Effects of temperature on the song parameters of the Moroccan bushcricket Eugaster spinulosa (Orthoptera, Tettigoniidae)

Abstract

Acoustic signals are important for inter- and intraspecific interactions in many species. Their information potential depends largely on species characteristics. Here we describe quantitatively the song of Eugaster spinulosa (Johannson 1763), (Orthoptera, Tettigoniidae) and analyse the relationships of song parameters with temperature. To the best of our knowledge there are no previous descriptions available of the song of any species in the genus. Songs of seven males from the mountains of Jebilet, Marrakech (Morocco), were recorded in a semi-anechoic chamber for 105 days. Using automated thermal tables, individuals were exposed to a daily cycle of temperatures between 17.5 and 41.5°C. The calling song of Eugaster spinulosa is broader in frequency (2–28 kHz) than the song of other tettigoniids. It consists of extended series of separately audible echemes, which are polysyllabic and comprise a variable number of broadband syllables, usually between 5 and 10. The stridulatory activity of Eugaster spinulosa showed a wide thermal plasticity (ranging over 24°C between thermal thresholds). In addition to changes in temporal features, we found that an increase in temperature reduced the number of syllables per echeme.