Invertebrates Facts

  • Invertebrates are multi-cellular and all the cells have different responsibilities to keep the animal alive.
  • Invertebrates have no backbone or bony skeleton or cells wall like all other animals.
  • Invertebrates like echinoderms do not have heads.
  • There are millions of invertebrates living in our house in the name of dust mites which are hardly visible to human eyes.
  • Invertebrates under a process called metamorphosis through which they change form as they grow.



The phylum Rotifers comprises of microscopic and near-microscopic pseudocoelomate animals. They are largely found in freshwater and some species are found in saltwater also.

Some species of rotifers are free swimming and are called plank-tonic and some other species move by inch-warming. They are also found in the moist soil, where they live in the thin films of water formed around soil particles.

Not only in the running water like rivers and streams, but also found in the still water like lake bottoms, pools. They are also seen in mosses, lichens, rain gutters, soil or leaf litter, mushroom growing near dead trees and also in the sewage treatment plants.

Rotifers are small in size and have soft-body, so they are not highly favored for the fossilization. The only hard part within the body of the rotifers is their jaws, and that can be preserved in the fossil record. Its size may be too small, so the detection makes it quite complex.

Most of the rotifers have a same cell count of about 1000. The size of the rotifers may vary from 0.00394 in to 0.098 in. The body is mainly divided into head, trunk and the foot regions.

The wheel organ in the head is also called ad corona, which is used for both locomotion and feeding.

The trunk may be of various shapes like elongated form, telescopic form, retractable pseudo-segments and also the sacciform form

Features of Rotifers:

  • Rotifers can live in high eutrophication waters
  • Rotifers are the live food for larval fish and crustacean culture
  • Bdelloid rotifer can live in any water like distilled water, sea water and salinity water
  • The characteristics of rotifers like its body size and its slow mobility pretend it as a good prey for larvae
  • Rotifers are dioecious and the female ones are always larger than the male ones

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