Relative Body Size Research Articles

Limited effects of management and ecological subsidies on the size-spectra of kelp forest fish communities

Animal body size influences key ecological processes across biological hierarchies. For instance, densities (N) and community biomass (B) are allometric functions of body mass (M). Energetic equivalence predicts that density scales with body size as N ∝ M-0.75 and that biomass scales with body size as B ∝ M0.25. However, the way fish size-spectra are influenced by external processes, such as ecological subsidies (e.g. nutrients from upwelling zones) and fisheries management, is not well understood. We investigated the relationship of body size with density and biomass of reef fishes associated with subtidal kelp forests of Lessonia trabeculata that were influenced by the separate and interactive effects of management (Territorial Use Rights for Fisheries [TURF] or open access) and upwelling regimes (upwelling or non-upwelling zones). Fish densities and lengths were recorded using underwater visual censuses. Within each of 4 locations, paired TURF and open-access sites were surveyed. We surveyed 18 fish species, encompassing 1511 individuals ranging between 2 and 6639 g. We observed that fish size-spectra deviated from energetic equivalence, as N ∝ M-0.32 and B ∝ M2.2, indicating that the contribution of large-sized fishes to community density and biomass was greater than that predicted by energetic equivalence. Multi-model inference suggested that TURF and upwelling scenarios had weak effects on fish size-spectra. Results indicated that fish communities may have access to external food sources beyond local kelp forests. In addition, size-spectra may be a spatially persistent attribute of these fish communities.

Life-history traits of Aedes aegypti (Linnaeus) distributed across a latitudinal range of 23 °N-6 °S.

The growth and associated traits of Aedes aegypti (L.) mosquitoes may adapt and evolve in response to the costs associated with body size in relation to latitudinal variation. We analyzed the life-history traits and energy reserves of field-collected mosquitoes from Taiwan, Thailand, and Indonesia along a latitudinal range spanning from 23°N to 6°S. A U-shaped relationship between body size and latitude was observed. Our study demonstrated the role of latitudinal temperature variations in determining the body size patterns of Ae. aegypti. Notably, the body size of the northern populations (from Taiwan) was significantly larger than those of the tropical populations from Thailand and Indonesia. Models have demonstrated that regional precipitation levels may contribute to body trait variations in certain high-latitude populations in Thailand. However, Indonesian populations have high development rates and large body sizes, indicating the involvement of other physiological traits in determining mosquito body size. The reproductive output of the adult females in this study was positively correlated with body size, but our measure of longevity did not covary significantly with the body size. By contrast, the reproductive output of mosquito-tested populations was in inverse proportion to longevity. Additionally, the mean teneral glycogen levels in the Indonesian and Thai populations were 2.5 times higher than those in the Taiwanese populations. The Indonesian and Thai populations had low mean generation and doubling times, resulting in a high intrinsic rate of increase compared with that of the Taiwanese populations, despite the Taiwanese populations having the highest net reproduction rate.

Broad-scale perspective on body size-trophic position patterns of freshwater fishes at the intraspecific and community levels from individual-based data in China

As predators are generally larger than their prey, positive body size and trophic position relationships are typically assumed, and these relationships have helped in estimating and predicting the effects of global environmental change on the trophic dynamics of aquatic ecosystems. However, current efforts to confirm the generality of body size-trophic position relationships have focused mainly on interspecific patterns using species-aggregated and averaged data, and little effort has been devoted to assessing how trophic position scales with body size at the intraspecific and community levels as well as exploring its ecological drivers, particularly for fishes in freshwater ecosystems. To fill this gap, we present a broad-scale study of body size-trophic position relationships in freshwater ecosystems at both the intraspecific and community levels using an individual-based body size and isotopic signature dataset that includes 2564 samples of 65 fish species in China. Our results indicate that body size-trophic position patterns at both the intraspecific and community levels can be positive, negative or insignificant. Non-significant patterns predominated at both levels, with slightly more than 30 % showing positive relationships, which highlights that the positive body size-trophic position pattern is not universally prevalent and that body size should be used with caution as a proxy for the trophic position of fishes at both the intraspecific and community levels in freshwater ecosystems. No factor was related to body size-trophic position patterns at the community level, while habitat type, elevation, temperature and fishing pressure were identified as the key determinants of body size-trophic position patterns at the intraspecific level, implying that fishing and climate warming can shift the food-web size structure of freshwater ecosystems by affecting population trophic dynamics.

Otolith morphometry and body size relationships of Rasborine fishes in Ganga River water

Otolith morphometry and body size relationships of Rasborine fishes in Ganga River water

More laws for pauses: Replication and generalization.

The basic timescales governing animal life are generally determined by body size. Pauses in naturally occurring human speech were investigated to determine if pause timescales are also sensitive to body size. Reported is an analysis of pause duration allometry in recorded interviews of 61 athletes. Pauses were divided into three classes based on whether they occurred during fluid speech or whether they preceded or followed a filled pause (i.e., "um"). Allometric laws relating body size to pause size were found for all three classes-larger people take longer pauses. The derived allometric exponents were used to evaluate a theory of how people experience the passage of time. The theory associates the experience of time passage with the distal flow of time through the mathematics of bounded exponential growth. Nonlinearities inherent in the theory are shown to predict, in detail, the way body size interacts with linguistic context in the deployment of pauses. The theory provides a meaningful framework for understanding how time is experienced as a felt quantity and how pauses are negotiated in everyday speech. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Relationships among development, growth, body size, reproduction, aging, and longevity - trade-offs and pace-of-life

Relationships of growth, metabolism, reproduction, and body size to the biological process of aging and longevity have been studied for decades and various unifying “theories of aging” have been proposed to account for the observed associations. In general, fast development, early sexual maturation leading to early reproductive effort, as well as production of many offspring, have been linked to shorter lifespans. The relationship of adult body size to longevity includes a remarkable contrast between the positive correlation in comparisons between different species and the negative correlation seen in comparisons of individuals within the same species. We now propose that longevity and presumably also the rate of aging are related to the “pace-of-life.” A slow pace-of-life including slow growth, late sexual maturation, and a small number of offspring, predicts slow aging and long life. The fast pace of life (rapid growth, early sexual maturation, and major reproductive effort) is associated with faster aging and shorter life, presumably due to underlying trade-offs. The proposed relationships between the pace-of-life and longevity apply to both inter- and intra-species comparisons as well as to dietary, genetic, and pharmacological interventions that extend life and to evidence for early life programming of the trajectory of aging. Although available evidence suggests the causality of at least some of these associations, much further work will be needed to verify this interpretation and to identify mechanisms that are responsible.

Perceived Body Size in Relation to 10-Year Weight Change in the Swedish Obese Subjects Intervention Study

Introduction: Body size underestimation in patients with obesity may be associated with long-term weight increase. In the current report, we analyse changes in body size perception in patients with obesity undergoing either bariatric surgery or usual obesity care, and in subgroups of patients who gain weight or maintain their body weight over 10 years. Materials and Methods: A total of 2,504 patients with obesity from the prospective, controlled Swedish Obese Subjects (SOS) intervention study were included in this report, 1,370 patients underwent bariatric surgery and 1,134 patients were usual care controls. Weight was measured and body size was self-estimated using the Stunkard’s figure rating scale at baseline and after 0.5, 1, 2, 3, 4, 6, 8 and 10 years of follow-up. A body perception index (BPI) was calculated as estimated/measured BMI. Weight (re)gain was defined as ≥10% increase between 1 and 10 years of follow-up. Results: Body size was underestimated by 12% in the surgery and 14% in the control group (i.e., >5 BMI units) at baseline and underestimation largely persisted over 10 years in both intervention groups. When stratified by long-term weight development, weight regainers from the surgery group underestimated their body size to a larger degree compared to weight maintainers (12 vs. 9%, p < 0.001) after 10 years. Likewise weight gainers in the control group also underestimated their body size to a larger degree (17% vs. 13%, p < 0.001). In both groups, the change in BPI was significantly different between weight regainers and maintainers during follow-up (time-BPI interactions both p < 0.001). Conclusion: Patients with obesity underestimate their body size and this underestimation remains long-term even after major weight loss induced by bariatric surgery. In patients with obesity who maintain their weight, regardless of treatment, underestimation of body size persists but body size perception is slightly more accurate compared to patients who gain or regain weight long-term.

