Abstracts (first author)
Adaptive evolution of the opsin genes in African crater lake cichlids?
Cichlid fishes from volcanic crater lakes represent small radiating lineages usually of few species. The Barombi Mbo Lake in Cameroon hosts a species flock of tilapiine cichlids, which underwent adaptive radiation similar to more famous Great Lakes cichlids. Several ecological adaptations were observed either in morphology of trophic apparatus (leading to feeding specializations) or extreme habitat preferences, such as deep-water niche. In general, cichlids are mainly visually oriented animals and their visual system shows in many cases the additional adaptations to the environment including the deep waters. Two ways of adaptation were found in cichlids from the Great Lakes, first in the DNA-sequence tuning and second in the gene expression levels differenciation. In the deep-water species convergently evolved mutations are known in opsin genes causing the shift of the chromophore sensitivity. The Barombi lake hosts a deep-water living species Konia dikume, however, nothing is known about the opsin evolution in these small crater lake systems so far. We sequenced a large region (up to 10 kbp) of each of the seven cone opsins (and putative regulatory regions) using the amplicon sequencing in the Ion Torrent next-generation sequencer. We further performed whole-transcriptome sequencing on the Ion Torrent next-generation sequencer to reconstruct robust phylogeny and we reconstruct evolution of the opsin genes by mapping on the tree. We further estimated the expression levels of all seven cone opsin genes, as well as the rod opsin. We found faster mutation rate in opsin genes in the genus Stomatepia (three species) and higher allelic variation within the genus Sarotherodon, however no DNA tuning has been found in Konia dikume.