Saccular potentials of the vocal plainfin midshipman fish, Porichthys notatus

Abstract

The plainfin midshipman fish, Porichthys notatus, is a vocal species of teleost fish that generates acoustic signals for intraspecific communication during social and reproductive behaviors. All adult morphs (females and males) produce single short duration grunts important for agonistic encounters, but only nesting males produce trains of grunts and growls in agonistic contexts and long duration multiharmonic advertisement calls to attract gravid females for spawning. The midshipman fish uses the saccule as the main acoustic endorgan for hearing to detect and locate vocalizing conspecifics. Here, I examined the response properties of evoked potentials from the midshipman saccule to determine the frequency response and auditory threshold sensitivity of saccular hair cells to behaviorally-relevant single tone stimuli. Saccular potentials were recorded from the rostral, medial and caudal regions of the saccule while sound was presented by an underwater speaker. Saccular potentials of the midshipman, like other teleosts, were evoked greatest at a frequency that was twice the stimulus frequency. Results indicate that midshipman saccular hair cells of non-reproductive adults had a peak frequency sensitivity that ranged from 75 (lowest frequency tested) to 145 Hz and were best suited to detect the low frequency components (≤105 Hz) of midshipman vocalizations.

Early Development of Hearing in Zebrafish

“…As shown in this paper, microphonic potentials can be robustly recorded from zebrafish of 2 to 7 dpf. Like microphonic responses that were previously reported in adult and juvenile fish and amphibians, microphonic waveforms recorded from the inner ear of zebrafish embryos/larvae have a characteristic feature of doubling the stimulus frequency, due to groups of hair cells in the inner ear that are oriented opposing to or opposite each other (Flock 1965;Furukawa et al 1972;Fay and Popper 1974;Corey and Hudspeth 1983;Sisneros 2007), making them distinguishable from stimulus artifact or background noise. Results of this study demonstrate that microphonic recording can be a quick and reliable physiological method to assess a difference in auditory function between control zebrafish and morphants/mutants during the first week of development.…”

“…Behavioral methods such as classical conditioning and food reward measure overall hearing ability of entire animals Cervi et al 2012). Electrophysiological methods such as auditory brainstem recording and microphonic potential recording measure function of a portion of the auditory system (Kenyon et al 1998;Lu and Tomchik 2002;Lu and Xu 2002;Sisneros 2007). The development of auditory function has been studied in several fish species that are juveniles and adults with a body length greater than 10 mm (Kenyon 1996;Higgs et al 2002Higgs et al , 2003Alderks and Sisneros 2011).…”

Seasonal plasticity of auditory saccular sensitivity in “sneaker” type II male plainfin midshipman fish, Porichthys notatus

“…The procedures for exposing and recording from the inner ear saccule followed those used in previous studies (Sisneros 2007(Sisneros , 2009bAlderks and Sisneros 2011). Briefly, animals were initially anesthetized in a 0.025% ethyl-p-aminobenzoate/saltwater bath until the fish's opercula ceased movement for at least 5 min.…”

“…The output of the lock-in amplifier reflects the relative amplitude of the inner ear saccule's hair cell response to a tonal stimulus. Because the opposing hair cell orientations within the saccular sensory maculae result in a double-frequency response, the saccular potential is defined here as the amplitude the hair cell response at the second harmonic of the stimulus (Cohen and Winn 1967;Sisneros 2007). …”

“…Recently Popper and Fay (2011) proposed that all future fish hearing studies should independently characterize particle motion and sound pressure sensitivities of fish regardless of any hearing specializations that fish may possess (e.g., accessory hearing structures such as Weberian ossicles that connect the swim bladder to the inner ear). Previous auditory physiology studies of the plainfin midshipman fish have primarily reported auditory responses with regard only to sound pressure Bass 1999, 2001;Sisneros et al 2004;Bass 2003, 2005;Sisneros 2007Sisneros , 2009bAlderks and Sisneros 2011;Rohmann and Bass 2011; but for the exception see Weeg et al 2002). Thus, better characterization of particle motion sensitivity in this species and across the different sexual phenotypes is warranted.…”