Negative association between host plant suitability and the fitness cost of resistance to Bacillus thuringiensis (Bacillales: Bacillaceae).

Transgenic crops producing Bacillus thuringiensis (Bt) toxins are commonly used for controlling insect pests. Nearby refuges of non-Bt host plants play a central role in delaying the evolution of resistance to Bt toxins by pests. Pervasive fitness costs associated with resistance, which entail lower fitness of resistant than susceptible individuals in refuges, can increase the ability of refuges to delay resistance. Moreover, these costs are affected by environmental factors such as host plant suitability, implying that manipulating refuge plant suitability could improve the success of the refuge strategy. Based on results from a previous study of Trichoplusia ni resistant to Bt sprays, it was proposed that low-suitability host plants could magnify costs. To test this hypothesis, we investigated the association between host plant suitability and fitness costs for 80 observations from 30 cases reported in 18 studies of 8 pest species from 5 countries. Consistent with the hypothesis, the association between plant suitability and fitness cost was negative. With plant suitability scaled to range from 0 (low) to 1 (high), the expected cost was 20.7% with a suitability of 1 and the fitness cost increased 2.5% for each 0.1 decrease in suitability. The most common type of resistance to Bt toxins involves mutations affecting a few types of midgut proteins to which Bt toxins bind to kill insects. A better understanding of how such mutations interact with host plant suitability to generate fitness costs could be useful for enhancing the refuge strategy and sustaining the efficacy of Bt crops.

Seed preference is only weakly linked to seed-type-specific feeding performance in a songbird.

The dehusking of seeds by granivorous songbirds is a complex process that requires fast, coordinated and sensory-feedback-controlled movements of beak and tongue. Hence, efficient seed handling requires a high degree of sensorimotoric skill and behavioural flexibility, since seeds vary considerably in size, shape and husk structure. To deal with this variability, individuals might specialise on specific seed types, which could result in greater seed handling efficiency of the preferred seed type, but lower efficiency for other seed types. To test this, we assessed seed preferences of canaries (Serinus canaria) through food choice experiments and related these to data of feeding performance, seed-handling skills and beak kinematics during feeding on small, spindle-shaped canary seeds and larger, spheroid-shaped hemp seeds. We found great variety in seed preferences among individuals: some had no clear preference, while others almost exclusively fed on hemp seeds, or even prioritized novel seed types (millet seed). Surprisingly, we only observed few and weak effects of seed preference on feeding efficiency. This suggests either that the ability to handle seeds efficiently can be readily applied across various seed types, or alternatively, that achieving high levels of seed-specific handling skills does not require extensive practice.

Seed preference is only weakly linked to seed-type-specific feeding performance in a songbird.

The dehusking of seeds by granivorous songbirds is a complex process that requires fast, coordinated and sensory-feedback-controlled movements of beak and tongue. Hence, efficient seed handling requires a high degree of sensorimotoric skill and behavioural flexibility, since seeds vary considerably in size, shape and husk structure. To deal with this variability, individuals might specialise on specific seed types, which could result in greater seed handling efficiency of the preferred seed type, but lower efficiency for other seed types. To test this, we assessed seed preferences of canaries (Serinus canaria) through food choice experiments and related these to data of feeding performance, seed handling skills and beak kinematics during feeding on small, spindle-shaped canary seeds and larger, spheroid-shaped hemp seeds. We found great variety in seed preferences among individuals: some had no clear preference, while others almost exclusively fed on hemp seeds, or even prioritized novel seed types (millet seed). Surprisingly, we only observed few and weak effects of seed preference on feeding efficiency. This suggests that either the ability to handle seeds efficiently can be readily applied across various seed types, or alternatively, it may indicate that achieving high levels of seed-specific handling skills does not require extensive practice.

Feeding selectivity and a functional trade-off in a benthic fish with a continuous morphological variation: an experimental test.

