Zooflagellates – Protozoan

Zooflagellates are heterotrophs that are free living, commensals or symbiotic or parasitic in other animals. A number of species eg. Trichonynzpha and Myxotricha live within the gut of termites and digest cellulose that the wood-eating termites feed o but cannot digest for themselves.

Trichortympha lives as a mutualistic symbiont in the hindgut of wood-eating insects (termites and woodroaches). The anterior end of these large, complex flagellates (sometimes over 300 pm long) is covered with an elaborate pellicle and hundreds of flagella, but the posterior end extends pseudopods and ingests bits of wood. The flagellate is able to produce cellulose-digesting enzymes, but the insect host cannot; and therefore, depends on carbohydrates released by its symbionts.

Each time the insect molts, it loses the lining of the hindgut and all its symbionts. If it is unable to acquire new ones, it will starve to death, even though it continues to feed normally, for it cannot digest the wood. The flagellates are equally dependent on the mutualism and die within minutes outside the host. A young or newly-molted termite acquires symbionts by feeding directly from the anal opening of other termites in the colony. Myxotricha appears to be covered with flagella. But only four of these are true flagella and the others are a kind of bacteria or spirochetes (see margin remarks) attached to its surface. Their lashing movements enable the flagellate to swim about, and its own flagella help in steering.

                                                                 Figure: Zooflagellates parasitic in the gut of termites.

Other well known parasitic species of flagellates are Trypanosoma and Leishmania found in humans and cattle in Africa and Asia. Trypanosoma causes sleeping sickness in humans and nagana in cattle. The blood of the host is infected with the flagellate when the tsetse fly bites the host. Leishnamia is the agent for the widespread kala-azar and related disease. It affects the immune system and causes skin lesions among other effects. The host for this protozoan is the blood sucking sand fly.