Morphological Studies on Five Trachelocercids from the Yellow Sea coast of China, with a Description of Tracheloraphis huangi spec. nov. (Ciliophora, Karyorelictea)

The morphology and infraciliature of five trachelocercid ciliates: Tracheloraphis huangi spec. nov., T. colubis (Kahl, 1933) comb. nov., T. phoenicopterus (Cohn, 1866) Dragesco, 1960, T. oligostriata (Raikov, 1962) Foissner and Dragesco, 1996 and Trachelocerca incaudata Kahl, 1933, isolated from the intertidal zone of a beach at Qingdao, China, were studied in live and protargol impregnated specimens. Tracheloraphis huangi spec. nov. was distinguished from its congeners mainly by its single nuclear group composed of 25–30 round macronuclei and 29–37 somatic kineties. The poorly known T. colubis is redescribed including for the first time information on its infraciliature. An improved diagnosis is also provided. In light of its infraciliature, T. colubis is transferred to Tracheloraphis from the genus Trachelocerca. Additional data on other three species is supplied based on the Qingdao populations

Morphological Studies on Five Trachelocercids from the Yellow Sea coast of China, with a Description of Tracheloraphis huangi spec. nov. (Ciliophora, Karyorelictea)

The morphology and infraciliature of five trachelocercid ciliates: Tracheloraphis huangi spec. nov., T. colubis (Kahl, 1933) comb. nov., T. phoenicopterus (Cohn, 1866) Dragesco, 1960, T. oligostriata (Raikov, 1962) Foissner and Dragesco, 1996 and Trachelocerca incaudata Kahl, 1933, isolated from the intertidal zone of a beach at Qingdao, China, were studied in live and protargol impregnated specimens. Tracheloraphis huangi spec. nov. was distinguished from its congeners mainly by its single nuclear group composed of 25–30 round macronuclei and 29–37 somatic kineties. The poorly known T. colubis is redescribed including for the first time information on its infraciliature. An improved diagnosis is also provided. In light of its infraciliature, T. colubis is transferred to Tracheloraphis from the genus Trachelocerca. Additional data on other three species is supplied based on the Qingdao populations

Data from: Novel predators reshape holozoan phylogeny and reveal the presence of a two-component signalling system in the ancestor of animals

Our understanding of the origin of animals has been transformed by characterizing their most closely related, unicellular sisters: the choanoflagellates, filastereans, and ichthyosporeans. Together with animals, these lineages make up the Holozoa [ 1, 2 ]. Many traits previously considered “animal specific” were subsequently found in other holozoans [ 3, 4 ], showing that they evolved before animals, although exactly when is currently uncertain because several key relationships remain unresolved [ 2, 5 ]. Here we report the morphology and transcriptome sequencing from three novel unicellular holozoans: Pigoraptor vietnamica and Pigoraptor chileana, which are related to filastereans, and Syssomonas multiformis, which forms a new lineage with Corallochytrium in phylogenomic analyses. All three species are predatory flagellates that feed on large eukaryotic prey, and all three also appear to exhibit complex life histories with several distinct stages, including multicellular clusters. Examination of genes associated with multicellularity in animals showed that the new filastereans contain a cell-adhesion gene repertoire similar to those of other species in this group. Syssomonas multiformis possessed a smaller complement overall but does encode genes absent from the earlier-branching ichthyosporeans. Analysis of the T-box transcription factor domain showed expansion of T-box transcription factors based on combination with a non-T-box domain (a receiver domain), which has not been described outside of vertebrates. This domain and other domains we identified in all unicellular holozoans are part of the two-component signaling system that has been lost in animals, suggesting the continued use of this system in the closest relatives of animals and emphasizing the importance of studying loss of function as well as gain in major evolutionary transitions

Species Diversity and Driving Factors of Benthic and Zooplanktonic Assemblages at Different Stages of Thermokarst Lake Development: A Case Study in the Lena River Delta (Middle Siberia)

Global climate change might result in permafrost thaw and the formation of thermokarst landscapes that release long-term carbon stocks as greenhouse into the atmosphere, thereby initiating a positive climate feedback. These processes are mediated by biological activity, including by microbes, vascular plants and animals, whereas the role of invertebrates in thermokarst ecosystems remains poorly understood. We investigated the diversity and assemblage structures of zooplankton (mainly Copepoda, Cladocera), microbenthos (testate amoebae) and meio- (Copepoda and Cladocera) and macrozoobenthos (mollusks, crustaceans, insects and annelids) from a range of water bodies representing different stages of thermokarst lake formation in the southern part of the Lena River Delta (Central Siberia). Altogether, 206 species of testate amoeba, mollusk, crustacean, insect and annelid taxa were identified. A total of 60 species of macrozoobenthos (mainly insects) and 62 species of testate amoebae were detected in the water bodies of the Lena River Delta for the first time. The species richness of zooplankton and meio- and macrozoobenthos was greater in the large thermokarst lakes than in the polygonal ponds due to the freezing of the latter in the winter. In contrast, the species richness of protists was higher in the polygonal ponds, which was related to the habitat preferences of testate amoebae. Fish grazing strongly affected the macrobenthos assemblages but not the smaller-sized organisms. Water acidity and temperature were the main environmental drivers of the assemblage structure of testate amoeba and microcrustacean. The species structure of the macroinvertebrate assemblages was significantly explained by water acidity, permafrost depth and size of the water area. It means that small size organisms with their short generation times are sensitive to more dynamic factors such as temperature and may serve as indicators of ecosystem changes due to global climate warming. In contrast, large size organisms are affected by driven factors that appear during thermokarst lakes formation and permafrost degradation

