Videomicrofluorometry on living cells and discriminant factorial analysis to study cell cycle distributions.

After a rapid overview of the approaches used to study cell cycle, a fluorescent digital imaging microscopy method is proposed. This method is improved by a factorial analysis relying on the evaluation of several parameters recorded on each living cell. Single lympho-blastoid living cells are labeled with three fluorescent markers: Hoechst 33342 for nuclear DNA, Rhodamine 123 for mitochondria and Nile Red for plasma membrane. For each cell, morphological and functional information parameters are obtained. A typological analysis is used to separate control cells into four groups: G0-G1, S, G2+M and polyploid cells Gn. These control cells define a learning population used to analyze untreated and adriamycine treated cells as supplementary individuals in a discriminant factorial analysis. Such an approach allows to accurately evidence the change of the values of some cellular parameters.

Infection patterns of Myxobolus heterospora in two tilapia species (Teleostei: Cichlidae) and its potential effects.

A Myxobolus heterospora (Baker, 1963) infection was found in 2 euryhaline tilapia species, Sarotherodon melanotheron melanotheron (Rüppel, 1853) and Tilapia zillii (Gervais, 1852), from a brackish water lake, Lake Nokoué (Benin, West Africa). The histology and ultrastructure of different levels of infection in intestinal connective tissues and wall tissues is described. A total of 391 S. melanotheron melanotheron and 222 T. zillii were examined from October 1987 to October 1989. M. heterospora was found throughout the study period, with a total prevalence of 42.19 and 26.57% for S. melanotheron melanotheron and T. zillii respectively. There was a statistically significant difference in occurrence as a function of season in S. melanotheron melanotheron but not in T. zilli, and there was a significant difference for size and sex in the former and for sex in the latter. M. heterospora induces total destruction of the intestine structure and probably leads to osmoregulatory disturbance. Further investigations of this myxosporean infection are necessary to determine its real effect on the host, since host survival and osmoregulatory rate have not yet been assessed.

Occurrence of myxosporean parasites in the gills of two tilapia species from Lake Nokoué (Bénin, West Africa): effect of host size and sex, and seasonal patterns of infection.

The gill myxosporean parasites of 2 euryhaline tilapias from Lake Nokoué, Sarotherodon melanotheron melanotheron (Rüppel, 1853) and Tilapia zillii (Gervais, 1852), were investigated from October 1987 to October 1989. A total of 391 S. m. melanotheron and 222 T. zillii were examined. Both of the fish species studied were infected by 3 host-specific myxosporean parasites for which prevalence greatly varied during our investigations. The 2 most common ones were Myxobolus sp. and M. zillii, which were located in the branchial filament. No significant fish sex effect was found for these 6 different myxosporean parasites. As seasonal pattern was clearly demonstrated for M. zillii while a host size effect was found for M. dossoui. However, further investigations of these myxosporean infections are necessary to determine the real effect of these parasites on their host, as host fecundity and survival was not assessed.