Metamorphosis: a life-changing event

WITH EVOLUTIONARY BIOLOGIST JV CHAMARY

- JV CHAMARY

WE FIRST ENCOUNTER metamorphosis through children’s books such as The Very Hungry Caterpillar, in which (spoiler alert!) the insatiable insect ends up turning into a beautiful butterfly. This process – a spectacular transformation in an animal’s form or ‘morphology’ – produces dramatic differences between larvae and adults.

Which animals metamorphose?

Metamorphosis is characteristic of insects and amphibians, but it’s also found in specific groups. Flatfish are a clear case among vertebrates: a fish starts with two sides to its body – bilateral symmetry – but the right eye migrates to the left side and its dorsal fin becomes shorter as it transitions from a free-swimming larva to a ‘benthic’ or bottom-dwelling adult on the seafloor or river bed.

Similar phenomena occur in invertebrates. For example, adult echinoderms have a benthic lifestyle and radial symmetry – as seen in five-armed starfish – but their larvae are bilaterally symmetrical, free-swimming plankton.

What happens in insects?