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1.
Sci Rep ; 13(1): 1242, 2023 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-36690681

RESUMO

Choanoflagellates are microeukaryotes that inhabit freshwater and marine environments and have long been regarded as the closest living relatives of Metazoa. Knowledge on the evolution of choanoflagellates is key for the understanding of the ancestry of animals, and although molecular clock evidence suggests the appearance of choanoflagellates by late Neoproterozoic, no specimens of choanoflagellates are known to occur in the fossil record. Here the first putative occurrence of choanoflagellates in sediments from the Cretaceous (Cenomanian-Turonian) is described by means of several cutting-edge petrographic techniques, and a discussion of its paleoenvironmental significance is performed. Furthermore, their placement in the organic matter classification systems is argued, with a placement in the Zoomorph Subgroup (Palynomorph Group) of the dispersed organic matter classification system being proposed. Regarding the ICCP System 1994, incorporation of choanoflagellates is, at a first glance, straightforward within the liptinite group, but the definition of a new maceral may be necessary to accommodate the genetic origin of these organisms. While modern choanoflagellates may bring light to the cellular foundations of animal origins, this discovery may provide an older term of comparison to their extant specimens and provide guidelines for possible identification of these organic components in other locations and ages throughout the geological record.


Assuntos
Coanoflagelados , Animais , Filogenia , Coanoflagelados/genética , Fósseis , Água Doce , Evolução Biológica
2.
Elife ; 112022 11 17.
Artigo em Inglês | MEDLINE | ID: mdl-36384644

RESUMO

In most eukaryotic organisms, cilia and flagella perform a variety of life-sustaining roles related to environmental sensing and motility. Cryo-electron microscopy has provided considerable insight into the morphology and function of flagellar structures, but studies have been limited to less than a dozen of the millions of known eukaryotic species. Ultrastructural information is particularly lacking for unicellular organisms in the Opisthokonta clade, leaving a sizeable gap in our understanding of flagella evolution between unicellular species and multicellular metazoans (animals). Choanoflagellates are important aquatic heterotrophs, uniquely positioned within the opisthokonts as the metazoans' closest living unicellular relatives. We performed cryo-focused ion beam milling and cryo-electron tomography on flagella from the choanoflagellate species Salpingoeca rosetta. We show that the axonemal dyneins, radial spokes, and central pair complex in S. rosetta more closely resemble metazoan structures than those of unicellular organisms from other suprakingdoms. In addition, we describe unique features of S. rosetta flagella, including microtubule holes, microtubule inner proteins, and the flagellar vane: a fine, net-like extension that has been notoriously difficult to visualize using other methods. Furthermore, we report barb-like structures of unknown function on the extracellular surface of the flagellar membrane. Together, our findings provide new insights into choanoflagellate biology and flagella evolution between unicellular and multicellular opisthokonts.


Assuntos
Coanoflagelados , Animais , Coanoflagelados/metabolismo , Microscopia Crioeletrônica , Flagelos , Axonema , Cílios
3.
Protist ; 173(6): 125923, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36370514

RESUMO

The deposition of silicified costal strips and lorica assembly in choanoflagellates is precisely linked to the cell cycle. A minority of species undergo nudiform division whereby a loricate cell divides to produce a naked daughter cell that deposits a set of costal strips and then assembles a lorica. Most species undergo tectiform division whereby a parent loricate cell produces a set of costal strips, divides and passes on the stored strips to a daughter cell that immediately assembles a lorica. Many phylogenetic analyses recover nudiform and tectiform species as sister-clades giving the impression that they are distinct evolutionary lineages. However, the tectiform species Stephanoeca diplocostata is capable of undergoing nudiform division and depositing costal strips and assembling a lorica with certain modifications in a nudiform manner. The recent discovery of a new genus, Enibas, comprising species with Stephanoeca-like loricae that undergo nudiform cell division and on phylogenetic analysis occur as a sister group to other nudiform species has drawn attention to whether there are also unique features in lorica construction. A range of Enibas loricae is illustrated and it appears that there are unique features which might be interpreted as being derived from a Stephanoeca-like ancestor.


