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