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.
Highlights
Paramecium is one of the most studied genera of ciliates
Strains from 30 populations of six morphospecies, namely representatives of the P. aurelia species complex, P. jenningsi, P. caudatum, P. multimicronucleatum, P. bursaria, and P. putrinum were introduced in the laboratory cultures
The greatest diversity was detected in the lakes, ponds, and streams of the Cantera Oriente reserve (Mexico City), where we isolated a number of strains of P. caudatum, P. multimicronucleatum, P. bursaria, and P. putrinum
Summary
Paramecium is one of the most studied genera of ciliates. At least fourteen morphological species of Paramecium are recognized as valid, and several more require reinvestigation [1,2,3]. Most of the morphological species include a number of genetically isolated groups, referred to as syngens. Syngens have been elevated to full species (the P. aurelia species complex, [4]) or could be described at least as genetic species due to the well-proved absolute reproductive barrier separating them, such as syngens in P. bursaria [5]. Several cryptic species of Paramecium have been reported [3], yet they are disputed as true species due to the failure to establish their laboratory culturing and to collect more specimens in nature. Some contested Paramecium species were documented only once from specific localities and were not subjected to thorough morphological, physiological or molecular description [1,6,7]
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