Lesser electric ray

Gulf Specimen's Research Agendas to Date:

Classical model for neurotransmitter research
Ray distribution in time and space: 12 months of trawl sampling at 4 offshore stations and 1 beach station: West Pass, Cape San Blas and Alligator Point
Sex ratio, size-frequency distribution, reproductive cycle
Movements of tagged animals
Maintenance in captivity: food supply, substrate, barriers, temperature limits
Behavior and electrobiology: ethology, electric recording, exogenous magnetite

GSML Publications on electric rays
Rudloe, A. 1989. Captive maintenance of the lesser electric ray, Narcine brasiliensis, with observations of feeding behavior. Prog. Fish Culturalist 51: 37-41.

Rudloe, A.1989 Habitat preferences, movement, size frequency patterns and reproductive seasonality of the lesser electric ray, Narcine brasiliensis. Northeast Gulf Science 10:103-112.

See Chapter 5.NIGHT OF THE ELECTRIC RAY and Chapter 6. TIDE OF THE PLUMMED WORM
from The Wilderness Coast by Jack Rudloe

Burried Electric Ray

Note eyes emerging from sand on right.

Electric Rays pull sand grains through their endolymphatic ducts located behind their eyes down into their sacculus, or inner ear, which is embedded in their skull.


Dissected electric ray, Narcine brasiliensis, with sacculus exposed showing black sand and orange brain stem. White, pulpy tissue on right is the electric organ.	CAT Scan of sacculus filled with sand. The illuminated bright spots show mineral sand.

	Below: The electric ray concentrates quartz, magnetite, and zirecons in its sacculus, or inner ear.

Ruptured sacculus showing aggregated quartz, magnetite and other heavy mineral grains.

Electric rays burrow in Florida Panhandle subtidal beach sand composed of 99% quartz grains (right) and 1% heavy minerals. A fraction of the 1% is titanium, magnetite, rutile, garnet and zircons, yet the electric ray finds and concentrates these rare minerals in its inner ears. The question is why. The top ridges of the sand ripples are made of lighter quartz, heavy minerals are found in the lower ripple valleys. Perhaps the ray can detect magnetic stripes in the sea floor.

Many of these minerals are magnetic or radio active. Why the electric ray concentrates them deep within its skull or why it has an orange brain stem when no other organism has one is also a mystery.

The electric rays are not born with these exogenenous crystals. Their inner ears are empty at birth, but they start mining sand immediately after leaving the mother. They do, however, have electric organs and are capable of discharging. How the mother puts up with these voltages from inside is unknown.

The electric ray and a few other electric fishes are nature's biological batteries. The lesser electric ray eats worms and eels and converts it to powerful energy for defense, prey detection and communication. There is a vast literature on the biochemistry of the ray and its ability to produce neurotransmitters like acetocholine. However, we hope that further investigation, modeling and understanding of how the ray produces electricity and why it mines magnetic and radio active sand grains may one day help us with our own energy problems.

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