Assuntos
Coanoflagelados , Dióxido de Silício , Filogenia , Divisão Celular
4.
Protist ; 173(6): 125924, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36327744

RESUMO

Lorica-bearing choanoflagellates belong to the order Acanthoecida, a taxon which has been consistently recovered as monophyletic in molecular phylogenies. Based upon differences in lorica development and morphology, as well as the presence or absence of a motile dispersal stage, species are labelled as either nudiform or tectiform. Whilst Acanthoecida is robustly resolved in molecular phylogenies, the placement of the root of the clade is less certain with two different positions identified in past studies. One recovered root has been placed between the nudiform family Acanthoecidae and the tectiform family Stephanoecidae. An alternative root placement falls within the tectiform species, recovering the monophyletic Acanthoecidae nested within a paraphyletic Stephanoecidae. Presented here is a 14-gene phylogeny, based upon nucleotide and amino acid sequences, which strongly supports tectiform paraphyly. The horizontal transfer of a ribosomal protein gene, from a possible SAR donor, into a subset of acanthoecid species provides further, independent, support for this root placement. Differing patterns of codon usage bias across the choanoflagellates are proposed as the cause of artefactual phylogenetic signals that lead to the recovery of tectiform monophyly.


Assuntos
Coanoflagelados , Coanoflagelados/genética , Filogenia
5.
Commun Biol ; 5(1): 954, 2022 09 12.
Artigo em Inglês | MEDLINE | ID: mdl-36097056

RESUMO

Choanoflagellates are primitive protozoa used as models for animal evolution. They express a large variety of multi-domain proteins contributing to adhesion and cell communication, thereby providing a rich repertoire of molecules for biotechnology. Adhesion often involves proteins adopting a ß-trefoil fold with carbohydrate-binding properties therefore classified as lectins. Sequence database screening with a dedicated method resulted in TrefLec, a database of 44714 ß-trefoil candidate lectins across 4497 species. TrefLec was searched for original domain combinations, which led to single out SaroL-1 in the choanoflagellate Salpingoeca rosetta, that contains both ß-trefoil and aerolysin-like pore-forming domains. Recombinant SaroL-1 is shown to bind galactose and derivatives, with a stronger affinity for cancer-related α-galactosylated epitopes such as the glycosphingolipid Gb3, when embedded in giant unilamellar vesicles or cell membranes. Crystal structures of complexes with Gb3 trisaccharide and GalNAc provided the basis for building a model of the oligomeric pore. Finally, recognition of the αGal epitope on glycolipids required for hemolysis of rabbit erythrocytes suggests that toxicity on cancer cells is achieved through carbohydrate-dependent pore-formation.


Assuntos
Coanoflagelados , Neoplasias , Animais , Carboidratos/química , Coanoflagelados/metabolismo , Glicoesfingolipídeos , Lectinas/química , Neoplasias/tratamento farmacológico , Coelhos
6.
Nat Microbiol ; 7(9): 1466-1479, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-35970961

RESUMO

Microbial predators such as choanoflagellates are key players in ocean food webs. Choanoflagellates, which are the closest unicellular relatives of animals, consume bacteria and also exhibit marked biological transitions triggered by bacterial compounds, yet their native microbiomes remain uncharacterized. Here we report the discovery of a ubiquitous, uncultured bacterial lineage we name Candidatus Comchoanobacterales ord. nov., related to the human pathogen Coxiella and physically associated with the uncultured marine choanoflagellate Bicosta minor. We analyse complete 'Comchoano' genomes acquired after sorting single Bicosta cells, finding signatures of obligate host-dependence, including reduction of pathways encoding glycolysis, membrane components, amino acids and B-vitamins. Comchoano encode the necessary apparatus to import energy and other compounds from the host, proteins for host-cell associations and a type IV secretion system closest to Coxiella's that is expressed in Pacific Ocean metatranscriptomes. Interactions between choanoflagellates and their microbiota could reshape the direction of energy and resource flow attributed to microbial predators, adding complexity and nuance to marine food webs.


