Ecogeography of group size suggests differences in drivers of sociality among cooperatively breeding fairywrens

Cooperatively breeding species exhibit a range of social behaviors associated with different costs and benefits to group-living, often in association with different environmental conditions. For example, species in which collective-care of offspring reduces the cost of reproduction are more common in harsh environments (true cooperative breeding), while species that collectively defend resources are present in benign environments (family-living). Here, we examine whether environment also shapes sociality within cooperatively-breeding species. We illustrate that Purple-backed Fairywrens, which primarily gain intrinsic, or collective-care benefits, have larger groups in hot, dry environments and smaller groups in cool, wet environments, whereas Superb Fairywrens which primarily gain extrinsic, or resource defense benefits, exhibit the opposite trend. We suggest differences in the costs and benefits of sociality contribute to these opposing ecogeographic patterns, demonstrating that comparisons of intraspecific patterns of social variation across species can provide insight into how ecology shapes transitions between social systems.

Telomerase as a possible key to bypass the cost of reproduction effect

Telomerase activity and telomere restoration in certain somatic cells of human adults maintain the proliferative capacity of these cells and contribute to their regenerative potential, and telomerase activity and telomere length are commonly considered lifespan predictors. Eusocial insects provide excellent model systems for aging research based on their extraordinary caste-related lifespan differences that contradict the typical fecundity/lifespan trade-off. In agreement with the common presumption, telomerase activity is upregulated in the reproductive, long-lived individuals of eusocial insects such as queens and kings, proposing that telomerase activity acts as a key factor in their extended longevity. But, as documented by the presence of telomerase in somatic tissues of numerous invertebrate and vertebrate species, the connection between telomerase activity and the predicted lifespan is not clear. Here, I ask whether somatic telomerase activity in eusocial reproductives may serve its non-canonical function to protect its individuals against the exacerbated metabolic stress upon reproduction and be a reflection of a more common phenomenon among species. I propose a hypothesis that the presence of telomerase activity in somatic cells reflects a different reproduction strategy of the species.

Demographic profiles and environmental drivers of variation relate to individual breeding state in a long-lived trans-oceanic migratory seabird, the Manx shearwater

Understanding the points in a species breeding cycle when they are most vulnerable to environmental fluctuations is key to understanding interannual demography and guiding effective conservation and management. Seabirds represent one of the most threatened groups of birds in the world, and climate change and severe weather is a prominent and increasing threat to this group. We used a multi-state capture-recapture model to examine how the demographic rates of a long-lived trans-oceanic migrant seabird, the Manx shearwater Puffinus puffinus, are influenced by environmental conditions experienced at different stages of the annual breeding cycle and whether these relationships vary with an individual’s breeding state in the previous year (i.e., successful breeder, failed breeder and non-breeder). Our results imply that populations of Manx shearwaters are comprised of individuals with different demographic profiles, whereby more successful reproduction is associated with higher rates of survival and breeding propensity. However, we found that all birds experienced the same negative relationship between rates of survival and wind force during the breeding season, indicating a cost of reproduction (or central place constraint for non-breeders) during years with severe weather conditions. We also found that environmental effects differentially influence the breeding propensity of individuals in different breeding states. This suggests individual spatio-temporal variation in habitat use during the annual cycle, such that climate change could alter the frequency that individuals with different demographic profiles breed thereby driving a complex and less predictable population response. More broadly, our study highlights the importance of considering individual-level factors when examining population demography and predicting how species may respond to climate change.

Bigger Is Better, Sometimes: The Interaction between Body Size and Carcass Size Determines Fitness, Reproductive Strategies, and Senescence in Two Species of Burying Beetles

The cost of reproduction hypothesis suggests that allocation to current reproduction constrains future reproduction. How organisms accrue reproductive costs and allocate energy across their lifetime may differ among species adapted to different resource types. We test this by comparing lifetime reproductive output, patterns of reproductive allocation, and senescence between two species of burying beetles, Nicrophorus marginatus and N. guttula, that differ in body size, across a range of carcass sizes. These two species of burying beetles maximized lifetime reproductive output on somewhat different–sized resources. The larger N. marginatus did better on large and medium carcasses while the smaller N. guttula did best on small and medium carcasses. For both species, reproduction is costly and reproduction on larger carcasses reduced lifespan more than reproduction on smaller carcasses. Carcass size also affected lifetime reproductive strategies. Each species’ parental investment patterns were consistent with terminal investment on carcasses on which they performed best (optimal carcass sizes). However, they exhibited reproductive restraint on carcass sizes on which they did not perform as well. Reproductive senescence occurred largely in response to carcass size. For both species, reproduction on larger carcasses resulted in more rapid senescence. These data suggest that whether organisms exhibit terminal investment or reproductive restraint may depend on type and amount of resources for reproduction.

