2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

Monday, September 24, 2012
Chair: Phillip Gienapp
�63 Frederico Henning A 703 / 14:00
Genetics of polychromatism in the Midas cichlid
Authors: Frederico Henning 1 , Shoji Fukamachi 2 , Julia Jones 1 , Paolo Franchini 1 , Axel
Meyer 1
Affiliations: 1 University of Konstanz; 2 Japan Woman's University
Theoretical advances in speciation research have come a long way since the dawn of
the new synthesis. The genetic architectures and ecological factors that are more
conducive to speciation, with or without geographic isolation, have been identified.
Testing these theoretical predictions requires knowledge of the genetics of traits
underlying reproductive isolation in addition to the ecological parameters that result
in selection. Such information is not easy to obtain in non-model organisms, and
empirical data is still lacking. The Midas cichlids of Nicaragua are an excellent study
system for conducting such an investigation. In these fish a color polymorphism exists
in many different populations. The majority of each population has normal greyish
coloration and a proportion of the population undergoes melanophore cell death,
resulting in an amelanic morph that is gold colored. The onset of morphological color
is variable. Several studies have reported that mating is assortative with regard to
color, and interestingly,, incipient speciation based on this trait has been proposed.
The results of genetic mapping, candidate-gene, genotype-phenotype association and
analysis of differential expression have led to a much more comprehensive view of
the genetic basis of this phenotype. We show that the gold phenotype is dominant
and coded by a single mendelian locus, termed gold. In addition, we describe
codominant inheritance of pleiotropic traits of ecological significance. Melanophore
cell death occurs as early as 6-7 months of age and there is evidence that some
genetically gold fish remain untransformed throughout their lives. Transcriptomic
analysis of the downstream effects of gold revealed the upregulation of chemokines,
early immediate response genes and surprisingly, anti-apoptotic regulators during
color change. As expected, genes within the melanin biosynthesis pathway were all
down regulated after color change. Genes down regulated in gold fish included novel
candidate color-genes but also several well-known color genes that are responsible
for convergent phenotypes in many taxonomic levels, from zebrafish to man.
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