Shark basics

2.  Sharks are cartilaginous fish
◦ Meaning their skeleton is made mainly of cartilage
 Belong to the class Chondrichthyes
(cartilaginous fish)
 Subclass Elasmobranchii (Elasmobranchs)

3.  Basic anatomy

4.  5 major fins.
 Dorsal
 Pectoral
 Pelvic
 Anal
 Caudal (Tail)

5.  Dorsal fins – stabilizing
 Pectoral fins – lift and steering
 Pelvic fins – stabilizing (clasping in males)
 Anal fins – stabilizing
 Caudal fins – forward momentum (propulsion)

6.  Most sharks have heterocercal tails
 The upper lobe is larger than the lower lobe
 And they use a carangiform swim motion

7.  Most male cartilaginous fish, including
sharks, have a modified pair of pelvic fins
called the claspers
 The claspers, or intromittent organs, are used
to deliver sperm from the male to the female

8.  Most sharks have 5 gills,
though some have seven
 Unlike bony fish, shark
gills are not protected by
any covering
 They allow for gas
exchange in the water
◦ Allow sharks to breathe

9.  When sharks are on the ocean floor they are
able to breathe using spiracles
 Spiracles are a pair of openings just behind
the fish's eyes that allow it to draw
oxygenated water in from above.
 The spiracles aid the fish in breathing even
when it is lying on the ocean bottom or
buried in the sand

11.  Sharks have very thick skin covered in dermal
denticles which gives it the feel of sandpaper
 These dermal denticles reduce turbulence
when sharks are in motion

12.  The skin of female sharks is usually 3-4
times thicker than that of male sharks
 Most forms of mating involve biting, so the
thicker skin is necessary to protect the
internal organs

13.  The skin usually demonstrates
countershading
◦ Coloring with a dark dorsal side and a light ventral
side
◦ Aids in camouflage

14.  Shark teeth are embedded in the gums, not
directly attached to the jaw
 Shark teeth are constantly replaced and are
produced in rows
◦ Most sharks have 3 rows
◦ Teeth are replaced on at a time, not a whole row at
a time

15.  Shark teeth come in many different forms
 The shape directly reflects the common prey
of that shark species

16.  Sharks have well-adapted
eyes
 Unlike bony fish, sharks
can dilate and constrict
their pupils
 They also have Tapetum
Lucidum, a lining in the
back of the eye that helps
detect light in dim or dark
areas

17.  Sharks also use their ampullae of Lorenzini to
detect predators and prey, and to aid in
navigation
 The ampullae of Lorenzini are small
electroreceptors located on the underside of
the rostrum

18.  Sharks are able to detect pressure changes in
the water, like all fish, by using their lateral
line
 Each pore (neuromast) contains a
neuroreceptor used to detect
motion/pressure changes

19.  Sharks have a strong
sense of smell, enables by
nostrils
 Their olfactory sensors
are located in the short
duct between the anterior
and posterior nasal
openings
 Some species can detect
as little as one part per
million of blood in
seawater

20.  Sharks have the ability to determine the
direction of a given scent based on the timing
of scent detection in each nostril
 Similar to how mammals hear

21.  Sharks have a sharp
sense of hearing
 A small opening on
each side of the
head leads directly
to an inner ear

22.  Final external structure is the cloaca
 The cloaca is an opening near the posterior
end of the shark
 It is the opening for the digestive (solid
waste), excretory (liquid waste) and
reproductive system (gametes)

23.  Sharks have a 3 loved liver filled with an oil
called squalene that helps them stay afloat

25.  Sharks’ circulatory systems are powered by a
two chambered hearts

26.  Sharks have a complete digestive tract;
beginning at the mouth and ending at the
cloaca
 Many sharks have the unique ability to
completely regurgitate their food

28.  Inside the intestine is a specialized structure
called a spiral valve, which helps with
digestion by increasing surface area

29.  The spleen of the shark is triangular in shape
and located near the posterior end
 The spleen is part of the circulatory system
 It is involved in the production, degradation,
and storage of red blood cells and is integral
to the shark’s immune system

30.  The shark has a small pancreas located on
the under side of the spleen
 The pancreas should consist of two lobes
 It provides secretions needed for digestion

31.  The reproductive organs are located near the
anterior end of the shark
 They occur in pairs; testes in males, ovaries
in females
 Connective tubes allow the reproductive cells
to travel from the organs to the cloaca