Sturgeons: An Evolutionary Insight to The α-globin Protein Speciation and Diversification

Sturgeons are living fossils and among the oldest surviving vertebrate species, and Caspian Sea is habitat of the vast majority of sturgeon species. It is tempting to assume that speciation of sturgeons occurred in response to the severe environmental changes during the formation of Caspian Sea from the ancient Paratethys Sea. Hemoglobin (Hb) reflects the evolutionary history of fishes. Changes in the Hb sequences will affect the protein structure and consequently the vital function of oxygen delivery. As complete sequence data for any sturgeon hemoglobin gene or protein was hitherto not available, we determined the complete gene and protein sequences of an α-globin chain (as one of the constituents of Hb complex) from six Caspian Sea sturgeons of different species and compared these sequences mutually and with all available fish α-globin sequences. The phylogenetic analyses based on alpha globin sequences can highlight the essentiality of proper changes in globin chains in the speciation process. Estimating the divergence time of α-globin genes for different fish families discloses important facts about the rate of evolution and decodes. The results support the hypothesis of simultaneity between the time of morphological speciation of fish families and their α-globin divergence. The correlation and concurrency between morphological and molecular changes can be interpreted as a sign of struggling to acquire more fitness to changing environment.