The first de novo genome assembly and annotation of a green-blooded skink (<i>Prasinohaema aff. flavipes</i>) from a historic museum sample

The scincid genus Prasinohaema represents the only group of amniotes to possess green blood, resulting from the accumulation of the bile pigment biliverdin. Recent phylogenetic analyses have shown Prasinohaema to be polyphyletic with four independent origins for green blood. It is unknown why this trait has evolved in multiple instances and how Prasinohaema species are able to tolerate such high concentrations of a cytotoxic bile pigment. Here, we report the first de novo genome assembly and annotation for a green-blooded skink, Prasinohaema aff. flavipes, which was sequenced from an ethanol-preserved specimen that was collected more than 20 years ago. Our assembly comprises 907 contigs spanning 1.52 Gbp with contig N50 of 3.2 Mbp. The genome is highly complete, with a BUSCO completeness score of 97.76%. Phylogenetic analysis confirmed that our specimen is sister to P. flavipes with high support; however, the two specimens exhibit deep genetic divergence, perhaps supporting their distinctiveness. Searches for the gene encoding serum albumin, a common blood transport protein known to bind biliverdin, suggested it is absent from our P. aff. flavipes genome. Yet, we found a tandem duplication of the serum albumin paralog alpha-fetoprotein, which may play a role in biliverdin retention. BUSTED analysis of alpha-fetoprotein sequences across reptiles revealed that both copies of alpha-fetoprotein from our Prasinohaema genome are under diversifying selection. We envision this new genome assembly as a valuable source in examining the key genes, regulatory mechanisms, and functional mutations involved in the elevated biliverdin levels.