Body Size Research Articles

Effect of Body Size on Plasma and Tissue Pharmacokinetics of Danofloxacin in Rainbow Trout (Oncorhynchus mykiss)

Danofloxacin is a fluoroquinolone antibiotic approved for use in fish. It can be used for bacterial infections in fish of all body sizes. However, physiological differences in fish depending on size may change the pharmacokinetics of danofloxacin and therefore its therapeutic efficacy. In this study, the change in the pharmacokinetics of danofloxacin in rainbow trout of various body sizes was revealed for the first time. The objective of this investigation was to compare the plasma and tissue pharmacokinetics of danofloxacin in rainbow trout of different body sizes. The study was conducted at 14 ± 0.5 °C in fish of small, medium, and large body size and danofloxacin was administered orally at a dose of 10 mg/kg. Concentrations of this antimicrobial in tissues and plasma were quantified by high performance liquid chromatography with ultraviolet detector. The plasma elimination half-life (t1/2ʎz), volume of distribution (Vdarea/F), total clearance (CL/F), peak concentration (Cmax), and area under the plasma concentration–time curve (AUC0–last) were 27.42 h, 4.65 L/kg, 0.12 L/h/kg, 2.53 µg/mL, and 82.46 h·µg/mL, respectively. Plasma t1/2ʎz, AUC0–last and Cmax increased concomitantly with trout growth, whereas CL/F and Vdarea/F decreased. Concentrations in liver, kidney, and muscle tissues were higher than in plasma. Cmax and AUC0–last were significantly higher in large sizes compared to small and medium sizes in all tissues. The scaling factor in small, medium, and large fish was 1.0 for bacteria with MIC thresholds of 0.57, 0.79, and 1.01 µg/mL, respectively. These results show that therapeutic efficacy increases with body size. However, since increases in danofloxacin concentration in tissues of large fish may affect withdrawal time, attention should be paid to the risk of tissue residue.

Biomass competition connects individual and community scaling patterns.

Both metabolism and growth scale sublinearly with body mass across species. Ecosystems show the same sublinear scaling between production and total biomass, but ecological theory cannot reconcile the existence of these nearly identical scalings at different levels of biological organization. We attempt to solve this paradox using marine phytoplankton, connecting individual and ecosystem scalings across three orders of magnitude in body size and biomass. We find that competitive interactions determined by biomass slow metabolism in a consistent fashion across species of different sizes. These effects dominate over species-specific peculiarities, explaining why community composition does not affect respiration and production patterns. The sublinear scaling of ecosystem production thus emerges from this metabolic density-dependence that operates across species, independently of the equilibrium state or resource regime. Our findings demonstrate the connection between individual and ecosystem scalings, unifying aspects of physiology and ecology to explain why growth patterns are so strikingly similar across scales.

Exposure, body size, and zooplankton overland dispersal capacity

AbstractThe dormant life stages of freshwater zooplankton are generally resistant to environmental exposure, and this facilitates their overland dispersal. However, environmental exposure and overland dispersal are less well studied for the active life stages of freshwater zooplankton. To characterize empirically the longevity of active life stages out of water, survival time to air exposure was measured in the laboratory for seven cladoceran species using heartbeat cessation to signify survival time. Survival time increased with body dry weight with an allometric scaling exponent near 2/3 in both a single‐species model with Daphnia mendotae and a multispecies model with five bivalved species that included Bosmina longirostris, Acroperus harpae, Ceriodaphnia dubia, D. mendotae, and Daphnia magna. The 2/3 scaling exponent is consistent with Euclidean geometry and points to water loss across the surface of a spherical body as the cause. Survival time of a 6th species, Holopedium gibberum, was 618% longer than predictions based on the multispecies model, likely due to its gelatinous mantle. Survival time of a 7th species, Bythotrephes cederströmii, was 58–83% shorter than predictions based on the multispecies model, likely due to its lack of a bivalve carapace. The longest survival time of an individual was 225.4 min (H. gibberum). Results suggest that at landscape scales, body size could be a proxy for the geographic extent of overland dispersal capacity of the active life stage.

