Mudskippers in the Mekong Delta might tell us something about vertebrate transition to land?

Abstract

Rise of vertebrates from water to land, which seems to be occurred in the mid to late Devonian Period (about 390 to 360 million years ago), shows one of the most crucial events throughout the existence of life [1]. There are many longstanding debates about emergence of vertebrates in the Paleozoic from marine environment or freshwater environments [2-6]. Through our four-year survey in the field in the place called Mekong Delta which is situated in Vietnam, we explored mudskippers a special species, Periophthalmodon septemradiatus, which inhabits the littoral zones in brackish waters near the coast of fully freshwater areas 150 km from the river mouth along the Mekong River [7]. Mudskippers which are amphibious gobies which usually inhabits intertidal mudflats from estuaries, subtropical coasts and tropical coasts and shows behavioral, physiological and morphological adaptations of life on land [8]. The most terrestrial fishes named Periophthalmodon septemradiatus are living today. During the period of our field survey, we have not seen any P. septemradiatus ventures into water. The substantial portal of gut content of this fish is constituted by ants, further supporting the high terrestriality of the fish