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[en] The immune system maintains the integrity of the organisms through a complex network of molecules, cells, and tissues that recognize internal or external antigenic substances to neutralized and eliminate them. The mechanisms of immune response have evolved in a modular fashion, where members of a given module interact strongly among them, but weakly with members of other modules, providing robustness and evolvability to the immune system. Ancestral modules are the raw material for the generation of new modules through evolution. Thus, the study of immune systems in basal metazoans such as cnidarians seeks to determine the basic tool kit from which the metazoans started to construct their immune systems. In addition, understanding the immune mechanisms in cnidarians contributes to decipher the etiopathology of coral diseases of infectious nature that are affecting coral reefs worldwide.
[en] Roles of various burrowing organisms in altering and generating infaunal habitat structure and in excavation and destruction of corals were studied. Burrowers and associated organisms were collected from corals and included polychaetes, sponges, bivalves, gastropods, sipunculans, crustaceans, echinoids, and nematodes. Sections of microatolls were analyzed for growth rates and sponge burrowing rates. Corals with a basal diameter of less than 6 cm suffered greater mortality due to bioerosion than larger heads
[en] In the late 1980s, as coral reefs throughout the Caribbean and elsewhere fell victim to a phenomenon known as bleaching, a few scientists stated that greenhouse warming is upon us and that the exquisitely sensitive corals, reacting to elevated water temperatures, are serving as biological sentinels. This stirred up so much concern that Congress assigned the National Science Foundation (NSF) to investigate the connection between coral bleaching and global warming. Late last month investigators at an NSF-sponsored meeting rendered their verdict. Following the Miami meeting, which brought together, for the first time, climatologists, oceanographers, and meteorologists with marine biologists, ecologists, and other reef experts, the participants issued a statement saying essentially that, yes, higher temperatures seem to be at least partly at fault but, no, greenhouse warming cannot be blamed
[en] Most of the volcanic mountains underwater more than thousand meters of height from its base on the ocean floor. These unique enclaves they have a great marine biodiversity because large number are concentrated in your environment nutrient that attracts one of faunas more rich and diverse on the planet. In some cases totally different to which species are they are in the surrounding area. However, only a few hundred of these submerged Giants -There are some 10,000 of the 100,000 that maps It is believed there are - have been able to study in detail due to visibility difficulties. (Author)
[en] It is stated that there have been many determinations of the acceleration of the Moon's mean longitude, mostly based on observations of occultations and on records of ancient eclipses. All these results have been expressed in Ephemeris Time and based on the annual apparent motion of the Sun about the Earth. Since 1955, however Atomic Time has come into use, based on the constant period of oscillation of the Cs atom. A difference of 25 seconds a century was found between the results using the two times, and it has been suggested that the most probable explanation is a decrease in the gravitational constant, G, by 8 parts in 1011 per year. Such a decrease would mean that the Earth is expanding somewhat, and there is some geological evidence supporting this. The authors tried to check this conclusion by a method involving the annual growth increments of specimens of coral. No evidence was found for any expansion of the Earth during the past 5 x 108 years. (U.K.)
[en] Marine sponges fulfill many critical functions to coral reefs. In turn, variations in the community structure of the poriferans may indicate changes in the environmental conditions of the ecosystems where they live. However, their study has been scarce in the Caribbean of Costa Rica, mainly in the ecological field. Therefore, the community structure of these organisms was evaluated in four reef patches (Perezoso, Pequeno, Coral Garden, and the 0.36) and it was determined whether it could be explained by sedimentation, substrate, and depth. Relative abundance (RA) and relative coverage (RC) for each species, sponge density, and diversity indices (species richness, Shannon heterogeneity, Pielous evenness, and Simpsons dominance) were calculated for each sampling site. Similarity between sites was compared to the relative abundance of sponges versus sedimentation, substrate, and depth. 13 new sponge records were found for the country. Perezoso had the highest sponge coverage (RC = 6.1 %) composed mainly by Cliona caribbaea (RC = 2.0 %) and with Niphates erecta as the dominant species (RA = 59.3 %). Species richness increased as site depth increased. Perezoso and Coral Garden showed the biggest similarity in terms of species abundance and shared N. erecta, Iotrochota birotulata and Scopalina ruetzleri as the most abundant species. These sites also shared the highest occurrence frequencies (40 %) of excavating sponges of the genus Siphonodictyon and the presence of the boring species C. caribbaea. Similarity between Perezoso and Coral Garden could be influenced to a greater extent by the high availability of calcareous pavement as a predominant substrate (48 < PC % < 67), which seems to favor the abundance of heterotrophic and generalist sponges, as well as that of excavating species and boring sponges.
[en] The immune system of animals is constituted by a large diversity of cells and molecules that collectively recognize, neutralize, and eliminate potential damaging agents, both biotic and abiotic. The study of the immune system has been traditionally biased towards some species with medical or economic importance, at the expense of the vast majority of species that constitute the animal diversity. With the current possibility of easily sequencing genomes and transcriptomes, there is an opportunity to study the immune systems of a wide variety of animal groups. One of these groups is the cnidarians, which include corals, anemones and jellyfishes, in which the study of the immune system has proved useful to understand two types of conflicts that are relevant for the survival of these organisms. The first one is the response of corals to diseases of infectious nature and the second relates to histocompatibility reactions, which mediate intraspecific competitions for habitable space. This article details the role of the cnidarian immune system to mediate the resolution of these two conflicts.
[en] Many sessile marine invertebrates have life cycles involving the development of larvae that settle on specific substrates to initiate metamorphosis to juvenile forms. Although is recognized that bacterial biofilms play a role in this process, the responsible chemical cues are beginning to be investigated. Here, we tested the role of substrate-specific bacteria biofilms and their Quorum Sensing Signaling Molecule (QSSM) extracts on chemotaxis and settlement of larvae from Hydractinia symbiolongicarpus, a hydroid that grows on gastropod shells occupied by hermit crabs. We isolated and taxonomically identified by 16S rDNA sequencing, 14 bacterial strains from shells having H. symbiolongicarpus. Three isolates, Shigella flexneri, Microbacterium liquefaciens, and Kocuria erythromyxa, were identified to produce QSSMs using biosensors detecting N-acyl-L-homoserine lactones. Multispecies biofilms and QSSM extracts from these bacteria showed a positive chemotactic effect on H. symbiolongicarpus larvae, a phenomenon not observed with mutant strains of E. coli and Chromobacterium violaceum that are unable to produce QSSMs. These biofilms and QSSMs extracts induced high rates of larval attachment, although only 1 % of the attached larvae metamorphosed to primary polyps, in contrast to 99 % of larvae incubated with CsCl, an artificial inductor of attachment and metamorphosis. These observations suggest that bacterial QSSMs participate in H. symbiolongicarpus substrate selection by inducing larval chemotaxis and attachment. Furthermore, they support the notion that settlement in cnidarians is decoupled into two processes, attachment to the substrate and metamorphosis to a primary polyp, where QSSMs likely participate in the former but not in the latter.