Sexual development in malarial parasites: gametocyte production, fertility and infectivity to the mosquito vector

Abstract

Using cloned lines of Plasmodium berghei producing mixed asexual and sexual (clone 234L) and purely asexual (clone 233L) parasitaemias, the courses of parasitaemia, gametocytogenesis, exflagellation, ookinete production in vitro and mosquito infectivity have been followed. For clone 234L mosquito infectivity is maximal at day 3 and has ceased by day 6 post-infection. Conversely, gametocytogenesis, exflagellation and ookinete production are at minimal levels at day 3 and rise to peaks between days 10 and 15 of infection (in TO mice infected with blood at mechanical blood passage 3). Sexual potential declines progressively with sustained mechanical passage (up to P14). Gametocyte conversion is highest early in infection and declines exponentially; however, upon each mechanical passage conversion is again raised but decreases more rapidly with succeeding passages. For practical mosquito transmission in the laboratory we consider P8 to be the useful limit for mechanical transmission for this parasite clone. Asexual parasite growth (virulence) is more rapid with increased mechanical passage inducing a rapid fall in haematocrit. By P14 the course of infection closely parallels that of the purely asexual clone 233L.

Avian malaria: a new lease of life for an old experimental model to study the evolutionary ecology ofPlasmodium

“…These results fit in with the general prediction that, in the absence of mosquitoes, serial passages should select for higher rates of asexual reproduction and thus for higher parasitaemia [20,27]. In some cases, this increase in parasitaemia has been accompanied by an increase in transmission potential, measured as gametocyte production [19], whereas in others gametocyte production has been reduced [28].…”

Phenotypic Plasticity in Bacterial Plasmids

“…pede host growth, thereby reducing the plasmid's poFor parasites that feature both horizontal and vertical tential for vertical transmission. We previously demonmodes of transmission, susceptible host density (R) should determine which mode is selectively favored (May and strated this trade-off when plasmids evolved increased Anderson 1983;Herre 1993;Bull 1994;Ewald 1994), horizontal transfer at the expense of decreased vertical provided there is a genetic trade-off between transfer transfer and vice versa (Turner et al 1998).…”

“…(damage to host fitness; May and Anderson 1983;Bull 1994;Ewald 1994). However, available host density did not mediate the trade-off because plasmids featuring can fail to invade if its net rate of spread is negative increased (and reduced) conjugation evolved in all (r Ͻ R Ϫ ␥P), where R is the growth rate of recipients treatments (Turner et al 1998).…”

Taking Stock: Relating Theory to Experiment

“…Myxoma virus of rabbits (Fenner and Fantini 1999); Phages of E. coli bacteria (Bull and Molineux 1992); Malaria parasites of humans (Dearsly et al 1990;Day et al 1993);…”