Common Torpedo - Biology and Ecology

Biology and Ecology

As with other members of its family, the common torpedo can subdue prey and deter threats with strong electric shocks generated from a pair of large electric organs. Derived from muscle tissue, each organ is made up of 400–500 columns, each column constituting a stack of around 400 jelly-filled disks ("electroplaques"). The columns together essentially act as batteries connected in parallel. The discharge of the electric organs can reach 200 volts, and may occur singly or in bursts ("trains"). Experiments in vitro have found that the nerves inervating the electric organ essentially stop functioning at temperatures below 15 °C (59 °F). Winter water temperatures regularly drop below this threshold in the wild, suggesting the ray may not use its electric organs for part of the year, or has a yet-unknown physiological mechanism to adapt electric organ function to colder conditions.

Solitary and nocturnal, the common torpedo spends much time resting on the sea floor, often buried in sediment. It is an ambush predator that pounces onto prey and stuns them with electricity, the process taking only a fraction of a second. Once the prey is immobilized, it is manipulated to the mouth with motions of the disc, and swallowed whole. Adults feed almost entirely on small benthic bony fishes, including soles, herring, mullet, gobies, goatfishes, porgies, dragonets, and jack mackerels. Large decapod crustaceans are a minor secondary food source, while very rarely skates may be consumed. Juveniles are less exclusively piscivorous than the adults and feed on a variety of invertebrates as well. The most significant prey species differ between seasons and geographic regions. For example, in the Tyrrhenian Sea, juvenile common sole (Solea solea) are by far the most important prey item in autumn and winter, but in spring and summer they become less available and other fishes figure more prominently in the ray's diet. Known parasites of this species include the tapeworm Phyllobothrium lactuca, and the monogeneans Amphibdella paronaperugiae and Amphibdelloides benhassinae.