form & function

Question 1

How are animals selected to have certain forms

Answer 1

1.morphology, physiology, biochemistry - amount of swimming muscle
2.performance capacity - burst swimming speed
3.behaviour - escape or not
4.fitness - life or death (leads to selection)

Question 2

what 2 things are there a balance between

Answer 2

• Some animals are fast and efficient survivors – but need lots of food + energy
• Other animals are slow – exist in a niche where less energy / food is required

Question 3

what happens when fish move its body to swim and how can we deal with this

Answer 3

some of it becomes thinner – move less mass to generate thrust
- Thin parts become floppy – becomes ramified with cartilaginous rods that run through body wall and thin body tissue
-Part in body wall = basal
-Part in fin = radial

Question 4

what are the cartilaginous rods called in the body and fin

Answer 4

-Part in body wall = basal
-Part in fin = radial

Question 5

what are the cartilaginous ridges that run through fin and body wall in elasmobranchs called

Answer 5

Still have basal + radial
- Ceratotrichia = fin
- Batoids = substantionally longer basals

Question 6

example of how radials change within different rays

Answer 6

• Ones that flap find like birds – radials extend considerably into fin itself
• Ones with more flexible fins – radials does not extend considerably into fin itself - gives more control at low speeds

Question 7

what does the radial articulate with in Primitive bony fish e.g. sturgeon

Answer 7

• radial now articulates with lepidotrichia (bony fin rays) outside body, and basal inside body
• Radial and basal made of bony material not cartilage

Question 8

fin structure in Advanced bony fish e.g. teleosts

Answer 8

• lepidotrichia = jointed – jointed fin rays
• Radial reduced to nub -> distal pterygiophores
• Basals = Inter and proximal pterygiophores
  Explains why you have such different looking fins

Question 9

what are radials called in Advanced bony fish e.g. teleosts

Answer 9

distal pterygiophores

Question 10

what are basals called in Advanced bony fish e.g. teleosts

Answer 10

Inter and proximal pterygiophores

Question 11

what gives bony fish much more control over their fins

Answer 11

Each fin ray has an associated muscle

Question 12

what kind of muscles do Pterygiophores have

Answer 12

• erector + depressor muscles – moves fin up and down
• indicator muscles – move fins left and right

Question 13

what can fin rays be ossified into in higher teleosts

Answer 13

Fin rays can be heavily ossified into spines in higher teleosts

Question 14

why are spine structures useful in higher teleosts and what 2 kinds can you get

Answer 14

• useful to make yourself bigger so cannot fit in preys mouth (gape limitation)
• Can also have venomous spines – if do get eaten get spat back out
  -Neural spine – goes upwards from vertical collumn
  -Haemal spine - goes downwards from vertical collumn

Question 15

what are fin characteristics in elasmobranchs and bony fishes

Answer 15

• Elasmobranchs = Rigid, inflexible, non-retractable primitive fins
• Bony fish = Very flexible, retractable fins supported by soft and spiny rays

Question 16

2 categories we can group fins into

Answer 16

• median fins (Single fin on central body line)
• paired fins

Question 17

5 different fin kinds

Answer 17

• dorsal
• anal
• pectoral
• pelvic
• caudal

Question 18

caudal fins job and characteristics

Answer 18

• All about thrust – escaping
• Can be symmetrical or asymmetrical
  -Bony fish usually have homocercal tail – reflects swim bladder – want to generate equal thrust when swimming
  -Primitive bony fishes + sharks = heteroceral tail – elasmobranchs have much bigger upper lobes – creates lift by giving downwards thrust (lack swim bladder)
• Can be highly decorative

Question 19

what kind of caudal fins do elasmobranchs and bone fishes have and why

Answer 19

• Bony fish = homocercal tail – reflects swim bladder – want to generate equal thrust when swimming
• Primitive bony fishes + sharks = heteroceral tail – elasmobranchs have much bigger upper lobes – creates lift by giving downwards thrust (lack swim bladder)

Question 20

what is Aspect ratio and its equation

Answer 20

Describes how much power that tail can generate
- Power to drag ratio of caudal fin depends on shape
- Problem with generating lots of power = generating lots of drag – more energy consuming
TAIL SPAN2 / TAIL AREA

Question 21

describe a Low aspect ratio tail

Answer 21

BROAD, FLAT TAIL: lots of thrust, but high drag
- used for short burst of speed e.g. rounded, truncate, emarginate
- Seen in cod, salmon, pike

Question 22

describe a high aspect ratio tail

Answer 22

THIN, NARROW TAIL: poor thrust, but little drag
- used for sustained swimming e.g. forked or lunate tail
- Seen in herring, mackerel and tuna