Filtration Behaviour of Ostrea edulis: Diurnal Rhythmicity Influenced by Light Cycles, Body Size and Water Temperature

AbstractDespite the existing studies on oyster physiology, it is a concern that, by ignoring the diurnal rhythmicity of feeding activities, the current knowledge on oyster filtration might be unrepresentative of their real filtration capacity. In the present study, the diurnal and nocturnal fluctuations of Ostrea edulis clearance rate were investigated for the first time under laboratory conditions, also considering the combined effects of water temperature and oyster size. A positive correlation was found between the mean clearance rate (CRm) and body size for both length and wet weight, with an average of 0.5 L h−1 and 0.1 L h−1 of water filtered by large and small adult oysters respectively during the 24-h experiment. A positive significant correlation between mean clearance rate and water temperature was found only for large oysters, suggesting further studies utilising temperature ranges closer to O. edulis thermal optimum are required to clarify the influence of temperature on oyster filtration activities across different size classes. The results of this study also showed a discontinuous ingestion of food by O. edulis throughout 24-h intervals, with higher values of clearance rate observed during hours of darkness at most temperatures for both size classes. This suggests photoperiod may have a potential influence on O. edulis filtration. Providing a better understanding of O. edulis filtration behaviour, these findings have implications for ecological restoration, aquaculture, and comparative studies on oyster bioenergetics and physiology, with direct applications to the development of predictive models and the assessment of ecosystem services provided by O. edulis habitat.

A second species of Stenasellus Dollfus, 1897 (Isopoda, Stenasellidae) from sulfidic groundwater of Iran described using morphological and molecular methods

We report on a new species of Stenasellus Dollfus, 1897 (Isopoda, Stenasellidae) from groundwater of Iran. Stenasellus stygopersicus Jugovic, Malek-Hosseini & Issartel sp. nov. inhabits the Chah Kabootari Cave that is adjacent to the Tashan Cave, the type locality of the first recorded species of Stenasellidae from Iran, Stenasellus tashanicus Khalaji-Pirbalouty, Fatemi, Malek-Hosseini & Kuntner, 2018. Both caves are fed by sulfidic groundwater and belong to the Tashan-Chah Kabootari species-rich aquifer on the Zagros Mountains. Both species are characterized by a large body size (≥ 20 mm), a female-biased sexual size dimorphism, and a distinct black-pigmented Bellonci’s organ. Stenasellus stygopersicus differs from S. tashanicus by a short and wide protopodite of pleopod I, setae set essentially along the apical margin of pleopod I exopodite, the subequal length and width of the male pleopod II protopodite, and deeply bilobed endopodites of pleopods III–V. Molecular evidence suggests that while Stenasellus stygopersicus is sister to S. tashanicus, the species are genetically distinguishable, with divergence time estimates ranging from 23 to 39.8 Ma.

A Comparative Metabolomics Study of the Potential Marker Compounds in Feces from Different Hybrid Offspring of Huainan Pigs

As a notable native Chinese genetic population, the Huainan pig has an exceptional meat quality but a low percentage of lean meat and subpar genetic performance. To better exploit the superior genetic traits of the Huainan pig and address knowledge gaps regarding the optimization of its hybrid offspring, this study used Huainan pigs as the maternal line and bred them with Yorkshire, Landrace, and Berkshire sires. This approach produced three hybrid combinations: Yorkshire × Huainan (YH), Landrace × Huainan (LH), and Berkshire × Huainan (BH). The body size, fat ratio, and average backfat thickness of these hybrid progeny were evaluated under the same feeding management and nutritional circumstances. The results revealed that the average backfat thickness of YH was significantly lower than that of LH and BH. In order to better understand the causes of these variations, fecal samples were taken from three pigs in each group for metabolomic analysis. A total of 2291 metabolites were identified, including benzene derivatives (16.6%), amino acids and their metabolites (14.5%), and organic acids (13.4%), with pyruvaldehyde and norethindrone acetate elevated in YH compared to LH and BH. In addition, the three hybrid pig groups commonly exhibited differences in the “glycerophospholipid metabolism” pathway. This variation may also contribute to differences in their fat ratio and backfat thickness. Our findings provide a novel perspective on the role of hybrid vigor in advancing the genetic population of Huainan pigs, while also revealing the unique metabolic characteristics of the YH with regard to fat deposition. This study is expected to enhance the conservation and effective utilization of genetic resources within the Huainan pig population.

