Biology
Corella eumyota has the capacity to establish dense populations very rapidly. Here it dominates the submerged surface of a concrete pontoon, forming an almost continuous carpet in Vila Praia de Âncora, Portugal. The marina was built only two years before the survey. © A El Nagar
Corella eumyota is a brooding hermaphroditic sea squirt.
It is capable of self-fertilization because the location of the sperm duct opening is very close to the oviductal opening.
The non-feeding tadpole-shaped larvae are retained after hatching until they are competent to settle, resulting in:
- an extremely short free-swimming larval period
- limited dispersal
- a tendency for the larvae to settle on the parent tunic or adjacent adults immediately after release, resulting in the formation of large clumps of variously sized individuals
Corella eumyota is a summer brooder.
In the southern hemisphere the breeding season may last more than six months of the year; from mid-September to the end of March. In the northern hemisphere its breeding season is offset to correspond to the longer day length and warmer temperature.
Dispersal
Adult orange-tipped sea squirts self-fertilise, brood their young, and the larvae have an unusually short free-swimming period. So, the transfer of even one or a few individuals on fouled boat hulls might be enough to establish new populations.
Its broad distribution in western Europe indicates that Corella eumyota is likely to spread rapidly within a region once established.
The mode of transport of Corella eumyota into the northern hemisphere, while unknown, is presumed to be anthropogenically by:
- hull fouling
- transport of settled post-metamorphic individuals on floating debris in ballast water, or
- importation of contaminated mussels or oysters from the southern hemisphere
