Transcript Ichthyology Fall 2000

Reading Assignment:
Chapter 19: Pike, Salmon and Smelt
end
Class Projects:
Tip:
divide tasks into two parts
1. main ideas, points and concepts
2. writing
Recap:
1.
2.
3.
4.
Chemoreception
Acustico-lateralis System
Electroreception
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
end
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
sensory structure of ear
sensory hairs
otolith
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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)
end
Gnathostomata
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
semicircular canal
ampullae
lagena
otolith
utriculus
sacculus
otolith
otolith (sagitta)
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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
end
end
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
end
Neruomast: Fig 10.5
cupula
water
decreasing pulse rate
increasing pulse rate
epidermis
fish
sensory cells
background pulse rate
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Lateral Line (cross section) Fig. 10.6
lateral line pores
cupulae
epidermis
lateral line canal
endolymph
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Lateral Line (cross section) Fig. 10.5
vibrations
nerve impulse to brain
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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”
end
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)
end
Malapteridae
-- electric
catfish
Gymnotiformes
-- electric
eel
Gymnotiformes -- knifefish
Mormyridae -- elephantfishes
end
Electroreception structures:
• Pit organs in teleosts (0.3 mm in depth)
• Ampullae of Lorenzini in
marine elasmobranchs (5160 mm in length)
• magnetite crystals in tunas
pit
gel
nerve
sensory
cells
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Electroreception Function:
• detection of geomagnetic lines (earth’s 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
end
distorted electric field
current
voltage
end
electric field
non-conducting object
-10 mV
fish
+10 mV
end
lesser electric ray
end
end
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
end
end
Behavior & Communication:
1.
2.
3.
4.
5.
Schooling
Feeding
Aggressive Behavior
Dominance Hierarchies
Resting Behavior
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1. Schooling - moving in close
coordinated association
• 25% of fishes school
– herring schools to 4.5 billion m3
• @ 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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end
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
end
sergeant major
end
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
end
Hydrodynamics of Schooling
thrust
turbulence
streamlines
end
Sphyreaenidae -- barracuda school
end
Carangidae--bigeye jack school
end
diagonal banded sweetlips
end
Advantages of Schooling continued:
• increased efficiency in finding food
• increased reproductive success
end
end
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
end
Scaridae--parrot-fishes
end
cookie cutter shark
end
cookie cutter shark
end
caught at depth of 960 m
goblin shark
end
end
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
end
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
end
end
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?
end
end
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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