Acoustic underwater signals with a probable function during competitive feeding in a tadpole

Abstract

Acoustic communication is widespread among adult stages of terrestrial animals and fish and has also been observed in insect larvae. We report underwater acoustic communication in the larvae of a frog, Gephyromantis azzurrae, from Isalo, a sandstone massif in western Madagascar. According to our field data, these tadpoles live in streams and prefer habitats characterized by comparatively low temperatures, shallow water depth, and a relatively fast current. Feeding experiments indicated that the tadpoles are carnivorous and macrophagous. They consumed insect larvae and, to a lesser extent, small shrimps, and conspecific as well as heterospecific tadpoles. Calls of these tadpoles consisted either of single click notes or of irregular series of various clicks. Some complex calls have a pulsed structure with three to nine indistinct energy pulses. Production of the pulses coincided with rapid closure of the jaw sheaths and often with an upward movement of the body. Calls were emitted while attacking prey and occurred significantly more often when attacking conspecifics. Tadpoles that had not been fed for some time emitted sounds more frequently than those that had been regularly fed. The spectral frequency of the calls differed in tadpole groups of different size and was higher in groups of smaller tadpoles, suggesting that spectral frequency carries some information about tadpole size which might be important during competitive feeding to assess size and strength of competitors. This report differs from those for the larvae of South American horned frogs, Ceratophrys ornata. These are the only other tadpoles for which sound production has reliably been reported but the calls of Ceratophrys tadpoles occur mainly in a defensive context.

Nidicolous tadpoles rather than direct development in Malagasy frogs of the genusGephyromantis

“…Some of these larvae are generalized tadpoles but the others appear to be carnivorous because of the presence of hypertrophied jaw sheaths. Carnivorous feeding as well as sound production has been demonstrated for the G. azzurae tadpole by Reeve et al (2011).…”

“…ambohitra, G. corvus and G. azzurae. The first three are generalized and the last two are carnivorous (see also Reeve et al 2011). These larvae will be described in more detail in forthcoming papers.…”

The use of bioacoustics in anuran taxonomy: theory, terminology, methods and recommendations for best practice

“…For instance, Reeve et al (2011) documented calls of a probable aggressive function during feeding in tadpoles of the Malagasy frog Gephyromantis azzurrae that fit into this category. The sound production mechanism of these immatures is unknown, but it is likely that sounds are produced with the respiratory system and thus qualify as vocalizations because tadpoles of G. azzurrae emit sounds during an opening and closing of the mouth (Reeve et al 2011). Also, juvenile spadefoot toads (Pelobates fuscus) emit feeding calls in the presence of prey, probably in the context of a general arousal (ten Hagen et al 2016).…”

Visual cues contribute to predator detection in anuran larvae

“…Anurans are unable to sense electric cues because they lack electroreceptors (Lannoo, 1999). Whether tadpoles exploit acoustic cues in predator detection is largely unexplored, although they do have a functional inner ear (Lannoo, 1999) and some species exhibit intraspecific acoustic communication (Natale et al ., 2011; Reeve et al ., 2011).…”