Looking at modern-day walking fish could help researchers gain insight into how our aquatic ancestors evolved to walk on land.
Over 400 million years ago a group of fish started moving onto land and eventually evolved into tetrapods, but researchers are not sure how these creatures used their bodies in their environment or what processes were involved, McGill University reported.
To learn more about these ancient creatures researchers looked at a modern fish, called Polypterus. The fish is native to Africa and can breathe air and "walk" on land; it looks very similar to the ancient fish that evolved into tetrapods. The researchers raised juvenile Polypterus on land for about a year to see how these "terrestrial" fish moved differently.
"Stressful environmental conditions can often reveal otherwise cryptic anatomical and behavioural variation, a form of developmental plasticity," said Emily Standen, a former McGill post-doctoral student who led the project, now at the University of Ottawa. "We wanted to use this mechanism to see what new anatomies and [behaviors] we could trigger in these fish and see if they match what we know of the fossil record."
The land-raised fish showed anatomical and behavioral changes such as walking wore effectively by placing their fins closer to their bodies and lifting their heads higher to keep their fins from slipping.
"Anatomically, their pectoral skeleton changed to became more elongate with stronger attachments across their chest, possibly to increase support during walking, and a reduced contact with the skull to potentially allow greater head [and] neck motion," said Trina Du, a McGill Ph.D. student and study collaborator.
The terrestrialized Polypterus experiment could help researchers gain insight into how ancient fish may have used their fins to navigate the terrestrial environment.
"Because many of the anatomical changes mirror the fossil record, we can hypothesize that the [behavioral] changes we see also reflect what may have occurred when fossil fish first walked with their fins on land," said Hans Larsson, Canada Research Chair in Macroevolution at McGill and an Associate Professor at the Redpath Museum.
