Transcript Intro to Fish - honorsmarinebiology

Marine Fishes
© 2006 Thomson-Brooks Cole
Jawless Fishes
• Class Agnatha
• Lack both jaws and paired appendages
• Have skeletons of cartilage (no bone)
• Lack scales
• Hagfish also lack vertebrae (some
scientists consider them invertebrates)
© 2006 Thomson-Brooks Cole
Hagfishes
• Bottom dwelling “slime eels”
• Skins are used to make leather goods
• Slime glands produce abundant milky,
gelatinous fluid if hagfish is disturbed
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Lampreys
• Have oral disk and rasping tongue covered with
tooth-like keratin plates
• Reproduction
– males migrate up rivers and build nests
– females arrive and they spawn; eggs attach to
stones of the nest
– larvae are benthic filter feeders
– after 3-7 years, they metamorphose into adults
and return to the sea
© 2006 Thomson-Brooks Cole
Lamprey Weir
© 2006 Thomson-Brooks Cole
Cartilaginous Fishes
• Class Chondrichthyes
– e.g. sharks, skates, rays, chimaeras
• Skeleton of cartilage
• Possess jaws and paired fins
• Have placoid scales (denticles)
© 2006 Thomson-Brooks Cole
Sharks
• Excellent swimmers with streamlined
bodies
– swim with powerful, sideways sweeps of
the caudal fin (tail)
– heterocercal tail—caudal fin in which the
dorsal lobe is longer than the ventral
• Males have claspers—modified pelvic
fins which transfer sperm from the
male to the female
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Which is a male?
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Sharks
• Maintaining buoyancy
– sharks sink if they stop swimming
– large livers produce squalene—an oily
material with a density less than seawater
– squalene offsets the shark’s higher density
to help maintain buoyancy
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Shark Sensory Systems
• Vision
– a clear nictitating membrane covers and
protects each lidless eye
– many species seem to have color vision
• Olfaction
– more important than vision – almost 2/3
of the shark’s brain cells are involved in
processing olfactory information
– sharks are sometimes referred to as
“swimming noses”
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Nictitating Membrane
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Shark Sensory Systems
• Lateral line system
– consists of canals running the length of
the animal’s body and over the head
– neuromasts detect vibrations in the fluid
which alert the shark to movements in the
water, possibly made by prey animals
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Shark Sensory Systems
• Ampullae of Lorenzini
– organs scattered over the top and sides of
the animal’s head
– sense electrical currents in the water
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Digestion in Sharks
• Blade-like, triangular teeth in the
mouth grasp prey and tear off chunks
(in some species)
• Food is swallowed whole (sharks
cannot move their jaws back and forth
to chew)
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Shark teeth
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Osmoregulation in Sharks
• Maintain an internal solute
concentration > or = to the seawater
– retain large amounts of nitrogenous
wastes, mostly urea.
• Gills work to excrete excess sodium
chloride (salt)
• Kidney excretes other salts
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Reproduction in Sharks
• Males have claspers to hold females
during copulation.
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3 Type of Reproduction in
Sharks
• Oviparity
– most primitive mode
– eggs are laid outside the body and the
embryos develop in a protective case
• e.g. whale sharks, bullhead sharks,
skates
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Oviparity
© 2006 Thomson-Brooks Cole
Reproduction in Sharks
• Ovoviviparity
– most common mode
– eggs hatch within the mother’s uterus but
no placental connection is formed
• young are nourished by yolk from the egg
– e.g. basking sharks, thresher sharks, saw
sharks, sand tiger
© 2006 Thomson-Brooks Cole
Ovoviviparity
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Reproduction in Sharks
• Viviparity
– most recent mode to evolve
– either the young directly attach to the
mother’s uterine wall or the mother’s
uterus produces “uterine milk” that is
absorbed by the embryo
– e.g. requiem sharks, hammerhead sharks
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Skates and Rays
• Have flattened bodies adapted to a
bottom existence
• Greatly enlarged pectoral fins that
attach to the head
• Reduced dorsal and caudal fins
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Skates and Rays
• Eyes and spiracles (openings for the
passage of water) on top of the head
• Gill slits on the ventral side
• Specialized pavement-like teeth are
used to crush prey (e.g. invertebrates)
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Differences between Skates
and Rays
Rays: swim by moving Skates: create a wave
fins up and down
from the forward to
backward fin edges
streamlined tails with fleshier tails with small
venomous barbs or
fins and no spines
spines
larger size
smaller size
ovoviviparous
mostly oviparous
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Defense Mechanisms
• Electric rays have electric organs that
can deliver up to 220 V
• Stingrays have hollow barbs connected
