Mochokidae are able to produce pectoral spine stridulation sounds. During sound production, high ... more Mochokidae are able to produce pectoral spine stridulation sounds. During sound production, high speed videos were used to study the pectoral fin movements to identify the mechanisms involved. A call consisted of a series of pulses and occurred during a spine sweep, which was in fact made up of a series of jerky movements. The morphology of the pectoral spines and associated muscles was also observed in different species. The contractions of adductor profundus and superficial adductor allows adduction and abduction movements (sweep) of the spine, respectively. Simultaneously, the contraction of the arrector ventralis or the arrector 3 of the pectoral spine allows the pulling and pressing the ridges of the dorsal process, against the rough lateral face of the spinal fossa. This results in the rubbing of the ridges of the dorsal process, producing sounds. In Synodontis the analogy for sound production would be a brake shoe pressing against a wheel. Supplementary material available online at http://jeb.biologists.org/cgi/content/full/213/7/1107/DC1 Key words: Mochokidae, acoustics, catfish, sound production, spine.
Abstract Stridulatory sound-producing behavior is widespread across catfish families, but some ar... more Abstract Stridulatory sound-producing behavior is widespread across catfish families, but some are silent. To understand why, we compared spine morphology and ecotype of silent and vocal clades. We determined vocal ability of laboratory specimens during disturbance behavior. Vocal families had bony (not flexible or segmented) spines, well-developed anterior and/or posterior serrations, and statistically significantly longer spines. We compared morphology of the proximal end of the pectoral spine between vocal and silent species. For vocal taxa, microscopic rounded or bladed ridges or knobs were present on the dorsal process. Most silent species had reduced processes with exclusively smooth, convoluted, or honeycombed surfaces very similar to spine-locking surfaces, or they had novel surfaces (beaded, vacuolated, cobwebbed). Most callichthyids had ridges but many were silent during disturbance. All doradid, most auchenipterid and most mochokid species were vocal and had ridges or knobs. Within the Auchenipteridae, vocal species had spines with greater weight and serration development but not length. Silent auchenipterids had thin, brittle, distally segmented spines with few microscopic serrations on only one margin and a highly reduced dorsal process lacking any known vocal morphology. Silent auchenipterids are derived and pelagic, while all vocal genera are basal and benthopelagic. This is the first phylogenetic evidence for stridulation mechanism loss within catfishes. Phylogenetic mapping of vocal ability, spine condition, and ecotype revealed the repeated presence of silence and vocal taxa, short and long spines, and ecotype shifts within clades. The appearance and loss of vocal behavior and supporting morphologies may have facilitated diversification among catfishes [Current Zoology 56 (1): 73–89 2010]. Key words Bioacoustic, Defense mechanisms, Historical biology, Stridulation Studies of sound-producing behavior in catfishes (Teleostei: Siluriformes) highlight the importance of sound signals in reproductive and agonistic behavioral contexts (Kaatz, 2002; Fine and Ladich, 2003). Pfeiffer and Eisenberg (1965) hypothesized that catfishes with weaponized pectoral spines produce disturbance sounds as a form of acoustic aposematism, but an experimental study of one species did not support this hypothesis (Bosher et al., 2006). Disturbance sounds are produced when a catfish is physically restrained in a way similar to an interspecific or predatory attack and can indicate the presence of stridulation signaling in undisturbed intraspecific contexts (Kaatz, 1999). Heyd and Pfeiffer (2000) observed that chemical alarm signals were weakened or absent from species that were vocal during disturbance. These findings suggest that disturbance could function as a
Abstract Swimbladder disturbance sounds of doradoid catfishes (Doradidae and Auchenipteridae) dem... more Abstract Swimbladder disturbance sounds of doradoid catfishes (Doradidae and Auchenipteridae) demonstrated striking waveform and spectrographic variation. We surveyed sounds of 25 doradoid species in 20 genera comparing these to sounds of four vocal outgroup catfish families. Sounds were either continuous waveforms (lacking interpulses) or pulsed (groups of pulses repeated at fixed temporal intervals). This is the first evidence for swimbladder calls with fixed interpulse patterns in catfishes. Vocal mechanism components that were similar between doradids and auchenipterids included: swimbladder shape, swimbladder dimensions and sonic muscle-somatic