Marbled Electric Ray

The marbled electric ray (Torpedo marmorata) is a benthic fish found in the coastal waters of the eastern Atlantic Ocean. This species can survive in environments with low levels of dissolved oxygen, such as tidal pools. It has a circular pectoral fin disc, a muscular tail with two dorsal fins, and a large caudal fin. The marbled electric ray can be identified by the long projections on the rims of its spiracles and its dark brown mottled color pattern.

This electric ray is nocturnal and solitary, often burying itself in the sea floor with only its eyes and spiracles exposed. It is a slow-moving predator that feeds primarily on small bony fishes, using electric bursts to subdue its prey. When threatened, the marbled electric ray can emit electric shocks to drive off predators. The species reproduces through aplacental viviparity, with females giving birth to litters of 3–32 pups after a gestation period of 9–12 months.

While the electric shock delivered by the marbled electric ray can be severe, it is usually not life-threatening. The ray's electrogenic properties have been known since ancient times, when it was used in medical treatments. Nowadays, the marbled electric ray and other electric ray species are used as model organisms in biomedical research. In coastal demersal fisheries, the marbled electric ray is often caught as bycatch and discarded due to its limited commercial value.

The marbled electric ray is widely distributed in the eastern Atlantic Ocean, ranging from the North Sea to 🇿🇦 South Africa and the Mediterranean Sea. It is typically found in rocky reefs, seagrass beds, and sandy/muddy flats in shallow to moderately deep waters. The ray prefers temperatures cooler than 20 °C and can be found at depths of 10–30 m off Britain and Ireland, 20–100 m off Italy, and down to 200 m off 🇹🇳 Tunisia. It has even been recorded at depths of 370 m. The marbled electric ray tends to inhabit deeper areas compared to the common torpedo, which shares part of its range.

Physically, the marbled electric ray has a soft and flabby body without dermal denticles. It has a circular pectoral fin disc that accounts for about 59–67% of its total length. The ray's eyes are small, and large oval spiracles with finger-like projections are located near each eye. It has small teeth and five pairs of gill slits. Its dorsal fins are rounded and placed close together, with the second dorsal fin slightly smaller than the first. The ray's tail is short and robust, terminating in a large triangular caudal fin. Its upper surface displays a dark mottled pattern on a brown background, while the underside is off-white with darker fin margins. The marbled electric ray can grow up to 1 m long, with females reaching larger sizes compared to males.

This ray is solitary and slow-moving, often remaining motionless for long periods. It is most active at night and can tolerate low levels of oxygen, allowing it to survive in deoxygenated bottom waters or stranded in shallow pools during low tide. The marbled electric ray possesses a pair of electric organs derived from muscle tissue, which it uses to produce strong electric shocks for attack and defense. Each electric organ contains vertical columns composed of jelly-filled "electroplates" that act as a battery. The ray can produce up to 70–80 volts of electricity, and its electric shock strength decreases as it becomes fatigued.

The marbled electric ray is known to host several parasites, including tapeworms, leeches, and nematodes. As an ambush predator, the ray relies on electricity to capture its prey rather than vision. It primarily feeds on small bony fishes, with cephalopods as a secondary food source. Due to its size and electric defenses, the marbled electric ray is not often preyed upon by other animals. It exhibits different defensive behaviors depending on where it is grasped by a predator, using electric shocks and specific body postures to fend off threats.

Although the electric shock delivered by the marbled electric ray can be painful, it is rarely life-threatening. In ancient times, the ray was used in medical treatments for various conditions. Nowadays, it is mainly caught as bycatch in fisheries and discarded due to its limited economic value.