Curator Terrestrial Invertebrates Julia Kasper looks at the reproductive lives of our local mosquitoes.
The salt pool mosquito (Opifex fuscus) can just be found in New Zealand and it is our only rock pool mosquito. From an evolutionary perspective they show quite ancient mosquito characteristics. They look stout, have a short proboscis (snout), and short but slender antennae (both males and females). But most random are their mating habits.
They breed in brackish and saline coastal rock pools above the high tide line from around South Auckland, Tauranga, Taranaki, Hawke’s Bay, and Wellington down to Nelson, Marlborough, Canterbury, Otago, and most offshore Islands.
The eggs are laid singly just above the water surface and can withstand desiccation. They hatch after submergence and the larvae are able to stay quite some time underwater, filtering particles of food out of the water or at the bottom. From time to time they need to reach the water surface in order to gain some air. Both pupa and larvae can be found all year round with the highest numbers in late summer.
So far, so normal – now to the unusual part: the male mosquitoes emerge from the pupal stage much earlier than the females. They are usually found sitting on the water surface of the rock pools in swarms, waiting for the female pupae raising to emerge. The male uses long claws on its fore legs to grab onto a pupa while this one is freeing itself from the pupal casing.
The male then attempts to mate with the pupa regardless of the gender, although they usually abandon other males fairly quickly. The fact that the male salt pool mosquito doesn’t need to search for females might explain their slender antennae. Their male insect relatives normally detect the smell of the female pheromones with their bushy antennae from far distances (you might have realised, for example, that male moths have enormous antennae and that’s why they are one of the best chemical detectors in the world and are even copied for nano-technology).
Females that have not been mated within 24 hours of emergence will not be mated with thereafter. But once a female mosquito has been mated during emergence, they do not mate again and are able to lay their first egg batch without a blood meal. Apparently they have had enough protein rich food during their larval life. That means they must have got some little animals on their plate. However, any subsequent egg batches require a blood meal.
And this one can be quite painful for humans, which they will readily bite during the day and at night if located within their habitat range. Usually New Zealand’s endemic mosquitoes are mainly bird biters as there haven’t been any warm-blooded mammals around for a very long time. Only seals in coastal areas (and bats in caves) made the exception.
Luckily, there is no known or suspected natural vector status (this means they don’t carry any diseases). Only under lab conditions it has been shown that they were able to be a laboratory host of Whataroa virus.