Sex, pests & photosynthesis: Awesome aphids

Aphids are pretty cool little creatures, but not everyone appreciates them as much as I do. The little sap-suckers have become the most dreaded enemies of farmers and gardeners around the world due to them being one of the most destructive pests for cultivated plants. BUT LOOK AT THE LITTLE GUYS!

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My attention was first drawn to aphids when I learned about their interesting reproduction strategies. First off, aphids can reproduce through a process called parthenogenesis, which means that the females can produce offspring asexually without the need for males. During spring and summer, virtually all of the aphid population is made up of females who are equipped to reproduce on their own and the live offspring they give birth to are – take a deep breath – already pregnant. THEY GIVE BIRTH TO LIVE APHIDS WHO ARE ALREADY PREGNANT. If that doesn’t blow your mind, what’s wrong with you?

As you can imagine, this process results in a lot of female aphids in a very short amount of time, and that’s important for a teeny weeny creature that is rather far down the food chain. You gotta keep your numbers up, and aphids have evolved to do this very well. However such vast populations can cause problems for creatures that spend most of their lives on their host plant. When a plant becomes overcrowded with aphids and food resources deplete, a hormonal changes triggers the production of aphids with wings. These winged individuals fly off and disperse, find another host plant and continue to produce wingless offspring there. Pretty amazing.

But the aphid sex (or lack of?) story does not end there. As it turns out, some aphids opt for sexual reproduction at a different time of the year. When autumn rolls around, life becomes a bit tougher for the aphid community as the plants they depend on to live begin to die. In response to these harsher conditions, the females of some aphid species begin to produce “sexual” males and females (which may not have mouths – clearly they have one purpose and one purpose only, no need to waste time eating and surviving…).  These sexual individuals mate which results in the female laying eggs on a plant or tree that will hatch the following spring, and the cycle begins again.

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This is a wonderful example of how environmental conditions can alter the reproduction strategies of a species. But aphids have been in the news this week for quite a different reason. There is evidence that they may be the first animal known to use a process very similar to photosynthesis as a way of harnessing energy directly from the sun. Researchers have found that aphids can make their own carotenoids, (a pigment), as a plant does (incidentally, it is this pigment which gives the aphid its green colour). Other animals have carotenoids in their body, but they gain them by eating plants and algae rather than produce them on their own, probably because it would be a very expensive use of precious energy.

Puzzled as to why the aphids would produce such costly chemicals, researchers measured the levels of adenosine triphosphate (ATP), which is a way of measuring energy transfer. Using laboratory aphids with differing levels of carotenoids they found that green aphids (who have a high number of carotenoids) make significantly more ATP than white ones (with low levels of carotenoids), and orange aphids (who have a moderate amount of cartenoids) made more ATP while exposed to sunlight, and less when placed in the dark.

This is a really cool finding, but more research needs to be done before we can conclude that aphids are actually capable of a photosynthesis-like system, and now we have new questions to ask, such as why would they need to use this process in the first place? GO FIND ANSWERS, SCIENCE!

 

References

Valmalette, J. C. et al. Sci. Rep. http://dx.doi.org/10.1038/srep00579 (2012).

Photosynthesis-like process found in insects. Nature News

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