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Fishes

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Feeding Behavior Herbivorous fishes eat plants and micro-algae. Most common on coral reefs parrotfishes, damselfishes, surgeonfishes. – PowerPoint PPT presentation

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Title: Fishes


1
Fishes
  • Chapter 24

2
Diversity
  • Fish has many usages extending beyond what are
    actually considered fishes today (e.g., starfish,
    etc.).
  • Fishes do not form a monophyletic group.
  • In an evolutionary sense, can be defined as all
    vertebrates that are not tetrapods.
  • Common ancestor of fishes is also an ancestor of
    land vertebrates.
  • Therefore in pure cladistics, would make land
    vertebrates fish.
  • Approximately 24,600 living species.
  • Adapted to live in medium 800 times denser than
    air.
  • Can adjust to the salt and water balance of their
    environment.

3
Diversity
  • Evolution in an aquatic environment both shaped
    and constrained its evolution.
  • Fish refers to one or more individuals of one
    species.
  • Fishes refers to more than one species.

4
Ancestry of Fishes
  • Fishes have descended from an unknown
    free-swimming protochordate ancestor.
  • Agnathans including ostracoderms.
  • Gnathostomes derived from one group of
    ostracoderms.
  • Four groups of gnathostomes flourished during the
    Devonian, two survive today.

5
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6
Fossils of Early Vertebrates
  • Armored, jawless vertebrates called ostracoderms
    had defensive plates of bone on their skin.
  • One group of ostracoderms led to the
    gnathostomes.

7
Fossils of Early Vertebrates
  • Placoderms, one group of early jawed fishes, died
    out during the Carboniferous.
  • Left no descendents.

8
Fossils of Early Vertebrates
  • Another group, the acanthodians, were common
    during the Devonian, but became extinct during
    the Permian.
  • They were distinguished by having heavy spines on
    all fins except the caudal (tail) fin.
  • Possible sister group of the bony fishes.

9
Fossils of Early Vertebrates
  • A third group of gnathostomes, the cartilaginous
    fishes (Class Chondrichthyes) lost the dermal
    armor and uses cartilage rather than bone for the
    skeleton.
  • Sharks, skates, rays, chimaeras.

10
Fossils of Early Vertebrates
  • The last group, the bony fishes, are the dominant
    fishes today.
  • Ray-finned fishes include most modern bony
    fishes.
  • Lobe-finned fishes contain few living species.
  • Includes sister group of tetrapods.
  • Lung fishes coelacanths.

11
Origins of Bone and Teeth
  • Mineralization appears to have originated with
    vertebrate mouthparts.
  • The vertebrate endoskeleton became fully
    mineralized much later.

12
Agnathans
  • The least derived vertebrate lineages that still
    survives are class Myxini, the hagfishes and
    class Petromyzontida, the lampreys.
  • They lack jaws, internal ossification, scales,
    and paired fins.
  • Pore-like gill openings along the side of the
    body.

13
Class Myxini - Hagfish
  • Entirely marine.
  • Feeds on annelids, molluscs, crustaceans, dead
    or dying fishes.
  • Predators or scavengers.

14
Class Myxini - Hagfish
  • Hagfishes are jawless marine vertebrates that
    have a cartilaginous skull and axial rod of
    cartilage derived from the notochord.
  • They lack vertebrae.

15
Class Myxini - Hagfish
  • A hagfish can tie itself in knots to increase
    leverage when burrowing into a dead fish.
  • Produces large amounts of slime.

16
Class Petromyzontida - Lampreys
  • Lampreys (Class Petromyzontida) are found in
    fresh and saltwater.
  • Lampreys have cartilaginous segments surrounding
    the notochord and arching partly over the nerve
    cord.

17
Class Petromyzontida - Lampreys
  • All ascend freshwater streams to breed.
  • Marine forms are anadromous.
  • Freshwater forms move between lakes streams.

18
Class Petromyzontida - Lampreys
  • Lamprey larvae are called ammocoetes.
  • Larvae look much like amphioxus.
  • Possess basic chordate characteristics in
    simplified form.
  • Suspension feeders.

19
Class Petromyzontida - Lampreys
  • Many are parasitic as adults.
  • Those that are not, do not feed as adults.

20
Derived Characters of Gnathostomes
  • Gnathostomes have jaws that evolved from skeletal
    supports of the pharyngeal slits.

