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Oceanic Nekton - PowerPoint

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Oceanic Nekton - PowerPoint Powered By Docstoc
					•Open water column                          •Lacks solid physical structures
•Neritic – pelagic environment above        •No place for attachment, burrowing,
continental shelf                           hiding
•Oceanic – pelagic environment beyond the
                                            •No tidal action
shelf break
                                            •Subject to currents




                                                              •Pelagic – organisms
•Stay afloat                                                  that live on the water
                                                              column, away from the
•Eat                                                          bottom
                                                 •Plankton – drift in water
•Avoid being eaten                                   •
•Movement                                        •Nekton – swim strongly enough to
                                                 move against currrent
                                                     •
Challenges   Adaptations
What are the 8 adaptations of
ocean nekton?
Nekton --- those organisms that have
developed powers of locomotion so that they
are not at the mercy of prevailing ocean
currents or wind-induced water motion.
Major zones of life
   in a marine
    ecosystem
    General characteristics of nekton
    Larger body size
    Greater swimming power
    Vertebrates dominate (fish)
    Invertebrates rare (squid)
    Few reptiles (turtles and sea snakes), birds
     (penguin) and mammals
Vertical Distribution
Holoepipelagic
 Spend entire life in epipelagic
 shark, tuna
 Meroepipelagic
  Spend part of life in epipelagic
  Oceanodromous
     Migrate to shallow waters to spawn
     Herring, dolphin
  Anadromous
     Live in ocean, migrate to freshwater to
      spawn
     Salmon, steelhead
               Getting oxygen
 Apneustic breathing
    several minutes of diving followed by a few
    seconds of breathing
 Extensive elastic tissue in the lungs
    Allows additional O2 uptake
 Collapsing lungs during a deep dive
 Storing O2 in blood
 Bradycardia
    slowing heart beating rate
Deep Divers:
http://www.youtube.com/watch?v=kHk6zJwDoQM
           Staying Bouyant
Gas-filled swim bladder
  Lacking in bottom fish
  In active, continuously swimming fish
    Swim bladder can not adjust fast enough
     to compensate for pressure changes and
     maintain neutral buoyancy.

Fat (blubber) present in those that lack swim
 bladder
  Sharks, mammals
Buoyancy adaptations of nektonic fish and
mammals.
              Reproduction
 Oviparity –fertilized eggs are laid by the
  mother and hatch outside body
    Tuna, marlin; egg case in skates, rays
 Ovoviviparity- young develop from eggs
  inside the mother but separated from it by
  the egg membranes
    thresher and blue shark
 Viviparity - developing embryo obtains its
  nourishment directly from the mother via a
  placenta
   mammals
         Sensory reception
   Chemoreception
   Vision
   Echolocation (sound reception) - sperm
    whale (melon)
   Electroreception - shark (ampullae of
    Lorenzani)
        Defense and camouflage

 Camouflage
    Countershading- darker on dorsal
     surface and lighter on ventral side
    Transparency of the body, mainly for
     plankton or small fish
    Alternation of body shape: develop a
     ventral keel the body to eliminate a
     conspicuous shadow on the belly.
Light beam


 Reflecting light makes fish
 to appear dark from above




   Reflecting light makes
   fish to appear light from
   below
Cryptic coloring on the sides of a Pacific white-sided
porpoise, Lagenorphynchus obliquidens, mimicking the
wave-roughened surface of the water.
Contrasting
color patterns
on various
nekton. (A)
Dall’s
porpoise
(Phocoenoides
dalli). (B)
Manta ray
(Manta ray
(Manta
hamiltoni). (C)
Albacore
(Thunnus
alalunga).
Diagram showing
how a keel on the
ventral surface of an
animal eliminates
the dark shadow
normally cast
downward by an
unkeeled animal.
The presence of the
shadow means that
an animal living
deeper and looking
upward would see
the unkeeled
nektonic animal due
to the shadow, but
would not see the
keeled animal,
which would blend
into the lighted
background.
               Locomotion
Propulsive force
Reduce resistance
 Body shape
    Hydrodynamic mechanism for
     additional buoyancy
  Fins
   Aspect ratio = (fin height)/fin area
      High ratio fish are capable of long-
        distance, continuous swimming
A – truncate
          most common
B – heterocercal
          sharks
C – lunate
          tuna, marlin
Three views of a tuna showing the adaptations
necessary for fast movement. (A) Front view. (B)
Side view. (C) Top view.
Some
characteristic
meroepipelagic
fishes. (A)
Ribbon
halfbeak,
Euleptorhamph
us viridis. (B)
Herring, Clupea
harengus, (C)
Whale shark,
Rhincodon
typus. (D)
Dolphin,
Coryphaena
hippurus. (E)
Salmon,
Oncorhynchus
keta.
Fast-swimming fishes with the characteristic lunate-
shaped tail and narrow caudal peduncle. (A) Tuna
(Thunnus thynnus). (B) Sailfish (Istiophorus platypterus).
Speed
  killer whale --- 40-50 km/hr
  barracuda --- 40 m/hr .
  yellow fin tuna 74.6 km/hr for 1.9 second
Schooling
  Protection
  Drag-reducing behavior creating
   turbulence
  Ensure high proportion of egg fertilization


          http://www.youtube.com/watch?v=EeMPLdco6
          C8&feature=channel
              Migration
Purposes of migration
 Reproduction or feeding
 Often exhibit a strong similarity to patterns
   of ocean surface currents
Orientation
 Biological clock operating on longer period
   rhythms
 Day length, water temperature, food
   availability, earth's magnetic field
 Keen sense of smell -- salmon for home
   stream
Definition:                          How?
                                     Radio tracking
To attach tracking device to
animal that relays its
location and migration               Satellite tracking
information back to satellites
and computers.
                              Satellite
Why?                          Tracking         Who?
Where and why animals migrate              Any migratory or ocean
                                           nekton animal
Species moving to new locations
       food density
       a change in water temp
       ability to adapt to changes

				
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