Systematics and ecology of Australian and South African gnathiid isopods, with observations on blood-inhabiting Protozoa found in some of their host fishes

• Main Author: Ferreira, Maryke Louise
• Published: 2011
• Subjects: Isopoda ecology; Parasite ecology; Protozoan diseases
• Online Access: http://hdl.handle.net/10210/3766

M.Sc. === In this research project, a variety of sites and ecosystems were studied. These ranged from tropical coral reefs (north-eastern Coast of Australia), to warm temperate intertidal pools (South Coast of South Africa, SA) and sub-tropical estuaries (East Coast of SA). The overall aims of the thesis were to examine the haematophagous gnathiid ectoparasites and blood protozoans of some host teleosts found in these systems, and to some extent to investigate the role gnathiids might play as vectors of the protozoans. Gnathiid research in Australia on the Great Barrier Reef (GBR) focuses mainly on gnathiid ecology and not taxonomy. This is not the case in SA, where gnathiid taxonomy is researched more regularly and gnathiid ecology has received little attention. In this thesis, two new gnathiid species, Gnathia aureamaculosa and Gnathia sp. B, were described from a number of teleost fishes of the GBR and several morphological features, including live colouration patterns, were highlighted as useful in future gnathiid identification and discrimination. The feeding ecology of Gnathia africana from SA was also examined and this feeding study was based on similar work done on coral reef gnathiids in Australia. Gnathiids of the GBR are mainly nocturnal due to cleaner fish predation during the day, whereas G. africana was found to have a preference for dawn/early morning/midday feeding on an intertidal teleost, Clinus superciliosus. Gnathia africana‟s behaviour/feeding patterns, especially of its different juvenile stages, are therefore determined by time of day, and likely by locality and predation by other organisms, such as fishes, though probably not by cleaner fish. Gnathiid feeding behaviours/patterns are thus, it seems, determined by environmental and biological factors, and these vary according to the type of ecosystem studied. Several gnathiids and fish blood protozoan species are known from the South Coast of SA, but the East Coast has remained largely unexplored. Sampling along the East Coast yielded the first records of haemogregarines from the blood of fishes in this region, in particular new hosts and locality records probably for both probable Haemogregarina bigemina and a Haemogregarina quadrigemina – like haemogregarine. However, both haemogregarines displayed unusual features compared with the original species descriptions, in size, development patterns, or effect on host cells. Limited data suggested that juveniles of Gnathia pilosus were possible haematophagous vectors of these haemogregarines, but further studies are required to confirm this.