J Comp Physiol A (2007) 193:413–424
DOI 10.1007/s00359-006-0195-5ORIGINAL PAPER
Saccular potentials of the vocal plainWn midshipman Wsh,
Porichthys notatus
Joseph A. Sisneros
Received: 20 July 2006 / Revised: 10 November 2006 / Accepted: 12 November 2006 / Published online: 2 December 2006
 Springer-Verlag 2006
Abstract The plainWn midshipman Wsh, Porichthys
notatus, is a vocal species of teleost Wsh that generates
acoustic signals for intraspeciWc 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 spawn-
ing. The midshipman Wsh uses the saccule as the main
acoustic endorgan for hearing to detect and locate
vocalizing conspeciWcs. Here, I examined the response
properties of evoked potentials from the midshipman
saccule to determine the frequency response and audi-
tory 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 pre-
sented by an underwater speaker. Saccular potentials
of the midshipman, like other teleosts, were evoked
greatest at a frequency that was twice the stimulus fre-
quency. 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.
Keywords Auditory evoked potentials · Tuning ·
Hair cells · Hearing · Saccule
Introduction
Acoustic communication plays an important role in the
social and reproductive behaviors of vocal teleost
Wshes in the Family Batrachoididae (midshipman and
toad Wshes). The reproductive success of nocturnally
active batrachoidids is often greatly dependent on the
detection and localization of the conspeciWc vocal sig-
nals that are produced during intraspeciWc social com-
munication. A number of investigations have
characterized the vocal-acoustic behaviors and neuro-
biology of these Wshes establishing both the midship-
man and the toadWsh as important models for
identifying mechanisms of auditory reception, neural
encoding, and vocal production shared by all verte-
brates (Bass et al. 1999; Fay and Simmons 1999; Bass
and McKibben 2003).
One species of midshipman Wsh that has been the
subject of intensive neuroethological investigation with
regard to acoustic communication is the plainWn mid-
shipman Porichthys notatus. This vocalizing species of
midshipman generates acoustic signals for intraspeciWc
communication during social and reproductive behav-
iors. All adult morphs (females and males: types I and
II) produce single short duration grunts important for
agonistic encounters. However, only type I nesting
males produce trains of grunts and growls in agonistic
contexts and long duration (>1 min) multiharmonic
advertisement (mate) calls, known as “hums”, to
attract reproductively active females to their nests
(Bass et al. 1999). Females use the auditory sense to
J. A. Sisneros (&)
Department of Psychology, University of Washington,
Guthrie Hall, Box 351525, Seattle, WA 98195, USA
e-mail: sisneros@u.washington.edu
J. A. Sisneros
Virginia Merrill Bloedel Hearing Research Center,
University of Washington, Seattle, WA 98195, USA123

414 J Comp Physiol A (2007) 193:413–424detect and locate vocalizing males that produce the
multiharmonic hums during the breeding season.
Recent work shows that the frequency sensitivity of
auditory primary aVerents that innervate the inner ear’s
saccule, the main organ of hearing in midshipman,
changes seasonally with female reproductive state such
that summer reproductive females become better suited
than winter non-reproductive females to encode the
higher harmonic components of the male’s hum (Sisn-
eros and Bass 2003). Approximately 1 month before the
beginning of the summer spawning season, females show
peaks in circulating plasma levels of testosterone and
17
-estradiol (Sisneros et al. 2004a), which are now
known to induce the female’s reproductive auditory phe-
notype and enhance their sensitivity to the dominant
higher harmonic components of the male’s advertise-
ment call (Sisneros et al. 2004b). In addition, midship-
man-speciWc estrogen receptor alpha has been identiWed
in the saccule’s sensory epithelium which now provides
support for a direct steroid eVect on the inner ear (Sisn-
eros et al. 2004b). Thus, a prime candidate site where this
novel form of steroid-dependent auditory plasticity may
occur is at the level of the saccular hair cell receptor.
