Investigating the link between morphological characteristics and diet in an island population of omnivorous reptiles (Sphenodon punctatus)

The morphological characteristics that impact feeding ecology in ectotherms, particularly reptiles, are poorly understood. We used morphometric measures and stable isotope analysis (carbon-13 and nitrogen-15) to assess the link between diet and functional morphology in an island population of an evolutionarily unique reptile, the tuatara (Sphenodon punctatus). First, we established a significant positive correlation between overall body size, gape size, and fat store in tuatara (n=56). Next, we describe the relationship between stable isotope profiles created from whole blood and nail trim samples and demonstrate that nail trims offer a low-impact method of creating a long-term dietary profile in ectotherms. We used nitrogen-15 values to assess trophic level in the population and found that tuatara on Takapourewa forage across multiple trophic levels. Finally, we found a significant relationship between gape size and carbon-13 (linear regression: P<0.001), with tuatara with large gapes showing dietary profiles that suggest a higher intake of marine (seabird) prey. However, whether body size or gape size is the primary adaptive characteristic allowing for more optimal foraging is yet unknown.

This article has an associated First Person interview with the first author of the paper.

Spring diet and energy intake of tundra swan (Cygnus columbianus) at the Yellow River National Wetland in Baotou, China

The Yellow River National Wetland in Baotou, China is an important resting and energy replenishment place for many migratory birds, such as tundra swan (Cygnus columbianus). The energy supply of food available at stopover sites plays an important role in the life cycle of migratory birds. In order to understand diet composition and energy supply of tundra swans for further protection of them, in this study, fecal of tundra swans (C. columbianus) were collected and fecal microhistological analysis was conducted to analyze the feeding habits and the energy supply. Results showed that: (1) tundra swans (C. columbianus) mainly fed on twelve species of plants from five families, including corn (Zea mays), quinoa (Chenopodium album) and rice (Oryza sativa), this is related to local crops and abundant plants. (2) The energy provided by crops to tundra swans (C. columbianus) was significantly higher than other abundant plants in wetlands (P < 0.05), corn and rice were the most consumed food, and other abundant wetland plants play complementary roles. (3) The daily energy intake of tundra swans (C. columbianus) was much higher than their daily energy consumption, the daily net energy intake of tundra swans (C. columbianus) was 855.51 ± 182.88 kJ (mean ± standard deviations). This suggested that the wetland provides energy for continue migrating to the tundra swan (C. columbianus). For further protection of tundra swans (C. columbianus) and other migratory birds, the Baotou Yellow River National Wetland environment and the surrounding farmland habitat should be protected.

Fatty acids composition in yellow-legged (Larus michahellis) and lesser black-backed (Larus fuscus) gulls from natural and urban habitats in relation to the ingestion of anthropogenic materials

Urban habitats offer spatially and temporally predictable anthropogenic food sources for opportunistic species, such as several species of gulls that are known to exploit urban areas and take advantage of accessible and diverse food sources, reducing foraging time and energy expenditure. However, human-derived food may have a poorer nutritional quality than the typical natural food resources and foraging in urban habitats may increase birds' susceptibility of ingesting anthropogenic debris materials, with unknown physiological consequences for urban dwellers. Here we compare the fatty acids (FA) composition of two opportunistic gull species (the yellow-legged gull, Larus michahellis, and the lesser black-backed gull, Larus fuscus) from areas with different levels of urbanization, to assess differences in birds' diet quality among foraging habitats, and we investigate the effects of ingesting anthropogenic materials, a toxicological stressor, on gulls' FA composition. Using GC-MS, 23 FAs were identified in the adipose tissue of both gull species. Significant differences in gulls' FA composition were detected among the three urbanization levels, mainly due to physiologically important highly unsaturated FAs that had lower percentages in gulls from the most urbanized habitats, consistent with a diet based on anthropogenic food resources. The deficiency in omega (ω)-3 FAs and the higher ω-6:ω-3 FAs ratio in gulls from the most urbanized location may indicate a diet-induced susceptibility to inflammation. No significant differences in overall FA composition were detected between gull species. While we were unable to detect any effect of ingested anthropogenic materials on gulls' FA composition, these data constitute a valuable contribution to the limited FA literature in gulls. We encourage studies to explore the long-term physiological effects of the lower nutritional quality diet for urban dwellers, and to detect the sub-lethal impacts of the ingestion of anthropogenic materials.