BACKGROUND: Functional trade-offs through ecological specializations are hypothesized to become causes of adaptive phenotypic divergence under divergent natural selection, where intermediate phenotypes may have the lowest fitness. Evidence of phenotypic divergence in a trade-off between populations experiencing different environmental/ecological conditions is abundant. However, traits in divergent selection sometimes present non-discrete (unimodal) variability, including intermediate phenotypes, although the underlying mechanisms are poorly documented. A benthic cyprinid fish, Pseudogobio esocinus, in Lake Biwa, central Japan, exhibits a large non-discrete/continuous variation in mouthpart morphology (from wide to narrow) within a lake population. The variation is linked with individual diets (i.e., the compositions of two different types of prey) even at a single site, and thus the variability is hypothesized to persist under divergent selection for prey usage. As a first step toward understanding the persistence mechanisms, here I examined the presence of morphology-dependent feeding selectivity and a functional trade-off in a laboratory experiment. RESULTS: When each experimental fish was simultaneously provided the different types of prey (chironomid larvae and amphipods), the fish mostly utilized chironomid larvae as primary prey. However, compared with the wider-mouthed fish, the narrower-mouthed fish took a larger proportion of amphipods as secondary prey by changing feeding (attacking) behavior. The intermediate-mouthed fish had lower feeding efficiency than the extreme-mouthed fish, indicating potential disadvantage of the intermediate phenotype. CONCLUSIONS: This experimental result supports the presence of morphology-dependent feeding performance and a functional trade-off with potential impacts on trait variability, which may favor specializations rather than generalizations. In the wild, however, there may be some situations for relaxing the trade-off, such as temporally fluctuating prey availability that could also favor generalizations depending on the conditions, and thus, both extreme and intermediate phenotypes may persist/coexist in a single habitat. Although further examinations, especially focusing on feeding efficiency for each prey type separated from the effects of prey selectivity, are needed, this case represents an opportunity to consider the possible mechanisms of the persistence of phenotypic variation that is maintained without divergence even in a trade-off.

The feeding apparatus of ants: an overview of structure and function.

Ants are a dominant family of eusocial terrestrial insects with a diversity of ecologies, lifestyles and morphologies. Ant diet preferences range from strict carnivory through omnivory to almost complete herbivory in species feeding on seeds or exudates of plant-sucking insects. While several studies have investigated ant feeding performance on different substrates, comparatively little is known about the functional morphology of the structures involved in food uptake or their diversification across the ants. To take stock of our current knowledge, we give an overview of how adult ants ingest food, followed by a morphological description of the mouthparts, preoral space and cephalic sucking pump. The mandibles are the most prominent mouthparts and have received considerable attention in the literature, so we focus on the maxillae and labium here. We present current hypotheses for the movement patterns of these parts and discuss morphological differences among ants that may be related to their ecological diversity. Finally, we give short comparisons of the ant condition with some other insects and vertebrates, as well as an outlook summarizing gaps in our knowledge. This sets the stage for future studies elucidating the connections between ant feeding mechanisms and mouthpart evolution. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.

Tomato Aphid (Aphis gossypii) Secreted Saliva Can Enhance Aphid Resistance by Upregulating Signaling Molecules in Tomato (Solanum lycopersicum).

This study investigated the impact of Aphis gossypii watery saliva on the induction of tomato (Solanum lycopersicum) plant resistance. To examine the role of A. gossypii saliva, we collected watery saliva from A. gossypii after a 48 h feeding period on an artificial diet. SDS-PAGE resolving gel 12% was used to separate the salivary proteins. Relative expression of gene analysis revealed that the intrusion of A. gossypii saliva dripping onto S. lycopersicum leaves triggered robust defense responses mediated by a signaling molecule, i.e., salicylic acid, while the signaling molecule's jasmonic acid-dependent defense responses were moderately activated. Aphid saliva infiltrated S. lycopersicum leaves slowed the intrinsic rate of population growth of A. gossypii and significantly reduced the number of nymphs produced daily, compared to untreated leaves. During a choice test with untreated S. lycopersicum, aphids showed a repellent response towards saliva-infiltrated S. lycopersicum. Moreover, the (EPG) electrical penetration graph analysis demonstrated that the eating pattern of A. gossypii compared to untreated S. lycopersicum, that had been exposed to saliva was negatively impacted. These results provide compelling evidence for the involvement of salivary components of A. gossypii in inducing resistance against aphids in S. lycopersicum plants. Furthermore, the study underscores the crucial role of watery saliva in the intricate interactions between aphids and plants. The activation of pathways was also part of the defensive response (jasmonic acid (JA), salicylic acid (SA) signaling molecules). The findings of this research deliver valuable insights into the potential of watery aphid saliva as a natural defense mechanism against aphid infestations in S. lycopersicum crops.