Big fish can't jump? Allometry of terrestrial jumping in cyprinodontiform fishes.

Teleost fishes that emerge onto land must produce effective terrestrial movements to return to the water. Using the Cyprinodontiformes as a model system, we examined a terrestrial behavior termed the tail-flip jump across a size range of individuals representing three species of aquatic killifishes (Gambusia affinis, Poecilia mexicana, and Jordanella floridae) and two species of amphibious killifishes (Kryptolebias marmoratus and Fundulus heteroclitus) to identify potential effects of size (mass) on jumping performance. The ballistic trajectory equation was used to partition the contributions of velocity (determined by acceleration and contact time) and takeoff angle to jump distance. Despite differences in size (over an order of magnitude) all fishes took off from the ground at ∼45°. However, in terms of total displacement, aquatic and amphibious killifish species scaled differently in their ability to perform the tail-flip jump. Aquatic killifishes decrease in total jump distance as mass increases; however, amphibious killifishes increase in total jump distance as mass increases. Aquatic killifishes cannot produce adequate accelerations at larger sizes, but amphibious killifishes produce similar accelerations despite over an order of magnitude size difference. Because of this, amphibious killifish species are able to maintain fast takeoff velocities at large body sizes. Distinct scaling patterns may be generated by differences in body shape. Aquatic killifishes have a fusiform body shape, with most of their body mass in the anterior of the body, while amphibious killifishes have a more uniform body shape that reduces their overall mass present in the anterior body. We hypothesize that reduced mass in the anterior body facilitates raising the head over the tail to prepare for takeoff. In contrast with amphibious species, the negative scaling relationship seen in body size vs. displacement in aquatic killifishes implies an upper size limit to producing the tail-flip jump for fish species that infrequently encounter the terrestrial environment.

Optimizing ring selection for secondary tricuspid regurgitation: the role of body size.

To investigate whether a larger prosthetic ring relative to a patient's body surface area (BSA) is associated with an increased risk of tricuspid regurgitation (TR) recurrence after tricuspid annuloplasty and adverse effects on long-term outcomes. We retrospectively enrolled 239 patients who underwent tricuspid ring annuloplasty and mitral valve surgery between 2011 and 2016. The tricuspid annuloplasty ring index (TARI) was calculated by dividing the size of the annuloplasty ring (mm) by the BSA (m2). Risk factors for recurrent TR were determined using multivariate analysis. Long-term clinical outcomes were compared between propensity score-matched large and small TARI groups. The annuloplasty ring size unadjusted for BSA did not affect TR recurrence (P = 0.388). TARI (subdistribution hazard ratio 1.34; 95% CI 1.07-1.67, P = 0.009) and right ventricular dimension (P = 0.020) were independent risk factors for recurrent TR in multivariate analyses. The cutoff value for discriminating the small from the large TARI group was 19.0 mm/m2. In the matched cohort, the cumulative TR recurrence at 3 years postoperatively was 0% in the small TARI group and 7.1% (95% CI 0-14.8%) in the large TARI group(P = 0.025). The cumulative incidence of adverse events at 3 years postoperatively was 8.3% (95% CI 5.1-16.2%) in the small TARI group and 13.2% (95% CI 3.3-23.0) in the large TARI group (P = 0.085). The patient's body size might better be considered when determining the tricuspid ring size.

