Intraerythrocytic merogony in Haemogregarina koppiensis (Apicomplexa: Adeleorina: Haemogregarinidae)

A first for Southern Africa: description of a new Heterobothrium (Monogenea: Diclidophoridae) parasitizing the evileye pufferfish Amblyrhynchotes honckenii (Tetraodontiformes: Tetraodontidae)

The monogenean genus Heterobothrium (Monogenea: Diclidophoridae) currently consists of 12 accepted species described globally from various pufferfishes (Tetraodontidae). This includes the economically important Heterobothrium okamotoi Ogawa 1991 that causes severe disease in the cultured tiger puffer Takifugu rubripes in Japan. During parasitological surveys targeting near shore marine fishes of South Africa, a new Heterobothrium was discovered on the gills of five evileye pufferfish Amblyrhynchotes honckenii with a prevalence of 100% and mean intensity of 23 (4-72). Specimens were morphologically studied using both light and scanning electron microscopy and molecularly characterized by sequencing the partial ribosomal gene 28S. Heterobothrium victorwepeneri n. sp. differs from its 12 congeners by a combination of morphological characters, such as fourth clamp pair (anteriormost, 180° inverted) as the smallest with some of the sclerites differing in shape from the other pairs, 8 to 9 genital hooks, number of testes 40-50, and absent isthmus. The 28S tree depicted two main branches, one clustering together species of mazocraeidean families while the other clustered together only species of the Diclidophoridae. Heterobothrium victorwepeneri n. sp. is the first species of its genus to be recorded and described from South Africa and from the tetraodontid A. honckenii. This study also provides for the first time 28S sequence for a species of this highly host-specific genus.

A review of parasite studies of commercially important marine fishes in sub-Saharan Africa

Scattered records of parasitic species infecting commercially important marine fishes in sub-Saharan Africa are known from just a few countries where concerted efforts have been made by local parasitologists (e.g. Senegal, Nigeria, South Africa). Most of these consist of taxonomic records or general surveys of parasite faunas associated with marine hosts, which may or may not have been of commercial value. Little to no multi-disciplinary research is conducted in most parts of sub-Saharan Africa and hence parasitological data are not commonly used to advise fisheries management procedures. This review summarizes current knowledge on all parasitological research associated with commercially important marine fish species in sub-Saharan Africa.

Three-dimensional visualisation of developmental stages of an apicomplexan fish blood parasite in its invertebrate host

Background

Although widely used in medicine, the application of three-dimensional (3D) imaging to parasitology appears limited to date. In this study, developmental stages of a marine fish haemogregarine, Haemogregarina curvata (Apicomplexa: Adeleorina), were investigated in their leech vector, Zeylanicobdella arugamensis; this involved 3D visualisation of brightfield and confocal microscopy images of histological sections through infected leech salivary gland cells.

Findings

3D assessment demonstrated the morphology of the haemogregarine stages, their spatial layout, and their relationship with enlarged host cells showing reduced cellular content. Haemogregarine meronts, located marginally within leech salivary gland cells, had small tail-like connections to the host cell limiting membrane; this parasite-host cell interface was not visible in two-dimensional (2D) light micrographs and no records of a similar connection in apicomplexan development have been traced.

Conclusions

This is likely the first account of the use of 3D visualisation to study developmental stages of an apicomplexan parasite in its invertebrate vector. Elucidation of the extent of development of the haemogregarine within the leech salivary cells, together with the unusual connections between meronts and the host cell membrane, illustrates the future potential of 3D visualisation in parasite-vector biology.

A new fish haemogregarine from South Africa and its suspected dual transmission with trypanosomes by a marine leech

Twenty two percent (22/98) of intertidal fishes of 10 species captured in South Africa at Koppie Alleen, De Hoop Nature Reserve (south coast) and Mouille Point, Cape Town (west coast), harboured single or combined infections of haemogregarines, trypanosomes and an intraerythrocytic parasite resembling a Haemohormidium sp. The haemogregarines included the known species Haemogregarina (sensu lato) bigemina (Laveran et Mesnil, 1901) Siddall, 1995 and Haemogregarina (sensu lato) koppiensis Smit et Davies, 2001, while Haemogregarina (sensu lato) curvata sp. n. was observed in Clinus cottoides Valenciennes and Parablennius cornutus (L.) at Koppie Alleen. This last haemogregarine is characterised particularly by its distinctly curved gamonts. Also at Koppie Alleen, squash and histological preparations of 9/10 leeches, Zeylanicobdella arugamensis De Silva, 1963, taken from infected C. cottoides and P. cornutus contained developmental stages of H. curvata and/or trypanosomes, but these were absent from haematophagous gnathiid isopods (Gnathia africana Barnard, 1914) taken from infected fishes. It is suspected that Z. arugamensis transmits the haemogregarine and trypanosomes simultaneously between fishes, a double event unreported previously from the marine environment.