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Neon gobies decide when to hatch their embryos

Leaving home to explore the world can be a difficult decision. Tiny coral reef fish called neon gobies help their offspring by pushing them out the door when the time is right, according to a new study from UT Austin. This research provides the first documented case of a coral reef fish regulating when its offspring hatch. 

Coral reef fish are incredibly vulnerable when hatching, which means that choosing the right time to hatch is a crucial decision. Male neon gobies hatch their embryos by removing eggs from the nest with their mouth. They transport the eggs to the opening of the sponge where the fish live – and then spit them out of the sponge entrance.

“We often think that eggs are like tiny kitchen timers: they develop for a set period of time, then – ding! – they hatch. But, in many species, embryos have to actively decide when to hatch,” explained study co-author John Majoris.

The researchers found that when neon goby embryos develop without parents, they hatch up to 50 percent earlier than embryos cared for by their parents.

All of the male parents in the study hatched their offspring at sunrise on the seventh day of development, suggesting that all of the goby parents know the best time for their embryos to hatch.

“Goby embryos are ready and waiting,” said Majoris. “When parents are around, they wait patiently for their dads to make the call that it’s time to hatch.”

Offspring hatched by their parents are more developed and likely benefit from their larger size when catching food, escaping predators and navigating the ocean. This is the first time scientists have discovered a coral reef fish that tells its offspring when to hatch, which could be more common than we think. 

Cryptobenthic coral reef fishes – a group of tiny bottom dwellers – often lay their eggs deep in reef crevices, where it is difficult for embryos to judge hatching conditions. In this case, parents can help out by hatching their eggs at just the right time. 

“This is a remarkably complex parenting behavior for a tiny fish,” Majoris said. “It goes to show that we still have so much to learn about life in our oceans.”

The surprising complexities of fish parenting behavior provides evidence that  fish parents can make decisions based on the local conditions that influence the survival, resilience and success of their offspring.

The paper is published in the journal Proceedings of the Royal Society B. The research was supported by the National Science Foundation, and a Dana Wright Summer Research Fellowship.

By Katherine Bucko, Staff Writer

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