The long-time adaptation of coelacanths to moderate deep water: reviewing the evidences

Abstract

The evolutionary history of coelacanths is long and complex with indications of adaptations to different aquatic environments. Fossil coelacanths are registered in shallow brackish, fresh or marine waters, while extant coelacanths inhabit moderate deep marine environments. Here we review some evidences of this long-time adaptation to moderate deep waters, focusing mainly on the hypothesis of bimodal respiration (gas exchange through gills and lungs) in most fossil coelacanths and on the aquatic gas exchange and the presence of a non-functional lung in the extant coelacanth Latimeria chalumnae. Another morphological evidence is the high rate of lipid accumulation in the whole body of L. chalumnae.