Scientists may have found what helped a fish transition to live on land

17 Jun 2020

A group of Pacific leaping blennies out of the water on the foreshores of the island Guam. Image: Terry Ord/UNSW Sydney

Researchers looking at blenny fish have found that being a ‘jack of all trades’ when it comes to diet may have helped some species transition onto land.

Blenny fish have been described as a “unique opportunity to study fish evolution in action”, in new research published to Functional Ecology. Previous discoveries have shown that while some species of blennies never emerge from water, others have made the transition to staying on land full-time in what could be evolution before our eyes.

Now, in this latest study, researchers from the University of New South Wales have suggested that the diverse diet and flexible behaviour of these blennies may have helped them make the transition to land, but have also now made them incredibly specialised.

“In this study, we found that having a flexible diet has likely allowed blennies to make a successful leap onto land,” said the study’s lead, associate professor Terry Ord. “But once out of the water, these remarkable land fish have faced restrictions on the type of food available to them.

“These restrictions have triggered major evolutionary changes in their morphology, specifically dramatic changes in their teeth, as they have been forced to become specialist scrappers of the rocks to forage on algae and detritus.”

While there is ample evidence to show that a transition from one environment to another is responsible for a species’ evolution, little is known about the mechanisms behind what drives those transitions.

‘A jack of all trades’

In order to better understand these mechanisms, the researchers applied a set of complex evolutionary statistics models to their data on blenny fish. This revealed the sequences of events that likely allowed aquatic marine fish to ultimately evolve into fish that could leave water and colonise land, as well as what happened when they got there.

“Our findings suggest that being a jack of all trade – for example, being flexible in the types of foods you can eat and being flexible in leaving water for very brief periods of time – can open the door to making what would seem to be a really dramatic change in habitat,” Ord said.

“The flipside of our study suggests that some species that are already uniquely specialised to their existing environment are probably less able to make further transitions in habitat, or might not cope well if abrupt changes occur to their environment. For example, as a consequence of the current climate crisis.”

Ord said that further research is needed to confirm the findings, as this most recent study was limited to observation and does not prove causation.

“It’s possible that diet or behavioural flexibility are not responsible, and that some other currently unknown factor is,” he said. “What this experimental study might be is hard to imagine at this stage, but we’re working on it.”

Colm Gorey was a senior journalist with Silicon Republic