The Cost of Reproduction in a Cooperatively Breeding Mammal: Consequences of Seasonal Variation in Rainfall, Reproduction, and Reproductive Suppression

Biological investments, such as reproduction, are influenced by both biotic and abiotic factors and their interactions. The trade-off between reproduction and survival has been well established. Seasonally breeding species, therefore, may exhibit variations in these trade-offs, but there is a dearth of knowledge concerning this. This study investigated the physiological cost of reproduction (measured through oxidative stress) across seasons in the cooperatively breeding highveld mole-rat (Cryptomys hottentotus pretoriae), one of the few seasonal breeding mole-rats. Oxidative stress indicates elevated reactive oxygen species (ROS) levels, which can overwhelm antioxidant defences resulting in damaged proteins, lipids and DNA, which overall can reduce longevity and compromise reproduction. Oxidative markers such as total oxidant status (TOS-measure of total peroxides present), total antioxidant capacity (TAC), oxidative stress index (OSI), and malondialdehyde (MDA) are utilised to measure oxidative stress. In this study, breeding and non-breeding male (NBM) and female mole-rats were captured during the dry season (breeding period) and wet season (non-breeding period). There was an apparent cost of reproduction in the highveld mole-rat; however, the seasonality pattern to the cost of reproduction varied between the sexes. Breeding females (BFs) had significantly higher MDA during the breeding period/dry season in comparison to the non-breeding period/wet season; this is possibly a consequence of bearing and nursing offspring. Contrastingly, breeding males (BMs) showed increased oxidative damage in the non-breeding/wet season compared to the breeding/dry season, possibly due to increased activities of protecting their mating rights for the next breeding/dry season, but this was not significant. Interestingly, during the non-breeding period/wet season, non-breeding females (NBFs) are released from their reproductive suppression, which resulted in increases in TOS and OSI, which again indicated that just the mere ability to be able to breed results in a cost (oxidative stress). Therefore we can speculate that highveld mole-rats exhibited seasonal variation in redox balance brought about by variation in abiotic variables (e.g., rainfall), physiology and behaviour. We conclude that physiological changes associated with reproduction are sufficient to induce significant acute oxidative stress in the plasma of female highveld mole-rats, which become alleviated following transition to the non-breeding season/wet period suggesting a possible hormetic effect.

Methods Of Biologization Of Grain-Grass Crop Rotations And Their Influence On Fertility Of Soddy-Podzolic Soil Of The Forest Zone

On soddy-podzolic soils of the forest zone of the European part of Russia, grain-grass crop rotations are most common for the production of voluminous fodder, food and fodder grain [1,2]. In such crop rotations, the link of perennial grasses is the main factor in the reproduction of soil fertility and the production of high-quality voluminous fodder. Improvement of the grass-field link of such crop rotations based on the cultivation of new species and varieties is an urgent scientific and practical task [3,4,5]. An important way to reduce the cost of reproduction of soil fertility in grain-grass crop rotations is the maximum use of plant residues, including straw and green manure crops, which makes it possible to exclude the use of organic fertilizers on certain arable land or, if necessary, to conduct a dung-free economy [6,7,8]. Improvement of the link of perennial grasses, saturation of crop rotations with legumes, maximum use of plant residues and green manure as organic fertilizers allows to reduce the cost of reproduction of soil fertility, to produce high-quality voluminous and concentrated feed [9,10].

Plasma oxidative stress in reproduction of two eusocial African mole-rat species, the naked mole-rat and the Damaraland mole-rat

One of the most prominent life-history trade-offs involves the cost of reproduction. Oxidative stress has been proposed to be involved in this trade-off and has been associated with reduced life span. There is currently an unclear relationship between oxidative cost and the reproduction-longevity trade-off. The current study, using a non-lethal and minimally invasive (only a single blood sample and no euthanasia) method, investigated whether an oxidative cost (oxidative stress) to reproduction would be apparent in two long-lived eusocial mole-rats, the naked mole-rat (NMR), Heterocephalus glaber, and the Damaraland mole-rat (DMR), Fukomys damarensis, where breeding colony members live longer than non-breeder conspecifics. We measured the direct redox balance in plasma by measuring the oxidative stress index (OSI) based on the ratio of total oxidant status and total antioxidant activity in breeders and non-breeders of both sexes, in the two species. NMR had significantly higher OSI between breeders and non-breeders of each sex, whereas DMR showed no significant differences except for total antioxidant capacity (TAC). The mode of reproductive suppression and the degree of reproductive investment in NMR may explain to some degree the redox balance difference between breeders and non-breeders. DMR show minimal physiological changes between breeders and non-breeders except for the mode of reproduction, which may explain some variations in TAC and TOS values, but similar OSI between breeders and non-breeders.

