Abstract
Amphileptus is one of the largest genera of pleurostomatid ciliates and its species diversity has been reported in various habitats all over the world. In the present work, we review its biodiversity based on data with reliable morphological records. Our work confirms that there are 50 valid Amphileptus species, some of which have a wide range of salinity adaptability and diverse lifestyles. This genus has a high diversity in China but this might be because of the relatively intensive sampling. Phylogenetic analyses based on SSU rDNA sequence data verify the non-monophyly of the genus Amphileptus. Furthermore, two new and one poorly known Amphileptus species, namely A. shenzhenensis sp. n., A. cocous sp. n., and A. multinucleatusWang, 1934, from coastal habitats of southern China were investigated using morphological and molecular phylogenetic methods. These three species are highly similar based on their contractile vacuoles and macronuclear nodules. However, they can be discriminated by details of their living morphology and somatic kineties. We also propose two new combinations, Amphileptus polymicronuclei (Li, 1990) comb. n. (original combination Hemiophrys polymicronucleiLi, 1990) and Amphileptus salimicus (Burkovsky, 1970b) comb. n. (original combination Hemiophrys salimicaBurkovsky, 1970b).
Highlights
IntroductionCiliated protozoa (ciliates) are a highly differentiated and diverse group of eukaryotic unicellular organisms which are common in a wide range of habitats where is sufficient water for their survival (Carey, 1992; Foissner, 1999; Wilbert and Song, 2005; Lynn, 2008; Foissner and Hawksworth, 2009; Song et al, 2009; Vd’acný and Foissner, 2012; Gao et al, 2016; Liu et al, 2017, 2019, Liu M.J. et al, 2020; Liu W.W. et al, 2020; Qu et al, 2018; Hu et al, 2019; Ma et al, 2019; Fan and Pan, 2020).Diversity of Amphileptus CiliatesPleurostomatida Schewiakoff, 1896 are a large order within the class Litostomatea Small and Lynn, 1981 and recent studies have revealed that its species diversity is much higher than previously anticipated (Lin et al, 2009; Vd’acný et al, 2011, 2014; Vd’acný, 2015; Wu et al, 2017; Hu et al, 2019)
Amphileptus is generally defined by the following combination of characters: (1) a single anterior suture formed by the right somatic kineties; (2) the presence of two rows of perioral kineties [three rows were detected in a single species, A. yuianus, by Lin et al (2005b); molecular data are needed to confirm its generic classification]; (3) extrusomes not distributed along the dorsal margin, and (4) the absence of a spoon-shaped apex in the anterior end of the body (Foissner, 1977, 1984; Song and Wilbert, 1989; Foissner and Leipe, 1995; Lin et al, 2007a)
Species no longer assigned to the genus Amphileptus, and species of Amphileptus originally assigned to other genera, are listed in Table 2 along with their current names and taxonomic status
Summary
Ciliated protozoa (ciliates) are a highly differentiated and diverse group of eukaryotic unicellular organisms which are common in a wide range of habitats where is sufficient water for their survival (Carey, 1992; Foissner, 1999; Wilbert and Song, 2005; Lynn, 2008; Foissner and Hawksworth, 2009; Song et al, 2009; Vd’acný and Foissner, 2012; Gao et al, 2016; Liu et al, 2017, 2019, Liu M.J. et al, 2020; Liu W.W. et al, 2020; Qu et al, 2018; Hu et al, 2019; Ma et al, 2019; Fan and Pan, 2020).Diversity of Amphileptus CiliatesPleurostomatida Schewiakoff, 1896 are a large order within the class Litostomatea Small and Lynn, 1981 and recent studies have revealed that its species diversity is much higher than previously anticipated (Lin et al, 2009; Vd’acný et al, 2011, 2014; Vd’acný, 2015; Wu et al, 2017; Hu et al, 2019). Amphileptus Ehrenberg, 1830 is the oldest genus within the order Pleurostomatida and comprises over 60 nominal species reported from marine (Wang, 1934; Dragesco, 1965; Song, 1991; Carey, 1992; Lin et al, 2005a,b, 2007a), brackish waters (Pan et al, 2014; Wu et al, 2014, 2015b), and freshwater habitats (Wang and Nie, 1933; Wang, 1940; Curds, 1982; Song and Wilbert, 1989; Li, 1990) all over the world. Since the ciliary pattern as revealed by silver staining is of great importance for species identification, there is an urgent need to redescribe those that are currently known only from in vivo observation
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