LE3 .A278 2015

2015

Smith, Todd

Acadia University

Bachelor of Science

Honours

Biology

Biology

Two sympatric species of Hepatozoon, H. clamatae and H. catesbianae, have a high prevalence in frogs of Nova Scotia. Although the vertebrate hosts appear not to be adversely affected by these parasites, high parasitaemia values (i.e., where more than 5% of erythrocytes are infected) that occur naturally in some frogs have been observed to cause death in mosquito vectors. The first objective of this study was to investigate the cause of death in mosquitoes, Culex territans, that have fed on frogs with heavy infections of Hepatozoon species. The second objective was to determine the route travelled by these parasites through the body of C. territans from the blood meal in the midgut to the Malpighian tubules, where parasite development occurs. Culex territans mosquitoes were allowed to feed on green frogs with parasitaemia values of 5%. Blood-fed mosquitoes were fixed in 2.5% gluteraldehyde at specific times (24 hr, 36 hr, 48 hr, and 72 hr) post-feeding (PF). Fixed mosquitoes were embedded in TAAB resin, sectioned at 1 μm sections, stained and observed using bright-field microscopy. At 12 hr PF, the midgut was healthy and parasites had not invaded Malpighian tubules. At 36 hr PF, there was extensive damage to the midgut, but parasites were not yet present in Malpighian tubules. At 48 hr PF, there was extensive trauma to the midgut, and Malpighian tubules were riddled with parasite zygotes. At 72 hr PF, Malpighian tubules were infected with growing oocysts, but there was negligible damage to the midgut. The results support the hypothesis that mosquito death is caused by morphological trauma to the midgut, and is not likely a result of septicaemia. This further supports the hypothesis that Hepatozoon species penetrate the midgut and enter Malpighian tubules through the haemocoel, rather than entering the tubules at their origin near the junction of the midgut and the hindgut.

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https://scholar.acadiau.ca/islandora/object/theses:1241