The lights are still on: the persistence and extraordinary density of the European lightbulb sea squirt Clavelina lepadiformis (Ascidiacea) in the Northwest Atlantic Ocean
摘要
The European ascidian Clavelina lepadiformis, the lightbulb sea squirt, was first observed in the Northwest Atlantic Ocean in 2008. Two close but isolated populations in Connecticut, in southern New England, were reported: one in a small harbor in Stonington and another, 15 km to the west, in the Thames River in New London. Last reported in 2009, we establish that C. lepadiformis is still present in both locations. In the summer, C. lepadiformis is the aspect dominant fouling species in Stonington Harbor, coating seawalls, pilings and other surfaces in what we newly report to be densities that can exceed 58,000 individuals/m2, yielding an estimate of millions of ascidians in the harbor, spanning a north-to-south range of approximately 1 km. While previously thought to be unable to naturally reattach once dislodged, we demonstrate that adult C. lepadiformis can reattach to a variety of substrates under laboratory conditions, suggesting the potential for drifting zooids to act as dispersal propagules. We further explore possible reasons why C. lepadiformis appears to have failed to spread yet along the North American Atlantic seaboard.