Temperature modulates compensatory responses to food limitation at metamorphosis in a marine invertebrate

Under climate change, increased temperatures combined with food limitation may be critical for species with complex life cycles, if high growth rates characterise the larval development. We studied the effect of increased temperature and food limitation on larval survival and on functional traits (developmental time, body mass, elemental composition, growth) at moulting and metamorphosis in the crab Carcinus maenas collected in the North Sea (Helgoland, Germany). We followed the approach of models of metamorphosis integrating responses of body mass and developmental time to increased temperature and food limitation. We also evaluated if body mass decreased with temperature (according to the temperature-size rule) and if developmental time followed an inverse exponential reduction (expected from some metabolic theories), as both trends are relevant for modelling effects of climate change on fitness and population connectivity. Larvae produced by four females during the reproductive period (i.e. spring-summer 2016) were reared separately from hatching to metamorphosis to the megalopa at two food conditions (ad libitum and low food availability), and at four temperatures covering the range experienced in the field (20°C). Survival and developmental rates were obtained by daily monitoring of the experiments. Biomass data (body mass and elemental composition) were obtained by sampling larvae at the zoea IV and megalopa stages and further processed with standard methods (see Torres & Giménez 2020 for details). We propose that integrative studies of traits at metamorphosis could be a basis to develop a mechanistic understanding of how species with complex life cycles will respond to climate change. Such models could eventually include hormonal and metabolic regulation of development as drivers of responses to environmental change

Anxiety and depression in patients aged 80 years and older following aortic valve therapy. A six‑month follow‑up study

Background Little is known about mental health following advanced cardiac procedures in the oldest patients. Aims To study changes in anxiety and depression from baseline to one- and six-month follow-up in older patients following transcatheter aortic valve implantation (TAVI) or surgical aortic valve replacement (SAVR). Methods Prospective cohort study of patients ≥ 80 years undergoing elective TAVI or SAVR in a tertiary university hospital. Anxiety and depression were assessed with the Hospital Anxiety and Depression Scale. Differences between TAVI/SAVR were analyzed using Welch’s t test or chi-squared. Changes over time and group differences were established with longitudinal models using generalized least squares. Results In 143 patients (83.5 ± 2.7 years), 46% (n = 65) received TAVI. Anxiety was identified in 11% of TAVI patients at baseline. One- and six-months later, percentages were 8% and 9%. In SAVR patients, 18% had baseline scores indicating anxiety. One and six-months later, percentages were 11% and 9%. Depression was identified in 15% of TAVI patients. One- and six-months later, percentages were 11% and 17%. At baseline, 11% of SAVR patients had scores indicating depression. One- and six-months after SAVR, percentages were 15% and 12%. Longitudinal analyses showed reductions (P < 0.001) in anxiety from baseline to one-month, and stable scores between one- and six-months for both treatment groups. There was no change over time for depression among treatment groups (P = 0.21). Discussion and conclusions SAVR or TAVI in patients ≥ 80 years was associated with anxiety reduction between baseline and follow-up. For depression, there was no evidence of change over time in either treatment group.publishedVersio

Line Defects in Molybdenum Disulfide Layers

Layered molecular materials and especially MoS2 are already accepted as promising candidates for nanoelectronics. In contrast to the bulk material, the observed electron mobility in single-layer MoS2 is unexpectedly low. Here we reveal the occurrence of intrinsic defects in MoS2 layers, known as inversion domains, where the layer changes its direction through a line defect. The line defects are observed experimentally by atomic resolution TEM. The structures were modeled and the stability and electronic properties of the defects were calculated using quantum-mechanical calculations based on the Density-Functional Tight-Binding method. The results of these calculations indicate the occurrence of new states within the band gap of the semiconducting MoS2. The most stable non-stoichiometric defect structures are observed experimentally, one of which contains metallic Mo-Mo bonds and another one bridging S atoms

Rapid Growth Reduces Cold Resistance: Evidence from Latitudinal Variation in Growth Rate, Cold Resistance and Stress Proteins

Background: Physiological costs of rapid growth may contribute to the observation that organisms typically grow at submaximal rates. Although, it has been hypothesized that faster growing individuals would do worse in dealing with suboptimal temperatures, this type of cost has never been explored empirically. Furthermore, the mechanistic basis of the physiological costs of rapid growth is largely unexplored. Methodology/Principal Finding: Larvae of the damselfly Ischnura elegans from two univoltine northern and two multivoltine southern populations were reared at three temperatures and after emergence given a cold shock. Cold resistance, measured by chill coma recovery times in the adult stage, was lower in the southern populations. The faster larval growth rates in the southern populations contributed to this latitudinal pattern in cold resistance. In accordance with their assumed role in cold resistance, Hsp70 levels were lower in the southern populations, and faster growing larvae had lower Hsp70 levels. Yet, individual variation in Hsp70 levels did not explain variation in cold resistance. Conclusions/Significance: We provide evidence for a novel cost of rapid growth: reduced cold resistance. Our results indicate that the reduced cold resistance in southern populations of animals that change voltinism along the latitudinal gradient may not entirely be explained by thermal selection per se but also by the costs of time constraint-induced higher growth rates. This also illustrates that stressors imposed in the larval stage may carry over and shape fitness in the adul

