Category Archives: dimorphism

On Male Versus Female (bugs)

Male fruitflies know what their ladies like. They court them with the dulcet tones of their wings themselves. It has been observed that one behavior that males of the species Drosophila Melanogaster can engage in that appears to increase his likelyhood of copulating with a female, is the rhythmic production of sound by wing-vibration; that is if she finds his performance to be sufficiently virtuosic. This behavior is controlled by a central pattern generator (CPG), a group of neurons that, more or less, independently generates the activity corresponding to this motion. Think of this as a sort of reflex, somewhat akin to walking at a constant pace over a completely flat surface in that it is extremely stereotyped and largely automatic.

Nature Magazine

One question this has raised in researchers minds is why this behavior is limited to males. A new study demonstrates that the females have this ability, but they simply suppress it. Apparently the neurons that kickstart the motor of the central pattern generator are simply not active in females. In order to get these cells going, Jai Y. Yu and Barry J. Dickson used a technique involving the manipulation of ion channels with light.

Every neuron’s excitability is mediated by the opening and closing of small pores (ion channels) in their membranes which allow charged ions to flow in and out. The regulation of this permeability or conductivity of the membrane determines how excited the neuron can become. Put another way, if a bunch of little doors burst open that allow positively charged ions to flow into the cell, those ions flood in, raising the voltage of the cell, putting it in an excited state. It turns out that certain species of algae have specialized ion channels that are of some use to scientists. Usually ion channels are opened in response to neurotransmitter or enzymatic signals, but these plants have ion channels that are directly “gated” (opened or closed) by impinging light. What Yo & Dickson have done is to exploit a technique in which they borrow these channels and put them into specific cells using molecular genetic techniques, thus allowing them to selectively excite specific ion channels in specific neurons with bursts of luminance.

In this way, they were able to observe that, through the excitation of neurons controlling the CPG, the ladies are able to produce these courtship songs as well, they just didn’t know they had it in them.