Lecture 4

Question 1

What features have bony fish evolved to now be able to have a wide range of body shapes?

Answer 1

. Gas bladder

. Their ability to be neutrally buoyant

Question 2

Bony fish have Operculum. What are these and how are they useful?

Answer 2

Operculum cover the gills so that they are not exposed directly to the environment and do they have more control of he flow of water over their gills

Question 3

What are Otoliths?

Answer 3

They are stony concretions situated in part of the war system at the base of the brain

Question 4

How are otoliths useful?

Answer 4

They carry a complete record of fish growth as they are deposited gradually through life, so it is good for ageing the fish (grow with the animal).
The shape of the large otoliths is species dependant/ species specific (diagnostic). Can identify the prey species in another animals faeces using these (and the size and age of the fish)

Question 5

What are the 4 types of fish scale?

Answer 5

. Placoid
. Cosmoid
. Ganoid
. Cycloid/ ctenoid

Question 6

Describe the placoid scale type and give an example of a type of animal that has this type of scale

Answer 6

Dentine and enamel and are essentially homologous with teeth. They are in sharks

Question 7

How do different types of scales differ?

Answer 7

They have different structures and different compositions

Question 8

Describe cosmoid scales and give an example

Answer 8

. Probably evolved from the fusion of placoid scales 
. Consist of two basal layers of bone:
- inner layer of dentine-like cosmine 
- outer layer of vitrodentine 
. Are seen in lungfish

Question 9

Describe Ganoid scales and give examples of where they are seen

Answer 9

. Usually rhomboid in shape
. Have articulating peg and socket joints between them. so they articulate between each other and this produces a very substantial armour for the animal. So the scales are interlinked
. Modified cosmoid scales
. Consist of a bony basal layer, a layer of dentine, and an outer layer of ganoine (an inorganic bone salt)
. Are seen in Bowfin and Sturgeon

Question 10

Describe cycloid/ ctenoid scales and give examples

Answer 10

. In the majority of teleost fish (these scales are thinner than the other ones)
. Cycloid are found in e.g. trout and herring
. Ctenoid are found in e.g. sole and perch
. Cycloid and ctenoid scales consist of two main regions:
- a surface bony layer, composed of an organic framework impregnated with calcium based salts
- a deeper fibrous layer composed mainly of collagen
. Grow throughout the fishes life
. They provide a growth record of the fish and may also show spawning

Question 11

How do bony fish take water into the mouth? How do they expel the water? If they are travelling long distances what can the fish do to aid themselves and save energy?

Answer 11

By expanding the buccal chamber, with the operculum closed, that allows water to be dragged in through the mouth into the buccal cavity. Then they close the mouth and contract the buccal cavity and that forces water out though the operculum chamber- so this is now an active process (so it costs energy). Fish that travel long distance can go back to the primitive passive process to save energy

Question 12

What is the gas bladder (previously known as the swim bladder)?

Answer 12

A gas filled sac located in the dorsal region of the body cavity

Question 13

Before the evolution of the gas bladder how were the animals lives different?

Answer 13

They had to keep moving to maintain their buoyancy

Question 14

The gas bladder volume can be varied, what does this mean for the fish?

Answer 14

It’s volume can be varied to increase or decrease buoyancy

Question 15

How do Physostomous swim bladders (more primitive) work?

Answer 15

A connection is retained between the swim bladder and the gut, allowing the fish to fill up the swim bladder by ‘gulping’ air. Excess gas can be removed in a similar manner. (these ones are essentially an outgrowth from the gut and it is a simple sort of air air- what they found was that the fish can go up to the surface, take a gulp of air and force it into the airwave. They can control the amount of air in the ace by gulping in more or releasing/ burp it-controlling their buoyancy)

Question 16

How do physoclistous swim bladders (more advanced) work? Why is this an advantage?

Answer 16

The connection to the digestive tract is lost (so these organs are no longer filled by filling- it is introduced via a gas gland). Fish either have to rise to the surface to fill up their swim bladders or introduce gas (usually oxygen) to the bladder to increase its volume and thus increase buoyancy.
Pressure changes with depth due to changes in volume and therefore any fish that gulps air is at a disadvantage

Question 17

What allows gas to be trapped in the swimbladder in both physostomous fish and phyoclistous fish?

