Marching to the beat of the Bongo

Blog post by Karen Holm, DVM, Klaus-Peter Koepfli, PhD, and H.C. Lim, PhD


The Eastern mountain bongo (Tragelaphus eurycerus isaaci) is the largest montane forest dwelling antelope species native to Kenya. The bongo is a member of the Bovidae family and the tribe Tragelaphini or spiral horned antelope, including eland, nyala and sitatunga (Bibi, 2013; Chen et al. 2019). They weigh-in around 200-280kg of body weight and females carry horns as well as the males. They are a rare and elusive species with fewer than 100 surviving in 5 isolated populations in Kenya. Therefore, the IUCN Red List of Threatened Species considers the Eastern mountain bongo Critically Endangered. Another subspecies, the Western bongo, differentiated by morphological and phenotypic evidence, extends across the Dahomey Gap from the Democratic Republic of the Congo to Sierra Leone and is disjunct from the Eastern subspecies.

Young bongo, image courtesy of Karen Holm [[CC]]

Conservation efforts of the Eastern subspecies have included a repatriation in 2004 of 18 animals to a semi-captive population at the Mount Kenya Conservancy. There have been many successful births and the herd is growing. In 2019, the Kenya Wildlife Service put together a national recovery and action plan for the Eastern mountain bongo for 2019-2023.


Bongos are unique in that females have 34 chromosomes and males have 33, with an acrocentric Y chromosome that is fused with one of the smaller chromosomeS. In addition, two types of X chromosomes exist, one being acrocentric and the other submetacentric, with the acrocentric X being similar to other tragelaphine antelopes (Benirschke et al., 1982).


Today we share the chromosome-length assembly for the Eastern Mountain Bongo. We thank The Wildlife Conservation Center in Virginia for providing the sample for the initial 10x Genomics Chromium linked-read and Supernova 2.0 de novo assembly, which was funded and assembled by H.C. Lim in the George Mason University Evolutionary Genomics Lab. The genome was then analyzed and annotated by Karen Holm, DVM. This draft assembly is in the process of being written up and published.


We also thank Bernadette and Howard, the two eastern bongos at the Houston Zoo who have provided samples for the chromosome-length Hi-C upgrade. (Read more exciting news from the eastern bongo family at the Houston Zoo here!)


See below how the chromosomes of the eastern bongo (2n=33/34) relate to those of cattle (2n=60).

Whole-genome alignment plot between the bongo (barney_pseudo2.1_HiC) and cattle (Bos_taurus_UMD_3.1.1) genome assemblies.

Citations:

Benirschke, K., Kumamoto, A., Esra, G., & Crocker, K. (1982). The chromosomes of the bongo, Taurotragus (Boocerus) eurycerus. Cytogenetic and Genome Research, 34(1-2), 10-18. doi:10.1159/000131788


Bibi, F. (2013). A multi-calibrated mitochondrial phylogeny of extant Bovidae (Artiodactyla, Ruminantia) and the importance of the fossil record to systematics. BMC Evolutionary Biology, 13(1), 166. doi:10.1186/1471-2148-13-166


Chen, L., Qiu, Q., Jiang, Y., Wang, K., Lin, Z., Li, Z., . . . Wang, W. (2019). Large-scale ruminant genome sequencing provides insights into their evolution and distinct traits. Science, 364(6446). doi:10.1126/science.aav6202

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