Massey University, PhD

Short circuit co-evolution by the perfect parasite: Antifreeze glycoproteins of fish leeches (Hirudinea, Piscicolidae) in Antarctica

Antifreeze glycoproteins (AFGPs) play an important role in biochemical adaptation to supercooled waters, and subsequently, the survival of notothenioid fish in Antarctica. These fishes have a well-developed parasitic epifauna, which in turn are also exposed to freezing conditions. In order to retain their association with Antarctic fishes as the environment progressively cooled during the Miocene, leeches and other fish-associated ectoparasites had to either adapt their own genome to confer protection from freezing or adapt a short circuit strategy by acquiring the necessary life-saving chemical compounds from their host.

This study aims to advance our knowledge of trophic links and ecosystem interactions in an Antarctic fish-ectoparasite system, and determine evolutionary strategies employed by fish leeches for their survival in supercooled Antarctic waters.

In pilot studies, we have found that the Antarctic leeches (Annelida, Hirudinea, Rhynchobdellida) feed on a variety of notothenioid fish species contain antifreeze compounds. This PhD project aims to characterise these AFGPs to determine their physical and biochemical properties and to trace their origins (leech or host). This will determine if these leeches have developed a novel means of short-cutting evolution by co-opting mechanisms for survival in supercooled waters from their hosts, either by biochemical exploitation or horizontal gene transfer. If so, then this will be the first example of an instantly effective adaptive advantage provided by another species in a quasi short circuit co-evolution.