scholarly journals How many cubs can a mum raise? Maternal age and size influence litter size in polar bears

2019 ◽  
Author(s):  
Dorinda Marie Folio ◽  
Jon Aars ◽  
Olivier Gimenez ◽  
Andrew E. Derocher ◽  
Øystein Wiig ◽  
...  
Keyword(s):  
Litter Size ◽  
Maternal Age ◽  
Life History Theory ◽  
Reproductive Effort ◽  
Maternal Investment ◽  
Polar Bears ◽  
Maternal Size ◽  
Large Size ◽  
Specific Variation

AbstractLife history theory predicts that females’ age and size affect the level of maternal investment in current reproduction, balanced against future reproductive effort, maintenance and survival. Using long-term (30 years) individual data on 231 female polar bears (Ursus maritimus), we assessed age- and size-specific variation on litter size. Litter size varied with maternal age, younger females had higher chances of losing a cub during their first months of life. Results suggest an improvement of breeding abilities early in life due to experience with subsequent reproductive senescence. Litter size increased with maternal size, indicating that size may reflect individual quality. Heterogeneity was observed among the largest females, suggesting that large size comes at a cost. Maternal traits and environmental conditions may act together to influence reproductive success.

scholarly journals How many cubs can a mum nurse? Maternal age and size influence litter size in polar bears

2019 ◽  
Vol 15 (5) ◽  
pp. 20190070 ◽  
Author(s):  
Dorinda Marie Folio ◽  
Jon Aars ◽  
Olivier Gimenez ◽  
Andrew E. Derocher ◽  
Øystein Wiig ◽  
...  
Keyword(s):  
Litter Size ◽  
Maternal Age ◽  
Life History Theory ◽  
Maternal Investment ◽  
Stabilizing Selection ◽  
Polar Bears ◽  
Female Body Size ◽  
Large Size ◽  
Specific Variation ◽  
Size Heterogeneity

Life-history theory predicts that females' age and size affect the level of maternal investment in current reproduction, balanced against the future reproductive effort, maintenance and survival. Using long-term (30 years) individual data on 193 female polar bears ( Ursus maritimus ), we assessed age- and size-specific variation on litter size. Litter size varied with maternal age, younger females had higher chances of losing a cub during their first months of life. Results suggest an improvement in reproductive abilities early in life due to experience with subsequent reproductive senescence. Litter size increased with maternal size, indicating that size may reflect individual quality. We also found an optimum in the probability of having twins, suggesting stabilizing selection on female body size. Heterogeneity was observed among the largest females, suggesting that large size comes at a cost.

scholarly journals Short- and long-term effects of litter size manipulation in a small wild-derived rodent

2014 ◽  
Vol 10 (3) ◽  
pp. 20131096 ◽  
Author(s):  
Mikko Lehto Hürlimann ◽  
Antoine Stier ◽  
Olivier Scholly ◽  
François Criscuolo ◽  
Pierre Bize
Keyword(s):  
Litter Size ◽  
Energy Demand ◽  
Reproductive Effort ◽  
Common Vole ◽  
Long Term Effects ◽  
Litter Size Manipulation ◽  
Laboratory Rodents ◽  
Short And Long Term ◽  
Long Term Consequences

Iteroparous organisms maximize their overall fitness by optimizing their reproductive effort over multiple reproductive events. Hence, changes in reproductive effort are expected to have both short- and long-term consequences on parents and their offspring. In laboratory rodents, manipulation of reproductive efforts during lactation has however revealed few short-term reproductive adjustments, suggesting that female laboratory rodents express maximal rather than optimal levels of reproductive investment as observed in semelparous organisms. Using a litter size manipulation (LSM) experiment in a small wild-derived rodent (the common vole; Microtus arvalis ), we show that females altered their reproductive efforts in response to LSM, with females having higher metabolic rates and showing alternative body mass dynamics when rearing an enlarged rather than reduced litter. Those differences in female reproductive effort were nonetheless insufficient to fully match their pups’ energy demand, pups being lighter at weaning in enlarged litters. Interestingly, female reproductive effort changes had long-term consequences, with females that had previously reared an enlarged litter being lighter at the birth of their subsequent litter and producing lower quality pups. We discuss the significance of using wild-derived animals in studies of reproductive effort optimization.