Using natricine snakes to test how prey type and size affect predatory behaviors and performance.

Introduction: Predation is a complex process for which behavior, morphology, and size of both predator and prey can affect the success and effectiveness of the predator. For predators such as snakes that swallow prey whole, gape ultimately limits prey size, but the behaviors used to select, capture, and consume prey and attributes of the prey can also affect maximal prey size. For example, swallowing live, struggling prey is difficult, but using coiling or envenomation to restrain or kill prey has evolved repeatedly in snakes. Methods: To test the potential benefits of these behaviors, we manipulated the type and size of prey, and determined how stereotyped predatory behavior was in a snake species (Liodytes rigida) that uses both coiling and envenomation to restrain and immobilize its formidable prey of crayfish. We also studied a close relative (Liodytes pygaea) that eats fish and salamanders to gain insights into the evolution of these traits. Results: For L. rigida, envenomation of hard-shell crayfish via their soft underside was very stereotyped (100% of feedings). Envenomation of soft-shell crayfish was less frequent (59% of feedings) but became more likely both with increased relative prey size and increased time after molt (hardness). L. rigida coiled more for hard-shell than soft-shell crayfish (77% vs. 30%). The probability of coiling was unaffected by prey size, but it increased with increased time after molt for the soft-shell crayfish. Liodytes rigida waited to swallow crayfish until they were completely immobile in 75% and 37% of the feedings with hard- and soft-shelled crayfish, respectively. Even with large prey L. pygaea never used coiling or envenomation, whereas previous studies of L. alleni, the sister species of L. rigida, observed non-lethal coiling without envenomation when eating hard-shell crayfish. Discussion: Our findings for the Liodytes clade of three species suggest that coiling evolved ancestral to the crayfish specialists (L. alleni; L. rigida), and envenomation by L. rigida subsequently evolved as an additional means of subduing formidable prey. The proximate benefits observed for coiling and envenomation in L. rigida support the evolutionary scenario that both traits evolved to enhance the feeding performance for more formidable prey.

Virulence of entomopathogenic fungi against fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) under laboratory conditions.

Maize is an essential crop of China. The recent invasion of Spodoptera frugiperda, also known as fall armyworm (FAW), poses a danger to the country's ability to maintain a sustainable level of productivity from this core crop. Entomopathogenic fungi (EPF) Metarhizium anisopliae MA, Penicillium citrinum CTD-28 and CTD-2, Cladosporium sp. BM-8, Aspergillus sp. SE-25 and SE-5, Metarhizium sp. CA-7, and Syncephalastrum racemosum SR-23 were tested to determine their effectiveness in causing mortality in second instars, eggs, and neonate larvae. Metarhizium anisopliae MA, P. citrinum CTD-28, and Cladosporium sp. BM-8 caused the highest levels of egg mortality, with 86.0, 75.3, and 70.0%, respectively, followed by Penicillium sp. CTD-2 (60.0%). Additionally, M. anisopliae MA caused the highest neonatal mortality of 57.1%, followed by P. citrinum CTD-28 (40.7%). In addition, M. anisopliae MA, P. citrinum CTD-28, and Penicillium sp. CTD-2 decreased the feeding efficacy of second instar larvae of FAW by 77.8, 75.0, and 68.1%, respectively, followed by Cladosporium sp. BM-8 (59.7%). It is possible that EPF will play an important role as microbial agents against FAW after further research is conducted on the effectiveness of these EPF in the field.

Relationship Between Feeding to Sleep During Infancy and Subsequent Childhood Disease Burden.

