Botryllus: Burgundy Color Variants

At the beginning of the season, the typical star-shaped Botryllus schlosseri color variants with a burgundy body and white inter-siphon pigment bands forming an actual white star was one of the most prevalent color variants.  But as the summer progressed, the number and variations of color variants increased, including the burgundy colonies.  Their appearance in daylight or under incandescent light varied depending on substrate (light green sea lettuce, dark green Codium, brown algae, red algae, mussel shell, Styela) and background setting (on the dock, in collection containers, or on a black or white microscope stage). In this post, I show a few of the burgundy color variants collected from Provincetown and Salem Sound during the summer.

   Burgundy Botryllus schlosseri Variant on Green Algae - White Star

Botryllus schlosseri on Ulva, MacMillan Wharf, Provincetown, MA, September, 2011.  Green back-lighting through the algae clearly outlines the zooids.   White pigment cells form a pair of curved bands between the branchial and excurrent siphons giving the bands a daisy-star appearance.  Stereozoom 1.0 x 10x.  

Burgundy Variants with Inter-siphon White Shield

 

Botryllus schlosseri on Codium, MacMillan Wharf, September, 2011. White pigment cells form a shield-shaped pattern filling the space between the branchial and excurrent siphons of the cluster. The zooids also have a tiny patch of white cells on the opposite, outer side of the branchial siphon at the anterior end of the endostyle.  Othewise, the branchial siphons are burgundy like the rest of the zooid body. Stereozoom 3.0 x 10x.

 Burgundy Variant on Red Algae, White Branchial Crescent with Atrial Ring

 

Nine-zooid cluster of Botryllus schlosseri on red algae, MacMillan Wharf, October, 2011. Scattered white pigment cells encircle the orange-colored branchial siphon, more heavily on the outer side of the cluster. The common excurrent siphon is outlined by a dashed ring of white pigment cells formed by a short, white stripe at the atrial opening of each zooid.  Stereozoom 1.5 x 10x.

Ampullae of Burgundy Variant on Red Algae - White-Capped

 

Same colony of Botryllus schlosseri on red algae as shown above.   The zooids share a common vascular system that consists of blood vessels and enlarged club-shaped vascular ampullae along the periphery. The ampullae have the capacity to reconstruct the colony by vascular budding if all the zooids are lost.  Top, ampullae define the edge of the colony and separate clusters of zooids.    Bottom, white pigmented cells concentrate at the distal ends of burgundy ampullae like snow-capped boulders. 

Burgundy Variant on Red Algae - Diffuse White Branchial Stripe

Botryllus schlosseri on red algae, MacMillan Wharf, September, 2011.  White pigment cells form a short stripe through the branchial siphon above the endostyle and dorsal lamina.  Pigment cells also lightly speckle the body of the zooid.  Branchial siphons are orange-colored. Top, two 7-zooid and 10-zooid clusters.  Stereozoom 2.0 x 10x.  Bottom, close-up view of branchial siphons and diffuse white stripe.  Stereozoom 3.0 x 10x.  

LINK:

CE Carver, AL Mallet, and B Vercaemer, Biological Synopsis of the colonial tunicates, Botryllus schlosseri and Botrylloides violaceus