Marine%20Fishes

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Chapter 10 Marine Fishes
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• Vertebrate
• Jawless vertebrates jawless fish
• Jawed vertebrates
• Fish
• Chondrichtyes
• Osteichtheyes
• Amphibians
• Reptiles
• Birds
• Mammals

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• First well talk about fish
• Jawless fish
• Jawed fish
• Cartilaginous fish Class Chondrichthyes
• Chimeras and ratfish
• Elasmobranchs sharks, skates and rays
• Class Osteichthyes
• Lobed fin fish
• Ray finned fish

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Fishes

• Fishes are vertebratesanimals that possess
  vertebrae, a series of bones or cartilages that
  surround the spinal cord and help support the
  body
• Primitive fishes lacked paired fins and jaws
• Adaptation of jaws and paired fins allowed fish
  to more efficiently obtain food ultimately
  replacing all but a few jawless forms.

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Jawless Fishes

• Hagfish and Lampreys
• Lack both jaws and paired appendages
• Have skeletons of cartilage (no bone)
• Lack scales
• Hagfish also lack vertebrae (some scientists
  consider them invertebrates), recent DNA evidence
  indicates that they are most closely related to
  lampreys

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Hagfishes

• Bottom dwelling slime eels
• Skins are used to make leather goods
• Slime glands produce abundant milky, gelatinous
  fluid for protection if hagfish is disturbed

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Lampreys

• Have oral disk and rasping tongue covered with
  horny dentacles to grasp prey, rasp hole in the
  body and suck out tissue and fluid.

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Cartilaginous Fishes

• Class Chondrichthyes
• sharks, skates, rays, chimaeras
• Skeleton of cartilage
• Possess jaws and paired fins
• Placoid scales cover skin
• 2 major groups
• chimaeras or ratfish
• elasmobranchs
• 2 body forms streamlined, e.g., sharks or
  dorsoventrally flattened, e.g., skates and rays)

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Sharks - Elasmobranchs

• Top predators of oceans food webs
• 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 claspersmodified pelvic fins which
  transfer sperm from the male to the female

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Stepped Art
Fig. 10-3, p. 266
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Sharks

• Found in all oceans with the greatest numbers in
  temperate and tropical waters
• Humans exploit shark populations for fins, meat,
  oil, leather, cartilage and sport

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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
• Eyes and spiracles (openings for the passage of
  water) on top of the head
• Gill slits on the ventral side
• Lack anal fin
• Specialized pavement-like teeth are used to crush
  prey (e.g. benthic invertebrates)

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Skates and Rays

• 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
• Fished commercially for food, many are considered
  threatened

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Differences between Skates and Rays
Rays swim by moving fins up and down Skates create a wave from the forward to backward fin edges
streamlined tails with venomous barbs or spines fleshier tails with small fins and no spines
larger size smaller size
Ovoviviparous young born live but no placental connection mostly oviparous egg laying
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Chimaeras

• ratfish, rabbitfish, spookfish
• Large pointed heads and long, slender tails
• Gills covered by operculum water inhaled through
  the nostrils rather than mouth
• Have flat plates for crushing prey instead of
  teeth
• Males have claspers on their heads and pelvic fins

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Chimaeras

• Oviparous produce large eggs in a leathery case
• Generally bottom dwellers
• Little commercial value

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Lobefins

• Coelacanths classified as lobefins due to
  presence of rod-shaped bones surrounded by thick
  muscle in the pelvic and pectoral fins
• Only known as fossils until discovery of living
  specimen in 1938

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Lobefins

• Live in Indian Ocean at depths of 150 to 250
  meters
• Skeleton made of bone and cartilage (vertebral
  column is cartilage)
• Rostral organ in head detects weak electrical
  currents, may aid in prey detection
• Life span is 60 years, reach sexual maturity at
  20 years, produce 5 to 26 live young
• Considered to be in danger of extinction

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Ray-Finned Fishes

• Ray-finned fish are named so because of the rays
  seen in their fins
• Most dominate group of vertebrates in ocean
• homocercal tails tails with dorsal and ventral
  flanges nearly equal in size vertebral column
  usually does not continue into the tail
• scales that are thinner and more flexible less
  cumbersome for active swimmers

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Ray-Finned Fishes

• dorsal fins, caudal fin, and 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

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The Biology of Fishes Body Shape

• Shape of body determined by characteristics of
  habitat
• 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
• complex habitat, e.g., 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 and Patterning

• Countershading is seen in open ocean fish
• obliterative countershadingcoloration in which
  the back (dorsum) is dark colored, and graduates
  on the sides to the bellys pure white
• when viewed from above, dark color blends in with
  surrounding water when viewed from below, white
  belly blends in with lit surface waters
• Disruptive colorationbackground color of the
  body is usually interrupted by vertical lines
  may be a dark dot (eyespot) present in tail
  area
• more difficult for predators to see the fish

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Fish Coloration and Patterning

• 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

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Fish Coloration and Patterning

• Cryptic coloration coloration which blends with
  the environment
• used for camouflage

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Locomotion

• In swimming, the trunk muscles propel the fish
  through the water
• trunk muscles are arranged in a series of muscle
  bands
• muscles contract alternately from one side of the
  body to the other
• contractions originate at the anterior end and
  move toward the tail, flexing the body and
  pushing against the water

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Locomotion

• Fish with different body forms swim in different
  ways
• elongate fish undulate the entire body
• swift swimmers flex only the posterior portion of
  the body
• other fish are somewhere in between
• fish with a dermal skeleton can only flex the
  area before the caudal fin
• some fish swim using their fins alone without
  body flexure

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Buoyancy Regulation

• Maintaining buoyancy
• sharks sink if they stop swimming
• large livers produce squalenean oily material
  with a density less than seawater

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Buoyancy Regulation

• Most fish use a swim bladdera gas-filled 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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The Biology of FishesAdaptations 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
• Parrotfish secrete a mucus cocoon
• Surgeonfish are armed with razor-sharp spines

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Adaptations to Avoid Predation

• Clingfishes use a sucker to attach to rocks so
  predators cant 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

• Three reproductive modes
• Oviparity eggs are shed into the water column
  and embryo develops outside the mothers body
• common in ray-finned fishes
• Ovoviviparity fertilization is internal and
  eggs hatch within mothers uterus, where they are
  nourished by yolk stored in egg
• common in sharks
• Viviparity young attach directly to mothers
  uterine wall or uterus produces uterine milk
  that is absorbed by embryo
• occurs in some sharks and some ray-finned fishes

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The Biology of Fishes Schooling

• School of fish group of individuals that
  operates in a polarized, synchronized fashion
• Reasons for schooling
• more eyes increases food finding abilities and
  predator avoidance
• predators cant focus on an individual