Researchers at Tokyo Institute of Technology have undertaken what is believed to be the very first CT scan of eggs inside a coelacanth fish.

“I was surprised to see that all the eggs were the same size,” said Dr Norihiro Okada, a bioscience professor at the university and a member of the research team. “I hope to do research into why this is.”

Each coelacanth fish was roughly 170 cm (67 in) long and weighed about 70 kg (154 lbs). After being captured off the coast of Tanzania, both fishes were frozen and send to Japan where the CT scan showed how each fish contained roughly 40 eggs; each egg being about 7 cm (almost 2 ¾ in) in diameter.

The eggs of a coelacanth are never released into the water because the offspring hatch while still inside their mother. The young fish sometimes reach a length of 30 cm (12 in) before leaving their mother’s body.

Coelacanths were long believed to have gone extinct around the same time as the dinosaurs, until scientists realized that these fishes actually turn up in the nets of African and Asian fishermen now and then. The first confirmed finding is from 1938 when a specimen was captured in the Indian Ocean.

Coelacanths are of special interest to evolutionary biologists since they are thought to represent an early step in the evolution of fish to amphibians. You can read more about this in our coelacanth article.