The relationship between fecundity and adult body weight in Homeotherms

Summary Bythotrephes cederstroemii Schoedler, a predatory freshwater zooplankter (Crustacea: Cladocera), was first found in the Laurentian Great Lakes in December 1984. The first individuals were from Lake Huron, followed in 1985 with records from Lakes Erie and Ontario. By late August, 1986 the species had spread to southern Lake Michigan (43°N). Bythotrephes has not previously been reported from North America, but has been restricted to a northern and central Palearctic distribution. Its dramatic and widespread rise in abundance in Lake Michigan was greatest in offshore regions. Bythotrephes appears to be invading aggressively, but avoiding habitats presently occupied by glacio-marine relict species that became established in deep oligotrophic North American lakes after the Wisconsin glaciation. Because it is a voracious predator its invasion may lead to alterations in the native zooplankton fauna of the Great Lakes. It offers the chance to study how invading plankton species join an existing community. Judging from its persistence and success in deep European lakes, Bythotrephes may now become a permanent member of zooplankton communities in the Nearctic.     

The relationship between symptoms of depression and body weight in younger adults

A bidirectional relationship between obesity and depression may exist, though previous results are conflicting. The objectives of our study were to determine whether there is a bidirectional relationship between obesity and symptoms of depression in younger adults and whether this relationship varies with sociodemographic factors. We used data from 7,980 participants in the National Longitudinal Survey of Youth 1979 to examine whether baseline depressive symptoms (score ≥ 10 on a seven-item subscale of the CES-D) in 1992, predicted adjusted percent change in BMI between 1992 and 1994. We then examined whether obesity in 1992 predicted the development of symptoms of depression in 1994, after adjustment for confounders. We found that the presence of baseline depressive symptoms was not prospectively associated with increase in percent BMI, except in Hispanic women. Additionally, baseline obesity was not associated with higher risk of future symptoms of depression in the sample overall (adjusted risk ratio (RR) 1.20; 99% CI 0.91-1.60). However, in those of higher socioeconomic status, obesity was associated with almost double the risk of depressive symptoms compared to nonobese (highest income category: adjusted RR 1.97; 99% CI 1.14-3.40). We concluded that although obesity was not associated with risk of depression symptoms in the population overall, obesity was associated with an increased risk of developing depressive symptoms in those of higher socioeconomic status. Sociodemographic factors may be important modifiers of the relationship between obesity and depression.     

The relationship between ecological segregation and sexual body size dimorphism in large herbivores

Ecological segregation (sexual differences in diet or habitat use) in large herbivores has been intimately linked to sexual body size dimorphism, and may affect both performance and survival of the sexes. However, no one has tested comparatively whether segregation occurs at a higher frequency among more dimorphic species. To test this comparatively, data on sex-specific diet, habitat use and body size of 40 species of large herbivores were extracted from the literature. The frequency of ecological segregation was higher among more dimorphic herbivores; however, this was only significant for browsers. This provides the first evidence that segregation is more common among more dimorphic species. The comparative evidence supported the nutritional-needs hypothesis over the incisor breadth hypothesis, as there was no difference in frequency of segregation between seasons with high and low resource levels, and since segregation was also evident among browsers. Whether the absence of a correlation between ecological segregation and level of sexual body size dimorphism for intermediate feeders and grazers is due to biological differences relative to browsers or to the fact that the monomorphic species included in the analysis were all browsers is discussed. Received: 18 August 1999 / Accepted: 31 January 2000     

The relationship between nephron number,kidney size and body weight in two inbred mouse strains

While some reports in humans have shown that nephron number is positively correlated with height, body weight or kidney weight, other studies have not reproduced these findings. To understand the impact of genetic and environmental variation on these relationships, we examined whether nephron number correlates with body weight, kidney planar surface area, or kidney weight in two inbred mouse strains with contrasting kidney sizes but no overt renal pathology: C3H/HeJ and C57BL/6J. C3H/HeJ mice had smaller kidneys at birth and larger kidneys by adulthood, however there was no significant difference in nephron number between the two strains. We did observe a correlation between kidney size and body weight at birth and at adulthood for both strains. However, there was no relationship between nephron number and body weight or between nephron number and kidney size. From other studies, it appears that a greater than 2-fold variation is required in each of these parameters in order to demonstrate these relationships, suggesting they are highly dependent on scale. Our results are therefore not surprising since there was a less than 2-fold variation in each of the parameters examined. In summary, the relationship between nephron number and body or kidney size is most likely to be demonstrated when there is greater phenotypic variation either from genetic and/or environmental factors.     