Genetic and biological insights into Hydatigera taeniaeformis in invasive black rats from southern Chile

IntroductionThis study investigates the genetic variability of Hydatigera taeniaeformis in black rats (Rattus rattus), a common tapeworm that infects cats and rodents worldwide. Despite its widespread presence and zoonotic potential, little is known about the genetic diversity of this parasite in the Americas.MethodsWe conducted DNA barcoding analysis using mitochondrial cox1 gene sequences using samples collected from 171 invasive wild black rats, captured in the temperate rainforest of Southern Chile. We also included two adult parasites isolated from road killed Kodkods (Leopardus guigna), a small felid species native to the Americas.ResultsOur findings revealed only two haplotypes, suggesting low genetic variability in a parasite that arrived in the Americas with the Spanish colonization.DiscussionThese haplotypes are more closely related to parasite populations from Peru, Africa, Australia, and Europe, suggesting an origin linked to the Spanish colonization, possibly from North Africa via the Canary Islands. The study also analyzed infection rates, parasite size, and their correlation with host body size, age, and weight, revealing significant patterns. These results provide new insights into the biogeography and genetic diversity of H. taeniaeformis in a new geographical area, enhancing our understanding of its evolutionary history.

Transcriptomic profiling of backfat and muscle in Lijiang pigs with divergent body size across growth stages.

Backfat thickness is an important economic trait that affects pork quality and flavor. The Lijiang pig (LJP), a local breed in Yunnan province, China, exhibits variations in growth and body composition. However, the molecular basis for these variations is unclear. This study aimed to analyze transcriptome profiles of backfat at different growth stages in LJP with discrepant body size: two months (M2), four months, and six months. Firstly, we analyzed the gene expression differences and discovered a significantly highest number of differentially expressed genes (DEGs) at the M2 stage. Secondly, we identified four gene profiles with reverse expression trends in LJP populations with different body sizes, and the related genes mainly associated with immune response functionality. Thirdly, we observed a lower correlation in LJP with large body size at the M2 stage, with a specific enrichment of DEGs with high genetic differentiation related to neural activity. Finally, we correlated transcriptome profiles of muscle and backfat and discovered the lowest correlation at the M2 stage. Highly correlated genes exhibited more significant differences and were prominently enriched for immune response processes. This study unveils candidate genes linked to backfat growth in LJP, emphasizing the specificity of the early growth stage of backfat.

A systematic review of observational studies on the association between diet quality patterns and visceral adipose tissue.

Beyond obesity, visceral adipose tissue (VAT) has emerged as an important predictor of chronic disease, but the role of diet quality patterns (DQP) in VAT development is not well defined. Therefore, we conducted a systematic review of how various DQP are associated with VAT via literature searches in PubMed and EMBASE. We included observational investigations in disease-free adults/adolescents that related DQP to VAT assessed by imaging methods. The studies were evaluated separately for a priori and a posteriori DQP and according to design differences. Study quality was assessed using the Risk of Bias in Non-randomised Studies of Interventions tool. Of the 1807 screened articles, thirty-five studies met the inclusion criteria. The majority of a priori indices, for example, the Healthy Eating Index, showed significant inverse associations with VAT, while only a small proportion of a posteriori patterns were related to VAT. Results did not differ substantially by the method of exposure and outcome assessment or between studies with (n 20) or without (n 15) body-size adjustment, but significant findings were more common in younger v. older individuals, USA v. other populations and investigations with moderate v. serious risk of bias. The heterogeneity of the existing literature limited the ability to quantify the magnitude of the associations across studies. These findings suggest that a high-quality diet, as assessed by a priori DQP, is generally inversely associated with VAT, but results for a posteriori DQP are less consistent. As associations persisted after adjusting for body size, diet quality may beneficially influence VAT beyond its association with obesity.

