Relative Body Size Research Articles

A field and video annotation guide for baited remote underwater stereo‐video surveys of demersal fish assemblages

Abstract Baited remote underwater stereo‐video systems (stereo‐BRUVs) are a popular tool to sample demersal fish assemblages and gather data on their relative abundance and body size structure in a robust, cost‐effective and non‐invasive manner. Given the rapid uptake of the method, subtle differences have emerged in the way stereo‐BRUVs are deployed and how the resulting imagery is annotated. These disparities limit the interoperability of datasets obtained across studies, preventing broadscale insights into the dynamics of ecological systems. We provide the first globally accepted guide for using stereo‐BRUVs to survey demersal fish assemblages and associated benthic habitats. Information on stereo‐BRUVs design, camera settings, field operations and image annotation are outlined. Additionally, we provide links to protocols for data validation, archiving and sharing. Globally, the use of stereo‐BRUVs is spreading rapidly. We provide a standardized protocol that will reduce methodological variation among researchers and encourage the use of Findable, Accessible, Interoperable and Reusable workflows to increase the ability to synthesize global datasets and answer a broad suite of ecological questions.

Relationship of self-reported body size and shape with risk for prostate cancer: A UK case-control study.

IntroductionPrevious evidence has suggested a relationship between male self-reported body size and the risk of developing prostate cancer. In this UK-wide case-control study, we have explored the possible association of prostate cancer risk with male self-reported body size. We also investigated body shape as a surrogate marker for fat deposition around the body. As obesity and excessive adiposity have been linked with increased risk for developing a number of different cancers, further investigation of self-reported body size and shape and their potential relationship with prostate cancer was considered to be appropriate.ObjectiveThe study objective was to investigate whether underlying associations exist between prostate cancer risk and male self-reported body size and shape.MethodsData were collected from a large case-control study of men (1928 cases and 2043 controls) using self-administered questionnaires. Data from self-reported pictograms of perceived body size relating to three decades of life (20’s, 30’s and 40’s) were recorded and analysed, including the pattern of change. The associations of self-identified body shape with prostate cancer risk were also explored.ResultsSelf-reported body size for men in their 20’s, 30’s and 40’s did not appear to be associated with prostate cancer risk. More than half of the subjects reported an increase in self-reported body size throughout these three decades of life. Furthermore, no association was observed between self-reported body size changes and prostate cancer risk. Using ‘symmetrical’ body shape as a reference group, subjects with an ‘apple’ shape showed a significant 27% reduction in risk (Odds ratio = 0.73, 95% C.I. 0.57–0.92).ConclusionsChange in self-reported body size throughout early to mid-adulthood in males is not a significant risk factor for the development of prostate cancer. Body shape indicative of body fat distribution suggested that an ‘apple’ body shape was protective and inversely associated with prostate cancer risk when compared with ‘symmetrical’ shape. Further studies which investigate prostate cancer risk and possible relationships with genetic factors known to influence body shape may shed further light on any underlying associations.

Do body mass and habitat factors predict trophic position in temperate stream fishes?

In animals with indeterminate growth, such as predatory fishes, mouth size is related to, and increases with, body mass of the organism. As fishes grow in body size, they can consume larger-bodied prey items at potentially-higher trophic levels. Therefore, body size should predict trophic position. Trophic position (TP) is useful for describing energy flow between biota, giving a more comprehensive picture of aquatic food webs, but the factors that influence the body-size–TP relationship are unclear. Additionally, stable isotope-derived TP and body-size relationships are untested for temperate freshwater fishes. Using linear mixed-effects models, we tested fish body mass as a predictor of TP across 6 species of temperate freshwater fish (n = 921 total individuals) sampled from 110 stream reaches in New Zealand, and we evaluated habitat factors (flood disturbance and stream size) likely to affect trophic structure of stream fish assemblages. Supporting ecological theory, but contrasting with some previous findings in marine and tropical environments, we found that TP was positively associated with body size across all species. Habitat factors did not affect fish TP. However, stream network spatial factors included in models as random effects explained the majority of variance in TP across species. Thus, while our study shows that New Zealand temperate freshwater fish body size is positively associated with stable isotope-derived TP, researchers will need to account for catchment-specific spatial factors to make accurate inferences about TP based on body size.

