Forensic Biology & Its biological significance.pdf
Shark basics
1.
2. Sharks are cartilaginous fish
◦ Meaning their skeleton is made mainly of cartilage
Belong to the class Chondrichthyes
(cartilaginous fish)
Subclass Elasmobranchii (Elasmobranchs)
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
10.
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
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
27.
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
