Farinocystis

This genus was created by Weiser in 1953.[1]

The type species is Farinocystis tribolii.

The species in this genus are spread by the orofaecal route. They infect the larva, pupae and adults of mealworms. The hosts may become black when heavily infected.

Eight elongate sporozoites emerge from each oocyst in the midgut of the host. These then migrate to the fat body where they become intracellular.

The meronts enlarge, becoming rounded or elongate and acquire up to 200 small nuclei. Elongate or spherical merozoites with one nucleus bud from the surface of the meront or are preformed in the meront and are released upon its rupture. The merozoites may form a new generation or develop into meronts with large nuclei which release uninucleate merozoites upon rupture of the meront.

The large nuclei are about double the size of the small nuclei at about 2-4 µm diameter. Pyriform, spindle shaped or ovoid merozoites with large nuclei differentiate into spheroidal gamonts.

The gamonts associate in head to head syzygy with the conoidal complexes juxtaposed.

The gametocytes are hemispherical. A common wall forms around the juxtaposed gamonts to form a gametocyst. Within this the two gamonts are now known as gametocytes

The gametocyst enlarges from 5 to 15 µm in length while the gametocytes undergo nuclear division and the nuclei arrange themselves around the perimeter of the gametocytes except at the interface between the two cells. The peripheral cytoplasm condenses around the nuclei to form 16 isogametes within each gametocyte. The interface between the gametocytes breaks down and the gametes fuse forming as many as 16 zygotes.

Each zygote forms 8 lemon shaped oocysts with polar thickenings.

The sporozoites are elongate and attached to the poles of the oocyst.

The oocyst leaves the host either via the faeces or after the death of the host and its subsequent disintegration.

• Mealworm (Tenebrio molitor)