Answer 17

Both have a gas gland with a rete mirabile (blood supply), a counter-current multiplier arrangement of capillaries, which allows gas to be trapped in the swimbladder

Question 18

Describe the mechanism for how gas becomes trapped in the swimbladder of both physostomous and physoclistous fish

Answer 18

In the swimbladder wall are guanine crystals which makes it impermeable to gas- so any gas in the swim bladder is held there and cannot get out. The only way it can get in and out is through the gas gland which has the counter current mechanism- so CO2 is constantly put into the arteriolar blood this means that we have a root shift because the CO2 lowers the pH, has a root shift in the oxygen saturation curve- so it makes blood less able to hold into oxygen- so as the blood goes into the swim gland it loses the oxygen so then it can go into the laymen and expand the swim bladder- so can control the amount by controlling the blood flow

Question 19

Fish move by a variety of means, what is the simplest? What do they quickly develop?

Answer 19

Passive drifters. They quickly develop the capability for active, directed movement

Question 20

How do most fish swim forward/ backward?

Answer 20

They utilise rhythmic undulations of their bodies or fins

Question 21

What does the stiff vertebral column in fish provide?

Answer 21

Compression resistance

Question 22

Fishes occur in a wide variety of body shapes so there is considerable variation in how they swim.these can be divided into 4 basic types of locomotor types. What are these?

Answer 22

. Anguilliform (eel-like)
. Carangiform/ subcarangiform (make up most of the fish)
. Ostracoderms (animals that have a very rigid body form)
. Swimming with the fins

Question 23

How are fish characterised into the 4 locomotor types?

Answer 23

By which body parts are involved in propulsion

Question 24

What does undulation mean in fish movement?

Answer 24

Sinusoidal wave passing down body or fins

Question 25

What does oscillation mean in fish movement?

Answer 25

Structure moving back and forth (almost a rowing motion)

Question 26

Describe the locomotory type anguilliform (eel-like) in fish (what does it involve, what is it seen in, what contributes to the propulsive force, speed- how do they increase it , different sections of the body, issues)

Answer 26

. Involves sinusoidal undulations of the whole body
. Seen in most eels, dogfishes and many fish larvae (seen in long bodied fish usually)
. Occurs in fishes with very flexible bodies
. All but the head contributes to the propulsive force
. As the wave moves posteriorly it increases in amplitude
. Speed (frequency) of the wave remains constant- always exceeds the speed of forward movement
. To swim faster- need faster waves (there is a limit to the speed in which it can produce those waves)
. Different sections of the body push against the water in different directions- so lose some of the forward motion- so there is some wasted energy in this form of motion
. Anguilliform swimmers are comparatively slow because of long bodies and involvement of anterior regions in propulsion
. Segments creating push forces also waste energy by pushing laterally and creating drag- ‘self-braking’

Question 27

Describe the locomotory type of fish movement Carangiform (subcarangiform) (how to avoid self-braking, why do they only use some portions of the body, use of ligaments, progression of types, functional hinge, advance swimmers)

Answer 27

. To avoid self-braking’ faster swimmers involve only the posterior segments of the body in wave generation
. Only some portions of the body are used in the wave generation
. Use ligaments to transfer force from muscles to caudal region
. Progression of types entails increasing use of tail and decreasing use of anterior body
. Functional hinge- connecting tail to caudal peduncle; allows fish to maintain tail at ideal attack angle of 10-20 degrees throughout the power stroke
. Advanced thymidine swimmers (e.g. tuna) have tail originating from narrow peduncle and lateral keels to create a more streamline shape- reduced drag
. Within the carangiform swimmers there is variability in tail design as fishes become more advanced from subcarangiform to the modified thymidine swimmers

Question 28

What kind of fins do subcarangiform swimmers have? Why is this good?

Answer 28

. Have caudal fins with a low aspect ratio
. Better suited for road acceleration and can aid hovering
. Tail has intrinsic musculature to help control shape

Question 29

What kind of fin do carangiforms have? Why is this good?

Answer 29

. Advanced swimmers have a stiff, sickle-shaped fin; narrow and tall
. Have a high aspect ratio- minimal drag; ideal for sustained swimming
. Reduced viscous drag by reducing surface area; reduced inertial drag by having pointed tips to produce minimal vortices (the only stage is from the tail fin itself and that is responsible for the forward motion of the animal itself)

Question 30

How do carangiform caudal fins increase efficiency? How does this differ from subcarangiforms?

Answer 30

Efficiency increased by the system of tendons rather than the muscle form itself which is seen in the subcarangiforms (such as trout) which have a much broader caudal peduncle* where the force doesn’t just come from the tail but from the back end of the animal as well- good for controlling and high acceleration that these animals can do (good for salmon and trout that have to do up against river currents)

Question 31

Describe the locomotory type in fish Ostraiform (what fish is it observed in, when does it oscillate, what do these type of fish rely on, describe the caudal fin, how do these fish swim?

