Fish Locomotion

1
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 earths 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 Redu
ced 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 finlike rowing No
body waves - body remains rigid - useful for
odd-shaped fishes
7
Swimming Styles Medial fin wavesAmiiform -
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 StylesPectoral fin beats Labriform
wrasse-likeSimilar to rowing
laterally-positioned pectoral fins- often
includes feathering as wellEspecially useful
for fine maneuveringe.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
• 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
• lt 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
• --gt Detection
• --gt Pursuit
• --gt Capture
• --gt 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 benefitcost 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 (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)

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 - 40 - 55 protein needed
• omnivores - 28 - 35 protein needed
• (birds mammals - 12 - 25 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 (dont 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 1.7 - 5.0
• birds mammals 5.0 - 15.0

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)