A first annotated genome sequence for Haliotis midae with genomic insights into abalone evolution and traits of economic importance

Abstract

Haliotis midae or "perlemoen" is one of five abalone species endemic to South Africa, and being palatable, the only commercially important abalone species with a high international demand. The higher demand for this abalone species has resulted in the decrease of natural stocks due to overexploitation by capture fisheries and poaching. Facilitating aquaculture production of H. midae should assist in minimising the pressure on the wild populations. Here, the draft genome of H. midae has been sequenced, assembled, and annotated. The draft assembly resulted in a total length of 1.5 Gb, contig N50 of 0.238 Mb, scaffold N50 of 0. 238 Mb and GC level of 40%. Gene annotation, combining ab initio and evidence-based pipelines identified 52,280 genes with protein coding potential. The genes identified were used to predict orthologous genes shared among the four other abalone species (H. laevigata, H. rubra, H. discus hannai and H. rufescens) and 4702 orthologous genes were shared across the five species. Among the orthologous genes in abalones, single copy genes were further analysed for signatures of selection and several molecular regulatory proteins involved in developmental functions were found to be under positive selection in specific abalone lineages. Furthermore, whole genome SNP-based phylogenomic assessment was performed to confirm the evolutionary relationship among the considered abalone species with draft genomes, reaffirming that H. midae is closely related to the Australian Greenlip (H. laevigata) and Blacklip (H. rubra). The study assists in the understanding of genes related to various biological systems underscoring the evolution and development of abalones, with potential applications for genetic improvement of commercial stocks.

Keywords: Adaptation; Aquaculture; Genome evolution; Growth; Haliotids; Molecular breeding.