Using unmanned aerial vehicles to estimate body volume at scale for ecological monitoring

Abstract Demographic data are essential to construct mechanistic models to understand how populations change over time and in response to global threats like climate change. Existing demographic data are either lacking or insufficient for many species, particularly those that are challenging to obtain direct measurements from that can be used to estimate demographic rates, like marine mammals. A method for collecting accurate demographic data to construct robust demographic models at scale would fill this knowledge gap for difficult‐to‐access species. We introduce a novel, non‐invasive method to estimate the 3D body size (volume) of pinnipeds (seals, sea lions and walruses) that will allow monitoring at high spatial and temporal scales. Our method integrates 3D structure‐from‐motion photogrammetry data collected via planned flight missions using off‐the‐shelf, multirotor unmanned aerial vehicles (UAVs). We apply and validate this method on the grey seal Halichoerus grypus, a pinniped species that spends much of its time at sea but is predictably observable during its annual breeding season. We investigate the optimal ground sampling distance (GSD) for surveys by calculating the success rates and accuracy of volume estimates of individuals at different altitudes. Based on current technology, we establish an optimal GSD of at least 0.8 cm px−1 for animals similar in size to UK grey seals (~1.2–2.5 m length), making our method reproducible and applicable to other species. We found volume estimates were accurate and could be successfully estimated for up to 68% of hauled‐out seals in study areas. Our method accurately estimates individual body volume of pinnipeds in a time‐ and cost‐effective manner while minimising disturbance. While the approach is applied to pinnipeds here, the method could be adapted to further taxa that are otherwise challenging to obtain direct measurements from. Our proposed approach therefore has the potential to fill demographic research gaps, which will improve our ability to protect and conserve species into the future.

Sex-dependent shifts in body size and condition along replicated elevational gradients in a montane colonising ectotherm, the common wall lizard (Podarcis muralis).

In ectothermic animals, elevational gradients, such as mountainous environments, are often associated with shifts in body size, although patterns differ across taxa and contexts. Mountain landscapes are characterised by relatively rapid shifts in biotic and abiotic conditions along an elevational gradient, commonly referred to as elevational zonation. Such zonation can reduce the geographic scale at which organisms experience the effects of climate change. The upslope range shifts will expose organisms at the colonization front to sub-optimal conditions. We can expect these challenging conditions to influence many life-history traits including growth rates and reproductive output. We tested the hypothesis that body size varies across elevational gradients in a contemporary montane colonizer, the common wall lizard (Podarcis muralis). Further, we assessed active body temperatures and available environmental temperatures in an attempt to discern a potential abiotic factor that might drive such a pattern. We quantified body size in lizards along four replicate transects ranging from 400 to 2400m above sea level in the Pyrenees. Male body size decreased with increasing elevation. While female body size was invariant, females at higher elevation exhibited lower body condition. These results suggest that the effects of abiotic limitations or selective pressures experienced at the high-elevation colonisation front are sex-specific. Furthermore, lizards from both sexes were able to maintain similar field active body temperatures across elevation, despite reduced ambient temperature. If available temperatures limit activity periods or necessitate higher thermoregulatory investment, as suggested by our results, then further warming may benefit lizards and favour further upslope migration.

The relationship between body size and diet breadth in non‐web building spiders

Abstract The handling hypothesis assumes that large animals have broader diets than small animals because small animals are restricted to small prey while large animals can handle both small and large prey. On the other hand, the optimal foraging hypothesis assumes no relationship between predator body size and diet breadth because large predators should shift from small prey to large prey to maximize the net energy intake. Using the diets and body sizes of 89 non‐web building spider species obtained from public databases (World Spider Trait database, Spiders of Europe and World Spider Catalogue), we investigated the relationship between body size and diet breadth in this group of terrestrial arthropod predators. We found that the taxonomic niche diet breadth measured by Hill numbers (i.e., prey richness, Shannon index of diversity and Simpson index of equitability) had no significant relationship with spider body size. The minimum prey size did not show any relationship with spider body size. On the other hand, mean, maximum, range and variability in prey size increased with spider body size. The results provide support for both hypotheses. The pattern in prey taxonomic dimension supports the optimal foraging hypothesis, while the pattern in prey size dimension supports the handling hypothesis. Overall, the observed distinct patterns between the taxonomic and prey size niche axes can be caused by the fact that the non‐web building spiders utilize similar prey types that are however highly size‐structured.

