Differences In Diet Composition Research Articles

Impact of a mixed culture of Lactobacillus casei and L. lactis on in vitro ruminal fermentation and the growth of feedlot steers fed barley-based diets

The effect of a direct-fed microbial (DFM) poduct containing a mixed culture of Lactobacillus casei and L. lactis on in vitro ruminal fermentation of barley-grain/barley-silage-based backgrounding and finishing diets and on growth performance and carcass characteristics of feedlot cattle was evaluated during backgrounding (84 d) and finishing (140 d) of 100 Hereford × Angus steers (initial body weight = 280 ± 15.5 kg). The inclusion rates of DFM in the in vitro study were 4, 8, 12 and 16 million colony forming units (CFU) of lactic acid bacteria (LAB) kg-1 DM of substrate. Total in vitro volatile fatty acids (VFA) production increased at 6 and 12 h of incubation (P < 0.01; linear response) when the backgrounding diet was supplemented with DFM. Dry matter digestibility and VFA production also increased (P < 0.05) during a 12-h fermentation of the finishing diet. Steers were randomly allocated to one of four dietary treatments that comprised feeding DFM tp provide 0 (control), 4 × 107, 8 × 107, or 12 × 107 CFU kg-1 diet DM. Average daily gain (ADG, kg) and feed efficiency (G:F; kg gain kg-1 DM consumed) of steers improved (P = 0.002 and 0.001, respectively) as a result of feeding DFM during the backgrounding period, but not during the finishing period. Saleable meat and rib eye area decreased (P = 0.038, linear; and P = 0.041, quadratic) with DFM supplementation. The results indicated that supplementing barley-grain/barley-silage-based feedlot cattle diets with 12 × 107 CFU of the mixed culture of lactobacilli used in these studies could improve ruminal fermentation, ADG and G:F in backgrounding feedlot steers. However, supplementation during the finishing period may not be warranted in terms of growth performance and carcass characteristics. Differences in the microbial ecology of the intestinal tract as a result of differences in diet composition may account for the varied response between the backgrounding and finishing periods.Key words: Beef cattle, direct-fed microbial, growth performance, Lactobacillus casei, Lactobacillus lactis, ruminal fermentation

Trophic ecology of New Zealand triplefin fishes (Family Tripterygiidae)

In many vertebrate radiations, food partitioning among closely related taxa is a key factor in both the maintenance of species diversity and the process of diversification. We compared diet composition and jaw morphology of 18 New Zealand triplefin species (F. Tripterygiidae) to examine whether species have diversified along a trophic axis. These fishes predominantly utilised small, mobile benthic invertebrates, and interspecific differences in diet composition appeared to be mainly attributable to habitat- or size-dependent feeding behaviour. Although there were differences in the relative size of the bones comprising the oral jaw apparatus between species, the majority showed an apparatus consistent with a relatively high velocity, low force jaw movement indicative of a diet of evasive prey. Phylogenetic comparative analyses showed that the evolution of jaw lever ratios and diet breadth was best explained by a non-directional model in which character changes have occurred randomly and independent of phylogeny. The mode of diet breadth evolution was gradual and the tempo has not accelerated or slowed down over time. The mode of evolution for the jaw lever ratios has been gradual for the opening but punctuated for the closing levers, suggesting that evolutionary changes have occurred rapidly for the latter trait. The tempo of trait evolution for the jaw opening levers has not accelerated or slowed down over time, while the tempo for the jaw closing levers has accelerated towards the tips of the tree, which is suggestive of species level adaptation. The lack of phylogenetic signal in diet breadth and jaw lever ratios appears most likely to be a correlated response to the marked habitat diversification in this group, and is thus the passive outcome of prey availability in species-specific habitat types. Overall, the trophic ecology of New Zealand’s triplefin fauna parallels the generalist strategy typical of the family worldwide, suggesting that trophic resource partitioning has not been an important factor in the evolution of these fishes.