Improving the biological realism of predator-prey size relationships in food web models alters ecosystem dynamics.

Body-size relationships between predators and prey exhibit remarkable diversity. However, the assumption that predators typically consume proportionally smaller prey often underlies size-dependent predation in ecosystem models. In reality, some animals can consume larger prey or exhibit limited changes in prey size as they grow larger themselves. These distinct predator-prey size relationships challenge the conventional assumptions of traditional size-based models. Cephalopods, with their diverse feeding behaviours and life histories, offer an excellent case study to investigate the impact of greater biological realism in predator-prey size relationships on energy flow within a size-structured ecosystem model. By categorizing cephalopods into high and low-activity groups, in line with empirically derived, distinct predator-prey size relationships, we found that incorporating greater biological realism in size-based feeding reduced ecosystem biomass and production, while simultaneously increasing biomass stability and turnover. Our results have broad implications for ecosystem modelling, since distinct predator-prey size relationships extend beyond cephalopods, encompassing a wide array of major taxonomic groups from filter-feeding fishes to baleen whales. Incorporating a diversity of size-based feeding in food web models can enhance their ecological and predictive accuracy when studying ecosystem dynamics.

Mechanisms of increasing predation by planktivorous fish with rising temperature may explain the temperature–body size relationships in zooplankton

The temperature–size rule (TSR) has been consistently observed in numerous studies, showing that ectotherms reared at higher temperatures experience accelerated growth during the juvenile stage and ultimately reach smaller sizes and younger ages at maturity. One explanation for this response is that it occurs when the effect of temperature on mortality, including predation, outweighs its effect on food intake and metabolism. While several studies have found that the latter effect is close to the expected result based on the Q10 = 2 assumption, confirmation of this hypothesis requires evidence that the effect of temperature on mortality exceeds the Q10 = 2 threshold. To test this hypothesis, we conducted experiments with two fish species: rudd and Malabar danio. We examined the capture rate, which serves as a proxy for mortality, as well as the standard metabolic rate (SMR) and several parameters characterising the mobility of the fish and their planktonic prey (Daphnia) at different temperatures. The results strongly supported our hypothesis, as the capture rate increased significantly more than expected based on the Q10 = 2 assumption, especially for the danio. This substantial effect cannot be attributed solely to the thermal sensitivity of the SMR, as the Q10 for the SMR was only around 2. The most likely explanation seems to be a much more pronounced increase in the fish’s mobility and resulting reaction field volume compared to its planktonic prey at elevated temperatures. This increased mobility leads to an improved attack rate by the fish, which exceeds the prediction made by the Q10 = 2 assumption. This mechanism may explain not only the TSR pattern in zooplankton, but also their reduced mean body size and density at population and community levels at elevated temperatures, and may hypothetically be observed at other predator–prey interfaces.

Lenstar LS900 vs EchoScan US-800: comparison between optical and ultrasound biometry with and without contact lenses and its relationship with other biometric parameters

ABSTRACT Background Due to the increasing use of contact lenses (CL) and the interest in ocular and body size relationships, this study aimed to compare measurements from two biometers (contact ultrasonic EchoScan US-800 and non-contact optical Lenstar LS900) with and without CL and to explore the relationship between ocular and body biometric parameters. Design and Methods This cross-sectional study measured ocular biometry using two biometers along with their body height and right foot length in 50 participants. Differences between biometry data from the two devices were compared and correlations between ocular and body biometric values were analyzed. Results All parameters showed interbiometric differences (p ≤ 0.030), except crystalline lens thickness during CL wear (p = 0.159). Comparing measurements with and without CL, differences were observed in axial length (p < 0.001), vitreous length measured by optical biometer (p = 0.016), and anterior chamber depth by ultrasonic biometer (p < 0.016). Lens thickness remained unaffected (p ≥ 0.190). Body height and foot length were correlated with anterior chamber depth, vitreous length, and axial length (p ≤ 0.019, r ≥ 0.330). Most biometric parameters were correlated among them using both devices (p ≤ 0.037, r ≥ 0.296). Conclusions These biometers are not interchangeable and CL affects measurements. Body height and foot length correlate with ocular dimensions, and most ocular biometric values correlate positively.

