Transcript Marine Fish

Phylum Chordata
 Dorsal hollow nerve cord
 Pharyngeal gill slits
 Notochord
Subphylum Vertebrata
 Backbone made of hollow connecting bones
(vertebrae); permits rapid efficient locomotion
 Spinal cord ending in a complex brain
 Bilateral symmetry
 Endoskeleton
Fish – 58% are marine
 First vertebrates to evolve
 Probably evolved from invertebrate chordate – Fig. 7
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Most are economically important marine organisms
Used for sport & aquariums
Usually covered with scales and have fins
Poikilothermic (cold blooded)
O2 and CO2 exchange through gills
Three Classes of Fish
 Agnatha – jawless fish
Jawless fish – Class Agnatha – Fig. 8-2
 Lampreys (mostly fresh H2O) & hagfish (marine)
 Most primitive
 Lack true jaws – feed by suction
 Lack paired fins (pectoral & pelvic) & scales
 Gill openings separate & external
 Cartilaginous skeleton
 Notochord persists throughout life
Three Classes of Fish
 Chondrichthyes -
cartilaginous fish
Cartilaginous Fish – Class Chondrichthyes –
Fig. 8-3 – 8-7
 Sharks, skates, rays, & ratfishes
 Cartilaginous skeleton – lighter & more flexible than
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bone
Jaws; mouth typically ventral
Notochord replaced by vertebrae in adults
Gill opening separate
Paired pectoral & pelvic fins; plus dorsal, anal, & tail
fin
Tail fin usually asymmetrical
Skin has tiny pointed scales with very little overlapping
– Fig. 8-8
Three Classes of Fish
 Osteichthyes – bony fish
Bony Fish – C lass Osteichthyes
 Spotted bass, flounder, salmon, tuna
 Body skeletons
 Jaws present with mouth usually terminal; provides
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more freedom of movement
Notochord replaced by vertebrae in adults
Gill openings all covered by a single operculum
(protects)
Paired pectoral & pelvic fins (not as fleshy as sharks),
dorsal, anal, & tail fins
Tail (caudal) fin is usually symmetrical
Scales are thin, flexible & overlapping and are covered
by a thin layer of tissue & mucus.
Swim bladder – gas filled sac that allows fish to adjust
buoyancy so it can float at any depth without exerting
its’ muscles
 http://www.youtube.com/watch?v=letqkpG3b5Q
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(hagfish feeding on whale carcass)
Slime, or mucus is used by many animals both on land
and in the sea, but Hagfish have the outstanding
ability to defend themselves by producing an
incredible slime when touched. It comes from the
glands along the side of their body, and within
minutes literally liters of it can be produced.
http://www.youtube.com/watch?v=pmaal7Hf0WA&N
R=1 (hagfish slime)
http://www.youtube.com/watch?v=yihoIvUBDM4
(manta ray feeding frenzy)
http://www.oceanfootage.com/video_clips/ST05_038
(tuna)
Ichthyology – Study of Fish
 Body shape – Form fits function – Fig. 8-9
 Very fast swimmers, streamlined bodies, laterally
compressed – tunas, sharks
 Bottom dwellers – have flattened bodies
 Living among vegetation or rocks – need very elongated
flexible/bendable body – eel, gunnel
 Slow swimmers – bodies are elongate on a vertical plane
(seahorse), triangular ( trunkfish) or round (porcupine)
 Shape of body can also be a form of camouflage –
resembles the area in which they live
Ichthyology – Study of Fish
 Coloration – can be used as camouflage or warning;
sometimes color changes reflect mood or reproductive
condition
 Chromatophores – specialized pigment cells found in
the skin; fish change color by contracting & expanding
pigment molecules in these cells
 http://video.google.com/videoplay?docid=125655308012313047#
 Aposematic (warning) coloration – warns potential
predators to stay away & not attack; protects best against
predators that can learn
 Cryptic coloration – blending with the environment to
deceive predator or prey – Fig. 8-10a
Aposmatic coloration
Ichthyology – Study of Fish
 Coloration (cont.)
