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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

External features

B. tuberatus are often dark-coloured ascidians covered in a translucent test.  Living zooids can range from being orange to red to purple (Abbott & Newberry 1980; Kott 1985).  They occur in colonies that are generally isolated from one another.  B. tuberatus usually has less than 12 zooids per colony, while each colony has a common cloacal aperture in the center, as seen in figure 1 below.  
Figure 1. Image showing a colony of B. tuberatus and the common cloacal aperture.  The individual zooids are labelled from 1-10.  

In addition to that, it has been observed in the current specimen that tentacles are present at the entrance of the incurrent aperture of each individual zooids, as seen in figure 2 below.  Strategically positioned at the entrance of the incurrent aperture, the tentacles are used in preventing large particles from entering the branchial basket and clogging up the ascidian (Cima et al. 2006).  

Figure 2. Image showing the incurrent aperture of an individual zooid.  Arrows point to the tentacles at the entrance.