Hearing in Cichlid Fishes under Noise Conditions

Abstract

BackgroundHearing thresholds of fishes are typically acquired under laboratory conditions. This does not reflect the situation in natural habitats, where ambient noise may mask their hearing sensitivities. In the current study we investigate hearing in terms of sound pressure (SPL) and particle acceleration levels (PAL) of two cichlid species within the naturally occurring range of noise levels. This enabled us to determine whether species with and without hearing specializations are differently affected by noise.Methodology/Principal FindingsWe investigated auditory sensitivities in the orange chromide Etroplus maculatus, which possesses anterior swim bladder extensions, and the slender lionhead cichlid Steatocranus tinanti, in which the swim bladder is much smaller and lacks extensions. E. maculatus was tested between 0.2 and 3kHz and S. tinanti between 0.1 and 0.5 kHz using the auditory evoked potential (AEP) recording technique. In both species, SPL and PAL audiograms were determined in the presence of quiet laboratory conditions (baseline) and continuous white noise of 110 and 130 dB RMS. Baseline thresholds showed greatest hearing sensitivity around 0.5 kHz (SPL) and 0.2 kHz (PAL) in E. maculatus and 0.2 kHz in S. tinanti. White noise of 110 dB elevated the thresholds by 0–11 dB (SPL) and 7–11 dB (PAL) in E. maculatus and by 1–2 dB (SPL) and by 1–4 dB (PAL) in S. tinanti. White noise of 130 dB elevated hearing thresholds by 13–29 dB (SPL) and 26–32 dB (PAL) in E. maculatus and 6–16 dB (SPL) and 6–19 dB (PAL) in S. tinanti.ConclusionsOur data showed for the first time for SPL and PAL thresholds that the specialized species was masked by different noise regimes at almost all frequencies, whereas the non-specialized species was much less affected. This indicates that noise can limit sound detection and acoustic orientation differently within a single fish family.

A unique swim bladder-inner ear connection in a teleost fish revealed by a combined high-resolution microtomographic and three-dimensional histological study

“…On the one hand, the morphological specializations in E. maculatus may function to increase auditory sensitivities and expand hearing bandwidth, as shown in previous studies [15,34]. On the other hand, they could also serve to improve other aspects of hearing, such as frequency selectivity (see the above mentioned Chilata example), directional hearing or the vestibular sense and, thus, maneuverability of fish.…”

Hearing capacities and otolith size in two ophidiiform species (Ophidion rocheiandCarapus acus)

“…Natural abiotic and biotic sounds as well as anthropogenic sounds are very abundant in underwater environments (Slabbekoorn et al, 2010;Ladich and Schulz-Mirbach, 2013). Animal sound sources mainly result from invertebrates (Fish, 1964;Cato, 1993), marine mammals (Fish, 1964;Cato, 1993) and fishes (Fish, 1964;Steinberg et al, 1965;Myrberg, 1981;Ladich et al, 2006).…”

“…Interestingly, many fishes evolved a simple way for enhancing their auditory sensitivity: they displaced or extended the anterior part of the swimbladder toward the otic capsule (Coombs and Popper, 1979;Ramcharitar et al, 2006a;Braun and Grande, 2008;Parmentier et al, 2011a;Parmentier et al, 2011b;Ladich and Schulz-Mirbach, 2013), improving sound transmission from gas bubbles to the inner ear (see Popper and Fay, 1999;Ladich and Wysocki, 2003). Otophysans (catfish, carp, piranhas and relatives) have developed a specialized hearing structure called the Weberian apparatus (Evans, 1925;Ladich and Wysocki, 2003;Braun and Grande, 2008;Lechner and Ladich, 2008).…”

Changes in the acoustic environment alter the foraging and sheltering behaviour of the cichlid Amititlania nigrofasciata

“…The hearing capabilities of our study species, convict cichlids, have not yet been defined. However, the cichlid family contains species whose hearing is mainly based on particle motion and species whose hearing is mainly based on sound pressure (Ladich and Schulz-Mirbach, 2013;Yan and Popper, 1992). The noise stimuli experienced by the fish will differ from the original ferry recording as tank-based acoustics are complex and occur within the near-field.…”