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Historical review of piscine trypanosomiasis107to the kinetoplast ). The author also reported two The above two patterns of multiplication described forabnormal forms, one with a kinetoplast and no nucleus fish trypanosomes are not similar, that for T.and other with a kinetoplast and two nuclei which did danilweskyi being by transverse binary fission and fornot fit into the sequence of division mentioned by him. T. trichogasteri being longitudinal binary fission,The division was thus transverse. Gupta, Gupta and however, both are symmetrogenic as characteristic ofSharma(1987) described the division of T. mastogophereans (Levine et al., 1980).trichogasteri in Colisa fasciata and in contrary to Woo(1981a), the division of the parasite was longitudinal.Lom and Dykova (1992) reported division in fishMultiple fissions were not observed.trypanosomes to start with production of a newflagellum, followed by a kinetoplast and then nuclearThe division in T. trichogasteri was initiated by division. The cell divides longitudinally startingkinetoplast division (longitudinal as well as anteriorly (eg. T. remarki). In T. carassii, the newtransverse) producing nearly equal sized kinetoplasts. flagellum is flipped posteriorly to extend in a directionThis was followed by nuclear division (transverse) opposite to that of the old flagellum and newand cytokinesis proceeding from the posterior end cytoplasm is grouped along it. After nuclear division,towards the anterior. The mother kinetoplast retained one of the nuclei moves posteriorly past the twothe undulating membrane and the free flagellum while kinetoplasts. Finally, a transverse, unequal cleavagea new flagellum arose from the daughter kinetoplast occurs between the kinetoplasts; the posterioreither simultaneous or subsequent to cytokinesis. As daughter individual is smaller. The vesicular nucleuscytokinesis progressed, each cell body contained one divides by a modified mitosis (“closed”nucleus and the undulating membrane was the last to pleuromitosis).acquire perfection as also reported by Woo (1981a). T.kargenensis also shows a similar pattern of divisionThe ploidy of trypanosomes reproducing largely by(Fig. 3) where division commences from thebinary fission still remains an open question. The mainkinetoplast, followed by nuclear division (Fig. 4d, e)reason for uncertainty in this basic fact is the absenceand cytokinesis (Fig. 4f). However, in contrast, theof the cell cycle phase with distinct easily counteddivided trypanosomes remained attached at theirchromosomes. For long, trypanosomes have beenanterior ends prior to separation into two youngconsidered to be asexual (Hoare, 1972), however, Taitparasites in these cases instead of being attached at(1980) doubted on this concept by studying enzymetheir posterior ends (Woo, 1981a).patterns of T. brucei and the existence of sexuality hasbeen suspected. The assumptions of the existence ofAsexual processes in trypanosomatids werepredominately based on zymograms and geneticequilibrium studies and supported the idea of diploidyBindirectly (Tait, 1980). However, there is as yet noindication of sexual reproduction in fishtrypanosomes.EC10 µmFig. 3. A F. Sequence of divisional stages in Trypanosomakargenensis from Heteropneustes fossilis. A, kinetoplastdivision; B, beginning of cytokinesis; C, nuclear division; D, F,cytokinesis and formation of 2 daughter trypanosomes.DFUltrastructural studies on the division of theepimastigotes of T. cobitis were conducted by Lewisand Ball (1981). The investigations were based onelectron microscopy of the epimastigotes in the leechvector, Hemiclepsis marginata and in culture. Thedivision followed the trypanosomatid pattern ofduplication of basal body, kinetoplast and thennucleus followed by cytokinesis with the exceptionthat the dividing epimastigotes within the vector hadmulti-axonemal flagella whereas in culture, the newflagellum grew separately alongside the original. Thekinetoplast duplicated by both lateral and equatorialenlargement.The above microscopic and ultra structural studies