Variation in Relative Abundance, Population Structure, and Body Size of the Suwannee Alligator Snapping Turtle (Macrochelys suwanniensis) in the Suwannee River

Geological processes influence water chemistry and biological productivity along the Suwannee River and divide the mainstem of the river into 6 distinct ecological reaches (ERs) in Florida. Because of these distinctions, we hypothesized that the Macrochelys suwanniensis (Suwannee Alligator Snapping Turtle) population varies among ERs. During 2011–2013, we sampled two 5-km sites in each ER to investigate spatial variation in relative abundance, sex ratio, size-class distribution, and body size of M. suwanniensis. Capture rates and male body sizes were greater in the middle ERs than in the upstream and downstream ERs. Sex ratios were male-skewed only in the middle ERs. Additional research is needed to understand the ecological drivers of M. suwanniensis population dynamics in this river.

Island and Rensch’s rules do not apply to cave vs. surface populations of Asellus aquaticus

Body size is a trait of fundamental ecological and evolutionary importance that is often different between males and females (sexual size dimorphism; SSD). The island rule predicts that small-bodied species tend to evolve larger following a release from interspecific competition and predation in insular environments. According to Rensch’s rule, male body size relative to female body size increases with increasing mean body size. This allometric body size – SSD scaling is explained by male-driven body size evolution. These ecogeographical rules are rarely tested within species, and has not been addressed in a cave–surface context, even though caves represent insular environments (small and isolated with simple communities). By analyzing six cave and nine surface populations of the widespread, primarily surface-dwelling freshwater isopod Asellus aquaticus with male-biased SSD, we tested whether cave populations evolved larger and showed higher SSD than the surface populations. We found extensive between-population variation in body size (maximum divergence being 74%) and SSD (males being 15%–50% larger than females). However, habitat type did not explain the body size and SSD variation and we could not reject isometry in the male–female body size relationship. Hence, we found no support for the island or Rensch’s rules. We conclude that local selective forces stemming from environmental factors other than island vs. mainland or the general surface vs. cave characteristics are responsible for the reported population variation.

Body size in relation to rotifer abundance underestimation using a net of large mesh size in a tropical reservoir

Body size in relation to rotifer abundance underestimation using a net of large mesh size in a tropical reservoir

41 A preliminary investigation of candidate genes from a GWAS identified QTL for relative body size in the American Quarter Horse

Artificial selection during domestication has influenced an array of morphological traits in the horse, many that are now important economic traits for the horse industry. Growth and skeletal phenotypes impact the desirability and function of horses in diverse disciplines and are often key characteristics in the development of breeds. Skeletal traits also impact functionality: benefitting horses for specialized work or predisposing them to musculoskeletal injury. To investigate variations in body size and shape, we utilized measurements taken at 2 years of age (+/− one week) from 91 American Quarter Horses bred and owned by the University of Florida. We summarized 32 body measures from each horse using a principal component analysis followed by a varimax rotation. Factor 1 summarizes 19.5% of the variation and describes overall body size, except for head measurements which are better captured in Factor 2. Factor 1 traits encompass body proportions, heavily loading on the measure's height at dock and croup. DNA was extracted from blood and hair through previously published methods and genotyped at GeneSeek Inc. (Lansing, MI) using the Affymetrix Axiom Equine HD 670k array. We recently reported results from a preliminary genome-wide association study with 311,085 high-quality SNPs (poly-high resolution, MAF >0.05)suggesting a quantitative trait locus for the Body Factor 1 trait on chromosome 6 (raw P = 1.356e-09, Bonferroni P = 4.51e-07) and defines a candidate region spanning 1.5Mb. The QTL is in a region unrelated to a previously characterized HMGA2 body height locus. The candidate region contains 5 protein-coding genes, influencing human height and skeletal traits including one associated with Noonan Syndrome- a disease impacting height and facial morphology, an interesting parallel to the phenotype observed in our population. None of the 16,860 variants found in the European Nucleotide Archive for our candidate region had a functional impacted on a protein coding region. Therefore, we sequenced 2 whole genomes from American Quarter Horses to discover variants specific to the haplotype bearing this new body size QTL. Using the 10x Chromium library prep with 150bp paired end reads on an Illumina HiSeq2500, the 2 genomes totaled 1.5 billion reads. Following alignment and variant calling using the LongRanger package (v2.2, 10x Genomics Inc.), we observed 4,703 SNPs in the candidate region. Future investigation aims to investigate additional loci relevant to body morphological variations and develop predictive phenotype models in the horse.