Growth parameter k and location affect body size responses to spatial protection by exploited rockfishes.

For many fish taxa, trophic position and relative fecundity increase with body size, yet fisheries remove the largest individuals, altering food webs and reducing population productivity. Marine reserves and other forms of spatial protection can help mitigate this problem, but the effectiveness of these management tools may vary interspecifically and spatially. Using visual survey data collected on the Central Coast of British Columbia, for 12 species of exploited rockfish we found that body size responses to spatial fishery closures depended on interspecific variation in growth parameter k (the rate at which the asymptotic body size is approached) and on location. For two closures, relative body sizes were larger at protected than at adjacent fished sites, and these differences were greater for species with lower k values. Reduced fishery mortality likely drove these results, as an unfished species did not respond to spatial protection. For three closures, however, body sizes did not differ between protected and adjacent fished sites, and for another closure species with higher k values were larger at fished than at protected sites while species with lower k values had similar sizes in both treatments. Variation in the age of closures is unlikely to have influenced results, as most data were collected when closures were 13 to 15-years-old. Rather, the lack of larger fish inside four of six spatial fishery closures potentially reflects a combination of smaller size of the area protected, poor fisher compliance, and lower oceanographic productivity. Interspecific differences in movement behavior did not affect body size responses to spatial protection. To improve understanding, additional research should be conducted at deeper depths encompassing the distribution of older, larger fish. Our study—which was conceptualized and executed by an alliance of Indigenous peoples seeking to restore rockfishes—illustrates how life history and behavioral theory provide a useful lens for framing and interpreting species differences in responses to spatial protection.

Body size in relation to cubicle dimensions affects lying behavior and joint lesions in dairy cows

Adequate cubicle dimensions are important for dairy cows to allow for species-appropriate lying behavior. Even though cow body size has increased in the last 2 decades, the cubicle dimensions of housing systems built many years ago have not been adjusted on most farms. Therefore, cows may be impaired in their lying behaviors, and thus the present study aimed to determine the influence of the ratio of body size to cubicle dimension on lying behavior and joint lesions. We investigated the lying behavior of 144 cows with withers heights of 140 to 163 cm on 8 Swiss dairy farms. Among the farms, the cubicle bed length varied from 187 to 200 cm and lunge space length varied from 47 to 202 cm. Specific behaviors of lying down and standing up movements, as well as lying positions, were observed on 3 d per farm. As outcome variables, the occurrences of these behaviors were calculated as proportions in relation to the respective total number of observations per cow. In addition, the presence of joint lesions was scored once. Data of the individual cows were analyzed in relation to the given cubicle dimensions on the farms by mixed-effects models. The bed length ratio [bed length (cm) on the farm/withers height (cm) of the observed cow] and the lunge space ratio [lunge space length (cm) on the farm/withers height (cm) of the observed cow] were used as explanatory variables. An increase in the bed length ratio was associated with decreased proportions of lying down movements with (1) repeated head pendulum movements, (2) repeated stepping with front legs, and (3) hitting against cubicle elements; decreased proportions of standing up movements with (1) shifting backward, (2) hesitant head lunge movements, and (3) hitting against cubicle elements; and an increased proportion of lying positions without physical contact with cubicle elements. An increase in the lunge space ratio was associated with a decreased proportion of standing up movements with sideways directed head lunge movements. Furthermore, an increase in the bed length ratio decreased the proportion of cows with tarsal joint lesions. To summarize, the lying behavior of large-framed cows was clearly modified given the cubicle dimensions in use on the study farms. In view of the consistency of the obtained results, we recommend adjusting the dimensions of cubicles so that they are suitable for cows whose body size meets the breeding goals of the farm.

