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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

Sexual Reproduction

As with all other Botryllus species, B. tuberatus undergo sexual reproduction in late spring to early summer.  They are hermaphroditic and typically cross-fertilize (Ruppert, Fox & Barnes 2004).  The colonies reach sexual maturity in 1-2 month's time (Abbott & Newberry 1980).  Testes have not been observed in this species, potentially due to the minimal data collected worldwide.  Eggs, on the other hand, are present on each side of the body as part of the test-vessel system (Abbott & Newberry 1980; Kott 1985).  Fertilized eggs are brooded and retained in the zooid until the larvae are ready to swim.  Then, they would be released together with the continual flow of water through the excurrent aperture and cloacal aperture (Abbott & Newberry 1980).  Since B. tuberatus are sessile marine organisms, this constitutes the dispersal phase for the organism as the larvae are free-swimming (Pennati et al. 2009).  The young larvae has adhesive papillae on its anterior end used in sensing the environment for suitable substrate to settle on (Pennati et al. 2009).