What's eating the shark?
When most people think about sharks, they think about what sharks are eating, not what’s living on them.
But new research from CQUniversity has flipped that idea on its head, uncovering a hidden world of parasites living on some of Australia’s most well-known shark species such as bull sharks and reef sharks.
Published in Zootaxa, the study is the first to document a group of parasitic flatworms, known as hexabothriids, in requiem sharks in Australian waters, filling a major gap in marine science.
Led by CQUniversity researcher Dr David Vaughan, the research focuses on monogeneans, tiny parasites that attach to sharks and spend their most of their lives on a single host.
“These parasites are small, but they tell us a really big story about how ocean ecosystems work,” Dr Vaughan said.
“People are fascinated by what sharks eat, but we’re asking the opposite question, what’s eating the shark?”
The parasites live on the sharks’ gills, where they feed and reproduce. While they are invisible to most people, they play an important role in marine ecosystems and can help scientists better understand how species are connected.
The study delivered several key breakthroughs, including the first Australian records of these parasites in requiem sharks, new host records for known species, and the first DNA sequences of these known species to better understand how they are related.
For Dr Vaughan, the discovery is a reminder that even in one of the most studied environments in the world, there are still major gaps in knowledge.
“We’re still at the stage of simply working out what’s out there,” Dr Vaughan said.
“This research opens the door to understanding how widespread these parasites are and the role they play in ocean health.”
Because many parasites are highly specific to their hosts, they can act as indicators of environmental change, offering clues about shifting conditions beneath the surface.
“Parasites are often overlooked, but they’re a critical part of biodiversity,” Dr Vaughan said.
“They help regulate host populations and give us insight into how species interact and how ecosystems are changing.”
The research also has broader implications for conservation, with parasites offering unique insights into the health of shark populations and marine environments.
“Parasites can tell us things we can’t easily see otherwise,” Dr Vaughan said.
“But before we can use that information, we need to know what species exist and that’s exactly what this work is doing.”
The findings reinforce the importance of continued marine research, particularly in regions like the Great Barrier Reef.
Beneath the surface, there’s still a vast, largely invisible world waiting to be understood.
