Genetic differentiation between Arctic and Antarctic monothalamous foraminiferans

Monothalamous (single-chambered) foraminifers are a major component of the benthic meiofauna in high latitude regions. Several morphologically similar species are common in the Arctic and Antarctic. However, it is uncertain whether these morphospecies are genetically identical, or whether their accurate identification is compromised by a lack of distinctive morphological features. To determine the relationship between Arctic and Antarctic species, we have compared SSU rDNA sequences of specimens belonging to four morphotaxa: Micrometula, Psammophaga, Gloiogullmia, and one morphospecies Hippocrepinella hirudinea from western Svalbard (Arctic) and McMurdo Sound (Antarctic). Wherever possible, we include in our analyses representatives of these taxa from the deep Arctic and Southern Oceans, as well as from Northern European fjords. We found that in all cases, the bipolar populations were clearly distinct genetically. As expected, Arctic specimens were usually more closely related to those from Northern Europe than to their Antarctic representatives. The deep-sea specimens from Weddell Sea branched as a sister to the McMurdo Sound population, while those from the Arctic Ocean clustered with ones from Norwegian fjords. Our study has revealed a high number of cryptic species within each of the examined genera, and demonstrates the unexplored potential of monothalamous foraminifers for use as a tool to evaluate the origin and biogeography of polar meiofaun

Novel lineages of Southern Ocean deep-sea foraminifera revealed by environmental DNA sequencing

Diversity of deep-sea foraminifera is commonly studied based on analysis of agglutinated and calcareous tests preserved in the dried sediment samples. Soft-walled and agglutinated monothalamous (single-chambered) foraminifera are usually ignored because they are poorly preserved and difficult to identify. Moreover, the assemblage examined is usually limited to sediment size fraction larger than 63 or 125 mu m. To overcome these problems, we analysed the foraminiferal assemblage based on ribosomal DNA sequences amplified specifically from total DNA extracted from unsieved and fine fraction (<32 mu m of sediment samples from three sites in Southern Ocean. We obtained 392 sequences, representing 123 phylotypes of foraminifera. Over 90% of phylotypes (112) could not be assigned to any previously sequenced species or genera. Among these new phylotypes, 20 belong to the clade of multi-chambered calcareous Rotaliida and agglutinated Textulariida, while 94 branch among the radiation of monothalamous species. Many new phylotypes clustered together with other environmental foraminiferal sequences and sequences of unknown origin. Eight new lineages of environmental foraminiferal sequences (ENFOR 1-8) were distinguished. The morphology of species included in these novel lineages is unknown, but we can speculate that they are tiny, amoeboid protists present in the deep-sea sediments. Their diversity may be as high as that of better known large-sized foraminifera. Documenting this hidden component of deep-sea foraminiferal assemblages is a major challenge for the future. (C) 2011 Elsevier Ltd. All rights reserved

Making predictions in a changing world – inference, uncertainty and learning

To function effectively, brains need to make predictions about their environment based on past experience, i.e. they need to learn about their environment. The algorithms by which learning occurs are of interest to neuroscientists, both in their own right (because they exist in the brain) and as a tool to model participants' incomplete knowledge of task parameters and hence, to better understand their behaviour.This review focusses on a particular challenge for learning algorithms - how to match the rate at which they learn to the rate of change in the environment, so that they use as much observed data as possible whilst disregarding irrelevant, old observations. To do this algorithms must evaluate whether the environment is changing. We discuss the concepts of likelihood, priors and transition functions, and how these relate to change detection. We review expected and estimation uncertainty, and how these relate to change detection and learning rate. Finally, we consider the neural correlates of uncertainty and learning. We argue that the neural correlates of uncertainty bear a resemblance to neural systems that are active when agents actively explore their environments, suggesting that the mechanisms by which the rate of learning is set may be subject to top down control (in circumstances when agents actively seek new information) as well as bottom up control (by observations that imply change in the environment

Genetic differentiation between Arctic and Antarctic monothalamous foraminiferans

Monothalamous (single-chambered) foraminifers are a major component of the benthic meiofauna in high latitude regions. Several morphologically similar species are common in the Arctic and Antarctic. However, it is uncertain whether these morphospecies are genetically identical, or whether their accurate identification is compromised by a lack of distinctive morphological features. To determine the relationship between Arctic and Antarctic species, we have compared SSU rDNA sequences of specimens belonging to four morphotaxa: Micrometula, Psammophaga, Gloiogullmia, and one morphospecies Hippocrepinella hirudinea from western Svalbard (Arctic) and McMurdo Sound (Antarctic). Wherever possible, we include in our analyses representatives of these taxa from the deep Arctic and Southern Oceans, as well as from Northern European fjords. We found that in all cases, the bipolar populations were clearly distinct genetically. As expected, Arctic specimens were usually more closely related to those from Northern Europe than to their Antarctic representatives. The deep-sea specimens from Weddell Sea branched as a sister to the McMurdo Sound population, while those from the Arctic Ocean clustered with ones from Norwegian fjords. Our study has revealed a high number of cryptic species within each of the examined genera, and demonstrates the unexplored potential of monothalamous foraminifers for use as a tool to evaluate the origin and biogeography of polar meiofauna