The relationship between nephron number, kidney size and body weight in two inbred mouse strains

While some reports in humans have shown that nephron number is positively correlated with height, body weight or kidney weight, other studies have not reproduced these findings. To understand the impact of genetic and environmental variation on these relationships, we examined whether nephron number correlates with body weight, kidney planar surface area, or kidney weight in two inbred mouse strains with contrasting kidney sizes but no overt renal pathology: C3H/HeJ and C57BL/6J. C3H/HeJ mice had smaller kidneys at birth and larger kidneys by adulthood, however there was no significant difference in nephron number between the two strains. We did observe a correlation between kidney size and body weight at birth and at adulthood for both strains. However, there was no relationship between nephron number and body weight or between nephron number and kidney size. From other studies, it appears that a greater than two-fold variation is required in each of these parameters in order to demonstrate these relationships, suggesting they are highly dependent on scale. Our results are therefore not surprising since there was a less than two-fold variation in each of the parameters examined. In summary, the relationship between nephron number and body or kidney size is most likely to be demonstrated when there is greater phenotypic variation either from genetic and/or environmental factors.     

The relationship between obesity and seasonal variation in body weight among elementary school children in Tokyo

Typical patterns of seasonal variation in body weight among Japanese children involve increases during the fall and/or winter and decreases during the summer. However, atypical variations, namely, increases in weight during the summer, have been reported for obese children. The present study examines whether weight gain during the summer (i.e., July through September) is a possible cause of obesity. We examined seasonal changes in weight for 446 elementary school children in Tokyo in six waves between 1972 and 2004. Weight was measured monthly for 6 years in each child and was evaluated by means of time-series analysis. Overall, significant seasonal variations in weight were found in 86% of the children, most of which were typical (i.e., decreases during the summer and increases during the fall, winter, and/or early spring). On the other hand, weight gain in the summer was observed exclusively among obese children. Children whose weight increased during the summer holiday spent most of their time comfortably indoors because of air conditioners, which became popular in 1970s. A possible explanation of the observed weight gain during the summer seems to be changes in life style associated with the use of air conditioning, concomitant with insufficient physical exercise and excessive consumption of food and drink, which could disturb the rhythms of seasonal weight changes and lead to obesity.     

Allometric relationship between oxygen consumption and body weight of mosquitofish,Gambusia affinis

Synopsis The allometric relationship between body size and oxygen consumption of Gambusia affinis at 28° C was determined under controlled experimental conditions, using a manometric respirometer. The allometric exponent (b-value) was 0.64 ± 0.02 S.E. (n = 51). Oxygen consumption was not influenced by any time-related factors during the 17 days of measurements. Variance between replicated oxygen consumption trials on individual fish was negligible. Specific oxygen consumption rates of several G. affinis at 28° C that were determined by using a sealed vessel and O₂ electrode respirometry method were similar to the rates measured by the manometric respirometry method in similar-sized G. affinis.     

A re-examination of the relationship between thermal conductance and body weight in mammals

• 1.1. The following equation based on 230 conductance values for 192 species of mammals of body weights ranging from 3.5 to 150,000 g describes the relationship of conductance below thermal neutrality to body weight in mammals: C = 0.760 W^−0.426, where C has units of mlO₂/g·h·°C and W is body weight in g.
• 2.2. Bats, order Chiroptera, have conductance values higher than predicted from body weight; conductance is predicted by the equation : C = 1.54 W^−0.54.
• 3.3. Heteromyid and cricetid rodents have conductance values below predicted and the following equations predict conductance in these two families. C = 0.62 W^−0.44 and C = 1.03 W^−0.54, respectively.

