Genome assembly of the numbat (Myrmecobius fasciatus), the only termitivorous marsupial

Abstract

The numbat (Myrmecobius fasciatus) is a critically endangered Australian marsupial, and the last surviving member of the Myrmecobiidae family. The numbat regularly undergoes torpor and is unique amongst marsupials as it is the only diurnal and termitivorous species. Here we sequenced the first draft genome of the numbat using 10x Genomics chromium linked-read technology, resulting in a 3.42 Gbp genome with a scaffold N50 of 223 Kbp. A global transcriptome from liver, lung and tongue was also generated to aid genome annotation with Fgenesh++, identifying 21,465 protein-coding genes and 78.7% complete mammalian BUSCOs. To investigate adaptation to the numbats termitivorous diet and arid/semi-arid range, we interrogated the most highly expressed transcripts within the tongue and manually annotated taste, vomeronasal and aquaporin gene families. Antimicrobial proteins and proteins involved in digestion were highly expressed in the tongue, as expected. Similarly, umami taste receptors were also expressed in the tongue, however sweet taste receptors were not expressed in this tissue. This pattern of taste receptor expression, combined with the putative contraction of the bitter taste receptor gene repertoire in the numbat genome, may indicate a potential evolutionary adaptation to their specialized termitivorous diet. Vomeronasal and aquaporin gene repertoires were similar to other marsupials and have not undergone expansion or contraction. The draft numbat genome is a valuable tool for conservation and can be applied to population genetics/genomics studies and to investigate the unique biology of this interesting species.