Using stable isotopes to investigate individual diet specialization in California sea otters (Enhydra lutris nereis)

Differences in diet composition among conspecifics (dietary specialization) have been documented across a broad range of taxonomic groups and habitats, and such variation at the individual level is increasingly recognized as an important component of diversity in trophic interactions. Accurate identification of individual dietary specialization, however, requires longitudinal dietary records that are labor-intensive and cost-prohibitive to obtain for many species. Here we explore the use of stable isotopes (delta13C and delta15N) as a promising technique for detecting and quantifying patterns of individual dietary specialization. Southern sea otters (Enhydra lutris nereis) offer a unique opportunity for testing this approach because (1) they consume a wide variety of prey that span multiple trophic levels, habitats, and ecologically defined functional groups; and (2) individual diet specialization can be validated with existing observational data. We analyzed the isotopic composition of sea otter vibrissae (n = 31) in order to characterize inter- and intra-individual variation in sea otter diets at Monterey Bay, California, USA. At the population level, sea otters showed substantial variation in both delta13C and delta15N values, occupying nearly all of the "isotopic space" created by the diversity of isotopic signatures of potential prey taxa. Most of the variation in sea otter vibrissae was accounted for by differences between individuals, with much less contributed by within-individual variation. A majority of sea otters (approximately 80%) showed relatively little temporal variability in isotopic composition, suggesting that the proportional composition of most individuals' diets is relatively constant over time; a few individuals (approximately 20%) exhibited a high degree of intra-vibrissa isotopic variability, suggesting seasonal shifts in diet composition. These results and our interpretation of them were supported by long-term observational data on the diets of radio-tagged sea otters from the same population (n = 23). Our results demonstrate that stable isotopes can provide an efficient tool for measuring individual- and population-level dietary breadth and may be useful for studying populations where longitudinal data on individuals would otherwise be impossible to acquire. This will be critical for examining the causes and consequences of dietary variation within and among consumer populations, thereby improving our understanding of these important ecological and evolutionary processes at the community level.

Intake and digestion of horned guan Oreophasis derbianus diets measured in three Mexican zoos

We conducted nutritional analyses of diets offered to and ingested by seven pairs of horned guans (Oreophasis derbianus) in three zoos. Digestibility was calculated with individually housed birds (n=1 at each zoo). Diets offered varied widely among institutions, both in ingredients fed as well as in nutrient composition. Feeding selectivity was evident through differences in composition of diets offered vs. consumed, with fruit (bananas, grape, and/or plantain) and avocado (when offered) highly preferred; green leaves, poultry pellets, and other vegetables comprised lesser proportions of the diet. All facilities fed 2-3X more food than consumed, allowing a great degree of choice of preferred items and potentially consumption of nutritionally imbalanced diets-in particular, mineral constituents. Diets were highly digestible; dry matter (DM) digestion coefficients ranged from 70 to approximately 90%; protein digestibility varied from 30 to 80%; fat was >90% digestible. Diet composition was compared with known nutritional requirements of domestic avian species, and feeding recommendations discussed. Despite the wide variability in nutrient composition of diets eaten (i.e. protein 6-10% of DM; fat 2-17% of DM), no overt health problems were noted and all pairs had successfully reproduced on these diets. It is suggested that horned guans may have nutrient requirements more similar to those suggested for other frugivorous birds than values determined for poultry as the physiologic model. Comparisons with native food items, as well as more detailed nutrient balance studies, may provide even better guidelines for captive management of this highly endangered species.

Diet Selection by the Swamp Wallaby (Wallabia bicolor): Feeding Strategies under Conditions of Changed Food Availability

