BIOLOGY 457/657 PHYSIOLOGY OF MARINE

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BIOLOGY 457/657PHYSIOLOGY OF MARINE ESTUARINE
ANIMALS

• May 5, 2004
• MIGRATION
• IN THE SEA

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INTRODUCTIONCues for Migration

• Marine Animals Use Every Available Sensory
  Modality to Orient Their Migrations, Both Short
  and Long-Distance

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INTRODUCTIONCues for Orientation

• Light (visual systems eyes)
• Sound (auditory senses)
• Gravity (mechanical systems)
• Pressure (several receptor types)
• Chemical gradients (chemosenses)
• Currents (mechanoreception)
• Wind (mechanoreception)
• Wave surge (acceration receptors gravity sense)
• Temperature (thermal sense)
• Celestial cues (visual systems)
• Electrical fields (electroreception)
• Magnetic fields (magnetoreceptors)
• Landmarks (visual systems)

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INTRODUCTIONTypes of Navigation

• Piloting - Navigation involving the use of
  landmarks.
• Dead Reckoning - Navigation involving
  compass and distance cues.
• True Navigation - Navigation requiring a
  reliable map sense requires 2 independent
  sets of coordinates.
• As animals migrate, they often combine all
  possible strategies during their travels. For
  instance, they may use true navigation to figure
  out where they are, dead reckoning to get near
  their destination, and piloting to reach the
  exact point they want to go. In fact, this is
  what a human navigator often does!

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INTRODUCTIONTypes of Migration
Definition The act of moving from one spatial
unit to another (Robin Baker, 1978). Accidental
Migration vs Non-accidental Migration Removal
Migration vs Return Migration Periodic
Migration vs Ontogenetic Migration Homing
Behavior
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INTRODUCTIONBiological Features of Migration
Is species characteristic. Generally involves a
large fraction (frequently all) of the
individuals in a population. Is multimodal.
Involves the use of diverse cues for orientation
and navigation. Is periodic. Periodicity may
be ontogenetic, annual, lunar or semilunar,
diel, or tidal. Has physiological aspects.
Includes sensory, internal drive, and
orientational/navigational components.
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Migrations in the SeaShort-Range Migrations
Diel Vertical Migration

• Common patterns
• Nocturnal (animals at surface at night, by far
  the most common pattern)
• Twilight (animals at surface at dawn and dusk a
  modification of the nocturnal pattern)
• Reverse (animals at surface during the day)
• Tidal (keyed to to tides phase shifts with
  regard to LD cycle)
• Substrate-Water Column (common for animals that
  are riding tidal currents or only feeding for
  part of the day)
• Patterns may vary with age, sex, season, mating
  condition, and presence of food or predators.
• Diel vertical migration is considered the
  greatest mass movement of animals on earth that
  takes place each day!

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Diel Vertical Migration

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Vertical Migration Mechanisms

• Light plays a central role in all but tidal
  vertical migration.
• Does not involve phototaxis (an oriented swimming
  response to light).
• Light orientation may be modified by other
  depth-related factors.
• Two Major Hypotheses
• (1) Preferendum Hypothesis - the animals
  follow a preferred level of light (a particular
  isolume).
• (2) Rate-of-Change Hypothesis - the migration
  is stimulated by changing light conditions. For
  instance, a decrease in light intensity might cue
  upward swimming, while an increase could initiate
  downward swimming.

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Vertical Migration Mechanisms

• Isolume-following by the deep scattering layer
  at sunrise (left) and sunset (right). Notice
  that the layer seems to stay with a particular
  level of light. But also notice that this
  apparent following behavior could be caused by
  changes in light intensity.

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Vertical Migration Mechanisms

• Isolume-following by crab larvae in an estuary.
  Note that while the larvae often stay with a
  particular isolume, they also migrate in response
  to other (less obvious) cues.

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Vertical Migration Mechanisms

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Vertical MigrationAdaptive Significance

• Optimal light value - old idea, but what does
  it mean???
• Photoprotection
• Accidental byproduct of station-keeping.
• Enhancement of dispersal by currents at different
  levels.
• Predator avoidance ()
• Metabolic advantages (feed in warm water, digest
  and assimilate in cold)
• Feeding advantages (chlorophyll and
  photosynthetic products are highest at sunset)

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Migrations in the SeaShort-Range Migrations
Y-Axis Orientation

• Animals on beaches commonly orient towards the
  water. This is called y-axis orientation,
  since it is perpendicular to the beach. There is
  evidence that the preferred orientation (with
  respect to the sun) is inherited, at least in
  beach amphipods.

www.gla.ac.uk/ibls/DEEB/honsproj/
izzie_2/graphics/tal.jpg
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Migrations in the SeaIntermediate-Range
Migrations

• Example The spiny lobster Panulirus argus in
  the Bahamas (research done by William Herrnkind
  and collaborators)
• The migration is
• unusual in that
• the lobsters
• actually travel
• in single-file
• queues.
• Queuing
• reduces drag.

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Migrations in the SeaIntermediate-Range
Migrations

stevegoldfarb.com/bvi/ art/spinylobster.gif
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Migrations in the SeaIntermediate-Range
Migrations

• Summary of migration
• Premigration. Lobsters move independently.
• Buildup. In autumn, lobsters move into the
  migration pathway.
• Mass migration. Lobsters begin to form long
  cues, moving southward along the margins of the
  island.
• Post-migration. Following the migration,
  lobsters disperse into available cover. The
  migration may prepare the animals for cold water
  conditions in winter.
• (Summarized from Herrnkind)

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Migrations in the SeaIntermediate-Range
Migrations
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Migrations in the SeaIntermediate-to-Long Range
Migrations

• Spiny lobsters also can orient back to their
  homes if displaced by several 10s to 100s of
  miles.
• Boles Lohmann 2003

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Migrations in the SeaIntermediate-to-Long Range
Migrations

• The navigation system is based on detection and
  orientation within the earths magnetic field.

