Post-metamorphic attachment by solitary ascidian Ciona intestinalis (Linnaeus, 1767) juveniles from Newfoundland and Labrador, Canada

Ciona intestinalis is an invasive marine biofouling organism first detected in coastal waters of Newfoundland and Labrador in 2012. As a sessile animal, it is essential that larvae locate a suitable substrate for attachment in an adequate environment, but the timing of this critical event may not be as important as once believed. We demonstrate that while swimming larvae may have limited time to locate and attach to a substrate, development into juvenile stages and prolonged survival is possible without substrate attachment. In laboratory experiments we demonstrate that between 38 and 61% of tadpole larvae undergo pre-attached metamorphosis at the water surface or free floating. These are the first experiments to confirm the ability of C. intestinalis juveniles to initiate post-metamorphic attachment when substrate is available. In the early stages of juvenile development (i.e. Rotation, FAS I, and FAS II) there are no differences in post-metamorphic attachment ability. Postponing attachment until after the onset of metamorphosis allows C. intestinalis larvae and juveniles to effectively prolong the planktonic stage and increase their dispersal potential. This information is of particular concern to aquaculture industries, but also may have implications for management efforts in regions where C. intestinalis has successfully invaded.