OBJECTIVE: To investigate the association of feeding to sleep during infancy and subsequent childhood health burdens. STUDY DESIGN: Information was collected from the parents of children who participated in the national health screening survey when the child was 9-12 months old. The exposure group included participants who were fed to sleep. The primary outcome was all-cause hospital admission (inpatient care, intensive care unit [ICU] admission, or general anesthesia) after age 24 months. Secondary outcomes were subsequent childhood diseases (ie, adenoidectomy and/or tonsillectomy, nasal polyps, allergic rhinitis, acute otitis media, asthma, pneumonia, and aspiration pneumonia), and growth status, as measured by weight-to-age and height-to-age z-scores. RESULTS: The study cohort consisted of 224 075 children who participated in the health screening program, 29 392 of whom (13.1%; 51% males) were fed to sleep. Exposure was associated with an increased risk of all-cause hospitalization after age 24 months (hazard ratio [HR], 1.05; 95% CI, 1.03-1.07), but not with admission to an ICU or receipt of general anesthesia. This also was related to adenoidectomy and/or tonsillectomy (HR, 1.08; 95% CI, 1.01-1.15), dental caries (HR, 1.32; 95% CI, 1.23-1.40), asthma (HR, 1.14; 95% CI, 1.14-1.24), pneumonia (HR, 1.10; 95% CI, 1.07-1.13), overweight (HR, 1.06; 95% CI, 1.03-1.09), and obesity (HR, 1.11; 95% CI, 1.06-1.16). CONCLUSIONS: Several adverse health outcomes are related to feeding to sleep during early childhood.

Effects of Complete Oral Motor Intervention and Nonnutritive Sucking Alone on the Feeding Performance of Premature Infants: A Systematic Review and Meta-Analysis.

We explore the effect of complete oral motor intervention (OMI) and nonnutritive sucking (NNS) alone on oral feeding in preterm infants through a meta-analysis. We searched the Embased, Medline, Cochrane Library, and Web of Science databases for randomized controlled trials up to 8 August 2023, based on established selection criteria. Quality evaluations of the studies were carried out by applying both the Cochrane risk of bias assessment tool and the Jadad scale. The outcome measures of three clinical indicators included transition time to oral feeding, weight gain, and hospitalization duration. We conducted a meta-analysis using a random-effects model to determine the pooled effect sizes, expressed as standardized mean differences (SMDs) and their corresponding confidence intervals (CIs). Additionally, we undertook a subgroup analysis and meta-regression to investigate any potential moderating factors. Eight randomized controlled trials with 419 participants were selected. Meta-analysis revealed that receiving a complete OMI had significantly reduced transition time compared with those receiving NNS alone in preterm newborns (SMD, -1.186; 95% CI, -2.160 to -0.212, p = 0.017). However, complete OMI had no significant effect on shortened hospitalization duration (SMD, -0.394; 95% CI, -0.979 to 0.192, p = 0.188) and increased weight gain (SMD, 0.346; 95% CI, -0.147 to 0.838, p = 0.169) compared with NNS alone. In brief, a complete OMI should not be replaced by NNS alone. However, we were unable to draw decisive conclusions because of the limitations of our meta-analysis. Future well-designed randomized controlled trials are necessary to confirm our conclusion.

Functional and hepatic metabolite changes in aquatic turtle hatchlings exposed to the anti-androgenic fungicide vinclozolin.

Many man-made chemicals that are released into water bodies in agricultural landscapes have been identified as endocrine disruptors and can cause serious impacts on the growth and survival of aquatic species living in these environments. However, very little attention has been paid to their toxicological effects in cultured non-fish species, such as aquatic turtles. We exposed hatchlings of the Chinese soft-shelled turtle (Pelodiscus sinensis) to different concentrations of vinclozolin (0, 5, 50 and 500 µg/L) for 60 days to assess physiological and metabolic impacts of this fungicide. Despite no death occurrence, hatchling turtles exposed to the highest concentration of vinclozolin consumed less food, grew more slowly (resulting in smaller body size after exposure) and performed more poorly in behavioral swimming tests than controls and turtles exposed to lower concentrations. Hepatic metabolite profiles acquired via liquid chromatography-mass spectrometry (LC-MS) revealed multiple metabolic perturbations related to amino acid, lipid, and fatty acid metabolism in animals exposed to environmentally relevant concentrations. Specifically, many critical metabolites involved in energy-related metabolic pathways (such as some intermediates in the tricarboxylic acid cycle, lactate, and some amino acids) were present in livers of hatchling turtles exposed vinclozolin, though at lower concentrations, reflecting energy metabolism dysregulation induced by exposure to this fungicide. Overall, our results suggest that the changes in growth and behavioral performances caused by chronic vinclozolin exposure may be associated with internal physiological and metabolic disorders mediated at the biochemical level.