Allometric scaling law and ergodicity breaking in the vascular system

Allometry or the quantitative study of the relationship of body size to living organism physiology is an important area of biophysical scaling research. The West-Brown-Enquist (WBE) model of fractal branching in a vascular network explains the empirical allometric Kleiber law (the ¾ scaling exponent for metabolic rates as a function of animal’s mass). The WBE model raises a number of new questions, such as how to account for capillary phenomena more accurately and what are more realistic dependencies for blood flow velocity on the size of a capillary. We suggest a generalized formulation of the branching model and investigate the ergodicity in the fractal vascular system. In general, the fluid flow in such a system is not ergodic, and ergodicity breaking is attributed to the fractal structure of the network. Consequently, the fractal branching may be viewed as a source of ergodicity breaking in biophysical systems, in addition to such mechanisms as aging and macromolecular crowding. Accounting for non-ergodicity is important for a wide range of biomedical applications where long observations of time series are impractical. The relevance to microfluidics applications is also discussed.

Dominance rank but not body size influences female reproductive success in mountain gorillas.

According to life history theory, natural selection has shaped trade-offs for allocating energy among growth, reproduction and maintenance to maximize individual fitness. In social mammals body size and dominance rank are two key variables believed to influence female reproductive success. However, few studies have examined these variables together, particularly in long-lived species. Previous studies found that female dominance rank correlates with reproductive success in mountain gorillas (Gorilla beringei beringei), which is surprising given they have weak dominance relationships and experience seemingly low levels of feeding competition. It is not currently known whether this relationship is primarily driven by a positive correlation between rank and body size. We used the non-invasive parallel laser method to measure two body size variables (back breadth and body length) of 34 wild adult female mountain gorillas, together with long-term dominance and demography data to investigate the interrelationships among body size, dominance rank and two measures of female reproductive success (inter-birth interval N = 29 and infant mortality N = 64). Using linear mixed models, we found no support for body size to be significantly correlated with dominance rank or female reproductive success. Higher-ranking females had significantly shorter inter-birth intervals than lower-ranking ones, but dominance rank was not significantly correlated with infant mortality. Our results suggest that female dominance rank is primarily determined by factors other than linear body dimensions and that high rank provides benefits even in species with weak dominance relationships and abundant year-round food resources. Future studies should focus on the mechanisms behind heterogeneity in female body size in relation to trade-offs in allocating energy to growth, maintenance and lifetime reproductive success.

Body size trends in response to climate and urbanization in the widespread North American deer mouse, Peromyscus maniculatus

Body size decline is hypothesized to be a key response to climate warming, including warming driven by urban heat islands. However, urbanization may also generate selective gradients for body size increases in smaller endotherms via habitat fragmentation. Here we utilize a densely sampled, multi-source dataset to examine how climate and urbanization affect body size of Peromyscus maniculatus (PEMA), an abundant rodent found across North America. We predicted PEMA would conform to Bergmann’s Rule, e.g. larger individuals in colder climates, spatially and temporally. Hypotheses regarding body size in relation to urbanization are less clear; however, with increased food resources due to greater anthropogenic activity, we expected an increase in PEMA size. Spatial mixed-models showed that PEMA conform to Bergmann’s Rule and that PEMA were shorter in more urbanized areas. With the inclusion of decade in mixed-models, we found PEMA mass, but not length, is decreasing over time irrespective of climate or population density. We also unexpectedly found that, over time, smaller-bodied populations of PEMA are getting larger, while larger-bodied populations are getting smaller. Our work highlights the importance of using dense spatiotemporal datasets, and modeling frameworks that account for bias, to better disentangle broad-scale climatic and urbanization effects on body size.

Influence of intra- and interspecific variation in predator-prey body size ratios on trophic interaction strengths.

