Sporozoans

Sporozoans - Sporozoans belong to a protozoan phylum Sporozoa. It is an old taxon first described and used in 1879 by by German zoologist, Karl Georg Friedrich Rudolf Leuckart. This is no longer recommended for use and phylum Apicomplexa is suggested instead. The phylum is comprised of protozoans that are characterized by having a special organelle called an apical complex. Most of them are single-celled, parasitic, and spore-forming.

The old phylum Sporozoa belongs to protozoa, which in turn, belongs to Kingdom Protista of the previous five kingdom scheme of classification. The protozoans are divided into four major groups that are classified based on the means of locomotion, i.e. the flagellates, the amoeboids, the sporozoans, and the ciliates. Sporozoans are characterized by being one-celled, non-motile, parasitic, and spore-forming. Most of them have an alternation of sexual and asexual stages in their life cycle. An example of sporozoan is the Plasmodium falciparum, which is the causative agent of malaria. This scheme too is no longer encouraged for use.

This is a large group (30,000 species) of parasitic non-photosynthetic protists that wholly lack flagellated stages with the exception of male gametes.These organisms all have an apical complex at some point in their life cycle and are homogenous in cellular organization. Their organization includes the following common features:

a. The apical complex is a set of secretory and cytoskeletal structures that enables the young parasite to enter a host cell. It consists of several components: two apical rings a conoid - an open cone of spiral rod-like elements polar wing of dense granular material that connects the ends of the longitudinal cytoskeletal microtubules rhoptries and micronemes. These are modified secretory vesicles.

The rhoptries are sac-shaped structures that may be either long or short depending on the species, while micronemes are elongated thread-like structures. Rhoptries and micronemes are believed to be part of the same secretory system by some researchers. They are involved in secretion of enzymes and other proteins that are involved in removing extracellular material and allowing the parasite to enter the host cell.

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