137
Sound is composed of two major components, the propagating sound pressure
wave and particle motion. All fi sh detect particle motion (the directional component
of sound) using their inner ear otoliths (otoconia in case of elasmobranchs) which
act as accelerometers (see for review Casper 2006 ). There have been two proposed
pathways of sound to the inner ear. The inner ear otoconia are the main players in
the otolithic pathway. Because the density of the shark’s body is approximately
equal to the surrounding water, sound essentially travels through the shark’s body
until it comes in contact with structures of a different density in the ear. In teleost
fi sh these structures are solid calcium carbonate otoliths. In elasmobranchs they are
represented by otoconia which contain calcium carbonate, with silica nanoparticles
of exogenous origin, but localized within gelatinous matrix. As sound moves
through the fi sh body, it comes in contact with these structures which are overlying
the sensory hair cells of the inner ear. “Since they are denser than the surrounding
tissues, they will lag relative to the rest of the body in the sound fi eld. This lag
causes a shearing of the hair cells, thus stimulating the ear,” (Casper 2006 ).
Of course, today, the data regarding to the chemistry and composition of otoliths is
amazing, especially with respect to specifi c proteins, mechanisms of crystal growth,
and metal incorporation into otoliths (see for review Melancon et al. 2008 ). Additionally,
novel scientifi c directions like climate change obtain interesting information from the
otolith research. Recently, Checkley et al. ( 2009 ) suggested that otoliths in eggs and
larvae of White Sea bass ( Atractoscion nobilis ) reared in seawater with elevated CO 2
would grow more slowly than they do in the same water, but with normal concentration
of CO 2 . Contrary to expectations, the otoliths of fi sh grown in seawater with high CO 2
,
and, correspondingly, lower pH and saturation state of CaCO 3 , were signifi cantly larger
than those of experimental animals grown under simulations of present-day conditions.
As reported by these authors, “estimated otolith masses were 10 to 14 % and 24 to
26 % greater, respectively, for fi sh under 993 and 2,558 μatm of CO 2 . The dry mass of
fi sh did not vary with CO 2 , and thus fi sh of the same size had larger otoliths when
grown under elevated CO 2 ,” (Checkley et al. 2009 ).
Results reported by Munday et al. ( 2011 ) “support the hypothesis that pH regulation
in the otolith endolymph can lead to increased precipitation of CaCO 3 in otoliths of
larval fi sh exposed to elevated CO 2 ,” (Munday et al. 2011 ). However, these data also
suggested some differences between fi sh species with respect to sensitivity. This is
a very interesting effect for better understanding of the infl uence of elevated CO 2 on
marine biomineralization in the ocean. Increase of the carbon dioxide content in the
aquatic environments may regulate the biomineralization- demineralization circle of
calcium-based skeletons of diverse marine taxa.
3.3.1 Chemistry and Biochemistry of Otoconia and Otoliths
One of the fi rst chemical analyses of teleost otoliths (statoliths) was carried out by
Wicke ( 1863 ) who found that the statoliths of cod consisted of 91.1 % inorganic and
8.9 % organic material. Chemical composition of the Trout ( Oncorhynchus mykiss )
3.3 Otoconia and Otoliths
Sound is composed of two major components, the propagating sound pressure
wave and particle motion. All fi sh detect particle motion (the directional component
of sound) using their inner ear otoliths (otoconia in case of elasmobranchs) which
act as accelerometers (see for review Casper 2006 ). There have been two proposed
pathways of sound to the inner ear. The inner ear otoconia are the main players in
the otolithic pathway. Because the density of the shark’s body is approximately
equal to the surrounding water, sound essentially travels through the shark’s body
until it comes in contact with structures of a different density in the ear. In teleost
fi sh these structures are solid calcium carbonate otoliths. In elasmobranchs they are
represented by otoconia which contain calcium carbonate, with silica nanoparticles
of exogenous origin, but localized within gelatinous matrix. As sound moves
through the fi sh body, it comes in contact with these structures which are overlying
the sensory hair cells of the inner ear. “Since they are denser than the surrounding
tissues, they will lag relative to the rest of the body in the sound fi eld. This lag
causes a shearing of the hair cells, thus stimulating the ear,” (Casper 2006 ).
Of course, today, the data regarding to the chemistry and composition of otoliths is
amazing, especially with respect to specifi c proteins, mechanisms of crystal growth,
and metal incorporation into otoliths (see for review Melancon et al. 2008 ). Additionally,
novel scientifi c directions like climate change obtain interesting information from the
otolith research. Recently, Checkley et al. ( 2009 ) suggested that otoliths in eggs and
larvae of White Sea bass ( Atractoscion nobilis ) reared in seawater with elevated CO 2
would grow more slowly than they do in the same water, but with normal concentration
of CO 2 . Contrary to expectations, the otoliths of fi sh grown in seawater with high CO 2
,
and, correspondingly, lower pH and saturation state of CaCO 3 , were signifi cantly larger
than those of experimental animals grown under simulations of present-day conditions.
As reported by these authors, “estimated otolith masses were 10 to 14 % and 24 to
26 % greater, respectively, for fi sh under 993 and 2,558 μatm of CO 2 . The dry mass of
fi sh did not vary with CO 2 , and thus fi sh of the same size had larger otoliths when
grown under elevated CO 2 ,” (Checkley et al. 2009 ).
Results reported by Munday et al. ( 2011 ) “support the hypothesis that pH regulation
in the otolith endolymph can lead to increased precipitation of CaCO 3 in otoliths of
larval fi sh exposed to elevated CO 2 ,” (Munday et al. 2011 ). However, these data also
suggested some differences between fi sh species with respect to sensitivity. This is
a very interesting effect for better understanding of the infl uence of elevated CO 2 on
marine biomineralization in the ocean. Increase of the carbon dioxide content in the
aquatic environments may regulate the biomineralization- demineralization circle of
calcium-based skeletons of diverse marine taxa.
3.3.1 Chemistry and Biochemistry of Otoconia and Otoliths
One of the fi rst chemical analyses of teleost otoliths (statoliths) was carried out by
Wicke ( 1863 ) who found that the statoliths of cod consisted of 91.1 % inorganic and
8.9 % organic material. Chemical composition of the Trout ( Oncorhynchus mykiss )
3.3 Otoconia and Otoliths