scholarly journals Maternal age alters offspring lifespan, fitness, and lifespan extension under caloric restriction

2019 ◽  
Author(s):  
Martha J. Bock ◽  
George C. Jarvis ◽  
Emily L. Corey ◽  
Emily E. Stone ◽  
Kristin E. Gribble
Keyword(s):  
Caloric Restriction ◽  
Maternal Age ◽  
Life History Theory ◽  
Maternal Investment ◽  
Age Effects ◽  
Therapeutic Interventions ◽  
Lifespan Extension ◽  
Age Related ◽  
Negative Effect ◽  
Food Conditions

ABSTRACTMaternal age has a negative effect on offspring lifespan in a range of taxa and is hypothesized to influence the evolution of aging. However, the mechanisms of maternal age effects are unknown, and it remains unclear if maternal age alters offspring response to therapeutic interventions to aging. Here, we evaluate maternal age effects on offspring lifespan, reproduction, and the response to caloric restriction, and investigate maternal investment as a source of maternal age effects using the rotifer,Brachionus manjavacas, an aquatic invertebrate. We found that offspring lifespan and fecundity decline with increasing maternal age. Caloric restriction increases lifespan in all offspring, but the magnitude of lifespan extension is greater in the offspring from older mothers. The trade-off between reproduction and lifespan extension under low food conditions expected by life history theory is observed in young-mother offspring, but not in old-mother offspring. Age-related changes in maternal resource allocation to reproduction do not drive changes in offspring fitness or plasticity under caloric restriction inB. manjavacas. Our results suggest that the declines in reproduction in old-mother offspring negate the evolutionary fitness benefits of lifespan extension under caloric restriction.

Modern Possibilities of Organ-Preserving Treatment in Children with Intraocular Retinoblastoma

2018 ◽  
Vol 5 (3) ◽  
pp. 175-187 ◽  
Author(s):  
O. V. Gorovtsova ◽  
T. L. Ushakova ◽  
V. G. Polyakov
Keyword(s):  
Drug Delivery ◽  
Survival Rate ◽  
Cancer Therapy ◽  
Neoadjuvant Chemotherapy ◽  
Patient Survival ◽  
Focal Therapy ◽  
Local Drug Delivery ◽  
Large Size ◽  
Intraocular Retinoblastoma

Retinoblastoma is one of highly curable diseases; today the total 5-year survival rate in patients with retinoblastoma exceeds 95%. The article summarizes the current world experience on treatment of patients with intraocular retinoblastoma. The treating skills of intraocular malignant tumor in children are a balance between the patient’s life and the preservation of an eye and its visual functions. The complex and challenging task is the treatment of common intraocular retinoblastoma groups «C», «D», «E» when the large size or localization of the tumor does not allow performing the local (focal) destruction of the tumor. As a rule, in such cases neoadjuvant chemotherapy (CT) is performed at the first stage in order to reduce the size of the tumor for further focal therapy. However, the analysed data on the effectiveness of neoadjuvant CT in combination with focal or radiotherapy demonstrated the limited possibilities of the proposed therapy. Local drug delivery in cancer therapy became a real breakthrough in the organ-preserving treatment of children with large intraocular retinoblastoma. The most widely used current methods of local drug delivery are intravitreal (IVitC) and selective intra-arterial chemotherapy (SIAC) as monotherapy or in combination with neoadjuvant CT and focal therapy which significantly increased the percentage of preserved eyes without radiotherapy administration or damage to the patient survival. The review discusses the different IVitC and SIAC techniques, chemotherapy schemes, dosages of chemotherapy, immediate and long-term complications of treatment.

scholarly journals Contributions to Management Strategies in the NE Atlantic Regarding the Life History and Population Structure of a Key Deep-Sea Fish (Mora moro)

