The Exotics Guide

Botryllus schlosseri Image 9-dark orange on mussel

A Botryllus schlosseri colony with dark orange zooids, growing on a bay mussel (Mytilus trossulus/ galloprovincialis complex) in San Francisco Bay.

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Botryllus schlosseri Image 8-detail of white, tan & yellow

Detail of colony in previous photo. Note the small white blobs arranged like beads around the outer rim of the colony, which are the pigmented ends of blood vessels.

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Botryllus schlosseri Image 7-white, tan & yellow

A Botryllus schlosseri colony with white, tan and yellow zooids, growing on a sheet-like green seaweed (Ulva sp.) in San Francisco Bay.

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Botryllus schlosseri Image 6-detail of previous orange

Detail of previous photo showing a system made up of 12 zooids. Note the oral apertures, appearing as darker orange pores in the teardrop-shaped zooids.

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Botryllus schlosseri Image 5-orange from SFBay

A Botryllus schlosseri colony with orange zooids from San Francisco Bay.

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Botryllus schlosseri Image 4-detail of white & black

Detail of previous photo showing a system made up of 12 zooids. Note the red-tinted oral apertures on the top surfaces of the white zooids, and the opening in the center of the system where water exits the colony.

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Botryllus schlosseri Image 3-white & black

A Botryllus schlosseri colony with white and black zooids, growing over the surface of a solitary tunicate (probably Ascidia sp.) in San Francisco Bay.

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Botryllus schlosseri Image 2 & Key

Detail of colony in previous photo.

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Botryllus schlosseri Image 1-orange from SFBay

A Botryllus schlosseri colony with orange zooids from San Francisco Bay.

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Botryllus schlosseri Pallas, 1766

STAR SEA SQUIRT, GOLDEN STAR TUNICATE

  • Kingdom: Animalia
  • Phylum: Chordata
  • Subphylum: Tunicata
  • Class: Ascidiacea
  • Order: Stolidobranchia
  • Family: Styelidae

Botryllus schlosseri is a colonial sea squirt that typically forms flat sheets 3-4 mm thick and up to 10 cm across. Colonies that overgrow narrow-bladed seaweeds may appear lobate, and colonies growing in stalked, fleshy lobes have been reported in southern Australia.

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