A new connection: Enhanced hearing ability in the New Zealand bigeye, Pempheris adspersa.

Abstract

Recently the bigeye, Pempheris adspersa, has been found to be one of the few sound producing fish found in the temperate marine waters of New Zealand. An initial crude morphological examination of this species found a special connection, analogous to that of the well-defined laterophysic connection, between the otic capsule and the lateral line recess. The aim of the present study was to characterize the hearing ability of the bigeye using auditory evoked potentials, understand the role of this special connection, and describe the morphology of the hearing structures using microCT and MRI techniques. The novel connection consists of a robust ligament directly connecting the otic capsule to the lateral recess, with the swim bladder running directly posterior to the ligament. Pempheris adspersa could hear in the frequency range 100–1000 Hz, with greatest sensitivity between 100–800 Hz. Cutting the connecting ligament resulted in a 15–20 dB threshold shift, with a further 5–10 dB shift after swim bladder puncture. This connection represents a completely novel hearing specialization and shows that the lateral line is directly connected to the otic capsule, enhancing the hearing ability of this species especially at low frequencies (100–200 Hz).

Pressure and particle motion detection thresholds in fish: a re-examination of salient auditory cues in teleosts

“…Severing the specialised hearing connection in the bigeye increases their hearing sensitivity by 15-20dB re. 1Pa (Radford et al, 2011). Our current study in conjunction with this previous research provides further evidence that it is the presence and the ability of the ancillary hearing structures to convey pressure sensitivity to the inner ear that differentiates the hearing ability of different species of fish.…”

“…The triplefin has no swim bladder so theoretically has no capability to detect a pressure stimulus, and this was represented in their pressure hearing sensitivity by their being the least sensitive of the three species examined. The two other species tested in the present study have ancillary hearing structures; Weberian ossicles for the goldfish (Von Frisch, 1938;Fay and Popper, 1974) and an otolaterophysic connection for the bigeye (Radford et al, 2011). It has been shown that as the Weberian ossicles develop in the zebrafish (Danio rerio) and connect the inner ear to the swim bladder, the hearing range increases from 1000 to 4000Hz and the fish become more sensitive to sound (Higgs et al, 2002).…”

“…Since then, shaker table technology has been used for other species (Edds-Walton and Fay, 1998;Weeg et al, 2002;Edds-Walton and Fay, 2003;Edds-Walton and Fay, 2005;Lu et al, 2010), not only to measure the axis of particle motion but also to describe how auditory signals are encoded in individual afferent fibres of the auditory nerve. Therefore, the aim of the present study was to: (1) describe the use of the AEP technique in association with a shaker table to measure particle acceleration thresholds in three species of fish with different hearing structures -triplefin (Forsterygian lappillum, Hardy 1989), which has no swim bladder (Montgomery et al, 2006); Carassius auratus (Linnaeus 1758), which like all cyprinids has Weberian ossicles (Von Frisch, 1938); and the New Zealand bigeye (Pempheris adspersa, Griffin 1927), which has a hearing specialisation connecting the swim bladder to the inner ear (Radford et al, 2011); (2) compare the abovementioned different ways for determining particle acceleration thresholds (shaker table, pressure differences between two hydrophones, and accelerometers); and (3) compare particle acceleration thresholds to pressure thresholds to better separate each aspect of underwater sound for acoustic detection.…”