New data support the presence of more than one species in the genus Helicostomella (Ciliophora: Spirotrichea: Tintinnina)

Abstract

Since its original report, Helicostomella includes 7 species, H. subulata, H. edentata, H. fusiformis, H. kiliensis, H. longa, H. lemairei, and H. antarctica based on the morphology of lorica. However, this approach is potentially problematic given the fact that these features apparently have a considerable phenotypic plasticity which could be affected by the organism’s life stage and environmental factors. Later based on reviews of previously published articles as well as large scale samplings, Souto (1979), Alder (1999), and Santoferrara & Alder (2009) suggested there might be only one species in the genus, H. subulata, since the important taxonomic features overlap to some degree and it is impossible to establish a cutting point between these species. However, as no species of the name bearing genus Helicostomella has ever been characterized genetically, the gene sequence data of H. subulata can either support or disprove this morphological hypothesis. From September 2008 to August 2009, we performed a daily sample collection approach for Helicostomella spp from Jangmok Bay, southern coast of Korea. In our study, we recorded the temporal distribution and morphological variability of Helicostomella spp. Furthermore, we sequenced the SSU rDNA and Internal Transcribed Spacer 2 (ITS2) sequences of two major forms of Helicostomella. Phylogenetic analyses show a close relationship