form & function Flashcards
How are animals selected to have certain forms
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)
what 2 things are there a balance between
- 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
what happens when fish move its body to swim and how can we deal with this
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
what are the cartilaginous rods called in the body and fin
-Part in body wall = basal
-Part in fin = radial
what are the cartilaginous ridges that run through fin and body wall in elasmobranchs called
Still have basal + radial
- Ceratotrichia = fin
- Batoids = substantionally longer basals
example of how radials change within different rays
- 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
what does the radial articulate with in Primitive bony fish e.g. sturgeon
- radial now articulates with lepidotrichia (bony fin rays) outside body, and basal inside body
- Radial and basal made of bony material not cartilage
fin structure in Advanced bony fish e.g. teleosts
- lepidotrichia = jointed – jointed fin rays
- Radial reduced to nub -> distal pterygiophores
- Basals = Inter and proximal pterygiophores
Explains why you have such different looking fins
what are radials called in Advanced bony fish e.g. teleosts
distal pterygiophores
what are basals called in Advanced bony fish e.g. teleosts
Inter and proximal pterygiophores
what gives bony fish much more control over their fins
Each fin ray has an associated muscle
what kind of muscles do Pterygiophores have
- erector + depressor muscles – moves fin up and down
- indicator muscles – move fins left and right
what can fin rays be ossified into in higher teleosts
Fin rays can be heavily ossified into spines in higher teleosts
why are spine structures useful in higher teleosts and what 2 kinds can you get
- 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
what are fin characteristics in elasmobranchs and bony fishes
- Elasmobranchs = Rigid, inflexible, non-retractable primitive fins
- Bony fish = Very flexible, retractable fins supported by soft and spiny rays
2 categories we can group fins into
- median fins (Single fin on central body line)
- paired fins
5 different fin kinds
- dorsal
- anal
- pectoral
- pelvic
- caudal
caudal fins job and characteristics
- 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
what kind of caudal fins do elasmobranchs and bone fishes have and why
- 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)
what is Aspect ratio and its equation
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
describe a Low aspect ratio tail
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
describe a high aspect ratio tail
THIN, NARROW TAIL: poor thrust, but little drag
- used for sustained swimming e.g. forked or lunate tail
- Seen in herring, mackerel and tuna
describe a Intermediate-low aspect ratio tail
great thrust + reduced drag
- allows salmon to overcome hydrodynamic obstacles (travel far + overcome waterfalls) to reach their spawning grounds
what is needed for Caudal fin swimming and how is this achievable
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
how to myotomes exist in vertebra
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
what are myotomes, myosepta, myomeres
- myotomes = innervated blocks of muscle
- myosepta = sepereates myotomes
- myomeres = myotomes folded into a series of W-shaped segments (white muscle)
White muscle characteristics
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
red muscle characteristics
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
4 forms of Body caudal fin swimming (BCS)
- 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)
how do Pectorals and pelvics fins control the movement of fish
direction change, braking, prevent pitch
how do Dorsal and anal fins control the movement of fish
reduce roll, yaw and aid in turning
do all fish use caudal fins for swimming
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
how can Pectoral fins be modified
- Can be modified into wings - Escape from predators
- Air less viscous than water, so less drag
- As efficient as bird wing
how can Dorsal fins be modified
- Can be modified into suction cups – allows to attach to larger animals e.g. sharks
- Virtually free travel
- Eat left-overs
how can Pectorals and pelvics be modified
- 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
what body shape is best for manoeuvrability
Short deep body - But produces high drag when swimming
what body shape is best for continuous swimming
fusiform (spindle shaped) - Scombrids (mackerels, tunas, etc.) display that body shape
Adaptations for sensory improvement
- tactile organs in gurnard
- sensory rays in rockling
- sensory and tactile pectorals tripod fish
other adaptations to fins for different benefits (other than sensory improvement)
- 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
