Transcript Fish Locomotion

Functional
Morphology:
Locomotion
&
Feeding
Chapter 8
(Helfman, Collette & Facey)
Fish Locomotion
• Primary forces involved in fish swimming:
– Thrust - force that propels forward
– Drag - friction produced from passing an object
through a medium
– Gravity – force from earth’s magnetic pull
(partially counterbalanced by density of water)
– Lift - upward force that counteracts gravity
Swimming Styles...Thrust Generation
• Body waves – Anguilliform
• Partial body waves – (Sub)Carangiform
• Caudal peduncle/fin beats – Ostraciform
• Medial fin waves - Amiiform
• Pectoral fin beats -Labriform
Swimming Styles Body waves
Anguilliform (eel-like)
Lateral curvature in spine and
musculature that moves in a
posterior direction
Start: lateral displacement
of head, and then passage of
this displacement along the
body axis to the tail
Result: backwardfacing “wall” of body
pushing against the
water
Swimming Styles Partial body waves
(Sub) Carangiform, Thunniform (tuna-like)
Body wave begins posterior to head and increases with
amplitude as it moves posteriorly
Reduced drag compared to full body wave swimming
Wave STARTS at the caudal peducle (deeply forked,
lunate)
Swimming Styles Caudal peduncle/fin beats
Ostraciform (boxfish-like and puffer-like)
Sculling action of caudal fin—like rowing
No body waves - body remains rigid - useful for oddshaped fishes
Swimming Styles Medial fin waves
Amiiform - bowfin-like
Body rigid, but medial fins generate posterior waves
(forward) or anterior (reverse)
Good for stalking or moving without disrupting body
musculature that serves as electric organ (knifefish)
Also used for sculling - triggerfish & others
Swimming Styles
Pectoral fin beats
Labriform
wrasse-like
Similar to rowing
laterally-positioned
pectoral fins- often includes
feathering as well
Especially useful for fine maneuvering
e.g. by deep-bodied fishes
Drag Reduction Features in Fish
• Fusiform body shape
• Reduction of body wave amplitude
• Reduction of fin surface area:
– caudal fin (forked, lunate)
– paired and medial fins
• Boundary layer modifications
– mucous
– laminar jets of water
– microprojections
Fusiform body shape
• pointed leading edge
• maximum depth 1/3 body length back from
head
• posterior taper
• “propellor” (caudal fin) interrupts perfect
fusiform shape
Body wave modifications
• Minimize lateral movement of head to
reduce drag - subcarangiform
• Increase amplitude as wave moves in
posterior direction
• Ultimate expression involves no body
waves, but alternate contraction and transfer
of body musculature energy to caudal
peduncle and caudal fin - thunniform
Fin surface area reduction
• Area of fins increases drag
• Permanent design modifications: forked caudal
fins, reduced length of medial fins
• Adjustable design modifications: variable erection
of fins - allows for minimizing surface area when
fin is not needed for thrust or turning - ultimate
expression: fairings in tunas (dorsal and pectoral
fin pockets)
Boundary layer modification
• Layer of water immediately adjacent to skin
causes most of friction - boundary layer
• thickness of boundary layer is proportional to
amount of friction
• three approaches to reducing thickness of
boundary layer:
– smoothing it - making it “slicker”
– roughing it - giving it tiny disruptions (golfers
learned from sharks??)
– shortening it - reducing distance of contact
Boundary Layer, continued
• Fluid jets - from gill chamber and out operculum
or in micropockets behind and beneath scales
• mucous - slime adds to “slipperiness”, can reduce
drag by up to 65%
• microprojections - disrupt boundary layer so it
cannot grow:
– ctenii
– placoid tips
Buoyancy Control in Fishes
• Dynamic lift: generated by propelling a hydrofoil
forward at an inclined angle of attack
• Static lift: generated by including low-density
substances and reducing mass of high density
substances in body.
