Fluctuations in the body size of marine invertebrates through the Pliensbachian–Toarcian extinction event

Despite an increasing incidence of body image and eating disturbances in men, research on men and the ways in which they are affected by the media remain greatly under-documented. Given the fact that men are not immune to media images and are increasingly objectified in the media (Rohlinger, 2002), some men may be under as much pressure as women to achieve cultural ideals of physical appearance depicted by the media. The media not only reflects cultural environments but it can also actively shape social norms as being recognized as an important socialization agent. In Western cultures, the male appearance ideal is leanness with defined musculature. Emphasis on muscularity for male body ideals has also been noted with children’s action toys (Baghurst, Carlston, Wood, & Wyatt, 2007). Although men are not targeted as obviously as fitness magazines target bodybuilders, men are increasingly targeted by advertisements in health and lifestyle magazines concerning how to improve their shape, tone their m...

Body size trends in the Ordovician to earliest Silurian of the Oslo Region

Titanosauriformes is a conspicuous and diverse group of sauropod dinosaurs that inhabited almost all land masses during Cretaceous times. Besides the diversity of forms, the clade comprises one of the largest land animals found so far, Argentinosaurus, as well as some of the smallest sauropods known to date, Europasaurus and Magyarosaurus. They are therefore good candidates for studies on body size trends such as the Cope's rule, the tendency towards an increase in body size in an evolutionary lineage. We used statistical methods to assess body size changes under both phylogenetic and nonphylogenetic approaches to identify body size trends in Titanosauriformes. Femoral lengths were collected (or estimated from humeral length) from 46 titanosauriform species and used as a proxy for body size. Our findings show that there is no increase or decrease in titanosauriform body size with age along the Cretaceous and that negative changes in body size are more common than positive ones (although not statistically significant) for most of the titanosauriform subclades (e.g. Saltasaridae, Lithostrotia, Titanosauria and Somphospondyli). Therefore, Cope's rule is not supported in titanosauriform evolution. Finally, we also found a trend towards a decrease of titanosauriform mean body size coupled with an increase in body size standard deviation, both supporting an increase in body size variation towards the end of Cretaceous.

Changes in brachiopod body size prior to the Early Toarcian (Jurassic) Mass Extinction

Change in body size is considered to be one of the animal responses to climate warming, although in many cases it is difficult to show whether it is evolutionary or a result of phenotypic plasticity. In this study, we analysed long-term changes in the body size and sex ratio of the European polecat Mustela putorius in relation to two factors: climate warming and competition with the invasive American mink Neovison vison . In the years 1959–2021, the average body mass of polecats inhabiting north-eastern Poland increased from 869 to 1109 g in males and from 449 to 690 g in females, whereas structural body size (the condylobasal length of the skull) increased from 64.4 to 68.0 mm in males and from 55.9 to 59.6 mm in females. The rates of these increases were different for both measures; in consequence, the index of body condition changed non-linearly over time with a high increase in last 30–40 years. The observed increase in polecat body mass and skull size correlated with the rise of mean winter and summer temperatures. We explain the recorded trends by easier access to amphibians (the staple food of polecats in the study area) in mild winters, which increases the survival rate of larger polecats and/or leads to a faster growth rate of subadults in warmer summers. Competition for food between the native polecat and invasive mink could play a role in the increase of polecat body size simultaneously with climate warming, but the timing of recorded changes suggests the second factor to be more important. Our study also confirmed a previous observation of increasing skewed sex-ratio towards polecat males, which, similarly to changes in polecat body size, could have resulted both from climate warming and competition with mink.

