We know that life began in the water, but now a remarkable group of fish have given scientists new clues about how vertebrates made the leap onto land.
There are more than 900 species of blennies; they are an incredibly diverse group of fish, occupying a wide range of habitats. Some species are fully aquatic, while others live in the intertidal zone – the region of the seashore that’s underwater at high tide and out of water at low tide – where they deal with fluctuations in temperature and salinity.
Some blennies can even remain out of water for hours at a time, as long as they stay moist. This diversity makes them really useful animals to study when investigating how animals moved from water to land.
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Researchers from the University of New South Wales and the University of Minnesota have hypothesised that a flexible diet and behaviour is key to making the transition.
“Fossils can give us important insights into how that transition might have unfolded, and the types of evolutionary adaptations it required or produced,” said lead author Dr Terry Ord.
“But having a contemporary example of fish making similar ecological transitions can also help us understand the general challenges that are faced by fish out of the water.”
The scientists think that once fish make the leap to living on land, restrictions in the types of food available means that their diet and behaviour become specialised. For example, land-dwelling blennies have become adapted to scraping algae off rocks with their teeth.
“Terrestrial blennies are really agile out of water, and I suspect they’ve adapted their body shape to allow them to hop about the rocks so freely. Which in turn implies they might not be able to go back to the water,” said Dr Ord.
“It would also be exciting to know how their sensory systems might have adapted out of the water as well, given vision and smell would probably work quite differently in these environments.”
Reader Q&A: Which part of the human body evolved most recently?
Asked by: Luca Blackwell
Evolution doesn’t just hand out useful traits such as opposable thumbs or colour vision like lottery prizes. Natural selection is constantly tinkering, and no part of our body is more ‘recent’ than another. But some are changing faster.
One of the fastest movers is the human jaw, which has been steadily shrinking over the last 10,000 years, as the invention of agriculture and cooking gave us softer foods that need less chewing.