 Disruptive coloration – presence of stripes, bars or spots
that break up outline of fish making it harder to see in
the dappled underwater light
 Countershading – open water disguise
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Silver or white bellies blend with light at surface when viewed
from below
Dark blue, black, grey backs blend with bottom when viewed
from above
Ichthyology – Study of Fish
 Locomotion – obtain food, escape from predators &
find mates; many cartilaginous fish swim to keep H2O
moving over their gills to obtain O2 – Fig. 8-11
 Most fish swim in sinuous motion (S – shaped waves)
that moves from head toward caudal fin
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Some fish use only their fins - Fig. 8-12
Myomeres – bands of muscles
http://www.youtube.com/watch?v=o81WIfjrt5I (shark
swimming)
 To aid buoyancy
 Sharks have stiff pectoral fins that increase lift, asymmetric
tail causes the head to be pushed upward, large amount of oil
in liver causes an increase in buoyancy
 Bony fish – swim bladder present, therefore fins are smaller
and can be used for greater mobility
Ichthyology – Study of Fish
 Feeding – wide variety of structural adaptations; form
fits function – Fig. 8-13
 Mainly carnivorous
 Some are filter feeders
 http://www.youtube.com/watch?v=caiMgEnRw7o
(basking shark feeding)
Ichthyology – Study of Fish
 Digestion – Fig. 8-14
 Mouth  esophagus  stomach  intestine  cloaca
 anus
 Stomach – chemical & mechanical breakdown
 Intestine – most absorption of nutrients, spiral valvew in
sharks increases surface area
 Cloaco – found only in cartilaginous fish, common
pathway for digestive, excretory & reproductive system
 Accessory organs include pancreas & liver which
secrete digestive enzymes
 Carnivores tend to have shorter and straighter
intestines; plant eating fish have coiled intestines
because they need more surface area to digest plants
Ichthyology – Study of Fish
 Circulatory System – Fig. 8-15
 Closed – blood always contained in vessels
 Two chambered heart – blood only passes through the
heart once (single circulation)
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Advantage of single circulation – all the blood going to the
body has already been oxygenated in the gills
Disadvantage – after the blood passes through narrow gill
capillaries the blood pressure is greatly reduced, this slows the
rate of O2 delivery to the cells and limits the metabolic rate
the fish can swim
Ichthyology – Study of Fish
 Respiratory System – Fig. 8-16, 8-17
 Respiratory surface – gills, exchange of CO2 and O2;
dissolved O2 from water must be constantly moved over
gills
 Irrigation of gills
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Cartilaginous fish – water enters through mouth & spiracles;
when mouth is shut contractions of the walls of pharynx and
gills slits causes water to move over the gills and out
Bony fish – operculum is shut when fish opens mouth &
expands pharynx causing water to be sucked in; when mouth
closes, the operculum opens and water flows over the gills and
out
Ichthyology – Study of Fish
 Respiratory System (cont.)
 Structure of gills
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Gills supported by a gill arch
Gill racker keeps food from flowing into gills (may be
specialized for filtering in filter feeders)
Gills are divided into gill filaments which contain many thin
plates called lamellae (increase surface area)
Ichthyology – Study of Fish
 Respiratory System (cont.)
 Countercurrent gas exchange – an anatomical structure
for manipulating a gradient so as to maximize uptake of
O2 – Fig. 8-17
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The direction of blood flow through the capillaries in the
lamellae is opposite that of H2O flowing over the lamellae
(remember – O2 diffuses down its concentration gradient)
 Hemoglobin – iron containing protein molecule in
RBC’s that carry O2 & CO2
 Myoglobin – protein molecule that can store large
amounts of O2
Ichthyology – Study of Fish
 Regulation of the Internal Environment – Fig. 8-18
 Cartilaginous fish – reduce osmosis by increasing solute
concentration of blood
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Retain urea which causes and increase in blood solute
concentration
Absorbs H2O through gills & skin
Excess salts are excreted by kidneys, intestine, & rectal gland
 Bony fish – reduce osmosis
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Drinks seawater
Excess salt secreted by gills
Excretes small amounts of concentrated salty urine
Ichthyology – Study of Fish
 Nervous System & Sensory Organs – Fig. 8-19 – CNS
consists of the brain & spinal cord, PNS consists of
nerves extending out from the CNS to all parts of the
body
 Messages are relayed by electrical & chemical signals
 NS integrates with the endocrine system
 Olfactory – sense of smell (chemoreceptors)
 Olfactory sacs on each side of the head pick up
“chemical” scents in the water which triggers a signal
which travels to the brain
Ichthyology – Study of Fish
 Nervous System & Sensory Organs (cont.)