     

Modeling the relationship between body weight and energy intake: A molecular diffusion-based approach

ABSTRACT: BACKGROUND: Body weight is at least partly controlled by the choices made by a human in response to external stimuli. Changes in body weight are mainly caused by energy intake. By analyzing the mechanisms involved in food intake, we considered that molecular diffusion plays an important role in body weight changes. We propose a model based on Fick's second law of diffusion to simulate the relationship between energy intake and body weight. RESULTS: This model was applied to food intake and body weight data recorded in humans; the model showed a good fit to the experimental data. This model was also effective in predicting future body weight. CONCLUSIONS: In conclusion, this model based on molecular diffusion provides a new insight into the body weight mechanisms.     

The genetic relationship between the Hbb locus and body size in a population of mice divergently selected for six-week body weight.

Both pleiotropy and linkage were examined as possible explanations for the fixation of the Hbb3 allele in the six Large lines of a population of mice divergently selected for six-week body weight (six replicates in each direction and six controls). A survey of over 1200 individuals in the lines still segregating at the Hbb locus excluded pleiotropy as a possible explanation. The results showed a nonsignificant effect of haemoglobin genotype on body weight. The linkage relationship of the Hbb locus was examined using a backcross mating system. The Hbb3 c+ region (chromosome 7) of a Large line was backcrossed into its corresponding Small line (Hbb4 c). The resultant difference in body weight between the two segregants (Hbb8 c+ [Hbb4 c; Hbb4 c/Hbb4 c) was measured. The results suggested linkage as the most plausible explanation for the fixation of the Hbb4 allele in the six Large lines.     

The relationship between aromatase activity and body fat distribution

The metabolism of androstenedione (A) to estrone (E1) and 5 alpha-reduced androgens was studied in stromal cells derived from human adipose tissue from different body sites. The tissue was obtained from non-obese patients undergoing cosmetic liposuction or at the time of surgery for reduction mammoplasty. The conversion of A to E1 per 1x 10(6) cells was between 6- and 30-fold greater in the upper thigh, buttock, and flank than in the abdomen. These differences were present in primary culture and persisted to at least the third subculture. Estrogen formation in breast adipose tissue was similar to that found in cells from abdominal fat. The formation of 5 alpha-reduced metabolites (5 alpha-androstenedione, androsterone, and dihydrotestosterone) varied from patient to patient but was similar in cells from different body sites. These studies show that the regional distribution of fat may influence the metabolism of androgens in adipose tissue, with upper body fat tending to form a lower ratio of estrogens to 5 alpha-reduced androgens than lower body fat.     

The relationship between body size and population abundance in animals

On average, large-bodied species live at lower densities than small-bodied ones. Early studies suggested that population densities might scale so that the energy use of a population is independent of body size. However, recent work shows that, at the scale of local communities, this is rarely true and that the pattern varies among taxonomic or ecological subsets of those communities. Energetic considerations may only be relevant to the densities of more abundant species. In fact, within natural assemblages o f organisms, the underlying relationship is very variable; in subsets of those assemblages, ecological processes such as competition may structure abundance patterns.     

The macroevolutionary relationship between diet and body mass across mammals

Body mass and diet are two fundamental ecological parameters that influence many other aspects of an animal's biology. Thus, the potential physiological and ecological processes linking size and diet have been the subject of extensive research, although the broad macroevolutionary relationship between the two traits remains largely unexplored phylogenetically. Using generalized Ornstein–Uhlenbeck models and data on over 1350 species of mammal, we reveal that evolutionary changes in body mass are consistently associated with dietary changes across mammals. Best‐fitting models find that herbivores are substantially heavier than other dietary groups and that omnivores are frequently intermediate in mass between herbivores and carnivores. Interestingly, although flying and swimming both place very different physical constraints on mass, bats still follow the general mammalian pattern but marine mammals do not. Such differences may be explained by reduced gravitational constraints on size in water along with ecological differences in food availability between aquatic and terrestrial realms, allowing marine carnivores to become the largest mammals on earth. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115 , 173–184.