Introduction to Fish
Phylum Chordata
Subphylum Vertebrata
Class Agnatha
Class Chondrichthyes
Class Osteichthyes
Class Amphibia
Class Reptilia
Class Aves
– Class Mammalia
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fish
Class Agnatha
- jawless fish: hagfish and lampreys
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absence of jaws
no paired fins
cartilaginous skeleton
2-chambered heart
Basic Anatomy
Class Agnatha
• Possess medial nostril, medial fins,
notocord rather than vertebral column
• 7 or more pr gill pouches present
• Light sensitive pineal eye
• Fertilization external
• Cartilaginous skeleton
• Lack jaws, paired fins, scales
• GI track w/out stomach
• Lampreys and hagfish
• 100 species
Agnatha
Class Agnatha
Hagfish
Jaw Development
agnathostome
1st appeared 400 mya
gnathostome
Jaws evolved from gill supports.
• Jaws developed from gill arches located around the
pharynx.
cranium
cranium
mouth
•
cranium
gill arches
mouth
Jaws gave vertebrates a huge advantage as predators.
mouth
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.
Basic Anatomy
Class Chondrichthyes
Sharks, skates, rays
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Posses jaws with teeth, cartilaginous skeleton, paired fins
Scales (denticles) have same origin and composition as teeth
Possesses 5-7 gills
Spiral valve intestine
Ureoosmotic strategy
Electroreception
Lateral line
No swim bladder
Heterocercal tail
Relatively unchanged (480 mybp)
Cartilaginous fish
Chondrichthyes
Bronze whaler
Eagle ray
Chondrichthyes
Basic Anatomy
Class Osteichthyes
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Posses jaws with teeth, bony skeleton, paired fins
4 paired gill arches covered by operculum
Intestine- simple, no spiral valve
Swim bladder
Lateral line
Homocercal tail
Scales- cycloid, ctenoid
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
water
flow
•
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.
– keep fish stable
– redirect water around fish as it swims
– help fish maneuver in water
dorsal fin
caudal fin
pectoral fin
anal fin
pelvic fin
Types of Fins
The source of propulsion for virtually all fish
1.
2.
3.
4.
comes from:
Undulation of the body
Paired Fins:
• Pectoral
• Pelvic
Unpaired Fins:
• Caudal
• Dorsal
• Anal
A combination of the above
Anguilliform swimming
(Undulation)
Dorsal & Anal Fin Propulsion
Anal Fin Propulsion
Black ghost knifefish
Pectoral Fin Propulsion
Dorsal fin
Bowfin
Sea horse
Knifefish
Pectoral Fin
Frogfish
Walking catfish
Mudskipper
•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
Fish Adaptations and Life Styles
General Life Style Categories
a. pelagic cruisers
1. occurring in water column far away from the bottom (benthic)
environment
2. often referred to as "blue water"
3. includes tuna, billfish, blue sharks, mackerel sharks (great
whites and mako sharks)
b. demersal
1.
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. benthic
1. 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.
Body shape
tuna
1) fusiform
a) = torpedo-shaped
b) allows minimal drag while swimming
c) best shape for a pelagic cruise
2) compressed
a) laterally flattened (e.g., butterflyfishes &
surgeonfishes)
b) allows for maneuverability in surge environments
c) useful for demersal fishes that hover above the reef
d) exception seen in flatfishes that lie on one side of the
body as benthic fishes
John Dory:
predator in
waiting…
3) elongated or attenuated
a) 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) depressed
a) dorso-ventrally flattened (e.g., frogfishes,
scorpionfishes & gobies)
b) broad ventral surface facilitates resting on
the bottom
c) seen in many benthic fishes
Body Coloration
1) source of color
a) pigment color - chromatophores for yellows,
reds, oranges, browns, & blacks
b) 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) camouflage
1) matching the background coloration
2) usually involves having irregular dark
blotches and spots
3) 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
Hatchet fish
Cookie cutter shark
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 stripes
1)
bars are vertical (e.g., manini)
2)
stripes are horizontal (e.g., ta'ape)
3)
seen frequently in schooling demersal
fishes
4)
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 coloration
1)
bright, obvious color patterns
2)
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)
mimicry
1)
imitating other creatures
2)
seen in a few demersal and benthic fishes
3)
examples
a)
blenny (Aspidontus taeniatus) mimics
cleaner wrasses
b)
shortnose wrasse mimics Potter's angel
which sports a defensive spine
g)
mimicry
4)
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
Dragon wrasse
Stoplight parrotfish
Bluehead wrasse
Sex and social behaviour
Territoriality
Black angel
fish
Placoderm
(395-345)
Osteichthyes (395)
Ostracoderm (510-=350 mybp)
Chondrichthyes (370)
lamprey
& hagfish
(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
Ostracoderm (510-=350 mybp)
Placoderm
(395-345)
(360)
lamprey
& hagfish