index. Morphological traits that showed variation among taxa and were evaluated for potential correlates of call diversity are: 1) diverticula (marginal outpocketings of the swimbladder with no connection to inner ear) and 2) elastic spring apparatus Müllerian rami (ESA-Mr). Within the doradid subfamilies and within the Auchenipteridae most species differed significantly in dominant frequency with frequency ranges overlapping to some extent for most. Doradid swimbladder diverticula did not explain dominant frequency variation within the doradoid superfamily. Some doradids with conical ESA-Mr had the highest dominant frequency sounds. Auchenipterids included both relatively lower and higher dominant frequency sound producers but lacked diverticula and had discoidal ESA-Mr. Comparing a phylogeny of doradoid genera with outgroup taxa, we infer that complex diverticula and conical ESA-Mr are derived characters within the Doradidae. Species representing outgroup families produced either continuous lower dominant frequency sounds (aspredinids, mochokids and pseudopimelodids) or pulsed higher dominant frequency sounds (pimelodids) [Current Zoology 58 (1): 171–188, 2012]. Keywords Catfishes, Communication, Signal evolution, Vocal mechanisms
Titles and headings should be checked carefully for spelling and capitalization. Please be sure t... more Titles and headings should be checked carefully for spelling and capitalization. Please be sure that the correct typeface and size have been used to indicate the proper level of heading. Review numbered items for proper order -e.g., tables, figures, footnotes, and lists. Proofread the captions and credit lines of illustrations and tables. Ensure that any material requiring permissions has the required credit line, and that the corresponding documentation has been sent to Elsevier.
One of the key morphological features of cichlid fishes is their highly developed pharyngeal jaw ... more One of the key morphological features of cichlid fishes is their highly developed pharyngeal jaw complex used in feeding (1). Although many studies focused on the anatomy (2) and function (1) of pharyngeal muscles, the potential physiological differences between them have not been examined in detail. The purpose of this paper is to investigate the capacity for anaerobic activity of the muscles in the pharyngeal jaw complex, and to assess whether they are all the same functional type. Finding different types would suggest that various muscles in the complex may have functions other than mastication.
AND BEHAVIOR 241 determine with certainty whether these recordings were made from For this cell, ... more AND BEHAVIOR 241 determine with certainty whether these recordings were made from For this cell, hypothetical excitatory and inhibitory magnitudes are primary afferent axons or from cells of the DON, response patterns approximately equal at all levels, with the excitatory cosine oriclassified as very sharpened or moderately sharpened (40%) were ented at about 36" to the left front, and the inhibitory cosine never observed in over 400 recordings from saccular afferents .
The evolutionary selection pressures and constraints responsible for the loss of sound signal com... more The evolutionary selection pressures and constraints responsible for the loss of sound signal communication in fishes are poorly understood. Pectoral spine stridulation is common in catfishes. Spines are part of predator defense or social display in known vocal species. Several catfish clades have secondarily lost the ability to produce sounds. We test the hypothesis that change in functional attributes of the pectoral fin and in particular the spine can lead to loss of sound production. We compared the length of the spine across 38 catfish families (993 species) from the literature and found it statistically significantly longer in vocal families. Spines of families with vocal species also had increased ossification and serration. Microscopy (scanning electron and compound) of the surface morphology of the dorsal process where bony vocal ridges are located identified four ridge types at the base of the spine that were absent in silent taxa (124 species, 21 families). We compared locking and swimming behavior, spine strength, dorsal process dimensions and microscopic surface structure for six species of doradoid catfishes. Silent species used fins for hovering not spine locking, while vocal species used spines as weapons in defense and locking. Silent species had atrophied spines and processes while vocal species had well developed spines and processes with "vocal ridges". Thus, there appears to be an integral trade-off in the evolutionary design of pectoral spines. We further evaluate the functional shift hypothesis by identifying other suites of ecological and behavioral traits possibly associated with silent vs. vocal catfishes.
