Download Hungry Shark Evolution Mod Apk Raja Apk |BEST|
Desiderato Merriwether
When hungry, Scyliorhinus and Raja perform well-aimed feeding responses to flatfish, even if the prey have covered themselves with sand. The object of the present study was to determine whether the sharks and rays use the bioelectric fields of the flatfish to detect the position of their prey.
Quite another type of behaviour appeared when the animals became hungry. They then spontaneously began to explore the pool, obviously searching for food, the sharks steadily swimming immediately above the sand, the rays walking on it by means of the leglike anterior parts of their pelvic fins. When a small piece of whiting was thrown into the sea water, the behaviour of the animals generally did not change within the first few seconds. However, as soon as the odour of the food reached them they began to swim very fast, excitedly circling around and snapping at the various objects, such as small pebbles and air stones, that they struck at the bottom of the pool. Yet, both the sharks and rays, although attracted by the odour from the food, could not find its source until actually touching the piece of whiting or at least passing it closely. They then stopped abruptly at, or turned sharply towards, the food and swallowed it voraciously.
To see how the sharks and rays behaved in the presence of living prey in eight experiments a small specimen of the flatfish Pleuronectes platessa, the plaice, was introduced into the pool. As soon as it was released into the water, the plaice went to the bottom, and hid itself under the sand. If the sharks and rays had been fed shortly before, they were not visibly aroused by what happened in their surroundings, although certainly aware of it (Kalmijn, 1966). When swimming and accidentally coming across the plaice, they sometimes showed a weak approach or even an avoidance response to it. However, as time went by and the sharks and rays became hungry, they began to pay more attention to the plaice and after intermittently starting and chasing their prey, they finally devoured it, although often only after several hours.
For analysing the feeding behaviour, it was desirable to have the whole process intensified and shortened. This could be achieved by offering the plaice to sharks and rays that had not been fed for over a week. A more convenient method, however, was to put the plaice into the pool before the sharks and rays became hungry, and then, after the fish had settled down, to motivate the test animals by an odour stimulus. A few drops of whiting juice, diffusely spread throughout the water, were sufficient to produce a frenzied feeding behaviour, even if the sharks and rays had been fed only 2 days before.