Assuntos
Coanoflagelados , Microbiota , Animais , Bactérias , Humanos , Oceano Pacífico , Sistemas de Secreção Tipo IV
7.
Angew Chem Int Ed Engl ; 61(41): e202209105, 2022 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-35901418

RESUMO

The choanoflagellate Salpingoeca rosetta is an important model system to study the evolution of multicellularity. In this study we developed a new, modular, and scalable synthesis of sulfonolipid IOR-1A (six steps, 27 % overall yield), which acts as bacterial inhibitor of rosette formation in S. rosetta. The synthesis features a decarboxylative cross-coupling reaction of a sulfonic acid-containing tartaric acid derivative with alkyl zinc reagents. Synthesis of 15 modified IOR-1A derivatives, including fluorescent and photoaffinity-based probes, allowed quantification of IOR-1A, localization studies within S. rosetta cells, and evaluation of structure-activity relations. In a proof of concept study, an inhibitory bifunctional probe was employed in proteomic profiling studies, which allowed to deduce binding partners in bacteria and S. rosetta. These results showcase the power of synthetic chemistry to decipher the biochemical basis of cell differentiation processes within S. rosetta.


Assuntos
Coanoflagelados , Diferenciação Celular , Lipídeos , Proteômica , Ácidos Sulfônicos , Zinco
8.
Curr Biol ; 32(11): R530-R532, 2022 06 06.
Artigo em Inglês | MEDLINE | ID: mdl-35671729

RESUMO

Nitric oxide (NO), an ancient gaseous signaling molecule, regulates several physiological processes across the kingdoms. A new study describes how NO controls collective cell contractions in the closest animal relatives, the choanoflagellates, to switch from feeding to swimming away.


Assuntos
Coanoflagelados , Animais , Coanoflagelados/fisiologia , Óxido Nítrico , Natação
9.
Curr Biol ; 32(11): 2539-2547.e5, 2022 06 06.
Artigo em Inglês | MEDLINE | ID: mdl-35504284

RESUMO

Although signaling by the gaseous molecule nitric oxide (NO) regulates key physiological processes in animals, including contractility,1-3 immunity,4,5 development,6-9 and locomotion,10,11 the early evolution of animal NO signaling remains unclear. To reconstruct the role of NO in the animal stem lineage, we set out to study NO signaling in choanoflagellates, the closest living relatives of animals.12 In animals, NO produced by the nitric oxide synthase (NOS) canonically signals through cGMP by activating soluble guanylate cyclases (sGCs).13,14 We surveyed the distribution of the NO signaling pathway components across the diversity of choanoflagellates and found three species that express NOS (of either bacterial or eukaryotic origin), sGCs, and downstream genes previously shown to be involved in the NO/cGMP pathway. One of the species coexpressing sGCs and a bacterial-type NOS, Choanoeca flexa, forms multicellular sheets that undergo collective contractions controlled by cGMP.15 We found that treatment with NO induces cGMP synthesis and contraction in C. flexa. Biochemical assays show that NO directly binds C. flexa sGC1 and stimulates its cyclase activity. The NO/cGMP pathway acts independently from other inducers of C. flexa contraction, including mechanical stimuli and heat, but sGC activity is required for contractions induced by light-to-dark transitions. The output of NO signaling in C. flexa-contractions resulting in a switch from feeding to swimming-resembles the effect of NO in sponges1-3 and cnidarians,11,16,17 where it interrupts feeding and activates contractility. These data provide insights into the biology of the first animals and the evolution of NO signaling.


