Water fleas - Daphnia
The genus Daphnia , is rather frequent in fresh water and the distinctive mark is the head form and large front eye.
Video 1 shows Daphnia together with the green algae Volvox. The feet are used in catching the”food”, back the intestine the heart is located. In the sac are some embryo developed from not fertilized eggs.
Video 2 vshows resistant eggs (ephippium). A fertilized egg can develop thickened walls, which are dark in colour. The egg can lie dormant for some month at the bottom of the pond. The egg eventually develops and then the cycle starts again. Notice the heart in front of the egg.