A recent discovery has uncovered two species of damselfish can recognise their relatives by smell – and it’s all happening before any of them have even hatched.

Dr. Jen Atherton and Prof. Mark McCormick, both at the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University, found that young damselfish – the cinnamon clownfish and the spiny chromis – imprint on the odours of their closely related kin while they are still only embryos.

“These fish can detect and recognise cues from their siblings quite early on in their development,” Dr. Atherton said.

“They start to panic when they pick up the scent of an injured relative.”

A sophisticated sense of smell

Dr. Atherton added, “The most amazing thing is, not only can the baby damselfish identify cues from other sibling fish with the same parents – they can differentiate between the fish of different parents, and also different species altogether.”

“These fish are only about eight days old and haven’t even hatched yet!”

Staying alive

This capability may be an important tool for the fish to help them avoid predators, with the early recognition of odours helping to reduce their chances of being eaten.

“These fish can increase their chance of survival not only through cooperating with their kin, who will help alert them to danger, but they may also use these scents to select ‘safe’ habitats,” Dr. Atherton said.


Heartbeat and smell linked

The study was a lab-based experiment, measuring fish embryo heart rates under a microscope – the embryos are transparent, so each individual heartbeat can be seen and counted.

“Looking at the change in heart rate from before and after the introduction of certain odours allowed us to quantify the fish embryo’s reaction to it,” Dr. Atherton said.

She found different responses between kin, non-kin of the same species, and other species.

This discovery comes after scientists from the Coral CoE found cardinalfish use magnetic forces to find their way home.

Damselfish are a diverse group of fish commonly found on coral reefs around the world. They perform many important functions that can promote the health of reef habitats.

This article was first published by James Cook University

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