21
Derived Characters of Gnathostomes
  • Other characters common to gnathostomes include
  • Enhanced sensory systems, including the lateral
    line system.
  • An extensively mineralized endoskeleton.
  • Paired appendages.

22
Fossil Gnathostomes
  • The earliest gnathostomes in the fossil record
    are an extinct lineage of armored vertebrates
    called placoderms.

23
Fossil Gnathostomes
  • Another group of jawed vertebrates called
    acanthodians radiated during the Devonian period.
  • Closely related to the ancestors of osteichthyans
    (bony fishes).

24
Class Chondrichthyes
  • Members of class Chondrichthyes have a skeleton
    that is composed primarily of cartilage.
  • The cartilaginous skeleton evolved secondarily
    from an ancestral mineralized skeleton.

25
Subclass Elasmobranchii
  • The largest and most diverse subclass of
    Chondrichthyes, Elasmobranchii, includes the
    sharks and rays.

26
Subclass Elasmobranchii
  • Most sharks have a streamlined body and are swift
    swimmers.
  • Heterocercal tail the upper lobe of the tail is
    longer than the lower.
  • Placoid scales.
  • The upper lower jaws have a front, functional
    row of teeth and several developing rows growing
    behind as replacements.

27
Subclass Elasmobranchii
  • Spiral valve in intestine slows passage of food
    and increases absorptive area.
  • Large fatty liver aids in buoyancy.

28
Subclass Elasmobranchii Acute Senses
  • Prey is initially detected using large olfactory
    organs.
  • Mechanorecptors in the lateral line system sense
    low-frequency vibrations from far away.
  • Vision is important at close range.
  • Bioelectric fields surrounding their prey can be
    detected using electroreceptors in the ampullae
    of Lorenzini on the sharks head.

29
Subclass Elasmobranchii
  • All chondrichthyans have internal fertilization.
  • Oviparous species lay large yolky eggs soon after
    fertilization.
  • Some lay eggs in a capsule called a mermaids
    purse that often have tendrils to attach it to a
    some object.

30
Subclass Elasmobranchii
  • Ovoviviparous species retain developing young in
    the uterus while they are being nourished by the
    yolk.

31
Subclass Elasmobranchii
  • In viviparous species, young receive nourishment
    from the maternal bloodstream through a placenta,
    or from nutritional secretions produced by the
    mother.
  • Some receive additional nutrition by eating eggs
    siblings.
  • Parental care ends as soon as eggs are laid or
    young are born.

32
Subclass Elasmobranchii
  • Skates and rays are specialized for bottom
    dwelling with a flattened body and enlarged
    pectoral fins.
  • Gill openings on ventral surface.
  • Water enters through spiracles on dorsal surface.

33
Subclass Elasmobranchii
  • Stingrays have a slender whip-like tail with one
    or more saw-edged spines with venom glands at the
    base.
  • Electric rays have large electric organs that can
    discharge high-amperage, low voltage current into
    the surrounding water.

34
Subclass Holocephali
  • A second subclass is composed of a few dozen
    species of chimaeras, or ratfishes.
  • Flat plates instead of teeth.
  • Upper jaw fused to cranium.

35
Osteichthyes
  • Osteichthyes are the bony fishes.
  • Bone replaces the cartilage during development.
  • A swim bladder is present for controlling
    buoyancy and respiration in some.
  • Not a monophyletic group.

36
Osteichthyes
  • Fishes breathe by drawing water over four or five
    pairs of gills located in chambers covered by a
    protective bony flap called the operculum.

37
Class Actinopterygii
  • Ray-finned fishes (class Actinopterygii) contain
    all the familiar bony fishes more than 23,600
    species.

38
Class Actinopterygii
  • The fins, supported mainly by long, flexible rays
    are modified for maneuvering, defense, and other
    functions.

39
Class Actinopterygii
  • Two main groups of ray-finned fishes.
  • Chondrosteans (e.g. sturgeons) have heterocercal
    tails and ganoid scales.

40
Class Actinopterygii
  • Neopterygians one lineage of early
    neopterygians led to the modern bony fishes
    (teleosts).
  • Early type neopterygians include the bowfin and
    gars.

