Fish Anatomy

Question 1

What is the structure of the gills? How does water flow over them?

Answer 1

Gills are paired, and located near the back of the head.

Cranially, they are open to the gullet. Caudally, they are open to the external environment.

Water flows continually over them through the mouth.

Each gill arch supports a pair of gill filaments (primary lamellae).

Each gill filament supports numerous secondary gill lamellae.

Gill rakers prevent extraneous material from entering gill filaments.

Secondary lamellae:
> Gas exchange
> Overlapping squamous epithelium
> Separated by pillar cells
> Scattered goblet cells

Question 2

How many gill arches do fish have on each side?

Answer 2

Four.

Question 3

What are the two main functions of gills?

Answer 3

1. Respiration and excretion of ammonia.
2. Obtain oxygen from the water.

Question 4

What are the 2 types of scales and which one is found in bony (teleost) fish?

Answer 4

1. Ctenoid scales (elasmobranch) - sandpaper finish
2. Cycloid scales (teleost) - smooth outer surface

Question 5

Do fish have an outer, middle or inner ear?

Answer 5

Fish only have an inner ear.

Question 6

What are the 4 parts of the fish ear and their characteristics?

Answer 6

1. Utricle - horizontal movement
2. Saccule - vertical movement
3. Lagena - part of the vestibular system
4. Ampulla - bulbous area that contains the cupula

Question 7

Where is the electric organ in marine and freshwater fish? What is its function?

Answer 7

Functions to detect electric fields; used for navigation, communication, defense, and sometimes incapacitation of prey.

Marine fish - located in the head
Freshwater fish - located in the tail

Question 8

What is the function of the lateral line?

Answer 8

Functions to detect wave movement in water.

Question 9

What are the different functions of the anterior and posterior kidneys?

Answer 9

The primary function is osmoregulation.

Hematopoietic “head” (anterior kidney) and excretory “tail” (posterior kidney).

Question 10

What are the 2 types of swim bladders, and describe how each works?

Answer 10

1. Physostomous swim bladder - connected to the gut; uses this connection to control the amount of gas in the swim bladder.
2. Physoclistous swim bladder - NOT connected to the gut; controls the amount of gas in the swim bladder via capillary gas exchange.

Question 11

What are the 2 hematopoietic organs in the fish?

Answer 11

Spleen and Kidney.

Question 12

What is the central lymphoid organ in the fish?

Answer 12

Thymus.

Question 13

Pyloric ceca

Answer 13

Thin, blind-ended tubes located at the hind end of the stomach.

Functions to secrete trypsin and other digestive enzymes.

Neutralizes the acidity of the chyme before it reaches the intestines.

Question 14

Operculum

Answer 14

Bony plate that protects the gills; hinged and has muscles attached to it to open/close.

Question 15

Hepatopancreas

Answer 15

Combination of pancreas and liver. Islands of pancreatic tissue scattered throughout the liver. Liver is not lobulated.

Question 16

Pseudobranch

Answer 16

Gill-like structure located under the dorsal operculum. Consists of a single gill arch with a single row of gill filaments.

Although function is unknown, it is possibly to provide well-oxygenated blood to the optic choroid and retina or to maintain blood pressure.

Question 17

Otolith

Answer 17

Ear stone; usually mineralized; can be used to age the fish.