Assuntos
Coanoflagelados , Animais , Coanoflagelados/metabolismo , GMP Cíclico/metabolismo , Guanilato Ciclase/genética , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase/genética , Óxido Nítrico Sintase/metabolismo , Transdução de Sinais/fisiologia
10.
Curr Top Dev Biol ; 147: 73-91, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35337467

RESUMO

Choanoflagellates, the closest living relatives of animals, have the potential to reveal the genetic and cell biological foundations of complex multicellular development in animals. Here we describe the history of research on the choanoflagellate Salpingoeca rosetta. From its original isolation in 2000 to the establishment of CRISPR-mediated genome editing in 2020, S. rosetta provides an instructive case study in the establishment of a new model organism.


Assuntos
Coanoflagelados , Animais , Coanoflagelados/genética , Biologia do Desenvolvimento
11.
Mol Biol Evol ; 39(4)2022 04 11.
Artigo em Inglês | MEDLINE | ID: mdl-35277960

RESUMO

Neuropeptides are a diverse class of signaling molecules in metazoans. They occur in all animals with a nervous system and also in neuron-less placozoans. However, their origin has remained unclear because no neuropeptide shows deep homology across lineages, and none have been found in sponges. Here, we identify two neuropeptide precursors, phoenixin (PNX) and nesfatin, with broad evolutionary conservation. By database searches, sequence alignments, and gene-structure comparisons, we show that both precursors are present in bilaterians, cnidarians, ctenophores, and sponges. We also found PNX and a secreted nesfatin precursor homolog in the choanoflagellate Salpingoeca rosetta. PNX, in particular, is highly conserved, including its cleavage sites, suggesting that prohormone processing occurs also in choanoflagellates. In addition, based on phyletic patterns and negative pharmacological assays, we question the originally proposed GPR-173 (SREB3) as a PNX receptor. Our findings revealed that secreted neuropeptide homologs derived from longer precursors have premetazoan origins and thus evolved before neurons.


Assuntos
Coanoflagelados , Ctenóforos , Neuropeptídeos , Animais , Evolução Biológica , Coanoflagelados/genética , Sistema Nervoso , Neuropeptídeos/genética
12.
Eur J Protistol ; 83: 125865, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35124520

RESUMO

In the course of the last decades, several acanthoecid choanoflagellates have been assigned to the tectiform reproducing genus Stephanoeca based on lorica morphological comparability. The recent description of a Stephanoeca-like nudiform genus, Enibas Schiwitza, Arndt and Nitsche, 2019, has emphasized the possibility that some species assigned to Stephanoeca (based solely on lorica morphological features) might in the end have to be relegated to other genera. Stephanoeca urnula Thomsen, 1973, shows a striking morphological resemblance to E. thessalia Schiwitza and Nitsche, 2020. Also, the inability to document from microscopy any bundles of supernumerary costal strips in the collar region of this species, makes it an obvious Stephanoeca outcast candidate. We have revisited the S. urnula type locality and established this species in crude culture. A detailed SEM morphological analysis of cultured specimens, and a molecular analysis of the SSU and LSU rRNA, has unveiled its undisputed affiliation to the nudiform genus Enibas. Here, we redescribe S. urnula Thomsen, 1973 as E. urnula (Thomsen, 1973) comb. nov. Based on microscopical examinations of species of Stephanoeca and Enibas we have been able to pinpoint anterior lorica chamber construction details, that in the future renders possible a morphological distinction between the two genera.


Assuntos
Coanoflagelados , Filogenia , RNA Ribossômico
13.
Biomolecules ; 12(1)2022 01 06.
Artigo em Inglês | MEDLINE | ID: mdl-35053236

