Kristineberg Marine Genomics

People involved:

John Bishop
Helen Sköld
Thomas Stach
Michael Thorndyke

Figure 1. Small colony of Diplosoma listerianum. Individuals enclosed in a common tunic grow on microscope slides.

Budding and Development

Figure 2. A colony of Botryllus schlosseri growing on sea weed. Individuals are arranged in star shaped aggregates around a common cloacal opening.

During asexual reproduction in colonial tunicates a new individual forms either from already differentiated tissue or from undifferentiated cells. Based on morphological criteria several types of budding have been characterized. However, little is known about the cellular and molecular mechanisms involved. We are interested in knowing whether the mechanisms used in embryonic development are switched on again during budding. In particular, we are interested in developmental mechanisms as they relate to stem cells in budding and specifically in brain regeneration during budding in adult tunicates. The capacity to produce a new individual, including a functional brain, by adult budding, is likely to have significant implication for medical studies.

Key questions:
· Which cells are proliferating in budding tunicates?
· How does a new brain form in colonial ascidians?
· What are the stem cells involved and where do they originate?

Interestingly, budding occurs in different evolutionary lineages within the tunicates. It is not known whether the same mechanisms are involved during budding in the separate tunicate taxa. We are applying a comparative evolutionary approach to learn about the plasticity in the developmental mechanisms and their evolutionary history.
Cultured species:
· Botryllus schlosseri (Styelidae, Stolidobranchiata)
· Diplosoma listerianum (Didemnidae, Aplousobranchiata)
· Perophora japonica (Perophoridae, Phlebobranchiata)
· Clavelina lepadiformis (Clavelinidae, Aplousobranchiata)
· more species will be cultured, when they become available

Figure 3. Budding in Diplosoma listerianum an aplousobranch ascidian.

Figure 4. Regeneration in Botryllus schlosseri, a stolidobranch ascidian. After removal of zooids a new individual develops.