to poison glands
– treatment for stingray wounds: submerge
in hot water to break down protein toxin
• Sawfishes and guitarfishes have a
series of (non-venomous) barbs along
their pointed rostrums
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Sawfish
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Chimaeras
• Subclass Holocephali
– e.g. ratfish, rabbitfish, spookfish
• Large pointed heads and long, slender
tails
• Gills covered by operculum; water
inhaled through the nostrils
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Chimaeras
• Oviparous – produce large eggs in a leathery
case
• Have flat plates for crushing prey instead of
teeth
• Generally bottom dwellers
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Bony Fishes
• Class Osteichthyes
• Very diverse 25,000 species
• Most forms have: swim bladder (or
lung), bone, bony scales, and fin rays
• 2 classes: lobed-fin fish and ray fin fish
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Coelacanths
• Characterized by lungs and lobed,
paired fins
• Known from fossils only before live
specimen was discovered in 1938
• Fat-filled swim bladder for buoyancy
• Nearly isotonic to seawater like sharks
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Ray-Finned Fishes
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Ray-Finned Fishes
homocercal tails, cycloid or ctenoid scales,
more maneuverable fins
• homocercal tails—tails with dorsal and ventral
flanges nearly equal in size; vertebral column
usually does not continue into the tail
• cycloid & ctenoid scales—scales that are
thinner and more flexible; less cumbersome
for active swimmers
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Caudal Fin
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© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Ray-Finned Fishes
• Possess paired fins, providing better
control of movements
• Median fins consist of 1 or more dorsal
fins, caudal fin, and usually anal fin
– help maintain stability while swimming
• Paired fins consist of pectoral and
pelvic fins
– both used in steering
– pectoral fins also help to stabilize the fish
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Body Shape
• Fusiform body shape—streamlined
shape with a very high and narrow tail
– efficient movement for active swimmers
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Body Shape
• Laterally
compressed
or deep
body
– allows
navigation
through
grass or
corals
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Body Shape
• Depressed or flattened bodies
– bottom-dwelling fishes
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Body Shape
• Globular bodies, enlarged pectoral fins
– appropriate for sedentary lifestyle
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Body Shape
• Long, snake-like bodies, absent or
reduced pelvic and pectoral fins
– useful for burrowing, living in tight spaces
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Fish Coloration
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Fish Coloration
• Countershading is seen in open ocean
fish
• Disruptive coloration—background
color of the body is usually interrupted
by vertical lines; may be an eyespot
– more difficult for predators to see the fish
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Countershading
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Fish Coloration
• Cryptic coloration—coloration which
blends with the environment
– used for camouflage
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© 2006 Thomson-Brooks Cole
Fish Coloration
• Poster colors—bright, showy color
patterns
– may advertise territorial ownership, aid
foraging individuals to keep in contact, or
be important in sexual displays
– aposematic (warning) coloration—bright
coloration to warn predators that the fish
is too venomous or spiny to eat
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Locomotion in Bony Fishes
• In swimming, the trunk muscles propel
the fish through the water
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© 2006 Thomson-Brooks Cole
Respiration and
Osmoregulation
• Gills often used to extract O2,
eliminate CO2, and aid in salt balance
– gill filaments—highly vascularized, rod-like
structures which compose the gills
– countercurrent multiplier system—blood
flows in the opposite direction from the
incoming water, maintaining a stable
gradient that favors the diffusion of O2 in
and CO2 out of the body
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Respiration and
Osmoregulation
• Water must be continuously moved
past the gills to keep blood oxygenated
– most bony fish ventilate gills by pumping
water across them
– very active fishes use ram ventilation—
continuously swimming forward at high
velocity with the mouth open
© 2006 Thomson-Brooks Cole
Respiration and
Osmoregulation
• Blood’s salt concentration is about 1/3
that of seawater, so water is lost
• Fish drink seawater to compensate
– chloride cells—specialized cells on the gills
which eliminate most of the excess salt
– kidneys and digestive tract remove other
excess salt
– marine fish excrete negligible amounts of
urine in order to retain maximum water
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Cardiovascular System
• Consists of heart, arteries, veins, and
capillaries
• Fish have a two chambered heart.
