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

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

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

Lateral Line (cross section) Fig 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

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

Electroreception structures: Pit organs in teleosts (0.3 mm in depth) pit nerve gel Ampullae of Lorenzini in marine elasmobranchs ( mm in length) magnetite crystals in tunas 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

voltage distorted electric field end

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

lesser electric ray 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

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 m density fish per m 3 1/7 th vol. of Lake Sakakawea –consider: Lake Sakakawea 30 billion m mi long; 185 ft max depth 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 streamlines turbulence 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

goblin shark caught at depth of 960 m 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

Salvelinus fontinalis--brook trout carotenoids end

carotenoids diagonal banded sweetlips end

melanins end

Poeciliidae -- black mollymelanins end

Etheostoma nigrum - johnny dartermelanins 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

Etheostoma exile--Iowa darter Example of coloration: end

Lepomis cyanellus -- green sunfish Example of coloration: