Parasite makes ant mimic fruit

Parasites frequently modify the behavior of their hosts to encourage the infection of new hosts. For example, see this video (taken from the Planet Earth documentary) of the fungus Cordyceps that makes insects climb to the top of grass stems, and then erupts its fruiting body from the host's body, and disperses its spores over more hapless hosts from this elevated position. Yanoviak et al. (Am Nat 2008. Vol. 171, pp. 536–544; DOI: 10.1086/528968) describe a case of parasite-induced mimicry in the ant Cephalotes atratus. A nematode infection causes the gasters (rear portion of the abdomen) to become bright red and swollen, resembling a berry fruit, where normally it is black and inconspicuous. The infected gasters are also full of parasite eggs. Birds that feed on berries would then pop off these packets of parasite propagules, and pass out the eggs in their faeces. Ants congregate around bird faeces, which represent food resources to them, and collect them to feed to their brood, completing the cycle.

Here's the lesson from all this, kids: don't eat dung.

Birdsong and Human Speech

Speech and language seem to be uniquely human traits, which begs the question of how they arose. It turns out that a key regulatory gene controlling human speech, the FOXP2 (forkhead box transcription factor) gene, is also found in other animals, including songbirds. Knocking out these genes in humans (though accidental mutations) results in speech disorders associated with abnormalities in the basal ganglia, though exactly how they control the ability to speak is unknown. A team of German scientists used songbirds as a model for understanding the development of human speech. Instead of simply knocking out the gene, they used RNA interference to reduce FOXP2 levels in a specific area of the basal ganglia, known as Area X, in zebra finches, while they were in the stage of learning their song. This resulted in abnormal song patterns and provides a very persuasive example of how some genes can be directly linked to certain elements of behavior. However, note that the FOXP2 gene is a transcription factor gene that is part of the developmental toolkit, and so functions by regulating the expression of several other genes, so the actual pathway may be much more complicated that it first appears to be, so it would be misleading to simply call FOXP2 the 'speech gene'.