Molecular systematics and morphological variation in the Mesopotamian spiny eel Mastacembelus mastacembelus (Teleostei: Mastacembelidae)

Abstract

The Mesopotamian spiny eel, Mastacembelus mastacembelus, an endemic freshwater fish restricted to the Euphrates and Tigris river drainages of Mesopotamian, and its related taxa in Afrotropica and South Asia present suitable elements for studies of the evolutionary history of mastacembelids across these heterogeneous areas. To understand and clarify the geographic variation of the Mesopotamian spiny eel from the Persian Gulf basin, we investigated the molecular and morphological characteristics of individuals collected from its whole distribution range in the Tigris (Karkheh, Karoon and Zab), Zohreh and Persis (Mond and Helleh) main river drainages in Iran. The morphological analysis revealed a separation of the studied populations; however, the genetic distances were relatively small and the molecular tree did not present a distinct branching pattern for the main river drainages based on the COI mitochondrial marker. Six haplotypes were identified: Helleh, Mond, Karkheh, Karoon, Zab and Zohreh tributaries each showed a separate haplotype. The COI marker indicates that the Mesopotamian eel has greater affinity with the African species than with the Southeast Asian species. Estimation of divergence times indicates the Mesopotamian spiny eel apparently diverged about 1 million years ago (Mya) (95% highest posterior density [HPD]: from 390,000 years ago to 2.1 Mya) in different river drainages of the Persian Gulf basin.