One of the key morphological features of cichlid fishes is their highly developed pharyngeal jaw ... more One of the key morphological features of cichlid fishes is their highly developed pharyngeal jaw complex used in feeding (1). Although many studies focused on the anatomy (2) and function (1) of pharyngeal muscles, the potential physiological differences between them have not been examined in detail. The purpose of this paper is to investigate the capacity for anaerobic activity of the muscles in the pharyngeal jaw complex, and to assess whether they are all the same functional type. Finding different types would suggest that various muscles in the complex may have functions other than mastication.
AND BEHAVIOR 241 determine with certainty whether these recordings were made from For this cell, ... more AND BEHAVIOR 241 determine with certainty whether these recordings were made from For this cell, hypothetical excitatory and inhibitory magnitudes are primary afferent axons or from cells of the DON, response patterns approximately equal at all levels, with the excitatory cosine oriclassified as very sharpened or moderately sharpened (40%) were ented at about 36" to the left front, and the inhibitory cosine never observed in over 400 recordings from saccular afferents .
Stridulatory sound-producing behavior is widespread across catfish families, but some are silent.... more Stridulatory sound-producing behavior is widespread across catfish families, but some are silent. To understand why, we compared spine morphology and ecotype of silent and vocal clades. We determined vocal ability of laboratory specimens during disturbance behavior. Vocal families had bony (not flexible or segmented) spines, well-developed anterior and/or posterior serrations, and statistically significantly longer spines. We compared morphology of the proximal end of the pectoral spine between vocal and silent species. For vocal taxa, microscopic rounded or bladed ridges or knobs were present on the dorsal process.
Mochokidae are able to produce pectoral spine stridulation sounds. During sound production, high ... more Mochokidae are able to produce pectoral spine stridulation sounds. During sound production, high speed videos were used to study the pectoral fin movements to identify the mechanisms involved. A call consisted of a series of pulses and occurred during a spine sweep, which was in fact made up of a series of jerky movements. The morphology of the pectoral spines and associated muscles was also observed in different species. The contractions of adductor profundus and superficial adductor allows adduction and abduction movements (sweep) of the spine, respectively. Simultaneously, the contraction of the arrector ventralis or the arrector 3 of the pectoral spine allows the pulling and pressing the ridges of the dorsal process, against the rough lateral face of the spinal fossa. This results in the rubbing of the ridges of the dorsal process, producing sounds. In Synodontis the analogy for sound production would be a brake shoe pressing against a wheel. Supplementary material available online at http://jeb.biologists.org/cgi/content/full/213/7/1107/DC1 Key words: Mochokidae, acoustics, catfish, sound production, spine.
Abstract Stridulatory sound-producing behavior is widespread across catfish families, but some ar... more Abstract Stridulatory sound-producing behavior is widespread across catfish families, but some are silent. To understand why, we compared spine morphology and ecotype of silent and vocal clades. We determined vocal ability of laboratory specimens during disturbance behavior. Vocal families had bony (not flexible or segmented) spines, well-developed anterior and/or posterior serrations, and statistically significantly longer spines. We compared morphology of the proximal end of the pectoral spine between vocal and silent species. For vocal taxa, microscopic rounded or bladed ridges or knobs were present on the dorsal process. Most silent species had reduced processes with exclusively smooth, convoluted, or honeycombed surfaces very similar to spine-locking surfaces, or they had novel surfaces (beaded, vacuolated, cobwebbed). Most callichthyids had ridges but many were silent during disturbance. All doradid, most auchenipterid and most mochokid species were vocal and had ridges or knobs. Within the Auchenipteridae, vocal species had spines with greater weight and serration development but not length. Silent auchenipterids had thin, brittle, distally segmented spines with few microscopic serrations on only one margin and a highly reduced dorsal process lacking any known vocal morphology. Silent auchenipterids are derived and pelagic, while all vocal genera are basal and benthopelagic. This is the first phylogenetic evidence for stridulation mechanism loss within catfishes. Phylogenetic mapping of vocal ability, spine condition, and ecotype revealed the repeated presence of silence and vocal taxa, short and long spines, and ecotype shifts within