Assessing the interactions of variables affecting the rate of nonhuman decomposition

Decomposition of organic tissue is a complex process that is affected by a large number of interactions. These variables affect the rate of decomposition, insect activity, and the onset of each individual stage in the decomposition process. Of the variables in effect, some of the most commonly studied are temperature and moisture. The purpose of this study is to analyze the impact of other variables, such as age at death, body size, sun exposure, and presence of preservation chemicals on the rate of decomposition in nonhuman specimens. The goal of this research is to give more insight into the complex interactions between these variables and analyze the reliability of current decomposition analysis. As ethical considerations and policies affect how researchers use human remains, more decomposition research is needed to better understand this very sensitive process and all the variables that are included. Preliminary results suggest that sun exposure, relative body size, and age at death do not significantly affect the rate of nonhuman decomposition, but a principal component analysis suggests correlation does exist between subsets of these variables. Ongoing work to include larger sample sizes, as well as chemically preserved animals, is currently running. Expected results indicate that preserved animals will take longer to fully decompose, and the effects of age, sun exposure, and body size will not be significant.&#x0D;  

Climate Change, Extreme Temperatures and Sex-Related Responses in Spiders.

Climatic extremes, such as heat waves, are increasing in frequency, intensity and duration under anthropogenic climate change. These extreme events pose a great threat to many organisms, and especially ectotherms, which are susceptible to high temperatures. In nature, many ectotherms, such as insects, may seek cooler microclimates and 'ride out´ extreme temperatures, especially when these are transient and unpredictable. However, some ectotherms, such as web-building spiders, may be more prone to heat-related mortality than more motile organisms. Adult females in many spider families are sedentary and build webs in micro-habitats where they spend their entire lives. Under extreme heat, they may be limited in their ability to move vertically or horizontally to find cooler microhabitats. Males, on the other hand, are often nomadic, have broader spatial distributions, and thus might be better able to escape exposure to heat. However, life-history traits in spiders such as the relative body size of males and females and spatial ecology also vary across different taxonomic groups based on their phylogeny. This may make different species or families more or less susceptible to heat waves and exposure to very high temperatures. Selection to extreme temperatures may drive adaptive responses in female physiology, morphology or web site selection in species that build small or exposed webs. Male spiders may be better able to avoid heat-related stress than females by seeking refuge under objects such as bark or rocks with cooler microclimates. Here, we discuss these aspects in detail and propose research focusing on male and female spider behavior and reproduction across different taxa exposed to temperature extremes.

Stowaways: Maritime ecology of the oldest commensal ship rats (Rattus rattus) found on a Mediterranean shipwreck

Ship rats (Rattus rattus) have successfully colonized six continents and 80% of islands worldwide by stowing-away on anthropogenic vessels. Numerous zooarchaeological and metagenomic studies have contributed to tracing the western dispersal of ship rats out of the Indian subcontinent and into the Mediterranean Basin, North Africa, and Europe. This has increased understanding of historical maritime mobility, trade contacts, and the spread of pandemic disease such as the plague. Moreover, considerable research has been conducted on the behavior, ecology, and population dynamics of ship rats in invaded areas, which supports conservation and eradication efforts. However, few studies have shed light on the mode of travel in between the geographic origins and destinations of ship rats, such as ships and boats, which act as mobile, commensal habitat for this cosmopolitan species. We address this lacuna here, by analyzing an assemblage of ship rat remains from an early Islamic period shipwreck, the Ma‘agan Mikhael B, located on the Carmel coast of modern Israel. Using zooarchaeological, biometrical, and palaeogenetic (aDNA) methodologies, we investigated the maritime ecology of ship rats regarding dispersal behavior, habitat selection, source–sink dynamics, and relative body size. The results of this study suggest that ship rats actively inhabited the Ma‘agan Mikhael B as part of their habitat selection processes, that conditions onboard provided high-quality habitat (adequate food and harborage, likely absence of predators and disease), and that they appear to have exhibited a degree of gigantism, possibly due to ‘island rule’. This study has implications for future metapopulation genetic studies on ship rats, as well as shows the value of zooarchaeological analysis in understanding the ecological circumstances of the maritime mobility of ship rats in the Mediterranean region.

