Population Genetics of Gyrodactylus
PhD project, Stanley King
Nearly every organism on earth is infected with at least one species of parasite and often many more. Although sometimes harmless, parasites have the ability to shape ecosystems, facilitate trophic interactions and, sometimes, annihilate populations. Parasitism has proven to be a very successful life strategy and has evolved multiple times independently. This has created a wonderful diversity in the morphology and ‘life-styles’ of the parasites we see today. They are an important part of every ecosystem but seem to particularly abound in aquatic environments, perhaps because water can aid in their dispersal. As a result, fishes typically have a rich parasite fauna. One group of parasites that has been particularly successful in infecting fishes throughout all aquatic environments are monogenean flatworms belonging to the genus Gyrodactylus and several related genera.
Biology and Life History
Gyrodactylus and related genera (henceforth, for convenience collectively referred to as Gyrodactylus) comprise a diverse group of ectoparasitic flatworms that primarily infect teleost fishes. There are an estimated 20,000 members in the genus and their distribution is global. Species of Gyrodactylus have a reproductive mode thought to be unique in the animal kingdom: they can reproduce both sexually and asexually, but all individuals are born as females and develop male reproductive organs as they mature. Further, adults contain a fully grown daughter in utero, which in turn contain a developing embryo, packaged one inside the other like Russian dolls. This ‘hyper-viviparity’ allows for explosive population growth, which can lead to parasite-induced mortality. Perhaps one of the most compelling examples of this comes from Atlantic salmon, Salmo salar. Wild stocks of Norwegian Atlantic salmon were decimated by inadvertently introduced Gyrodactylus salaris, which effectively destroyed populations in over 40 rivers causing over $670 million US in damages.
Current Research
Our primary research goal is to characterize the genetic structure of Gyrodactylus populations on different hierarchical levels using various genetic markers, including microsatellites developed with next generation sequencing. This research has various implications. Most generally, we hope to shed some light on intraspecific biodiversity and population structure in an understudied but ecologically important invertebrate group whose species diversity is comparable to that of their fish hosts. Further, the host specificity and lack of free-living stages suggest that the population structure of Gyrodactylus should resemble that of their fish hosts; however, the short generation times, and potentially small effective population sizes of the parasite, suggest further that the magnitude of genetic differentiation exhibited by Gyrodactylus is likely ‘magnified’ relative to their fish hosts. This opens up the possibility that Gyrodactylus may serve as sensitive biological tags, which may reveal important yet otherwise cryptic information regarding the ecology and evolutionary history of their fish hosts. Finally, we may be able to evaluate the potential threat posed by shipping fishes (e.g. aquaculture broodstock) and their parasites to foreign localities.
Gyrodactylus publications
Schelkle, B., Paladini, G., Shinn, A., King, S., Johnson, M., Van Oosterhout, C., Mohammed, R. and Cable, J. 2011. Ieredactylus rivuli gen. et sp. nov. (Monogenea, Gyrodactylidae) from Rivulus hartii (Cyprinodontiformes, Rivulidae) in Trinidad. Acta Parasitologica 56(4): 360-370.
You, P., Li, X., King, S. and Cone, D.K. 2011. Gyrodactylus rivularae n. sp. (Monogenoidea: Gyrodactylidae) from Abbottina rivularis (Basilewsky, 1855) (Pisces: Cyprinidae) in Central China. Comparative Parasitology 78 (2): 257-260.
You, P., Guo, Z., King, S. D. and Cone, D. K. 2010. A new gyrodactylid species from Cobitis granoei (Rendahl) (Cobitidae) in Central China. Journal of Parasitology 96: 897-899.
King, S. D. and Cone, D. K. 2009. Morphological and molecular taxonomy of Fundulotrema porterensis n. sp. and Gyrodactylus stephanus (Monogenea: Gyrodactylidae) from Fundulus heteroclitus (Actinopterygii: Cyprinodontiformes) in Nova Scotia, Canada. Journal of Parasitology 95: 846-849.
King, S. D., Forest, J. J. H. and Cone, D. K. 2009. Description of Gyrodactylus notatae n. sp. (Monogenea: Gyrodactylidae) from Menidia menidia (Actinopterygii: Atherinidae) in Nova Scotia, Canada. Systematic Parasitology 74: 23-27.
Gilmore, S., Cone, D. K., King, S. D., Jones S. and Abbott, C. Molecular phylogeny of Gyrodactylus (Monogenea) parasitizing fishes in freshwater, estuarine, and marine habitats throughout temperate Canada. In Press