Negative Allometry Research Articles

Length-Weight and Length-Length Relationships of the Scorpaena Species (Actinopteri: Scorpaenidae) in Izmir Bay (Aegean Sea of Turkey)

In this study, 173 specimens of Scorpaena porcus (n=50), Scorpaena elongata (n=20), Scorpaena scrofa (n=101), Scorpaena notata (n=2) were obtained from commercial fishermen in the Aegean Sea between 2017 and 2019. The length-weight relationships were determined for S. porcus, S. scrofa and S. elongata as W=0.0119TL3.182, W=0.0176TL3.004 and W=0.0656TL2.579, respectively. Negative allometry was found for S. scrofa and S. elongate, whereas positive allometry was present for S. porcus. However, with less than 5 individuals S. notata showed maximum, minimum, and mean total length and weight values. S. notata (2 individuals) had a mean total length and weight of 15.7-16.6 cm and 72.31-93.26 g. The results also demonstrated that the length-length relationships were strongly correlated for all Scorpaena species (r²>0.980, P<0.05).

Length-weight relationship and condition factor of Sarotherodon melanotheron and Tilapia guineensis in Lagos Lagoon, Nigeria

The length-weight relationship and condition factor of Sarotherodon melanotheron and Tilapia guineensis inhabiting Lagos lagoon were examined and the relationship among the parameters was determined by correlation. The mean total length and weight was 16.33±2.24cm and 71.44±30.04g for S. melanotheron and 16.08±2.92cm and 84.93±44.24g for T. Guineensis, respectively. The regression coefficient (b) of length and weight revealed that S. melanotheron exhibited negative allometry (b=2.36; a=-2.39; R2=0.67) while T. guineensis exhibited positive allometry (b=3.19; a=-4.54; R2=0.87). The condition factor which measures the physiology (wellbeing) of fish was greater than 1 for the two species although, it was higher in T. guineensis (2.04) than S. melanotheron (1.64). This difference may be due to variation in the weights of the two fish species as well as environmental factors in the lagoon. The study revealed that both species were healthy despite that Lagos lagoon receives wastewater from different anthropogenic sources. This shows that the study area is conducive for the development and sustenance of fisheries resources.

Comparative Study of Brain Size Ontogeny: Marsupials and Placental Mammals.

Simple SummaryThis study examined brain/body ontogenetic growth in marsupials and compared it with placental mammals. While marsupials display morphology and cerebral organization diverse from placentals, their neocortical arrangement and cellular composition is unclear. Unfortunately, knowledge of marsupial ontogenetic brain/body size allometry is limited. Since marsupial brain structure and volume differ when compared with those of placentals, marsupials are considered to possess simple behavioural patterns. This is misleading, since even at a basic observation, Australian marsupials display many of the same mental capacities as other mammals. Consequently, the study findings support further investigation into the intellectual abilities of marsupials.There exists a negative allometry between vertebrate brain size and body size. It has been well studied among placental mammals but less is known regarding marsupials. Consequently, this study explores brain/body ontogenetic growth in marsupials and compares it with placental mammals. Pouch young samples of 43 koalas (Phascolarctos cinereus), 28 possums (Trichosurus vulpecula), and 36 tammar wallabies (Macropus eugenii) preserved in a solution of 10% buffered formalin, as well as fresh juveniles and adults of 43 koalas and 40 possums, were studied. Their brain size/body size allometry was compared to that among humans, rhesus monkeys, dogs, cats, rats, guinea pigs, rabbits, wild pigs, and mice. Two patterns of allometric curves were found: a logarithmic one (marsupials, rabbits, wild pigs, and guinea pigs) and a logistic one (the rest of mammals).

