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Christian Sardet
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Species of ascidians and their uses

(most photos are from David Luquet our scubadiver and collector )




Phallusia mammillata


 Phallusia mammillata is our favorite species for studying fertilization and development. We collect  these ascidians in great numbers in Sete on the Mediterranean and find them in smaller numbers in  the bay of Villefranche .
 They also grow as big as 10 cm along the Atlantic coasts of Europe.Phallusias are hermaphrodites  and make gametes in abundance throughout the year (best months are may through november).  We can control fertilization and culture large numbers of synchronous embryos (see our methods).  Phallusia eggs develop into tadpoles in 15 hours and into juveniles in 3 days. The transparent eggs and embryos are ideal for imaging. 



Ciona intestinalis and Ciona savigny



Ciona intestinalis is present on all coasts of the world, possibly propagated via attachment to boat hulls. It is a hermaphroditic self sterile solitary ascidian and the most commonly used species for the study of gene expression during development. Systematic studies of the expression of thousands of genes have been undertaken in Japan. The sequencing of the genome has been completed. Ciona can now be raised in the laboratory.

Ciona savigny is a closely related species which is now cultivated. The California group has reported the first embryonic mutants.






Halocynthia papillosa


Halocynthia papillosa
is a mediterranean species which has not been used for research.



Halocynthia roretzi


Halocynthia roretzi
is a large hermaphroditic and self sterile solitary ascidian found in the northern part of Japan. It is a favorite food sold on Japanese markets and even packaged lyophilized or dried. The large (400 micron diameter) and abundant eggs and embryos are used for remarkable micromanipulations. Cell lineages are well described from egg to tadpoles to juveniles. An expression screen is underway providing many marker genes for tissues and potential tissue determinants. This photo was taken in H. Nishida's lab, the animal at the right has shed sperm and eggs.

 

Microcosmus comestibilus

Microcosmus comestibilus, commonly called "violet", is found around the mediterranean and is abundant near Sete where its bright yellow inside is eaten

 

 




Botryllus schlosseri


Botryllus schlosseri
is a colonial ascidian made of many individuals sharing common openings. Fertilization and early development is internal. Colonies are clones which vary in colors. They have contributed to our knowledge of primitive immunity and self/non self recognition.





Clavellina lepadiformis



Clavellina lepadiformis
has big eggs and is fertilized internally.




Ascidiella aspersa


Ascidiella aspersa is a sturdy species present on the Atlantic coasts of Northern Europe. It is spreading throughout the mediterranean and the Northern atlantic coast of America. It has been used recently to study calcium signals and the cell cycle after fertilization.