Study #3: Test 3: Fishes Flashcards
Traits of Vertebrata
- Largest, most diverse group of chordates
- Bony vertebrae (endoskeleton) completely replaces notochord
- All (xc jawless) have vertebral column
- Anterior end of nerve cord develops into 3 part brain
- Body plan: head, trunk, post-anal tail
- Two pairs of appendages (most)
- Many paired structures: kidneys, gonads, etc.
- Closed circulatory with heart
Theory of Vertebrate evolution: Walter Garstang 1928
Paedomorphosis: evolutionary retention of juvenile traits in adult body.
Theory that a tunicate tadpole larvae failed to become a sessile adult (mutated?), leading to a free-swimming adult
Recent molecular evidence supports a free-swimming ancestor
Jawless fish
Ostracoderms: earliest known fossil vertebrates; died off 360 MYA
Gave rise to modern jawless fish: Agnatha (hagfish and lampreys)
Super Class Agnatha: jawless fish
Hag fish and lampreys LACK: jaws scales paired fins bony skeleton
Class Myxini: Hagfishes
- Brain enclosed in fibrous sheath
- No vertebrae
- Possess notochord
- 4 pr of sensory tentacles surround mouth, but blind
- Slime covers body
- Burrow into mud on marine bottom and feed on dead animals
Class Petromyzontida: lampreys
- True vertebrates: nerve cord surrounded by vertebrae
- Suckerlike mouth with teeth
- Adults attach to prey, rasp away scales and feed on their blood
Lamprey problem in Great Lakes
- 1829 a canal was built between between Great Lakes and Atlantic
- By 1940, lampreys had invaded fisheries causing damage
- 1950, lake trout fishery collapsed along with other important species
- Problem still exists today
Fishes
- Oldest, most diverse Vertebrata (>25K species ie most vertebrates are fish)
- Aquatic; gill breathing
- Ectothermic (body head from environment)
- Paired appendages (pectoral-anterior & pelvic-posterior fins)
- Scales to reduce drag during swimming
- Jawed
Evolution of jaws
Evolved from anterior pharyngeal arches.
Allowed > efficient gill ventilation
Allowed > capture and ingestion of many different foods.
Same genes involved in development of bones supporting gills, also form the jaw.
Class Chondrichthyes: Cartilaginous Fishes
- Endoskeleton cartilaginous
- Tough skin with scales
- Teeth are modified scales
- Ventral mouth, no gill cover
- No swim bladder to regulate buoyancy
Subclasses of Chondrichthyes
Eslasmobranchii: sharks (predators), skates and rays (bottom feeders)
Holocephali: chimaeras (ratfish, ghostfish) no teeth and upper jaw fused to cranium
Adv of bony endoskeleton
- grows with body permitting unlimited body size
- living tissue
- Scaffold for muscle attachment
- Bone:
stores phosphorous & calcium
necessary strength for life on land
Protection (skull)
Blood cell formation in marrow
Class Osteichthyes: Bony fishes
- Bony Skeleton
- Bony operculum covers gill opening
- Swim bladder or lungs for buoyancy
- Examples: lobed-finned fishes (sarcopterygii)
and ray finned fishes (actinopterygii)
SIGNIFICANCE OF Subclass Sarcopterygii: Lobe-finned fishes
lungs for gas exchange allows survival out of water
Paired fins used to “walk” along bottom (ancestors to tetrapods)
Muscular lobes attached with their fins
Only 3 extant genera
Subclass actinopterygii
Most living fishes belong to this group.
Also called Modern bony fishes or teleosts
Fins lack muscular lobes
Swim bladder for buoyancy
Traits that make fish so successful
- Streamlined shape and mucus secretions reduce friction during swimming
- Paired fins and zigzag bands of muscles provide strong propulsion
- Can pump large volumes of water with muscles in mouth (swim with mouths open) to extract low amount of O2 present in water
Gas exchange across gills
Very efficient using countercurrent exchange method
Swim bladder
Gas filled chambers regulates buoyancy.
Gas comes from blood.
Light body tissues and lift from fins also help with buoyancy
Osmoregulation
Freshwater problem: osmotic uptake of water; loss of ions; do not drink water; kidneys designed to reabsorb ions, leading to dilute urine
Saltwater problem: must fight water loss
Drink water
Kidneys designed to reabsorb water, leads to salty urine
Elasmobranchs
Convert nitrogenous waste to urea and store it in tissues;
This reduces water loss because it is iso-osmotic with the seawater
Diadromous fishes
Migrate between freshwater and marine environments
NEED GILLS WHICH CAN DO BOTH
Sensory capabilities of fishes
Well developed: vision smell vibration reception (lateral line) electroreception (ampullae of lorenzini)
Reproduction of fishes
- Internal fertilization, parental care
- Oviparous: eggs dev outside female, nourished by stored yolk
- Oviviparous: embryos develop in a modifed oviduct of female, nourished by stored yolk
- Viviparous: embryo develops inside female, nourished coming directly from her
What makes sharks good predators?
***Highly developed senses: can perceive tiny changes in electricity around them; make them skillful hunters
Cartilaginous skeletons: strong and flexible
Replaceable teeth
5-7 gill slits on each side of body
No swim bladder so can cruise bottom for long periods of time
