Redescription of the Advertisement Call of Five Species of <i>Thoropa</i> (Anura, Cycloramphidae), Including Recordings of Rare and Endangered Species

<div><p>Frogs of the genus <i>Thoropa</i> comprise six endemic Brazilian species on the Eastern side of the country. Little is known about their natural history, especially about their acoustic communication. Therefore, aiming to provide an overview of their vocalizations, we analyzed and redescribed male advertisement calls of three living and two possibly extinct species. The smaller species, <i>T</i>. <i>petropolitana</i> and <i>T</i>. <i>lutzi</i>, produce simple calls (one single note) with a higher frequency range than the remaining larger ones. On the other hand, the larger species present complex calls, with more than one note: <i>T</i>. <i>megatympanum</i> calls have three notes, <i>T</i>. <i>taophora</i> calls have four notes, and <i>T</i>. <i>miliaris</i> calls varies from three to six notes. Population snout-vent length negatively correlated with peak of dominant frequency as expected. However, highlighted differences between two populations of <i>T</i>. <i>lutzi</i>, which could indicate need of further taxonomic evaluation of those lineages. Peculiar morphology, such as the absence of vocal sacs and slits, may have contributed to their call variation and highly banded frequency structure. If the observed population differences reflect species-level differences, <i>T</i>. <i>lutzi</i> may be classified as a critically endangered species, as <i>T</i>. <i>petropolitana</i>. Furthermore, we provided a suggestion to an unusual behavior in frogs: calling with the mouth open in the smaller species of the genus.</p></div

Linear regression between <i>Thoropa</i> snout-vent length (SVL) and peak of dominant frequency.

<p>Horizontal bars represent the SVL range and verticals lines represent the dominant frequency range.</p

Advertisement call parameters and size of species of genus <i>Thoropa</i>.

<p>Values presented as mean ± standard deviation (range; sample size). When only one value is presented the number of calls is equal to 1. Two populations of <i>T</i>. <i>lutzi</i> are present, one from the state of Minas Gerais and another from the type locality in the state of Rio de Janeiro.</p

Equipment and sound analyses settings used for the recordings of six populations of five <i>Thoropa</i> species. n/a = data not available.

<p>Equipment and sound analyses settings used for the recordings of six populations of five <i>Thoropa</i> species. n/a = data not available.</p

Spectrogram (above) and oscillogram (below) of the advertisement calls of five species of <i>Thoropa</i>.

<p>(A) Advertisement calls of <i>T</i>. <i>lutzi</i> from the state of Minas Gerais; (B) <i>T</i>. <i>lutzi</i> from the type locality in the state of Rio de Janeiro; (C) <i>T</i>. <i>petropolitana</i> from state of Rio de Janeiro; (D) <i>T</i>. <i>megatympanum</i> from the state of Minas Gerais; (E) <i>T</i>. <i>taophora</i> from the state of São Paulo; and (F) <i>T</i>. <i>miliaris</i> from the type locality in the state of Rio de Janeiro.</p

Conservation status of the species of the genus <i>Thoropa</i> in accordance to distinct sources.

<p>The IUCN Red List of Threatened Species [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0162617#pone.0162617.ref029" target="_blank">29</a>], Brazilian official red list [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0162617#pone.0162617.ref032" target="_blank">32</a>], and red lists of the state of Espírito Santo (ES) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0162617#pone.0162617.ref034" target="_blank">34</a>], Minas Gerais (MG) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0162617#pone.0162617.ref035" target="_blank">35</a>], Rio de Janeiro (RJ) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0162617#pone.0162617.ref031" target="_blank">31</a>], Rio Grande do Sul (RS) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0162617#pone.0162617.ref033" target="_blank">33</a>], and São Paulo (SP) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0162617#pone.0162617.ref036" target="_blank">36</a>]. Categories are least concern (LC); near threatened (NT); vulnerable (VU); endangered (EN); critically endangered (CR); data deficient (DD); and not evaluated (NE).</p