Unraveling the non-senescence phenomenon in Hydra

Unlike other metazoans, Hydra does not experience the distinctive rise in mortality with age known as senescence, which results from an increasing imbalance between cell damage and cell repair. We propose that the Hydra controls damage accumulation mainly through damage-dependent cell selection and cell sloughing. We examine our hypothesis with a model that combines cellular damage with stem cell renewal, differentiation, and elimination. The Hydra individual can be seen as a large single pool of three types of stem cells with some features of differentiated cells. This large stem cell community prevents “cellular damage drift,” which is inevitable in complex conglomerate (differentiated) metazoans with numerous and generally isolated pools of stem cells. The process of cellular damage drift is based on changes in the distribution of damage among cells due to random events, and is thus similar to Muller׳s ratchet in asexual populations. Events in the model that are sources of randomness include budding, cellular death, and cellular damage and repair. Our results suggest that non-senescence is possible only in simple Hydra-like organisms which have a high proportion and number of stem cells, continuous cell divisions, an effective cell selection mechanism, and stem cells with the ability to undertake some roles of differentiated cells

Characeen-Wiederfunde im Bereich Teutschental - Röblingen - ein Nachtrag zur Roten Liste der Algen des Landes Sachsen-Anhalt

Der ehemalige Salzige See, eine natürliche Binnensalzstelle deren Geologie in HOYNINGEN-HUENE (1959) ausführlich beschrieben ist, wies offenbar bis zu seinem Verschwinden um 1890 eine reichhaltige Characeenflora auf. Belege dafür finden sich nicht nur in den regional benachbarten Herbarien der Universität Halle bzw. des Herbariums Haussknecht in Jena, auch in Kopenhagen, Stockholm, Helsinki und Montpellier sind Belege von z. B. Chara erinita (Synonym von Ch. canescens) aus dem Jahr 1853 anzutreffen, beschriftet von ALEXANDER BRAUN (1805-1877) mit "Am Mansfelder Salzsee in Thüringen". Vor allem der intensiven Sammeltätigkeit von A. BRAUN und O. BULNHEIM (1820-1865) verdanken wir eine gute Kenntnis über die ehemaligen Characeen-Vorkommen dieses Sees, der als bekannte Binnensalzstelle die Aufmerksamkeit vieler Botaniker auf sich zog und phykologisch als "locus elassieus" der Art Chara intermedia A. BRAUN in BRAUN, RABENHORST et STITZENBERGER 1859 auch eine bleibende internationale Bekanntheit erlangte (vgl. auch BLÜMEL 2004)

Worker lifespan is an adaptive trait during colony establishment in the long-lived ant <i>Lasius niger</i>

AbstractEusociality has been recognized as a strong driver of lifespan evolution. While queens show extraordinary lifespans of 20years and more, worker lifespan is short and variable. A recent comparative study found that in eusocial species with larger average colony sizes the disparities in the lifespans of the queen and the worker are also greater, which suggests that lifespan might be an evolved trait. Here, we tested whether the same pattern holds during colony establishment: as colonies grow larger, worker lifespan should decrease. We studied the mortality of lab-reared Lasius niger workers from colonies at two different developmental stages (small and intermediate-sized) in a common garden experiment. Workers were kept in artificial cohorts that differed only with respect to the stage of the colony they were born in. We found that the stage of the birth colony affected the body size and the survival probability of the workers. The workers that had emerged from early stage colonies were smaller and had lower mortality during the first 400days of their life than the workers born in colonies at a later stage. Our results suggest that early stage colonies produce small workers with an increased survival probability. These workers are gradually augmented by larger workers with a decreased survival probability that serve as a redundant workforce with easily replaceable individuals. We doubt that the observed differences in lifespan are driven by differences in body size. Rather, we suspect that physiological mechanisms are the basis for the observed differences in lifespan

Lung disease caused by ABCA3 mutations

Background Knowledge about the clinical spectrum of lung disease caused by variations in the ATP binding cassette subfamily A member 3 (ABCA3) gene is limited. Here we describe genotype-phenotype correlations in a European cohort. Methods We retrospectively analysed baseline and outcome characteristics of 40 patients with two disease-causing ABCA3 mutations collected between 2001 and 2015. Results Of 22 homozygous (15 male) and 18 compound heterozygous patients (3 male), 37 presented with neonatal respiratory distress syndrome as term babies. At follow-up, two major phenotypes are documented: patients with (1) early lethal mutations subdivided into (1a) dying within the first 6 months or (1b) before the age of 5 years, and (2) patients with prolonged survival into childhood, adolescence or adulthood. Patients with null/null mutations predicting complete ABCA3 deficiency died within the 1st weeks to months of life, while those with null/other or other/other mutations had a more variable presentation and outcome. Treatment with exogenous surfactant, systemic steroids, hydroxychloroquine and whole lung lavages had apparent but many times transient effects in individual subjects. Conclusions Overall long-term (>5 years) survival of subjects with two disease-causing ABCA3 mutations was <20%. Response to therapies needs to be ascertained in randomised controlled trials

Life span evolution in eusocial workers--a theoretical approach to understanding the effects of extrinsic mortality in a hierarchical system.

While the extraordinary life span of queens and division of labor in eusocial societies have been well studied, it is less clear which selective forces act on the short life span of workers. The disparity of life span between the queen and the workers is linked to a basic issue in sociobiology: How are the resources in a colony allocated between colony maintenance and reproduction? Resources for somatic maintenance of the colony can either be invested into quality or quantity of workers. Here, we present a theoretical optimization model that uses a hierarchical trade-off within insect colonies and extrinsic mortality to explain how different aging phenotypes could have evolved to keep resources secure in the colony. The model points to the significance of two factors. First, any investment that would generate a longer intrinsic life span for workers is lost if the individual dies from external causes while foraging. As a consequence, risky environments favor the evolution of workers with a shorter life span. Second, shorter-lived workers require less investment than long-lived ones, allowing the colony to allocate these resources to sexual reproduction or colony growth

Hierarchical trade-off model for eusocial species.

<p>Simplified hierarchical trade-off with a focus on workers for eusocial species, including two trade-offs at the colony and the individual levels. Arrows indicate resource flows. Resources are obtained by workers that do not reproduce and are allocated toward worker maintenance () and/or the colony (1−). At the colony level, resources that are not consumed by workers can be allocated to sexual reproduction () and/or maintenance (1−), such as the production of new workers or different levels of worker quality.</p

Model results under different levels of extrinsic mortality.

<p>The horizontal axis represents the values of extrinsic mortality used to run the model(;). A) and B) show the optimized parameters (, ,) from our model. In C)–F) the solid lines indicate the results when the optimal values of and , The dashed lines indicate results if the colony did not change the maintenance investments () or the switching time () with increasing extrinsic mortality ( = 0.38  = 84). A) Optimal investment into workers () decreases with increasing extrinsic risk. B) Denotes the switching time (), where the colony switches to the production of sexuals. C) The number of sexuals alive at the end of the season (maximized by finding optimal values for switching time () and maintenance investments into workers ()) decreases with increasing extrinsic mortality. D) Worker mortality combines intrinsic and extrinsic mortality (). The dashed line denotes the increase of extrinsic mortality. The difference between the dashed and solid lines shows the effect of the changing investment in worker maintenance. E) Worker life expectancy at the beginning of the season with different levels of extrinsic mortality. F) Worker life expectancy at switching time. At switching time, the worker population reaches its maximum. The difference in worker life span between e) and f) is due to the reduction of foraged resources caused by density dependency. Used parameters:  = 0.15,  = 0.005,  = 0.0024,  =  = 0–0.06.</p