Effect of Left and Right Semi-Elevated Side-Lying Positions on Feeding Performance of Preterm Infants.

OBJECTIVE: To determine the effect of right and left semi-elevated side-lying positions on the feeding performance and skills of bottle-fed preterm infants. DESIGN: A single-group, crossover experimental study. SETTINGS: Level 3 NICU of a training and research hospital in Istanbul. PARTICIPANTS: A total of 60 preterm infants born at 24 to 36 6/7 weeks gestation. METHODS: We collected data using an infant information form, feeding observation form, and the Turkish version of the Early Feeding Skills Assessment (EFS-Turkish). For each infant, we collected data for two feeds: one in the right and one in the left semi-elevated side-lying position. RESULTS: We found no difference between the right and left semi-elevated side-lying positions in the volume or percentage of food taken (p = .582 and p = .625, respectively), feeding duration (p = .901), or feeding efficiency (p = .423). We observed no significant differences between feedings in the left and right semi-elevated side-lying positions in mean EFS-Turkish total score (p = .251) or subscale scores (p > .05). CONCLUSION: Neonatal nurses can feed preterm infants in both directions of the semi-elevated side-lying position when following evidence-based feeding guidelines.

The bite force-gape relationship as an avenue of biomechanical adaptation to trophic niche in two salmonid fishes.

All skeletal muscles produce their largest forces at a single optimal length, losing force when stretched or shortened. In vertebrate feeding systems, this fundamental force-length relationship translates to variation in bite force across gape, which affects the food types that can be eaten effectively. We measured the bite force-gape curves of two sympatric species: king salmon (Oncorhynchus tshawytscha) and pink salmon (Oncorhynchusgorbuscha). Cranial anatomical measurements were not significantly different between species; however, peak bite forces were produced at significantly different gapes. Maximum bite force was achieved at 67% of maximum gape for king salmon and 43% of maximum gape for pink salmon. This may allow king salmon to use greater force when eating large or elusive prey. In contrast, pink salmon do not require high forces at extreme gapes for filter feeding. Our results illustrate that the bite force-gape relationship is an important ecophysiological axis of variation.

How Does the Intricate Mouthpart Apparatus Coordinate for Feeding in the Hemimetabolous Insect Pest Erthesina fullo?

The yellow marmorated stink bug, Erthesina fullo (Thunberg, 1783), is a major pest of certain tree fruits in Northeast Asia. To better understand the feeding mechanism of E. fullo, the fine structure of the mouthparts, including the distribution and abundance of sensilla, are examined with scanning electron microscopy (SEM), and their functions are observed directly under laboratory conditions. The feeding performance is described in detail and illustrated for the first time. The adult feeding process involves several steps, including exploring and puncturing of the host plant epidermis, a probing phase, an engorgement phase, and removal of the mouthparts from the host tissue. Proceeding from labium towards the mandibular stylets, the movement pattern becomes increasingly stereotypical, including the sensilla on the tip of the labium probing, the labium making an elbow-like bend between the first and second segment, the base of the stylet fascicle housing in the groove of the labrum, the mandibular stylets penetrating the site and maxillary stylets feeding. In terms of morphology, the mouthparts are similar to those of other Heteroptera, consisting of a triangular pyramidal labrum, a tube-like and segmented labium with a deep groove on the anterior side, and a stylet fascicle consisting of two mandibular and two maxillary stylets. The four-segmented labium has five types of sensilla basiconica, three types of sensilla trichodea, two types of sensilla campaniformia and 1 type of sensilla coeloconica. Among them, sensilla trichodea one and sensilla basiconica one are most abundant. The tripartite apex of the labium is covered with abundant sensilla trichodea three and a few sensilla basiconica 5. The mandibular stylet tips have two nodules preapically on the dorsal margin of the convex external surface, which may help in penetrating plant tissue and anchoring the mouthparts. The externally smooth maxillary stylets interlock to form a larger food canal and a smaller salivary canal. The structure and function of the mouthparts are adapted for the phytophagous feeding habit in this species. Similarities and differences between the mouthparts of E. fullo and those of other Heteroptera are discussed.