Mammals can have either generalized (mixed) or specialized diets. We expected swamp wallabies (Wallabia bicolor) to have mixed diets, and predicted a negative relationship between the selection of a food type and its relative availability (negative frequency dependence). We collected data on diets in a native Eucalyptus forest where the relative availability of food types (defined as 5 plant functional groups: ferns, forbs, monocots, shrubs, and trees) had been altered by timber harvesting. A comparison of diets between individuals living in 2 habitat types (unharvested forest and 5-year-old regenerating areas) showed that in both habitats forbs were the major dietary component, although moderate amounts of shrubs and monocots also were consumed. Trees and ferns were eaten less at unharvested sites, and more at 5-year-old sites. Nonmetric multidimensional scaling followed by a multiresponse permutation procedure demonstrated a substantial difference in diet composition between the habitats (multiresponse permutation procedure: A = 0.20, P < 0.001), but when analyzed using an index of diet selection, the difference was smaller (A = 0.05, P = 0.04). Three alternative analyses demonstrated negative frequency dependence in many cases, a result generally consistent with a mixed feeding strategy. With the exception of tree foliage, selection was positively correlated with the relative availability of at least 1 other food type, and largely uncorrelated with 3 forage quality variables (nitrogen, water, and dry matter digestibility). Additional data at a finer resolution and in different seasons are required to test the generality of these conclusions.

Methods for calculating activity budgets compared: a case study using orangutans

The results of comparisons of behavioral data between individuals, age-sex classes, seasons, sites and possibly even species may depend on sample size and the computational method used. To establish whether these are valid concerns, we compared results for percentage time spent feeding on major food types (fruit, leaves, flowers, invertebrates, bark, pith and other) for two orangutan populations in Sabangau (24 months) and Tuanan (29 months), Indonesian Borneo. Both the minimum follow limit included in analyses and the computational method used produced small, but statistically significant, differences in the results obtained, and the differences were more common for food types eaten less frequently. In addition, using different computational methods produced more significant differences than did including different minimum follow lengths in analyses. The computational method used also influenced the results of tests for differences in diet composition between age-sex classes. Thus, the method used can influence the results obtained and, hence, it is important to state explicitly the minimum follow limit included and computational method used to compile averages, and to ensure standardization in methods when comparing data between age-sex classes, time periods, field sites or species.

Assessing diet composition of seahorses in the wild using a non destructive method: Hippocampus reidi (Teleostei: Syngnathidae) as a study-case

This paper presents the results of the first analysis of the natural diet of Hippocampus reidi, one of the most sought after seahorse species in the international aquarium trade. Its main goals were to investigate food items and prey categories consumed by the species, and to discuss feeding strategy and inter and intra-individual components of niche breadth. Data were gathered from October 2005 to September 2006 at the Mamanguape estuary, State of Paraíba, NE Brazil. Food items from seahorses anaesthetized with clove oil were obtained by using a modified version of the flushing method, and were counted and identified to the lowest possible taxonomic level. Specimens were marked and had their height, sex, life and reproductive stage recorded, and then returned to the same place where they were found for the further assessment of anaesthetization/gut flushing on seahorses. Food items were analyzed using frequency of occurrence, relative abundance, index of preponderance and prey-specific abundance using the points method. The graphic method of Amundsen et al. (1996) was used to interpret the feeding strategy and contribution to niche breadth. Nematodes and crustaceans were the most important items found, the latter item usually being the most commonly found in the gut contents of syngnathids. No significant differences in diet composition were found between reproductive stages, however, a higher proportion of large items were consumed by the larger seahorses. The feeding strategy and niche breadth analysis suggests that H. reidi has a generalist feeding strategy, with high variation between phenotypes. Our results suggest that the anaesthetization-flushing technique has the potential to be a useful tool in seahorse research.

Impact of diet selected by cattle and sheep grazing heathland communities on nutrient supply and faecal micro-flora activity

