Heeding the hormonal call

An enduring question in evolutionary biology is: How optimized are organisms for their environment? This question is perhaps best addressed in the field of sensory biology. It is straightforward to specify both sensory stimuli--such as species-specific communication signals, signals from predator or prey, or noise--and the transmission properties of the environment. Furthermore, it is easy to measure the ability of an animal's sensory system to pick up these signals. Some sensory receptors are sharply tuned to particularly potent signals, whereas others are broadly sensitive to the total array of signals encountered. Of particular interest are examples of apparent mismatches between communication signals and the sensitivity of the receptors receiving them. Could it be that an appropriate well-matched signal has not yet been found? Are the sensory receptors optimally tuned to a different signal that belongs to the evolutionary past? Is the mismatch exploited during, for example, the selection of a mate? Or, is the mismatch a reflection of the dynamic nature of matching between communication signals and sensory systems--that is, does the matching between sender and receiver change depending on the stage of the life cycle or environmental conditions? The answer is provided by Sisneros and colleagues on Science. 2004 Jul 16;305(5682):349-50., who chose as their subject the plainfin midshipman (Porichthys notatus), a nocturnal fish that inhabits Pacific coastal waters. These investigators resolve the apparent mismatch between a vocal mating signal emitted by the male fish and the sensitivity of the female's auditory system by demonstrating that steroid reproductive hormones increase the sensitivity of the female's auditory system to the male's courtship calls. (from Zakon H.)