Austrolebias charrua Genome sequencing. Austrolebias charrua

Annual fish of the genus Austrolebias are a rapidly evolving group of neotropical killifish (Cyprinidontiformes) endemic to the eastern seaboard of South America. Like other annual fish, they have adapted to withstand the seasonal desiccation of their habitat, temporary ponds in the grasslands of the Pampa, by producing embryos that can survive for months buried in the soil. The embryos undergo diapause, a reversible developmental arrest, and also show unique embryological features. While annualism has likely arisen multiple times among the Cyprinidontiformes, Austrolebias are a rapidly diverging genus distinguished by genomes that are 2-3 times the size of other their closest relatives with no evidence of multiploidization. We have de novo sequenced, assembled and annotated the genome of Austrolebias charrua, endemic to Uruguay and Southern Brazil, and report a genome size of 3.4Gb, one of the largest teleost genomes sequenced to date. We also sequenced the genome of a second annual fish that inhabits the same habitat, Cynopoecilus melanotaenia, a species that shared a common ancestor with Austrolebias ~25Mya, but which harbors a genome of only 1.0Gb. We report that the three-fold increase in genome size in A charrua relative to C melanotaenia is due to very recent amplification of mobile element sequences, most notably, LINE retrotransposons. This individual is from the first generation obtained from fish sampled from a wild-type population in Treinta y tres, Uruguay. Fish were husbandry and kept according to Papa et al. (2016), in 20L tanks filled with reverse osmosis filtered water reconstituted with marine salt (Tetra Marine Salt Pro, 300 uS, pH 7-7.5) with continuous recirculation and air bubbling. Fish were exposed to natural light, and the water temperature was maintained at 19 degrees. Specimens were fed once a day with live bloodworms and Daphnia magna.