Reading Assignment:

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Reading Assignment
Chapter 21 Silversides, Flying fish, and
Killifish
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Recap

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

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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
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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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Mormyridae--elephantfishes
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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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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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Communication

• Pheromones--already covered
• 1. Visual Signals
• 2. Auditory Signals

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1. Visual Signals

• Color -- important in visual comm.
• pigments
• carotenoids - reds, yellows (contribute to green)
• melanins - dark red, brown, black

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Color continued

• Structural colors (reflected light)
• purines - reflective (colorless)
• ex guanine (iridiophores) cells containing
  guanine
• iridescence produced when light waves are
  reflected in parallel

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carotenoids
clown fish
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carotenoids
Salvelinus fontinalis--brook trout
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carotenoids
diagonal banded sweetlips
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melanins
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Poeciliidae -- black molly
melanins
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Etheostoma nigrum - johnny darter
melanins
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guanine
blue marlin
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guanine
Hiodon alosoides -- goldeye
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guanine
Dorosoma petenense -- threadfin shad
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guanine
Sphyraenidae -- barracuda
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Example of coloration
Campostoma--stoneroller
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Example of coloration
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Example of coloration
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Example of coloration
Lepomis cyanellus -- green sunfish