Basic Fish Physiology Lecture

1. FISH PHYSIOLOGY
LITO A. APELO
Lecturer
Khabura Vocational College of Marine Science
Sultanate of Oman

3. Parts and Functions of Fish Organs
(External Organs)

4. Fins
 allow the fish to stay upright, move, and
maneuver in the water
https://www.youtube.com/watch?time_continue=55&v=-mC2VJ_Etm
The Evolution of Fins -
Fins originally evolved for locomotion, or thrust and
rotation in an aquatic environment. Over hundreds
of millions of years, fins have taken a variety of
shapes and forms providing separate functions
besides just locomotion.

5. FINS OF FISH

12. Rays
 Soft cartilage structure that supports the fins
of the fish.

14. Spine
Hard structure that supports
the fins and is used for
defense

16. Dorsal and Anal Fins
Balance and close quarters movements

17. DORSAL FIN
are located on the back. A fish can have up to three dorsal fins. The dorsal fins
serve to protect the fish against rolling, and assist it in sudden turns and stops.

18. ANAL FINS
The anal/cloacal fin is located on the ventral surface behind the anus/cloaca. This
fin is used to stabilize the fish while swimming.

19. Pectoral Fin
Allows to fish to dive and also
allows the fish to stay in one spot.

20. PECTORAL FINS
A peculiar function of pectoral fins, highly developed in some fish, is the creation
of the dynamic lifting force that assists some fish, such as sharks, in maintaining
depth and also enables the "flight" for flying fish.
In many fish, the pectoral fins aid in walking, especially in the lobe-like fins of
some anglerfish and in the mudskipper.
Certain rays of the pectoral fins may be adapted into finger-like projections, such
as in sea robins and flying gurnards.

21. Pelvic Fin
Balances and positions

22. PELVIC FINS
The pelvic fin assists the fish in going up or down through the water, turning
sharply, and stopping quickly.

23. Tail Fin
Helps to propel the fish

24. TAIL/CAUDAL FINS
The caudal fin is the tail fin (from the Latin cauda meaning tail), located at the end of
the caudal peduncle and is used for propulsion.

25. Lateral Line
Helps the fish detect vibration, sensors, and helps the fish to find food and
to navigate to avoid predators.
https://www.youtube.com/watch?v=mqraFwQF1iU

26. LATERAL/TACTILE LINE

27. TACTILE SENSATION WITH
LATERAL LINE ORGANS
Fish are aquatic animals with great diversity. There are over 32’000
species of fish, making it the largest group of vertebrates.
Most fish possess highly developed sense organs. The eyes of most daylight
dwelling fish are capable of color vision. Some can even see ultra violet
light. Fish also have a very good sense of smell. Trout for example have
special holes called “nares” in their head that they use to register tiny
amounts of chemicals in the water. Migrating salmon coming from the
ocean use this sense to find their way back to their home streams, because
they remember what they smell like. Especially ground dwelling fish have
a very strong tactile sense in their lips and barbels. Their taste buds are
also located there. They use these senses to search for food on the ground
and in murky waters.
Fish also have a lateral line system, also known as the LATERALIS
SYSTEM. It is a system of tactile sense organs located in the head and
along both sides of the body. It is used to detect movement and vibration
in the surrounding water.

28. HOW DOES IT FUNCTION?
• Fish use the lateral line sense organ to sense prey and predators,
changes in the current and its orientation and they use it to avoid
collision in schooling.
• The lateral line sensory organ is necessary for fish to detect their
prey and orient towards it. The fish detect and orient themselves
towards movements created by prey or a vibrating metal sphere even
when they are blinded. When signal transduction in the lateral lines is
inhibited by cobalt chloride application, the ability to target the prey
is greatly diminished.
• The dependency of fish on the lateral line organ to avoid collisions in
schooling fish was demonstrated by Pitcher et al. in 1976, where they
show that optically blinded fish can swim in a school of fish, while
those with a disabled lateral line organ cannot.

29. ANATOMY EXPLAINED…..
The lateral lines are visible as two faint lines that run along either side of the fish
body, from its head to its tail. They are made up of a series of mechanoreceptor
cells called neuromasts. These are either located on the surface of the skin or are,
more frequently, embedded within the lateral line canal. The lateral line canal is a
mucus filled structure that lies just beneath the skin and transduces the external
water displacement through openings from the outside to the neuromasts on the
inside. The neuromasts themselves are made up of sensory cells with fine hair
cells that are encapsulated by a cylindrical gelatinous cupula. These reach either
directly into the open water (common in deep sea fish) or into the lymph fluid of the
lateral line canal. The changing water pressures bend the cupula, and in turn the
hair cells inside. Similar to the hair cells in all vertebrate ears, a deflection towards
the shorter cilia leads to a hyperpolarization (decrease of firing rate) and a
deflection in the opposite direction leads to depolarization (increase of firing rate)
of the sensory cells. Therefore the pressure information is transduced to digital
information using rate coding that is then passed along the lateral line nerve to the
brain. By integrating many neuromasts through their afferent and efferent
connections, complex circuits can be formed. This can make them respond to
different stimulation frequencies and consequently coding for different parameters,
like acceleration or velocity

30. The lateral lines are visible as two faint lines that run along either side of
the fish body, from its head to its tail.

31. They are made up of a series of mechanoreceptor cells called
neuromasts.
The lateral line canal is a mucus filled structure that lies just beneath the
skin
Mucus refers to the viscous, slimy and slippery substance that is secreted
by the glands. Like a jelly…
This can make them respond to different
stimulation frequencies and consequently coding
for different parameters, like acceleration or
velocity

32. FISH LATERAL LINE EXPLAINED..
https://www.youtube.com/watch?v=mqraFwQF1iU

33. Gills
Supply the fish with oxygen that they need from water. Gills are one of the
most important parts on a fish.

34. Gill Raker
Strain the aquatic micro structure for use by the fish.

35. Barbels
Bottom feeders, they only
taste and feel

36. Scales
Protective cover on fish that prevents injury or disease also indicates age.

37. Catfish-Bullhead
Tough skin and scales
Trout/Carp

38. Mucus Covering
Protection from infections and disease. Also helps in swimming, lowering
friction in the water.

39. Nostrils
Are for smell