Question 23

describe a Intermediate-low aspect ratio tail

Answer 23

great thrust + reduced drag
- allows salmon to overcome hydrodynamic obstacles (travel far + overcome waterfalls) to reach their spawning grounds

Question 24

what is needed for Caudal fin swimming and how is this achievable

Answer 24

Flexible but non-compressible backbone
- Separately innervated blocks of muscle (myotomes - separated by myosepta) – each block can contract independantly
- Contraction of blocks on one side of body + and relaxation of blocks on opposite side will generate flexing of the body

Question 25

how to myotomes exist in vertebra

Answer 25

White muscle - folded into a series of W-shaped segments (myomeres)
- One myomere for each vertebra
- Lateral posterior-pointing cones (<-) and medial anterior-pointing cones (->)
- Nested cones are seen as concentric rings in cross sections of fish
- Majority of body mass

Question 26

what are myotomes, myosepta, myomeres

Answer 26

• myotomes = innervated blocks of muscle
• myosepta = sepereates myotomes
• myomeres = myotomes folded into a series of W-shaped segments (white muscle)

Question 27

White muscle characteristics

Answer 27

FAST TWITCH
- Poorly supplied with blood vessels and oxygen
- Little myoglobin – pale colour
- Few, small mitochondria
- Respires ANAEROBICALLY, converts glycogen to lactate - build up of lactic acid + oxygen debt
- Inefficient in fuel use
- Used for SHORT bursts of HIGH POWER
- 10+ fish lengths per second

Question 28

red muscle characteristics

Answer 28

SLOW TWITCH
- Well supplied with blood vessels and oxygen
- Well supplied with myoglobin – red colour
- Abundant, large mitochondria
- Respires AEROBICALLY, oxidising lipids and carbohydrates - no build up of lactic acid, no oxygen debt
- Fuel efficient
- Used for CONTINUOUS, slow swimming
- 3 to 5 lengths per second (depending on size
- Normally on outside of fish, always less of it
- Can use how much a fish has to look how active it is e.g. Pacific mackerel has loads of red muscle as it is very active

Question 29

4 forms of Body caudal fin swimming (BCS)

Answer 29

• Anguilliform (e.g. eels)
  Whole body undulates in large amplitude wavelength
• Subcarangiform (e.g. trout)
  Similar to 1 but undulation amplitude increases as waves progresses to the caudal fin
• Carangiform (e.g. mackerel)
  Stiff caudal fin, undulation only in final third of body
• Thunniform (e.g. tuna)
  Only tail moves backwards and forwards – more efficient (oscillation)

Question 30

how do Pectorals and pelvics fins control the movement of fish

Answer 30

direction change, braking, prevent pitch

Question 31

how do Dorsal and anal fins control the movement of fish

Answer 31

reduce roll, yaw and aid in turning

Question 32

do all fish use caudal fins for swimming

Answer 32

no
- e.g. parrotfish swim with their pectoral fins at low speeds - Rigid body means less drag, thus cheaper at slow speeds AKA median or paired-fin or labriform swimming
- At higher speeds, they use their caudal fin as the pectorals cannot provide enough thrust - referred to as undulatory or body caudal fin swimming

Question 33

how can Pectoral fins be modified

Answer 33

• Can be modified into wings - Escape from predators
• Air less viscous than water, so less drag
• As efficient as bird wing

Question 34

how can Dorsal fins be modified

Answer 34

• Can be modified into suction cups – allows to attach to larger animals e.g. sharks
• Virtually free travel
• Eat left-overs

Question 35

how can Pectorals and pelvics be modified

Answer 35

• Can be modified into little legs e.g. handfish
  At very low speeds, it may be cheaper to walk than swim
• Prevent detection from predators - fewer moving parts
• Common in ambush predetors

Question 36

what body shape is best for manoeuvrability

Answer 36

Short deep body - But produces high drag when swimming

Question 37

what body shape is best for continuous swimming

Answer 37

fusiform (spindle shaped) - Scombrids (mackerels, tunas, etc.) display that body shape

Question 38

Adaptations for sensory improvement

Answer 38

• tactile organs in gurnard
• sensory rays in rockling
• sensory and tactile pectorals tripod fish

Question 39

other adaptations to fins for different benefits (other than sensory improvement)

Answer 39

• Intromittent organ (claspers) in male sharks
  Used for internal fertilisation
  Modified pelvic fins
• Lure in Anglerfish
  Modified dorsal fin ray (illicium), sometimes with luminescent organ (esca) on the end
  Lure prey to ambush
• Lumpsucker (also common in gobies)
  Modified pelvic fins for attaching to seabed
  ”Sucker disc”
• Spines for defenece + gape limitation
• Camouflage in John Dory dorsal and pelvics
• Sexual dimorphism in Dragonet and colourful display of fins in males to display to females