The genomes of the giraffe and the okapi - the two members of the family Giraffidae - have been sequenced for the first time in a paper published online this week in Nature Communications. The study provides genetic insights into how the giraffe’s unique body shape and physiology evolved, and aids our understanding of the evolution of hoofed animals.
Douglas Cavener, Morris Agaba and colleagues sequenced the whole genomes of two female Masai giraffes (Giraffa camelopardalis tippelskirchi) from the Masai Mara reserve in Kenya and the Nashville Zoo in the United States and one male okapi (Okapia johnstoni) from the White Oak Holdings in the United States. Their analysis showed that the giraffe’s stature and cardiovascular adaptations are likely to have evolved in parallel through changes in a small number of genes. Genome comparison between these two species as well as with other mammals suggested that the development of the giraffe’s long neck - when compared to the short-neck of the okapi - may be attributed to genetic changes in two sets of proteins, one controlling gene expression during body and limb development, and another controlling gene expression of growth factors (substances which stimulate cellular growth). Given that many of these protein-encoding genes are also known to regulate cardiovascular development, the unusual body shape of the giraffe is likely to have co-evolved with the adaptation of a circulatory system that could accommodate the animal’s unique physiology.
As well as providing information on the iconic body shape and physiology of the giraffe, this work could help future conservation studies.