In the UK the funding mechanism for moorland restoration is implemented primarily through agri-environment schemes, yet comparatively little is known of the nutritional consequences of selecting diets from semi-natural vegetation communities. In this study the feed intake and diet digestibility of four groups of animals grazing heathland swards with low (8%) and high (61%) percentages of cover of Calluna vulgaris were estimated using n-alkanes. The impact of diet choice on metabolic status was monitored through blood sampling, and complementary in vitro studies investigating species/breed differences in gut microbial populations were carried out using faecal samples. Two breeds of sheep (Welsh Mountain (WM) and Scottish Blackface (SBF)) and two breeds of cattle (Welsh Black (WB) and Continental cross (CX)) grazed the experimental sites during two separate 14-day sampling sessions, in July and September, respectively. Between-species and between-breed differences in intake and diet digestibility were recorded. Chemical analysis of the main sward components highlighted the poor nutritional value of heathland species to ruminants, with most major plant groups having crude protein concentrations of less than 100 g kg −1 DM and digestible organic matter in the dry matter values of 0.400–0.500 g g −1. Overall, the blood metabolite results indicate that the intake of both energy and protein was less than optimal to supply even maintenance requirements. Low dietary protein intakes were linked to low serum urea concentrations in all animals. The serum non-esterified fatty acid concentrations indicated a feed energy deficit for both sheep and cattle, with the data suggesting that the deficit was greater for cattle than for sheep. While differences in diet composition could be linked to differences in metabolic profile, diet selected had little apparent impact on faecal micro-floral characteristics, with the gas production data indicating very few significant differences in the activity of microbial populations between different breeds of the same species. Overall the results demonstrate that careful management is required when domestic livestock graze such swards if animal welfare is not to be compromised. They also highlight the poor production potential of such vegetation communities, and the related repercussions with regards to economic sustainability.

Feeding ecology of two high-order predators from south-eastern Australia: the coastal broadnose and the deepwater sharpnose sevengill sharks

Quantifying the feeding ecology of marine predators is essential for understanding their trophic interactions and their potential regulatory effects in marine ecosystems. I quantified the feed- ing ecology of 2 related predators that overlap only in part in spatial distribution: the coastal broad- nose Notorynchus cepedianus and the deepwater sharpnose Heptranchias perlo sevengill sharks. I found the following: These 2 shark species have different diet specialisation patterns, but show sim- ilarities in their prey handling mode. N. cepedianus has a generalised diet, whereas H. perlo shows high specialisation and lower prey diversity. For both shark species, small, medium and large individ- uals use different strategies for handling different prey groups. H. perlo preys largely on deepwater teleosts, mainly Lepidorhynchus denticulatus, with larger individuals (901 to 1365 mm total length, TL) also consuming high proportions of large predatory teleosts of the families Gempylidae and Trichiuridae. N. cepedianus has a diverse diet. Small individuals (≤900 mm TL) prey largely on teleosts and secondarily on chondrichthyans. Medium individuals (901 to 1520 mm TL) prey primar- ily on chondrichthyans and secondarily on teleosts. Chondrichthyans (mainly Mustelus antarcticus) are also the main prey of large N. cepedianus (>1700 mm TL), but this group also shows a greater preference (than small and medium individuals) for fur seals. Despite the overall differences in dietary composition and the minimal overlap in spatial distribution, the 2 shark species consume prey that migrate from deep to coastal waters (ommastrephid squid and gempylid fish).

Effects of dietary intervention on MRI activity, de- and remyelination in the cuprizone model for demyelination

Whether differences in diet composition may influence demyelinating diseases remains controversial. The aim of this study was to analyse if diets with a different composition of polyunsaturated fatty acids (PUFAs) could influence demyelination and remyelination in cuprizone fed mice, a widely used animal model for de- and remyelination. C57Bl/6 mice were fed with 0.2% cuprizone on three different diets. The diets consisted of the same ingredients, except the lipid source, which came from 1) salmon fillets rich in marine n − 3 polyunsaturated fatty acids (PUFAs), 2) cod liver oil rich in marine n − 3 PUFAs, or 3) a control diet containing soybean oil rich in n − 6 PUFAs. After 5 weeks of cuprizone treatment, the mice given salmon-cuprizone had significantly less hyperintense lesion volume on brain magnetic resonance imaging (MRI) than the two other groups ( P < 0.0005). After 6 weeks of cuprizone treatment, the salmon-cuprizone group had less demyelination in the corpus callosum, as measured with luxol fast blue (LFB) ( P < 0.0005) and anti-proteolipid protein (PLP) ( P = 0.014). The salmon-cuprizone group also had enhanced remyelination compared to the cod liver oil-cuprizone group (LFB; P = 0.003, PLP; P = 0.018). This study indicates that a fish rich diet may offer a protective role in demyelination. The source of N − 3 PUFAs, or other components in the fish, may be important, as no effect of a cod liver oil based diet was observed. This may be of importance related to the discrepant results in dietary intervention studies for demyelinating diseases.

