Reading Assignment: Chapter 19: Pike, Salmon and Smelt end

Class Projects: Tip: divide tasks into two parts main ideas, points and concepts writing

Recap: 1. Chemoreception 2. Acustico-lateralis System 3. Electroreception 4. Pheromones end

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 end

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 end

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 end

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 end

sensory structure of ear Hearing details: sound travels farther & 4.8 x faster in water sound waves cause body of fish to vibrate sensory structure of ear otolith sensory hairs end

Hearing details continued: inertia of otoliths resist vibration of fish sensory hairs bend, initiating impulse nerves conduct impulse to auditory region of brain end

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

Structure of Inner Ear: Gnathostomata 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 end

Fish Inner Ear: Fig. 10.2 semicircular canal ampullae lagena otolith utriculus otolith sacculus otolith (sagitta) end

Function of inner ear components: semicircular canals & ampullae -- detect acceleration in 3D utriculus & otolith -- gravity and orientation sacculus/sagitta & lagena/otolith -- hearing end

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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 end

Neruomast: Fig 10.5 cupula water epidermis sensory cells fish decreasing pulse rate increasing pulse rate epidermis sensory cells fish background pulse rate end

Lateral Line (cross section) Fig. 10.6 cupulae lateral line pores epidermis lateral line canal subeipdermal tissue endolymph end

Lateral Line (cross section) Fig. 10.5 vibrations nerve impulse to brain end

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

Gymnotiformes -- electric eel Malapteridae -- electric catfish Mormyridae -- elephantfishes Gymnotiformes -- knifefish end

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 pit sensory cells gel nerve 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 current voltage end

non-conducting object electric field non-conducting object -10 mV fish +10 mV end

lesser electric ray end

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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 Pike deficate in certain areas, perhaps to minimize the potential for cyprinids to detect them from previous cyprind meals. end

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Behavior & Communication: 1. Schooling 2. Feeding 3. Aggressive Behavior 4. Dominance Hierarchies 5. 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

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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 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

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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 end

Scaridae--parrot-fishes end

cookie cutter shark end

cookie cutter shark end

caught at depth of 960 m goblin shark end

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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 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

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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 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

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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 end