Physalaemus centralis Bokermann, 1962

Hepp, Fábio & Pombal, José P., 2020, Review of bioacoustical traits in the genus Physalaemus Fitzinger, 1826 (Anura: Leptodactylidae: Leiuperinae), Zootaxa 4725 (1), pp. 1-106 : 63

Physalaemus centralis Bokermann, 1962

We found a single call type for the species, referred to as call A. The call is composed of single harmonic note with a very low fundamental frequency. Frequency modulations are subtle (20 Hz), still the call has a general downward FM, with an up-downward FM segment in the first third of the call duration.

Call A ( Fig. 31 A–E and 24H). We examined 16 recordings, a total of 36 minutes, with ca. 1880 calls from 25 males. Only some of these calls were measured (see Table 2 ). Call duration varies from 0.404 to 0.550 s. The call rise is much longer than call fall. Call rise has a short gradual increase followed by a long exponential part ( Fig. 31C ). In some calls the rise remains with very low amplitude until the limit with the sustain, where the amplitude increases abruptly ( Fig. 31A ). The sustain is regular, slightly decreasing towards the end of the call. The call fall is proportionally short and with logarithmic shape. The amplitude peak is at around the middle of the call duration. The envelope varies from elliptic ( Fig. 31C ) to almost rectangular (in calls in which the rise is not gradual; Fig. 31A ). More than 50 % of the call energy is concentrated in 25 % of the call duration around the amplitude peak. There is no PAM in the call. The call has a harmonic series ( Fig. 24H ). However, due to the low fundamental frequency (see below), the wave peaks are shown as pulses in audiospectrograms at broad filter bandwidth (e.g., above 100 Hz; Fig. 31E ). The bands are observed in audiospectrograms at narrow filter bandwidth (e.g., below 90 Hz; Fig. 31B, D ). The fundamental frequency is ca. 90 Hz. This band and the next harmonic are generally absent in audiospectrograms. There are ca. 20 emphasized harmonics. The wave periods are regular and harmonics clear throughout the call. The dominant frequency varies from ca. 1410 to 1500 Hz ( Fig. 31B ). The dominant harmonic varies from the fourth to the 21 st, but it is usually between the 15 th and 18 th. There is a clear shift in the relative energy among bands; the dominant frequency gets higher toward the end of the call, starting at the fourth, fifth or sixth harmonic and ending at the 15 th, 19 th, 20 th, or 21 st ( Fig. 24H , 31B, D ). Most of the call energy is between 600 and 1650 Hz (eight to twelve harmonics). Frequency modulations are subtle and better perceptible in audiospectrograms with wide filter band- widths (e.g., Fig. 31E ). The call has a general downward FM. Additionally, the calls have an up-downward FM in the first third of the call duration, yielding arc-shaped bands in this part of the call, and a short downward FM at the end ( Fig. 31B, D ). The general downward FM and the initial up-downward FM result in S-shaped harmonics when considering the entire call. There is no PFM.

Figures

FIGURE 24. Multiplicity relationship between “instantaneous” dominant frequency and w of calls A of eight Physalaemus species. Each graph shows a single call A of P. henselii (A), P. albonotatus (B), P. cuqui (C), P. atim (D), P. albifrons (E), P. erikae (F), P. kroyeri (G), P. centralis (H). Grid corresponds to the harmonic values (right y-axis). Red squares are the values of “instantaneous” dominant frequency; blue circles are the values of the reciprocal of w; green triangles are the factor values of the ratio “instantaneous” dominant frequency / w reciprocal per delta time. Delta time corresponds to the duration of one period of the measured acoustic oscillation. Note that factors around integer values suggest harmonic relationship between the frequency calculated (w reciprocal) and the dominant frequency. The heterogeneity of the factors in P. henselii (A) suggests sidebands.

FIGURE 31. Call A of Physalaemus centralis. Oscillograms (A and C) and audiospectrograms (B, D, and E). A single typical call (A–B). A variant call with a different envelope (C).Audiospectrograms with apparent bands at a narrow filter (B) and bands not visible at wide filter (D; see filter values below). Sequence with three calls (E); note the frequency modulations (see text). Horizontal scale bars have 0.1 s (C and D) and 0.5 s (E); vertical scale bars have 1 kHz (D) and 0.5 kHz (E). Filter bandwidth (Hz): 34.5 (B and E); 135 (D).