Fish’s homing instinct a clue to coral reef diversity

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Scientists have discovered that a fish species on the Australian Great Barrier Reef can sniff its way back to the patch of reef where it hatched.

If the cardinal fish’s remarkable odour-assisted homing abilities are common, the researchers suggest it might help to explain the diversity of marine life on coral reefs. “Coral reefs are famous like tropical rainforests for their diversity of species,” said Jelle Atema at the Marine Biological Laboratory at Woods Hole in Massachusetts.

But that amazing biodiversity looks puzzling when you consider that many marine species reproduce by releasing their eggs into the water to be carried at the whim of the current, he said. That would mean species are dispersed widely, preventing the genetic isolation in local areas needed for new species to evolve.

Dr Atema and his colleagues took DNA samples from cardinal fish on different sections of the Great Barrier Reef. They found that far from a random mixing of genes, the fish on different patches of reef separated by just two miles were genetically isolated from each other, even though the fry are carried up to 30 miles.

To test whether the fry can smell their way home, the team tested thousands in tanks of flowing water from different sources. The fish indicate which flow they prefer by moving from one to the other and they consistently chose water from their patch of reef. This may be due to a difference in odours created by organisms living in the reefs or the fry may be able to follow the smell of pheromones from their own population, said the researchers.

Source: Guardian (UK)