Novel Predators Reshape Holozoan Phylogeny and Reveal the Presence of a Two-Component Signaling System in the Ancestor of Animals

Our understanding of the origin of animals has been transformed by characterizing their most closely related, unicellular sisters: the choanoflagellates, filastereans, and ichthyosporeans. Together with animals, these lineages make up the Holozoa [1, 2]. Many traits previously considered “animal specific” were subsequently found in other holozoans [3, 4], showing that they evolved before animals, although exactly when is currently uncertain because several key relationships remain unresolved [2, 5]. Here we report the morphology and transcriptome sequencing from three novel unicellular holozoans: Pigoraptor vietnamica and Pigoraptor chileana, which are related to filastereans, and Syssomonas multiformis, which forms a new lineage with Corallochytrium in phylogenomic analyses. All three species are predatory flagellates that feed on large eukaryotic prey, and all three also appear to exhibit complex life histories with several distinct stages, including multicellular clusters. Examination of genes associated with multicellularity in animals showed that the new filastereans contain a cell-adhesion gene repertoire similar to those of other species in this group. Syssomonas multiformis possessed a smaller complement overall but does encode genes absent from the earlier-branching ichthyosporeans. Analysis of the T-box transcription factor domain showed expansion of T-box transcription factors based on combination with a non-T-box domain (a receiver domain), which has not been described outside of vertebrates. This domain and other domains we identified in all unicellular holozoans are part of the two-component signaling system that has been lost in animals, suggesting the continued use of this system in the closest relatives of animals and emphasizing the importance of studying loss of function as well as gain in major evolutionary transitions

Insights into the origin of metazoan multicellularity from predatory unicellular relatives of animals

Background: The origin of animals from their unicellular ancestor was one of the most important events in evolutionary history, but the nature and the order of events leading up to the emergence of multicellular animals are still highly uncertain. The diversity and biology of unicellular relatives of animals have strongly informed our understanding of the transition from single-celled organisms to the multicellular Metazoa. Here, we analyze the cellular structures and complex life cycles of the novel unicellular holozoans Pigoraptor and Syssomonas (Opisthokonta), and their implications for the origin of animals. Results: Syssomonas and Pigoraptor are characterized by complex life cycles with a variety of cell types including flagellates, amoeboflagellates, amoeboid non-flagellar cells, and spherical cysts. The life cycles also include the formation of multicellular aggregations and syncytium-like structures, and an unusual diet for single-celled opisthokonts (partial cell fusion and joint sucking of a large eukaryotic prey), all of which provide new insights into the origin of multicellularity in Metazoa. Several existing models explaining the origin of multicellular animals have been put forward, but these data are interestingly consistent with one, the “synzoospore hypothesis.” Conclusions: The feeding modes of the ancestral metazoan may have been more complex than previously thought, including not only bacterial prey, but also larger eukaryotic cells and organic structures. The ability to feed on large eukaryotic prey could have been a powerful trigger in the formation and development of both aggregative (e.g., joint feeding, which also implies signaling) and clonal (e.g., hypertrophic growth followed by palintomy) multicellular stages that played important roles in the emergence of multicellular animals.Science, Faculty ofNon UBCBotany, Department ofReviewedFacult

New Lineage of Microbial Predators Adds Complexity to Reconstructing the Evolutionary Origin of Animals

Highlights: • New predatory protist (Tunicaraptor) with unique morphology is related to animals • Tunicaraptor calls into question many of the well-accepted relationships in Holozoa • Tunicaraptor possesses a unique combination of “animal-specific” gene products • Eukaryovorous flagellates may represent a major share of unicellular animal relatives The origin of animals is one of the most intensely studied evolutionary events, and our understanding of this transition was greatly advanced by analyses of unicellular relatives of animals, which have shown many “animal-specific” genes actually arose in protistan ancestors long before the emergence of animals [1–3]. These genes have complex distributions, and the protists have diverse lifestyles, so understanding their evolutionary significance requires both a robust phylogeny of animal relatives and a detailed understanding of their biology [4, 5]. But discoveries of new animal-related lineages are rare and historically biased to bacteriovores and parasites. Here, we characterize the morphology and transcriptome content of a new animal-related lineage, predatory flagellate Tunicaraptor unikontum. Tunicaraptor is an extremely small (3–5 μm) and morphologically simple cell superficially resembling some fungal zoospores, but it survives by preying on other eukaryotes, possibly using a dedicated but transient “mouth,” which is unique for unicellular opisthokonts. The Tunicaraptor transcriptome encodes a full complement of flagellar genes and the flagella-associated calcium channel, which is only common to predatory animal relatives and missing in microbial parasites and grazers. Tunicaraptor also encodes several major classes of animal cell adhesion molecules, as well as transcription factors and homologs of proteins involved in neurodevelopment that have not been found in other animal-related lineages. Phylogenomics, including Tunicaraptor, challenges the existing framework used to reconstruct the evolution of animal-specific genes and emphasizes that the diversity of animal-related lineages may be better understood only once the smaller, more inconspicuous animal-related lineages are better studied