Transcript Fish - TypePad

• Most fish have 7 fins.
• Many fishes have well-developed eyes and a keen sense of
vision that they rely upon to find and capture food, avoid
predation, locate shelter and find a mate. Many fishes see color
and some are able to see in very low light levels.
• Comprising close to 80 percent of the body of many fishes,
muscles provide power.
• Fish are in a group called Craniata which describes a skull that
surrounds the brain, olfactory organs, eyes, and inner ear.
• Zoologists do not know what animals were the first craniates
were. Evidence suggests that the craniate lineage may go back
about 750 million years.
• Recent cladistic analysis indicates that a group of fish called
Hagfishes are the most primitive living Craniates.
• They have no endoskeleton.
• They breath through gills. They have
seven or more gill pouches which are
supported by bronchial arches.
• They have a closed circulatory system
with a two chambered heart.
• There are two sexes and reproduction
involves internal fertilization. They do
not have any signs of raising their
young.
• Includes the Hagfish and the Lamprey.
• They do not endoskeleton, the only part that is considered bone are
the teeth and the jaw. Everything is made of placoid scales.
• They breath through 5 to 7 gills. They lack a swim bladder so they
have to keep swimming in order to keep the water moving across
their gills.
• They have a closed circulatory system with a 2 chambered heart.
• They do not lay eggs and do not raise their young. They use internal
fertilization and their young go through direct development.
• This group includes the Sharks, Rays, Ratfish and Skates
• They are the only group with actual bones.
• They breath through 3 gill slits but some fish such as the lungfish
can breath through lungs.
• The have a close circulatory system with a heart that has 3
valves.
• They are dioecious an fertilize both internally and externally.
Some bony fish do raise their young.
• Fish move through the water using their fins and body wall to
push against the surrounding water.
• Fish tend to have five fins. The dorsal fin, caudal fin, anal fin,
pelvic fin, and the pectoral fin.
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Dorsal Fin-This fin is used for balance and staying upright
Caudal Fin-This is also known as the tail and used for forward movement.
Anal Fin-This fin is also used for balance
Pelvic Fin and Pectoral Fin- These fins are use to help the fish steer through
the water.
• The muscles are arranged in a sideways W pattern. The muscle
bundles extend posteriorly and anteriorly in a zigzag fashion,
contraction
• Most likely the earliest fist here filter feeders and
scavengers that sifted through the mud of the sea
floor
• Modern fish are predators and spend the
majority of their time searching for food.
• Prey can vary greatly from fish to fish. Some fish
feed on invertebrate animals, but many fish feed
on other vertebrates.
• Fish will usually swallow prey hold, some fish also
have teeth that are modified for crushing shells.
Some fish such as the herring, paddlefishes and
the whale shark are filter feeders.
• Filter feeders have a long gill process called gill
rakers that trap plankton while the fish swims
through the water with their mouths open.
• The digestive tract of a fish is very similar to
that of other vertebrates.
• The stomach is used to store large infrequent
meals.
• The small intestine is the primary site for
enzyme excretion and food digestion.
• Sharks and other Elasmobranchs have a
spiral valve in their intestine
• Boney fish poses out pockets of the intestine
called the pyloric ceca which increase
absorptive and secretory surfaces.
• Swim Bladder-a gas-filled sac, usually along
the dorsal body wall of bony fishes. It is an
out growth of the digestive tract and
regulates the buoyancy of a fish
• All vertebrates have a closed circulatory system where a heart
pumps blood, with red blood cells containing hemoglobin
through a series of arteries, capillaries and veins.
• In most fish the blood passes through the heart once with every
circuit around the body.
• A few fish like the lungfish have lungs and the pattern of
circulation is altered.
• In the lungfish the path to the gills is the same but a vessel to the
lungs has developed as a branch of the aortic arch.
• Operculum-The cover of a gill chamber of a boney fish.
• Fish live in a place that contains less than 2.5% present oxygen.
• Most fish have a muscular pumping mechanism to move the
water from the mouth, into the pharynx, over the gills and out
through the gill openings.
• This is achieved by muscles that surround the pharynx and the
opercular cavity which is between the gills and the operculum.
• Some sharks and open ocean fish such as the tuna maintain
water flow by keeping their mouths open. This method is known
as Ram Ventilation.
• Gas exchange occurs at a spot called the Pharyngeal Lamellae
• The gill arches support two rows of gill filaments. Blood flows
into these filaments through branchial arteries which break into
capillary beds within the lamellae.
• Water and blood flow in opposite directions on either side.
Water between the lamellae is saturated with oxygen. The
water will always loose oxygen because it always encountering
blood with a lower oxygen concentration.
• Gill arches-these support the gills
• Gill filaments-extend from each gill arch and include vascular
folds called the pharyngeal lamellae
• Counter current exchange mechanism-provides very efficient
gas exchange by maintaining a concentration gradient between
the blood and the water over the entire length of the capillary
bed.
