Lecture 16- Fish Characteristics 1

Question 1

fins are divided into:

Answer 1

1. median fins (dorsal, caudal and anal) 2. Paired fins (pectoral and pelvic)

Question 2

Answer 2

Question 3

Pectoral and pelvic fins are supported by what?

Answer 3

bony pectoral girdles

Question 4

whats the general difference between pectoral and pelvic fins?

Answer 4

Pectoral fin placement is relatively similar amongst fishes as is their use (primarily turning). However, pelvic fins are variable in position.

Question 5

what is the difference between Malacopterygian and Acanthopterygians?

Answer 5

Mala fishes are soft rayed (trou and herring) with abdominal pelvic fins. These fin placement is better for maintaining a straight course using less energy.

Acanthopterygian fishes are spiny-rayed (perch) with thorasic (below pectoral fins) or jugular (anterior to pectoral fins) pelvic fins (cod). Fin placement is more manueverable especially at low speeds

Question 6

what are the two main types of caudal fins?

Answer 6

1. homocercal- upper and lower lobes are equal
2. Heterocercal- upper and lower lobes not equal (more primitive)

Question 7

what is the primary function of the dorsal fin?

Answer 7

Dorsal fins come in several shapes and sizes but the primary function of all is as a rudder/brake

Question 8

all fins are supported by one of 3 types of structures: describe all 3

Answer 8

1. ) soft rays: which are segmented, with bilateral symmetry and are often branched. this occurs in soft-rayed fishes (malacopterygian) and spiny-rayed fished (acanthopterygians)
2. ) Spines: which are unsegmented, not bilateral or split at the ends. Occur only in true spiny-rayed fishes
3. ) Spinous soft ray: which are unsegmented (like a spine) but bilateral( like a ray). Occur on in some soft rayed fishes (catfish) usually as the first spine in an otherwise soft rayed fish

Question 9

like other vertebrates, fish skin is composed of what two layers?

Answer 9

1. epidermis
2. dermis

Question 10

why is the epidermis important in fish?

Answer 10

the epidermis is a layer of active cells that produce a layer of mucus and other secretions

Question 11

describe the 3 important roles mucus plays in a fishes life?

Answer 11

1. Important to reduce drag: important for all fish but particularly ambush predators like a pike.
2. Parasite/pathogen protection (prevent infection): Mucous is always sloughing off and takes external parasites with it.
3. Reduces water movement through the integument: extra water proofing

Question 12

where is poision produced in a fish?

Answer 12

Poisons are produced in glands within the epidermis and are often associated with spines to allow delivery to the victim.

Question 13

what is special about catfish skin? an example of yet another role the epidermis plays in a fishes life.

Answer 13

the epidermis also contains sensory structures including taste buds and neuromasts of the lateral lines. Some catfish actually contain more taste buds outside their mouth then in.

Question 14

what is on the epidermis of a fish that acts as an alarm for other fish?

Answer 14

club cells! when club cells are ruptured they release a substance that is an alarm cue to the other fish in the area and they know a predator interaction went down

Question 15

what does the dermal layer provide and what does it contain?

Answer 15

the dermal layer provides mechanical support and protection as well as contains connective tissue, scales, and pigment cells for colour

Question 16

scales are very —— to each species

Answer 16

unique/specific

Question 17

scales have been modified in evolution to become what 5 things?

Answer 17

1. fin rays/spines
2. Dermal bones of the skull
3. Lateral line scales
4. Armour pates (stickleback)
5. Absent (catfish)

Question 18

describe placoid scales:

Answer 18

a characteristic of chondrycthyes. Consits of a flattened regular plate with a spine protruding from the surface. The cone is composed of dentine with a pulp cavity supplied by blood. Outer layer composed of vitrodentine.

Question 19

describe cosmoid scale:

Answer 19

These scales ccur in extinct and extand sarcopterygian fishes. May have arose from fusion of placoid scales. Composed of 2 layers of bone covered with cosmine

Question 20

describe ganoid scale

Answer 20

Occur in chondrostei (bichers, reedfish, and stugeon)

They are modified cosmoid scales, cosmine is replaced by actual dentine and rhomboidal in shape. Modified in strugeon to form large plates called scutes

Question 21

describe cycloid/ctenoid scales

Answer 21

Occur in teleost fishes (the most derived fishes). originated as a modified ganoid scale with a thinning of the dermal plate. Allows greater flexibility and easier movement but less protection. Ctenoid scales have ctennii on posterior border and are the more derived of the two scale types

Question 22

describe the two origins of colour in fish:

Answer 22

1. colour can come from one of the three types of pigmented cells in the dermis
   - cartenoids: yellow, organge, red
   - melanin- black/brown

Guanine: white.silver

2. Colour can be tricks of structure and reflection
   - green/blue: structural colours produced by reflection and refraction of light by skin and scales

Question 23

describe the two ways fish are able to change colour

Answer 23

1. Morphologically: fish can change the number of pigment cells in response to the environemnt
   . These changes takes days to occur as the cells have to actually be created or destroyed.
2. Physiologically: the chromatophore pigments responsible for colour may be under nervous and hormonal control. These can change in seconds if under nervous system control. Cells under hormonal control change over hours or days

Question 24

The use of colour in fish can be broken into two groups:

Answer 24

1. Concealment: counter shading. Fish reflects light roughly equivalent to the background against which it is veiwed. Background matching is acheived through hormonal or nervous input.
2. ) Advertisement: aposematism- colour is used as a warning

Mimicry- attemption to resemble a larger or more dangerous animal

Species or gender recongtion

social interactions