Answer 31

. Observed in boxfishes (family Ostraciidae) and some other Tetraodontiformes (icefish, trunkfish) is extreme in that only the tail oscillates while the body is held rigid
. Contract the entire muscle mass on one side of the body then the other- produces a sculling motion
. These fishes rely on armour rather than speed for protection from predators
. The caudal fin is small and not differentiated into distinct lines- isocercal
. Elephant fishes (keep their bodies extremely rigid)- muscles pull on tendons (which move t forward) that run around the bones of the caudal peduncle and insert into tail
. Fish swims with ‘jerky’ tail beats only as apposed to a steady forward motion

Question 32

What is it called with a caudal fin is not differentiated into distinct lobes?

Answer 32

Isocercal

Question 33

Give 2 examples of fish that just their fins for forward motion

Answer 33

Sunfish, seahorses

Question 34

There are 5 types of group of fish that just use their fins for forward motion (all employ median and paired fins rather than body- tail couplings. Give the 5 groups

Answer 34

. Tetraodontiforms
. Labriform swimmers 
. Amiiform swimmers 
. Gymnotiforms
. Balistiforms

Question 35

Describe the groups of locomotion fin using fish (2) in the locomotion type Oscillatory. Give examples

Answer 35

. Tetraodontiforms (triggerfish, sunfish) also their dorsal and anal fins synchronously
. Labriform swimmers (wrasses, parrotfishes, surgeonfishes) row their pectoral fins, pushing with the broad blade then feathering it in the recovery phase (and switch to carangiform locomotion)

Question 36

Describe the groups of locomotion (3) in the undulatory locomotion types. Give examples

Answer 36

. Amiiform swimmers (seahorses, pipefishes, bowfins) the undulations lads along the dorsal fin
. Gymnotiform undulations of a log anal fin, essentially upside down amiiform
. Balistiform both an and dorsal fins undulate

Question 37

What are the 2 types of locomotion fin using fish?

Answer 37

. Oscillatory

. Undulatory

Question 38

What type of fish were the first lineage to evolve jointed fins? Give the class

Answer 38

The lib-finned fishes (class Sarcopterygii)

Question 39

In the water oxygen can vary considerably. What does it depend on?

Answer 39

If there is a water-body going into it, temp etc.

Question 40

Why do they think the gulping of water occurred?

Answer 40

Not due to buoyancy but to cope with reduced oxygen levels in water

Question 41

Why did lunglike sacs evolve?

Answer 41

In response to the inadequacy of gills for respiration in oxygen-poor waters (this set the stage for the invasion of land)

Question 42

Give the features of love finned (Sarcopterygii) fishes (what the fins are like, how they are attached to the body, how the fins differ from other fish, what do the scales consist of, what the pectoral and pelvic fins resemble, what they evolved into, how do they differ to actinopterygians (Ray-finned fish), what did many early ones have, what do all have)

Answer 42

. Fleshy, lobed paired fins, joined to the body by a single bone
. The fins differ from other fish- attached on a fleshy, lobe-like, scaly stalk extending from the body
. The scales consisting of dentine-like costume and keratin
. Pectoral and pelvic fins resemble tetrapod limbs. These evolved into legs of the first tetrapod land vertebrates, amphibians
. They have two dorsal fins with separate bases, as opposed to the single dorsal fin of actinopterygians (Ray-finned fish)
. Many early ones have a symmetrical tail
. All posses teeth covered with enamel

Question 43

How many species of lungfish are extant/ have survived? Where do they live?

Answer 43

6

In stagnant swamps and muddy waters in the Southern Hemisphere

Question 44

What are the lungfish lineage believed to have given rise to?

Answer 44

The tetrapods: the 4-legged amphibians, reptiles, birds and mammals of today

Question 45

What class of lungfishes in?

Answer 45

Dipnoi

Question 46

What is the most likely ancestor of the tetrapods? Describe these (body shape, fins, features)

Answer 46

. Elpistostegid (extinct group)
. Crocodile-like flattened body, had support in the vertebral column which was very important for territorialisation, no dorsal or anal fin, dorsal eyes (held towards the top of the animal), reduced tail, pectoral girdle and fins attached to operculum bones over gills (giving them support)

Question 47

What is the closest relative (Latin name) of tetrapods? Describe it (where it was found, what era it is from, what is represents, body shape/ make up, why this was key)

Answer 47

. Tiktaalik roseae
. A Devonian fossil found on Ellesmere Island (artic Canada) in 2006, may represent an intermediate between a finned fish and limbed tetrapod
. Pectoral girdle and fins seperared from operculur bones and skull- which means we have potential limbs which do not influence the head/ head movements, key because until now the only way in which the animal could move its head would be by moving its whole body
. Tetrapod legs later evolved from such jointed fins

Question 48

What is the advantage of separating the pectoral girdle from the skull? Why is this better? How is this enhanced?

