Ascidian colonies

Erica Westerman (first author on the study discussed in my last post) kindly sent me two nice images of ascidian colonies*. The first image shows a pair of small Botrylloides violaceus colonies (orange) growing up to each other at the top of the image. The lower colony is getting overgrown by a larger colony of Botryllus schlosseri at the bottom (brown). The individual zooids within the colony are orange (or brown) oblongs set in rosettes of 6 or more. Each set of individuals sucks in water through an opening at the colony surface, and the water flows to an opening at the center of the rosette, shared by all the zooids in the rosette.

The second image shows several larger colonies, of Botrylloides violaceus growing into each other on a settling plate. You can still see the boundaries between the colonies, which are distinct in coloration, and the arrangement of zooids.

*As always, please do not use images without permission from the contributor.