Synthetic analysis of trophic diversity and evolution in Enantiornithes with new insights from Bohaiornithidae

Enantiornithines were the dominant birds of the Mesozoic, but understanding of their diet is still tenuous. We introduce new data on the enantiornithine family Bohaiornithidae, famous for their large size and powerfully built teeth and claws. In tandem with previously published data, we comment on the breadth of enantiornithine ecology and potential patterns in which it evolved. Body mass, jaw mechanical advantage, finite element analysis of the jaw, and traditional morphometrics of the claws and skull are compared between bohaiornithids and living birds. We find bohaiornithids to be more ecologically diverse than any other enantiornithine family: Bohaiornis and Parabohaiornis are similar to living plant-eating birds; Longusunguis resembles raptorial carnivores; Zhouornis is similar to both fruit-eating birds and generalist feeders; and Shenqiornis and Sulcavis plausibly ate fish, plants, or a mix of both. We predict the ancestral enantiornithine bird to have been a generalist which ate a wide variety of foods. However, more quantitative data from across the enantiornithine tree is needed to refine this prediction. By the Early Cretaceous, enantiornithine birds had diversified into a variety of ecological niches like crown birds after the K-Pg extinction, adding to the evidence that traits unique to crown birds cannot completely explain their ecological success.

Microbial diversity and metabolic function in duodenum, jejunum and ileum of emu (Dromaius novaehollandiae)

Emus (Dromaius novaehollandiae), a large flightless omnivorous ratite, are farmed for their fat and meat. Emu fat can be rendered into oil for therapeutic and cosmetic use. They are capable of gaining a significant portion of its daily energy requirement from the digestion of plant fibre. Despite of its large body size and low metabolic rate, emus have a relatively simple gastroinstetinal (GI) tract with a short mean digesta retention time. However, little is known about the GI microbial diversity of emus. The objective of this study was to characterize the intraluminal intestinal bacterial community in the different segments of small intestine (duodenum, jejunum, and ileum) using pyrotag sequencing and compare that with the ceca. Gut content samples were collected from each of four adult emus (2 males, 2 females; 5-6 years old) that were free ranged but supplemented with a barley-alfalfa-canola based diet. We amplified the V3-V5 region of 16S rRNA gene to identify the bacterial community using Roche 454 Junior system. After quality trimming, a total of 165,585 sequence reads were obtained from different segments of the small intestine (SI). A total of 701 operational taxonomic units (OTUs) were identified in the different segments of small intestine. Firmicutes (14-99%) and Proteobacteria (0.5-76%) were the most predominant bacterial phyla in the small intestine. Based on species richness estimation (Chao1 index), the average number of estimated OTUs in the small intestinal compartments were 148 in Duodenum, 167 in Jejunum, and 85 in Ileum, respectively. Low number of core OTUs identified in each compartment of small intestine across individual birds (Duodenum: 13 OTUs, Jejunum: 2 OTUs, Ileum: 14 OTUs) indicated unique bacterial community in each bird. Moreover, only 2 OTUs (Escherichia and Sinobacteraceae) were identified as core bacteria along the whole small intestine. PICRUSt analysis has indicated that the detoxification of plant material and environmental chemicals seem to be performed by SI microbiota, especially those in the jejunum. The emu cecal microbiome has more genes than SI segments involving in protective or immune response to enteric pathogens. Microbial digestion and fermentation is mostly in the jejunum and ceca. This is the first study to characterize the microbiota of different compartments of the emu intestines via gut samples and not fecal samples. Results from this study allow us to further investigate the influence of the seasonal and physiological changes of intestinal microbiota on the nutrition of emus and indirectly influence the fatty acid composition of emu fat.

