Keratella cochlearis is a rotifer. Keratella cochlearis has an oval lorica , a shell-like protective outer cuticle. At the anterior end are three pairs of spines. The central pair curve towards the ventral surface, the next pair diverge slightly and the outer pair converge.
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We'd like to understand how you use our websites in order to improve them. Register your interest. Rotifers are ubiquitous freshwater animals for which many complexes of cryptic species i.
Keratella cochlearis occurs globally and shows a wide phenotypic diversity indicating the potential presence of a species complex. We sampled lakes of the Trentino-South Tyrol region Italy and investigated mitochondrial genetic diversity in K. We sequenced the mitochondrial cytochrome c oxidase subunit I and used the generalised mixed Yule coalescent approach, Poisson tree process model and automatic barcode gap discovery to delimit mitochondrial groups, associated with putative evolutionary significant units ESUs.
Based on sequences, eight putative ESUs were indicated that could only partially be delimited by lorica morphology. Specifically, several morphological characteristics i. Furthermore, different putative ESUs of K.
We conclude that the high mitochondrial genetic diversity may be linked to tolerance of K. Biodiversity is currently under threat, and our perception of species loss is highly dependent on accurate estimates of species richness. However, estimates of species richness are often impaired by the occurrence of cryptic species i. Understanding how and why species occur is one of the fundamental aspects in ecology Gaston, Evidence on cryptic species diversity in rotifers, subclass Monogononta, is growing and challenges our understanding of rotifer biodiversity.
Obertegger et al. Keratella cochlearis Gosse, can be found in most freshwater lakes and ponds all over the world Green, Lauterborn described several morphotypes in K. Ahlstrom, ; Ruttner-Kolisko, ; Koste, The morphotypes described by Lauterborn encompass three series macracantha—typica—tecta , hispida , and irregularis and the group of robusta.
These morphological varieties of K. The areolation is present on half of the spine, and only the distal part is smooth and pointed. In lateral view, the spine points to left or right, and this is according to Lauterborn not an important feature. Along the series, the reduction of the posterior spine is notable until it disappears completely.
Lauterborn concluded that it is impossible to draw a line between the different morphotypes of the macracantha—typica—tecta series that only differ in size and posterior spine length PSL. The morphotypes of the hispida series can be considered the forma punctata of the tecta series. In addition, the basal margin is divided into small posterior carinal facets. Similar to the hispida series, the lorica has small pointed spinelets on the intersection of the areolation.
Characteristic for this group is the wide base of the posterior spine that is the elongation of the ventral part of the lorica, the hooked form of the anterior spines, and the slightly bended median ridge. Considering the wide morphological variability of Keratella morphotypes, Lauterborn already hypothesised a subspecies status of some morphotypes.
In fact, Ahlstrom and Eloranta erected the series irregularis and hispida to separate species. However, Hofmann , who did not recognise transitional forms between the morphotypes cochlearis , irregularis , and tecta as described by Lauterborn , questioned the validity of the Lauterborn cycles.
Especially, the presence and length of the posterior spine seems to be a morphological character whose suitability for discriminating species is questionable. In eutrophic habitats, K. Green, , ; Bielanska-Grajner, and in the presence of predators Conde-Porcuna et al. Water conditioned with predators i. Asplanchna spp. Derry et al. Furthermore, the various morphotypes of K. The wide tolerances to environmental conditions could also indicate that K.
Here, we identified mitochondrial DNA mtDNA groups and compared their lorica morphology in a complementary approach as recommended by Schlick-Steiner et al. Combining genetic information with other species-bound aspects such as species morphology and ecology or biochemistry of species habitat can result in a more robust species delimitation than when using genetic information alone Schlick-Steiner et al.
We hypothesised that K. In fact, in B. Closely related species might have similar niches according to the phylogenetic niche conservatism theory e. Thus, ESUs with their close phylogenetic relationship might be especially prone to competitive exclusion; however, co-occurrence of rotifer cryptic species has been reported Obertegger et al.
Thus, we also investigated temporal co-existence of putative ESUs of K. Both mesh sizes were small enough to effectively collect specimens of K. For the core lakes and Lake Caldonazzo July sample , single specimens of K. For the measured specimens, we also observed the main characteristics of the dorsal plate, important to discriminate morphotypes.
