Fish I

Question 1

What are fish

Answer 1

They are a grade not clade

Paraphyletic group

Question 2

Name the three main extant groups of fish

Answer 2

Agnatha (cyclostomes)
Chondrichthyes
Osteichthyes (Actinopterygians, Sarcoptergyians)

Question 3

What are the 2 extant jawless agnathans

Answer 3

Hagfish and lampreys

Question 4

What are the 5 characteristics of agnathans

Answer 4

They are jawless fish so:
jawless (obviously)
absence of paired fins
Presence of notochord in larvae and adults
seven or more gill pouches
2 chambered heart

Question 5

Provide a brief description of hagfishes (can draw diagram)

Answer 5

Many pairs of tidal gill pouches
no jaws
long thin bodies
simple myotomes
tail fin
feature rasping tooth plates that move apart together to eat into dead fish

Question 6

list three somewhat interesting features of hagfish

Answer 6

They are benthic marine scavengers that eat into dead fish
Can exude large quantities of mucus (myxine glutinosa)
In order to shed the slime produced, can tie body into knot that can move up and down the body

Question 7

What are the archaic features of hagfish?

Clue: features from diagram included

Answer 7

They have a stiff fibre-sheathed notochord but no vertebrae
many pairs of tidal gill pouches
single nasal capsule
only ONE semi-circular canal in statocyst
myotomes not divided into D and V blocks
No pepsin or HCl in stomach
Segmental excretory funnels in trunk
no paired fins
long thin body

Question 8

What are lampreys?

Answer 8

Surviving agnathans
Long and cylindrical marine fish with vertebral structures

they are ectoparasitic on other fishes - stick onto them by suction - they rasp the flesh of their prey with oral tooth plates

Question 9

Describe gill ventilation in lampreys

Answer 9

The tidal ventilation of gill pouches allows the lamprey to remain attached and breathe while rasping away with muscular tongue - eating into prey
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Question 10

What are the archaic features of lampreys

Answer 10

Cartilaginos incomplete vertebrae around the notochord
many pairs of tidal gill pouches
single nasal capsule
only TWO semi circular canal in statocyst
myotomes not divided into d and v blocks
no pepsin or hcl in stomach
segmental excretory glomeruli in trunk
no paired fins
long thin trunk

Question 11

Describe the anadromous life cycle of lampreys

Answer 11

adults live in oceans or big lakes
ascend rivers or streams to breed. temperature triggered migration
males and females construct nest
females lay eggs that are fertilised by males
larvae differ dramatically from the parents. They leave the nest, and currents carry them downstream
larvae burrow themselves into mud and spend a few years as filter feeders
undergo metamorphosis
produces parasitic juvenile

Question 12

Why was the evolution of jaws a major step in fish evolution

Answer 12

The change from agnathans to gnathostomes led to:
new feeding habits: herbivory, predation
ability to manipulate objects (build nests, grasp mates during mating, care for young etc)

Question 13

How else are gnathostomes more derived than agnathans? (7 things)

Answer 13

A duplication of Hox gene complex
paired fins(that allow for increased manoeuvrability)
well developed lateral line
third semi circler Canal in inner ear (better 3D orientation
more complex vertebrae
ribs
two nostrils

Question 14

Describe how the evolution of jaws may have come about

Why modify the gill arch and not cartilage surrounding mouth?

Answer 14

gnathostomes are active - high metabolic demands
derived feature -> powerful mechanism for pumping water over gills

the mandibular gill arch evolved into protojaws, playing a role in forceful ventilation.
pharynx can be filled and then emptied by spreading and compressing the rays of the arches

cranial nerves become associated with jaw (e.g. dogfish jaws)

Question 15

Describe cells involved in the detection of fluid movement

see diagram!

Answer 15

neuromasts are basic displacement sensitive cells

they are excited by bending in one direction and inhibited in the opposite direction

Question 16

Talk about the neuromasts

Answer 16

Present on surface of all fish

they are superficial: naked and set on surface along body

canal: set in formal canals opening to the outside

Question 17

What is the difference between superficial and canal neuromasts

Answer 17

Canal neuromasts: low pass filter

different functions; high vs low frequency ?

Question 18

What are statocysts and where are they located?

Answer 18

The craniate head contains paired statocysts in the inner ear
statoliths (ossicles) give up and down info
also displaced by acceleration
swirling in semi circular canals is caused by angular acceleration
hagfish have one semicircular canal
and lampreys have two

Question 19

What do three paired canals allow for? (we have three paired canals)

Answer 19

Allow discrimination of rotational accelerations in yaw, pitch and roll axes as well as translational accelerations in any plane

Question 20

Describe the early appearance of paired fins

Answer 20

Early Devonian fish acanthodian fish : Euthacantus had paired rows of spiny finlets between the pharynx and anus

in the related acanthodes, reduced to discrete paired pelvic and pectoral fins

Question 21

Explain the locomotor function of fins

Answer 21

Increase manoeuvrability and stability
unpaired dorsal and anal fins control tendency to roll or yaw
paired pectoral and pelvic funs control pitch and act as brakes

Question 22

non locomotor functions of fins?

Answer 22

Spiny fins are used in defence - can evolve to inject poison when combined with glandular secretions e.g. in lion fish

colourful fins used to send signals to potential mates, rivals, and predators.

Question 23

What are the two forces acting on fish while swimming

Answer 23

Thrust and drag

Question 24

There are different fish swimming modes

Answer 24

Body or caudal fin swimming (greater thrust and acceleration)

median or paired fish swimming (greater manoeuvrability)

Question 25

describe anguilliform swimming (eel)

Answer 25

The travelling wave throughout the fish’s body pushes water backwards. the wave increases in amplitude as it is pushed backwards . the force generated (push) increases from head to tail as a result.

the equal and opposite reaction force to the push – the forces can be resolved into longitudinal thrust components and sideways components .

along the body , the thrust components summate, but the sideways components cancel out .

Question 26

describe carangiform swimming (trout)

Answer 26

Amplitude of undulation is small at the head and large at the tail - therefore major forces are produced at or near the tail, and the middle parts of the body do not contribute much to thrust

Question 27

what is vortex generation and shedding

Answer 27

swimming involves generation and shedding of vortices, forming a train

a vortex has mass and velocity – the ???

Question 28

Thunniform swimming (tuna)

Answer 28

oscillation is largely confined to the tail (hinge at beginning of tail). The tail acts on a large volume of water

propeller efficiency - if the mass of water moved backwards by the fish exceeds that of the fish, water will move backwards slowly but the fish moves forwards more rapidly.

Tail acts on a large volume of water so propeller efficiency is high!

Question 29

What are the main forms of drag?

Answer 29

Skin friction between fish and boundary layer (mucus, scale adaptations)

pressures formed in pushing water (fish shape)

energy lost in vortices formed around the fins