A Comparative Analysis of Complete Mitochondrial Genomes of Two Tyulka Clupeonella Kessler, 1877 (Actinopterygii: Clupeidae) Species Allowed to Clarify Their Evolutionary History in the Ponto-Сaspian Region

This paper presents a comparative analysis of mitochondrial genomes of two species of tyulka (also known as kilka or sprat): anchovy sprat Clupeonella engrauliformis and the Black and Caspian sea sprat C. cultriventris from the Caspian Sea. The mitogenome of tyulka has a length of about 16.6 thousand bp and is characterized by a gene order conservative for herring fishes. The difference between the mitochondrial genomes of anchovy and Black and Caspian Sea sprats concerns 449 bp (2.7%), including two insertions in the control region, unknown in other representatives of the genus Clupeonella. The differentiation of tyulkas is probably related to the transgression and degradation of the Pontic Lake-Sea: it began in the Miocene, continued in the Pliocene, and was completed by the Pleistocene. The modern differences of tyulkas may be connected with different adaptations of their ancestors to specific conditions in different water bodies—remnants of the Pontic Mega-lake.