clades. The appearance and loss of vocal behavior and supporting morphologies may have facilitated diversification among catfishes [Current Zoology 56 (1): 73–89 2010]. Key words Bioacoustic, Defense mechanisms, Historical biology, Stridulation Studies of sound-producing behavior in catfishes (Teleostei: Siluriformes) highlight the importance of sound signals in reproductive and agonistic behavioral contexts (Kaatz, 2002; Fine and Ladich, 2003). Pfeiffer and Eisenberg (1965) hypothesized that catfishes with weaponized pectoral spines produce disturbance sounds as a form of acoustic aposematism, but an experimental study of one species did not support this hypothesis (Bosher et al., 2006). Disturbance sounds are produced when a catfish is physically restrained in a way similar to an interspecific or predatory attack and can indicate the presence of stridulation signaling in undisturbed intraspecific contexts (Kaatz, 1999). Heyd and Pfeiffer (2000) observed that chemical alarm signals were weakened or absent from species that were vocal during disturbance. These findings suggest that disturbance could function as a
Abstract Swimbladder disturbance sounds of doradoid catfishes (Doradidae and Auchenipteridae) dem... more Abstract Swimbladder disturbance sounds of doradoid catfishes (Doradidae and Auchenipteridae) demonstrated striking waveform and spectrographic variation. We surveyed sounds of 25 doradoid species in 20 genera comparing these to sounds of four vocal outgroup catfish families. Sounds were either continuous waveforms (lacking interpulses) or pulsed (groups of pulses repeated at fixed temporal intervals). This is the first evidence for swimbladder calls with fixed interpulse patterns in catfishes. Vocal mechanism components that were similar between doradids and auchenipterids included: swimbladder shape, swimbladder dimensions and sonic muscle-somatic index. Morphological traits that showed variation among taxa and were evaluated for potential correlates of call diversity are: 1) diverticula (marginal outpocketings of the swimbladder with no connection to inner ear) and 2) elastic spring apparatus Müllerian rami (ESA-Mr). Within the doradid subfamilies and within the Auchenipteridae most species differed significantly in dominant frequency with frequency ranges overlapping to some extent for most. Doradid swimbladder diverticula did not explain dominant frequency variation within the doradoid superfamily. Some doradids with conical ESA-Mr had the highest dominant frequency sounds. Auchenipterids included both relatively lower and higher dominant frequency sound producers but lacked diverticula and had discoidal ESA-Mr. Comparing a phylogeny of doradoid genera with outgroup taxa, we infer that complex diverticula and conical ESA-Mr are derived characters within the Doradidae. Species representing outgroup families produced either continuous lower dominant frequency sounds (aspredinids, mochokids and pseudopimelodids) or pulsed higher dominant frequency sounds (pimelodids) [Current Zoology 58 (1): 171–188, 2012]. Keywords Catfishes, Communication, Signal evolution, Vocal mechanisms
Titles and headings should be checked carefully for spelling and capitalization. Please be sure t... more Titles and headings should be checked carefully for spelling and capitalization. Please be sure that the correct typeface and size have been used to indicate the proper level of heading. Review numbered items for proper order -e.g., tables, figures, footnotes, and lists. Proofread the captions and credit lines of illustrations and tables. Ensure that any material requiring permissions has the required credit line, and that the corresponding documentation has been sent to Elsevier.
One of the key morphological features of cichlid fishes is their highly developed pharyngeal jaw ... more One of the key morphological features of cichlid fishes is their highly developed pharyngeal jaw complex used in feeding (1). Although many studies focused on the anatomy (2) and function (1) of pharyngeal muscles, the potential physiological differences between them have not been examined in detail. The purpose of this paper is to investigate the capacity for anaerobic activity of the muscles in the pharyngeal jaw complex, and to assess whether they are all the same functional type. Finding different types would suggest that various muscles in the complex may have functions other than mastication.
AND BEHAVIOR 241 determine with certainty whether these recordings were made from For this cell, ... more AND BEHAVIOR 241 determine with certainty whether these recordings were made from For this cell, hypothetical excitatory and inhibitory magnitudes are primary afferent axons or from cells of the DON, response patterns approximately equal at all levels, with the excitatory cosine oriclassified as very sharpened or moderately sharpened (40%) were ented at about 36" to the left front, and the inhibitory cosine never observed in over 400 recordings from saccular afferents .
