283
to present the description of specifi c dynamic locomotory structure that is formed
by the caudal peduncle and caudal fi n of the giant shark C. carcharias as follow:
“The caudal peduncle is a highly modifi ed, dorsoventrally compressed and rigid structure
that facilitates the oscillations of the caudal fi n. Its stiffness appears to be principally
achieved by a thick layer of adipose tissue that composes 28–37 % of its cross-sectional
area, reinforced by cross-woven collagen fi bers. The overlying layers of collagen fi bers of
the stratum compactum, oriented in steep left- and right-handed helices (∼65° to the shark’s
long axis), prevent bowstringing of the perimysial fi bers that lie just below the dermal layer.
Perimysial fi bers, muscles, and the notochord are restricted to the dorsal lobe of the caudal
fi n and comprise the bulk of its mass. Adipose tissue reinforces the leading edge of the
dorsal lobe of the caudal fi n and contributes to maintaining the ideal cross-sectional
geometry required of an advanced hydrofoil.
These dermal fi bers of the stratum compactum in the dorsal lobe occur in numerous
distinct layers. The layers are more complex than in other sharks and appear to refl ect a
hierarchical development in C. carcharias. The fi ber layer comprises a number of thick fi ber
bundles along the height of the layer, and the layers get thicker deeper into the stratum
compactum. Each of these layers alternates with a layer a single fi ber-bundle deep, a formation
thought to give stability to the stratum compactum and to enable freer movements of the
fi ber system. In tangential sections of the stratum compactum the fi ber bundles in the dorsal
lobe can be seen oriented, with respect to the long axis of the shark, at ∼55–60° in left- and
right-handed helices.
Due to the backward sweep of the dorsal lobe (∼55° to the shark’s long axis), the righthanded fi bers also parallel the lobe’s long axis. In the dorsal lobe, ceratotrichia are present
only along the leading edge (embedded within connective tissue), apparently as reinforcement.
Stratum compactum fi ber bundles of the ventral lobe, viewed in transverse section, lack the
well-ordered distinctive layers of the dorsal lobe. Instead, they occur as irregularly arranged
masses of tightly compacted fi ber bundles of various sizes. In tangential sections the fi ber
bundles are oriented at angles of ∼60°, generally in one direction, i.e., lacking the left- and
right-handed helical pattern. Tensile load tests on the caudal fi n indicate high passive
resistance to bending by the skin. The shear modulus G showed that the skin’s contribution
to stiffness (average values from three specimens at radians 0.52 and 1.05) is 33.5 % for the
dorsal lobe and 41.8 % for the ventral. The load tests also indicate greater bending stiffness
of the ventral lobe compared to the dorsal. The helical fi ber architecture near the surface of
the caudal fi n is analogous to strengthening of a thin cylinder in engineering. High fi ber
angles along the span of the dorsal lobe are considered ideal for resisting the bending stresses
that the lobe is subjected to during the locomotory beat cycle. They are also ideal for storing
strain energy during bending of the lobe and consequently may be of value in facilitating the
recovery stroke. Thus, the complex fi ber architecture of the caudal fi n and caudal peduncle
of C. carcharias provides considerable potential for an elastic mechanism in the animal’s
swimming motions, and consequently for energy conservation,” (Lingham-Soliar 2005b ).
Furthermore, it was additionally reported (Lingham-Soliar 2005c ), that “the
buoyancy may play a dominant role in larger white sharks by permitting slow swimming while minimizing energy demands needed to prevent sinking. In contrast,
hydrodynamic lift is considered more important in smaller white sharks. Larger
caudal fi n spans and higher lift/drag ratio in smaller C. carcharias indicate greater
potential for prolonged, intermediate swimming speeds and for feeding predominantly
on fast-moving fi sh. Meanwhile, slow-swimming search patterns of larger individuals are advantageous in seeking predominantly large mammalian prey. Such data
may provide some answers to the lifestyle and widespread habitat capabilities of
this still largely mysterious animal,” (Lingham-Soliar 2005c ).
