Global genetic homogeneity in the deep-sea foraminiferan Epistominella exigua (Rotaliida: Pseudoparrellidae)

Epistominella exigua is one of the most common deep-sea foraminiferal morphospecies and has a world-wide distribution. A recent molecular study revealed high genetic similarity between Arctic, Atlantic and Antarctic populations of this species. Here, we show that the small-subunit (SSU) and internal transcribed spacer (ITS) rDNA sequences of an E. exigua population from Pacific are almost identical to those reported previously from the other three oceans. This result confirms the genetic homogeneity of E. exigua, which contrasts with the prevalence of highly differentiated populations in planktonic and shallow-water benthic foraminiferans. We discuss special features of diversifications mechanisms in the deep sea that may be responsible for the lack of genetic differentiation and global distribution of some meiofauna species

Protist diversity and function in the dark ocean - challenging the paradigms of deep-sea ecology with special emphasis on foraminiferans and naked protists

The dark ocean and the underlying deep seafloor together represent the largest environment on this planet, comprising about 80% of the oceanic volume and covering more than two-thirds of the Earth's surface, as well as hosting a major part of the total biosphere. Emerging evidence suggests that these vast pelagic and benthic habitats play a major role in ocean biogeochemistry and represent an “untapped reservoir” of high genetic and metabolic microbial diversity. Due to its huge volume, the water column of the dark ocean is the largest reservoir of organic carbon in the biosphere and likely plays a major role in the global carbon budget. The dark ocean and the seafloor beneath it are also home to a largely enigmatic food web comprising little-known and sometimes spectacular organisms, mainly prokaryotes and protists. This review considers the globally important role of pelagic and benthic protists across all protistan size classes in the deep-sea realm, with a focus on their taxonomy, diversity, and physiological properties, including their role in deep microbial food webs. We argue that, given the important contribution that protists must make to deep-sea biodiversity and ecosystem processes, they should not be overlooked in biological studies of the deep ocean

Memorial to Martin David Brasier (1947–2014)

Martin Brasier, Professor of Palaeobiology at the University of Oxford and Adjunct Professor at Memorial University, Newfoundland until his retirement in 2013, died in a car accident on 16 December 2014. He is most famous for his outstanding studies of the early biosphere, from the first appearance of life on Earth to that of essentially ‘modern’ animals and protists in the Cambrian. The enormous influence he had in this field, and the respect that he inspired, are evident from the meeting held in his honour in Oxford on his retirement in 2013 (http://www.palaeocast.com/evolution-and-early-life/), and the award of the Lyell Medal by the Geological Society of London in 2014. However, his contributions to science extended in many directions, among them the emerging discipline of astrobiology where he applied his research in Precambrian palaeobiology to the search for life on Mars. His achievements in both these fields have been explored in other memorials (e.g. Wacey, 2015; McMahon & Cockell, 2015; McLoughlin et al., 2015). Here, we will emphasise his work on modern benthic ecosystems and particularly foraminifera. This has received less attention than other parts of his scientific output, although the study of microfossils, a topic on which he published a standard textbook (Brasier, 1980a; a second edition by Armstrong & Brasier, appeared in 2005), is a theme that underpinned his research. Incidentally, the book was written while Martin was in bed recovering from a slipped disc acquired while collecting large rock samples for microfossil papers on the Cambrian of

A new genus of xenophyophores (Foraminifera) from Japan Trench: morphological description, molecular phylogeny and elemental analysis

The deep-sea floor is inhabited by a number of unusual and enigmatic taxa, unknown in shallow waters. These include the xenophyophores, a group of giant protists that construct fragile agglutinated tests. Here, we describe Shinkaiya lindsayigen. et sp. nov., a new xenophyophore collected by the submersible Shinkai 6500 at a depth of 5435 m near the Japan Trench. The phylogenetic analysis performed on its complete small-subunit ribosomal DNA (SSU rDNA) sequence confirms that Sh. lindsayisp. nov. is a foraminiferan that is closely related to another xenophyophore, Syringammina corbicula Richardson, 2001, and to a monothalamous (single-chambered) foraminiferan Rhizammina algaeformis Brady, 1879. In terms of morphology, the new genus resembles Syringammina, but its test wall is thicker, softer, and more weakly cemented. Moreover, the SSU rDNA sequences of the two genera are highly divergent. Mass spectra analyses reveal unusually high concentrations of some elements, such as lead, uranium, and mercury. The granellare system (the cytoplasm and the organic sheath that encloses it) is apparently devoid of barite crystals, which are usually abundant as intracellular inclusions in xenophyophores, but is rich in mercury (with 12 times the concentration of mercury found in the surrounding sediment). Fecal pellets retained within a tubular system (stercomare) concentrate heavy metals, including lead and uranium (respectively, two and six times more than that of the sediment). Based on a comparison of the compositions of the agglutinated test wall, the granellare, the stercomare, and the surrounding sediment, we discuss the impact of xenophyophores on their habitat