Subject:
Torpedo rays are known for being capable of generating electric shocks. The Blackspotted Torpedo Ray (Torpedo fuscomaculata) is endemic to the southwestern part of the Indian Ocean (from South Africa to Kenya in the west and on the islands of Madagascar, the Seychelles, and the Mascareignes in the east).
With two large electric organs on each side of its head, the Blackspotted Torpedo Ray can deliver an electric shock of up to 30 amperes and a voltage of 8 to 220 volts. These electricity-producing organs are made of patches of modified muscle cells called "electroplaques". The produced power can be stored in the tissues, acting like a battery. The Torpedo Ray discharges this power in powerful pulses to stun prey and defend itself from predators. These shocks are also used to stun prey, immobilising them for easy consumption by the ray.
Once the ray has discharged its stored power, it may take a while to "recharge" these electroplaques, making the ray vulnerable to predation from sharks or dolphins. Torpedo rays are often found buried under the sand, where they lie in ambush to hunt little fish, and remain out of sight from any potential predator.
These rather small rays are frequently encountered in Mauritius on sandy areas and patches of the reefs. They are easily recognised by their rounded and disc-like body shape and make a very distinctive zig-zag movement while swimming, contrasting with the elegant and gentle wing-flapping and gliding locomotion of the much bigger Pink Whiprays (Himantura fai) that share the same habitat on the Mauritian reefs and sandy areas.
When buried, they are very difficult to spot, and most of the time, only a distinctive form can be seen in the sand where the ray is lying in hiding. Sometimes, only the nostrils are visible on the substrate. It is not uncommon for an unaware diver to poke at these nostrils out of curiosity (“what the hell are these strange little things in the sand?”), only to be confronted with a sudden and nasty surprise followed by deep regret. Apparently, the shocks delivered by these rays are quite painful and can be remembered for a lifetime. This serves a purpose, as the mechanism of defence relies on the memory of the predator; any predator that has ever tried to prey on these rays will avoid a repetition of this unpleasant experience.
Technique:
Filming a fleeing fish is usually not a good idea as it delivers poor quality footage. However, knowing that any Torpedo Ray will prefer to hide under the substrate rather than flee, it was a good opportunity to follow the ray for a few meters before it settled itself in the loose sandy bottom.
Anticipating the behaviour of marine species is a good practice for any underwater videographer. Predicting what a specific animal might do next is a huge advantage when making underwater videos.
The burying process, a spectacular disappearing trick that lasts for barely two seconds, was what I was hoping to catch on film.
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