Biologie. Chemie. Zeměpis A journal for science teachers and science education researchers

SUBJECT MATTER OF EXPERIMENTS AND OBSERVATIONS OF WATER ANIMALS IN SCHOOL AQUARIUM XXVI (FRESHWATER HYDROZOANS)

Lubomír Hanel

Volume 35 (2026), issue 2 pp. 35–49 published online 19 August 2026 Czech

DOI https://doi.org/10.14712/25337556.2026.2.3

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Abstract

In the waters of the Czech Republic, there are hydroids (Hydroida) and freshwater jellyfish from the phylum Cnidaria (Olyndiidae), belonging to the group Limnomedusae (family Olyndiidae). Hydroids have a radially symmetrical body, formed by a double-layered funnel and a single receiving and simultaneously ejecting opening, around which grow tentacle-like arms varying in number (4–12) and length depending on the species. The internal undivided gastrovascular cavity extends up to the tentacles. In hydroids, the medusa stage is suppressed, in freshwater jellyfish (Craspedacusta sowerbyi) both the polyp stage (with stunted tentacles) and the hydromedusa stage appear. Both groups are characterized by the presence of stinging cells in the surface layer of the body. Polyps feed on small crustaceans, but can also overpower larger animals and even damage fish fry. The freshwater jellyfish has separate sexes, as do most species of jellyfish. They reproduce both sexually and asexually by budding. Hydroids are known for their high regenerative ability. The paper provides ideas for various observations and experiments with hydroids, especially with regard to their response to various stimuli and food intake. The paper also provides ideas for observation in school aquaria.

Keywords

school aquarium · freshwater hydrozoans · observation

How to cite

Hanel, L. (2026). Náměty na pokusy a pozorování vodních živočichů ve školním akváriu XXVI (chov sladkovodních polypovců). Biologie-Chemie-Zeměpis, 35(2), 35–49. https://doi.org/10.14712/25337556.2026.2.3

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