The evolutionary selection pressures and constraints responsible for the loss of sound signal com... more The evolutionary selection pressures and constraints responsible for the loss of sound signal communication in fishes are poorly understood. Pectoral spine stridulation is common in catfishes. Spines are part of predator defense or social display in known vocal species. Several catfish clades have secondarily lost the ability to produce sounds. We test the hypothesis that change in functional attributes of the pectoral fin and in particular the spine can lead to loss of sound production. We compared the length of the spine across 38 catfish families (993 species) from the literature and found it statistically significantly longer in vocal families. Spines of families with vocal species also had increased ossification and serration. Microscopy (scanning electron and compound) of the surface morphology of the dorsal process where bony vocal ridges are located identified four ridge types at the base of the spine that were absent in silent taxa (124 species, 21 families). We compared locking and swimming behavior, spine strength, dorsal process dimensions and microscopic surface structure for six species of doradoid catfishes. Silent species used fins for hovering not spine locking, while vocal species used spines as weapons in defense and locking. Silent species had atrophied spines and processes while vocal species had well developed spines and processes with "vocal ridges". Thus, there appears to be an integral trade-off in the evolutionary design of pectoral spines. We further evaluate the functional shift hypothesis by identifying other suites of ecological and behavioral traits possibly associated with silent vs. vocal catfishes.
One of the key morphological features of cichlid fishes is their highly developed pharyngeal jaw ... more One of the key morphological features of cichlid fishes is their highly developed pharyngeal jaw complex used in feeding (1). Although many studies focused on the anatomy (2) and function (1) of pharyngeal muscles, the potential physiological differences between them have not been examined in detail. The purpose of this paper is to investigate the capacity for anaerobic activity of the muscles in the pharyngeal jaw complex, and to assess whether they are all the same functional type. Finding different types would suggest that various muscles in the complex may have functions other than mastication.
AND BEHAVIOR 241 determine with certainty whether these recordings were made from For this cell, ... more AND BEHAVIOR 241 determine with certainty whether these recordings were made from For this cell, hypothetical excitatory and inhibitory magnitudes are primary afferent axons or from cells of the DON, response patterns approximately equal at all levels, with the excitatory cosine oriclassified as very sharpened or moderately sharpened (40%) were ented at about 36" to the left front, and the inhibitory cosine never observed in over 400 recordings from saccular afferents .
Stridulatory sound-producing behavior is widespread across catfish families, but some are silent.... more Stridulatory sound-producing behavior is widespread across catfish families, but some are silent. To understand why, we compared spine morphology and ecotype of silent and vocal clades. We determined vocal ability of laboratory specimens during disturbance behavior. Vocal families had bony (not flexible or segmented) spines, well-developed anterior and/or posterior serrations, and statistically significantly longer spines. We compared morphology of the proximal end of the pectoral spine between vocal and silent species. For vocal taxa, microscopic rounded or bladed ridges or knobs were present on the dorsal process.
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Papers by Ingrid Kaatz
study the pectoral fin movements to identify the mechanisms involved. A call consisted of a series of pulses and occurred during
a spine sweep, which was in fact made up of a series of jerky movements. The morphology of the pectoral spines and associated
muscles was also observed in different species. The contractions of adductor profundus and superficial adductor allows
adduction and abduction movements (sweep) of the spine, respectively. Simultaneously, the contraction of the arrector ventralis
or the arrector 3 of the pectoral spine allows the pulling and pressing the ridges of the dorsal process, against the rough lateral
face of the spinal fossa. This results in the rubbing of the ridges of the dorsal process, producing sounds. In Synodontis the
analogy for sound production would be a brake shoe pressing against a wheel.
Supplementary material available online at http://jeb.biologists.org/cgi/content/full/213/7/1107/DC1
Key words: Mochokidae, acoustics, catfish, sound production, spine.
we compared spine morphology and ecotype of silent and vocal clades. We determined vocal ability of laboratory specimens during
disturbance behavior. Vocal families had bony (not flexible or segmented) spines, well-developed anterior and/or posterior
serrations, and statistically significantly longer spines. We compared morphology of the proximal end of the pectoral spine between
vocal and silent species. For vocal taxa, microscopic rounded or bladed ridges or knobs were present on the dorsal process.