RESUMO

Enzyme rhodopsins, including cyclase opsins (Cyclops) and rhodopsin phosphodiesterases (RhoPDEs), were recently discovered in fungi, algae and protists. In contrast to the well-developed light-gated guanylyl/adenylyl cyclases as optogenetic tools, ideal light-regulated phosphodiesterases are still in demand. Here, we investigated and engineered the RhoPDEs from Salpingoeca rosetta, Choanoeca flexa and three other protists. All the RhoPDEs (fused with a cytosolic N-terminal YFP tag) can be expressed in Xenopus oocytes, except the AsRhoPDE that lacks the retinal-binding lysine residue in the last (8th) transmembrane helix. An N296K mutation of YFP::AsRhoPDE enabled its expression in oocytes, but this mutant still has no cGMP hydrolysis activity. Among the RhoPDEs tested, SrRhoPDE, CfRhoPDE1, 4 and MrRhoPDE exhibited light-enhanced cGMP hydrolysis activity. Engineering SrRhoPDE, we obtained two single point mutants, L623F and E657Q, in the C-terminal catalytic domain, which showed ~40 times decreased cGMP hydrolysis activity without affecting the light activation ratio. The molecular characterization and modification will aid in developing ideal light-regulated phosphodiesterase tools in the future.


Assuntos
Coanoflagelados/enzimologia , Luz , Diester Fosfórico Hidrolases/metabolismo , Proteínas de Protozoários/metabolismo , Animais , Coanoflagelados/genética , GMP Cíclico/genética , GMP Cíclico/metabolismo , Diester Fosfórico Hidrolases/genética , Domínios Proteicos , Proteínas de Protozoários/genética , Xenopus
14.
Chemistry ; 28(8): e202103883, 2022 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-34863043

RESUMO

We have analyzed the abundance of bacterial sulfonosphingolipids, including rosette-inducing factors (RIFs), in seven bacterial prey strains by using high-resolution tandem mass spectrometry (HRMS2 ) and molecular networking (MN) within the Global Natural Product Social Molecular Networking (GNPS) web platform. Six sulfonosphingolipids resembling RIFs were isolated and their structures were elucidated based on comparative MS and NMR studies. Here, we also report the first total synthesis of two RIF-2 diastereomers and one congener in 15 and eight synthetic steps, respectively. For the total synthesis of RIF-2 congeners, we employed a decarboxylative cross-coupling reaction to synthesize the necessary branched α-hydroxy fatty acids, and the Garner-aldehyde approach to generate the capnine base carrying three stereogenic centers. Bioactivity studies in the choanoflagellate Salpingoeca rosetta revealed that the rosette inducing activity of RIFs is inhibited dose dependently by the co-occurring sulfonosphingolipid sulfobacins D and F and that activity of RIFs is specific for isolates obtained from Algoriphagus.


Assuntos
Bacteroidetes , Coanoflagelados , Esfingolipídeos/química , Bactérias , Bacteroidetes/química , Coanoflagelados/química , Espectroscopia de Ressonância Magnética , Espectrometria de Massas em Tandem
15.
Commun Biol ; 4(1): 1404, 2021 12 16.
Artigo em Inglês | MEDLINE | ID: mdl-34916615

RESUMO

We provide a functional characterization of transcription factor NF-κB in protists and provide information about the evolution and diversification of this biologically important protein. We characterized NF-κB in two protists using phylogenetic, cellular, and biochemical techniques. NF-κB of the holozoan Capsaspora owczarzaki (Co) has an N-terminal DNA-binding domain and a C-terminal Ankyrin repeat (ANK) domain, and its DNA-binding specificity is more similar to metazoan NF-κB proteins than to Rel proteins. Removal of the ANK domain allows Co-NF-κB to enter the nucleus, bind DNA, and activate transcription. However, C-terminal processing of Co-NF-κB is not induced by IκB kinases in human cells. Overexpressed Co-NF-κB localizes to the cytoplasm in Co cells. Co-NF-κB mRNA and DNA-binding levels differ across three Capsaspora life stages. RNA-sequencing and GO analyses identify possible gene targets of Co-NF-κB. Three NF-κB-like proteins from the choanoflagellate Acanthoeca spectabilis (As) contain conserved Rel Homology domain sequences, but lack C-terminal ANK repeats. All three As-NF-κB proteins constitutively enter the nucleus of cells, but differ in their DNA-binding abilities, transcriptional activation activities, and dimerization properties. These results provide a basis for understanding the evolutionary origins of this key transcription factor and could have implications for the origins of regulated immunity in higher taxa.


