Virtual Museum of Canada

LIFE UNDERWATER

PLANKTON - ZOOPLANKTON - ENVIRONMENT AND ADAPTATIONS

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Refection of aquatic plants on water

Rotifers and copepods multiply rapidly. They reproduce asexually or parthenogenically.

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Video filmed under a microscope of a cladoceran.

VIDEO - 0 min 11 s
In parthenogenesis, unfertilized ova develop into successive generations of females, which are clones of their mother.
Here we see a female cladoceran with golden eggs in her body.

Shimmering water

Therefore, populations of cladocerans and rotifers are largely composed of females.

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Dried bank

Male cladocerans, which make sexual reproduction possible, can be observed under unfavourable conditions.

Aquatic water community with water-lilies and European frogbits

Fertilized eggs fall to the bottom of the lake. These eggs are known as resistant or resting eggs. The eggs hatch when favourable environmental conditions return. These eggs produce females.

Reflection of trees on water

In some species of rotifers, the males are simplified. Their only purpose is to produce spermatozoa to fertlize eggs. These males are incapable of feeding.

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Reflection of trees and aquatic plants on water

Unlike rotifers and cladocerans, copepods reproduce sexually. Therefore, both males and females are present in the environment at the same time.

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Video filmed under a microscope of a copepod

VIDEO - 0 min 03 s
In copepods, fertilized ova are held in egg sacs on both sides of the female’s abdomen. These egg sacs, located outside the body, can contain up to a hundred eggs.

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Video filmed under a microscope of Daphnia

VIDEO - 0 min 06 s
Daphnia are cladocerans that can change shape over their lifespan (cyclomorphosis). In some individuals, the head becomes pointed and the spine at the end of the abdomen grows longer. These changes make Daphnia more difficult to swallow and thus less attractive to predators.

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Video filmed under a microscope of a cladoceran.

VIDEO - 0 min 12 s
The cladoceran Holopedium gibberum has a large gelatinous mass on its back that helps it float.

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Video filmed under a microscope of a colony of rotifers.

VIDEO - 0 min 26 s
Some rotifers live in colonies, which provide extra protection against predation. When a colony of rotifers touches another organism, like a cladoceran (as seen here), it reacts by contracting.

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Video filmed under a microscope showing a close-up of a colony of rotifers.

VIDEO - 0 min 10 s
Each rotifer in the colony moves its cilia, creating a current that brings food to the colony and assists in its locomotion.

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LIFE UNDERWATER

PLANKTON - ZOOPLANKTON