Bioacoustics of Isophya gulae

Morphological description : Peshev 1981. Karyotype : Warchałowska-Śliwa et al. 2008. Supplement to the description and diagnosis : Male pronotum is clearly widened and elevated in metazone with slightly sinuated lateral hind margins but never saddle-shaped as in I. obtusa . Male tegmina ( Fig. 52 ) are moderalety uplifted, less shortened than in I. obtusa and not wider than the width of metazone; their venation is sharp. CuP is slightly widened and moderately approximated to CuA. The stridulatory file ( Fig. 177 A) is about 3.2–3.4 mm long and has 108–128 teeth (2 33). Female tegmina ( Fig. 76 ) are slightly blunt apically and have reticulate venation. Ventral keels of hind femora lack spines or have a single spine. Male cerci ( Figs 101 , 177 B) are moderately tapering apically and have stong pointed tooth subapically. The body colouration is green, sometimes darkened but not violet as in I. obtusa . Male tegmina have brownish disc getting dark green or brownish-green towards the apical area, contrasting with the body colour. The song ( Fig. 187 ) consists of isolated syllables or, sometimes, two sillables arranged at an interval of 3–6 seconds (usually syllables of an individual follow at intervals of 20–60 s). The syllables may have two parts: main part of dense impulses lasting 100–200 ms and additional part of 4–20 sparse impulses (after-clicks). Sometimes, especially in recently moulted males, the syllables (or the first of two grouped syllables) contain only the first part. Both parts are separated by a long silent interval and thus the total duration of the syllable is 1400–2500 ms (or less at T>25ºC). Bioacoustics : The syllable consists of a decrescending main (first) and an additional (second) part. Studied specimens started sing about a week after moulting. Male song at 20–21ºC had a total length of 1687–1991 ms (mean 1854±85; n=15). First part of the syllable lasted 106–159 ms (mean 142±10; n=24) and had 38–46 impulses (mean 42±3; n=24) with impulse period of 2–10 (usually 3–7) ms (mean 3.5±0.3; n=1005). Second part lasted 56– 171 ms (mean 106±28; n=15) and included 4–10 impulses (mean 6±2; n=15) with highly wariable impulse period raging from 2 to 50 ms. The interval between 1st and 2nd part lasted 1425–1728 ms (mean 1605±85; n=15). Temperature and age influenced the song. Higher temperatures influenced mostly the main syllable part and the interval between two parts by reducing their duration, while older individuals showed longer second part with higher number of impulses (up to 20) and a longer period between them (up to 80 ms) and thus the song at 21ºC became longer than 2 s. Females responded either to a neighbouring acoustically active male or to a played recording of a conspecific male. Female song (see marker on Fig. 187 ) included short “click” that usually contained a high-amplitude impulse followed by few low-amplitude ones that altogether lasted 60–80 ms (20–23ºC). The song was produced after the end of male syllable and thus the possible trigger for the female answer appears to be the second part of the male syllable. Thus, the matured males may be preferred against the recently moulted ones, the latter still having weakly developed second syllable part or even lacking it in some syllables. Yet, it is difficult to judge whether the female synchronizes her call with the beginning or the end of the male after-clicks. In any case, measuring the distance from the end of male call may be problematic due to its fading towards the null position of the tegmina. The measured intervals between the first after-click of the second part of male syllable and female answer at 21ºC lasted 322–545 ms (mean 432±56; n=36), and between the last detectable after-click and female answer—100–321 ms (mean 165±50; n=36). At 23ºC these values were 388–459 and 144–287 ms, respectively.