Assuntos
Coanoflagelados/genética , Evolução Molecular , NF-kappa B/genética , Proteínas de Protozoários/genética , Fatores de Transcrição/genética , Coanoflagelados/metabolismo , NF-kappa B/metabolismo , Proteínas de Protozoários/metabolismo , Especificidade da Espécie , Fatores de Transcrição/metabolismo
16.
Elife ; 102021 11 03.
Artigo em Inglês | MEDLINE | ID: mdl-34730512

RESUMO

Animals have evolved unique repertoires of innate immune genes and pathways that provide their first line of defense against pathogens. To reconstruct the ancestry of animal innate immunity, we have developed the choanoflagellate Monosiga brevicollis, one of the closest living relatives of animals, as a model for studying mechanisms underlying pathogen recognition and immune response. We found that M. brevicollis is killed by exposure to Pseudomonas aeruginosa bacteria. Moreover, M. brevicollis expresses STING, which, in animals, activates innate immune pathways in response to cyclic dinucleotides during pathogen sensing. M. brevicollis STING increases the susceptibility of M. brevicollis to P. aeruginosa-induced cell death and is required for responding to the cyclic dinucleotide 2'3' cGAMP. Furthermore, similar to animals, autophagic signaling in M. brevicollis is induced by 2'3' cGAMP in a STING-dependent manner. This study provides evidence for a pre-animal role for STING in antibacterial immunity and establishes M. brevicollis as a model system for the study of immune responses.


Assuntos
Coanoflagelados/imunologia , Imunidade Inata , Proteínas de Membrana/metabolismo , Coanoflagelados/genética , Coanoflagelados/metabolismo , Coanoflagelados/microbiologia , GMP Cíclico/metabolismo , Proteínas de Membrana/genética , Infecções por Pseudomonas/imunologia , Pseudomonas aeruginosa , Transdução de Sinais
17.
Molecules ; 26(19)2021 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-34641578

RESUMO

Choanoflagellates are single-celled eukaryotes with complex signaling pathways. They are considered the closest non-metazoan ancestors to mammals and other metazoans and form multicellular-like states called rosettes. The choanoflagellate Monosiga brevicollis contains over 150 PDZ domains, an important peptide-binding domain in all three domains of life (Archaea, Bacteria, and Eukarya). Therefore, an understanding of PDZ domain signaling pathways in choanoflagellates may provide insight into the origins of multicellularity. PDZ domains recognize the C-terminus of target proteins and regulate signaling and trafficking pathways, as well as cellular adhesion. Here, we developed a computational software suite, Domain Analysis and Motif Matcher (DAMM), that analyzes peptide-binding cleft sequence identity as compared with human PDZ domains and that can be used in combination with literature searches of known human PDZ-interacting sequences to predict target specificity in choanoflagellate PDZ domains. We used this program, protein biochemistry, fluorescence polarization, and structural analyses to characterize the specificity of A9UPE9_MONBE, a M. brevicollis PDZ domain-containing protein with no homology to any metazoan protein, finding that its PDZ domain is most similar to those of the DLG family. We then identified two endogenous sequences that bind A9UPE9 PDZ with <100 µM affinity, a value commonly considered the threshold for cellular PDZ-peptide interactions. Taken together, this approach can be used to predict cellular targets of previously uncharacterized PDZ domains in choanoflagellates and other organisms. Our data contribute to investigations into choanoflagellate signaling and how it informs metazoan evolution.


Assuntos
Coanoflagelados/química , Coanoflagelados/metabolismo , Biologia Computacional/métodos , Domínios PDZ , Ligação Proteica , Sequência de Aminoácidos , Evolução Molecular , Humanos , Filogenia , Conformação Proteica , Transdução de Sinais , Software , Especificidade por Substrato
18.
Eur J Protistol ; 81: 125826, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34399128

