APICOMPLEXANS
Apicomplexansare protozoa that live and grow inside another living organism
(obligate intracellular parasites) and cannot move by themselves (nonmotile).
Apicomplexans have an apical complex of organelles that form an apex (tip).
This tip contains enzymes that enable it to penetrate the tissues of a host.
Here are common Apicomplexans:- Plasmodium: Plasmodiumlives in the female Anopheles mosquitoand
causes malariawhen the mosquito bites a human. Symptoms of malaria
include severe chills and fever or “rigor” (a sudden chill or coldness that is
followed by fever). - Bebesia microti: B. microtilives in ticks and causes bebesiosis when the
tick bites someone. B. microtithen enters red blood cells where it multi-
plies quickly. At first there aren’t any symptoms (asymptomatic). However,
soon afterwards there is a high fever, headache, and muscle pain as B.
microtidestroys red blood cells. This causes the person to become anemic
(insufficient hemoglobin because of the reduction in the number of red
blood cells) and show signs of jaundice(an increase in bile, causing the
skin and eye sclera—the white part of the eye—to yellow). - Toxoplasma gondii, also known as T. gondii, lives in cat feces and raw
meat and causes lymphadenitis (infection of the lymph nodes), which can
have a devastating effect on people who are immunocompromised, such as
AIDS patients. T. gondiicauses congenital infections in a fetus because it
can pass from the mother to the fetus through the placenta.
Helminths
Helminths are parasitic, multicellular eukaryotic animals. The majority of these
animals belong to the phyla Platyhelminthes and Nematoda. There are free-
living members of these phyla; however, in this section, only the parasitic organ-
isms are discussed.
Many parasitic helminths do not have a digestive system and instead absorb
nutrients from the food that is consumed by their host organism, the host’s body
fluids, and the host’s tissues. Parasitic helminths have a very simplistic nervous
system because they have to respond to very few changes in their host’s environ-
ment. They lack or have reduced means of locomotion because they are transferred(^178) CHAPTER 11 The Eukar yotes