Allometry in the Freshwater Pearl Mussel (Margaritifera margaritifera L.): Mussels Tend to Grow Flatter at Higher Water Speed

The freshwater pearl mussel (Margaritifera margaritifera) is one of the longest-lived invertebrate species in the world and one of the most threatened freshwater animals in Europe. Its southernmost populations, located in northwestern Spain, are in a critical conservation situation and are still understudied. Here we calibrate a non-invasive method for calculating the volume of the shell and use it to study the ontogenetic scaling of shell volume on shell length. We characterized ontogenetic growth and determined allometric relationships in 16 M. margaritifera northwestern Spain populations by using ordinary least squares regression, major axis and reduced major axis methods. We estimated topographic slopes of the sampling points using a GIS system, as a proxy of water speed. We measured 803 shells and found that the volume of the shell can precisely be estimated using three linear measurements. We found evidence for negative allometry of shell volume in the global sample and in 11 populations. We hypothesized that water speed would affect allometric patterns of local populations. Results suggest a negative relationship between the allometric slope and the topographic slope of the river section inhabited by M. margaritifera. We propose that when water speed is higher, larger mussels become proportionally flatter than in locations where water current is slower, allowing them to burrow more easily in the sediment. Our method will allow estimation of M. margaritifera biomass and ontogenetic growth without killing any specimens, which will contribute to conservation programs for this species.

Declining metabolic scaling parallels an ontogenetic change from elongate to deep-bodied shapes in juvenile Brown trout.

Body shape and metabolic rate can be important determinants of animal performance, yet often their effects on influential traits are evaluated in a non-integrated way. This creates an important gap because the integration between shape and metabolism may be crucial to evaluate metabolic scaling theories. Here, we measured standard metabolic rate in 1- and 2-years old juvenile brown trout Salmo trutta, and used a geometric morphometrics approach to extricate the effects of ontogeny and size on the link between shape and metabolic scaling. We evidenced near-isometric ontogenetic scaling of metabolic rate with size, but also a biphasic pattern driven by a significant change in metabolic scaling, from positive to negative allometry. Moreover, the change in metabolic allometry parallels an ontogenetic change from elongate to deep-bodied shapes. This is consistent with the dynamic energy budget (DEB) and surface area (SA) theories, but not with the resource transport network theory which predicts increasing allometric exponents for trends towards more robust, three-dimensional bodies. In addition, we found a relationship between body shape and size independent metabolic rate, with a positive correlation between robustness and metabolic rate, which fits well within the view of Pace-of-Life Syndromes (POLS). Finally, our results align with previous studies that question the universality of metabolic scaling exponents and propose other mechanistic models explaining the diversity of metabolic scaling relationships or emphasizing the potential contribution of ecological factors.

Hammer it out: shifts in habitat are associated with changes in fin and body shape in the scalloped hammerhead (Sphyrna lewini)

Abstract Major shifts in habitat often occur during life history and can have significant impacts on the morphology and function of an animal; however, little is known about how such ecological changes influence the locomotor system of large aquatic vertebrates. Scalloped hammerheads (Sphyrna lewini) are large sharks found in warm temperate and tropical waters. Smaller scalloped hammerheads are generally found in near-shore habitats, but as they grow larger, individuals spend time in deep-water, pelagic habitats. We measured a number of morphological traits of scalloped hammerheads, ranging from 32 to 130 cm, to determine whether there are allometric changes in morphology in association with this shift in habitat. We found that head morphology, caudal fin area and lateral span scaled with negative allometry, whereas the lengths of their pectoral, dorsal and caudal fins, and their pectoral and caudal fin aspect ratios, scaled with positive allometry. Furthermore, the largest shark in our dataset exhibited an optimal body fineness ratio for locomotor efficiency. This suggests that the changes in ecology have profound influences on the functional morphology of scalloped hammerheads. We discuss how these drastic morphological changes relate to potential changes in scalloped hammerhead swimming function and performance.

