The addax (Addax nasomaculatus) is considered the most desert adapted antelope on the planet but is also among the most endangered, with less than 100 individuals left in the wild. Although the species was once found across the Sahelo-Saharan region of North Africa, they are now only present in a small area of Niger. Addax are able to live in extreme conditions and can face temperatures between -5 and 60 °C. They have large, flat hooves that allow them to walk across the desert without sinking into the sand and they rarely need to drink, since they obtain most of their liquids from the plants they eat, including wild melons. The primary threats faced by addax are hunting and changes in habitat use and their survival in the wild now relies on a series of large-scale reintroductions.
Fortunately, since the 1920s, addax have successfully been managed in captive populations across the globe. These insurance populations have proved invaluable for reintroductions and translocations into Tunisia, Morocco and Chad and will continue to represent a crucial component of addax management going forward. As part of this, researchers and conservationists are integrating genetic information into planning and decision making (Dicks et al. 2023). The availability of high quality genetic and genomic resources can therefore directly support addax conservation.
Today, we share a chromosome-length assembly for addax created using a combination of PacBio HiFi and Illumina Hi-C sequencing. PacBio HiFi sequencing was carried out at the University of Louisville Sequencing Technology Center from a male addax fibroblast cell line donated by the San Diego Frozen Zoo and contigged using HiFiasm (Cheng et al., 2021). The HiFi sequencing was made possible thanks to support from the Environment Agency – Abu Dhabi to the University of Edinburgh and the Royal Zoological Society of Scotland. Hi-C sequencing was carried out by the DNA Zoo using a blood sample donated by a female individual from SeaWorld.
Previously we shared an addax genome assembly using a draft generated by Hempel et al., 2021. The new genome assembly dramatically improves the contiguity of the assembly, boosting contig N50 from 10kb to 65.7Mb. We hope that this improved chromosome-level assembly will serve as an important backbone for future studies investigating this beautiful species of antelope on the brink of extinction.
Check out the chromosome-length contact map of the new addax reference below, and follow the assembly link for more details and info!