by Xavier Turon
We
are happy to announce that a new paper has been published with the
results of a study of the chimerism in Didemnum
vexillum:
M.
Casso, D. Tagliapietra, X. Turon, M. Pascual. «
High fusibility and chimera prevalence in an invasive colonial ascidian
» Scientific
Reports,
octubre del 2019. Doi: 10.1038/s41598-019-51950-y
In
this study, which is part of Maria Casso’s PhD on the global
invader Didemnum
vexillum,
we applied whole genome amplification protocols (WGA) and
genotyping-by-sequencing techniques (GBS) to genotype individual
zooids of the colonies. With this method we could investigate if the
colonies were genetically homogeneous or were chimeric, that is,
comprise zooids with different genotypes.
The
results reveal that 44% of the colonies of D.
vexillum
in a natural population in the Ebro Delta (NE Iberian Peninsula) are
chimeric. According to the study, this ability to create chimeras
could be a determining factor to promote genetic diversity and the
colonizing success of this exotic species in natural ecosystems
worldwide.
Chimera
formation in colonial forms proceeds through fusion of neighbouring
colonies. Another objective of the article was to determine whether
the ascidian colonies that merged were genetically more similar than
those showing rejection. With this goal, we analysed the merging
process in ascidian colonies in the Venetian Lagoon through an
experimental protocol that put in contact samples from the same
colony and fragments from different ones.
The colonies that merged in the experiments
carried out in the Institute of Marine Sciences in Venice (Italy) did
not share more genomic similarities than those that did not merge.
Therefore, there were not genetic differences globally between both
analysed groups, except for some loci or genomic regions –with an
unknown biological function due the lack of reference genomes- where
there was a major similarity regarding genetics. These loci deserve
further investigation to determine their role in the fusion/rejection
reaction.