New insights on limb evolution from Auckland

30 November 2016
Image of Medical scientist, Dr Peter Johnston.
Medical scientist, Dr Peter Johnston.

An Auckland medical scientist has contributed to a better understanding of the role of muscles in limb evolution from fish to land animals, in research published recently.

The study involved three scientists from Howard University College of Medicine and academic Peter Johnston from the University of Auckland.

“A continuous pattern of evolution from fins to limbs has been difficult to demonstrate,” says anatomy expert Peter Johnston.

“Our work brings together information from the sometimes separate spheres of traditional comparative anatomy, palaeontology, and modern developmental genetics.

“It sets the scene for a better understanding of the role of the soft tissues in limb evolution which are seldom preserved in fossils,” he says.

Lobe-fin or fleshy fin fishes such as coelacanths and lungfish are the fish closest to limbed land animals – the tetrapods (four-footed animals).

“Coelacanths were common residents of the oceans 300 million years ago and were thought to be extinct until 1938, but small numbers of the genus Latimeria were found near southern Africa and recently in Indonesia,” says Peter.

“In this study we analysed muscles in coelacanth and lungfish fins and have demonstrated structures that evolve into the tetrapod limb pattern,” he says. “Previous opinion was that many features of tetrapod limbs arose de novo [spontaneously new].”

Although lungfish are closer to tetrapods, the fin anatomy of coelacanths is a better model for tetrapod limb evolution, and this had not been appreciated previously.

“Coelacanth material is difficult to access,” says Peter who made several trips to the southern German university city of Tübingen to study material held there.

See the published paper at this link.

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