Longevity and germination of Edhazardia aedis (Microspora: Amblyosporidae) spores

Edhazardia aedis is a polymorphic microsporidium of mosquitoes that is both horizontally and vertically transmitted to its host. Because it is being developed for biological control of mosquitoes, detailed knowledge is needed regarding the longevity and germation of its fragile, mosquito‐infectious spore. Spores responsible for horizontal transmission were extracted from 7–10‐day‐old larvae (reared from infected Aedes aegypti eggs) and purified by Ludox density gradient centrifugation. Mature spores were variable in specific gravity, being found throughout the 20 and 60% zone in Ludox gradients. The optimal environment for spore germination was dilute KCl at pH 10.0–11.0; ammonia inhibited germination. Osmotic inhibition was almost complete in both sucrose and polyethylene glycol at concentrations equivalent to 40 atm. The spores retained their viability for a maximum of 21 days at 23±2°C, whereas when held at 5±2°C, their viability was completely lost within two days post‐harvest. Potential for germination decreased along with infectivity, providing a simple assay for spore viability.