Vertebrates 11.1 - Swimming Flashcards
Primary and secondary swimmers
Primary have always swam, secondary have returned to water from an ancestor that was terrestrial
Primary and secondary swimmers examples
Primary: fish and aquatic amphibians; Secondary: sea turtles, penguins, alligators, pinnipeds, cetaceans.
Undulatory groups
Trunk and tail: Anguiliform, carangiform, thunniform, ostraciform. Undulatory with paired fins ok too.
Anguliform
use most of body in undulation. Eels
Carangiform
About half of body (caudal) undulates. Jack fish and alligator.
Thunniform
Use just the back part of the tail. Tuna. The best form of swimming, creates the least drag.
Ostraciform
Just the tail moves. Rest of body rigid. Boxfish.
Undulatory with paired or unpaired fins
Stingray, bowfin, seahorse
Oscillatory swimmers
More like paddling. Used paired fins or legs. Frogs, beaver, sea turtle, penguins, duck, swan, perch
Role of fins
Caudal: generally big, thrust. Others are for stability and direction.
Pitch
Movement up and down. In fish created by extending or flexing both fins on both side (pectoral and pelvic)
Yaw
Movement side to side. In fish created by extending one fin and flexing the other.
Rolling
Controlled with the dorsal and anal fins, provide stability.
Were ancient fish good swimmers?
Streamline, caudal fin ok. But lacking the dorsal fins and pectoral fins pretty weak, so not very good. Dermal armour heavy and not flexible
Problems with water locomotion
Drag, buoyancy, and specific heat (esp for secondary swimmers)
Overcoming Drag
Water is dense, so it creates drag. Fusiform shape helps. (rounded at front end, tapered at other). Mucous makes boundary layer (water interacts with it, less drag).
Slow vs fast swimming
Slow: frictional drag. Fast: eddies/vortices create pressure drag (acts like vacuum). To go fastest, need to minimize movements but provide enough thrust. Balance.
Buoyancy
Depends on density of the animal. Most will sink naturally, but most have mechanisms to overcome
Buoyancy mechanisms of chondrichthyes
Cartilage is less dense than bones. Lots of lipids in liver (squalene). Shape helps maintain buoyancy (tail thrusts down a bit, head gives a bit of lift), fins lift.
Buoyancy mechanisms of osteichthyes (ray fins)
Swim bladder. It’s a membraneous sac associated with blood vessels. Regulates amount of gas in it. Head and tail don’t really affect buoyancy.
Problems with specific heat of water
Ectotherms ok because their body temperature can fluctuate without problems. Endotherms (cetaceans, some birds) need core temperature to be constant, use subcutaneous fat.
