Transcript Ichthyology Fall 2000 - University of North Dakota

Reading Assignment:
Chapter 21: Silversides, Flying fish,
and Killifish
Recap:
1.
2.
3.
4.
Chemoreception
Acustico-lateralis System
Electroreception
Pheromones
end
Lateral Line (cross section) Fig. 10.6
lateral line pores
cupulae
epidermis
lateral line canal
endolymph
end
Lateral Line (cross section) Fig. 10.5
vibrations
nerve impulse to brain
end
lateral line
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
Mormyridae--elephantfishes
Gymnotiformes -- knifefish
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
end
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
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
end
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
end
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
Carangidae--bigeye jack school
end
diagonal banded sweetlips
end
Advantages of Schooling continued:
• increased efficiency in finding food
• increased reproductive success
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
3. Aggressive Behavior
• Territoriality - some defend territories,
generally for a limited resource
–
–
–
–
mates
breeding sites
feeding territories
Ex. Tilapia in thermal gradient
end
Aggressive Behavior continued:
• Aggressive encounters:
–
–
–
–
–
charges
nips
flare fins
lateral displays
submissive behaviors
end
Aggressive Behavior continued:
• Factors affecting aggressive advantage:
– size
– prior residency
– result of previous encounters
• Dominance Hierarchies
– often established in interacting groups
– Advantages/Disadvantages?
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
end
Communication
Pheromones--already covered
1. Visual Signals
2. Auditory Signals
end
1. Visual Signals:
• Color -- important in visual comm.
– pigments:
• carotenoids - reds, yellows (contribute to green)
• melanins - dark red, brown, black
end
Color continued:
– Structural colors: (reflected light)
• purines - reflective (colorless)
– ex: guanine (iridiophores) cells containing
guanine
– iridescence: produced when light waves are
reflected in parallel
end
carotenoids
clown fish
end
carotenoids
Salvelinus fontinalis--brook trout
end
carotenoids
diagonal banded sweetlips
end
melanins
end
melanins
Poeciliidae -- black molly
end
melanins
Etheostoma nigrum - johnny darter
end
guanine
blue marlin
end
guanine
Hiodon alosoides -- goldeye
end
guanine
Dorosoma petenense -- threadfin shad
end
guanine
Sphyraenidae -- barracuda
end
Example of coloration:
Campostoma--stoneroller
end
Example of coloration:
end
Example of coloration:
Etheostoma exile--Iowa darter
end
Example of coloration:
Lepomis cyanellus -- green sunfish