The landscape of transposable element distribution in the genome of Neotropical fish Apareiodon sp. (Characiformes: Parodontidae).

Transposable elements (TEs) are widely present in eukaryotic genomes, where they can contribute to genome size and functional modifications. As new genomes are sequenced and annotated, more studies can be conducted regarding TE content, distribution, and genome evolution. TEs are extensively diversified in fish genomes resulting in an important role in genome and chromosome evolution. However, curated TE libraries are still scarce in non-model organisms, making it difficult to evaluate TE's impact on genomic modifications thoroughly. Here, we aimed to obtain a curated TE library from the neotropical fish Apareiodon sp. genome. The prospection and curation of the TE library resulted in 244 families from 18 superfamilies of DNA transposons and retrotransposons, which comprise about 10% of the genome, with most insertions fitting in one or a few families. A greater diversity of retrotransposon families is present, especially for Ty3 superfamily. Despite the greater number of retrotransposon families, DNA transposons are the most abundant in the genome, with 37% of all TE insertions belonging to the Tc1-Mariner superfamily. Complete TE copies were observed for almost all superfamilies, with most of the sequences on the Tc1-Mariner group. DNA transposons and SINEs presented older insertions in the genome, followed by LINEs and LTR retrotransposons. TE genome density is highest in the cs25 scaffold, and enriched for Helitron elements. With these data, allied to previous studies on chromosome evolution, we suggest that cs25 bears the W chromosome specific region of the Apareiodon sp. genome, with the presence of significant amount of Helitron insertions.