Predation is a pervasive force that structures food webs and directly influences ecosystem functioning. The relative body sizes of predators and prey may be an important determinant of interaction strengths. However, studies quantifying the combined influence of intra‐ and interspecific variation in predator–prey body size ratios are lacking.We use a comparative functional response approach to examine interaction strengths between three size classes of invasive bluegill and largemouth bass toward three scaled size classes of their tilapia prey. We then quantify the influence of intra‐ and interspecific predator–prey body mass ratios on the scaling of attack rates and handling times.Type II functional responses were displayed by both predators across all predator and prey size classes. Largemouth bass consumed more than bluegill at small and intermediate predator size classes, while large predators of both species were more similar. Small prey were most vulnerable overall; however, differential attack rates among prey were emergent across predator sizes. For both bluegill and largemouth bass, small predators exhibited higher attack rates toward small and intermediate prey sizes, while larger predators exhibited greater attack rates toward large prey. Conversely, handling times increased with prey size, with small bluegill exhibiting particularly low feeding rates toward medium–large prey types. Attack rates for both predators peaked unimodally at intermediate predator–prey body mass ratios, while handling times generally shortened across increasing body mass ratios.We thus demonstrate effects of body size ratios on predator–prey interaction strengths between key fish species, with attack rates and handling times dependent on the relative sizes of predator–prey participants.Considerations for intra‐ and interspecific body size ratio effects are critical for predicting the strengths of interactions within ecosystems and may drive differential ecological impacts among invasive species as size ratios shift.

A Tale of Winglets: Evolution of Flight Morphology in Stick Insects

Author(s): Zeng, Yu; O'Malley, Connor; Singhal, Sonal; Rahim, Faszly; Park, Sehoon; Chen, Xin; Dudley, Robert | Abstract: The evolutionary transition between winglessness and a full-winged morphology requires selective advantage for intermediate forms. Conversely, repeated secondary wing reductions among the pterygotes indicates relaxation of such selection. However, evolutionary trajectories of such transitions are not well-characterized. The stick insects (Phasmatodea) exhibit diverse wing sizes at both interspecific and intersexual levels, and thus provide a system for examining how selection on flight capability, along with other selective forces, drives the evolution of flight-related morphology. Here, we examine variation in relevant morphology for stick insects using data from 1,100+ individuals representing 765 species. Although wing size varies along a continuous spectrum, taxa with either long or miniaturized wings are the most common, whereas those with intermediate-sized wings are relatively rare. In a morphological space defined by wing and body size, the aerodynamically relevant parameter termed wing loading (the average pressure exerted on the air by the wings) varies according to sex-specific scaling laws; volant but also flightless forms are the most common outcomes in both sexes. Using phylogenetically-informed analyses, we show that relative wing size and body size are inversely correlated in long-winged insects regardless of sexual differences in morphology and ecology. These results demonstrate the diversity of flight-related morphology in stick insects, and also provide a general framework for addressing evolutionary coupling between wing and body dimensions. We also find indirect evidence for a “fitness valley” associated with intermediate-sized wings, suggesting relatively rapid evolutionary transitions between wingless and volant forms.

Variation in body size and sexual size dimorphism in the most widely ranging lizard: testing the effects of reproductive mode and climate.

