Overview  Make Strong Fields for hunting (rare)  Make Weak fields for other uses (more common)  Don’t make electrical fields, but sense them (very common).  Make Strong Fields for hunting (rare)  Make Weak fields for other uses (more common)  Don’t make electrical fields, but sense them (very common).

Electricity for Hunting

Strongly Electric Fish Electricity made using muscles or nerves

Torpedo Ray

Electro- plaques

Tells how many electrons are moving through the circuit. Tells how hard the electrons are being pushed.

12 V, 1 amp 24 V 4 X 12 = 48 V, 1 amp

1 Amp, 12 V 4 Amps, 12 V

Batteries 12 V and 1 Amp 36 V 4 Amp

Torpedo Ray Bottom Side!

Electro- plaques

Torpedo Ray Stacking For Volts ; Multiple stacks for Amps

Electric Eel

6.000 electroplaques 500 volts and 1 amp = 500 watts

Overview  Make Strong Fields for hunting (rare)  Make Weak fields for other uses (more common)  Don’t make electrical fields, but sense them (very common).  Make Strong Fields for hunting (rare)  Make Weak fields for other uses (more common)  Don’t make electrical fields, but sense them (very common).

Fish that make Weak Fields

Active Electricity for Locating prey Avoiding predators Navigation Communication Active Electricity for Locating prey Avoiding predators Navigation Communication

Weakly Electric Fish

Mormyrids

14 Percent of all fish species = Mormyrids

Red OctoberNimitz “Ping” Sound waves sent out by the Red October bounce off the Nimitz and back to the Red October. Sonar operators on the Red October hear the reflected sound and know that the Nimitz is there. Active Sonar

“gotcha” Active Electrical Senses An electrical field sent out by special organs in the Red Fish is distorted by the other fish. Electrical field detectors on the Red Fish detect the distortion and know that the other fish is there. Finds prey and predators.

Active Electricity for Locating prey Avoiding predators Navigation Communication Active Electricity for Locating prey Avoiding predators Navigation Communication

Active Electrical Senses Rock

Why to Electric Eels and Mormyrids have such weird fins?

The elephant fish sets up a nice symmetrical electrical field using it’s electrical organ. When anything enters the field, the field is distorted and the fish can sense the change.

Active Electricity for Locating prey Avoiding predators Navigation Communication Active Electricity for Locating prey Avoiding predators Navigation Communication

Electricity for Communication

Overview  Make Strong Fields for hunting (rare)  Make Weak fields for other uses (more common)  Don’t make electrical fields, but sense them (very common).  Make Strong Fields for hunting (rare)  Make Weak fields for other uses (more common)  Don’t make electrical fields, but sense them (very common).

Passive Electricity for Locating prey Avoiding predators Navigation Communication Passive Electricity for Locating prey Avoiding predators Navigation Communication

All animals make a weak electrical field

Red October Nimitz Sound from the engines and propeller of the Nimitz are detected by sonar operators on the Red October. When they hear the sound they know the Nimitz is there. Passive Sonar

An electrical field produced by normal muscle and nerve activity in the green fish is detected by electrical sensors on the Red Fish. Passive Electrical Senses

Hammerheads and Stingrays

Fish That Sense Electricity: It isn’t just for exotic species

Dermis Epidermis Ampullary Organ for sensing electrical fields

Sharks

Moving a wire through a magnetic field produces an electrical current

Sensors on Sharks = Opening of Ampullae = Lateral Line = Canal between Ampullae Canals are full of Conductive jelly!

Shark Navigation

Electricity Highlights Some fish use muscle and nerves to make strong fields for killing prey Some fish just sense electrical fields –Passive electrical senses – detects other animals for hunting or escape Other fish make weak fields for navigation or communication Communication: Mormyrids zap messages to each other and receive them Navigation –Active electrical senses: zap out a field and look for interference Sensors in bony fish = ampullary organs Sensors in sharks = conductive canals, Ampullae of Lorenzini

The Lateral Line

Ampula Cupola Lateral Line Canal Cupola Hair Cells Canal to skin surface Crista in Ear Neuromast in Lateral Line

Ampula Cupola Lateral Line Canal Cupola Hair Cells Canal to skin surface Crista in Ear Neuromast in Lateral Line

Water Movement Neuromasts Muscle Dermis Epidermis Pore

Muscle Dermis Epidermis Pore Scale Water Water Movement

Free Neuromasts Super Sensitive No “Filter”

= Lateral Line Pores = Exposed Neuromasts

Tilapia: The lateral line is interrupted to avoid the fin

Flounder: The lateral line goes around the fin.

Placements avoid fins, but also reveal the purpose of the Lateral Line

Schooling

Protection

Flying Fish: The lateral line is on the bottom of the fish so that it can sense what is beneath.

Prey Detection

Frogfish

Frog Fish: The lateral line goes along the top of the fish so that it can sense what is above.

Killifish

The struggling bug makes ripples that the killifish detects with free neuromasts

Antarctic Pagothenia

Lateral line specially tuned to shrimp vibrations

Navigation

Blind Cavefish

Lateral Line Highlights Detects movements in the water Canal connected to surface by pores Movement of water detected my neuromasts Neuromasts look like cristae (ears) Neuromasts may be exposed, but they are extremely sensitive: not for rough water Lateral line and neuromasts are positioned depending on the needs of the fish Lots of uses: Schooling, prey detection, predator avoidance, navigation

Semicircular Canals Third canal (horizontal) not visible Ampullae Fish Ear

Right side Up Fish Otolith Upside Down Fish Otolith bending hairs on hair cells Hairs on hair cells straight

Focusing in Mammals Lens shape changes Side Views Front View Near Far

Focusing in Fish Muscle pulls on lens

Daytime Cones in front Rods Shaded Light

Night Rods in Front No Shading Cones in Back Light

Smell vs. Taste? Nose Sensors in the Olfactory Epithelium Many uses, including food location Nose Sensors in the Olfactory Epithelium Many uses, including food location Mouth, & many places Taste buds SCC Primarily for feeding Mouth, & many places Taste buds SCC Primarily for feeding

Olfactory Epithelium Ciliated Cells Molecules Whooshing by in the Water Nerves to the brain

Amino acids: The building blocks of protein. Some amino acids are more stimulatory than others. Steroids: Some fish are highly sensitive to hormones especially those related to reproductive activities (see below). –Prostaglandins: Released by female fish upon ovulation.

What Can They Taste ? sweet, sour, bitter, salty, uma Amino acids Steroids: Sex hormones Organic acids and nucleotides: Carbon Dioxide: ?? Peptide toxins: Like marine puffer toxin

Solitary Chemoreceptor Cells: SCC Dispersed on external surface of fish as well as on gills and in the oral cavity. These cells are sensitive to amino acids in some species but not others. They are especially adept at detecting fish mucus and some organic acids.

Eggs: found in a redd Alevin: fry with yolk Parr: Fingerlings in fresh water, black bars Smolt: Fingerling ready for the sea, silver Adult: In the sea

Does not die, returns to the sea

Homing Theories Imprinting: Salmon smell the stream Pheromone: Salmon smell their kin Which is right?

“zap” Active Electrical Senses An electrical field sent out by special organs in the Red Fish is distorted by the other fish. Electrical field detectors on the Red Fish detect the distortion and know that the other fish is there.

An electrical field produced by normal muscle and nerve activity in the green fish is detected by electrical sensors on the Red Fish. Passive Electrical Senses

Sensors on Sharks = Opening of Ampullae = Lateral Line = Canal between Ampullae Canals are full of Conductive jelly!