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New insights into sea squirt physiology allow for better inland cultures

By conducting systematic observations of animals in the laboratory, researchers in the Christiaen group uncovered crucial information on the post-embryonic development of Ciona. Their results, including a new culture protocol, are published in Open Biology.

Birthe Thuesen Mathiesen in the Ciona facility
Head Engineer Birthe Thuesen Mathiesen contributed to establishing a new inland culture system for ascidians at the Michael Sars Centre.
Photo:
Marion Lebouvier

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While their appearance may not immediately evoke the animal kingdom to the untrained eye, ascidians – also called sea squirts – are closely related to vertebrates. Their bag-like tunic hides a heart pumping blood throughout their body, and larvae have a brain sensing their environment in great detail. These features make them a popular model for developmental biologists, but the animals’ life cycle is not easily completed in the laboratory and most studies depend on unreliable field collection. In a new article published in Open Biology, a team of researchers led by Postdoctoral Fellow Naoyuki Ohta and Head Engineer Birthe Thuesen Mathiesen from the group of Lionel Christiaen reveal the missing elements for a successful culture of two sea squirt species in the genus Ciona.

“We cultured animals as "Ciona culture team", each member had his or her own animals, and maintained and observed to get information about animals' growth and maturation”, explains Ohta. By analyzing the wealth of data resulting from these observations, the team discovered growth thresholds in the maturation of Ciona. This allowed them to establish a simple protocol for inland culture that uses size selection to optimize sexual maturation. “I am happy being a part of the team in the Christiaen lab which developed a new protocol for growing juvenile Ciona into healthy animals producing both sperm and eggs for experiments”, says Thuesen Mathiesen. “I found it especially exciting to discover that we were able to produce eggs of both quantity and quality to do successful electroporation.”

“Now, we cleared concerns on protocols for inland culturing, so it is time to aim for transgenic animals.”
- Naoyuki Ohta

The availability of model organisms is a major limiting factor in the laboratory. With the new protocol in place, the team looks forward to taking their research projects to the next level. “My main goal in this lab is to establish transgenic animals as a powerful tool for genetics”, says Ohta. “Now, we cleared concerns on protocols for inland culturing, so it is time to aim for transgenic animals.”