Invertebrate Zoology: A Study Guide - T. A. Dauda 2014
Protozoa
Sporozoans
The phylum Apicomplexa comprises approximately 3,600 species of parasitic Protozoa that inhabit epithelial, Blood, and other Cells in animals and humans.
Due to their parasitic lifestyle, apicomplexans have undergone, on the one hand, a simplification of body Organization and, on the other, a complexification of their life cycle. For instance, Organelles for capturing and ingesting food, digestive and contractile vacuoles, and locomotory organelles have been lost. At the same time, they exhibit a distinct alternation of asexual reproduction, sexual processes, and sporogony—The formation of spores that enable the embryo to survive adverse environmental conditions and spread to new host organisms.
Asexual reproduction typically occurs via multiple fission (schizogony), and in some forms, via binary fission. The sexual process takes the form of the fusion of male and female reproductive cells (Gametes).
The zygote formed As a result of gamete fusion typically secretes a protective coat.
In this form, it is referred to as an oocyst. Inside the oocyst, sporozoites are formed via sporogony; they either lie freely within the oocyst or are contained within sporoblasts that possess their own wall. Oocysts in which sporoblasts and sporozoites have developed are called sporocysts.
The phylum Apicomplexa is divided into 2 classes:
1) Coccidiomorphea (Coccidiomorpha);
2) Gregarines (Gregarinina).
Representatives of the Class Gregarines parasitize the intestines of Arthropods and are of no practical significance.
Last update: 13/08/2026
Editorial and Educational Adaptation: This material has been compiled based on the primary/original source text. The project team performed an editorial review, corrected technical inaccuracies, structured sections, and adapted the content for an educational format.
What was processed:
- elimination of formatting defects (OCR errors, structural breaks, corrupted characters);
- editorial organization of content;
- standardization of terminology in accordance with academic sources;
- verification of factual statements against the original source text.
All mentions of the author, publication year, and origin of the primary text have been preserved in accordance with the source.