Didemnum

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

Cobbles

Robust

Other: Chordata

Genera Characteristics Recorded Traits Possible Values
Size in cm
  • 1-10 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)
  • Short Term Planktonic
  • Long Term Planktonic
  • Short Term Planktonic
  • Brooded or Laid Eggs

“Short Term Planktonic”

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

Image: Didemnum © John Ryland

Vulnerability

Didemnum is a small colonial ascidian that lives permanently attached to the substratum. It is found on many British and Irish coasts, although it is rare in eastern Scotland, south east England and much of Ireland. It is likely to be vulnerable to dredging activities.

Recoverability

Didemnum is a permanent hermaphrodite that can also reproduce through budding. The life span is one year and sexual maturity is reached within few months. Reproduction is annually protracted and fertility rates change depending on environmental conditions. Didenmum has the ability to attach tenaciously to substrates but the tunic is flaccid and tears easily. If even a small part of the body wall adheres to any organisms that are transported to other areas, it can rapidly colonize a new substrate and may already be in reproductive mode. Recovery after dredging is likely to be fast.

References

  • Biology

    • Bullard et al, 2007
    • Dias & Sergio de Almeida, 2004
    • nurc website
  • Reproduction

    • Bullard et al, 2007
    • Dias & Sergio de Almeida, 2004
    • nurc website
    • Valentine et al., 2007