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Cardiovascular System
• Many active swimmers have a
countercurrent arrangement of blood
vessels
– maintains body-core temperature at 2-10o
C above seawater, increasing efficiency of
swimming muscles
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© 2006 Thomson-Brooks Cole
Buoyancy Regulation
• Most fish use a swim bladder—a gasfilled sac that helps offset the density
of the body and regulates buoyancy
– the fish can adjust the amount of gas in
the swim bladder to maintain depth
– gas is added as the fish descends and
removed as it ascends
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© 2006 Thomson-Brooks Cole
Buoyancy Regulation
• 2 methods for adjusting the amount of
gas in the swim bladder
– gulping air from the surface or spitting air
out as needed
– gas gland—a specialized gland which fills
the swim bladder from gases dissolved in
the blood
• fish with a gas gland empty gas from the swim
bladder through diffusion into the blood
• Active swimmers do not have swim
bladders, and must keep swimming
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Nervous System and Senses
• Taste and hearing
– taste receptors may be located on the
surface of the head, jaws, tongue, mouth
and barbels (whisker-like processes about
the mouth)
– bony fishes have a lateral line system for
detecting movement in the water
– ears are internal
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Nervous System and Senses
• Vision
– no eyelids
– eyes are usually set on the sides of the
head
– shallow-water species can perceive color
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Feeding Types
• Carnivores (e.g. pufferfish, groupers)
– most bony fishes are carnivores
– prey are usually seized, swallowed whole
• chewing would block water flow past gills
• Herbivores (e.g. surgeonfish, parrotfish)
– feed on a variety of plants and algae
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Feeding Types
• Filter feeders (e.g. anchovies, larvae)
– feed on plankton
– typically use gill rakers—projections from
the gill arches which filter phyto- and
zooplankton from seawater
– most travel in large schools, and are an
important food source for larger
carnivores
© 2006 Thomson-Brooks Cole
Adaptations to Avoid
Predation
• Many exhibit elaborate camouflage
• Pufferfishes and porcupinefish inflate
their bodies to deter predators
• Flying fishes use enlarged pectoral fins
to glide through the air and escape
• Pearlfish hide in other organisms
• Parrotfish secrete a mucus cocoon
• Surgeonfish are armed with razorsharp spines
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Adaptations to Avoid
Predation
• Clingfishes use a sucker to attach to
rocks so predators can’t dislodge it
• Triggerfish projects spines to deter
predators or wedge itself into cracks
• Scorpionfish and stonefish have venom
glands for self-protection
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Reproduction in Bony Fishes
• Sperm and eggs pass to the outside
through ducts, except in salmon
• Egg and sperm development is usually
seasonal
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Reproduction in Bony Fishes
• Pelagic spawners (e.g. tuna, wrasses)
– release vast quantities of eggs into the
water for fertilization by males
– fertilized eggs drift with the currents
– no parental care
• Benthic spawners (e.g. smelt)
– non-buoyant eggs with large yolks
– no parental care
– pelagic or benthic embryos/larvae
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Reproduction in Bony Fishes
• Brood hiders (e.g. grunion)
– species that hide their eggs in some way
but exhibit no parental care
• Guarders (e.g. damselfish)
– species that care for their offspring until
they hatch and, frequently, through their
larval stages
• Bearers (e.g. jawfish, seahorses)
– species that incubate their eggs until they
hatch (in the mouth or a special pouch)
© 2006 Thomson-Brooks Cole
Reproduction in Bony Fishes
© 2006 Thomson-Brooks Cole
Reproduction in Bony Fishes
© 2006 Thomson-Brooks Cole
Fish Migrations
• Migrations may occur within seawater or
between seawater and fresh water
(diadromous)
– catadromous—fishes that move from fresh water
to seawater to spawn
– anadromous—fishes that move from seawater to
fresh water to spawn
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Fish Migrations
• Freshwater eels
– best-studied catadromous fishes
– migrate down coastal rivers to the sea
during the fall
– adults spawn and then die
– young hatch, develop into leaf-like
leptocephalus larvae, and migrate back to
rivers
– after arrival, young metamorphose into
juveniles (elvers) that migrate into
streams and estuaries
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Fish Migrations
• Salmon
– Atlantic/Pacific species are anadromous
– Pacific species return to spawning grounds
once, reproduce, and die; Atlantic species
may spawn more than once
– lay eggs in a redd—a shallow depression
in the gravel of a fresh water stream
– salmon navigate upstream by the
characteristic odor of the stream; there is
not agreement on how they locate the
correct river’s mouth from the open sea
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole