Effects of cyanobacterial crude extracts from Planktothrix agardhii on embryo-larval development of medaka fish, Oryzias latipes.

Embryonic toxicity from exposure to microcystins, cyclic hepatotoxic heptapeptides from cyanobacteria, receives increasing attention as a public human health biohazard. Using a microinjection technology, we have introduced cyanobacterial extracts from Planktothrix agardhii directly into the vitellus of late neurula embryos (stage 19) of medaka (Oryzias latipes). Microinjection (2 nL) of P. agardhii PMC 75.02 extract containing microcystins (MC) resulted in a dose-dependent mortality of embryos. Survival rates were reduced up to 81% with extract concentrations of 10 mg mL(-1) (EC(50)=7.8 microg mL(-1)). On the other hand, injection of P. agardhii PMC 87.02 extract in which no microcystin could be detected resulted in much less embryonal toxicity (EC(50)=460 microg mL(-1)). In addition, advanced embryonic hatching processing was limited with PMC 75.02 crude extract and less obvious than had been described with pure MC-LR injections. In agreement with the known hepatotoxic effects of microcystin, embryos injected with PMC 75.02 extract consistently displayed hepatobiliary abnormalities. Loss of glycogen content of the hepatocytes and hepatic haemorrhage were evidenced in surviving post-hatching juveniles. Thus, the methodology presented in this paper should be a valuable tool to analyse the effects of crude extracts of cyanobacterial toxins on the development of aquatic vertebrate embryos.

Influence of breeding sites features on genetic differentiation of Aedes aegypti populations analyzed on a local scale in Phnom Penh Municipality of Cambodia.

This study analyzed genetic differentiation of 20 Aedes aegypti populations collected along a street in Phnom Penh Municipality of Cambodia. Using allozyme and microsatellite variations, we demonstrated that populations were differentiated and the pattern of differentiation was dependent on the type of breeding sites. Moreover, insecticide treatments with temephos mostly affect the population functioning of discarded containers. Low gene flow detected could limit the natural diffusion of resistant populations that might instead take advantage of human displacements to spread.