Physical Description

Phalusia julinea is a large solitary ascidian, mainly characterized by its bright yellow colour, explaining its common name: the yellow sea squirt.

The size and shape of solitary ascidians are highly variable and may look like seed, potato, grape or peach. The shape of the yellow sea squirt can vary from being long andclub-shaped to curved, however most are laterally flattened (Kott 1985). While some individuals have been recorded to be as big as 15cm(Kott 1985), most are about 5cm long.

The yellow sea squirt has two indented siphons used to intake and reject water. One oral (also called branchial) siphon located on the posterior end of the ascidian, through which water enters the body, and one atrial siphon located along the dorsal side of the body, through which the waters evacuates the body (see photo) (Peterson 2007).

One of the specimen of Phallusia julinea found on the Heron Island Reef.

Did you know? Some species of Ascidian look very closely like sponges. How can we differentiate them? Easy, Ascidians can react to movement, touch them with your finger and they will retract on themselves, while sponges will not do anything as they do not have a nervous system.

Identification

The following website is a good help in identifying ascidian species.
http://ascidians.com/