Most parasites are also specialized to live only in particular parts of their host. Malarial parasites live in the red blood cells of vertebrates. Theileria parasites of cattle, sheep and goats live in the lymphocytes of the mammal, and in the epithelial cells, and later in the salivary gland cells, of the tick that is the disease vector, and so on.
By transplanting parasites experi- parasites may search mentally from one part of the host's for habitats within body to another, it can be shown that their hosts many home in on target habitats.
When nematode worms (Nippostrongylus brasiliensis) were transplanted from the jejunum into the anterior and posterior parts of the small intestine of rats, they migrated back to their original habitat (Alphey, 1970). In other cases, habitat search may involve growth rather than bodily movement. For instance, loose smut of wheat, the fungus Ustilago tritici, infects the exposed stigmas of wheat flowers and then grows as an extending filamentous system into the young embryo. Growth continues in the seedling, and the fungus mycelium keeps pace with the growth of the shoot. Ultimately, the fungus grows rapidly into the developing flowers and converts them into masses of spores.
Was this article helpful?