A Wrst step in the neurophysiological investigation of
midshipman auditory hair cells is to determine the
response properties of hair cells in the saccule. Toward
this end, the focus of this study was to determine the
frequency response properties of evoked potentials
from hair cells in the saccule of the midshipman Wsh.
Numerous studies have used the evoked potential
recording technique to determine the sensitivity and
response dynamics of inner ear hair cells in teleost
Wshes (Piper 1906; Adrian et al. 1938; Zotterman 1943;
Furukawa and Ishii 1967; Furukawa et al. 1972). This
recording technique was originally used in the plainWn
midshipman to establish that the saccule was the main
organ of hearing in this species (Cohen and Winn 1967).
Among teleost Wsh in general, saccular potentials are
easily identiWed because they are evoked at twice the
auditory stimulus frequency due to the presence of non-
linear and opposite oriented hair cell populations in the
Wsh saccule (Hama 1969; Furukawa and Ishii 1967; Fay
1974; Fay and Popper 1974). This double frequency
eVect of the evoked potentials was Wrst reported for the
lateral line organ of the ruV (Acerina cernua) where the
two groups of opposite oriented hair cells produce two
evoked potentials during every stimulus cycle (Jielof
et al. 1952; Flock 1965; Wersall and Flock 1965). In con-
trast to auditory end organs, the mammalian cochlea
and the crista ampullaris have hair cells that are ori-
ented in the same direction and hence have potentials
that are evoked at the same auditory stimulus fre-
quency (de Vries and Bleeker 1949; Tasaki et al. 1954).
The main goal of this study was to characterize the
evoked potentials from the inner ear saccule of the pla-
inWn midshipman Wsh and determine the auditory
threshold sensitivity, dynamic range and frequency
response of midshipman saccular hair cells to behavior-
ally relevant single tone stimuli. In this study, I focus
on the saccular potentials of non-reproductive Wsh to
establish baseline data for midshipman saccular hair
cells with the non-reproductive auditory phenotype. I
compare the saccular hair cell frequency response
properties to that of the saccular aVerent response
properties from previous work and interpret my Wnd-
ings as they relate to possible adaptations of the mid-
shipman peripheral auditory system for the detection
of conspeciWc vocalization during social interactions.
Materials and methods
Animals
PlainWn midshipman Wsh (Porichthys notatus) are
known to have three adult reproductive morphs that
include females and two male morphs: types I and II
(Bass 1996). Type I males build nests, acoustically court
females, and provide parental care for fertilized eggs
during the breeding season, whereas type II males nei-
ther build nests nor acoustically court females, but
instead sneak or satellite spawn to steal fertilizations
from type I males (Brantley and Bass 1994). Twenty-six
adult plainWn midshipman Wsh, both females and type I
males, were collected during the non-reproductive sea-
son in late November 2005, mid February 2006, and
early March 2006 by otter trawl (R/V Kittiwake, Bio-
Marine Enterprises, and the R/V Centennial, Friday
Harbor Marine Labs) in Puget Sound near Edmonds,
WA, USA and in Bellingham Bay, WA, USA. All the
non-reproductive animals included in this study were
collected outside of the breeding season in oVshore
sites and designated as type I males or females were
well above the previously reported size range of ana-
tomically identiWed type I males (SL ¸ 10.5 cm) and
females (SL ¸ 8.5 cm) collected from nest sites during
the summer breeding season (Brantley et al. 1993; Bass
et al. 1996; Grober et al. 1994; Foran and Bass 1998).
Only one male (SL = 10.8 cm) in this study was smaller
than the reported upper size limit for type II males
(approximately 13–14 cm SL) (Brantley et al. 1993;
Grober et al. 1994). Thus, it is a low probability that the
majority of the males used in this study were misidenti-
Wed as type I males. All animals were maintained in
saltwater aquaria at 14–16°C and fed a diet of goldWsh
every 2–4 days.123