Tintinnids are protozoans that are conical or trumpet-shaped with well developed ciliation around the mouth opening. The rest of the cell lacks cilia. Most tintinnids are marine, but some can also be found in fresh and brackish water (“Tintinnid“, 2016). Delimitation of different species based on morphological criteria alone is very difficult. This is due to the range of variability in shapes and sizes. The variability can be very high even within a single species depending on life stages and environmental conditions (Xu, Sun, Shin, & Kim, 2012).
Xu, D., Sun, P., Shin, M., & Kim, Y. (2012). Species Boundaries in Tintinnid Ciliates: A Case Study – Morphometric Variability, Molecular Characterization, and Temporal Distribution of Helicostomella species (Ciliophora, Tintinnina). Journal Of Eukaryotic Microbiology, 59(4), 351-358.
The original photo for the featured tintinnid image can be found here: http://www.kahaku.go.jp/research/db/botany/bikaseki/img/f14-a.jpg