 Gustatory – sense of taste; chemorecep5ors on taste
buds & barbels pick up “chemical” scents
 Sight – photoreceptors (rods & cones) contain light
sensitive pigments
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Nictitating membrane – found in sharks (protects eye)
 Pressure – lateral line – Fig. 8-19; mechanoreceptor
(pressure) stimulated by water displacements caused by
other animals or sounds  Ampullae of Lorenzini – sense organ in cartilaginous
fish that detects weak electrical fields
 Sound – mechanoreceptors in fluid filled canals of inner
ear that detect changes in pressure caused by vibrations
& also are involved in equilibrium & balance
 http://www.youtube.com/watch?v=N3CXUO0jxNQ
(lateral line)
barbels
http://dsc.discovery.com/videos/ultimate-guide-the-sharksvibrations-and-shark-vision.html
http://dsc.discovery.com/videos/ultimate-guide-the-sharksshark-smell.html
Ichthyology – Study of Fish
 Behavior – used to adapt to physical factors; find food,
shelter; prey/predator; courtship & reproduction – Fig.
8-20 – 8-23
 Territoriality – defending home areas against intruders
to possibly ensure food & shelter & mates which may be
limited; usually involves some type of aggressive
behavior that is designed to frighten “predators”; actual
fights & fatalities are rare
 Schooling – well defined groups that function as well
coordinated units – Why school?
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Protection against predation
Increase swimming efficiency
Increase hunting efficiency
http://www.youtube.com/watch?v=25xV1IcctfA&feature=relat
ed
Ichthyology – Study of Fish
 Behavior (cont.)
 Migration – regular mass movements from one place to
another; most migrations seem to be related to feeding
and/or reproduction
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Navigate by using geographical features, currents, salinity,
chemicals, temp., earth’s magnetic field, light
Anadromous – fish that live in ocean but migrate to fresh H2O
to breed – salmon – Fig. 8-23
Catadromous – fish that live in fresh H2O but migrate to the
ocean to breed – eel – Fig. 8-24
Ichthyology – Study of Fish
 Reproduction & Life History – sexes usually separate
with both sexes having paired gonads (ovaries/testes)
 Reproductive systems
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Cloaca – in cartilaginous fish a common pathway for digestive,
excretory & reproductive system
Urogenital opening – opening for urine (excretory) & gametes
(reproductive); (digestive system has separate opening – anus)
Gamete production usually happens only during certain
periods of time when conditions are most favorable
Timing of gamete production is controlled by the release of
sex hormones which may be triggered by some environmental
factor such as temp., light, availability of food
Ichthyology – Study of Fish
 Reproduction & Life History (cont.)
 Reproductive systems (cont.)
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A few are hermaphrodites (have male and female reproductive
organs)
Sex reversal – males  females or females  males; probably
influenced by presence or absence of hormones &
pheromones
Ichthyology – Study of Fish
 Reproduction & Life History (cont.)
 Reproductive behavior – various adaptations to get
individuals together
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Migrate
Color changes to advertise readiness elaborate courtship
behaviors
Ichthyology – Study of Fish
 Reproduction & Life History
 Mating
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Copulation – transfer of sperm into females (internal
fertilization); usually found in cartilaginous fish; claspers –
Fig. 8-26
Spawning – release of gametes into water (external
fertilization); usually found in bony fish – Fig. 8-25
Remember the number of gametes produced usually
corresponds to parental involvement after fertilization (i.e. –
large number of gametes, no parental involvement – Fig. 8-27
Ichthyology – Study of Fish
 Reproduction & Life History
 Early development
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Ovoviviparous – eggs develop inside female and she gives
birth to live young; nutrients are received from yolk sac,
mostly cartilaginous fish – ex. Sharks
Oviparous – eggs develop free in the water; nutrients are
received from yolk sac – Fig. 8-30
http://dsc.discovery.com/videos/ultimate-guide-the-sharksshark-birth-and-maturation.html
Viviporous – nutrition absorbed from walls of mothers
reproductive tract ; live bearers