zamponi et al., 1998
  • Reproduction

    • Berrill, 1948
    • Berrill, 1949
    • Billard, 1901a
    • Billard, 1901b
    • Boero & Bouillon, 1993
    • Brault & Bourget, 1985
    • Broch, 1927
    • Bruce et al., 1963
    • Cornelius, 1990b
    • Cornelius, 1992
    • Cornelius, 1995a
    • Cornelius, 1995b
    • Crowell, 1953
    • Elmhirst, 1925
    • Faulkner, 1929
    • Hammett, 1943
    • Hammett, 1951a
    • Hammett, 1951b
    • Hammett, 1951c
    • Hammett, 1951d
    • Hammett, 1951e
    • Kosevich & Marfenin, 1986
    • MacGinitie and MacGinitie, 1949
    • Russell, 1953
    • Sommer, 1992
    • Stepanjants et al., 1993
    • Stepanjants, 1998