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

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 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 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 beatsLabriform 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. What is a fusiform body shape? • pointed leading edge • maximum depth 1/3 body length back from head • posterior taper • caudal fin interrupts ideal fusiform shape

11. Fin surface area reduction • Normally, surface 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)

12. Boundary layer modification • Layer of water immediately adjacent to skin causes most of friction - boundary layer • boundary layer thickness = friction • three approaches to reducing thickness: • smoothing it - making it “slicker” (65% reduction) • roughing it - giving it tiny disruptions, micro projections (golfers learned from sharks??) • shortening it - reducing distance of contact

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

14. Food capture • Mouth and pharyngeal cavity • upper jaw • teeth - jaw, mouth, pharyngeal • gill rakers: protect gills & strain food

15. 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

16. 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

17. 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

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

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

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

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

22. 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

23. 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

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

25. 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)

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

27. 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)

28. 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

29. 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

30. 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

31. 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

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