Page 146 - The Miracle of Migration in Animals

THE MIRACLE OF MIGRATION IN ANIMALS

Superior Intelligence in Migrating
Plankton

Plankton is a Greek word meaning “wandering” or “drifting.”
For this reason, it is a common term for the plant and animal organ-
isms that drift freely in oceans and lakes. While some plankton are
too small to be seen with the naked eye, they can also be as large as 3
meters (10 feet) in length, like large jellyfish.
Both plant and animal plankton migrate in vertical and horizon-

tal directions. The more important one is vertical migration, but usu-
ally movement is achieved in both directions simultaneously. The
basic reason for vertical movement is feeding. The plankton move up
and down in the water to find food. In plant plankton, increased
amounts of gas or oil, or reduced levels of salt achieve upward move-
ment. The converse applies to sink. Animal plankton swim by means
of legs, stiff hairs and fins, migrating in accord with the time of year
and the timing of reproduction.
The most important factor influencing the timing of their migra-
tion is thought to be light. At dusk, plankton move towards the sur-
face, and as light increases towards dawn they return to the depths. 42

Food supply and the presence of predators also influence their migra-
tion. For these creatures, most of which are of microscopic propor-
tions, to time migration to their best advantage, they must have prior
knowledge of the dangers and benefits that await them. To take pre-
cautions accordingly means they have the ability to judge, because
the plant plankton they feed on grow only near the surface of the
water, where there is ample sunlight. But because the predators, the
concentration of which is higher in these surface waters, can see them
more easily in the daytime, it’s dangerous for them to feed by day. For
this reason, animal plankton stay in the depths during the day and

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