BEHAVIOR RATHER THAN DIET MEDIATES SEASONAL DIFFERENCES IN SEED DISPERSAL BY ASIAN ELEPHANTS

Digestive physiology and movement patterns of animal dispersers determine deposition patterns for endozoochorously dispersed seeds. We combined data from feeding trials, germination tests, and GPS telemetry of Asian elephants (Elephas maximus) to (1) describe the spatial scale at which Asian elephants disperse seeds; (2) assess whether seasonal differences in diet composition and ranging behavior translate into differences in seed shadows; and (3) evaluate whether scale and seasonal patterns vary between two ecologically distinct areas: Sri Lanka's dry monsoon forests and Myanmar's (Burma) mixed-deciduous forests. The combination of seed retention times (mean 39.5 h, maximum 114 h) and elephant displacement rates (average 1988 m in 116 hours) resulted in 50% of seeds dispersed over 1.2 km (mean 1222-2105 m, maximum 5772 m). Shifts in diet composition did not affect gut retention time and germination of ingested seeds. Elephant displacements were slightly longer, with stronger seasonal variation in Myanmar. As a consequence, seed dispersal curves varied seasonally with longer distances during the dry season in Myanmar but not in Sri Lanka. Seasonal and geographic variation in seed dispersal curves was the result of variation in elephant movement patterns, rather than the effect of diet changes on the fate of ingested seeds.

Stable isotope ratios in Cape gannets around the southern coasts of Africa reveal penetration of biogeographic patterns in oceanic signatures

The southern coasts of Africa are influenced by two major oceanic currents, leading to biogeographic patterns in inshore and offshore species assemblages, and in the stable isotope signatures of suspended particulate matter and filter-feeding mussels. We used the stable isotope ratios of carbon ( 13C/ 12C) and nitrogen ( 15N/ 14N) from the blood and feathers of adult and chick Cape gannets ( Morus capensis) to investigate whether the geographic differences observed at the lower levels in the marine communities are deep penetrating effects that reach top predators. Additionally, we evaluated whether trophic segregation occurs between adult and reared chick gannets, and whether a shift to wintering habitat occurs in adults. The study was conducted during the 2006 breeding season on Bird Island in the Agulhas system, and on Malgas and Ichaboe Islands, in the south and north Benguela respectively. Our results showed significant differences in the isotope ratios of members of different colonies, but no intra-colony differences between tissues or age groups. These results indicate that there is neither age-related nor temporal segregation in the diet of members of the same colony. Feather isotopic values suggest that adults remain all year round in the same habitats, and do not undertake long migration after reproduction. Since all gannets tend to target similar prey, we attributed among-colony differences in isotope signatures mostly to the oceanic conditions experienced by the main prey of birds rather than substantial differences in diet composition. Overall, isotopic signatures segregate the two current systems, with depleted carbon values in the Agulhas and enriched nitrogen values in the upwelled waters of the Benguela. Within the Benguela birds from Ichaboe in the north had higher δ 15N values than those from Malgas in the south, which we attributed to differences in the functioning of the upwelling cells in the vicinity of the two colonies. Finally, slight variation in the proportion of main prey and discards from fisheries may contribute to the variation in the stable-isotope signatures between colonies in the Benguela.