Mobile applications for the sport and exercise nutritionist: a narrative review

Mobile technology is widespread in modern society, and the applications (apps) that they run can serve various purposes. Features such as portability, ease of communication, storage, and relative low cost may make such technology attractive to practitioners in several fields. This review provides a critical narrative on the existing literature for apps relevant to the field of sport and exercise nutrition. Three main areas are discussed: (1) dietary analysis of athletes, (2) nutrition education for athletes, (3) estimating body composition. The key purpose of the review was to identify what literature is available, in what areas apps may have a benefit over traditional methods, and considerations that practitioners should make before they implement apps into their practice or recommend their use to coaches and athletes.

Plastic debris and natural food in two commercially important fish species from the coast of Peru

The aim of this study was to evaluate the presence of plastic debris in the stomach contents of two commercially important species Ethmidium maculatum and Mugil cephalus from Peru and relate their characteristics to their diet. The contents of 1820 stomachs were analyzed visually to detect the presence of plastics and prey. Of the analyzed samples, 0.3% contained nine microplastic fragments (0.72-4.54 mm) and one mesoplastic fragment (6.65 mm). Green and blue plastics of polyethylene and polypropylene were the most common. In E. maculatum, copepods were the main prey, followed by diatoms and decapods, and they exhibited the highest amount of plastics. In M. cephalus, the main prey were diatoms, copepods, and dinoflagellates, and they exhibited only one type of microplastic. Although the characteristics of the plastics and the prey of these species may be related (sizes-colors), more research is required to understand this problem in commercially important fishery resources in Peru.

Diet and occurrences of the letter-winged kite in a predation refuge

Nomadism is an advantageous life history strategy for specialised predators because it enables the predator to respond rapidly to changes in prey populations. The letter-winged kite (Elanus scriptus) is a nomadic nocturnal bird of prey endemic to arid and semi-arid zones of Australia. Letter-winged kites prey almost exclusively on nocturnal rodents and are often associated with rodent irruptions, but little is known about the ecology of letter-winged kites inside their core range. The Strzelecki Desert contains a known dingo-mediated predation refuge for native rodents. In this manuscript, we compare kite sightings, predator activity, and small mammal populations across survey sites in the Strzelecki Desert where dingoes were common and where dingoes were rare and use publicly available data from the Atlas of Living Australia (ALA) to assess trends in the occurrence of kites in the region. Ninety-five percent of ALA observations occurred in areas where dingoes were common. Similarly, all our observations of kites occurred where dingoes were common and during an extended population irruption of Notomys fuscus. Notomys fuscus was the most frequent item in the letter-winged kite diet at our study sites. We suggest that there is significant evidence that these sites in the Strzelecki Desert form part of the core range for the letter-winged kite whose use of this area is facilitated by a predation refuge for rodents mediated by the dingo. We conclude that predation refuges mediated by dingoes could be a factor driving the distributions of letter-winged kites and other predators of rodents, particularly nomadic predators.

Are Virginia opossums really ecological traps for ticks? Groundtruthing laboratory observations

Virginia opossums (Didelphis virginiana) are a common synanthrope in North America, and serve as host to many species of ectoparasites. Research on captive Virginia opossums estimated that opossums eat, on average, 5500 larval ticks (Acari: Ixodidae) per week. To investigate this apparent preference exhibited by opossums for ingesting ticks, we comprehensively analyzed stomach contents of 32 Virginia opossums from central Illinois. Using a dissecting microscope, we searched the contents exhaustively for ticks and tick body parts, without sieving or pre-rinsing the stomach contents. We did not locate any ticks or tick parts in the stomach contents of Virginia opossums. We also performed a vigorous literature search for corroborating evidence of tick ingestion. Our search revealed 23 manuscripts that describe diet analyses of Virginia opossums, 19 of which were conducted on stomach or digestive tract contents and four of which were scat-based analyses. None of the studies identified ticks in their analyses of diet items. We conclude that ticks are not a preferred diet item for Virginia opossums. Considering that wildlife unconditioned to laboratory conditions may exhibit non-typical behaviors, we recommend that lab-based studies of wildlife behavior be groundtruthed with studies based in natural conditions.

