Scientists found a bacteria tricked a wasp to get rid of its males Premium

Researchers from Shenyang Agricultural University (SAU), China, published a paper in the June 3 issue of the journal Current Biology showing that Wolbachia bacteria had manipulated the wasp Encarsia formosa to entirely get rid of its males.

A hundred years ago, two American researchers named Marshall Hertig and Simeon Burt Wolbach discovered that mosquitoes harboured bacteria within their cells. Other researchers later found similar bacteria in the cells of most insects and many other arthropods. The genus to which the bacteria belonged was named Wolbachia.

Wolbachia bacteria are also present in insect eggs but they are absent in the sperm. This means females can transmit Wolbachia to their offspring whereas males can’t — from the bacteria’s point of view, an evolutionary dead-end. As a result, Wolbachia have evolved ways to manipulate their insect hosts to produce more female than male progeny.

A new study reports that the bacteria may have taken it a bit too far this time. Researchers from Shenyang Agricultural University (SAU), China, published a paper in the June 3 issue of the journal Current Biology showing that Wolbachia bacteria had manipulated the wasp Encarsia formosa to entirely get rid of its males.

E. formosa wasps are of interest to agricultural scientists because they provide an efficient way to control whiteflies. Whiteflies feed on the sap of plant leaves, causing productivity losses, and are thus a major agricultural pest. Whiteflies belong to the insect order Hemiptera whereas wasps belong to the insect order Hymenoptera. The wasp seeks out the nymphs (or larvae) of whiteflies and lays its eggs on them. When the eggs hatch, the larvae that emerge penetrate the nymph, feed on its tissues, grow to adulthood, and in the process kill the nymph.

The progeny wasps emerge from the nymph’s carcass. As a parasitoid of whiteflies, the female wasp is in effect a search and destroy weapon. The male wasps are superfluous to this role.

Generally, among hymenopterans such as ants, bees, and wasps, the eggs fertilised by sperm cells develop into females while unfertilised eggs develop into males. The males contain only one set of chromosomes, derived from the egg, and are thus said to be haploid. In contrast, the females are diploid because they contain two sets of chromosomes: one set derived from the egg and the other from the sperm.

The females use a specialised form of cell division called meiosis to transmit only one set of chromosomes to their eggs, while the males transmit their single chromosome set to all of their sperm by the more general cell-division process called mitosis. This, in a nutshell, is how haplo-diploid sex determination works.