Oleic Acid Protects Caenorhabditis Mothers From Mating-Induced Death and the Cost of Reproduction

Reproduction comes at a cost, including accelerated death. Previous studies of the interconnections between reproduction, lifespan, and fat metabolism in C. elegans were predominantly performed in low-reproduction conditions. To understand how increased reproduction affects lifespan and fat metabolism, we examined mated worms; we find that a Δ9 desaturase, FAT-7, is significantly up-regulated. Dietary supplementation of oleic acid (OA), the immediate downstream product of FAT-7 activity, restores fat storage and completely rescues mating-induced death, while other fatty acids cannot. OA-mediated lifespan restoration is also observed in C. elegans mutants suffering increased death from short-term mating, and in mated C. remanei females, indicating a conserved role of oleic acid in post-mating lifespan regulation. Our results suggest that increased reproduction can be uncoupled from the costs of reproduction from somatic longevity regulation if provided with the limiting lipid, oleic acid.

Reproductive activation in honeybee ( Apis mellifera ) workers protects against abiotic and biotic stress

Social insect reproductives exhibit exceptional longevity instead of the classic trade-off between somatic maintenance and reproduction. Even normally sterile workers experience a significant increase in life expectancy when they assume a reproductive role. The mechanisms that enable the positive relation between the antagonistic demands of reproduction and somatic maintenance are unclear. To isolate the effect of reproductive activation, honeybee workers were induced to activate their ovaries. These reproductively activated workers were compared to controls for survival and gene expression patterns after exposure to Israeli Acute Paralysis Virus or the oxidative stressor paraquat. Reproductive activation increased survival, indicating better immunity and oxidative stress resistance. After qPCR analysis confirmed our experimental treatments at the physiological level, whole transcriptome analysis revealed that paraquat treatment significantly changed the expression of 1277 genes in the control workers but only two genes in reproductively activated workers, indicating that reproductive activation preemptively protects against oxidative stress. Significant overlap between genes that were upregulated by reproductive activation and in response to paraquat included prominent members of signalling pathways and anti-oxidants known to affect ageing. Thus, while our results confirm a central role of vitellogenin, they also point to other mechanisms to explain the molecular basis of the lack of a cost of reproduction and the exceptional longevity of social insect reproductives. Thus, socially induced reproductive activation preemptively protects honeybee workers against stressors, explaining their longevity. This article is part of the theme issue ‘Ageing and sociality: why, when and how does sociality change ageing patterns?'

FEATURES OF DETERMINATION OF COST OF RIFLE SHOOTING-IRON

The article is devoted to the study of the issues of conducting a complex forensic commodity and forensic ballistic examination of small arms firearms of the range of specialized retail trade network. Attention is paid to the importance of providing a judicial opinion on a comprehensive investigation to determine the amount of damage caused by the crime, which will be used by pre-trial and judicial investigation authorities as a source of evidence in criminal, civil, commercial and administrative cases. The problem faced by commodity experts in the study of firearms and determining their value has been studied. Features of research of these objects are considered, the stages and sequence of complex research of the weapon are schematically represented. In particular, the ballistic stage of the study is described in detail. Forensic signs of belonging of the object to the firearm, constructive signs and the signs characterizing a condition of object and a way of its manufacturing that allows to reveal separate individual signs of the small arms and to carry out its exact identification are resulted. The problematic issues of ballistic research of firearms are illustrated by practical examples. The algorithm of carrying out of a stage of forensic research on an estimation of consumer properties of the weapon is stated; the expediency of using certain methodological approaches and methods of establishing the market value of weapons generally accepted in forensic science has been determined. The expediency of applying costly and comparative methodological approaches during the commodity research stage to determine the value of research objects is substantiated. Describes the feasibility of using a comparative methodological approach, when the secondary market for the sale of the object under study is quite developed and there is sufficient reliable information on the prices of offers for similar property; costly methodological approach - when the market of purchase and sale of these objects in use is significantly limited, there are no analogues of the investigated property in the secondary market, which denies the possibility of applying a comparative methodological approach, but it is possible to determine the cost of reproduction (replacement) estimates by a similar object.