Ingestion of anthropogenic materials by yellow-legged gulls (Larus michahellis) in natural, urban, and landfill sites along Portugal in relation to diet composition

Pollution is a global concern, increasing rapidly throughout marine and terrestrial ecosystems, and affecting many species. Urbanization enhances waste production, leading to the opening of landfills that constitute a spatially and temporally predictable food source for opportunistic species. Several species of gulls are known to exploit and breed in urban areas, taking advantage of accessible and diverse food resources. The exploitation of anthropogenic food subsidies at sea (e.g. fishery discards), urban sites, and landfills leads to debris ingestion by gulls with potential negative effects. Here we characterize anthropogenic debris ingested by yellow-legged gulls (Larus michahellis) along Portugal, by analysing the content of pellets collected in (1) natural and urban breeding locations, and in (2) urban and landfill resting sites, to assess seasonal patterns in the ingestion of anthropogenic debris. We also relate diet with the presence of anthropogenic debris. Debris materials were found in 28.8% of pellets from breeding locations (natural and urban) and in 89.7% of pellets from resting sites (urban and landfill). Gulls from the most urbanized breeding location exhibited higher levels of ingested materials during the entire breeding cycle, however, gulls from a natural breeding site also ingested high levels of debris during the pre-breeding season. At resting sites, small seasonal differences were detected in the number and mass of debris items ingested, which were both higher during spring and summer. Gulls that typically fed on pelagic fish had significantly less sheet and fragment plastics in their pellets. The presence of certain debris categories in gull pellets was positively related to the presence of some prey items, suggesting that gulls may accidentally ingest debris while foraging at multiple habitats. The quantity of anthropogenic materials ingested by gulls from urban locations and landfills indicates a need for improved waste management.

In the absence of specific advice, what do patients eat and avoid? Results from a community based diet study in patients suffering from rheumatoid arthritis (RA) with a focus on potassium

Rheumatoid arthritis (RA) is a painful disabling difficult to treat disease. Clinicians and guidelines invariably focus on drugs. Diet is important but lacks robust data. We carried out a comprehensive analytical study in Indian (Asian) patients.

METHODS

141 consenting symptomatic chronic RA patients [mean age 46 years) center and 165 unrelated healthy control subjects (mean age 36 years) completed a a-priori validated food frequency questionnaire in a cross-sectional non-random design study under the supervision of a nutritionist. All patients were under standard rheumatology care. A 3 day retrospective recall record captured dietary data for all subjects. National Indian guidelines were adopted for diet analytics. Standard statistical analysis was carried out; significant p < 0.05.

RESULTS

Daily diet was found to be significantly deficient in calories and consumption of proteins, calcium and potassium when compared to healthy subjects. It was also inadequate for several nutrients when compacted to recommended daily allowance. The proportion of carbohydrates (65%), proteins (15%) and fat (25%) in daily diet was consistent with Indian standards (healthy). Women patients reported higher deficiency. 44% patients consumed vegetarian diet and showed lesser pain and better function compared to non-vegetarians (not significant). 44% patients reported dietary restriction; higher swollen joint counts in patients following any dietary restriction (p = 0.01) or Ayurveda (ancient Indian medicinal system) advise (p = 0.01) or consuming night shade vegetables (p = 0.002).

CONCLUSION

Dietary inadequacy and in particular for protein and potassium was identified in patients of RA. Any form of dietary restriction did not seem to improve RA. Specific dietary needs of RA patients and in particular impact of potassium deficiency needs further research.