A dynamic cycle of O-linked GlcNAc (O-GlcNAc) addition and removal is catalyzed by O-GlcNAc transferase and O-GlcNAcase, respectively, in a process that serves as the final step in a nutrient-driven "hexosamine-signaling pathway." Evidence points to a role for O-GlcNAc cycling in diabetes and insulin resistance. We have used Drosophila melanogaster to determine whether O-GlcNAc metabolism plays a role in modulating Drosophila insulin-like peptide (dilp) production and insulin signaling. We employed transgenesis to either overexpress or knock down Drosophila Ogt(sxc) and Oga in insulin-producing cells (IPCs) or fat bodies using the GAL4-UAS system. Knockdown of Ogt decreased Dilp2, Dilp3, and Dilp5 production, with reduced body size and decreased phosphorylation of Akt in vivo. In contrast, knockdown of Oga increased Dilp2, Dilp3, and Dilp5 production, increased body size, and enhanced phosphorylation of Akt in vivo. However, knockdown of either Ogt(sxc) or Oga in the IPCs increased the hemolymph carbohydrate concentration. Furthermore, phosphorylation of Akt stimulated by extraneous insulin in an ex vivo cultured fat body of third instar larvae was diminished in strains subjected to IPC knockdown of Ogt or Oga. Knockdown of O-GlcNAc cycling enzymes in the fat body dramatically reduced neutral lipid stores. These results demonstrate that altered O-GlcNAc cycling in Drosophila IPCs modulates insulin production and influences the insulin responsiveness of peripheral tissues. The observed phenotypes in O-GlcNAc cycling mimic pancreatic β-cell dysfunction and glucose toxicity related to sustained hyperglycemia in mammals.

Evolutionary and ecophenotypic controls on bivalve body size distributions following the end-Permian mass extinction

Reflections on nutrition in biological anthropology.

The insular body size trends for different vertebrate families are compared. Certain groups such as lagomorphs, bats, artiodactyls, elephants, foxes, raccoons, snakes, and teiid and lacertid lizards are habitually represented by relatively smaller forms on islands. On the other hand, cricetid rodents, iguanid lizards, tortoises, and bears often have races with larger body sizes on islands. Contrary to conventional niche theoretic concepts, in many instances knowledge of the body sizes of some of these animals' insular and mainland competitors does not help explain the difference in that species body size in the 2 places. To account for these divergent size changes I examine optimum body size models that use as the optimization criterion the net energy gained by an organism over a given time period. These models predict that increases in the mean amount of available food should lead to evolutionary increases in body size, but only if body size is not tightly constrained by additional physical or biotic factors: such additional factors might be important if a change in body size alters an animal's effectiveness in finding or handling preferred food items or increases competition with its neighbors. Next using arguments derived from simple non—age—structured 2 species predator—prey models, the availability of food for a given consumer species at equilibrium is compared in theoretical island and mainland situations. Because islands usually contain fewer competitors and the insular physical environment is often more moderate, food availability for colonists is initially expected to be high. On the other hand, as the population grows resources will become depleted. Further, the loss of many predator species on islands may allow consumer densities to increase to such an extent that at equilibrium food may become relatively more limiting for consumers on islands than on the mainland. Whether the supply to demand ratio (S:D) of consumers for their food is ultimately greater or lower will depend on the relative magnitude of these various factors. Within this framework, a necessary condition for island S:D ratios to be greater than on the mainland is that the consumers maintain individual feeding territories. For animals whose body sizes are not tightly bound within narrow limits by physical or competitive restraints, an increase in S:D should lead to an evolutionary increase in body size. Accordingly, a good association is found between the presence or absence of territoriality and the direction of the insular body size shift in a number of different vertebrate groups. Yet there are exceptions which fall into 2 categories: First, if a species' mainland predators preferentially take larger individuals, selection favoring small size may override selection based on optimizing energy input. Such may have been the case for the now extinct mainland relatives of certain giant relictual insular reptiles. Secondly, an animal's body size may be tightly constrained by physical or competitive factors. The body size of island foxes, rattlesnakes, and some lizards appears to be primarily adjusted to the competitive milieu along typical niche theoretic lines. That is, body size may be predicted quite well from knowing the size class of competitors which are absent from an island or from differences in the species' prey—size distribution between island and mainland sites.

Recent changes in global climate have been linked with changes in animal body size. While declines in body size are commonly explained as an adaptive thermoregulatory response to climate warming, many species do not decline in size, and alternative explanations for size change exist. One possibility is that temporal changes in animal body size are driven by changes in environmental productivity and food availability. This hypothesis is difficult to test due to the lack of suitable estimates that go back in time. Here, we use an alternative, indirect, approach and assess whether continent‐wide changes over the previous 100 years in body size in 15 species of Australian birds are associated with changes in their yellow carotenoid‐based plumage coloration. This type of coloration is strongly affected by food availability because birds cannot synthesize carotenoids and need to ingest them, and because color expression depends on general body condition. We found significant continent‐wide intraspecific temporal changes in body size (wing length) and yellow carotenoid‐based color (plumage reflectance) for half the species. Direction and magnitude of changes were highly variable among species. Meta‐analysis indicated that neither body size nor yellow plumage color showed a consistent temporal trend and that changes in color were not correlated with changes in size over the past 100 years. We conclude that our data provide no evidence that broad‐scale variation in food availability is a general explanation for continent‐wide changes in body size in this group of species. The interspecific variability in temporal changes in size as well as color suggests that it might be unlikely that a single factor drives these changes, and more detailed studies of museum specimens and long‐term field studies are required to disentangle the processes involved.

