Have you ever wondered who would choose to study parasites and what kinds of research they may do? Research in Parasitology at the SA Museum is described here.
Parasitologists study parasites. It is said that more than 50% of all animal species are parasitic at some stage in their life history. Parasitism, therefore, is a, if not the, dominant ecological interaction in biology. This means that there are many parasitic relationships to study. For every parasite species we know something about, countless others remain unknown. Some have complex life-cycles and must infect several different animal and/or plant species before the parasite can mature and reproduce. An example is a human tapeworm that could be acquired by eating infected meat such as pork or beef. Other parasites have direct life-cycles and infect only one animal species on which it matures and reproduced. An example is a head louse.
Parasites provide parasitologists with exciting, interesting challenges to address and solve, for example:
- What is the life-cycle?
- What impact does a parasite species have on its host(s)?
- If harmful, how can parasites be controlled?
- How is an organism adapted for life as a parasite?
- How do parasites evolve?
Some parasites are pests of economically important plant and animal species. Without an established collection of parasite species from Australian and international animal and plant species as a frame of reference, how can parasitologists and other scientists be certain of the correct identity of a parasite species, whether it is a pest or not? An extensive, continually growing and properly managed collection of biological material for access by interested persons to compare, help identify and determine whether a species is new or known is essential to the work of biologists. Therefore, the Australian Helminthological Collection (AHC) at the South Australian Museum is critically important to parasitologists.
Dr Ian Whittington, Senior Research Scientist at the South Australian Museum, researches marine parasites. Ian leads several research programs in Parasitology at the museum and at the University of Adelaide. Their focus is principally on marine parasites that infect fishes. Current projects are investigating:
- the systematics, taxonomy and identity using traditional morphology and advanced molecular genetic techniques of Monogenea (flatworms) and other flatworm parasites from fish globally;
- the biology of the Capsalidae, a family of ectoparasitic monogeneans that infect skin, gills, eyes, pharyngeal tooth pads, fins, lips, nares and branchiostegal membranes of bony and cartilaginous fish, some of which cause disease;
- the impacts of pathogenic marine parasites on farmed fish and methods to control them;
- the evolution, evolutionary history and radiation of Monogenea;
- studies of parasite-host interactions using local fish species near Adelaide as ‘models’ to study parasite biology and life-cycles;
- parasites of the giant Australian cuttlefish.
Some of these projects involve students at The University of Adelaide, several research scientists locally and research collaborations with other specialists within Australia and internationally.
Ian Whittington has written more than 130 peer-reviewed publications on parasites of fishes including chapters in international text books about marine parasitology and fish diseases.
Knowledge of Flatworm Parasites of Kingfish
Seriola species or yellowtail, amberjack and Samson fish are recreationally and commercially important fishes that occur throughout the world in warm waters. They are farmed in Japan, South and Central America (Chile, Ecuador, México) and Australasia (Australia, New Zealand). In all these regions, farmed stock is parasitised by skin flukes (Benedenia seriolae) and gill flukes (Zeuxapta seriolae and/or Heteraxine heterocerca). These parasites have been studied to better understand their biology so that we can develop methods to try to control their populations on farmed fish. In South Australia, Benedenia seriolae and Zeuxapta seriolae infect wild Samson fish (Seriola dumerili) and wild yellowtail kingfish (Seriola lalandi) but may also affect growth and health of yellowtail farmed in sea cages in Spencer Gulf. A series of PhD and Honours students have investigated different aspects of these parasites such as their egg biology, development and growth rates at different temperatures and salinities, the efficacy of antiparasitic chemicals and ways that can improve farm husbandry to reduce the burden of B. seriolae and Z. seriolae on farmed kingfish health. There is a small display about these parasites in the South Australian Museum’s Biodiversity Gallery.
Leslie Chisholm is the Manager of the Parasitology Collection at the South Australian Museum and is an expert on marine parasitic flatworms that infect sharks and stingrays (elasmobranchs). She has described 35 new species of flatworm parasites from sharks and rays and has written more than 75 peer reviewed papers on parasites of fish. The current research projects that she is involved in include:
- A survey of sharks and rays of Borneo and their metazoan parasites. This is a collaborative National Science Foundation (USA) project involving parasite and shark and ray taxonomists from 8 different institutions in the USA, Australia, Malaysia, and Indonesia. The project as been running since 2002 and the aim is to investigate elasmobranchs and their parasites off Malaysian (2002–2004) and Indonesian (2005–2008) Borneo. Until these studies, there were no published records of monogenean parasites from elasmobranchs in this region.
- Investigations of monogenean parasites on captive sharks and rays kept at Two Oceans Aquarium, Cape Town, South Africa. Collaborator David Vaughan of Two Oceans Aquarium and Leslie continue to study monocotylid flatworm parasites from sharks and rays in captivity. Before wild caught fish are added to the main display tanks at the aquarium, they are quarantined and carefully screened for parasites. We find and describe many new parasite species this way.
- Study of Capsalinae parasites, a subfamily of ectoparasites that live on the gills, nares and skin of fast moving prize sport-fish species such as marlin and tuna.
Emeritus Professor Lesley Warner, an Honorary Research Associate, has a long history of involvement with the Australian Helminthological Collection.
Adhesive Secretions in the Platyhelminthes
Some monogeneans secrete bioadhesives to attach temporarily to the surfaces of their fish hosts. All monogeneans have a principal posterior attachment organ called the haptor that used proteinaceous hooks or clamps to secure them mechanically to epithelium on the body surface or gills. Some monogeneans are highly mobile and alternately attach the haptor and the head region to allow locomotion across fish tissue. These secretions function as underwater glue and are secreted in tiny quantities from special frontal apertures. These bioadhesives are remarkable because they attach parasites to surfaces that one would consider are difficult to adhere to (i.e. wet, mucus-covered, living tissues). As the fish swims through water or as it respires, the parasites are subjected to significant volumes of fast-flowing water that could easily dislodge them. The parasites can switch their bioadhesion on and off instantly as the short video here demonstrates.