• Cloaca- A common opening for excretory, digestive, and
reproductive systems
• Most fish have chambers called pneumatic sacs. Air enters these
sacs and gas exchange occurs across the vascular surface. This is
use by fish such as the Indian Climbing Perch, Lungfish. In this
case they act as lungs. In other fish they are used as swim
bladders.
• Like most vertebrates the nervous
system includes a brain and a spinal
chord.
• Sensory structures are widely
distributed over the body in addition to
structures for touch, water temperature,
vision, hearing, equilibrium and
balance and detecting water
movements.
• Fish have what are call external nares,
these are openings that lead to
olfactory receptors. They eyes of a fish
are similar to other vertebrates but
have no eyelid.
• Just like other vertebrates the receptors
for equilibrium, balance and hearing
are in the inner ear of a fish.
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Semicircular canals detect the rotational movement while other
sensory patches help with equilibrium and balance by
detecting the gravitational pull.
Fish can hear, vibrations pass from the water through the
bones of the skull to the middle ear, and some fish have chains
of bony ossicles that connect the back of the skull to the swim
bladder in which the vibrations strike the fish, amplified by the
swim bladder and sent to the skull through the ossicles
All fish have what is called a Lateral-Line System this consists
of sensory pits in the epidermis that connect to canals just
beneath the epidermis. These are used to detect water
currents, or a predator or prey.
• Some fish are capable of Electroreception. This is the ability to
detect electrical fields that fish and other organisms generate.
• This ability has been demonstrated in over 500 species in seven
families of Chondrichthyes and Osteichthyes. This ability is also
highly evolved in sharks and rays
• The best known fish for producing and electric current is the
electric Eel
• The organs that produce the currents are in the trunk of the eel
and can deliver shocks that exceed 500 volts.
• Osmoregulation is a major function of the
kidneys and gills of fish.
• Kidneys are located close to the midline of
the body, dorsal to the peritoneal
membrane that lines the body cavity.
• The excretory structures are called nephrons
and can be found in all vertebrates.
• Nephrons filter blood borne nitrogenous
wastes, ions, water and small organic
compounds across a network of capillaries
called a glomerulus
• Filtrate passes into a tubule system where
the nutrients is absorbed then finally
excreted
• Cloaca-A common opening for excretory,
digestive, and reproductive systems.
• Freshwater fish live in an environment
containing few substances.
• To control excess water buildup and ion
loss by never drinking and only taking
in water when they are feeding.
• Freshwater fish have very short tubular
systems so little water is reabsorbed.
This makes fish produce large quantities
of dilute urine.
• Active transport of ions into the blood
at the gills compensates for this loss of
ions.
• Marine fish have the opposite problem. The environment they
live in contains 3.5% ions and their tissues contain 0.65%
• They drink water and eliminate excess ions by excretion,
defecation, and active transport across gill surfaces.
• The nephrons of marine fish possess small glomeruli and long
tubule systems.
• Fish will often produce large number of
eggs with the hopes that they will be
fertilized by the sperm of a male.
• Most of the fish are oviparous which
means that the eggs develop outside of
the female from the stored yolk.
• Some fish have special structures for
sperm transfer. Fish like sharks have
modified pelvic fins called claspers
• In many cases care of the embryos is
limited or nonexistent. Some fish will build
and tend nests.
• Some of the best brooders are the
seahorses
• Craniata
• Skull surrounds the brain, olfactory organs, eyes and inner ear. Unique embryonic tissue, neural crest,
contributes to a variety of adult structures, including sensory nerve cells and some skeletal and other
connective tissue structures.
• Subphylum Hyperotreti
• Fishlike; skull consisting of cartilaginous bars; jawless; no paired appendages; mouth with four pairs of
tentacles; olfactory sacs open to mouth cavity; 5 to 15 pairs of pharyngeal slits; ventrolateral slime
glands. Hagfish
• Subphylum Vertebrata
• Vertebrae surround nerve chord and serve as primary axial support.
• Hyperoartia
• A large, sucker-like mouth, reinforced by cartilage. Gill arches with spine-shaped processes.
• Class Cephalaspidomorphi
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Sucking mouth with teeth and rasping tongue; seven pairs of pharyngeal slits; blind olfactory sacs. Lampreys
• Gnathostomata
• Hinged jaws and paired appendages; vertebral column may have replaced notochord; three
semicircular canals
• Class Chondrichthyes
• Tail fin with large upper lobe; cartilaginous skeleton; lack opercula and a swim bladder or lungs. Sharks,
skates, rays, ratfishes.
• Subclass Elasmobranchii
• Cartilaginous skeleton may be partially ossified; placoid scales or no scales or no scales. Sharks,
Skates Rays
• Subclass Holocephali
• Operculum covers pharyngeal slits; lack scales; teeth modified into crushing plates; lateral-line
receptors in an open groove. Ratfishes.
• Class Osteichthyes
• Subclass Sarcopterygii
• Paired fins with muscular lobes; pneumatic sacs function as lungs. Lungfishes and coelacanths
• Subclass Actinopterygii
• Paired fins supported by dermal rays; basal portions of paired fins not especially muscular; tail fin
with approximately equal upper and lower lobes; blind olfactory sacs.