Distomus

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

Cobbles

Vulnerable

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
  • 1-2 years
  • >10 years
  • 3-10 years
  • 1-2 years
  • <1 year
Maturity
  • <1 year (Estimated)
  • >4 years
  • 3-4 years
  • 1-2 years
  • <1 year

estimated

Fecundity
  • 100 - 1000 (Estimated)
  • 1 - 10
  • 10 - 100
  • 100 - 1000
  • 1000 - 10000
  • 10000 - 1 million
  • > 1 million

estimated

Image: Distomus © John Ryland

Vulnerability

Distomus is a small ascidian (sea squirt) belonging to the Family Styelidae. It comprises clumps of solitary zooids each of about 1cm height & united at the base by a test. It is attached to stones & rocks but more often on kelp where it filters particulate matter from the water column through a complex branchial basket. It is vulnerable to dredging & to the deposition of sediment mobilised by the dredging process. This may clog the filtration system & also prevent settlement on surfaces that would otherwise be suitable for recolonisation.
 

Recoverability

There is little information on the longevity or age at maturity for this genus. The zooids are hermaphrodite & are also capable of asexual reproduction by budding. Fecundity is likely to be low, with a single egg released from each of 6-10 ovaries. There is a very restricted larval phase & settlement is likely to be close to the site of release. Dispersal potential is therefore low.
 

References

  • Biology

    • Fish & Fish, 1996
  • Taxonomy

    • Gibson et al., 2001
    • Hayward & Ryland, 1995b
    • Howson & Picton, 1997
    • Millar, 1970
  • Distribution

    • Hayward & Ryland, 1995b
    • JNCC, 1999
    • Millar, 1970
    • NBN, 2002
    • Picton & Costello, 1998
  • Reproduction

    • Berrill, 1948b