1. (Helfman, Collette & Facey)
Functional
Morphology:
Locomotion
&
Feeding
Chapter 8
(Helfman, Collette & Facey)

2. 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

3. 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

4. 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: backward-facing “wall” of body pushing against the water

5. 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)

6. 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 odd-shaped fishes

7. 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

8. 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

9. 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

10. Fusiform body shape pointed leading edge
maximum depth 1/3 body length back from head
posterior taper
“propellor” (caudal fin) interrupts perfect fusiform shape

11. 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

12. 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)

13. 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

14. 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

15. 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.

16. 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

17. 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

18. 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

19. Food Aquisition & Processing
1. Structure
2. Function (behavior, physiology)
3. Nutritional needs
4. Digestive efficiency

20. Food capture
Mouth and pharyngeal cavity
upper jaw
teeth - jaw, mouth, pharyngeal
gill rakers

21. More on teeth

22. Food capture
Mouth and pharyngeal cavity
upper jaw
teeth - jaw, mouth, pharyngeal
gill rakers

23. Food capture
Mouth and pharyngeal cavity
upper jaw
teeth - jaw, mouth, pharyngeal
gill rakers

24. 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

25. GI- auxiliary organs Liver Pancreas produces bile (lipolysis)
stores glycogen
stores lipids
Pancreas
digestive enzymes
proteases - protein breakdown
amylases - starch breakdown
chitinases - chitin breakdown
lipases - lipid breakdown

26. 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

27. Fish Feeding - function, cont.
Carnivores
zooplanktivores
suction feeding
ram feeding
benthic invertebrate feeders
graspers
pickers
sorters
crushers

28. Fish Feeding - function, cont.
Carnivores, cont.
fish feeders
active pursuit
stalking
ambushing
luring

29. Fish feeding behavior
Fish feeding behavior integrates morphology with perception to obtain food:
Search
--> Detection
--> Pursuit
--> Capture
--> Ingestion

30. Feeding behavior Fish show versatility in prey choice and ingestion
Behavior tightly linked to morphology
(co-evolution)

31. 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

32. 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

33. Fish digestive physiology
Digestion is accomplished in
Stomach
low pH - HCl, other acids (2.0 for some tilapia!)
proteolytic enzymes (mostly pepsin)

34. Fish digestive physiology
Digestion is accomplished in
Stomach
Intestine
alkaline pH ( )
proteolytic enzymes - from pancreas & intestine
amylases (carbohydrate digestion) - from pancreas & intestine
lipases (lipid digestion) - from pancreas & liver (gall bladder, bile duct)

35. Fish digestive physiology
Absorption is accomplished in
Intestine
diffusion into mucosal cells
phagocytosis/pinocytosis by mucosal cells
active transport via carrier molecules

36. Fish Nutritional Needs
High protein diet:
carnivores % protein needed
omnivores % protein needed
(birds & mammals % protein needed)
10 essential amino acids (PVT. TIM HALL)

37. 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

38. Nutritional efficiency in fishes
Fish more efficient than other vertebrates:
conversion factor = kg feed required to produce 1 kg growth in fish flesh
fishes:
birds & mammals:

39. 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

40. 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

41. Temperature & Size effects - red hind (Serranidae)