308
size groups, the authors did fi nd a signifi cant interaction between frequency and
age/size, as well as, a trend (but not signifi cant) which indicated that older fi sh may
have slightly lower thresholds. The same study also described a substantial increase
in the size of the saccular otolith and associated saccular epithelia of the inner ear
during development, suggesting that a large increase in the size of the inner ear size
does not necessarily lead to a signifi cant change in auditory sensitivity.
Batrachoidiformes
This order includes the midshipman fi sh and toadfi shes, which rely on acoustic
communication for social behaviors and, therefore, their auditory system has been
focus of attention in many studies including ontogeny.
According to Vasconcelos and Ladich ( 2008 ), the Lusitanian toadfi sh
Halobatrachus didactylus (Batrachoididae) exhibits slight developmental increases
in auditory sensitivity and maximum detectable frequency with age/size. Using the
AEP recording technique, the authors found that the smallest group analyzed
(3–4 cm SL) was circa 11 dB less sensitive at 100 Hz compared to larger size groups
and had a lower maximum detectable frequency (800 Hz). The remaining size
groups, which ranged from 5–7 to 20–32 cm SL, responded at all frequencies tested
(50–1000 Hz) with similar thresholds (Fig. 4 ).
Another member of Batrachoididae, the plainfi n midshipman ( Porichthys notatus ),
has also been investigated regarding ontogenetic changes in auditory capabilities
using electrophysiology and behavioral methods. Sisneros and Bass ( 2005 ) conducted extracellular single unit recordings from saccular afferents in different- sized
midshipman fi sh, from small juveniles (3–5 cm SL) to the adults (>10 cm SL). Both
resting discharge rate and auditory sensitivity increased with fi sh size, while the
temporal encoding of the tested frequencies at an iso-intensity of 130 dB re 1 μPa
did not show any signifi cant developmental shifts.
Also using the midshipman fi sh model, Alderks and Sisneros ( 2011 ) recorded
evoked saccular potentials to investigate potential ontogenetic changes in saccular
sensitivity across a wider range of animals from small juveniles (1.9–3.1 cm SL) to
adults (9–22.6 cm SL). The authors showed an ontogenetic retention of saccular
sensitivity with size (see Fig. 5 ). They also reported an increase in the maximum
detectable frequency with age/size such that larger fi sh were more likely to detect
frequencies greater than 385 Hz. Subsequently, Alderks and Sisneros ( 2013 )
reported the development of the acoustic startle-like response in different-sized
groups of midshipman fi sh larvae that ranged in size from 1.5 to 3.2 cm TL. The
acoustic startle response was fi rst observed in larvae at a size of 1.4 cm TL; above
1.8 cm TL, all larvae responded to a broadband stimulus of 154 dB re 1 μPa. Larval
fi sh from the medium size group (1.9–2.4 cm TL) had signifi cantly lower acoustic
startle-like thresholds at 75–145 Hz than the other size groups, which may be related
to differential growth and development of the saccule during different time points
during early larval development (Fig. 5 ). Future work will be needed to determine
the mechanisms responsible for the observed differences in acoustic startle-like
response among the size groups tested for this species.
R.O. Vasconcelos et al.
size groups, the authors did fi nd a signifi cant interaction between frequency and
age/size, as well as, a trend (but not signifi cant) which indicated that older fi sh may
have slightly lower thresholds. The same study also described a substantial increase
in the size of the saccular otolith and associated saccular epithelia of the inner ear
during development, suggesting that a large increase in the size of the inner ear size
does not necessarily lead to a signifi cant change in auditory sensitivity.
Batrachoidiformes
This order includes the midshipman fi sh and toadfi shes, which rely on acoustic
communication for social behaviors and, therefore, their auditory system has been
focus of attention in many studies including ontogeny.
According to Vasconcelos and Ladich ( 2008 ), the Lusitanian toadfi sh
Halobatrachus didactylus (Batrachoididae) exhibits slight developmental increases
in auditory sensitivity and maximum detectable frequency with age/size. Using the
AEP recording technique, the authors found that the smallest group analyzed
(3–4 cm SL) was circa 11 dB less sensitive at 100 Hz compared to larger size groups
and had a lower maximum detectable frequency (800 Hz). The remaining size
groups, which ranged from 5–7 to 20–32 cm SL, responded at all frequencies tested
(50–1000 Hz) with similar thresholds (Fig. 4 ).
Another member of Batrachoididae, the plainfi n midshipman ( Porichthys notatus ),
has also been investigated regarding ontogenetic changes in auditory capabilities
using electrophysiology and behavioral methods. Sisneros and Bass ( 2005 ) conducted extracellular single unit recordings from saccular afferents in different- sized
midshipman fi sh, from small juveniles (3–5 cm SL) to the adults (>10 cm SL). Both
resting discharge rate and auditory sensitivity increased with fi sh size, while the
temporal encoding of the tested frequencies at an iso-intensity of 130 dB re 1 μPa
did not show any signifi cant developmental shifts.
Also using the midshipman fi sh model, Alderks and Sisneros ( 2011 ) recorded
evoked saccular potentials to investigate potential ontogenetic changes in saccular
sensitivity across a wider range of animals from small juveniles (1.9–3.1 cm SL) to
adults (9–22.6 cm SL). The authors showed an ontogenetic retention of saccular
sensitivity with size (see Fig. 5 ). They also reported an increase in the maximum
detectable frequency with age/size such that larger fi sh were more likely to detect
frequencies greater than 385 Hz. Subsequently, Alderks and Sisneros ( 2013 )
reported the development of the acoustic startle-like response in different-sized
groups of midshipman fi sh larvae that ranged in size from 1.5 to 3.2 cm TL. The
acoustic startle response was fi rst observed in larvae at a size of 1.4 cm TL; above
1.8 cm TL, all larvae responded to a broadband stimulus of 154 dB re 1 μPa. Larval
fi sh from the medium size group (1.9–2.4 cm TL) had signifi cantly lower acoustic
startle-like thresholds at 75–145 Hz than the other size groups, which may be related
to differential growth and development of the saccule during different time points
during early larval development (Fig. 5 ). Future work will be needed to determine
the mechanisms responsible for the observed differences in acoustic startle-like
response among the size groups tested for this species.
R.O. Vasconcelos et al.