Superorganisms of the protist kingdom : a new level of biological organization

The concept of superorganism has a mixed reputation in biology-for some it is a convenient way of discussing supra-organismal levels of organization, and for others, little more than a poetic metaphor. Here, I show that a considerable step forward in the understanding of superorganisms results from a thorough review of the supra-organismal levels of organization now known to exist among the “unicellular” protists. Limiting the discussion to protists has enormous advantages: their bodies are very well studied and relatively simple (as compared to humans or termites, two standard examples in most discussions about superorganisms), and they exhibit an enormous diversity of anatomies and lifestyles. This allows for unprecedented resolution in describing forms of supra-organismal organization. Here, four criteria are used to differentiate loose, incidental associations of hosts with their microbiota from “actual” superorganisms: (1) obligatory character, (2) specific spatial localization of microbiota, (3) presence of attachment structures and (4) signs of co-evolution in phylogenetic analyses. Three groups-that have never before been described in the philosophical literature-merit special attention: Symbiontida (also called Postgaardea), Oxymonadida and Parabasalia. Specifically, it is argued that in certain cases-for Bihospites bacati and Calkinsia aureus (symbiontids), Streblomastix strix (an oxymonad), Joenia annectens and Mixotricha paradoxa (parabasalids) and Kentrophoros (a ciliate)-it is fully appropriate to describe the whole protist-microbiota assocation as a single organism (“superorganism”) and its elements as “tissues” or, arguably, even “organs”. To account for this level of biological complexity, I propose the term “structured superorganism”

Molecular Phylogeny and Evolution of Parabasalia with Improved Taxon Sampling and New Protein Markers of Actin and Elongation Factor-1α

BACKGROUND: Inferring the evolutionary history of phylogenetically isolated, deep-branching groups of taxa-in particular determining the root-is often extraordinarily difficult because their close relatives are unavailable as suitable outgroups. One of these taxonomic groups is the phylum Parabasalia, which comprises morphologically diverse species of flagellated protists of ecological, medical, and evolutionary significance. Indeed, previous molecular phylogenetic analyses of members of this phylum have yielded conflicting and possibly erroneous inferences. Furthermore, many species of Parabasalia are symbionts in the gut of termites and cockroaches or parasites and therefore formidably difficult to cultivate, rendering available data insufficient. Increasing the numbers of examined taxa and informative characters (e.g., genes) is likely to produce more reliable inferences. PRINCIPAL FINDINGS: Actin and elongation factor-1α genes were identified newly from 22 species of termite-gut symbionts through careful manipulations and seven cultured species, which covered major lineages of Parabasalia. Their protein sequences were concatenated and analyzed with sequences of previously and newly identified glyceraldehyde-3-phosphate dehydrogenase and the small-subunit rRNA gene. This concatenated dataset provided more robust phylogenetic relationships among major groups of Parabasalia and a more plausible new root position than those previously reported. CONCLUSIONS/SIGNIFICANCE: We conclude that increasing the number of sampled taxa as well as the addition of new sequences greatly improves the accuracy and robustness of the phylogenetic inference. A morphologically simple cell is likely the ancient form in Parabasalia as opposed to a cell with elaborate flagellar and cytoskeletal structures, which was defined as most basal in previous inferences. Nevertheless, the evolution of Parabasalia is complex owing to several independent multiplication and simplification events in these structures. Therefore, systematics based solely on morphology does not reflect the evolutionary history of parabasalids

Planeacion regional: Cuatro ensayos basicos

SIGLETIB Hannover: RA 2043(23)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Das Aktivitaetensystem der Regionalwissenschaft Eine synoptische Darstellung des energetischen und stofflichen Bedingungszusammenhangs von Aktoren und Aktivitaeten

SIGLEBibliothek Weltwirtschaft Kiel C 151363 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman