Rhabdospora thelohani Laguessé, 1895 (Apicomplexa): New Host and Geographic Records with Taxonomic Considerations*

Abstract

New fish species and geographic records for Rhabdospora thelohani Laguessé, 1895 (rodlet cells) are presented. Additionally, the ultrastructure of R. thelohani in Alburnoides bipunctatus ohridanus Karaman, Borostomias antarcticus (Lönnberg), Leuciscus cephalus albus Bonaparte and Rutilus rubilio (Bonaparte) is compared with that reported by other authors and with members of Subphylum Apicomplexa. The ultrastructure of R. thelohani was similar in all the fish species examined; however, the organism was not present in all members of any single species and had intertissue density variations. Rhabdospora thelohani is pyriform, averaging in size 7 X 12 micrometer, with a basal nucleus. The surface complex is composed of a layer (0.5 micrometer diameter) formed by microfilaments (9.3 nm) and an outer trilaminar membrane (9.3 nm). The cytoplasm contains structures identical to rhoptries, micronemes and subpellicular microtubules. Mitochondria, Golgi apparatus, and rough endoplasmic reticulum were not observed, althouth free ribosomes were present and arranged in a vesicular pattern. The observations suggest that the organism moves between cell of epithelial layers and is either released into a lumen intact or passively or actively discharges its contents into a lumen. Results from this study indicate that R. thelohani should be considered a member of Apicomplexa unless definitive evidence is presented to the contrary.

The inflammatory response of fish to helminth parasites

“…Contrasting points of view of the nature of rodlet cells (RCs) have been proposed since their first description by Thélohan (1892). The view that RCs are parasites was held by several authors after 1895 (Laguesse, 1895;Bannister, 1966;Mayberry et al, 1979;Viehberger & Bielek, 1982;Bielek & Viehberger, 1983;Richards et al, 1994). Authors that favoured the parasitic nature of RCs, for a long time believed that they were sporozoan (Mayberry et al, 1979).…”

“…The view that RCs are parasites was held by several authors after 1895 (Laguesse, 1895;Bannister, 1966;Mayberry et al, 1979;Viehberger & Bielek, 1982;Bielek & Viehberger, 1983;Richards et al, 1994). Authors that favoured the parasitic nature of RCs, for a long time believed that they were sporozoan (Mayberry et al, 1979). They based their arguments on electron microscope observations which they claimed gave confirmation that Rhabdospora thelohani (rodlet cell) belonged to the Apicomplexa (Mayberry et al, 1979).…”

“…Authors that favoured the parasitic nature of RCs, for a long time believed that they were sporozoan (Mayberry et al, 1979). They based their arguments on electron microscope observations which they claimed gave confirmation that Rhabdospora thelohani (rodlet cell) belonged to the Apicomplexa (Mayberry et al, 1979). The main arguments of those claiming that RCs are parasites included: their numbers vary from fish to fish; often they cannot be found in all individuals of the same species; they can be encountered in different tissues of the same species.…”

Rhabdospora thelohani: Epidemiology of and migration into Cyprinus carpio bulbus arteriosus.

“…Numerous papers have been published on various aspects of R. thelohani, or "rodlet cells" , with extensive reviews appearing in 1978(MORRISON and ODENSE 1978MAYBERRY et al, 1979). In the review by MAYBERRY et al (1979), it was argued that R. thelohani is a parasite and should be included in the subphylum Apicomplexa, at least until the life cycle is elucidated. Their conclusion was based on evidence that included: 1) that the organisms contained organelles characteristic of apicomplexans and 2) that the organisms are not found in all fish species nor in all members of any single species.…”

Epithelium of the Intestinal Tract of a Freshwater Teleost, <i>Schizothorax curvifrons</i> Heckel (Cyprinidae, Cypriniformes, Pisces): An Ultrastructural Study

“…These distinct cells have been classified as apicomplex parasites (Bannister 1966, Iwai 1968, Barber et al 1979, Mayberry et al 1979 or, based on the species distribution and morphological features of the cells, as normal somatic cells performing a set of functions (Leino 1974, Desser and Laster 1975, Morrison and Odense 1978, Mattey et al 1979. Their occurrence in Schizothorax curvifrons is a first record for this species although their details were not worked out in this study.…”