Is the red spotted green frog Hypsiboas punctatus (Anura: Hylidae) selecting its preys? The importance of prey availability

The study of the feeding ecology of amphibians is an old issue in herpetology. Notwithstanding, the lack of food resources data in many studies of amphibians feeding has lead to partial understanding of frog feeding strategies. In this study we evaluate the trophic selectivity of a red spotted green frog (Hypsiboas punctatus) population from a Middle Paraná River floodplain pond in Argentina, and discuss the importance of prey availability data when interpreting results from diet analysis. We analyzed the gut contents of 47 H. punctatus adults and compared frog's diet with the environmental food resources. Prey availability was estimated by systematically seep-netting the microhabitat where anurans were localized foraging. We identified 33 taxonomic categories from gastrointestinal contents. Numerically, the most important prey categories were dipterans, followed by hemipterans, homopterans and coleopterans. The diet similarity between males and females was high and no statistical differences in diet composition were found. The most abundant food resources in the environment were dipterans, coleopterans, homopterans and collembolans. In order to assess whether frogs were selecting their preys, we calculated Pianka's niche overlap index and Jacobs' electivity index comparing gut contents to prey availability data. Trophic niche overlap was medium but significantly higher than expected by chance. The electivity index indicated that H. punctatus foraged dipterans slightly above their environmental abundance. Among the secondary preys, hemipterans were foraged selectively, homopterans were consumed in the same proportion to their occurrence in the environment, coleopterans were foraged quite under their availability and collembolans were practically ignored by frogs. Without food resources data, H. punctatus could be classified as a specialist feeder, but dipterans also were quite abundant in the environment. Our results show that H. punctatus fit better as a generalist feeder, foraging on their main food item and some secondary preys in similar proportion to their environmental availability; even though other secondary preys are being selectively preferred or ignored by frogs. Our data illustrate the importance of including the resource availability data on diet studies to improve the understanding of amphibian feeding ecology.

Adipocyte Gene Expression Is Altered in Formerly Obese Mice and As a Function of Diet Composition 3

In the development of obesity, the source of excess energy may influence appetite and metabolism. To determine the effects of differences in diet composition in obesity, mice were fed either a high-carbohydrate diet (HC; 10% fat energy) or a high-fat energy–restricted diet (HFR; 60% fat energy) over 18 wk in weight-matched groups of mice. To identify obesity-associated genes with persistently altered expression following weight reduction, mice were fed either a standard low-fat diet (LF; 10% fat energy), an unrestricted high-fat diet (HF; 60% fat energy), or a HF diet followed by weight reduction (WR). Mice fed a HF diet had significantly greater gonadal fat mass and higher whole blood glucose concentrations than mice fed an HC diet. Of the mice fed a high-fat diet, total body weight and serum insulin concentrations were greater in HF than in HFR. Microarray analysis revealed that HF vs. HC feeding resulted in global differences in adipocyte gene expression patterns. Although we identified genes whose expression was altered in both moderately and severely obese mice, there were also a large number of genes with altered expression only in severe obesity. Formerly obese, WR mice did not differ significantly from lean controls in total body weight or physiological measures. However, microarray analysis revealed distinctly different patterns of adipocyte gene expression. Furthermore, there were 398 genes with altered expression in HF mice that persisted in WR mice. Genes with persistently altered expression following obesity may play a role in rebound weight gain following weight reduction.

Spatial and temporal variation in the diet of Steller sea lions in the Kodiak Archipelago, 1999 to 2005