The influence of body size and phylogeny on trabecular microstructure in the proximal femur and humerus of rodents and primates

Life history theory states that organisms maximize their fitness via energetic trade‐offs between various biological functions. It has been well‐established that life history strategy is related to intraspecific variation in body size and that body size predicts some bone microstructural properties, but the relationship between life history strategy and skeletal variation has not been sufficiently examined across multiple mammalian clades. Generally, small‐bodied mammals have “fast” life histories and faster growth rates than large‐bodied mammals, meaning small mammals deposit bone tissue at a faster rate, which may affect skeletal morphology. Therefore, the goal of this study was to conduct a preliminary analysis of trabecular bone structure in the rodent and primate humerus and femur to evaluate the influence of life history traits, particularly body size, on bone properties in a phylogenetically diverse sample. Using a sample of 67 size‐matched adult rodent and primate individuals from 8 extant rodent genera (N=26) and 10 extant primate genera (N=41) ranging in body size from 0.04kg to 70kg, we analyzed trabecular bone structure in the proximal femoral and humeral head. Regression analyses were used to assess associations between trabecular bone properties and body size and one‐way ANOVAs were used to compare bone properties between rodents and primates across three size‐matched classes.Regression results are consistent with previous primate and mammal studies. Bone volume fraction (BV/TV) scales with weak positive allometry in both groups and both elements except for the rodent humerus, which scales isometrically. Degree of anisotropy (DA) varies across all groups and shows no consistent relationship with body size. Trabecular thickness (Tb.Th) and trabecular separation (Tb.Sp) increase with body size, while connectivity density (Conn.D) and bone surface density (BS/BV) decrease with body size across both clades and elements. In both groups and both bones, Tb.Th, Tb.Sp, and Conn.D scale with strong negative allometry while BS/BV scales with strong positive allometry. ANOVAs reveal that Tb.Th and Tb.Sp are higher in the primate femur than in the rodent femur for medium and large size classes, while Conn. D is higher in the rodent femur for medium and large size classes. Other bone properties do not show consistent patterns of differences between primates and rodents. Overall, while overlapping confidence intervals for all slopes suggest body size scales similarly with these bone properties across clades, ANOVA results suggest that medium and large bodied rodents have thinner, more numerous trabeculae in the femur compared to similarly‐sized primates. Further investigation is necessary to elucidate the biological significance of this result and the underlying mechanisms driving the observed phenomenon.

LENGTH-WEIGHT RELATIONSHIP AND HEALTH OF Macrobrachium dux (LENZ, 1910) AND Macrobrachium macrobrachion (HERKLOTS, 1851) IN RIVER ETHIOPE HEADWATERS, NIGERIA

The length-weight relationship and condition factor of two identified Palaemonidae species, Macrobrachium dux (Lenz, 1910) and Macrobrachium macrobrachion (Herklots, 1851) from the upper limnic River Ethiope, Nigeria, were investigated for future aquaculture feather nest and management. Prawn samples were collected from three sites (Umutu, Abraka, and Eku) by artisanal fishers using local traps and scooping gear. Of the 285 prawns collected from artisanal, 238 (83.51%) were allotted to Abraka and Eku registered 47(16.49%). The prawns were identified using the taxonomic keys. The total length of the prawns was measured to the nearest 0.01 cm with a pair of dividers and a metre rule. The weights of the shrimp were also taken using the OHAUS dial spring scale to the nearest 0.1g. The length-frequency analyses showed the males ranged from 4.1-6.5cm in length, with a weight range of 0.51-2.63g, mostly more massive than the females (1.5-5.3cm) with a higher weight range (0.03-12.0g) and the non-identified sex (NIS) group with a 0.1-2.9cm length range. Only the NIS of M.dux at Eku showed positive allometric growth (b &gt; 3), while the others showed negative allometry (b 3). High correlation determinants (r²) exist between the length-weight of all species besides the female M.dux at Abraka (0.26) and Eku (0.33). The condition factors of the two prawns predicted upper River Ethiope soft water quality as good for farming M.dux and M. macrobrachion.

