Fish Locomotion

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Functional Morphology: Locomotion & FeedingChapter 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 earths 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 tailResult: 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 finlike rowingNo body waves - body remains rigid - useful for oddshaped fishes

Swimming Styles Medial fin waves Amiiform - bowfin-likeBody 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 & Processing1. Structure 2. Function (behavior, physiology)

3. Nutritional needs4. 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


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 (dont 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 Fish mass MR (% body (g) mass/day) 250 1.7 600 28 250 600 1.3 5.8 3.0 Maint. diet (g) 4.25 7.8 14.5 18.0