Functional traits of the world's late Quaternary large-bodied avian and mammalian herbivores

Prehistoric and recent extinctions of large-bodied terrestrial herbivores had significant and lasting impacts on Earth's ecosystems due to the loss of their distinct trait combinations. The world's surviving large-bodied avian and mammalian herbivores remain among the most threatened taxa. As such, a greater understanding of the ecological impacts of large herbivore losses is increasingly important. However, comprehensive and ecologically-relevant trait datasets for extinct and extant herbivores are lacking. Here, we present HerbiTraits, a comprehensive functional trait dataset for all late Quaternary terrestrial avian and mammalian herbivores ≥10 kg (545 species). HerbiTraits includes key traits that influence how herbivores interact with ecosystems, namely body mass, diet, fermentation type, habitat use, and limb morphology. Trait data were compiled from 557 sources and comprise the best available knowledge on late Quaternary large-bodied herbivores. HerbiTraits provides a tool for the analysis of herbivore functional diversity both past and present and its effects on Earth's ecosystems.

Tributaries of the hepatic vein in the ostrich (Struthio camelus)

Abstract The ostrich (Struthio camelus, Linnaeus 1758) is the largest bird in the world. It is of great economic importance in Africa and is found across several countries. With developments in breeding systems, morphological studies that facilitate the application of the knowledge are necessary, considering the species has unique anatomical features. The objective of the present study was to describe the major tributaries of the hepatic vein in the species. Ten viscera of adult individuals of both sexes, which were injected with Neoprene latex through the hepatic vein, were used to visualize their tributaries. After the vascular repletion, the tissues were fixed and conserved in 10% formaldehyde aqueous solution. The hepatic carrier system was dissected and photo-documented. The left hepatic vein receives blood from the proventricle and gastric ventricle, while the right hepatic vein is responsible for the drainage of blood into the following organs: spleen, through the proventriculosplenic vein; pancreas, through the pancreaticoduodenal vein; jejunum, through the jejunum trunk; and the colon, which forms the cranial mesenteric vein.

Phylogeny and herbivory are related to avian cecal size

Avian ceca, a pair of blind sacs arising from the junction of the ileum and colon, are homologous to the cecum in mammals. Cecal size is hypothesized to depend on dietary proclivities and pressures, with faunivorous species having short ceca, whereas herbivorous species have long ceca. Previous tests of this hypothesis, however, did not account for phylogenetic pseudoreplication among closely related taxa. We collated published data on cecal length, dietary category, flying ability, and body mass from 155 avian taxa. Character states were mapped onto a phylogenetic framework, and the permutation tail probability test was used to detect phylogenetic signal in each character. Phylogenetic signal is significant among the characters. As with the cecoappendicular complex in mammals, closely-related birds tend to have similar cecal length. To account for phylogenetic pseudoreplication, we performed phylogenetic generalized least squares regression on cecal length and body mass with dietary category, superordinal-level clade, and flying ability as cofactors. The best-fitting regression model supports the dietary hypothesis for the avian cecum. Among sampled birds of comparable body mass, mean cecal length is significantly longer in herbivorous species than in carnivorous ones (p = 0.008), presumably allowing the extraction of nutrients without the burden of fermenting bulky masses of dietary fiber. Exceptions to this trend, however, suggest that avian ceca are functionally complex and may have additional roles in water balance and nitrogen recycling.

Beyond Fermentation: Other Important Services Provided to Endothermic Herbivores by their Gut Microbiota

For decades, comparative biologists have recognized the importance of microbial partners in facilitating herbivory as a successful feeding strategy. Most of this success is attributed to the ability of gut microbes to digest recalcitrant dietary fiber and provides usable nutrients to their hosts. Gut microbes can also provide numerous other functions, such as vitamin synthesis, nitrogen recycling, and the detoxification of plant secondary compounds. Here, we review these microbial functions in herbivorous mammals and birds, highlighting studies that utilize recently developed metagenomic techniques. Several of these studies emphasize that microbial services are the product of interactions and exchanges within a complex microbial community, rather than the product of an individual member. Additionally, a number of these microbial functions are interdependent. For example, levels of dietary nitrogen or plant toxins can influence fiber digestibility. Further studies into the variety of microbial services provided to herbivorous hosts, and how these services might interact will broaden our understanding of host-microbe interactions.