41
Class Actinopterygii
  • The major lineage of neopterygians are teleosts,
    the modern bony fishes.
  • Changes in fins increased maneuverability and
    speed.
  • Symmetrical, homocercal, tail allows increased
    speed.

42
Teleosts
  • Thinner, lighter cycloid and ctenoid scales
    replace the heavy dermal armor of primitive
    ray-finned fishes. Some (e.g. eels) lack scales.

43
Teleosts
  • Fins diversified for a variety of functions
    camouflage, communication, complex movements,
    streamlining, etc.

44
Teleosts
  • The swim bladder shifted purpose from primarily
    respiratory to buoyancy.
  • Gill arches in many diversified into pharyngeal
    jaws for chewing, grinding, and crushing.

45
Class Sarcopterygii
  • Lobed-finned fishes (class Sarcopterygii) include
    2 species of coelacanths and 6 species of
    lungfishes.
  • This group was much more abundant during the
    Devonian.
  • Rhipidistians are an extinct group of
    sarcopterygians that led to tetrapods.

46
Class Sarcopterygii
  • All early sarcopterygians had lungs as well as
    gills and a heterocercal tail.
  • Later sarcopterygians have a continuous flexible
    fin around the tail.
  • They have fleshy, paired lobed fins that may have
    been used like legs to scuttle along the bottom.

47
Class Sarcopterygii
  • Some lungfishes can live out of the water for
    long periods of time.
  • During long dry seasons, the African lungfish can
    burrow down into the mud and secrete lots of
    slime forming a hard cocoon where they will
    estivate until the rains return.

48
Class Sarcopterygii
  • Coelocanths arose during the Devonian and peaked
    (max. species) in the Mesozoic.
  • One genus, two species currently.
  • Believed to be extinct for 70 million years,
    rediscovered in 1938.
  • The second species was discovered in 1998.

49
Locomotion in Water
  • Fishes use trunk and tail musculature to propel
    them through the water.
  • Musculature is composed of zigzag bands called
    myomeres.

50
Locomotion in Water
  • Flexible fishes like eels use a serpentine
    movement.
  • Not very efficient for high speed.
  • Fast swimmers are less flexible.
  • Body undulations limited to caudal region.

51
Locomotion in Water
  • Many fast swimmers are streamlined with grooves
    so their fins can lie flat.

52
Buoyancy
  • Sharks must move constantly to avoid sinking.
  • The heterocercal tail provides lift as it moves
    from side to side.
  • Broad head and angled, stiff fins add lift.
  • Their large livers with fatty hydrocarbons aid in
    buoyancy as well.
  • Liver is like a large sack of buoyant oil.

53
Buoyancy
  • Bony fishes use a gas-filled space to regulate
    buoyancy the swim bladder.
  • Derived from a pair of lungs.
  • Swim bladders are absent in tunas, abyssal
    fishes, many bottom dwellers.
  • Bony fishes will sink without the swim bladder
    because they are denser than water.

54
Buoyancy
  • Fishes must be able to regulate gas inside the
    swim bladder.
  • At depth, the gas will compress and the fish will
    sink.
  • As it rises to the surface, the gas will expand
    and the fish will rise faster.
  • Gas may be removed in two ways.

55
Buoyancy
  • Physostomous fishes (more primitive, e.g. trout)
    have a pneumatic duct that connects the swim
    bladder and the esophagus.
  • Air can be expelled through the duct.
  • Gas must be secreted into the swim bladder from
    the blood, although some species can gulp air to
    fill the swim bladder.

56
Buoyancy
  • Physoclistous fishes (more derived, e.g. advanced
    teleosts) the pneumatic duct has been lost. Gas
    must be absorbed by blood from the highly
    vascularized ovale.
  • Gas is secreted into the swim bladder from the
    blood at the gas gland.

57
Hearing
  • The bodies of fishes are nearly the same density
    as water.
  • Makes hearing difficult.
  • Weberian ossicles, found in minnows, suckers,
    catfish, improves hearing.
  • Sound detection starts in swim bladder (sound
    vibrates easily in air) and is transmitted to the
    inner ear by Weberian ossicles.