Inter‐relationships among body mass, jaw musculature and bite force in birds

AbstractBite force can provide an insight into the feeding biomechanics and ecology of vertebrates. There has been an increasing interest in bite force in birds with data being collected using force transducers although bite forces have also been calculated from the mass of the jaw musculature. Studies have sought to find ecological correlates between bite force and diet or feeding style as well as with morphology. This study collated data reported in the literature for bite force and mass of the jaw musculature in birds and explored the relationships between these variables and their relationships with body mass to test two hypotheses. First, bite force and mass of the jaw musculature would scale with body mass irrespective of the phylogeny. Second, bite force and mass of the jaw musculature would be directly related to each other and be unrelated to phylogeny. Phylogenetically controlled analyses showed that in relation to body mass there were different relationships with bite force, and with the mass of the jaw musculature, for non‐passerine (isometry and negative allometry, respectively) and passerine species (both positive allometry). By contrast, a single significantly positively allometric relationship described the relationship between jaw muscle mass and bite force. These relationships were driven in part by the diet of the species concerned but also may reflect morphological differences in jaw musculature. The few studies that compare measured and calculated bite force for the same species show that values derived from muscles were higher. Detaching muscles from their points of origin and insertion to calculate physiological cross‐sectional area may be biasing bite force calculations.

Factors regulating growth pattern and condition factor of an amphibious fish Periophthalmus gracilis living in the Mekong Delta.

Growth pattern and condition factor (CF) are essential to fish resource assessment but limited to Periophthalmus gracilis—an amphibious fish living in the mudflats along the Indo-Pacific regions, including the Mekong Delta (MD), Vietnam. This study lasted from April 2020 to March 2021 to verify if their growth pattern and CF change with sex, size, season, month and site. The total length and weight of 486 individuals (236 females and 250 males) were 2.9–5.9 cm and 0.13–1.66 g, respectively. The mudskipper displayed negative allometry as the slope value (b = 2.69 ± 0.06) obtained from length and weight (LWR) was significantly less than 3 (p < 0.01), indicating that most fish specimens were caught in the immature stage. The fish growth pattern did not change with sex as both males and females displayed negative allometry but varied by size since the mudskipper showed negative allometry in the immature group and isometry in the mature group. Likewise, growth type changed with season since fish showed negative allometry in the dry season but isometry in the wet season. As the slope value (b) varied by site and month, the mudskipper displayed spatiotemporal growth patterns, ranging from negative to positive allometry. The CF was impacted by sex as this value of females (1.09 ± 0.02) was higher than that of males (0.96 ± 0.01, p < 0.01). Besides, CF was regulated by fish length since this value was higher in the mature group (1.12 ± 0.03) than in the immature group (1.01 ± 0.01, p < 0.01). Likewise, CF was affected by season as this value was higher in the wet season (1.05 ± 0.02) than in the dry season (0.99 ± 0.01, p < 0.01). Although the CF varied with site and month variables (p < 0.01), this value (1.02 ± 0.01) was generally higher than 1, showing fish adapted well to their habitat. The fish length at first capture should be increased to exploit this species sustainably.

Length-Weight Relationship And Condition Factor Of Mangrove Fish Species In Azagny National Park (Grand-Lahou Department, Ivory Coast)

The length-weight relationship and condition factor of mangrove fish species in Azagny National Park (ANP) were studied, to provide baseline data of the impact of mangrove disturbances on ichthyofauna. Specimens were captured from March 2019 to February 2020 using gillnets and mesh traps. After identification, each specimen was weighed to the nearest gram and measured to the nearest millimeter. Twenty-eight species belonging to 17 families and 24 genera were selected based on their numbers (only species with at least 10 specimens were considered). Most of these species have a negative allometry (22 species, 78.57%). 14.28% species showed positive allometry and 7.14% species showed isometry. The length-weight regressions are significant with a coefficient of determination (r²) varying between 0.115 for Chrysichthys maurus and 0.936 for Labeo coubie. The coefficient of allometry b varies from 0.413 for Chrysichthys maurus to 4.272 for Labeo coubie with a mean value of 2.384 ± 0.810. The condition factor ranged on average from 0.935 ± 0.966 for Schilbe mandibularis 113.3 ± 10.644 for Chrysichthys maurus. This study provides information on the effects of mangrove disturbance on the growth of species of the said ecosystem and contributes to the management of the ichthyofauna of the ANP.

