Monitoring at MacMillan Wharf, Provincetown, MA

Monitoring at MacMillan Wharf, Provincetown, MA
Marine Invasive Species (MIS) Monitoring at MacMillan Wharf, Provincetown, MA.

Friday, December 9, 2011

New Ascidian Images on Tunicarium

Botryllus schlosseri is another beautiful colonial ascidian whose single and multi-color variants make for an amazing number of color morphs.  These colorful ascidans, like Botrylloides violaceus (Nov. 11 Post), make for terrific underwater photographs that I thought would transcend directly to the stereomicroscope.  It did to an extent; however, like with Botrylloides, structural detail was easier to capture with the lighter color variants.  Some of the stereomicrographs from this summer's monitoring of Cape Cod and Salem Sound marinas are now featured on Tunicarium, including images of the invasive ascidians Botrylloides violaceus, Botryllus schlosseri, and Didemnum vexillum.  

Botryllus schlosseri was a challenging colonial to capture under fiber optic lighting. The variants with dark-colored zooids blended in with the backgrounds making difficult the photography of structural detail.  With the light color variants against a darker background, the two-toned beige, which formed a mosaic-patterned colony, and single-colored orange colonies proved to be highly photogenic.

To capture the zooids with open siphons, I tried Gretchen Lambert's technique for relaxation with menthol crystals.  It was terrific for relaxing ascidians as well as other invertebrates.  But as with any approach, I found relaxation had its pros and cons for viewing as well as photomicrography.  Relaxation greatly reduced contraction ability, but also inhibited the ability of zooids to fully expand. Lack of anesthesia was challenging under bright light because individual zooids reacted to the light independently, each zooid in a cluster randomly closing and re-opening during photography.  My objective was to obtain images where all the branchial siphons in the field of view were fully open.  It made for some interesting and entertaining time-sequence shots.    

The images below are two of my favorites.  They demonstrate the difference between the information revealed capturing images of light vs. dark Botryllus color variants and show zooid structural and pigment cell details that cannot be seen solely by underwater photography.  The 40X original magnification generated images with the greatest resolution and zooid detail (4X zoom + 10X objective lens).  These details can also be seen out in the field with the 30-40X jeweler's loupe magnifying glasses that I discussed in the Nov. 25 Post.  The beige variant gave vivid zooid detail, whereas the typical white star on dark purple was outstanding for showing cells in the pigment bands.

Botryllus schlosseri Beige-Rust Mosaic Variant
Botryllus schlosseri growing on the green algae Codium fragile collected from MacMillan Wharf, Provincetown, MA. Zooids have a translucent beige color revealing the tips of the branchial tentacles and pale rust-orange cells in the pigment bands. 

Botryllus schlosseri White Star Variant with Parallel Pigment Bands.
Botryllus schlosseri growing on Codium collected from MacMillan Wharf, Provincetown, MA.  Four branchial openings are seen at the top with 4 pairs of white pigment bands leading to the single, common atrial aperture at the bottom center.  

The full collection of images on Tunicarium can be seen all together on Google Images that has been web-searched using the word "Tunicarium".  The photos are featured in thumbnail view and can be "double-clicked" to see the jpg files saved on the website.  Larger sized micrographs can be obtained from me by request at