Fish Flashcards
how do organisms get better, stronger, faster?
muscles, internal skeleton, better lungs, better circulatory systems
Gill filament structure
(thin, vascularized, high surface area)
-blood vessels flow through gill arches
-capillary beds in gill filaments; gas exchange
-filament epithelium is one cell thick (1-2 micrometers)
-water & blood flow in opposing direction!!
Countercurrent exchange
-blood flows in opposite direction to water flow
-ensures partial pressure gradients are maintained
-achieves maximum exchange of gases (O2 and CO2)
-concurrent flow not seen in fish gills
-countercurrent flow seen in fish gills
-more efficient exchange across the gradient, partial pressure maintained when flowing in opposite directions
-whales/dolpihn in arctic and geese in canada = have countercurrent exchanges for heat within the legs and flippers
-as the warm blood comes in it goes further and moves warmth into the blood
>retains the heat through countercurrent exchange before the heat gets into the extremities
>same thing happens in the kidney
>present in the swim bladder in fishes (what evolved into the lungs)
>heat pumps and airconditioning work the same way
Fish circulatory system
-system = closed (single circuit)
>arteries to arterioles to capillaries to venules to veins
-fish hear only has 2 chambers
>strong muscular pump
>ventrally located
>one way valves
>2+ chambers
>maintains blood flow
Humans have two circuits (pulmonary and systemic)
-chordata similarities:
1)dorsal hollow nerve cord (carry electrical signals)
-lancelots
2)notochord (rigid structure, partially integrated into the nerve cord, precursor to the spine, thick fluid filled, provides structure to the body)
3)muscular, post-anal tail (use for locomotion, lost through evolution)
Pharyngeal slits (pouches)
-located on the side of the head
-ancestral trait for deuterostomes
-lost in echinoderms
-supported by arches (cartilaginous) in vertebrates → important for vertebrate function
-FUNCTION: filter feeding (water comes in and out), taking food out
-cephalochordate (lancelets)
-urochordate (tunicates)
-respiration in vertebrates (water coming in mouth passes through slits)
-O2 and CO2 can be exchanged across a respiratory surface = gills
Vertebrata
-characteristics:
a)axial skeleton
>cranium (skill)
>vertebral column (spine)
>ribs
b)appendicular skeleton
>pectoral girdle
>pelvic girdle
>closed circulatory system!! First time
>ventral heart
>blood moves in loops, not flowing directly through the animal
>organs suspended in coelom (sack)
Fish diversity
-fish are not monophyletic
-are they even a real group? ‘Fish’
-myxinoidea (hagfish) and petromyzontoidea (lampreys) have cranium and vertebrae but dont have jaws
>everything else after them has jaws
-vertebrates, but not gnathostomes (jawless fishes, aka agnathans)
-lampreys and hagfish (eel looking, extended)
-cartilaginous skeleton
-no paired fins
-no swim bladder
-no scales
-gill slits
-notchord present
-no jaws
Hagfish (scavengers at the bottom of the ocean)
> Mixinoidea
-dont regulate their osmotic concentration, same as seawater
-kidneys dont do alot of work
-used by humans for leather
-tie a knot with their bodies until it comes up to their head and rip off the food
-mucous production
-go inside of dead whales and eat them from the inside out
-produce massive amounts of mucus
Lampreys (petromyzontoidea)
-superficially looks like hagfish
-has rasping teeth like
-suck out juices
-very distinct larval form (ammocoete)
-adults of many species are parasitic on fishes
-no jaw, oral disc instead
-filter feed in freshwater for 7 years
-in ocean they are parasitic on fish and then come back to freshwater to breed (similar to life history of salmon)
-low head dams
-lampreys cant jump very well
Jawed fishes = gnathostomata
-jaws are very important
-not present in early fishes and present-day agnathans
-evolved from anterior gill arches
-teeth evolved from scales in mouth
-greatly improved ability to feed and diversify
-fish with jaws have less gill arches
-chewing enabled → tearing
Gnathostomes have paired fins
-on pectoral and pelvic limb girdles
-enabled more active swimming
-used for steering stabilizing and lift
-pelvic fin used for stabilization
-pectoral fins also important
-fins have also diversified
Gnasthostomes part 1
-cartilaginous fishes (aka chondrichthyes)
-sharks, skates, rays
-mostly marine
-jaws
-paired fins
-5-7 gill slit pairs
-SCALES
-no swim bladder
-predators, scavegers, filter-feeders
-males bit the fit of the female to stay close to her while mating
>white tip sharks in the galapagos
Sharks
-high diversity
-whale shark, basking shark, great white
-smallest living shark (16 cm, dwarf lantern shark)
-largest living shark (18 m, whale shark)
Two groups of bony fishes
1)ray-finned fishes (actinopterygians)
>teleosts
*deep sea anglerfish (700-1000 meters, bioluminescent lures, pheromones)
*males are parasitic and find/bite and never let go to the females (shared blood flow, female does all the eating) hard to find male and female in the ocean
>most fishes 2)lobe-finned fishes (sarcopterygians) >lungfish >coelocanths -much diversity in form and function
How to get better?
-get more oxygen: gills & heart
-get that skeleton on the inside
-jaws
-paired fins
Coelacanth
(actinistia) = a living fossil
-thought to be extinct (65 mya)
-1938 = found on south african trawler
-1998 - 2nd species found in Indonesian fish market
Lungfish
(Dipnoi)
-6 species (Africa, SA, aust)
-walk on lobe-fins >tetrapod motion
-breathe through gills & primitive lungs
-estivate in mud during droughts
Why move on land?
-devonian droughts (around 400 mya)
>shallow inland seas, swamps, ponds
>low dissolved O2
-increased competition in water (crowidng in small pools)
-new food resources on land (arthropods, plants)
-no competitors on land
Differences between land and water as relevant to life
-less moisture on land
-density of medium (need muscle to support)
-easier access to oxygen, more of oxygen
-stability of temperature (less stable in air)
-amount of UV radiation
Advantages of terrestrial respiration
-air has a higher concentration of oxygen than water
-gases diffuse faster in air than water
Lung evolution
-lobe-finned fishes
>2 ventral pockets formed off esophagus
-used as a supplemental respiratory device
Problems on land
1)water needed to prevent desiccation
>need to stay moist
>most require water for fertilization and larval development
2)air is less dense than water (biggest challenge)
>requires stronger skeletal support, muscles
>require more energy, more oxygen brought in and distributed
3)air temperature is more variable
>body temp will fluctuate more
>need to modify behavior or physiology
4)UV radiation more intense on land
>need physical protection or change behavior
Tetrapod solutions
1)stronger limbs, vertebral column, ribs
Early tetrapod
Ichthyostega
>stronger limbs and girdles, vertebral columns, ribs
>tail used for balance, not swimming
>lungs were primary respiratory organ
>external and internal nostrils (nares)