Effect of Environmental Parameters on the Reproduction of the White Mullet (Mugil curema, Valenciennes, 1836) in the Saloum Delta (Senegal)

Mugil curema, known as white mullet, was one of the fish species encountered in the fisheries landings of the Saloum Delta. In this study, the morphometric parameters and the reproductive biology of this species were studied as well as the influence of environmental parameters on its reproduction. Experimental fisheries were carried out monthly in the Saloum Delta. The fish were caught using surface drift nets. The captured individuals were measured and weighed. The gonads were collected to determine the sex and the stages of sexual maturity. Out of a total of 406 individuals sampled in the Saloum Delta, 306 females and 100 males were identified, no individuals of undetermined sex were obtained. The sex ratio was globally in favor of females. Individuals in this study ranged in size from 102 to 385 mm and weight from 34.9 to 395 g. The allometric coefficient b was equal to 2.40 and indicated a negative allometry. The exploitation of the monthly IGS results indicated that reproduction was in April, May and June. The size at first sexual maturity indicated that the males matured at a size of 220 mm, lower than that of the females 226 mm.

Histopathology and Morphometric Characters of Tilapia guineensis as Biomarker to Evaluate Level of Environmental Stress in Badagry and Ojo Creeks, Lagos, Nigeria

Forty wild adult Tilapia guineensis were sourced from Ojo and Badagry creeks between January and March 2021, to investigate its morphometric character (total length, body weight, standard length, and head depth) and tissues structure (gill, muscle and small intestine) differences. Samples were collected and analysed using standard methods. The results showed no significant difference (P&lt;0.05) between the mean total length, body weight, standard length, and head depth of Tilapia guineensis recorded from both creeks. Length-weight relationships of T. guineensis obtained from both creeks showed negative allometry(b&lt;3) growth pattern while its condition factor (k) value was more significant than one, which indicated that the fishes are in good condition. Muscle of T.guineensis from Ojo creek showed a severe lesion of muscle bundle, degeneration of muscular bundle and shortening of bundles. Similarly, the gills structure of T. guineensis from Ojo creek showed severe degeneration, hyperplasia of secondary gill lamellae, and curling of secondary lamellae with unclear water channels. It is also characterized by hypertrophy of lamellae, and there is evidence of partial fusion of lamellae and dilation of gill filament. The observation of none lesion or degenerated tissues of T. guineensis in Badagry creek could suggest that Ojo creek is more subjected to effluents or other environmental stressors than Badagry creek. In conclusion, T. guineensis from Badagry creek is less affected by any environmental contaminants than T. guineensis from Ojo creek. Therefore, a collective effort towards ensuring reduction in direct discharge of untreated effluent or avoidance of another unhygienic usage of the creeks is very pertinent.

Relative growth and reproductive biology of females of Macrobrachium amazonicum (Heller, 1862) (Decapoda: Caridea: Palaemonidae) in the semiarid Northeast Region, Brazil

Abstract We analyzed aspects related to the relative growth and reproduction of females of Macrobrachium amazonicum (Heller, 1862) in a population of the semiarid Northeast Region of Brazil. Carapace (CL) and total length (TL) ranged 5.57–17.61 mm (mean 10.96 ± 2.07 mm) and 28.96–80.63 mm (mean 52.14 ± 9.13 mm), respectively. Relative growth analysis showed that total length increased in a higher proportion than carapace region (positive allometry). This region also increased in a higher proportion regarding weight (negative allometry) due to energy cost in reproduction. Of the three criteria used to determine size at the onset of maturity (SOM), the smallest size observed was obtained by physiological SOM I (based on advanced vitellogenesis): 8.22 mm CL, followed by functional SOM II (8.83 mm CL, based on ovigerous females) and physiological SOM III (9.48 mm, based on CL50). SOM was influenced by the population’s phenotype, and SOM I and SOM II showed synchronicity. The estimated maximum fecundity was 2,805 eggs per female, with a mean value of 690 eggs. There was continuous reproduction and the dry season favored the percentage occurrence of ovigerous females (September-December 2016 and July-August 2017). The smaller lengths of the individuals, compared to other female populations, were due to the characteristics of the environment and the intrinsic traits of the studied population. The negative allometry for the length-weight relation and the continuous reproductive period with seasonal variation was similar as that recorded for other Brazilian localities. This suggests that these last characteristics are a pattern for this species, which shows a latitudinal variation only in the sizes reached. The fast maturation and continuous reproduction of M. amazonicum females make them a potential species for commercial exploitation.