Is Alcohol Consumption Pattern Dependent on Prenatal Sex-Steroids? A Digit Ratio (2D:4D) Study Among University Students.

There is evidence that alcohol consumption is influenced by prenatal sex steroids (as measured by digit ratio [2D:4D]). Here, we clarify the effect size of the relationship in a student (rather than a patient) population. There were 258 (169 women) participants. Digit length was measured directly with calipers. Alcohol use was evaluated by the Polish version of Alcohol Use Disorders Identification Test (AUDIT) and operationalized as total AUDIT scores and grams of alcohol/week. Digit ratios were sexually dimorphic (males < females). There were negative correlations between right 2D:4D and Dr-l (right 2D:4D minus left 2D:4D) and AUDIT scores and grams of alcohol/week in both sexes. Relationships varied from small (r = -0.29) to large (r = -0.69) and they were stronger in males in comparison to females and for right 2D:4D in comparison to Dr-l. In males only, there were small (r = 0.21) to moderate (r = 0.31) positive associations with body size (height, weight, and mean right digit length) and alcohol consumption. Multiple regression analyses showed relationships between digit ratios remained significant but those for body size did not. Alcohol consumption was negatively related to 2D:4D, suggesting high prenatal testosterone and low prenatal estrogen are linked to its consumption. Correlations varied in strength from small to large with the strongest found for right 2D:4D and for males. Positive relationships between body size and alcohol were small to moderate, confined to males, and were not independent of digit ratios. Prenatal androgenization may influence alcohol drinking patterns in non-clinical individuals.

Ontogenetic scaling of disc width with total length in west African batoids

AbstractMorphological scaling describes changes in the size or shape of one morphological character (e.g. mass, length, width, area etc.) as another increases in size. Understanding how morphological characters scale with body size can shed light on how natural selection influences morphology, and the nature of ecomorphological relationships through ontogeny. Batoids (Elasmobranchii: Batoidea) are a highly specialised lineage of cartilaginous fishes displaying extreme dorsoventral flattening. Despite this, little is known about morphological scaling in batoids compared to sharks. In this study we test the relationship between disc width and total length in five batoid species (Torpedo torpedo, Mobula tarapacana, Fontitrygon margarita, Raja parva, Rhinobatos irvinei) representing four orders that differ in both ecology and morphology, measured from artisanal fisheries in Western and Central Ghana. Whilst a lack of existing ecological data presents some limitations, our results are broadly consistent with ecomorphological theory previously applied to sharks. Moreover, we find that for some lineages (including some myliobatiform taxa) total length may represent a valid proxy for estimating overall body size. This finding has applications for body size and shape estimation in partially processed batoids obtained from fishing camps, and extinct taxa known only from incomplete or fragmented remains.

Unravelling the diversity of Posthodiplostomum Dubois, 1936 (Trematoda: Diplostomidae) in fish-eating birds from the Neotropical region of Mexico, with the description of a new species.

Adults of the genus Posthodiplostomum, Dubois, 1936 are parasites of fish-eating birds, mainly of the family Ardeidae, and are globally distributed. The genus currently comprises 35 species, although recent molecular evidence has shown that the diversity of the genus is underestimated since several candidate species have been recognized. In the Neotropical region of Mexico, at least 6 Posthodiplostomum lineages have been detected with metacercaria stages recovered from unrelated fish hosts. Here, we obtained adult specimens of Posthodiplostomum from 6 fish-eating birds representing 2 families (Butorides virescens, Ardea herodias, Nycticorax nycticorax, Tigrisoma mexicanum – Ardeidae, and Rynchops niger and Leucophaeus atricilla – Lariidae) from 4 localities in southern Mexico. Specimens were sequenced for 2 nuclear (28S and ITS1–5.8S–ITS2) and 1 mitochondrial (cox1) molecular marker. Phylogenetic analyses allowed us to link metacercariae and adult specimens and recognized a lineage, which was described morphologically. The new species can be distinguished from its congeners by its prosoma morphology and body size; this is the first described species in the Neotropical region of Mexico. Additionally, new host and locality records for P. macrocotyle and P. pricei are presented, expanding their geographical distribution range in the Americas.

