133
the long time of metazoan evolution. The answer to the question “where do the true
teeth begin?” is still open because of the existence of numerous mineralized
teeth- like structures, which are biocomposites that also have hierarchically organized
architecture. Moreover, these structures contain Ca-phosphate phases, collagen
and different acidic proteins similar to those described in true oral teeth, however in
other proportions and molecular orientations at the nanolevel. Thus, even in fi sh
teeth we can differentiate between enameloid and enamel, between dentine and
petrodentine, plicidentine, osteodentine, orthodentine etc. because of specifi city
of their chemistry, structural and material properties. Some of these biological
materials are not known for human teeth, whose surfaces at the macrolevel are
arranged only in a way that achieves cutting, crushing or grinding of a food supply.
Differences in biomechanics between human and marine vertebrate’s teeth are,
probably, determined by different mechanisms of biomineralization. For example,
the crystal shape in mammalian enamel is controlled by growth kinetics, whereas
in hyper mineralized lungfi sh dentine the crystal shape is controlled by a protein
scaffolding.
The fossilized teeth of extinct marine vertebrates represent a unique source of
ancient biological materials and reveal the principles of their structural organization.
3.3 Otoconia and Otoliths
Abstract Otoconia are crystalline biocomposites of calcium carbonate and phosphate phases with localization within the inner ear and vestibular system of marine
vertebrates. Thousands of micro-otoconia can exist separately, or can be organized
within the inertial mass. The transition from the otoconial mass to the rigid polycrystalline otolith probably occurred in fi sh by progressive fusion of otoconia from
a loose aggregate to a semi-rigid mass. The organic fraction of otoconia and otoliths
contains numerous specifi c proteins, some of which possess collagen domains.
Each mineral polymorph of otoconia contains proteins unique to that polymorph.
Molecular structure and composition of fi sh otoliths and their importance in ecological science are discussed.
Otoconia are composite-based microstructures of organic molecules and inorganic
crystals formed in the peripheral portion of the vestibular system of marine vertebrates.
“ Thousands of small otoconia provide inertial mass and generate shearing forces to
allow the cells to sense gravity and the organisms to maintain normal balance, ”
(Kawasaki et al. 2009 ; see also Hughes et al. 2006 ). Movement of the otoconial
layer through action of gravitational or inertial forces activate the underlying mechanosensory hair cells to generate action potentials that are transmitted to the brain
(Dror et al. 2010 ). Thus the otoconia must be located within an ear and vestibular
sensory apparatus.
3.3 Otoconia and Otoliths
the long time of metazoan evolution. The answer to the question “where do the true
teeth begin?” is still open because of the existence of numerous mineralized
teeth- like structures, which are biocomposites that also have hierarchically organized
architecture. Moreover, these structures contain Ca-phosphate phases, collagen
and different acidic proteins similar to those described in true oral teeth, however in
other proportions and molecular orientations at the nanolevel. Thus, even in fi sh
teeth we can differentiate between enameloid and enamel, between dentine and
petrodentine, plicidentine, osteodentine, orthodentine etc. because of specifi city
of their chemistry, structural and material properties. Some of these biological
materials are not known for human teeth, whose surfaces at the macrolevel are
arranged only in a way that achieves cutting, crushing or grinding of a food supply.
Differences in biomechanics between human and marine vertebrate’s teeth are,
probably, determined by different mechanisms of biomineralization. For example,
the crystal shape in mammalian enamel is controlled by growth kinetics, whereas
in hyper mineralized lungfi sh dentine the crystal shape is controlled by a protein
scaffolding.
The fossilized teeth of extinct marine vertebrates represent a unique source of
ancient biological materials and reveal the principles of their structural organization.
3.3 Otoconia and Otoliths
Abstract Otoconia are crystalline biocomposites of calcium carbonate and phosphate phases with localization within the inner ear and vestibular system of marine
vertebrates. Thousands of micro-otoconia can exist separately, or can be organized
within the inertial mass. The transition from the otoconial mass to the rigid polycrystalline otolith probably occurred in fi sh by progressive fusion of otoconia from
a loose aggregate to a semi-rigid mass. The organic fraction of otoconia and otoliths
contains numerous specifi c proteins, some of which possess collagen domains.
Each mineral polymorph of otoconia contains proteins unique to that polymorph.
Molecular structure and composition of fi sh otoliths and their importance in ecological science are discussed.
Otoconia are composite-based microstructures of organic molecules and inorganic
crystals formed in the peripheral portion of the vestibular system of marine vertebrates.
“ Thousands of small otoconia provide inertial mass and generate shearing forces to
allow the cells to sense gravity and the organisms to maintain normal balance, ”
(Kawasaki et al. 2009 ; see also Hughes et al. 2006 ). Movement of the otoconial
layer through action of gravitational or inertial forces activate the underlying mechanosensory hair cells to generate action potentials that are transmitted to the brain
(Dror et al. 2010 ). Thus the otoconia must be located within an ear and vestibular
sensory apparatus.
3.3 Otoconia and Otoliths