7.1 Fish Fins and Rays: Diversity, Structure and Function
to present the description of specifi c dynamic locomotory structure that is formed
by the caudal peduncle and caudal fi n of the giant shark C. carcharias as follow:
“The caudal peduncle is a highly modifi ed, dorsoventrally compressed and rigid structure
that facilitates the oscillations of the caudal fi n. Its stiffness appears to be principally
achieved by a thick layer of adipose tissue that composes 28–37 % of its cross-sectional
area, reinforced by cross-woven collagen fi bers. The overlying layers of collagen fi bers of
the stratum compactum, oriented in steep left- and right-handed helices (∼65° to the shark’s
long axis), prevent bowstringing of the perimysial fi bers that lie just below the dermal layer.
Perimysial fi bers, muscles, and the notochord are restricted to the dorsal lobe of the caudal
fi n and comprise the bulk of its mass. Adipose tissue reinforces the leading edge of the
dorsal lobe of the caudal fi n and contributes to maintaining the ideal cross-sectional
geometry required of an advanced hydrofoil.
These dermal fi bers of the stratum compactum in the dorsal lobe occur in numerous
distinct layers. The layers are more complex than in other sharks and appear to refl ect a
hierarchical development in C. carcharias. The fi ber layer comprises a number of thick fi ber
bundles along the height of the layer, and the layers get thicker deeper into the stratum
compactum. Each of these layers alternates with a layer a single fi ber-bundle deep, a formation
thought to give stability to the stratum compactum and to enable freer movements of the
fi ber system. In tangential sections of the stratum compactum the fi ber bundles in the dorsal
lobe can be seen oriented, with respect to the long axis of the shark, at ∼55–60° in left- and
right-handed helices.
Due to the backward sweep of the dorsal lobe (∼55° to the shark’s long axis), the righthanded fi bers also parallel the lobe’s long axis. In the dorsal lobe, ceratotrichia are present
only along the leading edge (embedded within connective tissue), apparently as reinforcement.
Stratum compactum fi ber bundles of the ventral lobe, viewed in transverse section, lack the
well-ordered distinctive layers of the dorsal lobe. Instead, they occur as irregularly arranged
masses of tightly compacted fi ber bundles of various sizes. In tangential sections the fi ber
bundles are oriented at angles of ∼60°, generally in one direction, i.e., lacking the left- and
right-handed helical pattern. Tensile load tests on the caudal fi n indicate high passive
resistance to bending by the skin. The shear modulus G showed that the skin’s contribution
to stiffness (average values from three specimens at radians 0.52 and 1.05) is 33.5 % for the
dorsal lobe and 41.8 % for the ventral. The load tests also indicate greater bending stiffness
of the ventral lobe compared to the dorsal. The helical fi ber architecture near the surface of
the caudal fi n is analogous to strengthening of a thin cylinder in engineering. High fi ber
angles along the span of the dorsal lobe are considered ideal for resisting the bending stresses
that the lobe is subjected to during the locomotory beat cycle. They are also ideal for storing
strain energy during bending of the lobe and consequently may be of value in facilitating the
recovery stroke. Thus, the complex fi ber architecture of the caudal fi n and caudal peduncle
of C. carcharias provides considerable potential for an elastic mechanism in the animal’s
swimming motions, and consequently for energy conservation,” (Lingham-Soliar 2005b ).
Furthermore, it was additionally reported (Lingham-Soliar 2005c ), that “the
buoyancy may play a dominant role in larger white sharks by permitting slow swimming while minimizing energy demands needed to prevent sinking. In contrast,
hydrodynamic lift is considered more important in smaller white sharks. Larger
caudal fi n spans and higher lift/drag ratio in smaller C. carcharias indicate greater
potential for prolonged, intermediate swimming speeds and for feeding predominantly
on fast-moving fi sh. Meanwhile, slow-swimming search patterns of larger individuals are advantageous in seeking predominantly large mammalian prey. Such data
may provide some answers to the lifestyle and widespread habitat capabilities of
this still largely mysterious animal,” (Lingham-Soliar 2005c ).
7.1 Fish Fins and Rays: Diversity, Structure and Function