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 360:265-283 (2008) - DOI: https://doi.org/10.3354/meps07383 Spatial and temporal variation in the diet of Steller sea lions in the Kodiak Archipelago, 1999 to 2005 Jane McKenzie*, Kate M. Wynne University of Alaska Fairbanks, School of Fisheries and Ocean Science, 118 Trident Way, Kodiak, Alaska 99615, USA *Email: janemckenzie@malpage.com ABSTRACT: Spatial and temporal variation in the diet of Steller sea lions Eumetopias jubatus was investigated using scat (fecal) samples collected from 4 regions in the Kodiak Archipelago. Over 2700 scats with identifiable prey were collected from the northern, eastern, southern and western sides of Kodiak Island from 1999 to 2005. Of 76 prey types identified using hard remains, the most important species in terms of frequency of occurrence and numerical abundance were Pacific sand lance Ammodytes hexapterus, walleye pollock Theragra chalcogramma, arrowtooth flounder Atheresthes stomias, Pacific cod Gadus macrocephalus, salmon Oncorhynchus spp., and Pacific herring Clupea pallasi. Significant differences in diet composition were found among regions, seasons, and years, suggesting that the diet of sea lions is strongly influenced by local and temporal distributions and abundances of prey. Herring dominated scat collections from the west coast and accounted for most (14 to 30%) of the differences in regional diet in spring and winter. Annual variation in diet was relatively low in winter, whereas spring and fall diets varied from year to year, with regional-specific shifts in dominant prey. Results from our study generally agree with diet studies conducted in the 1990s, but differ markedly in the relative importance of the major prey species. KEY WORDS: Eumetopias jubatus · Prey · Seasonal · Diet overlap · Forage fish · Gulf of Alaska · Theragra chalcogramma · Ammodytes hexapterus Full text in pdf format Supplementary appendix PreviousNextCite this article as: McKenzie J, Wynne KM (2008) Spatial and temporal variation in the diet of Steller sea lions in the Kodiak Archipelago, 1999 to 2005. Mar Ecol Prog Ser 360:265-283. https://doi.org/10.3354/meps07383Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 360. Online publication date: May 22, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Differences in feeding ecology among three co-occurring species of wrasse (Teleostei: Labridae) on rocky reefs of temperate Australia

The foraging behaviours and dietary compositions of three co-occurring labrids (Ophthalmolepis lineolatus, Notolabrus gymnogenis and Pictilabrus laticlavius), which are conspicuous on rocky reefs in temperate south-eastern Australia, were investigated between 2003 and 2005. SCUBA observations at two locations showed that the feeding intensity, and hence the associated effects of these fishes on rocky reef invertebrate prey, was temporally consistent. Relative differences in the contributions of ingested prey and use of different feeding microhabitats demonstrated that the feeding ecology differed significantly among the three species. Thus, O. lineolatus fed on proportionately higher volumes of polychaetes, polyplacophorans, marginellid gastropods (especially Austroginella sp.), bivalves and echinoids, which were sighted opportunistically in a wide selection of microhabitats, but particularly in sand/rubble. Ambush hunting was used regularly by smaller N. gymnogenis and all sizes of P. laticlavius to forage on amphipods, small decapods and small gastropods at algal bases or fronds and Diopatra dentata tubes. Amphipods were similarly important in the diet of smaller O. lineolatus. Larger N. gymnogenis foraged opportunistically over an increased reef area and made greater use of microhabitats that offered minimal prey refuge (e.g. sand/rubble, bare rock/steel) from which common prey, in particular decapods, were obtained. The significant intra- and inter-specific differences in dietary compositions, allied with differences in the use of feeding microhabitats, would facilitate co-occurrence of these three conspicuous species and contribute to maintaining high richness of labrid species in reef systems. Echinoids were regularly consumed by each species but they made a moderate contribution to the diet of only O. lineolatus, which suggests that only one of the three labrids is likely to play a significant role in regulation of echinoid densities in these rocky reef habitats. However, the broad diets and diverse forging strategies employed by these labrid species imply that they have a system-wide influence on invertebrate prey on rocky reefs.

Siphonophores off a riverine system in the southern Gulf of Mexico: factors affecting their distribution and spatial niche breadth and overlap

Environmental factors determining the spatial pattern of the whole siphonophore community, as well as the hydrological occurrence ranges, small-scale vertical distribution, and spatial niche breadth and overlap of 23 siphonophore species collected off a riverine system in the southern Gulf of Mexico were analysed. A total of 149 zooplankton samples were collected in different strata of the water column (from 0 to 100 m) over a grid of 23 oceanographic stations during low (April) and high (October) rainy periods. Temperature and salinity measurements were taken with a CTD probe. Considering both seasons, salinity fluctuated between 30.7 and 37.0, and temperature between 18.2 and 29.0°C. Under these conditions, the hydrological occurrence ranges of species were analysed. Data on siphonophore biovolumes in the upper 30-m layer were subjected to a regression tree (RT) analysis taking the zooplankton biomass, the distance to the shore, the temperature, and the salinity as predictable variables. Results of the RT analysis showed that the distance from the shore, food availability, and temperature were among the most important factors affecting siphonophore spatial distribution. Food availability had a positive influence on the siphonophores distribution, whereas temperatures higher than 28.1°C seemed to depress most siphonophore populations. Diphyes dispar moderately dominated the community and represented 30% of the total biovolume. The calycophorans Abylopsis tetragona, A. eschscholtzi, Diphyes bojani, and Chelophyes appendiculata were the most generalist species as revealed by their niche breadth values, and Enneagonum hyalinum endured the widest salinity conditions (30.7–37.0) and was mainly distributed in coastal waters. The second most abundant species, the physonect Agalma okeni, exhibited a low mean niche overlap value with the calycophoran species. We hypothesise that differences in diet composition between physonects and calycophorans are the main cause of those low niche overlap values.

