Thursday, July 30, 2009

How Cricket Studies at a Field Station Inspired Next
Generation Directional Hearing Aids

Dr. Oliver Beckers, University of Nebraska, a post-doctoral student in Dr. William Wagner's lab at the University of Nebraska, is working at Hastings and elsewhere in California. Oliver is doing a interesting research project on the flies that spray sticky larva near singing crickets. The female comes into see the robust singing male, but might become attached to one of the larvae of this parasitic fly as it approaches the male. So, the male might try fooling the parasite by singing cryptically so the fly won't know where to spray the larvae. But then, the females may not think highly of his song and fail to approach for mating. Alas. The struggle between what Darwin called "sexual selection" (females choosing males for some attractive characteristic like long songs, large antlers, colorful feathers, etc.) and natural selection (environment, including parasites, weather, volcanoes, etc. which influences how many young any individual gets into the next generation). The male crickets work hard to make a great song that attracts the females and, dang it, they attract a deadly parasite. That is, sex is killing them! Oliver gave a great talk today; same title. We learned that crickets have ears on their legs (photos), and other ears along their sides. They are very sensitive to sounds. (see photos). These are nothing like the ears in the fly though.
About 30 years ago, a UTA (Univ. Texas Austin) graduate student in Zoology, named Bill Cade (who has gone on from being an important researcher in behavioral genetics, to the presidency of Lethridge University in Canada), made the apparently irrelevant discovery at a Texas biological field station that field crickets are parasitized by a inconspicuous parasitic fly, Ormia ochracea. This same fly is present at Hastings, and is a parasite on our common field cricket, Gryllus lineaticepts. Most flies can't hear, but this fly has incredible directional hearing for such a small animal. It was an important entomological discovery, ’acoustic parasitism’ and launched many interesting studies related to parasite-host relationships. Among the studies that Cade's discovery inspired were those of Ron Hoy, Cornell University, starting in 1991, in which a team at Cornell University, set out to discover what kind of ’ears’ the fly uses to detect and localize the singing cricket. They discovered that the Ormia fly possesses a hearing organ unlike any other in nature. One of Hoy’s colleagues is a mechanical engineer and he and his colleagues have come up with an entirely novel design for micro-miniature directional microphones. These microphones operate on the principle of the fly's ears and are fabricated using cutting-edge nanofabrication techniques at Cornell. These microphones will be the basis for the next generation of hearing aids that will incorporate directional sensitivity to suppress unwanted noise from conversational sounds. The NIH has recently allocated nearly $7 million dollars to develop these fly-inspired microphones.

Ears on leg; photo and drawing. Parasitic fly on cricket.