Reproductive mode, ancestry, and climate are hypothesized to determine body size variation in reptiles but their effects have rarely been estimated simultaneously, especially at the intraspecific level. The common lizard (Zootoca vivipara) occupies almost the entire Northern Eurasia and includes viviparous and oviparous lineages, thus representing an excellent model for such studies. Using body length data for >10,000 individuals from 72 geographically distinct populations over the species' range, we analyzed how sex‐specific adult body size and sexual size dimorphism (SSD) is associated with reproductive mode, lineage identity, and several climatic variables. Variation in male size was low and poorly explained by our predictors. In contrast, female size and SSD varied considerably, demonstrating significant effects of reproductive mode and particularly seasonality. Populations of the western oviparous lineage (northern Spain, south‐western France) exhibited a smaller female size and less female‐biased SSD than those of the western viviparous (France to Eastern Europe) and the eastern viviparous (Eastern Europe to Far East) lineages; this pattern persisted even after controlling for climatic effects. The phenotypic response to seasonality was complex: across the lineages, as well as within the eastern viviparous lineage, female size and SSD increase with increasing seasonality, whereas the western viviparous lineage followed the opposing trends. Altogether, viviparous populations seem to follow a saw‐tooth geographic cline, which might reflect the nonmonotonic relationship of body size at maturity in females with the length of activity season. This relationship is predicted to arise in perennial ectotherms as a response to environmental constraints caused by seasonality of growth and reproduction. The SSD allometry followed the converse of Rensch's rule, a rare pattern for amniotes. Our results provide the first evidence of opposing body size—climate relationships in intraspecific units.

Foraging behaviour and diet in two sympatric shrike species during autumn migration across the Arabian Peninsula.

In situations of restricted food supply, the trophic niches of closely-related species of animals should be separate. For sit-and-wait hunters, such as shrikes, this is associated with competition for food and hunting sites. In the present study, the foraging behaviour of two shrike species – Red-tailed Shrike Lanius phoenicuroides and Red-backed Shrike Lanius collurio – was studied in a desert habitat in Oman. The fieldwork was carried out in September 2019, during the peak migration of these birds. Their behaviour was recorded in detail during 30-minute observation bouts. A General Linear Mixed Model with logit link function and binomial error variance was used to compare their behaviour. The type of perch and its height did not differ between them, but there were significant differences in their use of look-out posts only in the mean duration of a single perching event, which was more than twice as long in Red-backed Shrike. No differences in prey size were found between the species and hunting success (the ratio of successful attacks to all attacks) was similar in both (RtS-RbS: 46 vs. 61%). Dietary diversity was twice as great in Red-tailed Shrike as in Red-backed Shrike, but in general, their diets did not differ very much. Dietary overlap between the species at this level of prey identification was 92%. This absence of differences in some aspects of behaviour and diet may be due to the similarity of the two species, above all their same body size, and even the possibility of hybridization. If the species compared are so similar due to body size, behaviour and evolutionary relationship their food niches may overlap.

Virile crayfish escalate aggression according to body size instead of weapon size

Many crustaceans use their large claws to signal fighting ability during territorial contests. However, the size of a claw does not always reflect its strength or the bearer's ability to fight. If strength predicts the outcome of a fight, the mismatch between the size and strength of a claw creates dishonest signalling. Still, only a handful of species have been studied, leaving a gap in our knowledge of the taxonomic diversity and evolutionary history of dishonest signalling. To help fill this gap, we studied signalling and fighting between virile crayfish, Faxonius virilis. First, we measured the relationship between the size and strength of a claw in males and females. Then, we staged encounters between members of the same sex to determine how carapace length, claw size and claw strength influence the probability of fighting and the probability of winning. Both males and females possessed claws whose size poorly predicted their strength, especially at larger sizes. Unlike other species, which escalate aggression based on claw size, virile crayfish escalated aggression based on relative body size. When fighting occurred, however, both body size and claw strength determined the winner. Likely, virile crayfish ignore claw size because body size provides a more reliable signal of dominance. Our results stress the importance of observing behavioural dynamics in addition to functional relationships when studying the potential for dishonest signalling.

