[Edited_by_A._Ciancio,_C.N.R.,_Bari,_Italy_and_K.(Bookos.org)

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L.P.S. VAN DER GEEST
fusion of nuclei or nuclear material that occurs during sexual reproduction). The
nucleus undergoes subsequently meiosis, resulting in the formation of haploid
ascospores inside the asci. These asci are often borne in or on top of a sporocarp.
Very few Ascomycota have been isolated from mites. These isolations concern
mainly Laboulbeniales infections in a number of mite species. Laboulbeniales is an
order of fungi with more than 2,000 species. They are small, often minute fungi that
have an obligate association with arthropods, mainly insects, and they lack
mycelium. On their host, they appear as scattered or densely crowded bristles or
bushy hairs which may form furry or velvety patches on certain part of the host’
integument. These plume-like structures and triggers help in ascospore release when
the arthropod comes into contact with a mature thallus.
The site of attachment is usually limited to definite regions on the integument of
each host. The entire thallus (body) is derived from enlargement and subsequent cell
division of the two-celled ascospore. Below the surface of the arthropod cuticle
absorption through a peg- or root-like haustorium provides a nutrition source for the
fungus; however, the fungal parasites of this group do not appear to cause much
damage to the host. A few species have been found on mites, including a Rickia sp.
and an unknown species on Hirstionyssus (Demanyssidae) (Steinhaus & Marsh, 1962).
5. DISEASES CAUSED BY EUKARYOTIC MICROPARASITES
Traditionally, the animal kingdom has been divided into two subkingdoms: the
Protozoa (unicellular eukaryotes) and the Metazoa (multicellular animals). In
modern taxonomy, a kingdom Protista is considered of which the members are either
unicellular, colonial or multicellualar. All these organisms are eukaryotes,
The Protista are divided into three major groups: the Protozoa, the Algae and
the Fungus-like protists. Protozoa are defined as single-celled eukaryotic organisms,
that feed heterotrophically (feeding both on both organic and inorganic raw
materials) and exhibit diverse motility mechanisms. Traditionally, four divisions are
discerned, based on their mode of mobility:
- Flagellata (Mastigophora) are protozoa that move by means of flagellar
action. Some flagellates have their flagella attached in a structure called an
undulating membrane. They often have symbiotic relationships with
multicellular organisms.
- Rhizopoda (Amoebozoa) Rhizopoda are protozoa that move by employing
pseudopodia, which are covered by membranes. These pseudopodia are
cytoplasmic extensions that are not only used for locomotion but also to
engulf food. Amoebae live in moist terrestrial and aquatic environment.
- Apicomplexa (or Sporozoa). The Sporozoa are parasitic spore formers that
do not move by their own power. Plasmodium vivax, the cause of malaria,
is a sporozoan.
- Ciliata (Ciliophora) Ciliata are protozoa that move by means of cilia action.
Cilia are small and numerous; flagella are large and few. Because of the
tremendous variety in ciliary arrangements and functions, ciliates are
among the most diverse cells in the biological world.