page_title: Marbled electric ray
section_title: Biology and ecology
hierarchical_section_title: Marbled electric ray / Biology and ecology
caption_attribution_description: English: Torpedo marmorata, Gallipoli peninsula, Türkiye.
context_page_description: The marbled electric ray is a species of electric ray in the family Torpedinidae found in the coastal waters of the eastern Atlantic Ocean from the North Sea to South Africa. This benthic fish inhabits rocky reefs, seagrass beds, and sandy and muddy flats in shallow to moderately deep waters. It can survive in environments with very little dissolved oxygen, such as tidal pools. The marbled electric ray has a nearly circular pectoral fin disc and a muscular tail that bears two dorsal fins of nearly equal size and a large caudal fin. It can be identified by the long, finger-like projections on the rims of its spiracles, as well as by its dark brown mottled color pattern, though some individuals are plain-colored. Males and females typically reach 36–38 cm and 55–61 cm long respectively.
  Nocturnal and solitary, the marbled electric ray can often be found lying the sea floor buried except for its eyes and spiracles. This slow-moving predator feeds almost exclusively on small bony fishes, which it ambushes from the bottom and subdues with strong electric bursts.
context_section_description: Solitary and slow-moving, the marbled electric ray may remain motionless for several days at a time. It is more active at night and spends much of the day buried in sediment with only the eyes and spiracles showing. Consistent with its sluggish nature, the marbled electric ray has a low blood oxygen carrying capacity and heart rate (10–15 beats/min), and consumes less oxygen than other sharks and rays of similar size. It is highly tolerant of being deprived of oxygen (hypoxia), allowing it to cope with deoxygenated bottom waters or being stranded in small pools by the falling tide. The ray stops breathing entirely when the oxygen partial pressure in the water drops below 10–15 Torr, and can survive such a state for at least five hours. It deals with extreme hypoxia by coupling anaerobic glycolysis to additional energy-producing pathways in its mitochondria, which serves to slow down the accumulation of potentially harmful lactate within its cells.
  Like other members of its family, the marbled electric ray can produce a strong electric shock for attack and defense, produced by a pair of electric organs derived from muscle tissue. Each electric organ consists of 400–600 vertical columns, with each column composed of a stack of roughly 400 jelly-filled "electroplates" that essentially act like a battery. This ray has been measured producing up to 70–80 volts, and the maximum potential of the electric discharge has been estimated to be as high as 200 volts. The strength of the electric shock declines progressively as the ray becomes fatigued. Experiments in vitro have found that the nerves innervating the electric organ essentially stop functioning at temperatures below 15 °C (59 °F). As the water temperature in the wild regularly drops below this threshold in winter, it is possible that the ray does not use its electric organ for part of the year. Alternately, the ray may have a yet-unknown physiological mechanism to adapt electric organ function to the cold.
  Known parasites of the marbled electric ray include the tapeworms Anthocephalum gracile and Calyptrobothrium riggii, the leeches Pontobdella muricata and Trachelobdella lubrica, the monogeneans Amphibdella torpedinis, Amphibdelloides kechemiraen, A. maccallumi, A. vallei, Empruthotrema raiae, E. torpedinis, and Squalonchocotyle torpedinis, and the nematodes Ascaris torpedinis and Mawsonascaris pastinacae.
caption: The marbled electric ray can survive in environments with very little oxygen, such as tidal pools.
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