Rhoptry

They are club-shaped organelles connected by thin necks to the extreme apical pole of the parasite.

The proteins they contain are important in the interaction between the host and the parasite, including the formation of the parasitophorous vacuole (PV).

[2][3] Rhoptries are one of the three characteristic secretory organelles present in all Apicomplexa along with micronemes and dense granules.

[4] Rhoptries and micronemes are localized at the apical complex of the Apicomplexan organism, which suggests common ancestry of the members of the phylum and the evolution process they have experienced.

[5] Those two classes of proteins, RONs and ROPs, follow the typical secretory pathway from the endoplasmic reticulum to the Golgi, then finally, where they are normally stored, the rhoptry.

[9] Pre-rhoptries elongate and mature into the functional rhoptries just before cytokinesis, which then move to the apexes of the parasites to localize to their normal position—the apical complexes.

[4] The three unique secretory organelles of Apicomplexa—micronemes, rhoptries, and dense granules—release their contents by exocytosis at different stages of the host invasion as the process is regulated in time and space.