Next-generation sequencing analysis of Pardosa pseudoannulata's diet composition in different habitats

Spiders are the most common and predominant predators in terrestrial ecosystems. The predatory behavior of spiders affects the energy flow across the food web within an ecosystem. Traditiaonal methods for analyzing spider diets such as field observation, anatomy and faeces analysis are not suitable for spider experiments due to spiders’ special dietary behavior. The molecular method based on the specific primers of prey DNA seems to be inefficient either in spite of its wide application in diet analysis. As the next-generation sequencing (NGS) technology becomes prevalent in many different areas, several cases of the NGS-based analysis of mammal diets have been published. This study analyzed the diet differences of Pardosa pseudoannulata (Araneae: Lycosidae) in four habitats (a wetland, a tea plantation, an alpine meadow and a paddy field) by using the NGS technology, combined with the DNA barcode method. The results suggested that the Pardosa pseudoannulata feed on a broad range of prey, and 7 orders and 24 families of insects were detected in the four investigated habitats. Moreover, it is found that the diet diversity of Pardosa pseudoannulata is greatly influenced by their living environments and seasons. In a nutshell, this study established an NGS-based methodology for spider diets analysis, and the results provided some basic materials to inform the protection and utilization of the Pardosa pseudoannulata as a potential eco-friendly predator against pests.

Do frogs really eat cardamom? Understanding the myth of crop damage by amphibians in the Western Ghats, India

In the Western Ghats of India, amphibians are culled at cardamom plantations since they are perceived to consume cardamom. To better understand the relationship between amphibians and cardamom, a study was undertaken at these plantations, which harbor numerous threatened and range-restricted amphibians. We undertook questionnaire surveys with 298 respondents at 148 plantations across southern India. Time-activity budget and diet analysis surveys were undertaken to determine whether amphibians really consumed cardamom. The conception that amphibians eat cardamom was found to be widespread especially among small-sized plantations, leading to negative perceptions and a lack of interest in amphibian conservation. The plantation community perceives a substantial economic loss due to amphibians, even though this is non-existent as revealed by our field surveys. These perceptions would lead to a continued intolerance of amphibian presence in plantations. A suitable outreach initiative re-affirming facts and spreading awareness on the positive role of amphibians would need to be conducted to negate this age-old myth.

Selection of a marker gene to construct a reference library for wetland plants, and the application of metabarcoding to analyze the diet of wintering herbivorous waterbirds

Food availability and diet selection are important factors influencing the abundance and distribution of wild waterbirds. In order to better understand changes in waterbird population, it is essential to figure out what they feed on. However, analyzing their diet could be difficult and inefficient using traditional methods such as microhistologic observation. Here, we addressed this gap of knowledge by investigating the diet of greater white-fronted goose Anser albifrons and bean goose Anser fabalis, which are obligate herbivores wintering in China, mostly in the Middle and Lower Yangtze River floodplain. First, we selected a suitable and high-resolution marker gene for wetland plants that these geese would consume during the wintering period. Eight candidate genes were included: rbcL, rpoC1, rpoB, matK, trnH-psbA, trnL (UAA), atpF-atpH, and psbK-psbI. The selection was performed via analysis of representative sequences from NCBI and comparison of amplification efficiency and resolution power of plant samples collected from the wintering area. The trnL gene was chosen at last with c/h primers, and a local plant reference library was constructed with this gene. Then, utilizing DNA metabarcoding, we discovered 15 food items in total from the feces of these birds. Of the 15 unique dietary sequences, 10 could be identified at specie level. As for greater white-fronted goose, 73% of sequences belonged to Poaceae spp., and 26% belonged to Carex spp. In contrast, almost all sequences of bean goose belonged to Carex spp. (99%). Using the same samples, microhistology provided consistent food composition with metabarcoding results for greater white-fronted goose, while 13% of Poaceae was recovered for bean goose. In addition, two other taxa were discovered only through microhistologic analysis. Although most of the identified taxa matched relatively well between the two methods, DNA metabarcoding gave taxonomically more detailed information. Discrepancies were likely due to biased PCR amplification in metabarcoding, low discriminating power of current marker genes for monocots, and biases in microhistologic analysis. The diet differences between two geese species might indicate deeper ecological significance beyond the scope of this study. We concluded that DNA metabarcoding provides new perspectives for studies of herbivorous waterbird diets and inter-specific interactions, as well as new possibilities to investigate interactions between herbivores and plants. In addition, microhistologic analysis should be used together with metabarcoding methods to integrate this information.