Helminth-bacteria interaction in the gut of domestic pigeon Columba livia domestica

The present paper is an attempt to study the interaction between the helminth parasite and bacteria residing in the gut of domestic pigeon, Columba livia domestica. Biochemical and molecular characterization of the gut bacterial isolate were done and the isolate was identified as Staphylococcus sp. DB1 (JX442510). The interaction of Staphylococcus sp. with Cotugnia cuneata, an intestinal helminth parasite of domestic pigeon was studied on the basis of the difference between 'mean worm burden' of antibiotic treated infected pigeons and infected pigeons without any antibiotic treatment. The ANOVA and Tukey tests of the data obtained showed that antibiotic treatment reduced the mean worm burden significantly. The biochemical properties of Staphylococcus sp. DB1 (JX442510) also showed a mutualistic relationship with the physiology of C. cuneata.

Characterization of cecal microbiota of the emu (Dromaius novaehollandiae)

Emus (Dromaius novaehollandiae), large flightless ratites native to Australia, are farmed for their fat and meat. They are omnivorous and feed on a wide variety of plants and insects. Despite having a relatively simple gastrointestinal tract and a short digesta retention time, emus are able to digest a significant portion of the ingested dietary neutral detergent fibre. However, nothing is known about the microbial diversity in their gastrointestinal tract. In this study, we evaluated the phylogenetic diversity of the cecal microbiota of four emus (2 males, 2 females) that were fed a barley-alfalfa-canola based diet, using 454 pyrosequencing after amplification for V3-V5 region of bacterial 16S rRNA gene. Emus were slaughtered in early November, just prior to the onset of their breeding season, but after the seasonal decline in their feed intake had begun. A total of 822 operational taxonomic units (OTUs) (335.3 ± 70.5 OTUs/sample) belonging to 9 bacterial phyla were identified. The most predominant bacterial phyla were Bacteroidetes (≈ 57% of total classified diversity), Proteobacteria (≈ 24%), Fusobacteria (≈ 11.3%), and Firmicutes (≈ 7%). Our results indicate that the emus' ceca may have a higher microbial richness (Chao1: 624 ± 170 OTUs, and ACE: 586 ± 161 OTUs) than other species of birds, but they have a lower microbial diversity (Shannon diversity index: 3.4 ± 0.2, Simpson index: 0.79 ± 0.02), possibly reflecting their decrease feed intake. This is the first study to characterize the microbial community of the gastrointestinal tract of a ratite using pyrosequencing, providing a baseline for further study.

Foregut fermentation in the hoatzin, a neotropical leaf-eating bird

The only known case of an avian digestive system with active foregut fermentation is reported for the hoatzin (Opisthocomus hoazin), one of the world's few obligate folivorous (leaf-eating) birds. Hoatzins are one of the smallest endotherms with this form of digestion. Foregut fermentation in a flying bird may be explained by increased digestive efficiency by selection of highly fermentable and extremely patchy resources, coupled with microbial nutritional products and secondary compound detoxification. This unexpected digestive system gives a new perspective to the understanding of size limitations of vertebrate herbivores and to the evolution of foregut fermentation.

Allometry of visceral organs in living amniotes and its implications for sauropod dinosaurs

Allometric equations are often used to extrapolate traits in animals for which only body mass estimates are known, such as dinosaurs. One important decision can be whether these equations should be based on mammal, bird or reptile data. To address whether this choice will have a relevant influence on reconstructions, we compared allometric equations for birds and mammals from the literature to those for reptiles derived from both published and hitherto unpublished data. Organs studied included the heart, kidneys, liver and gut, as well as gut contents. While the available data indicate that gut content mass does not differ between the clades, the organ masses for reptiles are generally lower than those for mammals and birds. In particular, gut tissue mass is significantly lower in reptiles. When applying the results in the reconstruction of a sauropod dinosaur, the estimated volume of the coelomic cavity greatly exceeds the estimated volume of the combined organ masses, irrespective of the allometric equation used. Therefore, substantial deviation of sauropod organ allometry from that of the extant vertebrates can be allowed conceptually. Extrapolations of retention times from estimated gut contents mass and food intake do not suggest digestive constraints on sauropod dinosaur body size.

