Abstract
We isolated a population of Oxytricha granulifera granuliferaFoissner and Adam (1983) from a hot spring in Iceland. The pure culture of this isolate was established at room temperature in the laboratory. This allowed for a detailed investigation, informed by integrated approaches, of the isolate’s morphology and morphogenesis, as well as molecular phylogeny. Results showed that the morphological and morphogenetic characteristics of the Iceland population are consistent with those of other populations. During the 3-year long period of laboratory cultivation, some abnormal individuals appeared repeatedly in the culture system. Interestingly, the morphological characteristics of these abnormal cells were rather stable, and were as follows: 1) body slender and elliptical-shaped; 2) remarkably shortened adoral zone and significantly reduced number of adoral membranelles; and 3) loss of undulating membranes. Resting cysts, binary fission and conjugate reproduction were not found in abnormal specimens. Although the morphology of abnormal individuals changed significantly, the sequences of the SSU rDNA of the normal and abnormal morphotypes were the same. Phylogenetic analyses showed that the two morphotypes clustered in a clade with other populations of O. granulifera granulifera.
Highlights
Ciliates are a large and diverse group of protozoa, which are distributed in a variety of habitats, including extreme environments (Foissner, 2016; Chen et al, 2019; Li et al, 2019; Luo et al, 2019; Shao et al, 2019, 2020; Bai et al, 2020; Wu et al, 2020)
Diagnosis of O. granulifera granulifera was as follows: cells 70–127 × 28–75 μm in vivo; adoral zone with 29–32 membranelles; paroral and endoral membranes in Oxytricha-pattern; the right marginal cirri row starting at the same level of the rightmost frontal cirrus; constantly five transverse cirri; rarely a sixth dorsal kinety; confined to terrestrial habitats (Foissner and Adam, 1983; Méndez-Sánchez et al, 2018)
Based on the general morphological features, the Iceland population conforms with the subspecies O. granulifera granulifera (Table 2)
Summary
Ciliates are a large and diverse group of protozoa, which are distributed in a variety of habitats, including extreme environments (Foissner, 2016; Chen et al, 2019; Li et al, 2019; Luo et al, 2019; Shao et al, 2019, 2020; Bai et al, 2020; Wu et al, 2020). Méndez-Sánchez et al (2018) subdivided Oxytricha granulifera into three subspecies, namely Oxytricha granulifera granulifera (Foissner and Adam, 1983), O. granulifera quadricirrata (Blatterer and Foissner, 1988), and O. granulifera chiapasensis (Méndez-Sánchez et al, 2018). This subdivision was mainly based on morphological characteristics, i.e., the patterns of undulating membrane, the numbers of dorsal kineties and transverse cirri. Diagnosis of O. granulifera granulifera was as follows: cells 70–127 × 28–75 μm in vivo; adoral zone with 29–32 membranelles; paroral and endoral membranes in Oxytricha-pattern; the right marginal cirri row starting at the same level of the rightmost frontal cirrus; constantly five transverse cirri; rarely a sixth dorsal kinety; confined to terrestrial habitats (Foissner and Adam, 1983; Méndez-Sánchez et al, 2018)
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