Aspects of the morphology and life history of Oculotrema hippopotami (Polystomatidae: Monogenea)
Moeng, Itumeleng Amos
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Being the only monogenean known from a warm-blooded animal and from a mammal Oculotrema hippopotami Stunkard (1924) took a major leap in monogenean evolution. After its description in 1924 various researchers rejected the claim that it came from the hippopotamus and made it out as a mislabeled specimen. It was only 40 years later that this parasite received full recognition. In spite of the fact that it was described more than seven decades ago, only a few papers on this parasite have seen the light. During 1996 this parasite was rediscovered in South Africa. A hippopotamus culling program in Kwazulu-Natal gave an opportunity to study this parasite. The present study is the first detailed attempt to study the morphology and life history of Oculotrema hippopotami. The approach in this study was as follows: 1. Background on the host's morphology, behaviour and phylogeny is given. The hippopotamus' eye is situated deep in the orbit with the result that a deep crevice is present all around the eye, which serves as habitat for the parasites. 2. The external morphology of the egg, oncomiracidium and adult parasite was studied USIng scannmg electron rrucroscopy. This is the first ever scanrung electron microscopical study of 0. hippopotami and this study revealed many new information. 3. The internal morphology of the adult parasite was studied histologically using wax sections. This revealed unique musculature in the mid piece that has never before been reported for any polystomatid parasite. 4. Sperm morphology and the ultrastructure of the musculature in the mid piece was studied at transmission electron mieroeope level. Indications are that the sperm morphology is very similar to that reported for other polystomatids. 5. Infection levels for different seasons were compared. In contrast with most other polystomatids that reproduce during the warmer summer months, 0. hippopotami lays eggs during the cooler winter months. 6. The parental care and behaviour of a pair of hippopotami with a newborn calf were studied. A very close bond with long periods of physical contact was observed. This could give an ideal opportunity for parasite transmission from mother to calf.