introduction to fish. phylum chordata subphylum vertebrata – class agnatha – class...
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Introduction to Fish
Phylum Chordata
Subphylum Vertebrata
– Class Agnatha– Class Chondrichthyes– Class Osteichthyes– Class Amphibia– Class Reptilia– Class Aves– Class Mammalia
fish
Class Agnatha - jawless fish: hagfish and lampreys
• absence of jaws• no paired fins• cartilaginous skeleton• 2-chambered heart
Agnatha
Jaws evolved from gill supports.
• Jaws developed from gill arches located around the pharynx.
cranium
mouth gill arches
cranium
mouth
cranium
mouth
• Jaws gave vertebrates a huge advantage as predators.
Only two groups of jawed fish still exist. • Cartilaginous fish and bony fish are still in existence.
• Cartilaginous fish have skeletons made of cartilage.
• Cartilaginous fish include the Holocephali and Elasmobranchs
– Holocephali include ratfish, a small group of deep-sea fish.
– Elasmobranchs include sharks, rays, and skates.
Class Chondrichthyes - cartilaginous fish: sharks and
rays
• cartilaginous skeleton• 2-chambered heart• 5+ pharyngeal slits• well developed lower jaw• bony teeth• placoid (tooth-like) scales• ventral mouth and nostrils• nostrils do not open into mouth
Cartilaginous fish
Chondrichthyes
Bronze whaler
Eagle ray
Chondrichthyes
Class Osteichthyes - bony fish
• ossified skeleton• 2-chambered heart• pharyngeal slits covered by single bony
operculum (gill cover)• membranous fins strengthened with rays• presence of a swim bladder (teleost)• lateral line sensory receptor
Bony fish
Swim bladder
Fish are vertebrates with gills and paired fins.
• Fish use specialized organs called gills to breathe underwater.– sheets of thick, frilly tissue filled with capillaries – take in dissolved oxygen from water, release carbon dioxide
waterflow
• Countercurrent flow is the opposite movement of water against the flow of blood in the fish’s gills.
Circulatory system of fish
• Bony fish have skeletons made of bone.
– operculum protects a bony fish’s gills– movements of operculum help bony fish move water over gills
• Fins are surfaces that project from a fish’s body.
dorsal fin
caudal fin
anal finpectoral fin pelvic fin
– keep fish stable– redirect water around fish as it swims– help fish maneuver in water
•Myomeres – bands of muscle along sides of body contract pushing against water, forces body forward
•Dorsal & anal fins – act as rudders to steer & provide stability (unpaired)
•Pelvic fins – to turn, balance, & “brake” (paired)
● Pectoral fins – steering (paired)
Fish senses
• All fish have a lateral line system.
– sensory system– sensitive to small changes in water movement
lateral line
Lateral line system
Fish scales
• Reduce drag and direct water flow
Types of fish scales
General Life Style Categoriesa. pelagic cruisers1. occurring in water column far away from the bottom (benthic)
environment2. often referred to as "blue water"3. includes tuna, billfish, blue sharks, mackerel sharks (great
whites and mako sharks)
Fish Adaptations and Life Styles
b. demersal1. bottom-associated fishes, but not usually sitting on the bottom
2. rely on the benthic environment as a source of food, place to reproduce, and/or place of refuge, etc.
3. includes most reef fishes (e.g., butterfly fishes, surgeon fishes, wrasses, parrot fishes, etc.)
c. benthic1. bottom-dwelling fishes that spend the majority of time
sitting on the bottom
2. includes flatfishes, lizard fishes, many scorpion fishes, many hawkfishes, gobies, etc.
tuna
1) fusiforma) = torpedo-shaped b) allows minimal drag while swimmingc) best shape for a pelagic cruise
Body shape
2) compresseda) laterally flattened (e.g., butterflyfishes &
surgeonfishes)b) allows for maneuverability in surge environmentsc) useful for demersal fishes that hover above the reefd) exception seen in flatfishes that lie on one side of the
body as benthic fishes
John Dory: predator in waiting…
3) elongated or attenuateda) long body (e.g., trumpetfish, cornetfish, eels)b) seen in demersal fish that either hover
motionless in the water)c) seen also in benthic fishes (e.g., eels) that
hide in holes in the reef
4) depresseda) dorso-ventrally flattened (e.g., frogfishes,
scorpionfishes & gobies)b) broad ventral surface facilitates resting on
the bottomc) seen in many benthic fishes
Body Coloration
1) source of colora) pigment color - chromatophores for yellows,
reds, oranges, browns, & blacksb) structural color - iridophores (reflection) &
light refraction for blues, silvers, & rainbows
2) patterns
a) countershading
1) dark blue or black dorsally, white or silvery ventrally
2) results in blue water "camouflage“
3) observed most frequently in pelagic cruisers
b) camouflage1) matching the background coloration2) usually involves having irregular dark
blotches and spots3) typically seen in benthic fishes, especially
benthic ambush predators (e.g., frogfishes, gobies, & many scorpionfishes)
4) some fishes (e.g., flatfishes) may exhibit rapid color changes in response to different backgrounds
Cryptic colouration
b) camouflage
5) matching downwelling light
Cookie cutter shark
Hatchet fish
c) disruptive coloration
1) color pattern breaks up the silhouette of the fish
2) may involve dark bars across the eye and tail region
3) seen in many demersal fishes such as butterfly fishes
d) bars and stripes1) bars are vertical (e.g., manini)2) stripes are horizontal (e.g., ta'ape)3) seen frequently in schooling demersal
fishes4) may confuse potential predators by making it difficult to select individual
prey from the school
e) misdirection
1) false eye spots, etc.2) observed in many demersal butterfly fishes
f) advertising coloration1) bright, obvious color patterns2) possible functions
a) advertising a cleaning station (e.g., cleaner wrasses)b) advertising a warning (e.g., nohu)c) advertising for mates (e.g., male
parrotfishes)
Hawaiian cleaner wrasse Nohu
g) mimicry1) imitating other creatures2) seen in a few demersal and benthic fishes3) examples
a) blenny (Aspidontus taeniatus) mimics cleaner wrasses
b) shortnose wrasse mimics Potter's angel which sports a defensive spine
g) mimicry4) leafy sea dragon (Australia)
h) uniform red coloration
1) most often observed in deep-dwelling or night active demersal fishes
2) examples include opakapaka, oweoweo, menpachi, & squirrelfishes
i) noctural versus diurnal color changes
j) male versus female color differences
k) juvenile versus adult color differences
Bluehead wrasse
Dragon wrasse
Stoplight parrotfish
Sex and social behaviour
Territoriality
Black angel fish
Placoderm(395-345)
lamprey & hagfish
Ost
raco
derm
(510
-=35
0 m
ybp)
Ost
eich
thye
s (3
95)
Chondrichthyes (370)
(360)
Coelacanth
Lungfish
New Zealand Fish
• Over 1,000 species, many in Indo-Pacific and Australia as well
• Of the 270 coastal species, approx. 25% are endemic
Triplefins
Osteichthyes
Parore: Herbiverous fish feeding on kelps and other algae
• Demersal fish live on the sea floor
• Pelagic fish live in the water column above
Variations on a theme
Osteichthyes
Blue maomao : plankton feeders
Trevalley : plankton feeders
Snapper
Leatherjacket
Yellow-finned tuna