Bloodlines: mammals, leeches, and conservation in southern Asia

Southern Asia is a biodiversity hotspot both for terrestrial mammals and for leeches. Many small-mammal groups are under-studied in this region, while other mammals are of known conservation concern. In addition to standard methods for surveying mammals, it has recently been demonstrated that residual bloodmeals within leeches can be sequenced to find mammals in a given area. While these invertebrate-parasite-derived DNA (iDNA) methods are promising, most of the leech species utilized for this type of survey remain unevaluated, notwithstanding that their diversity varies substantially. Here we examine approximately 750 individual leech specimens in the genus Haemadipsa across a large range in southern Asia (Bangladesh, Cambodia, and China), specifically reviewing the diversity of mammals they feed on and their own genetic structuring. Leeches were found to feed on a considerable variety of mammals, corroborating prior studies. Additionally, leeches were found to have fed both on bats and on birds, neither of which has previously been recorded with this method. The genetic structuring of the leeches themselves revealed 15 distinct clades of which only two precisely corresponded to previously characterized species, indicating that much work is needed to finalize classifications in this genus. Most importantly, with regards to mammal conservation, leeches in these clades appear to feed on a broad range of mammals

Time series are critical to understand microbial plankton diversity and ecology

International audienceHow diverse are marine planktonic protist communities? How much seasonality do they exhibit? For a very long time, these two old and challenging questions in the field of plankton ecology could be addressed only for large-size protist species, based on cell counting under the microscope. The recent application of molecular techniques, notably massive marker-gene amplicon sequencing approaches (metabarcoding), has allowed investigating with unprecedented level of resolution the small-sized (<20 µm) planktonic eukaryotes too. An amazing diversity of these tiny organisms has been unveiled but details about their temporal dynamics remain much more elusive. In a From the Cover article in this issue of Molecular Ecology, Giner et al. (2019) introduce a new Recurrence Index (RI) to specifically look for seasonality in time-series metabarcoding data. They inspected the temporal dynamics of all operational taxonomic units (OTUs) in a rich sequence data set of pico- and nanoplanktonic eukaryotes in samples collected monthly during 10 years. Although most OTUs did not show seasonality, some abundant ones did, which explains why some averaging methods can find seasonality at the less detailed level of whole planktonic communities. Not surprisingly, the very complex small-sized eukaryotic plankton communities are composed of organisms with miscellaneous temporal dynamics

The role of high-pressure flow-through experiments for evaluating the mechanical behaviour of gas hydrate-bearing soils

The role of high-pressure flow-through experiments for evaluating the mechanical behaviour of gas hydrate-bearing soil

Should the teaching of biological evolution include the origin of life?

The development of mainstream research on the origin of life as an outcome of Darwinian evolution is discussed. It is argued that prebiotic evolution and the origin of life should not be excluded from the syllabus and should be part of classes on biological evolution, and that the transition from non-living to living matter is best understood when seen as part of evolutionary biology. The wide acceptance of evolutionary approaches to the study of the emergence of life in European and Latin American countries is discussed

Survival and selection biases in early animal evolution and a source of systematic overestimation in molecular clocks

Important evolutionary events such as the Cambrian Explosion have inspired many attempts at explanation: why do they happen when they do? What shapes them, and why do they eventually come to an end? However, much less attention has been paid to the idea of a ‘null hypothesis’—that certain features of such diversifications arise simply through their statistical structure. Such statistical features also appear to influence our perception of the timing of these events. Here, we show in particular that study of unusually large clades leads to systematic overestimates of clade ages from some types of molecular clocks, and that the size of this effect may be enough to account for the puzzling mismatches seen between these molecular clocks and the fossil record. Our analysis of the fossil record of the late Ediacaran to Cambrian suggests that it is likely to be recording a true evolutionary radiation of the bilaterians at this time, and that explanations involving various sorts of cryptic origins for the bilaterians do not seem to be necessary

Sex and sexuality: An evolutionary view

In this article, I first offer a summary of Darwin’s main ideas, especially relating to sex, and explain how these have been elaborated by more recent evolutionary scholars. I then give an account of the historical divergence between psychoanalysis and classical Darwinian thought, and describe how the early psychoanalyst Sabina Spielrein tried to counter this by addressing some biological themes in her work. Following a review of some contemporary attempts to bring psychoanalysis and evolutionary thought into alignment with each other, I make some suggestions regarding a view of sex and sexuality that would be sound in evolutionary terms while also being helpful in psychoanalytic ones

