Simón Bolívar University

About: Simón Bolívar University is a education organization based out in Caracas, Venezuela. It is known for research contribution in the topics: Population & Crystallization. The organization has 5912 authors who have published 8294 publications receiving 126152 citations.

Bacterial assemblages differ between compartments within the coral holobiont

Abstract: It is widely accepted that corals are associated with a diverse and host species-specific microbiota, but how they are organized within their hosts remains poorly understood. Previous sampling techniques (blasted coral tissues, coral swabs and milked mucus) may preferentially sample from different compartments such as mucus, tissue and skeleton, or amalgamate them, making comparisons and generalizations between studies difficult. This study characterized bacterial communities of corals with minimal mechanical disruption and contamination from water, air and sediments from three compartments: surface mucus layer (SML), coral tissue and coral skeleton. A novel apparatus (the ‘snot sucker’) was used to separate the SML from tissues and skeleton, and these three compartments were compared to swab samples and milked mucus along with adjacent environmental samples (water column and sediments). Bacterial 16S rRNA gene diversity was significantly different between the various coral compartments and environmental samples (PERMANOVA, F = 6.9, df = 8, P = 0.001), the only exceptions being the complete crushed coral samples and the coral skeleton, which were similar, because the skeleton represents a proportionally large volume and supports a relatively rich microflora. Milked mucus differed significantly from the SML collected with the ‘snot sucker’ and was contaminated with zooxanthellae, suggesting that it may originate at least partially from the gastrovascular cavity rather than the tissue surface. A common method of sampling the SML, surface swabs, produced a bacterial community profile distinct from the SML sampled using our novel apparatus and also showed contamination from coral tissues. Our results indicate that microbial communities are spatially structured within the coral holobiont, and methods used to describe these need to be standardized to allow comparisons between studies.

Expected‐posterior prior distributions for model selection

Abstract: SUMMARY We consider the problem of comparing parametric models using a Bayesian approach. A new method of developing prior distributions for the model parameters is presented, called the expected-posterior prior approach. The idea is to define the priors for all models from a common underlying predictive distribution, in such a way that the resulting priors are amenable to modern Markov chain Monte Carlo computational techniques. The approach has subjective Bayesian and default Bayesian implementations, and overcomes the most significant impediment to Bayesian model selection, that of ensuring that prior distributions for the various models are appropriately compatible.

A proposed unified nomenclature for the enamelled components of the molar teeth of the Cricetidae (Rodentia)

Abstract: The primitive topography of the enamelled surface of molar teeth of the Cricetidae is described as expressed in the fossil Cricetodontinae. Morphological variations in the molar structure of different subgroups among the Cricetidae are interpreted as derivations from this cricetodontine pattern. Eleven available naming systems for such components are surveyed, and a new unifying nomenclature is proposed, based on the Cope-Osborn cusp homologies for mammals. Names for enamel cusps, cuspules, styles, lophs, folds and islands are given, in an attempt to include in an overall general nomenclature the advantages of the most valuable, already available, nomenclatorial systems. The system purports to apply to all modifications of the cricetid crown molar pattern, and it claims to fulfil the need for a uniform nomenclature.