Placozoa: at least two

Wolf, Matthias; Selig, Christian; Müller, Tobias; Philippi, Nicole; Dandekar, Thomas; Schultz, Jörg

doi:10.2478/s11756-007-0143-z

Cited by 11 publications

(7 citation statements)

References 23 publications

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“…The CM furthermore supports the phylogenetic split between Trichoplax (clade I; note: no data available for clade II) and the new placozoan genus Hoilungia (clades III–VII), as shown in the dendrogram on top of the heatmap. These clades are consistent with those recovered from analyses of the mitochondrial ribosomal large subunit (16S) [ 5 ] and compensatory base changes in the ITS2 [ 55 ]. Data underlying this figure can be found at https://bitbucket.org/molpalmuc/hoilungia-genome/src/master/reproductive_isolation/ .…”

Section: Resultssupporting

confidence: 83%

“…A clear split of the Placozoa in the molecular groups “A” and “B” was previously shown by the rearrangement pattern of mitochondrial genomes [ 61 ] and compensatory base changes in the internal transcribed spacer 2 (ITS2) [ 55 ]. The conspecificity analysis, the high amount of genomic rearrangement, and the large-scale independent gene duplication history, as well as the genetic distances in six independent datasets, strongly support this split ( Fig 3 ).…”

Section: Resultsmentioning

confidence: 99%

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Comparative genomics and the nature of placozoan species

et al. 2018

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Placozoans are a phylum of nonbilaterian marine animals currently represented by a single described species, Trichoplax adhaerens, Schulze 1883. Placozoans arguably show the simplest animal morphology, which is identical among isolates collected worldwide, despite an apparently sizeable genetic diversity within the phylum. Here, we use a comparative genomics approach for a deeper appreciation of the structure and causes of the deeply diverging lineages in the Placozoa. We generated a high-quality draft genome of the genetic lineage H13 isolated from Hong Kong and compared it to the distantly related T. adhaerens. We uncovered substantial structural differences between the two genomes that point to a deep genomic separation and provide support that adaptation by gene duplication is likely a crucial mechanism in placozoan speciation. We further provide genetic evidence for reproductively isolated species and suggest a genus-level difference of H13 to T. adhaerens, justifying the designation of H13 as a new species, Hoilungia hongkongensis nov. gen., nov. spec., now the second described placozoan species and the first in a new genus. Our multilevel comparative genomics approach is, therefore, likely to prove valuable for species distinctions in other cryptic microscopic animal groups that lack diagnostic morphological characters, such as some nematodes, copepods, rotifers, or mites.

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Section: Resultssupporting

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Comparative genomics and the nature of placozoan species

et al. 2018

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“…We provided an emendation of the genus including taxa which form mucilaginous envelopes and colonies. (krienitz et al 2004müller et al 2007;WolF et al 2007;ruhl et al 2009). As our study showed, the 5.8S and ITS-2 region works well for Chlorella as a tool for species delineation.…”

Section: Discussionmentioning

confidence: 99%

Taxonomic reassessment of the genus Chlorella (Trebouxiophyceae) using molecular signatures (barcodes), including description of seven new species.

Böck¹,

Krienitz²,

Pröschold³

2011

Fottea

127

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Abstract:After the description of Chlorella vulgaris by Beijerinck, 120 years ago, members of the genus Chlorella belong to the best studied green algae worldwide. However, numerous open questions remained regarding their systematics. Recent molecular studies showed the polyphyly of the genus within the Chlorophyceae and Trebouxiophyceae. Chlorella-species were traditionally characterized by spherical to oval cell shape, solitary lifeform and the absence of mucilaginous envelopes. The challenge in the past was how to distinguish species due to their high phylogenetic diversity combined with a limited amount of morphological characters. Using a polyphasic approach of SSU-and ITS rDNA phylogeny, secondary structure of the ITS and light microscopic observations, we were able to detect six lineages with Dictyosphaerium-like strains in close relationship to C. vulgaris, here described or combined newly as C. coloniales sp. nov., C. pituita sp. nov., C. pulchelloides sp. nov., C. singularis sp. nov., C. elongata comb. nov. and C. chlorelloides comb. nov. Furthermore, three new species without mucilage were described as C. lewinii sp. nov., C. rotunda sp. nov. and C. volutis sp. nov. Using the 5.8S rRNA and part of the ITS-2 as molecular signature (barcode), we were able to distinguish not only the five already known species of Chlorella, C. vulgaris, C. sorokiniana, C. heliozoae, C. lobophora and C. variabilis but the seven new species and two new combinations as well. CBCs and hemi-CBCs within the secondary structure of the ITS-2 confirmed the separation of the species. Our study led to a new understanding of the evolution of morphology within the genus Chlorella and to an emendation of the generic description.

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“…Secondary structure data can be used to generate reliable alignments between divergent ITS2 sequences that cannot be aligned based on sequence data alone (Schultz et al, 2005;Seibel et al, 2008;Siebert & Backofen, 2005;Wolf et al, 2007), resulting in more robust phylogenetic inferences based on ITS data. It has also been shown recently that differences of as little as a single compensatory base change in the secondary structure pairing of the ITS2 region is strongly correlated with sexual incompatibility and is, therefore, indicative of distinct ''biological species'' within a system (Coleman, 2009;Müller et al, 2007;Wolf et al, 2005).…”

Section: Biogeographical Distributionmentioning

confidence: 99%

Gynichthys diakidnus n. g., n. sp. (Digenea: Cryptogonimidae) from the grunt Plectorhinchus gibbosus (Lacépède, 1802) (Perciformes: Haemulidae) off the Great Barrier Reef, Australia

Miller

Cribb

2009

Syst Parasitol

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Gynichthys diakidnus n. g., n. sp. (Digenea: Cryptogonimidae) is described from the fish Plectorhinchus gibbosus (Lacépède) (Perciformes: Haemulidae) off Heron and Lizard Islands on the Great Barrier Reef, Australia. The monotypic Gynichthys n. g. is distinguished from all other cryptogonimid genera by the combination of a fusiform body, the lack of oral spines, a forebody that occupies approximately half or more of the body length, a deeply lobed ovary, opposite to slightly oblique testes, a seminal vesicle that is confined mainly in the forebody and the presence of multiple gonotyls in the form of two small slightly muscular pores or pseudosucker-like structures in the mid-line well anterior to the ventral sucker. Bayesian inference analysis of LSU rDNA data revealed that G. diakidnus n. sp. grouped relatively distant to species of the cryptogonimid genus Oligogonotylus Watson, 1976, which also have multiple gonotyls, suggesting that the presence of multiple gonotyls is homoplasious and has thus at least evolved twice in the family. The secondary structure of the internal transcribed spacer 2 (ITS2) rDNA region was inferred for G. diakidnus using minimum free energy and homology modelling algorithms. A four helix model was inferred with helices I and IV being relatively short (<30 nucleotides) and helix three being the longest; this structure is homologous with that observed for other digeneans and eukaryotes in general.

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Placozoa: at least two

Cited by 11 publications

References 23 publications

Comparative genomics and the nature of placozoan species

Comparative genomics and the nature of placozoan species

Taxonomic reassessment of the genus Chlorella (Trebouxiophyceae) using molecular signatures (barcodes), including description of seven new species.

Gynichthys diakidnus n. g., n. sp. (Digenea: Cryptogonimidae) from the grunt Plectorhinchus gibbosus (Lacépède, 1802) (Perciformes: Haemulidae) off the Great Barrier Reef, Australia

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