This document provides an overview of fish anatomy. It begins by stating that fish are cold-blooded vertebrates that breathe through gills and move using fins, with over 30,000 species ranging greatly in size. The body is then divided into three main regions: the head, trunk, and tail. Key external features of the head are described, including the mouth, eyes, nostrils, scales and fins. The trunk contains organs and features like the lateral line and openings for gills, fins, anus and urogenital areas. Finally, the tail region ends at the anus and contains the caudal fin, which can vary in shape between species. Common scale types and their distribution patterns are also outlined.

1. Fish Anatomy
By
Prof. Dr. Abdelmohaimen Mostafa Saleh
Professor of Anatomy & Embryology
Assiut University

2. Student Learning Objectives
.1. Introduction
2. External features of the typical fish.
3. Identify common freshwater fish species
found in South Carolina waters.
4. Identify common saltwater fish species
found in South Carolina waters.
2

3. 3
 Fish are cold-blooded, vertebrate that
breathe with gills and move with fins. They are
the most numerous vertebrates more than
30,000 species
 smallest
 Philippine Island Goby – 1/3”- 1/2”
 largest
 Whale Shark – 50’ and several tons
 INTRODUCTION:

4. 4
Anatomically, The body of fishes is divided into 3
regions: head, trunk and tail.
General external features of the fishes
Head Trunk Tail

5. General external features
Head Trunk Tail

6. 6

7. A- Head region:
7
• The head extends from the tip of upper jaw to
caudal margin of operculum.
• It includes mouth, snout, eyes, cheek,
operculum, chin, barbels, nostrils, spine , and
sensory canals .

8. 8
** Features of the head :
1- Mouth:
It has different positions:
a) Inferior
b) Subterminal
c) Terminal
d) Superior
The mouth may be:
A- protrusible
B- nonprotrusible.

9. Terminal Superior

10. Labial fold
sensory canals and
pores . spines

11. 11
2- Eye:
The fish has two eyes without eye lids
3- Snout:
A region between the eye and the tip of the
upper jaw
4- Nostrils:
They consists of a blind sa c on each side which
has a sensory function. They have no
respiratory function.
5- Cheek:
A region between the eye and the
preopercle.
6- Barbels:
They are sensory structures which
carry tactile and chemical
receptors.
They are not found in all fishes
and have sensory function.

12. 12
7- Spines:
As a source of defense
8- Sensory canals:
They are recognized by rows
pores in the skin and have
sensory function.
9- Operculum (Gill cover):
It covers the gill cavity.
10- Folds:
The folds not found in all
They surround the mouth to
increase the surface area.

13. 13
2-Trunk region:

14. The trunk extends from the caudal margin of the
operculum to the anus.
-It has the following features:
1- Nuchal region:
-It is the dorsal surface just behind the occiput.
2- Isthmus:
-It is the most anterior ventral part of the body that
extends forward below and between the gills
openings.
2-Trunk region

15. 3- Lateral line:
- It is a continuation of the sensory canals of the
head, along each side of fish.
- It is usually single line ( may be an open groove
,or a row of pores in the skin).
- Lines may be multiple or variously reduced.
- It has sensory function.

17. 3- Gill openings:
They are typically in a lateral position covered by
operculum.
4- Fins:
* Single:
Dorsal fin - Anal fin - Caudal fin
** Paired:
Pectoral fins - Pelvic fins
5- Anus:
Represents the opening of the gut in most fishes.

18. 18
6- Urogenital opening:
Lies caudal to the anus, the urinary opening may
be separate from and behind the genital pore.
Some fishes have:
A- Combined urogenital opening lies behind anus.
B- The urinary opening is separated and lies
caudal to the genital opening.
C- There is a cloaca which receive the openings of gut
genital and urinary systems
6- Cloaca:
Found in some fishes (shark) and receives the
openings of the gut, the urinary and genital
systems.

19. 19

20. 7- Gill openings:
-They are in the lateral position and
covered by operculum
8- Fins:
-They will discuss in a separate
chapter.

21. Body forms of fishes:
The bodies of most fishes have different forms as:
(aFusiform . b) Compressiform
c) Depressiform . d) Filiform .
e) Taeniform . f) Sagitiform .
g)Globiform . h) Angwilliform .

23. C- Tail region:
 Begins at the anus and extends caudally.
 The narrow part of the fish just cranial to tail fin
is called the peduncle.

24. Fins -The fins are the most characteristic features on
the fish body.
 They are fold of skin strengthed by rays which may
be soft or modified into spines.
- -They are Classified into 2 groups:
1- single fins: dorsal , caudal and anal .
2- paired fins: pectoral and pelvic .

25. Position: They lie on sides of trunk
just behind the gill openings.
Function :
1-Make stability.
2-Change direction.
3-Bear taste buds(sensory function).
Modifications :
1-Act as fore limb especially in fish which live in deep
sea.
2-May have finger like projection which has sensory
function.
3-Sometimes act as a wing, in flying fishes and fishes
have habbit of jumping
1-Pectoral fins:
A- Paired fins

26. a- Finger like projections b- Wing-like
Fig.7: Modified pectoral fins
c-As a fore Limb

27. 2-Pelvic fins:
Position: They have different positions:
1- jugular: cranial to pectoral fins .
2- thoracic: behind the pectoral fins .
3- subabdominal: cranial to the anus.
4- abdominal : caudal to the anus.
Function:
1- Stability (balance).
2- braking.
3- sexual intercourse .

28. A- Abdominal B- Subabdominal
C-Thoracic D- Jugular

29. 29
Single Fins
It extends along the back of the fish.
It may be:
- Divided into two or three separate fins
- Single and small or may not found .
Function
- Balance
- Change the direction of motion
- Undulating movement when it extends
along the back .
Modification
- Sucking disc → help in absorption
- Spines → for defense
1- Dorsal fin

30. A- Sucking disc
A- Sucking disc
B- Spine

31. 3- Anal fin:
Positions: -It lies caudal to the anal opening
Number:
-Single (most fishes).
-more than one anal fin( Few fishes ).
Function: - Helps in copulation

32. Position:
It is the terminal fin.
Size:
It is small in size in most fishes.
Function:
It changes the direction of motion as follow.
1-speediest fishes have lunate fin.
2-strong swimmers have other shapes of fins.
They are slower than the previous group.
3-weak swimmers have small caudal fin.
3. Caudal (Tail) fin:

33. A- Round B-Truncate
D- Lunate
C- Emarginate
E-Forked

34. Scales:
Definition:
-Translucent plates of dermal origin that
project into the epidermis.
Function:
-Have protection function.

35. Types:
-There are 4 major scale types :
1- Cycloid scales:
-Oval with smooth borders .
2- Ctenoid scales:
-Ridged scales.
3- Ganoid scales:
-It consists of a bony basal layer( of dentine) and an outer layer of ganoine. (an
inorganic bone salt).
4-Placoid scales:
-Flattened rectangular base plate embedded in the fish, and variously developed
structures, such as spines, project posteriorly on the surface.

39. Distribution patterns of scale:
- Distribution patterns have some clinical
significance ,dictating handling and treatment
procedures.
1- Scaleless fishes:
-These fishes don’t contain scales
2 - Lightly scaled fishes:
N.B: the fishes of number 1 and 2 can be much
more sensitive to drugs and toxins in water .
3- Very finely scaled fishes:
-These fishes are easily damaged.
4- large scaled fishes:
-These fish can be very difficult to
inject.
-large scales may complicate surgical
efforts.

40. 40