15 May 2014
Video footage filmed using a microscope is bringing curious creatures to life as part of the South Australian Museum’s specialist research into parasites.
Associate Professor Ian Whittington is part of an internationally renowned team at the Museum that studies parasites and helps industries deal with their impact. Associate Professor Whittington has used monogenean parasites, which principally infect fishes, as a model research system and has published around 150 papers on different elements of their infection, invasion and reproductive biology, ecology, biodiversity and control.
In a fascinating video recorded and edited by Associate Professor Ian Whittington, he uses freeze-frame to highlight the pharynx, which is the feeding organ of the parasite.
The technology offers a new insight into the parasites’ behaviour. “A video like this is a great way to show people who probably rarely think about parasites just what incredible creatures they are. And there are countless species of monogenean fish parasites on freshwater and marine fish everywhere!”
Close-ups show egg formation in a muscular chamber undergoing constant contraction and relaxation. This mixes the components necessary to form a tiny (approximately a tenth of a millimetre wide), shelled egg. Then the resulting tetrahedral egg is laid by muscular contraction of the body.
Parasites are important to study and understand. Every fish in the world will be infected with a parasite at some stage and the impact for aquaculture and aquarium industries can be severe. Parasites can also play a role in the natural regulation of fish population sizes. “Species in the genus Neobenedenia are a major threat to fish health in aquaculture and aquaria. Their populations can grow rapidly due to the direct lifecycle of the parasite,” said Associate Professor Whittington.
While these animals feed from the host and can cause serious damage, if a human accidentally ate the monogenean parasite, there would be no physical harm. They would simply digest the parasite because these species only infect and feed on fish.
“Parasites are especially well-evolved to find their host, reproduce and feed. The fish parasite in the video may lay an egg every two minutes!” The video also shows a starved parasite attempting to feed on the glass dish in the same way the worm would feed on fish epidermis.”
Muscular contractions occur which is how the parasite’s pharynx rasps and dislodges skin cells in combination with secreted enzymes to begin digestion. Throughout this entire process, the video shows yet another egg being made.
Scientists at the South Australian Museum regularly record digital video of the animals they research. “We’ve used digital video for several years to record the fauna we study. I’m a Parasitologist and it’s not necessarily easy to obtain live parasites for research. Once removed from their host, the parasites have a limited lifespan because they rely on their host for food. Separate a parasite from its food source and it may starve to death rapidly,” said Associate Professor Whittington.
A different function for the parasite’s feeding organ ends the video. Flatworms are primitive invertebrates and have a single opening to the intestine. They have no anus, so food taken in by the mouth must also be excreted via the mouth. “They use their muscular pharynx to swallow seawater to flush out the intestine. You can watch the branched gut stand out like a road map as it inflates with seawater. Then muscles around the gut branches suddenly contract to flush out the intestinal contents through the mouth.”
Understanding these parasites can help scientists work out the intricacies of their lifecycle, how they find and identify their specific host, how they breed and their consequential impact on fish and industry.
Our parasite experts, including Associate Professor Whittington, are also regularly consulted for advice on issues such as the specific identities of parasites, details of their lifecycles and what measures can be implemented to help control them. General Practitioners may request information on parasite infections reported by infected patients when returning from an overseas trip. Veterinarians often send samples of parasites passed in faeces or vomited by family pets.
Federal and State government agencies have requested data on parasites recorded naturally from horses to compile reports to monitor their health. The Museum has the largest collection of parasitic worms in Australia used regularly by scientists throughout the world when they study parasites of wildlife.
Visitors to the South Australian Museum can learn more about parasites in our Biodiversity Gallery on Level 2.
Listen to the interview with Peter Goers on 891 ABC Adelaide.