Bioluminescence and Electric Organs

Exam 3

Electric Organs

• Exapted Muscle Electrocytes

• Exapted Nerve Electrocytes

Exapted Muscle Electrocytes

• this group of fish has developed electric organs from modified muscles

• electric eel, torpedo ray, stargazer

Exapted Nerve Electrocytes

• This group of fish had electric organ is derived from modified spinal nerves

• Ghost Knife Fish → Apterontidae

Electrocyte Function

• Non-contractile muscle (or nerve) has developed greater control over ion gradients (Na/K) in/out of the cell

• These flat cells generate a real, but small, electrical differential

• By stacking these cells in series, called electropaxes, the per-cell-charge (0.15V) can be amplified significantly

• Electrophorus Eels can generate 600-800 volts

Muscle-Based

Volts

are the differential in electrical potential

Amperage (Amps)

is the volume of electrons moving across that difference

You would expect the fish capable of the highest electrical shocks to live in:

Freshwater

‘Shocker’ type fish use

• the electrocytes for prey capture or defense

• Includes stargazers, electric eel/ray/catfish

‘Sensor’ type fish use

• the electrocytes for navigation or communication

• Includes elephant fish, knifefish, and electric skates

TENS unit

a small, battery-powered device that uses low-voltage electrical currents to provide non-invasive, drug-free pain relief

Independently Shocking

Best evidence shows at least 6 different independent lineages of electric generating clades

Bioluminescent Strategies

• Bacteriogenic

• Autogenic

Bacteriogenic

Symbiosis with glowing bacteria

• Pinecone Fish

• Anglerfish

Autogenic

Created by vertebrate internal physiology

• Midshipmen

• Stoplight Loosejaw

• Kitefin Shark

Photopores in Bacteriogenic

• A bacteria, generally Photobacterium or Vibrio species, is housed inside a light generating structure

• Often backed by a layer of Guanine crystals to reflect the light out

Luciferin

• All autogenic bioluminescent verts use luciferin and luciferase to glow

• This enzyme system releases photons when digested

While they all use luciferin, not all bioluminescent fish have the genes to create luciferin themselves

through their diet

But Why do some organisms use bioluminescent?

• Warning – Do not Eat

• Mimicry

• Hunting

• Communication

• Defense

• Counter-Illumination

Red Vs Blue

• Blue-green light is the only wavelength that penetrates to the deep ocean

• If you generate red light, most of your neighbors won’t have any receptors in their eyes to see it

If you actually want others to see your light,

you stick in the blue-green wavelengths

Counter-Illumination

• From the top, I want to look dark

• From the bottom, I want to look light

Platypus, and many other birds/mammals/etc., will…

glow when exposed to UV light

• This is biofluorescence not bioluminescence because the light is being generated exogenously