Rhabdospora Research Articles

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

Results of a survey of Cyprinus carpio, carp, in Croatia, Yugoslavia and data from carp reared under controlled laboratory conditions, have provided new information on the enigmatic nature of Rhabdospora thelohani or “rodlet cells”. Carp larvae were obtained in the laboratory by artificial fertilization and reared so as never to be in contact with other fish. Young fish were sacrificed at 10 and 60 days of age, serially sectioned and examined for R. thelohani. In 10 day larvae, organisms were never observed. However, 60 day fry had rhabdosporans loosely associated with the afferent branchial arteries and ventral aorta distal to the bulbus arteriosus. More proximally, they appeared to aggregate at the periphery of the aorta, become associated with the endothelium while decreasing in number at the periphery and finally localized primarily inside of the bulb. Results of the survey showed one out of a total of five (20 %) 11 mm carp contained R. thelohani; the organisms were found associated with the adventitia of the ventral aorta but not the bulbar tissue per se. The bulbi of all carp g30mm in length, from all four fish farms sampled, contained varying numbers of rhabdosporans. These observations suggest a migration of rodlet cells to the bulb and suggest but do not conclusively prove that they are not parasites.

Rhabdospora thelohani Laguessé, 1906 Is Not a Member of the Apicomplexa

Rhabdospora thelohani Laguessé, 1906 Is Not a Member of the Apicomplexa

Rhabdospora thelohani Laguessé, 1895 (Apicomplexa): new host and geographic records with taxonomic considerations.

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.

Intracardial Mesotheliomas and a Gastric Papilloma in a Giant Grouper, Epinephelus itajara (Lichtenstein)

A giant grouper, Epinephelus itajara (Lichtenstein), was found dead in its tank. The principal necropsy findings consisted of multiple tumors in the ventricle of the heart, a tumor mass in the stomach, and protozoa-like organisms in the heart tumor, bile ducts and kidney collecting ducts. The heart tumors were identified as mesotheliomas the stomach tumor as a papilloma. The morphology of the protozoan-like organisms was similar to that of Rhabdospora thelohani (Languesse).

The hepato‐renal syndrome in cultured turbot (Scophthalmus maximus L.)

The histopathology of biliary hyperplasia and renal calcinosis, associated with infections of two parasites, Myxidium incurvatum and Rhabdospora thelohani, is described in turbot, Scophthalmus maximus (L.), from Scottish marine fish farms and wild populations. Liver and kidney lesions were divided into four, and parasite infections into five grades of severity. A few of the fish examined were not parasitized, but every one showed some evidence of pathological change, even the apparently normal individuals from all populations. Although there is a positive association between the parasitic and pathological data, parasitism is not considered to be the principal cause of either the hepatic or renal lesion; the evidence suggests rather a secondary opportunist role for the parasites. The general severity of the condition in captive stocks suggests that the cause may lie in the fundamentals of present techniques of turbot husbandry, but no specific agent has been identified. A case is put forward for considering Rhabdospora to be a parasite rather than a specialized host cell.

Ultrastructure and Development of Rodlet Cells in Gill and Intestine of Walleyed Pike (Stizostedion vitreum)

Tissues from the gut and gill of walleyed pike, ranging in age from birth to one year, reared in tanks separate from mature fish, were examined with the electron microscope for rodlet cells. While these cells are thought to be intercellular parasites (Rhabdospora thelohani) by some investigators, the present study supports the view held by others that they are secretory cells of the fish. Mature and previously undescribed immature rodlet cells were examined.Mature rodlet cells contain a basal nucleus with a supranuclear Golgi and associated saccules and vesicles. Large club-shaped sacs, the narrow parts of which converge upon an opening in the apex of the cell, comprise much of the cytoplasm. The sacs contain a dense-staining amorphous “core” substance surrounded by less dense material.

Is Rhabdospora thelohani (Laguesse) a sporozoan parasite or a tissue cell of lower vertebrates?

An examination with light and electron microscopes has been made of the cell type which is considered by some authors to be a sporozoan parasite,Rhabdospora thelohani, and by others to be a tissue cell of fishes and amphibians.The cell type was found in the minnowPhoxinus phoxinusin many tissue sites, including olfactory and pharygneal epithelia, kidney, eyes and brain. In some specimens it could not be found in any tissue.The cell has a thick fibrous wall, a basal nucleus, an apical mitochondrial zone, a Golgi body, and from 8 to 50 characteristic refractile rodlets.The rodlets give a negative reaction to the Feulgen test for nuclear material, but are positive to the periodic acid–Schiff stain, a test for polysaccharide. Glycogen does not appear to be present in the rodlets.Under certain circumstances the rods rupture the cell wall and may protrude in the apical region of the cell.The structures described are discussed with the evidence for and against a parasitic interpretation of the cell. It is concluded thatRhabdosporais a protozoan parasite, whose exact functional and taxonomic status is as yet unknown.I am grateful to Professor G. E. H. Foxon and to Professor P. C. C. Garnham for their encouragement, advice, and helpful criticism of the manuscript. I am further indebted to the National Spastics Society for the use of the electron microscope housed in Guy&s Hospital Medical School, and to Mr I. D. Bradbrook for his assistance with the histological techniques.