Most silent species had reduced processes with exclusively smooth, convoluted, or honeycombed surfaces very similar to
spine-locking surfaces, or they had novel surfaces (beaded, vacuolated, cobwebbed). Most callichthyids had ridges but many were
silent during disturbance. All doradid, most auchenipterid and most mochokid species were vocal and had ridges or knobs.
Within the Auchenipteridae, vocal species had spines with greater weight and serration development but not length. Silent
auchenipterids had thin, brittle, distally segmented spines with few microscopic serrations on only one margin and a highly reduced
dorsal process lacking any known vocal morphology. Silent auchenipterids are derived and pelagic, while all vocal genera
are basal and benthopelagic. This is the first phylogenetic evidence for stridulation mechanism loss within catfishes. Phylogenetic
mapping of vocal ability, spine condition, and ecotype revealed the repeated presence of silence and vocal taxa, short and long
spines, and ecotype shifts within clades. The appearance and loss of vocal behavior and supporting morphologies may have facilitated
diversification among catfishes [Current Zoology 56 (1): 73–89 2010].
Key words Bioacoustic, Defense mechanisms, Historical biology, Stridulation
Studies of sound-producing behavior in catfishes
(Teleostei: Siluriformes) highlight the importance of
sound signals in reproductive and agonistic behavioral
contexts (Kaatz, 2002; Fine and Ladich, 2003). Pfeiffer
and Eisenberg (1965) hypothesized that catfishes with
weaponized pectoral spines produce disturbance sounds
as a form of acoustic aposematism, but an experimental
study of one species did not support this hypothesis
(Bosher et al., 2006). Disturbance sounds are produced
when a catfish is physically restrained in a way similar
to an interspecific or predatory attack and can indicate
the presence of stridulation signaling in undisturbed
intraspecific contexts (Kaatz, 1999). Heyd and Pfeiffer
(2000) observed that chemical alarm signals were
weakened or absent from species that were vocal during
disturbance. These findings suggest that disturbance
could function as a
waveform and spectrographic variation. We surveyed sounds of 25 doradoid species in 20 genera comparing these to sounds of
four vocal outgroup catfish families. Sounds were either continuous waveforms (lacking interpulses) or pulsed (groups of pulses
repeated at fixed temporal intervals). This is the first evidence for swimbladder calls with fixed interpulse patterns in catfishes.
Vocal mechanism components that were similar between doradids and auchenipterids included: swimbladder shape, swimbladder
dimensions and sonic muscle-somatic index. Morphological traits that showed variation among taxa and were evaluated for potential
correlates of call diversity are: 1) diverticula (marginal outpocketings of the swimbladder with no connection to inner ear)
and 2) elastic spring apparatus Müllerian rami (ESA-Mr). Within the doradid subfamilies and within the Auchenipteridae most
species differed significantly in dominant frequency with frequency ranges overlapping to some extent for most. Doradid swimbladder
diverticula did not explain dominant frequency variation within the doradoid superfamily. Some doradids with conical
ESA-Mr had the highest dominant frequency sounds. Auchenipterids included both relatively lower and higher dominant frequency
sound producers but lacked diverticula and had discoidal ESA-Mr. Comparing a phylogeny of doradoid genera with outgroup
taxa, we infer that complex diverticula and conical ESA-Mr are derived characters within the Doradidae. Species representing
outgroup families produced either continuous lower dominant frequency sounds (aspredinids, mochokids and pseudopimelodids)
or pulsed higher dominant frequency sounds (pimelodids) [Current Zoology 58 (1): 171–188, 2012].
Keywords Catfishes, Communication, Signal evolution, Vocal mechanisms
study the pectoral fin movements to identify the mechanisms involved. A call consisted of a series of pulses and occurred during
a spine sweep, which was in fact made up of a series of jerky movements. The morphology of the pectoral spines and associated
muscles was also observed in different species. The contractions of adductor profundus and superficial adductor allows
adduction and abduction movements (sweep) of the spine, respectively. Simultaneously, the contraction of the arrector ventralis
or the arrector 3 of the pectoral spine allows the pulling and pressing the ridges of the dorsal process, against the rough lateral
face of the spinal fossa. This results in the rubbing of the ridges of the dorsal process, producing sounds. In Synodontis the
analogy for sound production would be a brake shoe pressing against a wheel.
