New study by St. Olaf researchers published in flagship biological journal
New findings by a team of St. Olaf College researchers about the way that temperature impacts signal preferences between species has been published in The Royal Society’s flagship biological research journal Proceedings of the Royal Society B.
The team, supervised by St. Olaf College Associate Professor of Biology Norman Lee, posed a simple question: If cricket songs change with temperature, can the acoustic parasitoid fly Ormia ochracea maintain their ability to recognize suitable host crickets?
The study, co-led by Kari Jirik ’20 and Post-Baccalaureate Research Associate Jimena Dominguez, both members of the Lee Lab of Neural Systems and Behavior at St. Olaf College, have found that Ormia ochracea exhibit song temporal pattern preferences that change with ambient temperature in a way that parallels how ambient temperature affects the temporal features of cricket songs. This study is the first to describe in detail temperature-coupling between song features of a signaler and the song preferences of an unintended eavesdropping receiver.
“Since the pulse rate of cricket calling songs change when ambient temperature changes, we found that the pulse rate preferences of Ormia ochracea also shifted with ambient temperature,” says Dominguez.
Along with other members of the Lee Lab, the research team described cricket song pulse rate preferences in Ormia ochracea by using a high-speed spherical treadmill system to record walking phonotactic responses to calling songs that varied in pulse rates under different ambient temperatures. At a room temperature of 21℃ flies walked optimally to cricket songs with a pulse rate of 50 pulses per second, and walked less to cricket songs with higher or lower pulse rates. This peak of their pulse rate preference function shifted to a higher pulse rate (70 pulses per second) at 30℃. In addition to the shift in the peak of the pulse rate preference function, the team also found that flies became less selective and responded more readily to a wider range of pulse rates.
“Our results are cool because it introduces a new possibility of eavesdropping flies being able to recognize their host cricket songs across a wide range of temperatures, allowing gravid females to find host crickets even when the temperature fluctuates,” says Dominguez.
“Our results are cool because it introduces a new possibility of eavesdropping flies being able to recognize their host cricket songs across a wide range of temperatures, allowing gravid females to find host crickets even when the temperature fluctuates.”
Jimena Dominguez
As the rhythmic production of sound pulses in calling songs change with temperature, temperature-coupling of song preferences would be important for maintaining effective communication between male and female crickets of the same species. This is especially the case when the ambient temperature drops at dusk, during peak hours of acoustic communication among crickets.
“The temperature coupling of male signal features and female preferences for those features was thought to be possible because male and female crickets are genetically related and genetically coupled. Genetic coupling might allow for a common genetic basis underlying signal production and signal preferences,” says Lee, the senior author. Temperature coupling in the absence of genetic coupling may occur if temperature affects cellular and metabolic processes in the same way in signalers and receivers. The precise mechanisms of how signal preferences and signal recognition change with temperature is currently unknown and warrants further investigation in future studies.
This current study is part of a larger effort funded by a U.S. National Science Foundation CAREER grant awarded to Lee to determine cricket calling song features that Ormia ochracea evaluate to recognize appropriate host species. Across the southern U.S., the Hawaiian Islands, and in Mexico, different populations of Ormia ochracea utilize different host cricket species that produce songs differing in the temporal patterning of sound pulses. Acoustic communication signals across the animal kingdom share the common feature of being temporally patterned, and receivers of these signals are tasked with making sense of information that may be encoded in the temporal structure. Understanding the basis of song pattern recognition in Ormia ochracea may provide valuable insights into fundamental principles involved in recognizing this information in communication signals.