LECTURE NOTES IN ZOOLOGY

Module 2. SUBKINGDOM MULTICELLULAR ANIMALS (METAZOA). DIVISION PRIMITIVE METAZOA (PROMETAZOA). LOWER METAZOA (EUMETAZOA)

Content Module 2.3. Flatworms, Nemerteans, Rotifers, Spiny-headed Worms

Topic 2.3.3. Phylum Rotifera (Rotifers)

General characteristics of the phylum. Origin, evolution, paleontological data, modern diversity, geographic distribution, and their role in nature and human life. Overview of the main taxonomic groups important for human life and the functioning of natural ecosystems. Class Rotatoria (Rotifers).

Aquatic, predominantly freshwater organisms, including both benthic and planktonic forms. A small number of species have adapted to terrestrial life among mosses, Lichens, etc. They are among the smallest (0.04 - 2 mm) Multicellular animals, featuring a diverse and sophisticated body Organization. Over 1,600 species have been described. In Ukraine, 500 freshwater and over 100 marine species are known. In terms of their level of organization, they are close to pseudocoelomates. The body is covered by a syncytial hypodermis layer, which may secrete a cuticle or thicken to form a lorica (shell). Cilia in the integument are retained only in the corona (a specific Structure). There is no basement membrane or muscular-cutaneous sac; the musculature consists of separate differentiated bundles (smooth and striated Muscles). A primary body cavity, the schizocoel, is present. During evolution, it arises in place of the parenchyma As a result of the Separation and breakdown of parenchymal Cells, hence its alternative name - schizocoel (cavity of disintegration). The digestive tract is complete; In addition to the foregut and midgut, There is a hindgut and an anus. The Pharynx contains a specialized chewing apparatus called the mastax.

Class Rotatoria (Rotifers). Free-living, motile animals; some species lead a sessile lifestyle, while a small number are parasites of certain invertebrates, particularly Protozoans (heliozoans). Many species form colonies consisting of several hundred or sometimes thousands of young free-swimming individuals that, upon connecting, secrete large amounts of gelatinous substance. The colony either attaches to a substrate (Lacinularia flosculosa) or swims freely (Sinantherina socialis).