The North Sulawesi babirusa (Babyrousa celebensis) is a member of the Suidae family native to swampy forests of Indonesia. Their famous tusks have inspired generations of art and folklore in Indonesia, where the tusks of the babirusa are often featured in traditional masks. The upper tusks of male babirusas will continue to grow throughout their lifetime, eventually curling over the head if not worn down through fights with other males. Female babirusas are easy to identify as they lack upper tusks [1]. Babirusas are great swimmers and spend much of their time wallowing in the mud to keep cool and protect their skin.
Due to deforestation of the natural habit and excessive hunting, the wild population of the babirusa is drastically declining. The ICUN Redlist has categorized the Sulawesi babirusa as vulnerable. As babirusas do not easily breed in captivity, breeding programs haven't been able to keep up with the rate of decline of the wild population.
Today, we share the chromosome-length assembly for the North Sulawesi babirusa, Babyrousa celebensis. This is a $1K de novo genome assembly, with a contig n50 of 53 Kb and a scaffold n50 of 113 Mb. For details on assembly procedure, check out Dudchenko et al., 2018 or our Methods page. We thank Remley from the Houston Zoo for providing the sample that has made this genome assembly possible! Read more about Remley and her partner Jambi in this featured blog post by the Houston Zoo celebrating National Pig Day (March 1st).
Check out how the chromosomes in the new assembly align with those of the domestic pig Sus scrofa (assembly by Warr et al., 2020) in a whole-genome alignment plot below. While both of these Suidae species have a karyotype of 2n=38, there are considerable differences including two chromosome breakages (#3 and #6 in the domestic pig), two fusions (#13+#16; #15+#17 in domestic pig) and a big inversion on the pig chromosome #1 equivalent.
Interestingly, in 2006, a zoo in Copenhagen managed to cross a different babirusa species (B. babyrussa) with the domestic pig, leading to hybrid offspring [2]. Previously thought to be sexually incompatible due to genetic distance of the species, the cross produced three surviving offspring. The hybrids were sterile though, which is probably at least in part due to chromosomal differences between the crossed species similar to the one shown above. Reach out if you have a B. babyrussa sample to confirm!