Supplementary material available online at http://jeb.biologists.org/cgi/content/full/213/7/1107/DC1
Key words: Mochokidae, acoustics, catfish, sound production, spine.
we compared spine morphology and ecotype of silent and vocal clades. We determined vocal ability of laboratory specimens during
disturbance behavior. Vocal families had bony (not flexible or segmented) spines, well-developed anterior and/or posterior
serrations, and statistically significantly longer spines. We compared morphology of the proximal end of the pectoral spine between
vocal and silent species. For vocal taxa, microscopic rounded or bladed ridges or knobs were present on the dorsal process.
Most silent species had reduced processes with exclusively smooth, convoluted, or honeycombed surfaces very similar to
spine-locking surfaces, or they had novel surfaces (beaded, vacuolated, cobwebbed). Most callichthyids had ridges but many were
silent during disturbance. All doradid, most auchenipterid and most mochokid species were vocal and had ridges or knobs.
Within the Auchenipteridae, vocal species had spines with greater weight and serration development but not length. Silent
auchenipterids had thin, brittle, distally segmented spines with few microscopic serrations on only one margin and a highly reduced
dorsal process lacking any known vocal morphology. Silent auchenipterids are derived and pelagic, while all vocal genera
are basal and benthopelagic. This is the first phylogenetic evidence for stridulation mechanism loss within catfishes. Phylogenetic
mapping of vocal ability, spine condition, and ecotype revealed the repeated presence of silence and vocal taxa, short and long
spines, and ecotype shifts within clades. The appearance and loss of vocal behavior and supporting morphologies may have facilitated
diversification among catfishes [Current Zoology 56 (1): 73–89 2010].
Key words Bioacoustic, Defense mechanisms, Historical biology, Stridulation
Studies of sound-producing behavior in catfishes
(Teleostei: Siluriformes) highlight the importance of
sound signals in reproductive and agonistic behavioral
contexts (Kaatz, 2002; Fine and Ladich, 2003). Pfeiffer
and Eisenberg (1965) hypothesized that catfishes with
weaponized pectoral spines produce disturbance sounds
as a form of acoustic aposematism, but an experimental
study of one species did not support this hypothesis
(Bosher et al., 2006). Disturbance sounds are produced
when a catfish is physically restrained in a way similar
to an interspecific or predatory attack and can indicate
the presence of stridulation signaling in undisturbed
intraspecific contexts (Kaatz, 1999). Heyd and Pfeiffer
(2000) observed that chemical alarm signals were
weakened or absent from species that were vocal during
disturbance. These findings suggest that disturbance
could function as a
waveform and spectrographic variation. We surveyed sounds of 25 doradoid species in 20 genera comparing these to sounds of
four vocal outgroup catfish families. Sounds were either continuous waveforms (lacking interpulses) or pulsed (groups of pulses
repeated at fixed temporal intervals). This is the first evidence for swimbladder calls with fixed interpulse patterns in catfishes.
Vocal mechanism components that were similar between doradids and auchenipterids included: swimbladder shape, swimbladder
dimensions and sonic muscle-somatic index. Morphological traits that showed variation among taxa and were evaluated for potential
correlates of call diversity are: 1) diverticula (marginal outpocketings of the swimbladder with no connection to inner ear)
and 2) elastic spring apparatus Müllerian rami (ESA-Mr). Within the doradid subfamilies and within the Auchenipteridae most
species differed significantly in dominant frequency with frequency ranges overlapping to some extent for most. Doradid swimbladder
diverticula did not explain dominant frequency variation within the doradoid superfamily. Some doradids with conical
ESA-Mr had the highest dominant frequency sounds. Auchenipterids included both relatively lower and higher dominant frequency
sound producers but lacked diverticula and had discoidal ESA-Mr. Comparing a phylogeny of doradoid genera with outgroup
taxa, we infer that complex diverticula and conical ESA-Mr are derived characters within the Doradidae. Species representing
outgroup families produced either continuous lower dominant frequency sounds (aspredinids, mochokids and pseudopimelodids)
or pulsed higher dominant frequency sounds (pimelodids) [Current Zoology 58 (1): 171–188, 2012].
Keywords Catfishes, Communication, Signal evolution, Vocal mechanisms