They spawn by releasing gametes into the water: a female Atlantic oyster tends to release clouds of eggs in a series of wet puffs, while males send sperm forth in a stream.
Later, their progeny will head back into the mosquito's salivary glands and infect its next victim.By vaccinating humans against proteins on the gametes, still-active immune agents in the blood sucked up by the mosquito can recognise and destroy the parasites as soon as they come out of hiding.
Generally, the male releases his gametes first, which acts as a signal to any females nearby.
Once a tipping point was reached, oysters were too far apart for enough of their gametes to meet, so the population could not sustain itself.
Once the pair of gametes connect, they become a larva that drifts and swims in the tidal current, propelling itself by means of a little organ ringed with cilia called a velium.
"The gametes swim out into a lethal sea," explains Professor Carter, "and they just pop and are gone.
But male oysters can spawn in the style of females, and vice versa; and hermaphroditism, in which eggs and sperm shoot out of the same oyster at the same time, also occurs, albeit rarely.Fertilisation occurs when opposite gametes meet in the water: hence the advantage offered by proximity.
The gametes bear numerous spirally arranged flagella.
Meiosis produces the haploid gametes.
Sexual reproduction is by motile gametes.
During fertilization, male and female gametes fuse, producing a diploid (i.e., containing paired chromosomes) zygote.
