*Article Paramecium* **Diversity and a New Member of the** *Paramecium aurelia* **Species Complex Described from Mexico**

#### **Alexey Potekhin 1,2,\* and Rosaura Mayén-Estrada 3**


http://zoobank.org/urn:lsid:zoobank.org:act:B5A24294-3165-40DA-A425-3AD2D47EB8E7 Received: 17 April 2020; Accepted: 13 May 2020; Published: 15 May 2020

**Abstract:** *Paramecium* (Ciliophora) is an ideal model organism to study the biogeography of protists. However, many regions of the world, such as Central America, are still neglected in understanding *Paramecium* diversity. We combined morphological and molecular approaches to identify paramecia isolated from more than 130 samples collected from different waterbodies in several states of Mexico. We found representatives of six *Paramecium* morphospecies, including the rare species *Paramecium jenningsi*, and *Paramecium putrinum*, which is the first report of this species in tropical regions. We also retrieved five species of the *Paramecium aurelia* complex, and describe one new member of the complex, *Paramecium quindecaurelia* n. sp., which appears to be a sister species of *Paramecium biaurelia*. We discuss criteria currently applied for differentiating between sibling species in *Paramecium*. Additionally, we detected diverse bacterial symbionts in some of the collected ciliates.

**Keywords:** biogeography; ciliates; *Paramecium quindecaurelia*; cytochrome C oxidase subunit I gene; sibling species; species concept in protists; bacterial symbionts
