From the University of Montreal , something that might actually be a good thing if true. If warmer temperatures make mostly male insects, then this might also apply to mosquitoes, and only the females bite. OK, it’s a bit of a stretch, but no more so than the press release.
Temperature influences gender of offspring
New study on parasitoid reveals that heat favours production of male progeny
Whether an insect will have a male or female offspring depends on the weather, according to a study led by Joffrey Moiroux and Jacques Brodeur of the University of Montreal’s Department of Biological Sciences. The research involved experimenting with a species of oophagous parasitoid (Trichogramma euproctidis), an insect that lays its eggs inside a host insect that will be consumed by the future larvae.
“We know that climate affects the reproductive behaviour of insects. But we never clearly demonstrated the effects of climate change on sex allocation in parasitoids,” Moiroux explained.
The study was carried out in collaboration with Guy Boivin of the Horticulture Research and Development Centre of Agriculture and Agri-Food Canada, and published in the May issue of the journal Animal Behaviour.
Cold impairs gender selection
As in bees, wasps, and ants, the gender determination of Trichogramma parasitoids is called “haplodiploid,” that is, fertilized eggs produce female offspring, while unfertilized eggs produce male offspring, summarizes Moiroux. “It is possible to predict whether the parasitoid will lay a son or daughter by observing the presence or absence of a pause in its abdominal contractions at the time of spawning,” he says. “A pause means the egg will be fertilized. Conversely, the absence of a pause means the egg will not be fertilized.”
To know whether this particular behaviour is modified by climate, the researcher exposed female Trichogramma to three different temperatures: 34°C (high), 24°C (medium), and 14°C (low). The study found that when it was hot, females deliberately produced more males than at medium temperature – at 34°C, the number of males produced increased by 80%.
The ability of Trichogramma to “program” the sex of their offspring is compromised, however, when the temperature is cold. “There was a physiological stress that was not related to the females’ choice,” notes Moiroux. “They intended to spawn as many females as during medium temperature, but the eggs were not fertilized after all. There were therefore more males produced at low temperature.”
Increasing fitness
In insects, fitness is positively correlated with the size of an individual, and this relationship is greater in females than in males. “Larger females live longer and have higher fertility, whereas males are relatively less penalized than females when they are small,” Moiroux said. “It is therefore advantageous for mothers to have the largest female offspring possible and use hosts that will produce smaller offspring for males.”
However, in a hot environment, offspring are smaller. This is why females tend to use hosts found in hot areas to produce males and reserve hosts in colder areas (e.g., in the shade of hedges) to produce females.
Biocontrol
As part of this study, which was funded by the Ouranos Consortium, Moiroux tried to understand the possible role of global warming on the relationship between crop pests and their natural enemies – parasitoids and predators. Among the issues addressed, he sought to determine whether there is an effect of “phenological asynchrony” between parasitoids and their hosts, and therefore an impact on the availability of host eggs and on pest control by their natural enemies. “Predators and parasitoids are more sensitive to climate change, and this is why many researchers expect an increase in episodes of phenological asynchrony. This could be very harmful to crops if hosts escape the control of their natural enemies,” he said.
In Quebec, the European corn borer is a pest that farmers face every year. The parasitoid Trichogramma, for its part, is an ally since its larvae kill this insect host. “It is of the utmost importance to clearly identify harmful and beneficial insects in the field in order to adopt an appropriate strategy for integrated pest management,” Moiroux said. He will now be looking at which species of soybean pests could come to Quebec in the coming years due to climate change.
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When the rainy season arrives and temperatures SHOOT UP there is a sharp increase in the number of insects in my local. I always dread the hot, humid months which are full of flies, mosquitoes, rampant spiders and bees. This is a good thing despite my inconveniences. Would Al Gore ever talk like this? Of course not because he wants to make over 1 billion Dollars. What’s 2 large houses between global warming friends. We have a planetary emergency between hypocrites.
Jimbo says: May 22, 2014 at 3:50 pm
Is it just possible that as the climate changes insect acclimatization, adaptation can change?
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Yepper. Takes only about 25 generations for a SNP to completely spread in the entire (small) population of insects. [see studies of insect resistance from Pimentel et al]
25 generations is about 1.5 years in tropical insects, 400-500 years for humans.
However, for most environmental variability like these, insects hardly need a genetic basis for changes. Differential production & modes of action of enzymes and proteins or simple behavioral change (eg resting in sheltered locations) within an individual lifespan is possibly enough to deal with these kinds of nothings. If it was worth a literature search, someone could possibly find the answer already out there.
@ur momisugly Jimbo
Actually, I now recall that newly introduced Dengue, Yellow Fever, Chikungunya vector Aedes albopictus has enlarged its usual northern range in the USA far into the temperate zone (Minnesota to Maine) by a recent adaptation for cold tolerance.
ALL since it was introduced into Houston in 1985. Not bad for a supposedly tropical mossie.
Also, mosquitoes use CO2 (from respiration) to hone in on their human and animal victims. It stands to reason that a higher background concentration of CO2 will make it harder for them to find their prey.
At this time in Central VA, it’s’ finally getting into the 80s with a few mosquito bites. By August, when it’s 90s temp and 90s humidity, you can’t hear yourself think for all the roaring around your head. Granted, they do tend to lay low until dark. Luckily, the gators don’t get up this far.
Eric Simpson says: May 22, 2014 at 7:24 pm
It stands to reason that a higher background concentration of CO2 will make it harder for them to find their prey.
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So you would think. But mosquitoes are not so simple-minded despite their tiny little itsy bitsy teeny ‘brains’. Different species & different ages respond to different organic molecules, heat, motion, prey color, as well as CO2 at different times and different distance from the prey. It’s quite interesting to read reviews of CO2 traps made by qualified scientists. Certain species in one trap but few in another and vice versa and so on. But they all agree on one thing: the traps don’t actually decrease the number of or eliminate bites !! FAIL
Jimbo says:
May 22, 2014 at 4:11 pm
Global warming might make less biting, itching, scratching
“Global warming will mean MORE ‘biting, itching, scratching’ I am afraid. I live in the tropics and I have lived in London. Biting, stings, scratching is the norm I’m afraid – it’s what happens when breeding rates / biodiversity increases due to warmer weather / climate.”
Have you been to Scotland in the summer or any of the northern tundras for that matter? There is too much emphasis placed on average temperature changes whereas I have suffered mosquito bites every year of my life in the UK and each summer does not have a consistent temp. We have removed huge areas of wetlands in the UK and these were where Malaria was prevalent. In more recent years people removed ponds from their gardens for fear of toddlers falling in and drowning and probably convenience. So if people are now putting ponds back in and having water buts then we can only ever return to a mosquito population the same or less than before because there just isn’t the wet surface area available anymore and temperature is not the driver, its abundant standing water and abundant warm blooded food supply.
Just to reiterate with this extract from Wikipedia:
“Arctic mosquitoes may be active for only a few weeks as pools of water form on top of the permafrost. During that time, though, they exist in huge numbers and can take up to 300 ml of blood per day from each animal in a caribou herd.”