Dynamic Lift
• Hydrofoils: fish use their fusiform body and some
use their pectoral fins as hydrofoils
• Amount of lift is determined by: angle of attack
and speed of propulsion
• Ultimate expression of this is in pelagic rovers tunas, mackerel sharks
– head, pectoral fins and peduncle keels all used
as hydrofoils
– swim constantly
Static Lift
• Reduction of high density substances:
– cartilage less dense than bone
– use design features in bone that increase
strength while reducing mass of bone
• Inclusion of low-density fluids
– lipids - squalene in sharks (sp. grav. = 0.86)
• stored in liver
– gases - in swim bladder
• only in bony fishes
Swim bladders
• Gas-filled appendix to the anterior digestive
system; dorsal to abdominal organs
• Two types of swim bladders:
– physostomous - pneumatic duct connects swim
bladder to esophagous
– physoclistous - no connection between swim
bladder and gut
Food Aquisition
&
Processing
1. Structure
2. Function (behavior,
physiology)
3. Nutritional needs
4. Digestive efficiency
Food capture
• Mouth and pharyngeal cavity
– upper jaw
– teeth - jaw, mouth, pharyngeal
– gill rakers
More on teeth
Food capture
• Mouth and pharyngeal cavity
– upper jaw
– teeth - jaw, mouth, pharyngeal
– gill rakers
Food capture
• Mouth and pharyngeal cavity
– upper jaw
– teeth - jaw, mouth, pharyngeal
– gill rakers
GI
•
•
•
•
•
Esophagus
Stomach
– large in carnivores,
small in
herbivores/omnivores
Pyloric caecae
Intestine
– short in carnivores,
long in
herbivores/omnivores
Anus - separate from
urogenital pore
GI- auxiliary organs• Liver
– produces bile (lipolysis)
– stores glycogen
– stores lipids
• Pancreas
– digestive enzymes
•
•
•
•
proteases - protein breakdown
amylases - starch breakdown
chitinases - chitin breakdown
lipases - lipid breakdown
Fish Feeding - function
• Herbivores
– < 5% of all bony
fishes, no
cartilaginous fishes
• browsers - selective eat only the plant
• grazers - less selective
- include sediments
• Detritivores
– 5 - 10% of all species
– feed on decomposing
organic matter
Fish Feeding - function, cont.
• Carnivores
– zooplanktivores
• suction feeding
• ram feeding
– benthic invertebrate
feeders
•
•
•
•
graspers
pickers
sorters
crushers
Fish Feeding - function, cont.
• Carnivores, cont.
– fish feeders
•
•
•
•
active pursuit
stalking
ambushing
luring
Fish feeding behavior
• Fish feeding behavior integrates
morphology with perception to obtain
food:
– Search
– --> Detection
– --> Pursuit
–
--> Capture
–
--> Ingestion
Feeding behavior
• Fish show versatility in
prey choice and
ingestion
• Behavior tightly linked
to morphology
(co-evolution)
Fish feeding behavior
• Behavior tends to be optimizing when
choices are available
– optimal = maximize benefit:cost ratio
– basically...more for less!
– i.e., select the prey that yields the greatest
energetic or nutrient “return” on the energy
invested in search, pursuit, capture, and
ingestion
Fish digestive physiology
• After ingestion of food, gut is responsible for:
– Digestion (breaking down food into small,
simple molecules)
• involves use of acids, enzymes
– Absorption - taking molecules into blood
• diffusion into mucosal cells
• phagocytosis/pinocytosis by mucosal cells
• active transport via carrier molecules
Fish digestive physiology
• Digestion is accomplished in
– Stomach
• low pH - HCl, other acids (2.0 for some tilapia!)
• proteolytic enzymes (mostly pepsin)
Fish digestive physiology
• Digestion is accomplished in
– Stomach
– Intestine
• alkaline pH (7.0 - 9.0)
• proteolytic enzymes - from pancreas & intestine
• amylases (carbohydrate digestion) - from
pancreas & intestine
• lipases (lipid digestion) - from pancreas & liver
(gall bladder, bile duct)
Fish digestive physiology
• Absorption is accomplished in
– Intestine
• diffusion into mucosal cells
• phagocytosis/pinocytosis by mucosal cells
• active transport via carrier molecules
Fish Nutritional Needs
• High protein diet:
– carnivores - 40 - 55% protein needed
– omnivores - 28 - 35% protein needed
– (birds & mammals - 12 - 25% protein
needed)
– 10 essential amino acids (PVT. TIM HALL)
Fish Nutritional Needs
• High protein diet
• Why so high?
– proteins needed for growth of new tissue
– proteins moderately energy-dense (don’t
need dense source - ectotherms, low gravity)
– few side-effects - ease of NH4+ excretion
Nutritional efficiency in fishes
• Fish more efficient than other
vertebrates:
– conversion factor = kg feed required to
produce 1 kg growth in fish flesh
• fishes: 1.7 - 5.0
• birds & mammals: 5.0 - 15.0
Nutritional efficiency in fishes
• Fish more efficient than other vertebrates
• Why?
– ectothermy vs. endothermy
– energy/matter required to counterbalance
gravity
– bias of a high-protein diet
Nutritional efficiency
• Maintenance ration (MR) = the amount of food
needed to remain alive, with no growth or
reproduction (% body wt./day)
• MR is temperature-dependent
– MR increases as temperature increases
• MR is size-dependant
– MR decreases as size increases
Temperature & Size effects - red hind
(Serranidae)
Temp (C)
19
28
Fish mass MR (% body
(g)
mass/day)
250
1.7
Maint. diet (g)
4.25
600
1.3
7.8
250
5.8
14.5
600
3.0
18.0