113
strictly for long-range detection and localization purposes in these taxa. One possible proximate function of acoustic signaling in vertebrates is rapid modulation of
the neuroendocrine profi le (e.g., Cheng et al. 1998 ; Remage-Healey and Bass 2005 ),
and sculpins, darters, and gobies would be useful taxa for investigations in that
direction. Exposing Etheostoma crossopterum females to male courtship sounds
lead to a decline in circulating oestrogen (Noel 2012 ), suggesting that sounds were
capable of inducing ovulation, since teleost ovulation is characterized by oestrogen
decline concurrent with maturation steroid elevation (Kime 1993 ).
7.2 What Selective Pressures and Constraints Affect Changes
in Acoustic Repertoire?
Darters, gobies, and sculpins could inform future investigations into the evolution
of acoustic repertoire expansion in fi shes because these taxa include members that
exemplify the continuum of simple pulse sounds to complex and harmonic sounds,
which is more broadly characteristic of fi sh sound diversity involving drumming
mechanisms (Amorim 2006 ). The problem of the emergence of tonal sounds and
of the relative role of tonal vs pulsatile components is a complex issue involving
numerous factors; some basic constraints that may apply to the production of
pulsatile versus tonal sounds and their effi cacy of reception by receivers are discussed here.
Pulsatile and tonal signals could have different energetic and production costs.
While fast twitch sonic muscle is highly metabolically active tissue (Parmentier and
Diogo 2006 ), O 2 consumption was not signifi cantly elevated in toadfi shes after prolonged muscle contraction, suggesting negligible energetic cost for sound production as a proportion of the total energy budget (Amorim et al. 2002 ). However,
sound duration may be still be limited by fatigue (Mitchell et al. 2008). Rapidly
contracting muscles producing tonal sounds are designed for contraction speed,
which involve a suite of physiological adaptations (reviewed by Parmentier and
Diogo 2006 ), but contraction speed can come with costs to power and/or endurance
(Rome and Lindstedt 1998 ; Mitchell et al. 2008). Long duration tonal sounds are
expected to generate fatigue more quickly than sparse pulsed sounds; trade-offs
between call duration and call rate have been supported in the boatwhistles of Gulf
toadfi sh, Opsanus beta (Thorson and Fine 2002 ).
Pulsatile and tonal sounds may differ in transmission in the environment and in
salience in the receiver auditory system. Tonal sounds could facilitate larger active
spaces than pulse trains, since tonal, frequency modulated sounds are more generally characteristic of long range signals in vertebrates (Wiley and Richards 1982 ;
Lugli and Fine 2007 ). Frequency modulated sounds could increase detectability by
stimulating a wider range of frequency fi lters in receivers (Wiley and Richards
1980). For example, tonal sounds may have evolved in association with territoriality
in highly territorial Padogobius spp., where longer detection ranges would be an
advantage. Differences in receiver auditory sensitivity to pulse intervals could also
result in differential encoding of pulsed versus tonal sounds (e.g., Crawford 1997 ).
Convergent Aspects of Acoustic Communication in Darters, Sculpins, and Gobies
strictly for long-range detection and localization purposes in these taxa. One possible proximate function of acoustic signaling in vertebrates is rapid modulation of
the neuroendocrine profi le (e.g., Cheng et al. 1998 ; Remage-Healey and Bass 2005 ),
and sculpins, darters, and gobies would be useful taxa for investigations in that
direction. Exposing Etheostoma crossopterum females to male courtship sounds
lead to a decline in circulating oestrogen (Noel 2012 ), suggesting that sounds were
capable of inducing ovulation, since teleost ovulation is characterized by oestrogen
decline concurrent with maturation steroid elevation (Kime 1993 ).
7.2 What Selective Pressures and Constraints Affect Changes
in Acoustic Repertoire?
Darters, gobies, and sculpins could inform future investigations into the evolution
of acoustic repertoire expansion in fi shes because these taxa include members that
exemplify the continuum of simple pulse sounds to complex and harmonic sounds,
which is more broadly characteristic of fi sh sound diversity involving drumming
mechanisms (Amorim 2006 ). The problem of the emergence of tonal sounds and
of the relative role of tonal vs pulsatile components is a complex issue involving
numerous factors; some basic constraints that may apply to the production of
pulsatile versus tonal sounds and their effi cacy of reception by receivers are discussed here.
Pulsatile and tonal signals could have different energetic and production costs.
While fast twitch sonic muscle is highly metabolically active tissue (Parmentier and
Diogo 2006 ), O 2 consumption was not signifi cantly elevated in toadfi shes after prolonged muscle contraction, suggesting negligible energetic cost for sound production as a proportion of the total energy budget (Amorim et al. 2002 ). However,
sound duration may be still be limited by fatigue (Mitchell et al. 2008). Rapidly
contracting muscles producing tonal sounds are designed for contraction speed,
which involve a suite of physiological adaptations (reviewed by Parmentier and
Diogo 2006 ), but contraction speed can come with costs to power and/or endurance
(Rome and Lindstedt 1998 ; Mitchell et al. 2008). Long duration tonal sounds are
expected to generate fatigue more quickly than sparse pulsed sounds; trade-offs
between call duration and call rate have been supported in the boatwhistles of Gulf
toadfi sh, Opsanus beta (Thorson and Fine 2002 ).
Pulsatile and tonal sounds may differ in transmission in the environment and in
salience in the receiver auditory system. Tonal sounds could facilitate larger active
spaces than pulse trains, since tonal, frequency modulated sounds are more generally characteristic of long range signals in vertebrates (Wiley and Richards 1982 ;
Lugli and Fine 2007 ). Frequency modulated sounds could increase detectability by
stimulating a wider range of frequency fi lters in receivers (Wiley and Richards
1980). For example, tonal sounds may have evolved in association with territoriality
in highly territorial Padogobius spp., where longer detection ranges would be an
advantage. Differences in receiver auditory sensitivity to pulse intervals could also
result in differential encoding of pulsed versus tonal sounds (e.g., Crawford 1997 ).
Convergent Aspects of Acoustic Communication in Darters, Sculpins, and Gobies