Successive Changes in Animal Life during Hydrosere
The successive changes in plant communities in the different seral communities of a hydrosere. The question arises, is there any change in the animal life along with the different seres. There are certainly changes in the animal life also, but these may not be as obvious as in case of plant community. In an aquatic ecosystem like this, protozoans Like Paramecium, Amoeba, Euglena and many others are the pioneers. When the planktonic growth forms are very rich, then animals like blue gill fish, sun fish, largemouth bass etc. start appearing. Some caddisflies are also found. In the second stage, that is, the submerged stage, the caddisflies are replaced by other animals that may creep over the submerged vegetation. Thus dragonflies, mayflies and some crustaceans as Asellas, Gammarus, Daphnia, Cypris, and Cyclops inhabit the pond at this stage. At the floating stage, the animals life is chiefly represented by Hydra spp., gill breathing snails, frogs, salamanders, diving beetles, and other insects. There also appear some turtles and snakes. At the reed-swamp stage, the pond becomes shallower, and the bottom starts becoming exposed.
The floating animals are replaced by different species of mayflies and dragonflies, whose nymphs remain attached to submerged parts of the vegetation, and adults present on the surfaces of exposed parts of vegetation. Gill-breathing animals like snails are replaced by lung breathers as Lymnea, Physa and Gyraulus. Among insects, water scorpion, giant water bug, scavenger beetles etc. are present at this stage. The bottom of the pond is now inhabited by some annelids, mud pickerel and bull-heads. Red-winged black birds, kingfisher, great blue heron, swamp sparrow, ducks, musk rats, and beavers become common in the area. At the sedge-meadow stage, the animals like snails as Anodonta, Psidium become common. Finally, at the woodland stage, under terrestrial conditions, most of the terrestrial forms of animal life appear in the area.