58
Respiration
  • Fish gills are composed of thin filaments covered
    with an epidermal membrane that is folded into
    lamellae.
  • Richly supplied with blood vessels.
  • Located inside the pharyngeal cavity.
  • Covered with an operculum in bony fishes.
  • Elasmobranchs have gill slits.

59
Respiration
  • Water must be continuously pumped over the gills.
  • A countercurrent system is found where the flow
    of water is opposite to the flow of blood.
  • Deoxygenated blood encounters the freshest water
    with the highest oxygen content.

60
Osmotic Regulation
  • Freshwater fishes (hyperosmotic regulators) must
    have a way to get rid of water that enters their
    bodies by diffusion through the gills.
  • Water enters the body, salts are lost by
    diffusion.
  • Water is pumped out by the opisthonephric kidney
    which can form very dilute urine.
  • Salt absorbing cells in the gill actively move
    salt from the water into the blood.

61
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62
Osmotic Regulation
  • Saltwater fishes (hypoosmotic regulators) have a
    lower blood salt concentration than the seawater.
  • Tend to lose water and gain salts.
  • Marine teleosts drink seawater.
  • Salts are carried by the blood to the gills where
    they are secreted out by salt-secretory cells.
  • Other salts are voided with feces or excreted by
    the kidney.

63
Feeding Behavior
  • Most fishes are carnivores and prey on everything
    from zooplankton to large vertebrates.
  • Some deep-sea fishes can eat victims twice their
    size an adaptation to scarce food.
  • Most fishes cant chew with their jaws (this
    would block water flow over the gills), many have
    pharyngeal teeth in their throats.
  • Large-mouthed predators can suck prey in by
    suddenly opening their mouths.

64
Feeding Behavior
  • Herbivorous fishes eat plants and micro-algae.
  • Most common on coral reefs parrotfishes,
    damselfishes, surgeonfishes.
  • And tropical freshwater habitats minnows,
    characins, catfishes.

65
Feeding Behavior
  • Suspension feeders filter microorganisms from the
    water using gill rakers.
  • Herring-like fishes are common menhaden,
    herring, anchovies etc.
  • Many larval fishes.
  • Basking sharks.
  • Most are pelagic fishes that travel in large
    schools.

66
Feeding Behavior
  • Other groups are scavengers that eat dead and
    dying animals,
  • Detritivores that consume fine particulate
    organic matter,
  • Parasites that consume parts of other live fishes.

67
Migration
  • Freshwater eels are catadromous, they enter the
    ocean as adults, migrate to a spawning area where
    they spawn then die.
  • Larvae make their way back to the streams only
    females enter the streams.

68
Migration
  • Anadromous salmon spend their lives at sea,
    returning to freshwater to spawn.
  • Die after spawning.
  • Strong homing instinct brings them to their
    parent stream.
  • Guided by odor of parent stream.

69
Reproduction
  • Most fishes are dioecious with external
    fertilization and external development
    oviparity.
  • Ovoviviparous species (guppies, mollies,
    surfperches) bear live young after development in
    the ovarian cavity of the female.

70
Reproduction
  • Fertilized eggs may be pelagic and hatch into
    pelagic larvae.
  • Large yolky benthic eggs are often attached to
    vegetation or deposited in nests, buried, or even
    carried in the mouth.
  • Many benthic spawners guard their eggs.
  • Usually the male.

71
Reproduction
  • In some species, males defend nest sites and
    perform courtship rituals to entice females to
    lay their eggs in his nest. Sometimes, several
    females will lay eggs in a nest.
  • The male will guard the eggs from predators and
    will also fan them with his fins to aerate them.

72
Growth
  • Larvae may depend on the yolk sac until their
    mouths and digestive systems are fully developed.
  • Larvae then forage for their own food.

73
Growth
  • Larvae metamorphose into juveniles with body
    shape color patterns usually similar to the
    adults.
  • Some species have different color patterns in
    juveniles.

French Angelfishes (Pomacanthus paru) juvenile
(left) and adult (right).
74
Growth
  • Growth is temperature dependent.
  • Fish grow faster in summer when the temperature
    is warm and food is plentiful.
  • Growth may nearly cease during the winter.
  • Annual rings in scales, otoliths, and other bony
    parts reflect seasonal growth.
  • Fish continue to grow throughout life.
  • Larger fishes produce more gametes.
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