Growth pattern and stock assessment of Jinga shrimp Metapenaeus affinis (H. Milne Edwards, 1837) (Decapoda, Penaeidae) from the southeastern Mediterranean of the Egyptian coasts

A total of 1457 random specimens of the newly established population of Metapenaeus affinis was collected monthly from the shrimp commercial catch at Boughaz El-Maadiyah landing center (Mediterranean Sea, Egypt) during the period from July 2020 to June 2021. This study aims to shed light on the growth pattern and stock assessment of this newly established species. The results showed that the catch of M. affinis varied in lengths between 5.4 cm and 16.0 cm TL. At length 13.5 cm, the population was composed of 100% females. The test of the allometric coefficients “b” of the total length (TL) – carapace length (CL) relationship showed negative allometry growth for males, females, and sexes combined. The values of “b” for the length-weight relationship reflected isometric growth for males, and a pattern of positive allometric growth was shown for females and sexes combined. The overall sex ratio (F:M) was 1.00:0.58 and the Chi-square test reflected high significant differences (χ2 = 100.68; df = 1; P < 0.01). Five cohort groups representing 2 yr for females and four cohort groups representing 1+yr for males were identified by Bhattacharya's method. For combined sexes, the growth parameters were L∞ = 19.849 cm, K = 0.242, and to = −0.872. The study of fishery parameters revealed that M. affinis population was still unexploited (Ecur. = 0.38). Further studies are recommended to shed lights on its spawning and nursery grounds in the Egyptian waters. The study of the reproductive biology for this shrimp species is also recommended.

Understanding Australia’s unique hopping species: a comparative review of the musculoskeletal system and locomotor biomechanics in Macropodoidea

Kangaroos and other macropodoids stand out among mammals for their unusual hopping locomotion and body shape. This review examines the scaling of hind- and forelimb bones, and the primary ankle extensor muscles and tendons. We find that the scaling of the musculoskeletal system is sensitive to the phylogenetic context. Tibia length increases with positive allometry among most macropodoids, but negative allometry in eastern grey kangaroos and isometry in red kangaroos. Femur length decreases with stronger negative allometry in eastern grey and red kangaroos than among other macropodoids. Muscle masses scale with negative allometry in western grey kangaroos and with isometry in red kangaroos, compared to positive allometry in other macropodoids. We further summarise the work on the hopping gait, energetics in macropodoids, and stresses in the musculoskeletal system in an evolutionary context, to determine what trade-offs may limit locomotor performance in macropodoids. When large kangaroos hop, they do not increase oxygen consumption with speed, unlike most mammals, including small hopping species. We conclude that there is not enough information to isolate the biomechanical factors that make large kangaroos so energy efficient. We identify key areas for further research to fill these gaps.