Among-population variation in sexual size dimorphism of Nepa cinerea (Heteroptera: Nepomorpha)

AbstractNepa cinerea is a common aquatic predator. It is widely distributed in various aquatic biotopes of the Palaearctic. Body size is an important trait that impacts the fitness and survival of animals and thus their evolution. Like most insects, N. cinerea males are smaller than females, but sexual size dimorphism (SSD) has not been investigated. We investigated the extent of SSD, the validity of Rensch's rule, and morphological differences between nine populations based on 51 morphological parameters. Females were found significantly and marginally significantly larger than males in all but one population. However, no difference in body length was found between the populations. Population had a significant effect on 12 traits for females and only on 5 for males, showing that females are more variable than males. Specifically, differences were found in the length of the second and third leg pairs. We did not find any support for the Rensch's rule. Nevertheless, female body size and SDI (sexual dimorphism index) were positively correlated. We suggest that fecundity selection accounts for female-biased SSD in N. cinerea.

The osteology of Triisodon crassicuspis (Cope, 1882): New insights into the enigmatic "archaic" placental mammal group "Triisodontidae".

Following the end-Cretaceous mass extinction, mammals underwent an increase in body size, taxonomic diversity and ecological specialization throughout the Paleocene, exemplifying their adaptability. One especially enigmatic group is the "Triisodontidae", medium- to large-sized ungulate-like placentals from the Paleocene which are best known from their teeth that exhibit adaptations towards carnivory. The "triisodontids" were the first large carnivorous mammals and pre-date, and may have given rise to, Mesonychia, a group of more specialized placental carnivores. The "triisodontids" have been well-described from dental material, although very little is known about their postcrania. Here, we describe the postcrania of Triisodon crassicuspis-the most completely represented species of the genus to date-from a specimen (NMMNH P-72096) recovered from basal Torrejonian strata of the Nacimiento Formation in the San Juan Basin, New Mexico. Anatomical comparisons reveal that the forelimb long bones of Tri. crassicuspis are robust relative to its size, more so than other "triisodontids". Attachment sites on the ulna are evidence of well-developed muscles involved in powerful extension and flexion of the manus. In Tri. crassicuspis, the range of pronation-supination was limited as evident from the humeroradial morphology. Qualitative functional assessment of osteological features of the forelimb of Tri. crassicuspis is suggestive of terrestrial locomotion with at least moderate digging ability. Re-analyses of the dentition confirmed that Tri. crassicuspis had specializations for carnivory, and provide a body mass estimate of ca. 32-44 kg based on dental proxies. In summary, Tri. crassicuspis was a relatively large and powerful terrestrial animal, and one of the first known placentals to fill a largely carnivorous niche.

Body mass and growth rates predict protein intake across animals.

Organisms require dietary macronutrients in specific ratios to maximize performance, and variation in macronutrient requirements plays a central role in niche determination. Although it is well recognized that development and body size can have strong and predictable effects on many aspects of organismal function, we lack a predictive understanding of ontogenetic or scaling effects on macronutrient intake. We determined protein and carbohydrate intake throughout development on lab populations of locusts and compared to late instars of field populations. Self-selected protein:carbohydrate targets declined dramatically through ontogeny, due primarily to declines in mass-specific protein consumption rates which were highly correlated with declines in specific growth rates. Lab results for protein consumption rates partly matched results from field-collected locusts. However, field locusts consumed nearly double the carbohydrate, likely due to higher activity and metabolic rates. Combining our results with the available data for animals, both across species and during ontogeny, protein consumption scaled predictably and hypometrically, demonstrating a new scaling rule key for understanding nutritional ecology.