Wombats are herbivores with CDCA and 15-alpha-OH as the major bile salts

The wombat looks like a overgrown rat or even a cat with rat like features. However, it is neither a rodent nor a carnivore. Being a marsupial confined in its geographic distribution to Australia, many of us have probably never seen it. However, it does look similar to the koala bear in someways. Their claws and front teeth are used for burrowing as well as eating tough vegetation. These species feed on roots and bark. A very slow metabolism has been documented and is thought to help them survive in arid environments.

By JJ Harrison (jjharrison89@facebook.com) - Own work, CC BY-SA 3.0, Link

The bile composition of the wombat (Vombatus ursinus) has been quantified using HPLC. It mainly consists of CDCA and 15-alpha OH bile acids. It is unclear whether the other two species of Northern and Southern hairy-nosed wombats (Lasiorhinus krefftii & latifrons) have a similar bile content. Given the frequent changes in bile composition of closely related species, it is possible that bile composition might be different in these other species.

Shinde et al., explores the signatures of relaxed selection in the CYP8B1 gene and finds strong patterns of relaxed selection in the wombat CYP8B1 gene. The time between biorxiving and acceptance of the paper is fairly short given the fast turnaround time of the journal of molecular evolution. All the code used for the analysis along with detailed instructions are posted on the github-CYP8B1 page that goes with the paper. In addition to the striking pattern of relaxation seen in the wombat CYP8B1 gene sequence the manuscript also explores few other aspects related to cetaceans, birds, afrotheria and technical challenges associated with detecting relaxed selection and gene loss. By investigating population level variability of the gene in chicken, we are able to identify the CYP8B1 gene that is not annotated in the latest build of the Gallus gallus genome. Located beside the ACKR2 gene seen in the picture below, it is conserved across a large number of chicken breeds despite having acquired a stop codon in the genome of the individual used for performing genome assembly. Future versions of the chicken genome will hopefully annotate this gene.

Figure 1: Lack of annotation for the CYP8B1 gene in the chicken genome.