The inverse associations between birth weight and later adverse health outcomes and the positive associations between adult body size and poor health imply that increases in relative body size between birth and adulthood may be undesirable. In this paper, the authors describe life course path analysis, a method that can be used to jointly estimate associations between body sizes at different time points and associations of body sizes throughout life with health outcomes. Additionally, this method makes it possible to assess both the direct effect and the indirect effect mediated through later body size, and thereby the total effect, of size and changes in size on later outcomes. Using data on childhood body size and adult systolic blood pressure from a sample of 1,284 Danish men born between 1936 and 1970, the authors compared results from path analysis with results from 3 standard regression methods. Path analysis produced easily interpretable results, and compared with standard regression methods it produced a noteworthy gain in statistical power. The effect of change in relative body size on adult blood pressure was more pronounced after age 11 years than in earlier childhood. These results suggest that increases in body size prior to age 11 years are less harmful to adult blood pressure than increases occurring after this age.

BackgroundThe association between change in weight or body mass index, and mortality is widely reported, however, both measures fail to account for fat distribution. Change in waist circumference, a measure of central adiposity, in relation to mortality has not been studied extensively.MethodsWe investigated the association between mortality and changes in directly measured waist circumference, hips circumference and weight from baseline (1990–1994) to wave 2 (2003–2007) in a prospective cohort study of people aged 40–69 years at baseline. Cox regression, with age as the time metric and follow-up starting at wave 2, adjusted for confounding variables, was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for change in body size in relation to mortality from all causes, cardiovascular disease and cancer.ResultsThere were 1465 deaths (109 cancer, 242 cardiovascular disease) identified during an average 7.7 years of follow-up from 21 298 participants. Compared to minimal increase in body size, loss of waist circumference (HR: 1.26; 95% CI: 1.09–1.47), weight (1.80; 1.54–2.11), or hips circumference (1.35; 1.15–1.57) were associated with an increased risk of all-cause mortality, particularly for older adults. Weight loss was associated with cardiovascular disease mortality (2.40; 1.57–3.65) but change in body size was not associated with obesity-related cancer mortality.ConclusionThis study confirms the association between weight loss and increased mortality from all-causes for older adults. Based on evidence from observational cohort studies, weight stability may be the recommended option for most adults, especially older adults.

Birth weight, early life course BMI, and body size change: Chains of risk to adult inflammation?

Contemporary climate change has been linked to widespread changes in phenology and in the geographic distribution of species. Based on Bergmann’s rule, body sizes of birds have been predicted to decline as global temperatures increase. We examined changes in body size of 20 resident and short-distance migrant passerine species in eastern North America between 1980 and 2012, and how changes in resident species related to annual mean summer and mean winter temperatures. We found that wing length generally increased and that fat-free mass did not change significantly. Fat score, a measure of body condition, declined over time. However, changes in wing length, fat-free mass, and fat score all showed significant variation across species. For resident species, increasing mean summer temperatures were generally associated with shorter wing lengths, but were not related to fat-free mass or fat score. Increasing mean winter temperatures were associated with reduced fat-free mass but not with wing length or fat score. Temperature effects did not vary significantly across species for any of the three measures. Across resident species, the magnitude of body size change over time was not related to the influence of mean winter or mean summer temperatures, and may have been driven by other factors. Our findings contrast with those from a study at a nearby bird banding station, in which widespread decreases in wing length and fat-free mass were observed. Our results demonstrate that populations of the same species can exhibit opposing changes in body size over short geographic distances (<250 km). We conclude that changes in body size are heterogeneous over short time scales and can vary across and within species over short distances. Continued advances in understanding how body size changes relate to climate change must embrace this inherent complexity and consider alternative hypotheses.

Overweight Adolescent African-American Mothers Gain Weight in Spite of Intentions to Lose Weight