Potential Impact of Nutritional Strategy on Noninvasive Measurements of Hormones in Birds

The dietary preferences, gastrointestinal anatomy, digestive physiology, biochemical capabilities, and commensal microflora of a bird are collectively known as its nutritional strategy. Measurement of hormones in droppings requires an appreciation of an animal's nutritional strategy in order to optimize collection protocols, validate techniques, interpret results, and minimize variability and artifacts. Foods of animal origin, nectar, and seeds are highly digestible by relatively simple digestive tracts and result in low rates of feces production. Most frugivorous species also have simple digestive tracts, and they digest the fruit's simple sugars and proteins, but not the fiber in its pulp. Consequently, retention time of food in the digestive tract is short, and their droppings are voluminous. Herbivorous species possess enlarged ceca that house microorganisms that aid in the digestion of fibrous components of their food. Part of the digesta enters the ceca and is subjected to lengthy microbial fermentation. The rest is excluded and quickly passes through the rectum, and is quickly defecated. For measurement of hormones in droppings it appears prudent to collect only rectal feces and to avoid cecal feces. One-third of the avian families are omnivorous and consume a wide variety of foods. Their digestive strategies are highly variable and change with diet, as does the amount and composition of feces and the rate of passage.

Symbiotic fermentation, digesta passage, and gastrointestinal morphology in bullfrog tadpoles (Rana catesbeiana)

Relative to other herbivorous vertebrates, the nutritional ecology and digestive physiology of anuran larvae remain poorly understood. Our objective was to compare gut structure and inhabitants, digesta passage, and microbial fermentation in bullfrog tadpoles (Rana catesbeiana) to those in other herbivores. Bullfrog tadpole gastrointestinal tracts were long and voluminous, with an enlarged colon that harbored a diverse symbiotic community. The transit time for particulate markers passing through bullfrog tadpoles was 6 h, the median retention time was 8-10 h, and gut clearance was 10-14 h postingestion. Relatively high levels of short-chain fatty acids in the hindgut of tadpoles indicated active microbial fermentation in this gut region. This report represents the first account of gastrointestinal fermentation in the class Amphibia. On the basis of in vitro fermentation assays, we estimated that microbial fermentation in the hindgut provides 20% of the total daily energy requirement of bullfrog tadpoles. These tadpoles also exhibited coprophagy, a practice that provides important nutritive gains in other herbivores. The physiological and behavioral characteristics of these tadpoles are remarkably similar to those of other small-bodied, hindgut-fermenting vertebrates, suggesting convergent digestive strategies among a broad range of herbivorous taxa.

Contributions of microbes in vertebrate gastrointestinal tract to production and conservation of nutrients

The vertebrate gastrointestinal tract is populated by bacteria and, in some species, protozoa and fungi that can convert dietary and endogenous substrates into absorbable nutrients. Because of a neutral pH and longer digesta retention time, the largest bacterial populations are found in the hindgut or large intestine of mammals, birds, reptiles, and adult amphibians and in the foregut of a few mammals and at least one species of bird. Bacteria ferment carbohydrates into short-chain fatty acids (SCFA), convert dietary and endogenous nitrogenous compounds into ammonia and microbial protein, and synthesize B vitamins. Absorption of SCFA provides energy for the gut epithelial cells and plays an important role in the absorption of Na and water. Ammonia absorption aids in the conservation of nitrogen and water. A larger gut capacity and longer digesta retention time provide herbivores with additional SCFA for maintenance energy and foregut-fermenting and copoprophagic hindgut-fermenting species with access to microbially synthesized protein and B vitamins. Protozoa and fungi also contribute nutrients to the host. This review discusses the contributions of gut microorganisms common to all vertebrates, the numerous digestive strategies that allow herbivores to maximize these contributions, and the effects of low-fiber diets and discontinuous feeding schedules on these microbial digestive processes.

