Three new species of Myxosoma (Protozoa: Myxosporidia) from East African freshwater fish

Abstract

1. Three new species of Myxosoma (Sporozoa, Cnidosporidia, Myxosporidia) are described from freshwater fish of the genus Tilapia in East Africa.2. Two of these, M. heterospora and M. brachyspora spp.nov., inhabit the abdominal viscera: the former was found in 41 of 43 fish examined, while the latter was less common. The third species, M. homeospora sp.nov., produces small oval or circular ‘cysts’ in the subdermal muscle and was found in two very young fish only. Spores resembling those of the first two species were also found in one Haplochromis sp.3. The spores of M. heterospora are roughly ellipsoidal but are very variable in shape, and range from 8·5–17·0 μ in length and 6·3–11·0 μ in breadth; the two anterior polar capsules measure from 2·0–9·5 by 1·5–3·5 μ. Those of M. brachyspora are flattened antero-posteriorly, measuring from 7·0–7·5 μ long and 12·0–13·5 μ broad; their polar capsules are from 2·5–3·8 by 2·3–2·5 μ in size. M. homeospora has ovoid spores with the anterior end narrowed, measuring from 13·5–17·0 by 8·5–11·0 μ; the polar capsules measure 4·0–6·0 by 2·0–4·0 μ.4. It is suggested that M. heterospora, at least, is pathogenic and may play a considerable part in reducing the availability of fish as food in this part of Africa.5. A check-list is given of all species of the genus Myxosoma.I thank Mr R. S. A. Beauchamp (then Director of E.A.F.R.O.) and his staff, also Mr G. Bowser (Manager of TUFMAC), for facilities and assistance in the examination of fish; also Dr G. D. Fryer and Dr D. J. Garrod for sending material to me in London, and Dr P. H. Greenwood for supplying the Haplochromis and checking the names of fish; also Messrs G. D. Lomax and P. E. Nesbitt for the preparation of sections. This work was commenced while I was employed at the East African Trypanosomiasis Research Organization.