Specialized specialists
The division of labour in New World army ant societies of the genus Eciton might have made Adam Smith proud. Not only do they have castes, such as soldiers and workers, but several species in the genus have castes within castes. They have workers, called submajors, that specialize in the task of transporting prey. Researchers had already noted that about three per cent of workers in some species were submajors, with longer legs and disproportionately large heads and mandibles. But they could not, until now, explain what might have favoured their evolution.
Eciton army ants need to be mobile. They feed on other ants, as well as insects and spiders, and also stick to a cycle of raids and migrations, wherein an entire colony can migrate overnight-queen, larvae, prey, and all-workers hauling loads beneath their bodies. Two British biologists at the University of Bristol have now suggested an answer. They noted that Eciton army ant species that fed exclusively on other ants lacked submajors. Submajors, they found, proved better than regular workers at transporting prey, both as individuals and in teams. Their long legs enable them to carry awkwardly-shaped prey with less friction with the ground. So submajors “can be seen ultimately as a cost of expanding out of the ancestral feeding niche,” the study authors concluded.
Parasite mind control
The hairworm parasite Sphinochordodes tellinii, it seems, has Machiavelli written into its DNA. It spends part of its life inside the grasshopper Meconema thalassinum, and induces bizarre behaviour in its host. Parasite-carrying grasshoppers are known to actively seek, and jump into, bodies of water. This enables the parasite to emerge from its host to complete the last leg of its life cycle-adulthood and breeding.
French and British researchers have now shed light on the parasite’s machinations. They looked at the two organisms’ proteomes-the smorgasbord of proteins produced by both. Several of the hairworm’s proteins, they found, are similar to ones found in the grasshopper and other insects. So the parasite’s manipulation of its host is a case of molecular mimicry, they concluded. The hairworm releases potent concentrations of these proteins, directly affecting the development and workings of the grasshopper’s central nervous system, causing them to seek water.
-Mike Ghenu
Source: Proceedings of the Royal Society B