Elevational partitioning in species distribution, abundance and body size of Australian alpine grasshoppers (Kosciuscola)

AbstractChanges in the physical environment with elevation can influence species distributions and their morphological traits. In mountainous regions, steep temperature gradients can result in patterns of ecological partitioning among species that potentially increases their vulnerability to climate change. We collected data on species distributions, relative abundance and body size for three grasshopper species of the genus Kosciuscola (K. usitatus, K. tristis and K. cognatus) at three locations within the mountainous Kosciuszko National Park in Australia (Thredbo, Guthega and Jagungal). All three species showed differences in their distributions according to elevation, with K. usitatus ranging from 1400 to 2000 m asl, K. tristis from 1600 to 2000 m asl and K. cognatus from 1550 to 1900 m asl. Decreasing relative abundance with increasing elevation was found for K. usitatus, but the opposite pattern was found for K. tristis. The relative abundance of K. cognatus did not change with elevation but was negatively correlated with foliage cover. Body size decreased with elevation in both male and female K. usitatus, which was similarly observed in female K. tristis and male K. cognatus. Our results demonstrate spatial partitioning of species distributions and clines in body size in relation to elevational gradients. Species‐specific sensitivities to climatic gradients may help to predict the persistence of this grasshopper assemblage under climate change.

Silk Spinning Behavior Varies from Species-Specific to Individualistic in Embioptera: Do Environmental Correlates Account for this Diversity?

Abstract String sequence analysis revealed that silk spinning behavior of adult female Embioptera varies from species-specific to individualistic. This analysis included 26 species from ten taxonomic families with a total of 115 individuals. Spin-steps, 28 possible positions of the front feet during spinning, were scored from hour-long DVD recordings produced in the laboratory. Entire transcripts of hundreds to thousands of spin-steps per individual were compared by computing Levenshtein edit distances between all possible pairs of subsequences, with lengths ranging from 5 to 25—intraspecific similarity scores were then computed. Silk gallery characteristics and architecture, body size, climatic variables, and phylogenetic relationships were tested as possible drivers of intraspecific similarity in spinning behavior. Significant differences in intraspecific similarity aligned most strongly with climatic variables such that those species living in regions with high temperature seasonality, low annual precipitation, and high annual temperatures displayed more species-stereotypical spinning sequences than those from other regions, such as tropical forests. Phylogenetic signal was significant but weakly so, suggesting that environmental drivers play a stronger role in shaping the evolution of silk spinning. Body size also appears to play a role in that those of similar size are more like each other, even if not related.

A Perspective on Body Size and Abundance Relationships across Ecological Communities.

Recently, several studies have reported relationships between the abundance of organisms in an ecological community and their mean body size (called cross-community scaling relationships: CCSRs) that can be described by simple power functions. A primary focus of these studies has been on the scaling exponent (slope) and whether it approximates −3/4, as predicted by Damuth’s rule and the metabolic theory in ecology. However, some CCSR studies have reported scaling exponents significantly different from the theoretical value of −3/4. Why this variation occurs is still largely unknown. The purpose of our commentary is to show the value of examining both the slopes and elevations of CCSRs and how various ecological factors may affect them. As a heuristic exercise, we reanalyzed three published data sets based on phytoplankton, rodent, and macroinvertebrate assemblages that we subdivided according to three distinctly different ecological factors (i.e., climate zone, season, and trophic level). Our analyses reveal significant variation in either or both the CCSR slopes and elevations for marine phytoplankton communities across climate zones, a desert rodent community across seasons, and saltwater lagoon macroinvertebrate communities across trophic levels. We conclude that achieving a comprehensive understanding of abundance-size relationships at the community level will require consideration of both slopes and elevations of these relationships and their possible variation in different ecological contexts.

Early life body size in relation to risk of renal cell carcinoma in adulthood: a Danish observational cohort study.

