Botrylloides violaceus Oka, 1927

Botrylloides violaceus is a colonial sea squirt that forms flat sheets that are irregular in outline and adhere to the substrate, with large colonies reaching up to a third of a meter or so in diameter. It grows on a variety of surfaces, include docks, boat hulls, buoys, ropes, pilings, the undersides of rocks, eelgrass (Zostera marina) blades and seaweeds. It often overgrows mussels, barnacles, encrusting bryozoans and solitary sea squirts.

Return to Top

Botrylloides violaceus

Luis A. Solórzano

An orange Botrylloides violaceus colony on a bay mussel (Mytilus trossulus-galloprovincialis complex) in San Francisco Bay. Note the meandering double rows of zooids that are characteristic of this species.

Luis A. Solórzano

A Botrylloides violaceus colony in which many of the zooids appear to be in oval systems like those in Botryllus schlosseri. However, the narrow ends of the teardrop-shaped zooids point away from the ovals, and the ends of blood vessels appear as small blobs within the ovals (see enlarged image).

James T. Carlton

Botrylloides violaceus colonies of several different colors growing on a tire hanging from a dock in Willapa Bay, Washington.

Gretchen Lambert

Orange and red colonies of Botrylloides violaceus growing on ropes in Tomales and San Francisco bays. A yellow sponge (Halichondria bowerbanki) and a tan bushy bryozoan (Bugula sp.) are also present in the right-hand photo.

Gretchen Lambert

A red colony of Botrylloides violaceus overgrowing the sponge Halichondria bowerbanki in San Francisco Bay.

Washington Dept. of Natural Resources

A large orange colony of Botrylloides violaceus growing on seaweed in Puget Sound.

Luis A. Solórzano

Closeup of a small tan colony of Botrylloides violaceus, growing on a solitary sea squirt Molgula manhattensis, in San Francisco Bay. The pigmented ends of numerous blood vessels are visible along the right side of the colony.

California Academy of Sciences

Closeup of two adjoining colonies of Botrylloides violaceus in San Francisco Bay. The pigmented ends of blood vessels are visible between the zooids.

Leslie Harris, NHMLAC

A Botrylloides violaceus larva. Note the large number of fingerlike larval ampullae (about 18 visible in the photo) on the head (at left in image).

Luis A. Solórzano

Closeup of an orange colony of Botrylloides diegensis in San Francisco Bay.

Watersipora Image 8

Closeup of Watersipora subtorquata zooecia from San Francisco Bay, showing the black opercula and the fine black lines where the zooecia join. The two round “windows” (thinner, translucent areas) in each operculum are characteristic of this species.

Return to Top

Watersipora Image 8

Watersipora Image 7 & Key

Closeup of a red Watersipora subtorquata colony in San Francisco Bay, showing the black opercula

Return to Top

Watersipora Image 7 & Key

Watersipora Image 6

A large red colony of Watersipora subtorquata (about 10 x 15 cm) from the side of a dock in San Francisco Bay.

Return to Top

Watersipora Image 6

Watersipora Image 5

Closer view of a smaller orange Watersipora subtorquata colony from San Francisco Bay.

Return to Top

Watersipora Image 5

Watersipora Image 4

A large, orange Watersipora subtorquata colony from the side of a dock in San Francisco Bay. The colony’s edges have grown up from the substrate in frilly lobes.

Return to Top

Watersipora Image 4

Watersipora Image 3

An old Watersipora subtorquata colony covering a rock in San Francisco Bay. The tubes of the polychaete worm Ficopomatus enigmatus, the oyster drill Urosalpinx cinerea, and the egg cases of the drill are all visible in the image.

Return to Top

Watersipora Image 3

Watersipora Image 2

An old Watersipora subtorquata colony on a rock in San Francisco Bay. Most of the colony is black, with only the outer rim colored red.

Return to Top

Watersipora Image 2

Watersipora Image 1

A small, flat Watersipora subtorquata colony encrusting the underside of an intertidal rock in San Francisco Bay. The colony is mainly red, with a blackened central portion and black opercula. The orange bryozoan in the lower left of the image is Schizoporella unicornis.

Return to Top

Watersipora Image 1

Watersipora subtorquata d'Orbigny, 1852

Watersipora subtorquata is a type of colonial animal called a bryozoan. It grows on a variety of hard substrates including rocks, shells, docks, vessel hulls, pilings, debris, kelp holdfasts, and other bryozoans. On flat surfaces the smaller colonies, up to several centimeters in diameter, are flat and roughly circular. As a colony grows larger it becomes more lobed and may overgrow itself in places.

Return to Top

Watersipora subtorquata

Andrew N. Cohen

A small, flat Watersipora subtorquata colony encrusting the underside of an intertidal rock in San Francisco Bay. The colony is mainly red, with a blackened central portion and black opercula. The orange bryozoan in the lower left of the image is Schizoporella unicornis.

Andrew N. Cohen

An old Watersipora subtorquata colony on a rock in San Francisco Bay. Most of the colony is black, with only the outer rim colored red.

Andrew N. Cohen

An old Watersipora subtorquata colony covering a rock in San Francisco Bay. The tubes of the polychaete worm Ficopomatus enigmatus, the oyster drill Urosalpinx cinerea, and the egg cases of the drill are all visible in the image.

Luis A. Solórzano

A large, orange Watersipora subtorquata colony from the side of a dock in San Francisco Bay. The colony’s edges have grown up from the substrate in frilly lobes.

Luis A. Solórzano

Closer view of a smaller orange Watersipora subtorquata colony from San Francisco Bay.

California Academy of Sciences

A large red colony of Watersipora subtorquata (about 10 x 15 cm) from the side of a dock in San Francisco Bay.

Andrew N. Cohen

Closeup of a red Watersipora subtorquata colony in San Francisco Bay, showing the black opercula

California Academy of Sciences

Closeup of Watersipora subtorquata zooecia from San Francisco Bay, showing the black opercula and the fine black lines where the zooecia join. The two round “windows” (thinner, translucent areas) in each operculum are characteristic of this species.