Discrimination of grasshopper (Orthoptera: Acrididae) diet and niche overlap using next-generation sequencing of gut contents

Species of grasshopper have been divided into three diet classifications based on mandible morphology: forbivorous (specialist on forbs), graminivorous (specialist on grasses), and mixed feeding (broad-scale generalists). For example, Melanoplus bivittatus and Dissosteira carolina are presumed to be broad-scale generalists, Chortophaga viridifasciata is a specialist on grasses, and Melanoplus femurrubrum is a specialist on forbs. These classifications, however, have not been verified in the wild. Multiple specimens of these four species were collected, and diet analysis was performed using DNA metabarcoding of the gut contents. The rbcLa gene region was amplified and sequenced using Illumina MiSeq sequencing. Levins' measure and the Shannon-Wiener measure of niche breadth were calculated using family-level identifications and Morisita's measure of niche overlap was calculated using operational taxonomic units (OTUs). Gut contents confirm both D. carolina and M. bivittatus as generalists and C. viridifasciata as a specialist on grasses. For M. femurrubrum, a high niche breadth was observed and species of grasses were identified in the gut as well as forbs. Niche overlap values did not follow predicted patterns, however, the low values suggest low competition between these species.

Bayesian estimation of predator diet composition from fatty acids and stable isotopes

Quantitative analysis of stable isotopes (SI) and, more recently, fatty acid profiles (FAP) are useful and complementary tools for estimating the relative contribution of different prey items in the diet of a predator. The combination of these two approaches, however, has thus far been limited and qualitative. We propose a mixing model for FAP that follows the Bayesian machinery employed in state-of-the-art mixing models for SI. This framework provides both point estimates and probability distributions for individual and population level diet proportions. Where fat content and conversion coefficients are available, they can be used to improve diet estimates. This model can be explicitly integrated with analogous models for SI to increase resolution and clarify predator–prey relationships. We apply our model to simulated data and an experimental dataset that allows us to illustrate modeling strategies and demonstrate model performance. Our methods are provided as an open source software package for the statistical computing environment R.

Application of DNA barcoding for identification of freshwater carnivorous fish diets: Is number of prey items dependent on size class for Micropterus salmoides?

Understanding predator–prey interactions is a major challenge in ecological studies. In particular, the accurate identification of prey is a fundamental requirement in elucidating food-web structure. This study took a molecular approach in determining the species identity of consumed prey items of a freshwater carnivorous fish (largemouth bass, Micropterus salmoides), according to their size class. Thirty randomly selected gut samples were categorized into three size classes, based on the total length of the bass. Using the universal primer for the mtDNA cytochrome oxidase I (COI) region, polymerase chain reaction (PCR) amplification was performed on unidentified gut contents and then sequenced after cloning. Two gut samples were completely empty, and DNA materials from 27 of 28 gut samples were successfully amplified by PCR (success rate: 96.4%). Sequence database navigation yielded a total of 308 clones, containing DNA from 26 prey items. They comprised four phyla, including seven classes, 12 orders, and 12 families based on BLAST and BOLD database searches. The results indicate that largemouth bass show selective preferences in prey item consumption as they mature. These results corroborate a hypothesis, presence of ontogenetic diet shift, derived through other methodological approaches. Despite the practical limitations inherent in DNA barcoding analysis, high-resolution (i.e., species level) identification was possible, and the predation patterns of predators of different sizes were identifiable. The utilization of this method is strongly recommended for determining specific predator–prey relationships in complex freshwater ecosystems.