The Hindu : Kerala / Thiruvananthapuram News : Marine aquarium breeds electric rays in captivity

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Thursday, Nov 19, 2009
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Kerala - Thiruvananthapuram

Marine aquarium breeds electric rays in captivity

Special Correspondent

Thiruvananthapuram: The marine aquarium established by the Central Marine Fisheries Research Institute (CMFRI) at Vizhinjam, near here, has recorded the rare incident of spawning electric rays in captivity.

As many as 12 young rays, each about 12 cm in length, are now swimming about in the tanks at the aquarium. The electric ray (species Torpedo marmorata) is capable of giving an electric shock of 30 to 220 Volt.

The young ones are also capable of giving mild shock for defence and for catching prey.

The parents were collected from the sea about five months back and kept in a tank at the aquarium.

Electric rays are ovoviviparous. The egg hatches inside the mother but nutrition is from the egg yolk present in the egg, whereas in mammals it is from the mother through placenta

Electric rays have a rounded pectoral disc with a stout, muscular tail.

The body is thick and flabby, with soft, loose skin devoid of dermal denticles and thorns. A pair of kidney-shaped electric organs is found at the base of the pectoral fins.

They are bottom dwelling fish, found from shallow coastal waters down to 1,000 metres (3,300 ft) depth.

They are sluggish and slow moving, propelling themselves along with their tails, rather than using their disc-shaped bodies, as other rays do.

They feed on invertebrates and small fish. They lie in wait for prey below the sand or other substrate, using their electricity to stun and capture it.

According to M.K. Anil, scientist at CMFRI, Vizhinjam, the electric ray is known to be the most electro-sensitive of all zoological organisms.

The eyes are situated on top of its head, providing for poor vision which must be balanced by the use of other senses, including the detection of electricity.

Many species of rays and skates outside the family of the electric ray have electric organs located in the tail.

However, the electric ray possesses two large electric organs on each side of its head.

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