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Botryllus tuberatus (Ritter & Forsyth, 1917)

Pacific Star Tunicate

Adeline Ang (2014)



Fact Sheet

Brief Summary

Physical Description

External Features

Internal Features

Slides Preparation


Life History & Behaviour

Feeding Mechanisms


Internal Transport & Movement

Asexual Reproduction

Sexual Reproduction

Anatomy & Physiology

Evolution & Systematics

Biogeographic Distribution

Biofouling Threats

References & Links

Brief Summary 

Image showing the external appearance of a single B. tuberatus colony (4mm by 3mm) on a settlement plate. 

Botryllus tuberatus (B. tuberatus) are often dark-coloured ascidians covered in a translucent test.  They are arranged circularly in colonies with a maximum of 12 zooids per colony.  Each colony as a common cloacal aperture in the center of each colony.  Identifying to the species level requires looking at the internal structures of the zooids (Kott 1985).
As with other ascidians, B. tuberatus are filter feeders that are able to undergo both sexual and asexual reproduction.  They are distributed all over the world, ranging from California, U.S.A to Japan to Philippines and around Australia (Abbott & Newberry 1980).  They are also considered to be a marine biofouling species (Rocha & Kremer 2005).