All sponges are aquatic and most of them are marine. Where Freshwater sponges exist? Freshwater sponges are found in fair numbers—but belonging to relatively few species—in ponds and lakes, streams and rivers, even in lakes formed in the craters of extinct volcanoes 10,000 feet above sea-level. Where Marine sponges exist? Marine sponges exist in large … Read more
Where Mesozoans found? The mesozoans are tiny parasitic animalcules found in certain marine invertebrates. Orders of Mesozoans Dicyemida Orthonectida Simple multicellular structure has provoked much speculation about their place in any systematic classification of the animal kingdom. How Mesozoans infect the kidneys? In a way still unknown, the worm-like dicyemids infect the kidneys of young squids … Read more
Spirotrichs (Subclass Spirotricha) Members of this class are mostly free-living and have a more highly developed AZM than the primitive hymenostomes. The AZM winds clockwise to the cytostome. Many of the more advanced spirotrichs have no somatic cilia but this loss is secondary. There is a wide variety of structure which prevents generalizations on morphology; … Read more
The ciliates (Class Ciliata) These protozoans have many cilia and nuclei of two sizes. Because the mastigophoran Opalina also has many flagella (or cilia), it is the nuclei that act as the criterion and establish the true ciliates as a distinct group. Other features include a kinety system of fibrils and granules for co-ordinating the … Read more
The spore-formers (Class Sporozoa) This class, like many others making up the phylum, is a dumping ground for probably unrelated families and orders. Its characters are based on the fact that all are well-adapted parasites. To this end, reproductive efficiency is exaggerated and structural complexity reduced. The same stages, though not the names, are found … Read more
Class Actinopoda This class contains two orders, Heliozoa and Radiolaria, which are superficially rather similar. Individuals of both orders may have siliceous skeletons arranged as spheres with holes in them. Axopodia, pseudopodia stiffened with axial filaments, project through the holes. Food is caught on the axopodia and is drawn by the movement of the cytoplasm … Read more
Rhizopods (Class Rhizopoda) This class includes the various species of amoebas. Typically amoebas crawl on the surface of the mud, submerged plants, in the spaces between soil particles, or inside animals as parasites. Locomotion is by means of pseudopodia, which may be long and thin but usually unbranched (filopodia), long, thin, and branched, uniting with … Read more
Zoomasts (Subclass Zoomastigina) These are flagella-bearing protozoans which have truly animal methods of nutrition. Many are parasitic and have been extensively studied as they affect the life of man. The number of free-living species is not certain. They are morphologically diverse and are best considered in their orders. Protomonads (Order Protomonadina) All members have only … Read more
The flagellates (Class Mastigophora) This class contains organisms which are actively motile by means of flagella. They may have a single flagellum or they may have hundreds, so that they bear a strong superficial resemblance to dilates. The nuclei are usually restricted to one per cell but if there is more than one they are … Read more
Phylum Protozoa (PROTOZOANS) The term Protozoa embraces the vast assemblage of living organisms, some free-living, some parasitic, that appear to organize their whole lives as single cells. Estimates of the total number of species are difficult to make because the definition of the term species is particularly unclear in the Protozoa. It is safe to … Read more