Stomach stones for feeding or buoyancy? The occurrence and function of gastroliths in marine tetrapods

Gastroliths or ‘stomach stones’ occur frequently in some, but not all, groups of fossil and living m arine tetrapods. C om parative analysis of gastrolith distribution suggests a role in buoyancy control rather than food processing. Once accidental ingestion by bottom-feeding animals is excluded, gastroliths occur in most tetrapods which ‘fly’ underw ater with hydrofoil limbs, including plesiosaurs, penguins, and otariid pinnipeds, but not the m arine chelonians. They do not usually occur in cetaceans, ichthyosaurs, mosasaurs, and odobenid and phocid pinnipeds, which swim with a caudal fin or the equivalent. Occurrence in amphibious forms is variable; crocodilians often have gastroliths, but nothosaurs and placodonts do not. T he correlation of gastroliths and underw ater flight is corroborated by a com parative analysis which takes phylogenetic factors into account. There is no correlation with diet. Consideration of function and occurrence in terrestrial forms suggests that the use of gastroliths in digestion would not be useful, and might even be harmful, to a carnivorous m arine tetrapod. Gastroliths are more efficient than skeletal bone (as in pachyostosis) in terms of sinking force per unit of added mass or volume. As well as driftwood and ice, m arine tetrapods should be considered as a potential source of erratic stones in freshwater and marine sediments. Gastroliths may have evolved by the accidental ingestion of stones, the retention into adulthood of stones used by juveniles to process insect or plant food, or as a com pensatory replacem ent for dense bones habitually filling the stomach. Their presence or absence should be more carefully recorded and further studies should be carried out on their function.

Optimization of gut structure and diet for higher vertebrate herbivores

A generalized herbivore gut is modelled as (i) a well-stirred anterior chamber in which microbial fermentation occurs; (ii) a tubular reactor in which digestion but no fermentation occurs; and (iii) a posterior fermentation chamber. The rate at which the herbivore gains metabolizable energy is calculated for diets that can be eaten at different rates and contain different energy densities of easily digested cell contents, and of cell wall materials that can be fermented but not digested. The optimum gut structure for each diet is determined. Chewing probably speeds digestion and fermentation but reduces eating time. Optimal chewing times are determined for particular diets and guts. Herbivores often have a choice between poorer food that can be eaten fast and richer food that can only be eaten more slowly. Energy costs may be incurred in travelling between patches of the richer food. Optimal diet choices are predicted for herbivores with particular gut structures.

The effect of diet on microfaunal population and function in the caecum of a subterranean naked mole-rat, Heterocephalus glaber

The effect of dietary fibre and starch content on digestibility, microfaunal population and caecal function was investigated in a subterranean mole-rat, Heterocephalus glaber (Rodentia). Mole-rats were fed on a diet of either sweet potato (neutral-detergent fibre (NDF) 65 g/kg dry matter (DM), starch 638 g/kg DM) or carrot (NDF 157 g/kg DM, starch 258.7 g/kg DM) for 4 weeks. Daily intake and faecal output were monitored. Thereafter caecal microfaunal population, density and function were assessed using light and scanning electron microscopy and by measuring both gas and short chain fatty acid (SCFA) production. A 2.4-fold increase in fibre and 2.5-fold decrease in starch content resulted in a decrease in caecal DM content (390 g/kg). A concomitant dramatic decline (by 93%) in ciliate protozoa with a corresponding 2-fold increase in bacteria also accompanied this change in diet. Fermentative efficiency as indicated by gas production was 2.6 times greater on a carrot diet than on sweet potato. Microbial fermentation resulted in higher SCFA concentrations on the carrot diet, with a 42% reduction in SCFA concentration on the sweet potato diet. Here, SCFA contributed 5.1% of daily energy expenditure and this increased 5.0-fold on the carrot diet. Caecal micro-organism function, therefore, played an important role in the nutritional physiology of these naked mole-rats, and enabled maximum utilization of the food substrate.