Sex-specific ontogenetic patterns of cranial morphology, theoretical bite force, and underlying jaw musculature in fishers and American martens.

The carnivoran cranium undergoes tremendous growth in size and development of shape to process prey as adults and, importantly, these ontogenetic processes can also differ between the sexes. How these ontogenetic changes in morphology actually relate to the underlying jaw musculature and overall bite performance has rarely been investigated. In this study, I examined sex-specific ontogenetic changes in cranial morphology, jaw adductor muscles, and theoretical bite force between subadults and adults in the fisher (Pekania pennanti) and American marten (Martes americana). I found evidence that cranial size alone does not completely explain ontogenetic increases in bite forces as found in other mammalian species. Instead, cranial shape development also drives ontogenetic increases in relative bite force by broadening the zygomatic arches and enlargement of the sagittal crest, both of which enable relatively larger jaw adductor muscles to attach. In contrast, examination of sexual dimorphism within each age-class revealed that cranial shape dimorphism did not translate to dimorphism in either size-corrected bite forces or size-corrected physiological cross-sectional area of the jaw adductor muscles. These results reveal that morphological size and shape variation can have different influences on bite performance depending on the level of intraspecific variation that is examined (i.e. ontogenetic versus sexual dimorphism).

New methods and tools to assess nutritive sucking in new-borns: effect of different feeding bottles on nutritive performance.

Nutritive sucking is a fundamental process assuring the primary infant nourishment in the first months of life. When feeding is impaired for pathological conditions, the growth of the infant may be delayed with a cascade effect on the overall development. While literature studied nutritive sucking development in infants with feeding problems, like in severe premature babies or with low weight at birth, few works assesses to what extent different feeding bottles may influence feeding performance of healthy new-borns. This work proposes a method for functional characterization of feeding bottles based on the most promising and reliable indices used to quantitatively assess feeding skills in clinical applications. Thirty healthy newborns have been fed with two different bottles instrumented with a device for feeding monitoring. Their impact on feeding performance is objectively assessed and discussed. The approach presented here, even if preliminary, paves the way to a new method for functional characterization of feeding bottles. Further studies may allow to confirm our analyses with a higher number of bottles and infants.

Range-extending coral reef fishes trade-off growth for maintenance of body condition in cooler waters.

As ocean waters warm due to climate change, tropical species are shifting their ranges poleward to remain within their preferred thermal niches. As a result, novel communities are emerging in which tropical species interact with local temperate species, competing for similar resources, such as food and habitat. To understand how range-extending coral reef fish species perform along their leading edges when invading temperate ecosystems, we studied proxies of their fitness, including somatic growth (length increase), feeding rates, and body condition, along a 730-km latitudinal gradient situated in one of the global warming hotspots. We also studied co-occurring temperate species to assess how their fitness is affected along their trailing edges under ocean warming. We predicted that tropical fishes would experience reduced performance as they enter novel communities with suboptimal environmental conditions. Our study shows that although tropical fish maintain their body condition (based on three proxies) and stomach fullness across all invaded temperate latitudes, they exhibit decreased in situ growth rates, activity levels, and feeding rates in their novel temperate environment, likely a result of lower metabolic rates in cooler waters. We posit that tropical fishes face a growth-maintenance trade-off under the initial phases of ocean warming (i.e. at their leading edges), allowing them to maintain their body condition in cooler temperate waters but at the cost of slower growth. Temperate fish exhibited no distinct patterns in body condition and performance along the natural temperature gradient studied. However, in the face of future climate change, when metabolism is no longer stymied by low water temperatures, tropical range-extending species are likely to approach their native-range growth rates along their leading edges, ultimately leading to increased competitive interactions with local species in temperate ecosystems.

Dry versus wet and gross: Comparisons between the dry skull method and gross dissection in estimations of jaw muscle cross-sectional area and bite forces in sea otters.

