Ciona savignyi

Ciona intestinalis

Ciona savignyi is a sea-squirt native to the Asian Pacific. These ascidians are sessile filter feeders that unfortunately decided to feed on very small particles of sewage and waste, which led to the establishment of populations in regions all over the world.

Nobody can predict if invasive organisms will become nuisance species or not. We do, however, know some things already about Ciona savignyi, and its close cousin from Europe, Ciona intestinalis, both of which have a history as invasive species. Both species grow abundantly in certain man-made environments, floating docks, boat hulls, and on hanging aquaculture rafts. Interestingly their distribution is often consistent with hull fouling on ships and recreational boats as they seem to be the major vectors of introduction and spread. On natural surfaces they are less common, but C. intestinalis is known to cover eelgrass blades in some Scandinavian Fjords.

Early detection of these species would be very helpful but morphology-based ascidian taxonomy is a highly specialized discipline and the mis-identification of species has been, and remains, a significant problem due to a lack of reliable diagnostic morphological characters.

Researchers of the Cawthron Institute, Nelson and from the University of Waikato, Hamilton used DNA Barcodes to detect Ciona savigny in the waters around New Zealand. They also developed a simple PCR-based assay for discriminating between the two morphological very similar species Ciona intestinalis and Ciona savignyi. 

This is a great example how DNA Barcoding done the right way can aid in accurate species identification with applications in both biosecurity  programs and general research.