Measured specimens were subject to DNA extraction and sequencing. However, we could not obtain sequences for all measured specimens. Lorica drawing of K. Specimens of K. Cryptic species complexes in rotifers are often inferred based on the mitochondrial COI Suatoni et al.
Master mix proportions for one sample were We constructed the phylogenetic tree using a maximum likelihood ML and Bayesian inference BI approach. The selected model was implemented into PhyML 3. The posterior probability distribution was estimated with Markov chain Monte Carlo MCMC sampling, which was run for million generations, sampling every 10,th generation.
We used Tracer v1. We used TreeAnnotator v1. As outgroup sequences, we used B. Brachionidae as Keratella. We inferred mtDNA groups within K. For all methods, the outgroup was excluded prior to the analyses. We took the results of the GMYC approach as our baseline results because previously rotifer diversity was investigated by it for different species Obertegger et al. The GMYC approach is based on branching rates along an ultrametric tree here from BEAST to distinguish between species-level Yule, slower and population-level coalescent, faster branching rates.
Similarly to GMYC, PTP assumes that there are less intraspecific substitutions than interspecific substitutions because they have less time to accumulate. This method does not require an ultrametric tree and has been shown to match other methods of species delimitation in rotifers Tang et al.
It detects the gaps in the distribution of genetic pairwise distances. This method has been successfully used to delimit species of the meiofauna Tang et al. Here, all aligned K. We based our phylogenetic reconstructions and inference of mtDNA groups on a single mitochondrial gene COI , and this may gave a biased estimate on genetic diversity.
A higher evolutionary rate of COI with respect to other nuclear markers Tang et al. To assess the general validity of this correlation, we considered only those specimens that were measured and for which we obtained COI sequences. We performed a univariate statistical analysis and a multivariate ordination method to investigate if putative ESUs could be distinguished based on morphology.
We performed generalised least squares modelling to allow for dependence of measurements of ESUs coming from the same lake and checked homogeneity of residuals graphically. As multivariate ordination method, we performed non-metric multidimensional scaling NMDS. We, furthermore, performed a linear discriminant analysis LDA to investigate the discriminatory power of lorica morphology to separate ESUs. We tested for homogeneity of within-ESU covariance matrices.
We also investigated the correlation between phylogenetic and morphological diversity. Phylogenetic diversity was calculated as distance matrix based on the ultrametric tree, and morphological diversity as a distance matrix based on mean morphological values of ESUs.
The correlation between both distance matrices was investigated by a Mantel test. For statistical analyses, we used the library nlme Pinheiro et al. We obtained sequences of the COI gene of K. These sequences comprised 57 haplotypes. Phylogenetic relationships of the 57 COI haplotypes of K. Posterior probabilities from the Bayesian reconstruction and approximate likelihood ratio test support values from the maximum likelihood are shown below and above each branch , respectively.
Lakes were sorted according to increasing altitude elevation in the upper line , metres above sea level. The number of sequences for each haplotype per lake is given in each line. ESUs 3 and 7 co-occurred most often in different lakes. We obtained lorica measurements from individuals of K. Non-metric multidimensional scaling NMDS plot of all morphological variables.
We noted the presence of spinelets Fig. In addition, we observed small humps in the middle of the areolation section and the symmetrically situated lateral antenna Fig. SEM pictures of K. Our study indicated that eight putative ESUs of K. This diversity may be responsible for the apparent tolerance of K. The putative ESUs of K. The general good agreement of the various methods that we used to infer putative ESUs corroborated our results.
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Rotifer Symposium V pp Cite as. Vertical distribution of the rotifer Keratella cochlearis in stratified water columns of mesotrophic and eutrophic lakes during summer stagnation has been studied. Coexisting morphs K. The distribution of morph abundance and reproductive potential indicate that substitution of morphs within the vertical water column may be due to trophic conditions. The maximum population productivity is observed at the epi-metalimnion border. The maximum density zone lies below the zone of the highest productivity. Unable to display preview.
We'd like to understand how you use our websites in order to improve them. Register your interest. Rotifers are ubiquitous freshwater animals for which many complexes of cryptic species i. Keratella cochlearis occurs globally and shows a wide phenotypic diversity indicating the potential presence of a species complex. We sampled lakes of the Trentino-South Tyrol region Italy and investigated mitochondrial genetic diversity in K.
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