Abstract
The genus Pseudoblepharisma is currently comprised of only one species, P. tenue, and one variant, P. tenue var. viride, both described as free-living ciliates thriving in oxygen depleted freshwater habitats of Europe. Here we report on this genus being discovered from subtropical freshwaters of Florida, USA. The Florida strain diverges from the P. tenue by being much larger, as well as having a far higher density of intracellular symbiotic green algae, resembling P. tenue var. viride. Unlike its European counterparts, the North American strain was observed to build a lorica, likely useful for protection and feeding; this has not been previously described for this genus. In contrast to P. tenue, the Florida strain does not have endosymbiotic purple bacteria. Despite large distances between sampling zones, the species is a close match at a morphological level to Pseudoblepharisma tenue var. viride. We provide the first 18S rRNA gene sequence for this species, allowing future investigations into the biogeography of this genus. As intensive sampling efforts continue to increase, cryptic microbial species will continue to be recorded from diverse freshwater habitats at a global scale.
Highlights
The cryptic biodiversity of an environment is an important component of microbial food webs and the ecosystems they help to support [1,2]
An approximately 400 μm freshwater ciliate that builds a protective case, or lorica, and contains dense green symbiotic algae was discovered at three Florida sites (Table 1, Figure 2)
Further taxonomic investigation allowed the identification of the Florida ciliate as being a species within the rarely recorded genus Pseudoblepharisma, such as the species Pseudoblepharisma tenue var. viride [10] due to the cell size and overall shape, along with the presence of dense symbiotic green algae (Figure 2)
Summary
The cryptic biodiversity of an environment is an important component of microbial food webs and the ecosystems they help to support [1,2]. Undersampling remains a persistent issue within microbial ecology [3,4], such that the true diversity of a particular site or region is difficult to quantify This results in many species remaining cryptic, especially when present in low numbers; they will remain cryptic, even when present in astronomically high numbers, if the habitat is not studied [5]. The genus was further described from the same geographical area, with descriptions of Pseudoblepharisma tenue presented [9]. This original work recorded the basic morphology, and it was later recorded ( in Germany) by Kreutz and Foissner (2006) [10], including the presence of intracellular algae and pink bacteria which were recognized not to be ingested but likely symbionts [8]. A detailed description of the German strain of P. tenue has recently been published [11], in which the use of single-cell genomics has allowed the identification of the symbionts, as well the determination of the draft genome for the ciliate
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