Biology ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 522
Author(s):  
Régis Santos ◽  
Wendell Medeiros-Leal ◽  
Osman Crespo ◽  
Ana Novoa-Pabon ◽  
Mário Pinho
Keyword(s):  
Population Structure ◽  
Life History ◽  
Deep Sea ◽  
Management Strategies ◽  
Size Composition ◽  
Large Size ◽  
The Common ◽  
Fishing Impacts ◽  
Sea Fish

With the commercial fishery expansion to deeper waters, some vulnerable deep-sea species have been increasingly captured. To reduce the fishing impacts on these species, exploitation and management must be based on detailed and precise information about their biology. The common mora Mora moro has become the main deep-sea species caught by longliners in the Northeast Atlantic at depths between 600 and 1200 m. In the Azores, landings have more than doubled from the early 2000s to recent years. Despite its growing importance, its life history and population structure are poorly understood, and the current stock status has not been assessed. To better determine its distribution, biology, and long-term changes in abundance and size composition, this study analyzed a fishery-dependent and survey time series from the Azores. M. moro was found on mud and rock bottoms at depths below 300 m. A larger–deeper trend was observed, and females were larger and more abundant than males. The reproductive season took place from August to February. Abundance indices and mean sizes in the catch were marked by changes in fishing fleet operational behavior. M. moro is considered vulnerable to overfishing because it exhibits a long life span, a large size, slow growth, and a low natural mortality.

A Primer of Life Histories

2021 ◽  
Author(s):  
Jeffrey A. Hutchings
Keyword(s):  
Life History ◽  
Life Histories ◽  
Life History Theory ◽  
Life History Traits ◽  
Reproductive Effort ◽  
Effective Means ◽  
Academic Experience ◽  
Sustainable Exploitation ◽  
Evolution Of Life ◽  
Opportune Time

Life histories describe how genotypes schedule their reproductive effort throughout life in response to factors that affect their survival and fecundity. Life histories are solutions that selection has produced to solve the problem of how to persist in a given environment. These solutions differ tremendously within and among species. Some organisms mature within months of attaining life, others within decades; some produce few, large offspring as opposed to numerous, small offspring; some reproduce many times throughout their lives while others die after reproducing just once. The exponential pace of life-history research provides an opportune time to engage and re-engage new generations of students and researchers on the fundamentals and applications of life-history theory. Chapters 1 through 4 describe the fundamentals of life-history theory. Chapters 5 through 8 focus on the evolution of life-history traits. Chapters 9 and 10 summarize how life-history theory and prediction has been applied within the contexts of conservation and sustainable exploitation. This primer offers an effective means of rendering the topic accessible to readers from a broad range of academic experience and research expertise.

scholarly journals Uncoupling Inter-Municipal Cooperation Capacity: Lithuanian Municipalities’ Efforts To Sustain Services Provision

2018 ◽  
Vol 11 (2) ◽  
pp. 32-60
Author(s):  
Jurga Bučaitė-Vilkė ◽  
Remigijus Civinskas ◽  
Aistė Lazauskienė
Keyword(s):  
Service Delivery ◽  
Public Services ◽  
Central Government ◽  
Municipal Service ◽  
Economy Of Scale ◽  
External Influences ◽  
Services Delivery ◽  
Large Size ◽  
Cooperative Solutions

Abstract Despite the absence of the long-term tradition of inter-municipal cooperation in Lithuania, the country represents a compelling case of cooperative solutions which are mostly focused on public services delivery design imposed by the central government. The article provides theoretical and empirical insights on the inter-municipal cooperative capacities and their scope in the case of Lithuania, with reference to the size of the municipality. The results reveal that the large size municipalities are more likely to benefit from collaborative arrangements in comparison to small size municipalities which have less institutional ability for collaboration. In this respect, the external influences imposed by the central authorities’ agenda on implementing economy of scale principles and strong municipal service delivery regulations is extremely important for understanding the municipal efforts for collaboration.

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