Persistence of plastic debris and its colonization by bacterial communities after two decades on the abyssal seafloor

The fate of plastic debris entering the oceans is largely unconstrained. Currently, intensified research is devoted to the abiotic and microbial degradation of plastic floating near the ocean surface for an extended period of time. In contrast, the impacts of environmental conditions in the deep sea on polymer properties and rigidity are virtually unknown. Here, we present unique results of plastic items identified to have been introduced into deep-sea sediments at a water depth of 4150 m in the eastern equatorial Pacific Ocean more than two decades ago. The results, including optical, spectroscopic, physical and microbial analyses, clearly demonstrate that the bulk polymer materials show no apparent sign of physical or chemical degradation. Solely the polymer surface layers showed reduced hydrophobicity, presumably caused by microbial colonization. The bacterial community present on the plastic items differed significantly (p < 0.1%) from those of the adjacent natural environment by a dominant presence of groups requiring steep redox gradients (Mesorhizobium, Sulfurimonas) and a remarkable decrease in diversity. The establishment of chemical gradients across the polymer surfaces presumably caused these conditions. Our findings suggest that plastic is stable over extended times under deep-sea conditions and that prolonged deposition of polymer items at the seafloor may induce local oxygen depletion at the sediment-water interface

The Evolution and Development of Coloniality in Hydrozoans

Hydrozoan colonies display a variety of shapes and sizes including encrusting, upright and pelagic forms. Phylogenetic patterns reveal a complex evolutionary history of these distinct colony forms, as well as colony loss. Within a species, phenotypic variation in colonies as a response to changing environmental cues and resources has been documented. The patterns of branching of colony specific tissue, called stolons in encrusting colonies and stalks in upright colonies, are likely under the control of signaling mechanisms whose changing expression in evolution and development are responsible for the diversity of hydrozoan colony forms. Although mechanisms of polyp development have been well studied, little research has focused on colony development and patterning. In the few studies that investigated mechanisms governing colony patterning, the Wnt signaling pathway has been implicated. The diversity of colony form, evolutionary patterns and mechanisms of colony variation in Hydrozoa are reviewed here

Metabolically active microbial communities in marine sediment under high-CO2 and low-pH extremes

Sediment-hosting hydrothermal systems in the Okinawa Trough maintain a large amount of liquid, supercritical and hydrate phases of CO2 in the seabed. The emission of CO2 may critically impact the geochemical, geophysical and ecological characteristics of the deep-sea sedimentary environment. So far it remains unclear whether microbial communities that have been detected in such high-CO2 and low-pH habitats are metabolically active, and if so, what the biogeochemical and ecological consequences for the environment are. In this study, RNA-based molecular approaches and radioactive tracer-based respiration rate assays were combined to study the density, diversity and metabolic activity of microbial communities in CO2-seep sediment at the Yonaguni Knoll IV hydrothermal field of the southern Okinawa Trough. In general, the number of microbes decreased sharply with increasing sediment depth and CO2 concentration. Phylogenetic analyses of community structure using reverse-transcribed 16S ribosomal RNA showed that the active microbial community became less diverse with increasing sediment depth and CO2 concentration, indicating that microbial activity and community structure are sensitive to CO2 venting. Analyses of RNA-based pyrosequences and catalyzed reporter deposition-fluorescence in situ hybridization data revealed that members of the SEEP-SRB2 group within the Deltaproteobacteria and anaerobic methanotrophic archaea (ANME-2a and -2c) were confined to the top seafloor, and active archaea were not detected in deeper sediments (13–30 cm in depth) characterized by high CO2. Measurement of the potential sulfate reduction rate at pH conditions of 3–9 with and without methane in the headspace indicated that acidophilic sulfate reduction possibly occurs in the presence of methane, even at very low pH of 3. These results suggest that some members of the anaerobic methanotrophs and sulfate reducers can adapt to the CO2-seep sedimentary environment; however, CO2 and pH in the deep-sea sediment were found to severely impact the activity and structure of the microbial community