Dinoflagellate

Summary

The dinoflagellates (Greek δῖνος dinos "whirling" and Latin flagellum "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protist. Dinoflagellates are mostly marine plankton, but they also are common in freshwater habitats. Their populations vary with sea surface temperature, salinity, and depth. Many dinoflagellates are photosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey (phagotrophy and myzocytosis). In terms of number of species, dinoflagellates are one of the largest groups of marine eukaryotes, although substantially smaller than diatoms. Some species are endosymbionts of marine animals and play an important part in the biology of coral reefs. Other dinoflagellates are unpigmented predators on other protozoa, and a few forms are parasitic (for example, Oodinium and Pfiesteria). Some dinoflagellates produce resting stages, cal

Official source

https://en.wikipedia.org/wiki/Dinoflagellate

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While the early acquisition of Symbiodiniaceae algae into coral host tissues has been extensively studied, the dynamics of the migration of algal cells into rapidly expanding coral tissues still lacks a systematic study. This work examined two Red Sea branching coral species, Pocillopora damicornis and Stylophora pistillata, as they were growing and expanding their tissue laterally on glass slides (January-June, 2014; 450 assays; five colonies/species). We measured lateral tissue expansion rates and intratissue dinoflagellate migration rates. Tissue growth rates significantly differed between the two species (with Stylophora faster than Pocillopora), but not between genotypes within a species. Using a "flow-through coral chamber" under the microscope, the migration of dinoflagellates towards the peripheral edges of the expanding coral tissue was quantified. On a five-day timescale, the density of the endosymbiotic dinoflagellate cells, presenting within a 90 mu m region of expanding coral tissue (outer edge), increased by a factor of 23.6 for Pocillopora (from 1.2 x 10(4) cells cm(-2) to 2.4 x 10(5) cells cm(-2)) and by a factor of 6.8 for Stylophora (from 3.6 x 10(4) cells cm(-2) to 2.4 x 10(5) cells cm(-2)). The infection rates were fast (5.2 x 10(4) and 4.1 x 10(4) algal cells day-1 cm(-2), respectively), further providing evidence of an as yet unknown pathway of algal movement within coral host tissues.

2019

Montreux Co-Operative Culturelle. Une architecture de l'intelligence collective

Benoît Meugniot

L'architecte est pris au piège dans son système de pensées d'expert. Dès lors, le travail vise à introduire des outils conviviaux au workflow architectural pour faciliter l'intervention et la discussion des utilisateurs profanes, promulguant une architecture plus inclusive et durable. Le projet s'appuie sur les idéaux de l'association, « la 17ème », résidant à Montreux. Son idéologie, articulée autour de notions de participativité, d'inventivité et d'exploration, favorise un environnement propice à la vérification du processus « par et pour l'utilisateur ». L'expérience s'appuie sur le logiciel « Minecraft », base de nos interactions projectuelles. Ces dernières, collectées, nous permettent de comprendre les différentes itérations et l'improvisation architecturale qui mènent à la solution concertée. Situé dans un bâtiment désaffecté derrière le Montreux Palace, en aplomb sur le lac, le programme tente de répondre au besoin d'un « Incubateur culturel ». Ce choix questionne le rapport de la culture amatrice, qui nécessite des espaces d'expressions et de performances, avec celui d'une dynamique de logement coopératif. Ainsi, l'emphase sur l'intelligence collective rend intelligible, d'une part le fonctionnement du processus de création collective et d'autre part, solidifie les préceptes coopératifs.

2021

Regulation of Apoptotic Mediators Reveals Dynamic Responses to Thermal Stress in the Reef Building Coral Acropora millepora

Background: Mass coral bleaching is increasing in scale and frequency across the world's coral reefs and is being driven primarily by increased levels of thermal stress arising from global warming. In order to understand the impacts of projected climate change upon corals reefs, it is important to elucidate the underlying cellular mechanisms that operate during coral bleaching and subsequent mortality. In this respect, increased apoptotic cell death activity is an important cellular process that is associated with the breakdown of the mutualistic symbiosis between the cnidarian host and their dinoflagellate symbionts. Methodology/Principal Findings: The present study reports the impacts of different stressors (colchicine and heat stress) on three phases of apoptosis: (i) the potential initiation by differential expression of Bcl-2 members, (ii) the execution of apoptotic events by activation of caspase 3-like proteases and (iii) and finally, the cell disposal indicated by DNA fragmentation in the reef building coral Acropora millepora. In corals incubated with colchicine, an increase in caspase 3-like activity and DNA fragmentation was associated with a relative down-regulation of Bcl-2, suggesting that the initiation of apoptosis may be mediated by the suppression of an anti-apoptotic mechanism. In contrast, in the early steps of heat stress, the induction of caspase-dependent apoptosis was related to a relative up-regulation of Bcl-2 consecutively followed by a delayed decrease in apoptosis activity. Conclusions/Significance: In the light of these results, we propose a model of heat stress in coral hosts whereby increasing temperatures engage activation of caspase 3-dependent apoptosis in cells designated for termination, but also the onset of a delayed protective response involving overexpression of Bcl-2 in surviving cells. This mitigating response to thermal stress could conceivably be an important regulatory mechanism for cell survival in corals exposed to sudden environmental changes. © 2011 Pernice et al.

Public Library of Science2011

Regulation of Apoptotic Mediators Reveals Dynamic Responses to Thermal Stress in the Reef Building Coral Acropora millepora

Public Library of Science2011