Variation in eucalypt bark allometry across Australia

Positive bark allometry (hyperallometry), characterised by rapid early bark growth, is expected where fire selects for thicker bark to resist cambial damage and topkill. We examine this prediction for 52 Australian eucalypt species. An effective bark allometric coefficient (α) was estimated from the first segment of breakpoint regression, which included fire-affected young trees. Eucalypts presented a negative–positive bark allometry continuum. Contrary to expectation, 73% of species (n = 38) displayed negative effective bark allometry. Early rapid bark growth was observed (α = 0.92 ± 0.04, x ± s.e., n = 168 sites), but was slower than isometry and bark was thinner overall than expected. Fire type (crown-fire propensity) and net primary productivity (resource availability) most influenced bark allometry. Productive ecosystems experienced crown-fire and bark was thicker at standardised diameter (x ± s.e. = 2.04 ± 0.20 cm) than in less productive ecosystems under surface fire (x ± s.e. = 1.68 ± 0.18 cm). Bark morphology types did not differ in their stem diameter (x ± s.e. = 21.47 ± 1.06 cm) or bark thickness (x ± s.e. = 1.88 ± 0.08 cm) thresholds, representing putative stable alternative evolutionary solutions. Fundamentally, many eucalypts possess negative bark allometry with a relatively thin bark compared to non-eucalypts, because unique bark bud traces sustain post-fire resilience through epicormic resprouting. The resource allocation trade-off to thin bark v. height growth, selected by fire and resource limitation, accounts for eucalypt persistence and domination of Australia’s flammable ecosystems.

Length–Weight Relationships of Indigenous Fish Species Salmostoma boopis from Bhima River, India

Salmostoma boopis is small indigenous fish native to Indian fresh water. It is found abundantly in the catch of fishermen from Bhima river of Maharashtra throughout the year. The present study included length-weight relationships of Salmostoma boopis from Bhima river at Hatwalan site. 131 specimens were sampled during the period of April 2021 to March 2022 for analysis of their length–weight relationships (LWRs). The intercept (‘a’ value) was found to be 0.009, whereas the slope (‘b’ value) was 2.84. The LWRs analysis of the species revealed that S. boopis has b value less than 3 indicating negative allometry, while these values are in expected range (2.5 to 3.5). The R2 value in the present study was found to be greater than 0.80 for the species, which indicated the proper fitness of the model for growth and good health status.

An evaluation of common methods for comparing the scaling of vertical force production in flying insects.

Maximum vertical force production (Fvert) is an integral measure of flight performance that generally scales with size. Numerous methods of measuring Fvert and body size are accessible to entomologists, but we do not know whether method selection affects inter- and intraspecific comparisons of Fvert-size scaling. We compared two common techniques for measuring Fvert in bumblebees (Bombus impatiens) and mason bees (Osmia lignaria), and examined Fvert scaling using five size metrics. Fvert results were similar with incremental or asymptotic load-lifting, but scaling analyses were sensitive to the size metric used. Analyses based on some size metrics indicated similar scaling exponents and coefficients between species, whereas other metrics indicated coefficients that differed by up to 18%. Furthermore, Fvert showed isometry with body lengths and fed and starved masses, but negative allometry with dry mass. We conclude that Fvert can be measured using either incremental or asymptotic loading but choosing a size metric for scaling studies requires careful consideration.

Parasitism of Arapaima gigas (Schinz, 1822) in fish farms of the state of Amazonas, Brazil.

The objective of this study was to investigate the parasites occurrences and to determine the rates of infestation/parasitic infection in juvenile Arapaima gigas from seven fish farms in the state of Amazonas, relating to the characteristics of these fish farms. Of the 70 A. gigas evaluated, 43 were infested/infected, with a total of 133 parasites collected. Three fish farms (2, 4, 6) showed the highest levels of prevalence of parasites (100%, 70%, 70%), mean intensity (4.1±2.6, 8.1±9.2, and 2.1±1.3), and mean abundance (4.1±2.6, 5.7±8.1, and 1.5±1.5), respectively. Prevalence ranged from 30% to 100%, mean intensity from 1.0 to 8.1 and mean abundance from 0.3 to 5.7. Monogenea, Digenea, Nematoda (Hysterothylacium sp. and Spirocamallanus sp.) and Acanthocephala (Neoechinorhynchus sp. and Polyacanthorhynchus sp.) were identified. The parasites Hysterothylacium sp. and Neoechinorhynchus sp. were the most prevalent parasites with 31.43% and 15.71%, respectively. The fish presented negative allometry in growth and constant condition factor. Measures to prevent and control the parasitic diseases diagnosed are discussed as well prophylactic practices that contribute to the biosecurity of the farms.