SUPPORTING LECTURE NOTES IN ZOOLOGY

Module 1. ZOOLOGY AS A SCIENCE. SUBKINGDOM PROTOZOA

Content Module 1.2. Subkingdom Protozoa. General Characteristics

Topic 1.2.4. Phylum Microspora

General characteristics of the phylum. Origin, evolution, paleontological records, contemporary diversity, geographic distribution, and role in nature and human life. Overview of major taxonomic groups essential to human life and the functioning of natural ecosystems. Class Microsporea. Minute (a few micrometers in size) intracellular parasites of animals, ranging from Protozoans to vertebrates and humans. The highest species richness is found among Arthropods. Hyperparasitism (in gregarines, trematodes, and parasitic nematodes). At the end of their life cycle, unicellular spores are enclosed in a single shell containing a mono- or binucleate germ (sporoplasm) and an extrusion apparatus (from extrudo - to thrust out) with a polar tube. Cell/35.html">Mitochondria and Lysosomes are absent. A single class.

Class Microsporea. Over 1,000 species (2–5% of actually existing forms). Vegetative stages (sporoplasm and meront) reside in the Cytoplasm, rarely in The Nucleus. Infection occurs via the Digestive System. The smallest measure 1–16 µm. Spores possess a trilaminar shell, a mono- or binucleate germ (sporoplasm), a polaroplast, a posterior vacuole, a polar tube, and a polar anchoring disc. All Organelles, except for the germ, form the extrusion apparatus. The Mechanism of extrusion is not yet fully understood. The region of the shell is digested by the host's digestive juices, allowing Water to enter the spore, which is absorbed by the polaroplast. This causes a sharp increase in internal pressure, resulting in the rapid, lightning-fast uncoiling and eversion of the polar tube, acting much like a gunshot. The sporoplasms enter the invaded cell or the bloodstream. The intrasporal sporoplasm lacks a membrane and organelles. Inside the host cell, it develops a membrane and organelles (Endoplasmic reticulum, Ribosomes), becoming a meront (schizont), which undergoes schizogony or, less frequently, binary fission (yielding two merogonial generations), followed by sporogony to form a sporont (characterized by a secondary shell and reorganization of the nuclear apparatus) involving a sexual process with nuclear fusion (autogamy). The First and Second nuclear Divisions of the sporont are meiotic, followed by mitotic divisions. Reorganization of the nuclear apparatus occurs via various pathways. A multinucleated plasmodium gives rise to numerous sporoblasts and subsequently spores. Spore activation involves the enlargement of the polaroplast, transforming the simple sporoblast cell into a complex spore. In some species, merogony is absent, and the sporogony process becomes more intricate. A mucous layer may be distributed evenly, forming long threads or short bridges between spores. Spore production ranges from 10 thousand to 100 million. Pathological changes in Cells include mortality during wintering, diapause, molting, or stress, and less commonly, acute diseases resulting in rapid death. They colonize cells with high metabolic rates (secretory or tumor cells), functioning as "tumor hyperparasites." They disrupt the function of the host's Gonads, leading to complete sterility, and interfere with molting, metamorphosis, and diapause. Microsporidians of Blood-sucking mosquito larvae inhabit small crustaceans and other aquatic animals. Nosema bombycis causes the death of silkworms. N. apis causes nosemosis (diarrhea) in bees. About 80 species parasitize freshwater and marine Fishes (cod, herring, flounder, eel, trout), commercial crustaceans (crayfish, crabs, shrimps), and mussels. Five species of microsporidians infect warm-blooded animals, including humans (e.g., Encephalitozoon cuniculus). Up to 30% of AIDS patients succumb to microsporidiosis. Approximately 70% of species are found in arthropods, blood-sucking insects, forest pests, and agricultural crop pests. Their potential in the biological control of pest invertebrates.