First Land Animals Saw In Colour

Visual pigments in a living fossil, the Australian lungfish Neoceratodus forsteri. 2007. Helena J Bailes, et al. Evolutionary Biology 7: 200.

According to a new study it's likely that creatures venturing out of the depths viewed their new environment in full colour.

A team analysed retinas from Australian lungfish (Neoceratodus forsteri), thought to be the closest living relative to the first terrestrial vertebrates. The DNA of five visual pigment genes in the retinas of lungfish reveals that these have more in common with four-legged vertebrates (tetrapods) than with fish retinas.

Lungfish were previously thought to have poor eyesight due to their small eyes, low spatial resolving power, sluggish behaviour in captivity and ability to detect prey using electroreception. N.forsteri inhabits a brightly lit, shallow freshwater habitat similar to the environment from which terrestrial evolution probably occurred. This prompted the team to investigate the complement of visual proteins expressed in N. forsteri, to trace photoreception's evolution in ancestral tetrapods.

"The genus Neoceratodus, of which N. forsteri is the sole survivor, is found in the fossil record from the Lower Cretaceous period 135 million years ago and therefore N. forsteri lays claim to being the oldest surviving vertebrate genus," says Bailes. "The visual system of N. forsteri may represent an evolutionary design most closely reflecting that present just prior to the emergence of land vertebrates in the Devonian period."