Climate-induced phenology shifts linked to range expansions in species with multiple reproductive cycles per year

Advances in phenology (the annual timing of species’ life-cycles) in response to climate change are generally viewed as bioindicators of climate change, but have not been considered as predictors of range expansions. Here, we show that phenology advances combine with the number of reproductive cycles per year (voltinism) to shape abundance and distribution trends in 130 species of British Lepidoptera, in response to ~0.5 °C spring-temperature warming between 1995 and 2014. Early adult emergence in warm years resulted in increased within- and between-year population growth for species with multiple reproductive cycles per year (n = 39 multivoltine species). By contrast, early emergence had neutral or negative consequences for species with a single annual reproductive cycle (n = 91 univoltine species), depending on habitat specialisation. We conclude that phenology advances facilitate polewards range expansions in species exhibiting plasticity for both phenology and voltinism, but may inhibit expansion by less flexible species

Variation in Size and Growth of the Great Scallop Pecten maximus along a Latitudinal Gradient

Understanding the relationship between growth and temperature will aid in the evaluation of thermal stress and threats to ectotherms in the context of anticipated climate changes. Most Pecten maximus scallops living at high latitudes in the northern hemisphere have a larger maximum body size than individuals further south, a common pattern among many ectotherms. We investigated differences in daily shell growth among scallop populations along the Northeast Atlantic coast from Spain to Norway. This study design allowed us to address precisely whether the asymptotic size observed along a latitudinal gradient, mainly defined by a temperature gradient, results from differences in annual or daily growth rates, or a difference in the length of the growing season. We found that low annual growth rates in northern populations are not due to low daily growth values, but to the smaller number of days available each year to achieve growth compared to the south. We documented a decrease in the annual number of growth days with age regardless of latitude. However, despite initially lower annual growth performances in terms of growing season length and growth rate, differences in asymptotic size as a function of latitude resulted from persistent annual growth performances in the north and sharp declines in the south. Our measurements of daily growth rates throughout life in a long-lived ectothermic species provide new insight into spatio-temporal variations in growth dynamics and growing season length that cannot be accounted for by classical growth models that only address asymptotic size and annual growth rate

What are the evolutionary constraints on larval growth in a trophically transmitted parasite?

For organisms with a complex life cycle, a large larval size is generally beneficial, but it may come at the expense of prolonged development. Individuals that grow fast may avoid this tradeoff and switch habitats at both a larger size and younger age. A fast growth rate itself can be costly, however, as it requires greater resource intake. For parasites, fast larval growth is assumed to increase the likelihood of host death before transmission to the next host occurs. Using the tapeworm Schistocephalus solidus in its copepod first intermediate host, I investigated potential constraints in the parasite’s larval life history. Fast-growing parasites developed infectivity earlier, indicating there is no functional tradeoff between size and developmental time. There was significant growth variation among full-sib worm families, but fast-growing sibships were not characterized by lower host survival or more predation-risky host behavior. Parental investment also had little effect on larval growth rates. The commonly assumed constraints on larval growth and development were not observed in this system, so it remains unclear what prevents worms from exploiting their intermediate hosts more aggressively

Mothers Matter Too: Benefits of Temperature Oviposition Preferences in Newts

The maternal manipulation hypothesis states that ectothermic females modify thermal conditions during embryonic development to benefit their offspring (anticipatory maternal effect). However, the recent theory suggests that the ultimate currency of an adaptive maternal effect is female fitness that can be maximized also by decreasing mean fitness of individual offspring. We evaluated benefits of temperature oviposition preferences in Alpine newts (Ichthyosaura [formerly Triturus] alpestris) by comparing the thermal sensitivity of maternal and offspring traits across a range of preferred oviposition temperatures (12, 17, and 22°C) and by manipulating the egg-predation risk during oviposition in a laboratory thermal gradient (12–22°C). All traits showed varying responses to oviposition temperatures. Embryonic developmental rates increased with oviposition temperature, whereas hatchling size and swimming capacity showed the opposite pattern. Maternal oviposition and egg-predation rates were highest at the intermediate temperature. In the thermal gradient, females oviposited at the same temperature despite the presence of caged egg-predators, water beetles (Agabus bipustulatus). We conclude that female newts prefer a particular temperature for egg-deposition to maximize their oviposition performance rather than offspring fitness. The evolution of advanced reproductive modes, such as prolonged egg-retention and viviparity, may require, among others, the transition from selfish temperature preferences for ovipositon to the anticipatory maternal effect

Defining the Boundaries of Development wih Plasticity

International audienceThe concept of plasticity has always been present in the history of developmental biology, both within the theory of epigenesis and within morphogenesis studies. However this tradition relies also upon a genetic conception of plasticity. Founded upon the concepts of "phenotypic plasticity" and "reaction norm," this genetic conception focuses on the array of possible phenotypic change in relation to diversified environments. Another concept of plasticity can be found in recent publications by some developmental biologists (Gilbert, West-Eberhard). I argue that these authors adopt a "broad conception of plasticity" that is closely related to a notion of development as something that is ongoing throughout an organism's lifecycle, and has no clear-cut boundaries. However, I suggest that given a narrow conception of plasticity, one can define temporal boundaries for development that are linked to specific features of the morphological process, which are different from behavioral and physiological processes