Summary Description

Botrylloides leachii is an ascidian composed of many individual zooids growing together to form colonies. Zooids are small, up to 2 mm long but the entire colony can be quite large and greatly variable in colour from grey to red-brown and orange. Colonies are thin, irregular in shape and have a smooth, even surface. Zooids are crowded together in long curving and branching double-row systems with a common exhalent (atrial) siphon between them. The exhalent openings are very wide, exposing a large part of the internal organs of each zooid. Terminal ampullae are randomly distributed over the test surface in spaces between systems while at the colony borders they are often long and parallel to each other.