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.