RESUMO

The ambition to generate an overview of warm water loricate choanoflagellate biodiversity, based on a classic morphometric approach, is here completed by analyses of a range of tiny forms with anterior spines or projections and in most cases also a posterior pedicel. The warm water study complements previously obtained results from the more extensively studied temperate and polar regions of the world's oceans. It thus contributes to a significantly more balanced approach to global diversity patterns for these organisms. The current survey includes taxa such as Polyfibula elatensis, Parvicorbicula pedicellata, as well as a range of primarily undescribed and taxonomically challenging species, that are in an interim approach allocated to Coronoeca gen. nov. (C. kosmaniae sp. nov., C. conicella sp. nov., C. superpositus (Booth) comb. nov., C. marchantii sp. nov., C. tongiae sp. nov., and C. patongiensis sp. nov.). The analysis of warm water acanthoecid biodiversity has revealed in total 80 species from the six geographic regions sampled, corresponding to approximately 50% of all loricate species described. Nineteen species are previously undescribed forms. The Andaman Sea, Thailand, and West Australia are in a global context the most species-rich regions with 62 and 64 species respectively.


Assuntos
Coanoflagelados , Biodiversidade , Oceanos e Mares , Filogenia , Especificidade da Espécie , Água
19.
Eur J Protistol ; 80: 125791, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34087546

RESUMO

The loricate choanoflagellate genera Diaphanoeca Ellis and Crinolina Thomsen encompass a total of ten species. The majority of these are recorded from the warm water regions reported on here. A distinct morphological dichotomy characterizes the genus Diaphanoeca as currently circumscribed. The species distribute themselves within a 'D. grandis subgroup' and a 'D. pedicellata subgroup' distinguished on e.g., the position of the protoplast inside the lorica chamber and the elaboration of the anterior projections. We are, while awaiting in particular further molecular evidence, taking a conservative approach and abstain from dealing with the subgroup issue at the generic level. The examination of material from the warm water regions of the world's oceans has resulted in the description of D. sargassoensis sp.n., D. pseudoundulata sp.n., and D. throndsenii sp.n., and a thorough re-examination of D. undulata. Species of Crinolina share multiple features with in particular the D. grandis species subgroup. It is yet relevant, both in a morphological and molecular perspective, to retain the genus Crinolina which remains unambiguously defined based on the posteriorly open lorica. A high level of agreement is found when contrasting morphological and molecular based phylogenetic schemes.


Assuntos
Coanoflagelados/classificação , Água do Mar/parasitologia , Coanoflagelados/citologia , Temperatura Alta , Oceanos e Mares , Especificidade da Espécie
20.
Eur J Protistol ; 79: 125798, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33984646

RESUMO

In contrast to previous perspectives, hypersaline environments have been proven to harbour a variety of potentially highly adapted microorganisms, in particular unicellular eukaryotes. The isolated, hypersaline waterbodies in the Atacama Desert, Northern Chile are exposed to high UV radiation and deposition of toxic heavy metals, making them of great interest regarding studies on speciation and evolutionary processes. In the past two years, among a variety of other protist species, five new species of heterotrophic choanoflagellates were described and analysed from this area, showing an adaptation to a broad range of salinities. Morphological data alone does not allow for species delineation within craspedid species, additional molecular data is essential for modern taxonomy. In addition, molecular clock analyses pointed towards a strong selection force of the extreme environmental conditions. Within this study, we describe three additional craspedid choanoflagellate species, isolated from different aquatic environments. Phylogenetic analyses show two distinct clades of choanoflagellates from the Atacama, suggesting two independent invasions of at least two ancestral marine species, and, as indicated by our new data, a possible dispersal by Andean aquifers. The extended molecular clock analysis based on transcriptomic data of choanoflagellate strains from the Salar de Llamará, a hypersaline basin within the Central Depression of the Atacama Desert, reflects colonisation and divergence events which correspond to geological data of the paleohydrology.


Assuntos
Coanoflagelados , Filogenia , Adaptação Fisiológica , Biodiversidade , Chile , Coanoflagelados/classificação , Coanoflagelados/citologia , Coanoflagelados/genética , Clima Desértico , Salinidade , Especificidade da Espécie
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