Evidence of auditory insensitivity to vocalization frequencies in two frogs

Abstract

The emergence and maintenance of animal communication systems requires the co-evolution of signal and receiver. Frogs and toads rely heavily on acoustic communication for coordinating reproduction and typically have ears tuned to the dominant frequency of their vocalizations, allowing discrimination from background noise and heterospecific calls. However, we present here evidence that two anurans, Brachycephalus ephippium and B. pitanga, are insensitive to the sound of their own calls. Both species produce advertisement calls outside their hearing sensitivity range and their inner ears are partly undeveloped, which accounts for their lack of high-frequency sensitivity. If unheard by the intended receivers, calls are not beneficial to the emitter and should be selected against because of the costs associated with signal production. We suggest that protection against predators conferred by their high toxicity might help to explain why calling has not yet disappeared, and that visual communication may have replaced auditory in these colourful, diurnal frogs.

Peer Review #2 of "Advertisement call of Brachycephalus albolineatus (Anura: Brachycephalidae) (v0.2)"

“…hermogenesi (Verdade et al 2008), B. pitanga (Araújo et al 2012, Tandel et al 2014, Goutte et al 2017, B. tridactylus (Garey et al 2012), B. crispus (Condez et al 2014), B. sulfuratus (Condez et al 2016), and B. darkside (Guimarães et al 2017).…”

“…Call descriptions of the species are scarce, which is surprising, given that individuals of the species are usually located by their calls, often emitted at locally high male densities (one person might hear dozens of males from a single hearing spot). Advertisement calls were described for B. ephippium (Pombal Jr., Sazima & Haddad 1994, Goutte et al 2017, B.…”

Evolution of treefrogs' calls in tropical islands might be under directional selection

“…In general, the frog ear is anatomically composed by two regions: the inner ear, where the amphibian and basilar papillae sits, and the middle ear, generally containing a tympanum (Van Dijk et al, 2011). The amphibian papilla is composed by a patch of epithelium covered by hair cells that is responsible for lower and mid frequencies perception (Purgue & Narins, 2000;Goutte et al, 2017), while the basilar papilla is structurally simpler and responsible for higher frequencies perception (Narins & Capranica, 1980;Van Dijk et al, 2011). The tympanic membrane is coupled to capsule via extrastapes and stapes and serve to transmit vibrations from surrounding air to the inner ear (Van Dijk et al, 2011).…”

Redescription of the advertisement call of Brachycephalus tridactylus (Anura: Brachycephalidae)

“…In the last decade, intensified fieldwork has led to the description of 23 species (Frost 2018), but data on natural history lag behind the rate of new species descriptions. Advertisement calls have been described for 12 of 36 species (33%): B. actaeus Haddad, 2018 (Monteiro et al 2018a); B. ephippium (Spix, 1824) (Pombal et al 1994, Goutte et al 2017; B. albolineatus Bornschein, Ribeiro, Blackburn, Stanley, andPie, 2016 (Bornschein et al 2018); B. crispus Condez, Clemente-Carvalho, Haddad, andReis, 2014 (Condez et al 2014); B. darkside Guimarães, Luz, Rocha, andFeio, 2017 (Guimarães et al 2017); B. hermogenesi (Giaretta and Sawaya, 1998) (Verdade et al 2008); B. mirissimus Pie, Ribeiro, Confetti, Nadaline, andBornschein, 2018 (Pie et al 2018); B. olivaceus Bornschein, Morato, Firkowski, Ribeiro andPie, 2015 (Monteiro et al 2018b); B. pitanga Alves, Sawaya, Reis, and Haddad, 2009(Araújo et al 2012, Tandel et al 2014, Goutte et al 2017; B. quiririensis Ribeiro, 2015 (Monteiro et al 2018b); B. sulfuratus Haddad, 2016 (Condez et al 2016); and B. tridactylus Garey, Lima, Hartmann, andHaddad, 2012 (Garey et al 2012).…”