Background:

Polypterus condense unique characteristics that astonished and confused naturalists since 1802 when Geoffroy St. Hilaire first described and named this fish. Polypterus was seen in that epoch as primitive amphibians or a link between fishes and amphibians. Polypteriformes have the ability to regenerate its pectoral fins with the accuracy only seen in urodel amphibians and have the capacity to breathe air using paired lungs.

Goals:

We aimed to evaluate how forced land-living condition (i.e., terrestrialization) could affect pectoral girdle bones shape and pectoral fin regeneration in Polypterus senegalus.

Methods:

Polypterus were reared in semi-terrestrial conditions for nine months and iterative amputations of pectoral fins were performed every two months. The bone elements of the shoulder girdle and pectoral fins were measured and compared between terrestrialized organisms and controls.

Results:

Terrestrialization produces notable morphological alterations, including general reduced body growth and big eyes, serial amputations under this condition decreases the number of radial bones of pectoral fins.

Conclusions:

We propose allometry and heterochrony as reliable concepts to explain the modifications generated by terrestrialization. Also, we suggest that anatomical alterations in early tetrapod ancestors were an unavoidable consequence of the influence of environment on general metabolic processes associated with growth.