Concordant Spatial Gradients in Predation Intensity and Productivity Archived in Surficial Mollusk Shell Accumulations in Seagrass Meadows Along the Gulf Coast of Florida

Seagrass meadows are highly structured habitats of great socioeconomic value but are declining globally due to human impacts. The northern Gulf Coast of Florida contains one of the largest relatively unaltered seagrass habitats (~3,000 km2), making it a model system for acquiring baselines to better manage and monitor seagrass meadows. This project investigated spatial gradients in ecological and taphonomic attributes of surficial seagrass-associated benthic mollusk death assemblages. An updated analysis of water parameters (based on project COAST data) indicated that total dissolved phosphorous (TDP) and chlorophyll-a (CHL-a) concentrations increased steadily northward. To analyze the historical ecology of local seagrass meadows, mollusk assemblages were bulk sampled at 12 stations across multiple estuaries along the gradient. Radiocarbon dating of valves (n = 90) from several estuaries indicated that the assemblages represented a multi-millennial accumulation with a median shell age of 1760 AD. Focusing on two abundant bivalves found within all estuaries, Transennella spp and Crassostrea virginica, the study evaluated spatial trends in body size, traces of predation, and post-mortem shell alterations. The results, primarily focused on Transennella spp., indicated that ecological and taphonomic characteristics varied notably, both among and within estuaries. Relative abundance, body size, and taphonomic attributes did not appear to correlate significantly with productivity or drilling frequency. However, drilling frequency correlated significantly with TDP and CHL-a, suggesting that predator-prey interactions may co-vary tightly with productivity. These results suggest that spatial gradients in predation can be archived by drilling frequencies in death assemblages. Moreover, the consistency between the long-term record of predation and modern gradient conditions suggests that long-term spatial dynamics of predator-prey interactions may be hydrologically controlled.

New occurrences of the endangered Notholebias minimus (Cyprinodontiformes: Rivulidae) in coastal plains of the State of Rio de Janeiro, Brazil: populations features and conservation

Abstract Notholebias minimus is an endangered annual killifish endemic to the coastal plains of the State of Rio de Janeiro, Brazil. This study aimed to present new occurrences in the Atlantic Forest biome, provide unprecedented population features (body and egg size, fecundity, sexual ratio, and length-weight relationship – LWR), and compare changes in land use and coverage between 1985 and 2021 in biotopes located inside and outside protected areas. Three new occurrence localities were found in shallow temporary wetlands with acidic pH (6.4 ± 0.2) and low concentrations of dissolved oxygen (2.0 ± 0.9 mg/L). Males and females total length ranged from 11.1 to 31 mm and 11 to 26 mm, respectively. Batch fecundity ranged from 18 to 40 oocytes (24.8 ± 8.8), corresponding to oocytes with sizes between 800–1,006 µm (905 ± 56). Males were significantly larger than females (W = 2193.5, p = 0.0067), but both sexes occurred in similar proportions (p = 0.472). LWR showed positive allometry (b = 3.18). Biotopes located within protected areas exhibited higher conservation. Our discoveries expand the knowledge about habitat and population features of N. minimus and reinforce the importance of establishing protected areas for the conservation of annual fish biotopes.

Relative Body Size Relationship to Proximate Composition of Farmed Hypophthalmichthys nobilis from Bahawalnagar, Pakistan

Relative Body Size Relationship to Proximate Composition of Farmed Hypophthalmichthys nobilis from Bahawalnagar, Pakistan