Thursday, 13 September 2012

Amazing Aphid

A colleague showed me today an interesting article on aphids (see here, sorry non-Russian speakers). We discussed the famous experiments by Shaposhnikov. Shaposhnikov, apparently, actually managed to achieve reproductive isolation, one of the two main features of a biological species, the other one being numerous progeny. However, as far as I know, no one else could repeat Shaposhnikov's experiments. Chaikovsky points [1] that Shaposhnikov had to waste a lot of his time trying to defend himself from his hardline Darwinist colleagues. Some say that he nonetheless did continue his research and succeeded in crossing the border of the aphid genus but his later work was never published.

Aphid. Source: Science Photo Library.

Aphids are superorganisms because they actively use endosymbiosis, a special type of  symbiotic interaction whereby organisms live inside one another. It is interesting that, as stated in the above article, aphids are apparently phototrophs, i.e. it is believed that they are able to extract solar energy directly via carotenoid synthesis. If this is true, aphids are the only animal species known today which is capable of synthesizing carotenoids. All other animal species get them from food. Plants betake to a more complex process of converting solar energy which is called photosynthesis, whereby carbon is chemically bound from carbon dioxide in the air and is converted with the help of light into organic compounds. Carotenoid synthesis in aphids is regulated by only seven genes! It is thought that aphids borrowed them by way of a lateral transfer from a fungus species which is believed to have once been their parasite. The acquired genes code up for the enzymes necessary for carotenoid synthesis.

Aphids Infesting a Lupin. Source: Science Photo Library.

1. Yu.Chaikovsky. Nauka o razvitii zhisni: Opyt teorii evolutsii (The science of the development of life: An experience of the theory of evolution). Мoscow, КМК, 2006 (in Russian).