Computational models of heart pumping efficiencies based on contraction waves in spiral elastic bands

We present a framework for modeling biological pumping organs based on coupled spiral elastic band geometries and active wave-propagating excitation mechanisms. Two pumping mechanisms are considered in detail by way of example: one of a simple tube, which represents a embryonic fish heart and another more complicated structure with the potential to model the adult human heart. Through finite element modeling different elastic contractions are induced in the band. For each version the pumping efficiency is measured and the dynamics are evaluated. We show that by combining helical shapes of muscle bands with a contraction wave it is possible not only to achieve efficient pumping, but also to create desired dynamics of the structure. As a result we match the function of the model pumps and their dynamics to physiological observations.     

Exclusive male care despite extreme female promiscuity and low paternity in a marine snail

Males exhibit striking variation in the degree to which they invest in offspring, from merely provisioning females with sperm, to providing exclusive post-zygotic care. Paternity assurance is often invoked to explain this variation: the greater a male's confidence of paternity, the more he should be willing to provide care. Here, we report a striking exception to expectations based on paternity assurance: despite high levels of female promiscuity, males of a marine snail provide exclusive, and costly, care of offspring. Remarkably, genetic paternity analyses reveal cuckoldry in all broods, with fewer than 25% of offspring being sired by the caring male, although caring males sired proportionally more offspring in a given clutch than any other fathers did individually. This system presents the most extreme example of the coexistence of high levels of female promiscuity, low paternity, and costly male care, and emphasises the still unresolved roles of natural and sexual selection in the evolution of male parental care.     

For adults only? Supply-side ecology and the history of larval biology

When ecologists study organisms with multiphasic life cycles, they must often confront the problem of which phase to scrutinize. In principle, the dynamics and interactions of all stages could play a major role in the regulation of adult populations and species assemblages. In practice, however, the roles of larger and more sedentary phases - being easier to count and manipulate than motile propagules - have been emphasized. Nonetheless, several recent studies on the small, dispersing larval phase of marine invertebrate life cycles reach the conclusion that the spatial distribution and supply of propagules can control the distribution and abundance of populations of benthic adults. To some, the present emphasis on planktonic propagules amounts to a resurrection of ideas developed during a long and rich history of larval biology. To others, studies of demographic and ecological connections between larval and adult populations represent a substantial revision of ecological paradigms.     

Migratory movements of waterfowl in Central Asia and avian influenza emergence: sporadic transmission of H5N1 from east to west

Waterfowl in the genera Anas and Tadorna are suspected as vectors in the long‐distance transmission of highly pathogenic avian influenza H5N1. The former Soviet Republics of Central Asia are situated at an important migratory crossroads for these and other species of birds that bridges regions where the disease is prevalent. However, waterfowl movements through Central Asia are poorly quantified. In this study, historical data derived from over 80 years of bird ringing are combined with recent satellite tracking data to delineate migration routes, movement chronology and habitat use patterns of waterfowl in relation to H5N1 outbreak locations. Results confirm migratory linkage between breeding and moulting areas in northern Kazakhstan and southern Siberia, with non‐breeding areas in the Caspian, Black and eastern Mediterranean Sea basins, as well as with South Asia. However, unlike the situation in neighbouring regions, most notably western China, H5N1 outbreaks have not been recurrent in Central Asia after they were first reported during summer 2005 and spring 2006. These findings have implications in relation to potential sampling biases, species‐specific variation in migratory behaviour and continuing regional H5N1 transmission risks.     

Patterns of Mass Mortality among Rocky Shore Invertebrates across 100 km of Northeastern Pacific Coastline

Mass mortalities in natural populations, particularly those that leave few survivors over large spatial areas, may cause long-term ecological perturbations. Yet mass mortalities may remain undocumented or poorly described due to challenges in responding rapidly to unforeseen events, scarcity of baseline data, and difficulties in quantifying rare or patchily distributed species, especially in remote or marine systems. Better chronicling the geographic pattern and intensity of mass mortalities is especially critical in the face of global changes predicted to alter regional disturbance regimes. Here, we couple replicated post-mortality surveys with preceding long-term surveys and historical data to describe a rapid and severe mass mortality of rocky shore invertebrates along the north-central California coast of the northeastern Pacific Ocean. In late August 2011, formerly abundant intertidal populations of the purple sea urchin (Strongylocentrotus purpuratus, a well-known ecosystem engineer), and the predatory six-armed sea star (Leptasterias sp.) were functionally extirpated from ~100 km of coastline. Other invertebrates, including the gumboot chiton (Cryptochiton stelleri) the ochre sea star (Pisaster ochraceus), and subtidal populations of purple sea urchins also exhibited elevated mortality. The pattern and extent of mortality suggest the potential for long-term population, community, and ecosystem consequences, recovery from which may depend on the different dispersal abilities of the affected species.     

Limited potential for adaptation to climate change in a broadly distributed marine crustacean

The extent to which acclimation and genetic adaptation might buffer natural populations against climate change is largely unknown. Most models predicting biological responses to environmental change assume that species' climatic envelopes are homogeneous both in space and time. Although recent discussions have questioned this assumption, few empirical studies have characterized intraspecific patterns of genetic variation in traits directly related to environmental tolerance limits. We test the extent of such variation in the broadly distributed tidepool copepod Tigriopus californicus using laboratory rearing and selection experiments to quantify thermal tolerance and scope for adaptation in eight populations spanning more than 17° of latitude. Tigriopus californicus exhibit striking local adaptation to temperature, with less than 1 per cent of the total quantitative variance for thermal tolerance partitioned within populations. Moreover, heat-tolerant phenotypes observed in low-latitude populations cannot be achieved in high-latitude populations, either through acclimation or 10 generations of strong selection. Finally, in four populations there was no increase in thermal tolerance between generations 5 and 10 of selection, suggesting that standing variation had already been depleted. Thus, plasticity and adaptation appear to have limited capacity to buffer these isolated populations against further increases in temperature. Our results suggest that models assuming a uniform climatic envelope may greatly underestimate extinction risk in species with strong local adaptation.     

A few disconnected notes related to Levinthal paradox

We estimate that the longest protein chain capable of exhaustive sampling of all its conformations within a millisecond is shorter than 15 residues. This reinforces the understanding of Levinthal paradox which emerged in the last decade, namely, that cooperative (all-or-none) character of folding and unfolding transition is indicative of the sequences selected such that reliable folding does not require exhaustive conformation sampling. The opinion is formulated that the discussions of Levinthal paradox should now fly to the new spheres.     

Theory of the toroidal compact form of DNA in a polymer solution

A diagram of the states of single long rigid DNA macromolecule in solution of short flexible polymer was plotted. It has been shown that the compacting effect of the polymer solvent on DNA can be interpreted as hydrostatic pressure of coils gas on impermeable "walls" of the DNA globule. Conditions were found for the existence of compact (globular) states in the form of a sphere (stable for a very long DNA) and tore (for a relatively short one). Possibility of intramolecular liquidcrystalline orderliness of DNA segments in a globule was analyzed. Regions of realization of both regimes were studied: when compression with an added polymer was equalized by the forces of steric repulsion of DNA segments and when it was balanced by the elasticity of the DNA chain bendings.     

The sea as deathtrap: comment on a paper by miller and wiens

Miller & Wiens (2017) claim that low marine as compared with terrestrial diversity results from more frequent extinctions and insufficient time for diversification in marine clades. Their data on marine amniotes are unrepresentative of marine diversity, their analysis of clade dynamics is flawed, and they ignore previously proposed explanations for the diversity difference.