CREATURE FEATURE: ELECTRIC RAYS

CREATURE FEATURE: ELECTRIC RAYS

This month we’re focusing on some shockingly (sorry) awesome rays – the electric rays!

The electric rays (Torpediniformes) are unique – as they are the only rays who have a specialised electric organ. This means they are able to produce a shock of 20-200 volts! Now there are some skates that can do this. But they don’t produce a shock in quite the same way.

Electric ray bodies are thick and flabby. This generally means they’re not popular for human consumption. Combined with their powerful electric shock, fishers tend to avoid them and quickly discard any that are caught as bycatch.

Their ability to produce a coordinated, external electric shock is known as electrogenesis. It’s a complicated process. But essentially – the ray is able to stimulate modified muscle cells to produce the shock. These muscle cells sit in a honeycomb pattern. Within a kidney-shaped organ in the front of either side of the disc. Used as a defensive or predatory reflex, the shock that species can produce can range from a mild warning pulse all the way up to a 200 volt shock used to incapacitate prey.

Marbled Torpedo Ray (Torpedo marmorata)

The Marbled Torpedo Ray is one species of electric ray. It’s found in the coastal waters of the Eastern Atlantic, from the North Sea and English Channel down to South Africa, including the Mediterranean Sea. Nocturnal and solitary, they reside at depths of 10 – 370m on rocky reefs, seagrass beds and sandy or muddy flats.

The species was used in Ancient Greece and Ancient Rome, its shocks used to treat conditions like chronic headaches! In the modern world, along with other electric ray species, it is caught and used as a “model organism” in biomedical research. However, the species is not commercially targeted by fishers, and bycatch is discarded due to its low commercial value.

The Marbled Electric Ray feeds predominantly on bony fishes and can produce a shock of up to 70-80 volts. It ambushes its prey from the seabed, then uses its wings to engulf prey whilst emitting electrical shocks to stun them. New-born rays are immediately capable of using electricity to hunt.

Within the Mediterranean Sea it’s the most common species of electric ray, and the population is considered stable. Despite a lack of largescale fisheries targeting this species, the population is thought to be decreasing outside of the Mediterranean. This is suspected to be due to bycatch mortality and pressure from localised fishing.

SCIENTIFIC NAME: Torpedo marmorata

FAMILY: Torpedinidae

MAXIMUM SIZE: 100cm, usually to 60cm.

DIET: Bony fishes.

DISTRIBUTION: North Sea and English Channel down to South Africa, including Mediterranean Sea.