Visceral fat and total body fat mass correlate differently with hormones in rat

Forty-eight 67-day-old male Wistar rats (330+/-5g) were fed ad libitum either with a lipid enriched diet or a standard laboratory chow. Half of each sub-group was submitted to training. Training and difference in diet composition induced nonsignificant changes in body adiposity. Visceral fat (perirenal adipose tissue mass) was correlated with leptin (r=0.35, p=0.02) and insulin (r=0.38, p=0.01). Total body fat mass (measured by DEXA) was correlated with leptin only (r=0.58, p=0.003). Other correlations between perirenal adipose tissue or fat mass and adiponectin or insulin like growth factor 1 were nonsignificant. These results suggest that, in rat like in human, visceral fat development is linked with insulin insensitivity.

Food habits of Geoffroy's cat (Leopardus geoffroyi) in the central Monte desert of Argentina

Geoffroy's cat (Leopardus geoffroyi) is a little-known South American felid. Here we report the first detailed data on its seasonal food habits in a protected area of the central Monte desert, Argentina. We collected and analyzed 182 scats, identifying a total of 441 prey items, with 2.4±1.5 prey items per scat (range=1–10). Our results confirm that, as with most other felids, Geoffroy's cat is a small-sized predator specialized in capturing vertebrates. Small mammals were the most frequent prey items, representing at least the 63.3% of the food items in each season. The Sigmodontinae rodents Akodon molinae and Calomys musculinus were the most important prey throughout the study period, whereas birds and reptiles were consumed mainly during warmer seasons. Seasonal differences in diet composition were higher between warmer and colder seasons, suggesting that diet composition is constrained by seasonal fluctuation and disponibility of prey.

Mercury and stable isotopes of carbon and nitrogen in mink

Total Hg concentrations and values of stable isotopes (delta(15)N, delta(13)C) in tissues of mink (Mustela vison) captured in Rhode Island (USA) during winters of 1999 to 2004 were statistically distinct based on location. Mink captured in salt marsh environments (salt marsh group mink [SMGM]) had significantly lower mean Hg concentrations in liver and muscle tissue, and significantly higher delta(15)N and delta(13)C values in muscle, than those in corresponding samples of mink from upland freshwater locations (upland group mink [UPGM]). Stomach content samples obtained from the mink carcasses showed that fish, frogs, and crayfish were the dominant food items in UPGM, but in SMGM, fish predominated. Significant correlations were found for total Hg concentrations and stable isotope values between stomach contents and tissues. Comparisons of increases in Hg concentrations and delta(15)N values from stomach contents to muscle tissue showed nonsignificant differences between UPGM and SMGM for Hg concentrations (SMGM, factor of 4.2; UPGM, factor of 3.9) and delta(15)N values (SMGM, difference of 3.9 per thousand; UPGM, difference of 3.1 per thousand). These results suggest that the length of the trophic step and the extent of accumulation of Hg were approximately equal in both mink groups despite the differences in dietary composition and possible differences in accumulation of organic and inorganic Hg. The correspondence of stable isotope values and Hg concentrations between mink tissues and their stomach contents indicates that use of stomach content analysis to identify major prey items, followed by collection and analysis of appropriate field prey, may represent an approach for estimating Hg exposure to mink.