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Migrations in the SeaLong-Range Migrations I
Tunas

• Bluefin tuna (Thunnus thynnus) make long-distance
  (trans-oceanic) migrations. To study this, tuna
  were tagged with implantable archival tags
  (recovered at the triangles) and pop-up
  satellite archival tags (recovered at the
  circles). These tags monitored location, depth,
  and temperature.

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Migrations in the SeaLong-Range Migrations I
Tunas

• Individual tuna swam vertically down as much as
  1000 m, but often less deep at night (see the
  blue trace, right). Body temperature (red) was
  relatively constant and almost always higher than
  sea temperature outside the fish (black lines
  the red dots are maximum body temperature, and
  the black dots are minimum environmental
  temperature).

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Migrations in the SeaLong-Range Migrations I
Tunas

• Fish often stayed resident in the western
  Atlantic, and many made transoceanic return
  migrations at least once. Panel A shows data
  from 19 fish that migrated only slightly. The
  fish in panel B migrated to the Gulf of Mexico
  and back. C shows several fish that crossed the
  ocean and returned. The bottom panel (D)
  illustrates a fish that stayed near North America
  in 1999 (black) and then crossed to the east
  (where it was caught).

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Migrations in the SeaLong-Range Migrations
II Eels

• Fish migrations between sea rivers fall into
  two general types
• Catadromous migrations. Adults live in fresh
  water, but breed in the open sea. The best
  examples are the anguillid eels, which live in
  rivers (in Europe or Asia) as adults, but breed
  in the sea (in the case of the Atlantic
  population, Anguilla anguilla, in the Sargasso
  Sea).
• Anadromous migrations. Adults live in seawater,
  but spawn in fresh (or estuarine) waters.
  Excellent examples are salmon, lampreys, and
  striped bass (rockfish).
• Navigational mechanisms are unknown, but it is
  clear that chemical cues play major roles.
  Almost certainly, geomagnetic senses are involved
  too.

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Migrations in the SeaLong-Range Migrations
II Eels
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Migrations in the SeaLong-Range Migrations
II Eels

• The Japanese counterpart of Anguilla anguilla (A.
  japonica) was also known to exhibit a catadromous
  migration, but it was only in 1991 that the
  location of the reproductive center was located
  in the Philippine Sea.
• Boles Lohmann 2003

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Migrations in the SeaLong-Range Migrations
III Whales
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Migrations in the SeaLong-Range Migrations
III Whales

• In sperm whales (Physeter catodon), only the
  males carry out the long-distance migrations.
  Females and juveniles remain in temperate or
  tropical latitudes all year long.

homepage1.nifty.com/surara/ pbooks/kujira/sperm.jp
g
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Migrations in the SeaLong-Range Migrations
III Whales

• In humpbacks (Megaptera novaeangeliae), both
  sexes carry out the long-distance migrations.
  Because the northern and southern hemispheres
  have different seasons, the two hemispheres have
  populations that are mostly reproductively
  isolated.

home.earthlink.net/jimmrc/whale/
whalenews0102/w18.html
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Migrations in the SeaLong-Range Migrations
III Whales

• In gray whales (Eschrichtius gibbosus), the
  migration occurs along the coastline from Alaska
  to Baja California, generally within sight of
  land. The animals spy-hop during the
  migration, perhaps to spot landmarks along the
  way.

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Migrations in the SeaLong-Range Migrations
IV Sea Turtles

• Sea turtles (like the green turtle, Chelonia
  mydas, illustrated here) often nest on tiny,
  isolated islands (here, Ascension Island) or
  single beaches (photo, Heron Island, Great
  Barrier Reef). How do the adults find their way
  back to the beach? How do the nestlings make
  their way to the sea and eventually return home?

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Migrations in the SeaLong-Range Migrations
IV Sea Turtles

• Emerging hatchlings (1) find their way to the
  water using visual cues (the location of a
  bright, open horizon), (2) continue offshore by
  swimming into approaching waves, and (3)
  eventually orient in the open ocean using
  geomagnetic cues.

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Migrations in the SeaLong-Range Migrations
IV Sea Turtles1. Visual Cues

• The initial orienting cue is the sight of an
  open, typically bright horizon. Hatchlings will
  orient to a darker horizon if the bright one is
  elevated (as would occur on a moonlit night).
  However, in cases where the horizon is roughly
  equally flat in all directions, they run towards
  the brightest part. This is why artificial
  lighting is so destructive to sea turtles.

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Migrations in the SeaLong-Range Migrations
IV Sea Turtles2. Wave Orientation

• Once the hatchlings reach the water, they orient
  by swimming into waves. Since most waves refract
  when they approach beaches so that they approach
  roughly perpendicular to the shore, wave travel
  direction is usually a reliable cue for the
  direction offshore when near shore.

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Migrations in the SeaLong-Range Migrations
IV Sea Turtles3. Magnetic Orientation

• The final orienting cue is the earths
  geomagnetic field. Turtles have an internal
  map sense they know what direction to swim
  from their current location to get to a given
  destination. The strength and direction of the
  earths field is used for this orientation.

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Migrations in the SeaLong-Range Migrations
IV Sea Turtles3. Magnetic Orientation

• This figure illustrates the 2 components just
  mentioned (field strength and field direction)
  that together produce a map in the north
  Atlantic Ocean that provides a unique
  identification for each location.
• Turtles probably dont know where they are in
  the sense that a human navigator would, but they
  know which way to swim to get to their
  destination.

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