Chondrichthyes
Hydrodynamics
 Body
shape
 Sharks typically have an elongate fusiform
body (rounded and tapering at both ends).
This body shape reduces drag and
requires a minimum of energy to swim.
Swimming is essential for buoyancy.
Caudal Fin = Propulsion
 Unlike
most bony fishes, the upper lobe of a
shark's caudal fin is larger than the lower
lobe. As the caudal fin moves back and
forth to propel the shark forward, it also
moves upward. As the caudal fin continues
to lift, the shark's head points down. The
overall effect of the motion of the caudal fin
results in a forward and downward motion
Pectoral Fins = Lift
 The
pectoral fins compensate for this
downward motion. One function of the
rigid pectoral fins is to provide lift in the
forward region of the shark's body. This
counteracts the overall downward force
caused by the caudal fin and results in
horizontal passage through the water.
Pelvic Fins = balance
 Also
Paired
 In males the median part of the pelvic fin is
modified to form a clasper which is used in
copulation.
Swimming Speed
 Generally
sharks swim at speeds less than
5 kph (about 3 mph). For the most part,
bottom-dwelling sharks are slowswimming.

Makos are among the fastest sharks,
reaching speeds up to 48 kph (30 mph).
Characteristics

1. Endoskeleton entirely cartilaginous.
This is interesting considering they evolved
from ancestors that had bone.
Notochord present but reduced
Vertebrae separate and complete
 2. Brain of two olfactory lobes, two optical lobes,
two cerebral hemispheres, cerebellum, and
medulla oblongata.
 3. Circulatory System 2 chambered heart.
 4. Respiration: through gills, they have 5 to 7
pairs.
Placoid Scales
 5.
Skin with placoid scales.
Teeth are modified placoid scales that can
be replaced on a regular basis.
Scales Help Swimming?
As a shark swims, placoid scales
may create a series of vortices or
whirlpools behind each scale.
This enables a shark to swim
efficiently.
Digestive System with stomach and
intestine with a spiral valve.
 7. Body fusiform with heterocercal
caudal fin.
8. Mesonephric Kidney and rectal
gland: the rectal gland helps control
salt concentrations in the blood by
secreting a colorless fluid high in
sodium chloride.
9. No swim bladder or lung. Sharks
have high amounts of lipids fats in
their liver that help them be bouyant.

6.
 10.
Separate Sexes
 All sharks have Internal Fertilization but
care of young varies considerably.
 Oviparous: eggs released by females,
development outside the mother.
 Ovoviviparous: eggs develop inside
mother without nourishment from parent.
Hatch inside mother or immediately after
laying.
 Viviparous: eggs develop inside with
nourishment, offspring born alive already
with development.
 11.
Lateral Line: part of its nervous
system. Detects changes of current in the
water, and movement of some objects in
the water.
 Consists of long recessed grooves along
the side of the shark. Concentrated at the
head area and extending posterior to the
tail. The groove has a series of
neuromasts.
 Navigation is the primary function of the
lateral line system.

12. Ampullary
Organs of Lorenzini
 Detect bioelectric
fields.
 Located in the head
around the eye.
 Enables them to detect
prey that is even buried
in the sand.