Reading Assignment:

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Reading Assignment

• Chapter 19 Pike, Salmon and Smelt

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Class Projects

• Tip
• divide tasks into two parts
• main ideas, points and concepts
• writing

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Recap

• 1. Chemoreception
• 2. Acustico-lateralis System
• 3. Electroreception
• 4. Pheromones

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1. Chemoreception details

• Olfaction taste --sense chemicals
• Differences
• location of receptors
• olfaction -- special sensory pits
• taste -- surface of mouth, barbels
• sensitivity
• olfaction -- high
• taste -- lower

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Olfaction details

• Sense food, geog. location, pheromones
• structure -- olfactory pit
• incurrent excurrent openings (nares) divided by
  flap of skin
• olfactory rosette -- sensory structure large
  surface area
• water movement driven by
• cilia
• muscular movement of branchial pump
• swimming

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Olfaction details continued

• Sensitivity varies--high in migratory spp.
• Odors perceived when dissolved chem. makes
  contact with olfactory rosette
• anguilid eels detect some chems. in conc. as low
  as 1 x 10-13 M !
• M moles per liter
• salmon detect amino acids from the skin of
  juveniles
• sea lampreys detect bile acids secreted by larvae
• directional in nurse, hammerhead sharks

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Taste details-- short-range chemoreception

• detects food, noxious substances
• sensory cells in mouth and on external surfaces,
  skin, barbels, fins
• particularly sensitive to amino acids, small
  peptides, nucleotides, organic acids

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2. Acoustico-lateralis system

• Detects sound, vibration and water displacement
• Functions in orientation balance
• Organs
• inner ear (no external opening, no middle ear, no
  ear drum)
• lateral line system

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Hearing details

• sound travels farther 4.8 x faster in water
• sound waves cause body of fish to vibrate

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Hearing details continued

• inertia of otoliths resist vibration of fish
• sensory hairs bend, initiating impulse
• nerves conduct impulse to auditory region of brain

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Hearing details continued

• certain sounds cause insufficient vibration
• weak sounds
• high frequency
• distant sounds
• enhancements for sound detection
• swim bladder close to ear
• swim bladder extensions (clupeids, mormyrids)
• Weberian apparatus--ossicles (ostariophysans)

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Structure of Inner Ear

• 3 semicircular canals--fluid-filled tubes w
  sensory cells (hair-like projections)
• 3 ampullae--fluid filled sacs w sensory cells
• 3 sensory sacs containing otoliths
• otoliths--calcareous bones approx. 3x as dense
  as fish

• 1 in Myxini
• 2 in Cephalaspidomorphi

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Fish Inner Ear Fig. 10.2
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Function of inner ear components

• semicircular canals ampullae --
• detect acceleration in 3D
• utriculus otolith --
• gravity and orientation
• sacculus/sagitta lagena/otolith --
• hearing

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Lateral line

• detects water movement
• low frequency vibrations
• specialized for fixed objects and
• other organisms
• Neuromasts -- fundamental sensory structure
• single or part of lateral line system

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Neruomast Fig 10.5
water
increasing pulse rate
decreasing pulse rate
fish
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Lateral Line (cross section) Fig. 10.6
subeipdermal tissue
endolymph
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Lateral Line (cross section) Fig. 10.5
vibrations
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Lateral line details

• often well-developed on head
• system poorly developed in lampreys and
  hagfishes--neuromasts only
• often no lateral line in inactive fishes
• well-developed in blind cave fishes
• functions like a sort of sonar
• exploration -- higher speed swim-by

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3. Electroreception

• detection of weak electrical current
• common in all groups except teleosts
• exceptions--teleosts with electroreception
• mormyrids -- elephantfishes
• Gymnotiformes -- electric knifefishes, elec. eel
  650V
• Malapteruidae -- electric catfishes (450 V)

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Electroreception structures

• Pit organs in teleosts (0.3 mm in depth)

• Ampullae of Lorenzini in marine elasmobranchs
  (5-160 mm in length)
• magnetite crystals in tunas

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Electroreception Function

• detection of geomagnetic lines (earths mag.
  Field)
• detection of signals given off by muscle
• detection of signals produced by conspecifics
• electric organs--produce electric field
• weak -- most
• strong -- electric catfish, electric eel,
  electric ray--stun prey

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electric field
fish
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lesser electric ray
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Pheromones

• Defn Chemicals released onto environment that
  elicit an immediate and specific reaction in
  conspecifics.
• Schreckstoff ostariophysan fright substance
  (pike defecation habits)
• Ovarian pheromone elicits courtship behavior in
  male frillfin gobies
• difficult to study

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Behavior Communication

• 1. Schooling
• 2. Feeding
• 3. Aggressive Behavior
• 4. Dominance Hierarchies
• 5. Resting Behavior

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1. Schooling - moving in close coordinated
association

• 25 of fishes school
• herring schools to 4.5 billion m3
• _at_ density 0.5-1 fish per m3
• 1/7 th vol. of Lake Sakakawea
• consider Lake Sakakawea 30 billion m3
• 200 mi long 185 ft max depth

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Advantages of Schooling

• Reduced risk of predation
• school may appear as large organism
• collective alertness
• predator confusion
• difficulty of selecting target (flock-shooting)
• movement camouflage

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sergeant major
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Advantages of Schooling continued

• Hydrodynamics--energetic efficiency in swimming
• drafting
• snout-cone effect
• similar to V-formation in birds
• 25 birds could get a 70 increase in distance for
  a given energy expenditure

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Hydrodynamics of Schooling
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Sphyreaenidae -- barracuda school
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Carangidae--bigeye jack school
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diagonal banded sweetlips
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Advantages of Schooling continued

• increased efficiency in finding food
• increased reproductive success

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2. Feeding Behavior

• Generalists--wide variety of prey
• omnivores -- catfishes
• Specialists--specific prey
• herbivores -- plant/algae eaters
• planktivores
• piscivores -- fish eaters
• extreme specialists
• scale-eating cichlids
• parrot fishes -- coral
• cookie-cuter sharks

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Scaridae--parrot-fishes
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cookie cutter shark
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cookie cutter shark
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caught at depth of 960 m
goblin shark
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Feeding Behavior continued

• Opportunists -- take advantage of abundant prey
• even if outside normal mode of feeding
• non-surface feeders may feed at surface during
  mayfly hatch
• trout feeding on insect hatches

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Foraging Factors

• prey size versus mouth size
• energetic efficiency--energy spent versus energy
  gained
• prey distance
• ease of capture - speed maneuverability
• handling - spines armor
• ease of digestion - composition scales bone
• energy/nutrient content

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3. Aggressive Behavior

• Territoriality - some defend territories,
  generally for a limited resource
• mates
• breeding sites
• feeding territories
• Ex. Tilapia in thermal gradient

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Aggressive Behavior continued

• Aggressive encounters
• charges
• nips
• flare fins
• lateral displays
• submissive behaviors

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Aggressive Behavior continued

• Factors affecting aggressive advantage
• size
• prior residency
• result of previous encounters
• Dominance Hierarchies
• often established in interacting groups
• Advantages/Disadvantages?

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4. Resting Behavior

• sleeping or inactive
• observed in many species
• day night dusk dawn
• schools become disorganized
• some change color
• some do not react to vision or touch

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