Current knowledge of the starvation and reproduction stages of the limnic species Holophrya teres (Ciliophora: Prostomatea)

Abstract

This study presents a light microscopy observation on the life cycle of the prostomatid ciliate, Holophrya teres. We were able to make distinctions between its reproduction and starvation phases. Within these phases, we observed the following stages, namely the trophont, protomont and tomont, as well as reproductive (tomites), temporary and resting cysts. Additionally, we also described two types of active specimens after the excystation process, especially from the reproductive cyst (theront) and from the resting cyst. The main differences between these two specimens were in the shape and size of the cell, the rate of the regeneration, and the speed of the excystation process itself. To date, the life cycle of the genus Holophrya has only been known synonymously with the general model of the life cycle of the genus Prorodon. However, the characteristics of these two cycles are not identical at all. For this reason, we also focused on an overview of currently available data, and we have uncovered several specifics of the life cycle of H. teres for the first time. This study has revealed that the life cycles of limnic ciliates are somewhat more diversified than the life cycles of terrestrial groups of ciliates.