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Thalia democratica


Brook Anderson (2013)     


Fact Sheet



Physical Description

Sexual Form

Asexual Form


Biogeographical Location

Feeding Ecology

Life History & Behaviour

Asexual Reproduction

Sexual Reproduction

Anatomy & Physiology

Sensory System

Muscular System

Feeding Structures and Function

Evolution & Systematics

Conservation & Threats

References & Links


The body form of the sexual individual ranges between 1.8 and 18.2 millimeters in length along the oral-aboral axis.The body is surrounded by a thin test.  The body is oval shaped and tapers off to a pointed terminal process at the aboral end. The body is asymmetrical with a small lateral protuberance on one side. Both openings are present on the dorsal side; the oral opening central and the atrial opening situated just off centre. A variable number of tubular extensions range from the mantle to the outer test.

Like the asexual body form, the sexual body form consists of 5 continuous circular muscles (labeled M1 to M5). A fusion of muscles M1- M3, and M4 - M5 occurs mid dorsally. A large separation is present dorsally between the two groups of muscles (M1 – M3 & M4 – M5).

An internal gut is present ventrally in the posterior end of the individual. It is more compact than the gut in solitary forms and when grouped with the intestines comprises the nucleus. Located on the anterio-dorsal surface of the animal is a small circular eye spot, on which the dorsal ganglion is situated. Directly anterior to this spot is the dorsal tubercle. Due to the transparency of the animals, an internal dorsal lamina is evident running along the anterior-posterior axis of the body from the eye spot to the posterior nucleus. An endostyle is also present ventral to the dorsal lamina running along the anterior–posterior axis, terminating mid dorsally.