Planktivory

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Planktivory
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Planktivory
Suspension feeders Animals that process large
quantities of water through a feeding apparatus
(gill rakers, baleen). Gill rakers trap
particles such as zooplankton, phytoplankton and
detritus.
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(No Transcript)
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Includes manta rays, basking shark, whale shark,
megamouth, paddlefish, gizzard shad, menhaden,
and bighead carp.  
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• Feeding strategies
•  A)   Obligate and faculative planktivores
• Most fish are planktivorous at some point in
  their life, either as holoplankton or
  meroplankton.
• Facultative planktivores (ex. sunfishes) are
  opportunistic feeders. Prey selection depends on
  food availability
• Obligate planktivores (ex. blueblack herring,
  Atlantic Menhaden) feed exclusively on plankton  

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• B) Ram feeding and suction feeding
• Ram feeding creates a forward motion in which
  water is delivered into the mouth opens mouth
  wide as possible and rams prey
• continuous ram feeders
• intermittent ram feeders
• Suction feeding predator remains relatively
  stationary, comes close to prey and then sucks
  prey in.
• continuous suction feeders
• intermittent suction feeders

Suction feeder
Nonsuction feeder
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Jaw Protrusion
Sling-jaw wrasse
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• Ram Feeders
• Continuous
• Intermittent

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Continuous ram feeders (tow-net)- water passes
continuously through mouth, over gills and exits
through gill slits or operculum. 20 species
fish In fish extensive elaboration of the
branchial (gill) apparatus
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• Manta Ray
• They have no teeth.
• Cephalic flaps channel water containing plankton
  into mouth
• To prevent gills from clogging, a screen of small
  tiny protuberances located in the throat, hold
  the food until it can be swallowed.

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Megamouth, Basking Shark and Whale Shark-
Generally these planktivorous sharks have tiny
numerous teeth and elongated gill rakers. The
gill rakers help to strain plankton.
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• Basking shark- (10 meters long)
• Swims about 2 knots with mouth open and
  bristle-like gill rakers erect while filtering
  particulate matter
• It then closes its mouth forcing water over the
  gills it is an indiscriminate planktivore
• Has five pairs of gill slits and can filters 540
  liters zooplankton/day and over 1500 gallons of
  water/ hour (1850 m3 water/hour)
• Basking sharks caught between Oct. And Dec., no
  visible gill rakers were found, but had immature
  or functionless, incompletely developed rakers
  (possibly has a resting, non feeding stage).
  Re-grows gill rakers by February.

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• Paddlefish- Order Acipenseriformes
• freshwater, rarely brackish found in China and
  the US
• gill rakers are long and in the hundreds- used
  for plankton feeding, minute teeth are present
• Polyodon spathula (US- Mississippi drainage)-
  plankton-feeding non protrusible mouth
• Psephurus gladius (China- Yangtze River)-
  piscivorous with a protrusible mouth

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Continuous ram feeding
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• Intermittent ram feeders
• takes one gulp of water at a time, extracts
  particles and repeats the process
• In using this method, the predator needs to be
  able to grab prey before it moves out of the way.
• Seen in whales, not sure about in fish????

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• Suction Feeders
• Continuous
• Intermittent

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• Continuous suction feeders (pump filter feeders)-
  creates and osculatory pump and draws water in
  over sieving device. Animal remains still while
  suctioning.
• Ammocetes (lamprey larvae)-spends 3-7 years
  filter feeding and burrows into sand
• Feeding
• a current of water is drawn in by muscular
  action
• water enters buccal cavity and washes over gills
• uses gills to filter particles for food
• in ammocetes, filtering linked to breathing.

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• Intermittent suction feeders (intermediate
  feeding)
• relatively unspecialized
• intermediate condition between ram and suction
  feeding on individual prey
• they dont alter their swimming speed or
  direction to focus attention on individual
  plankton.  

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Diurnal and Nocturnal Planktivores
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Diurnal Planktivores

• Typically feed by forming aggregations in the
  water column
• prey- swimming crustacea, larvaceans and fish
  eggs
• largely transparent except for some pigments on
  eyes or gut and usually small size (lt 3mm in
  size)
• Planktivore
• find modifications to jaw, head and dentition
  usually small mouth, reduced or absent
  teeth
• jaw protrusion mainly functions to produce
  suction
• In Chromis viridis- uses ram-jaw, low suction to
  capture evasive prey, but decrease jaw protrusion
  and increase suction when prey are less evasive

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Diurnal Planktivory
adaptations - streamlining and deeply forked
caudal fins aggregation ecology-feed along the
reef edge mainly on transient zooplankton from
open water the fish depend on water currents to
supply them with food may feed in stationary
aggregations
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Crepuscular changeover- diurnal fish leave
typically in order of small fish first.mid
sized . then large Very active time. In
nocturnal species- fish enter waters above the
reef at night fall by size order (small to larger)
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Nocturnal Planktivores

• Difficulty in visually locating prey in dim light
• adaptation- large eyes ex. squirrel fish
• Feed on larger zooplankton Hobson Chess found
  that even the smallest nocturnal reef
  planktivores are limited to zooplankters larger
  than 1 mm whereas diurnal planktivores with
  similar feeding structures have been found to
  feed primarily on organisms smaller than 1 mm.
• Possibly due to
• 1.)   inability to see smaller ones
• 2.)   more efficient
• 3.)   prey more vulnerable

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• Adaptations to nocturnal threats from predators
• streamlined bodies and deeply forked tails are
  less developed- possibly due to less threat to
  attack after dark
• less aggregation occurs at night
• countershading using luminescent organs
• Nocturnal planktivores more widespread throughout
  reef than diurnal counterparts

ctenophore