Adaptations for avian frugivory: assimilation efficiency and gut transit time of Manacus vitellinus and Pipra mentalis

I examined the digestive physiology of two avian frugivores, the golden-collared manakin, Manacus vitellinus, and the red-capped manakin, Pipra mentalis, to discover how these birds extract energy from fruit. Using 14 species of fruit in the natural diet of manakins, I examined the assimilation of nutrients from fruit pulp, fruit passage rates, seed passage rates, and gut morphology. Fruits in the manakins' diets had high water content (average, 84%) and low nutrient concentrations (3 kJ/g wet pulp; 17 kJ/g dry pulp; 1% nitrogen/g dry pulp). Manacus and Pipra did not differ in the average assimilation of energy in fruit pulp (63%), although it varied from 37 to 84% depending on fruit species. Assimilation of total nonstructural carbohydrates in the fruit pulp was very high (86-98%) in both species. Gut evacuation was rapid; maximum transit time of a labeled fruit was 30 min. Seeds passed through the gut faster (Manacus: 15 min; Pipra: 12 min) than the accompanying fruit epidermis (both spp: 22 min). Manakins regurgitated large seeds (>5 mm diameter) in 7 to 9 min. Rapid gut passage time, high assimilation of nonstructural carbohydrates, and the selective regurgitation and rapid elimination of bulky seeds enable manakins to process a large volume of food per day. By increasing rates of fruit intake and gut passage, manakins can effectively increase total nutrient uptake. These adaptations of manakins are requisite for harvesting sufficient nutrients from fruit, due to its low nutrient density, high water content, and bulky seeds.

Absorption by the cecum of wild birds: is there interspecific variation

The major functions proposed for the avian cecum--energy balance and osmoregulation--involve absorption of material from the cecum, yet little is known of these absorptive processes in wild birds. The magnitude of transport of compounds from the ceca depends on the concentrations of compounds in the ceca, the presence of transport pathways for those compounds, and the size of the reabsorptive surface. Interspecific variation in size of avian ceca is well documented, but the other two determinants of absorption are much less well studied. All ceca examined contained acetic, propionic, and butyric acid; water content varies from less than 70 to greater than 90%. Most other constituents have been quantified in just one or two species. A model for cecal transport, derived from studies of mammalian ceca but consistent with observations on birds, is described. A luminal (mucosal) Na+/H+ exchanger couples the absorption of Na+ to that of volatile fatty acids, which are absorbed in their uncharged (protonated) form; these two compounds are thereby mutually stimulatory in their absorption. The cecum also absorbs water, sodium, carbon dioxide, and probably some nitrogenous compounds (e.g., ammonia). Too few data exist to analyze interspecific variation in cecal transport in birds. However, variations in the following characteristics do exist: cecal contents, cecal absorptive surface area, transport characteristics of other regions of avian intestine (e.g., rectum), cecal transport among mammalian species, and histology of avian ceca. Studies of the physiological consequences of these variation should yield insight into the function and contributions of the avian cecum.

Anatomy of the avian cecum

The gross anatomy of the avian ceca is reviewed. In most birds, right and left ceca arise laterally or ventrolaterally at the junction of the small and large intestines. In a few species, the ceca open into the rectum ventrally or dorsally. In many herons and bitterns, only one cecum is present, and in the secretary bird there are two pairs of ceca. Ceca are absent in woodpeckers, hummingbirds, swifts, kingfishers, pigeons, mousebirds, cuckoos, and parrots. Ceca may be classified according to length into long, moderately or poorly developed, and vestigial types. In most birds, the ceca are simple tubular structures with minor variations in shape. However, in a few species, including the ostrich, rheas, kiwis, some tinamous, the red-throated loon, screamers, the satyr tragopan, the great bustard, and the pin-tailed sandgrouse, the ceca are sacculated or have diverticula. There is usually no correlation between the development of the ceca and systematic position. Except in grouse (Tetraonidae), in which the long ceca are related to the fibre content of the diet, the correlation between cecal development and diet is extremely limited. There is no relationship between the size of the ceca and the length and width of the rectum.