Bite force is a measure of feeding performance used to elucidate links between animal morphology, ecology, and fitness. Obtaining live individuals for in vivo bite-force measurements or freshly deceased specimens for bite force modeling is challenging for many species. Thomason's dry skull method for mammals relies solely on osteological specimens and, therefore, presents an advantageous approach that enables researchers to estimate and compare bite forces across extant and even extinct species. However, how accurately the dry skull method estimates physiological cross-sectional area (PCSA) of the jaw adductor muscles and theoretical bite force has rarely been tested. Here, we use an ontogenetic series of southern sea otters (Enhydra lutris nereis) to test the hypothesis that skeletomuscular traits estimated from the dry skull method accurately predicts test traits derived from dissection-based biomechanical modeling. Although variables from these two methods exhibited strong positive relationships across ontogeny, we found that the dry skull method overestimates PCSA of the masseter and underestimates PCSA of the temporalis. Jaw adductor in-levers for both jaw muscles and overall bite force are overestimated. Surprisingly, we reveal that sexual dimorphism in craniomandibular shape affects temporalis PCSA estimations; the dry skull method predicted female temporalis PCSA well but underestimates male temporalis PCSA across ontogeny. These results highlight the importance of accounting for sexual dimorphism and other intraspecific variation when using the dry skull method. Together, we found the dry skull method provides an underestimation of bite force over ontogeny and that the underlying anatomical components driving bite force may be misrepresented.

Temperature-mediated feeding between spring-associated and riverine-associated congeners, with implications for community segregation.

Freshwater fish communities segregate along water temperature gradients attributed in part to temperature-mediated physiological processes that affect species fitness. In spring complexes of southwest USA, spring complexes with narrow range of water temperatures are dominated by a community of fishes (i.e., spring-associated fishes), whereas riverine habitats with wide-range of water temperatures are dominated by a different community of fishes (i.e., riverine-associated fishes). The purpose of this study was to test a prediction of the concept that temperature-mediated species performance is a mechanism in maintaining community segregation. We predicted that a spring-associated fish (Largespring Gambusia Gambusia geiseri) would feed first and more often in a pairing with a riverine-associated fish (Western Mosquitofish G. affinis) at an average spring temperature (23 °C) and that the riverine-associated fish would feed first and more often in a pairing with the spring-associated fish at a warm riverine temperature (30 °C). Among four trails consisting of 30 pairings, at the spring complex temperature (23 °C), Largespring Gambusia had a greater number of first feeds (mean ± 1 SD, 5.0 ± 0.82) than Western Mosquitofish (2.5 ± 1.73) and had greater mean number of total feeds (1.9 ± 0.31) than Western Mosquitofish (0.81 ± 0.70). At the riverine environment temperature (30 °C), Western Mosquitofish had a greater number of first feeds (5.25 ± 1.71) than Largespring Gambusia (2.5 ± 1.73) and had greater mean number of total feeds (2.78 ± 1.05) than Largespring Gambusia (0.94 ± 0.68). Our findings suggest that temperature-mediated species performance could be maintaining segregation between the two fish communities. This study benefits our understanding of distributional patterns and improves threat assessments of stenothermal aquatic organisms.

Full oral feeding is possible before discharge even in extremely preterm infants.

AIM: This study described the steps needed to achieve full oral feeding before discharge in a group of very and extremely preterm (EPT) infants. We analysed the effects of oral feeding skills on discharge timing and on weight gain during their neonatal intensive care unit (NICU) stay. METHODS: A prospective cross-sectional observational study of 100 infants who were <32 weeks of gestation (GA) was conducted at the Division of Neonatology, Graz, Austria, from March 2014 to February 2015. Patients were stratified into two groups: those who were <28 weeks at birth and those who were 28 weeks and over. Velocity of oral feeding skills attainment and weight gain were analysed. RESULTS: All infants successfully acquired oral feeding skills during hospitalisation. The median GA at which full oral feeding skills were reached was 37 + 1 weeks in EPT and 34 + 5 weeks in very preterm infants. More immature neonates showed worse feeding performances and lower weight increments during oral feeding steps. CONCLUSION: Our study confirmed the role of GA in the development of oral feeding skills in the most premature babies. It also raises the question of whether expected daily weight gain should be targeted according to GA.