Leopard torpedo  (Torpedo panthera)

Torpedo rays have fascinated scientists for many years due to their remarkable ability to produce an electrical discharge from large kidney-shaped organs situated between the head and the pectoral fins (3) (4). The flattened body and enlarged pectoral fins form a circular disc shape, which in this species is dark brown patterned with clusters of whitish spots (3), vaguely resembling the large cat species of its common name. The mouth is situated on the underside of the flabby body and small, bulging eyes are situated on top of the head, surrounded by small spiracles (3) (4). Spiracles are tiny holes that allow the ray to breathe when resting on the ocean bottom, as in this position the mouth is covered (4). The stout tail is substantially shorter than the length of the body disc and bears a well developed fin at its tip (3).

The leopard torpedo occurs in the Indian Ocean, where it is thought to be distributed from the Red Sea, through the Gulf of Aden, to the Arabian Sea and the Gulf of Oman, to the Bay of Bengal (1) (3).

Within its marine habitat, the leopard torpedo is known to occur in very shallow water and down to a depth of 110 metres, over muddy or sandy bottoms (2). Their flattened body is an adaptation to life on the sea bed (5).

The leopard torpedo is an ovoviviparous fish (6), meaning that the young develop inside a weakly-formed egg shell within the adult female, receiving nourishment from their yolk sac. The young hatch inside the female and are then ‘born' live (7). Sexual maturity is believed to be reached before the leopard torpedo reaches a length of 28.1 centimetres (3), but nothing else is known about the biology of this fish.

The greatest threat to the leopard torpedo is thought to be by-catch. Areas of the leopard torpedo's distribution are heavily fished, in particular with shrimp trawls, and species that dwell on the ocean bottom are particularly vulnerable to being captured in fishing trawls. It is presumed that when accidentally captured, the leopard torpedo is thrown back into the water, but whether many survive this ordeal is unknown. A lack of data means that it is not known whether leopard torpedo numbers have already decreased due to by-catch, but with shrimp trawl fisheries unlikely to lessen or stop in the future, a decline in leopard torpedo populations seems likely (1).

Before any conservation measures can be implemented, further data are clearly needed. Clarifying the leopard torpedo's distribution, and determining the extent to which it is threatened by shrimp trawling, would help establish how threatened this species is (1).

For further information on the electric organs of rays see:

• ReefQuest Centre for Shark Research:
  www.elasmo-research.org/education/topics/p_batteries.htm

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