Adult obesity increases risks of renal cell carcinoma (RCC). This study investigated if birth weight, child body mass index (BMI) and height are associated with adult RCC. The study included 301,418 children (152,569 boys) from the Copenhagen School Health Records Register born 1930-1985 with measured weights and heights at ages 7 to 13years. Birth weight was obtained by parental report. BMI and height were transformed to z-scores, and BMI was categorized as normal BMI or overweight. RCC was identified by linkage to the Danish Cancer Registry. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated by Cox proportional hazards regression. During follow-up, 1010 individuals (680 men) were diagnosed with RCC. BMI and height were positively associated with RCC with no significant sex-differences (age 13: HR = 1.14, 95% CI 1.06-1.23 per BMI z-score, HR = 1.12, 95% CI 1.05-1.20 per height z-score). Compared to children with normal BMI at ages 7 and 13 years, children with overweight only at age 13 had higher risks of RCC (HR = 1.67, 95% CI 1.24-2.26). Compared to children with average growth in height, persistently taller-than-average children (HR = 1.06, 95% CI 1.03-1.10) and children who changed from average to above-average height (HR = 1.08, 95% CI 1.01-1.15) had increased risks of RCC. Birth weight was positively associated with RCC (HR = 1.12, 95% CI 1.05-1.20 per 500 grams). Birth weight, childhood BMI and height were positively associated with RCC risk in men and women.

Helminths associated with Norops fuscoauratus (Squamata, Dactyloidae) in highland marshes of the Brazilian semi-arid.

Helminthological studies may contribute with valuable information on host biology and conservation. Herein, we provide new data on helminths infecting the lizard Norops fuscoauratus, testing one of the factors considered most important in parasitic ecology: host size. We analysed 25 specimens of N. fuscoauratus from three highland marshes in the Brazilian semi-arid. Eight taxa of helminths belonging to Nematoda, Trematoda and Acanthocephala were found. Physaloptera sp. showed the higher prevalence (40%), with a mean intensity of infection of 3.3 ± 1.46 (1-16) and mean abundance 1.32 ± 0.65 (0-16). Norops fuscoauratus represents four new host records for the helminths Cyrtosomum sp., Pharyngodon travassosi, Strongyloides sp. and Centrorhynchus sp. There is no relationship of host body size (P = 0.79) and mass (P = 0.50) with parasite richness. In addition, the present study contributes to the knowledge of the parasitic fauna of N. fuscoauratus and the Neotropical region.

Otolith Morphology and Body Size Relationships of Monopterus albus in Malaysia

Monopterus albus production in Malaysia is widely depends on wild stock. Otolith morphology has been widely used to give additional information that is crucial for aiding the seed production. Otolith morphology of Asian swamp eel, Monopterus albus and its relationships to fish size was examined. A total of 125 samples were collected from the East Coast of Peninsular Malaysia (ECPM) and Sabah for analyses. Otolith descriptions were based on its outline, including otolith length (OL, mm), otolith height (OH, mm) and otolith weight (OW, mm). Fish total length (TL, cm) and body weight (BW, kg) were also measured and recorded. Paired t-test result (p-value > 0.05) showed there is no statistically significant difference between left and right otolith dimensions. Regression models related to otolith morphometric parameters with eel length and body weight were determined. There is no morphological difference between left and right otolith of swam eel observed. Otolith weight is a good indicator of body weight (R2 =0.8994) and total length of fish (R2 =0.8707) since the R2 value is strongest than other relationship. If the otolith weight used to estimate the length and body weight of eel, the regression explains more than 87% of data variation in this Monopterus albus.

Brain structure differences between solitary and social wasp species are independent of body size allometry

Evolutionary transitions in social behavior are often associated with changes in species' brain architecture. A recent comparative analysis showed that the structure of brains of wasps in the family Vespidae differed between solitary and social species: the mushroom bodies, a major integrative brain region, were larger relative to brain size in the solitary species. However, the earlier study did not account for body size effects, and species' relative mushroom body size increases with body size in social Vespidae. Here we extend the previous analysis by measuring the effects of body size variation on brain structure differences between social and solitary vespid wasps. We asked whether total brain volume was greater relative to body size in the solitary species, and whether relative mushroom body size was greater in solitary species, after accounting for body size effects. Both total brain volume and relative mushroom body volume were significantly greater in the solitary species after accounting for body size differences. Therefore, body size allometry did not explain the solitary versus social species differences in brain structure. The evolutionary transition from solitary to social behavior in Vespidae was accompanied by decreases in total brain size and in relative mushroom body size.