Answer 48

. Feeding- better ability of catching prey
. Once the pectoral girdle is free from the skull, greater mobility is possible in the skull, permitting greater feeding
. This is enchanted by the architecture of the 2 occipital consuls and the presence of the atlas
. The snout and jaws become elongates (seen as a relative shortening of prix-occipital region)
. There is improved articulation of the jaw and expansion
. Head can move independently of the legs and also link to the vertebral column via a number of jointed bones (the atlas)

Question 49

Why did lobe-fins evolve into limbs?

Answer 49

. Adaption to shallow and temporary pools
. Foraging above water surface (insects, plants)/ resources
. Juvenile dispersal movements (over short land barriers)
. Escape from predatory fish (that can’t get out of the water)
. New semi-terrestrial (amphibious) foraging niches available- early amphibians move in the same way as the fish that left the water- have to move their body to put on leg forward

Question 50

What were he consequences of terrestrialisation?

Answer 50

. Have to change the sensors they had in the aquatic environment). Smell- now carried in the air, so gave to adapt to pick up air-born chemicals (transmission of chemical signals)
. Reproduction- broadcast spawning, which was often used, can no longer be used
. Circulation with multiple respiratory structures- need circulation that goes to the lungs

Question 51

What were the skeletal solutions to the consequences of terrestrialisation?

Answer 51

Prefrontal girdles divorcee from back of skull (implications for sound conduction). Sound is transmitted via the bones straight to the hearing organs in aquatic animals but with the separation of the skull from the rest of the skeleton that is no longer possible

Question 52

What were the skeleton adaptions to respond to the consequences of terrestrialisation?

Answer 52

. Undulatory locomotion (very early terrestrial forms- simply copied what the animals were doing in the aquatic environment)
. Suspension of vertebral column- the body is no longer supported by the water and so gravity pulls everything down (has to have a structure that allows it to stay in shape and so it doesn’t bend)
. Regionalisation of vertebral column- different parts of the vertebral column- different parts of the vertebral column are for different purposes (specialisation of regions of the vertebral column itself e.g. the skull)
. Organisation of amphibian vertebrae
. Suspension of internal organs (in the aquatic environment the whole body is supported by the water and when you come out on land these organs have to be held in place and so you have to develop a suspension system to do that)
. Reorganisation of the skull (move senses)

Question 53

What are the issues of moving into land that early animals had to contend with to adapt for transition to life in land?

Answer 53

. No buoyancy in air, so weight-bearing is crucial
. Movement facilitated by limbs, to apply force to the land surface for propulsion (instead of force applied to the side as in water)
. Gills collapse in air, so lungs are required for gas exchange (symplesiomorphy: already present in common ancestor with Dipnoi)
. Water loss through evaporation (from the skin- so these animals cannot survive in areas of very low humidity. So, come out to move from one water body to another, live in high humidity environments or come out when water loss is reduced e.g. at night) in air requires production of concentrated urine (to conserve water) in kidneys also providing a route for nitrogen excretion as insoluble iris acid salts- these can be excreted almost as a solid e.g. reduced water loss

Question 54

Why is the vertebral column in fish a fairly simple system?

Answer 54

Because there is no support between each individual vertebrae

Question 55

When the supporting vertebral column evolved when animals were adapting to terrestrial life, zygapophyses developed. What are these and what are they absent in?

Answer 55

Zygapophyses stop the vertebral column from sinking- lock vertebrae in position, still have a certain, but limited, amount of flexibility- the whole vertebral column is supported and from this rigid structure we have the suspension of those organs) absent in modern aquatic mammals(- as they no longer need them as the body is now being supported by the water again (a later reversal))

Question 56

Describe the tetrapod skeleton Acanthostega (very early example of an amphibian)

Answer 56

. A stem tetrapod of the late Devonian (c.360mya)
. 8toes in forelimb- multiple digits
. Flattened
. Only has very weak zygapophyses (probably why it is flattened- because there is a limit to how much the vertebral column can support)

Question 57

Give an example of a very early example of an amphibian

Answer 57

Acanthostega

Question 58

Describe the tetrapod skeleton Ichthyostega. Comparing t to Acanthostega (very early amphibian)

Answer 58

. A stem tetrapod of the late Devonian (c. 360mya)
. Much more upright stance. A lot more specialisation in the vertebrae. Stronger zygapophyses than Acanthostega. The ribs are more developed- are robust and overlap, providing protection to the internal organs. Reduction in the tail as it is no longer need as much as it was in the aquatic environment. However, still retains the tail and has ‘paddle-like’ hands so likely amphibious spending a lot of its time in the water/ an aquatic lifestyle
. 7 toes on hind limb (reduction in digits)