Detection and Modulation of Olfactory Sensing Receptors in Carnivorous Rainbow Trout (Oncorhynchus mykiss) Fed from First Feeding with Plant-Based Diet.

Sense of smell is mediated by diverse families of olfactory sensing receptors, conveying important dietary information, fundamental for growth and survival. The aim of this study was to elucidate the role of the sensory olfactory pathways in the regulation of feeding behavior of carnivorous rainbow trout (RT, Oncorhynchus mykiss), from first feeding until 8 months. Compared to a commercial diet, RT fed with a total plant-based diet showed drastically altered growth performance associated with feed intake from an early stage. Exhaustive examination of an RT genome database identified three vomeronasal type 1 receptor-like (ORA), 10 vomeronasal type 2 receptor-like (OLFC) and 14 main olfactory receptor (MOR) genes, all highly expressed in sensory organs, indicating their potential functionality. Gene expression after feeding demonstrated the importance in olfactory sensing perception of some OLFC (olfcg6) and MOR (mor103, -107, -112, -113, -133) receptor family genes in RT. The gene ora1a showed evidence of involvement in olfactory sensing perception for fish fed with a commercial-like diet, while ora5b, mor118, mor124 and olfch1 showed evidence of involvement in fish fed with a plant-based diet. Results indicated an impact of a plant-based diet on the regulation of olfactory sensing pathways as well as influence on monoaminergic neurotransmission in brain areas related to olfactory-driven behaviors. The overall findings suggest that feeding behavior is mediated through olfactory sensing detection and olfactory-driven behavior pathways in RT.

No sustained increase in zooarchaeological evidence for carnivory after the appearance of Homo erectus.

The appearance of Homo erectus shortly after 2.0 Ma is widely considered a turning point in human dietary evolution, with increased consumption of animal tissues driving the evolution of larger brain and body size and a reorganization of the gut. An increase in the size and number of zooarchaeological assemblages after the appearance of H. erectus is often offered as a central piece of archaeological evidence for increased carnivory in this species, but this characterization has yet to be subject to detailed scrutiny. Any widespread dietary shift leading to the acquisition of key traits in H. erectus should be persistent in the zooarchaeological record through time and can only be convincingly demonstrated by a broad-scale analysis that transcends individual sites or localities. Here, we present a quantitative synthesis of the zooarchaeological record of eastern Africa from 2.6 to 1.2 Ma. We show that several proxies for the prevalence of hominin carnivory are all strongly related to how well the fossil record has been sampled, which constrains the zooarchaeological visibility of hominin carnivory. When correcting for sampling effort, there is no sustained increase in the amount of evidence for hominin carnivory between 2.6 and 1.2 Ma. Our observations undercut evolutionary narratives linking anatomical and behavioral traits to increased meat consumption in H. erectus, suggesting that other factors are likely responsible for the appearance of its human-like traits.

Reconstruction of evolutionary changes in fat and toxin consumption reveals associations with gene losses in mammals: A case study for the lipase inhibitor PNLIPRP1 and the xenobiotic receptor NR1I3.

The inactivation of ancestral protein-coding genes (gene loss) can be associated with phenotypic modifications. Within placental mammals, repeated losses of PNLIPRP1 (gene inhibiting fat digestion) occurred preferentially in strictly herbivorous species, whereas repeated NR1I3 losses (gene involved in detoxification) occurred preferentially in strictly carnivorous species. It was hypothesized that lower fat contents of herbivorous diets and lower toxin contents of carnivorous diets cause relaxed selection pressure on these genes, resulting in the accumulation of mutations and ultimately to convergent gene losses. However, because herbivorous and carnivorous diets differ vastly in their composition, a fine-grained analysis is required for hypothesis testing. We generated a trait matrix recording diet and semi-quantitative estimates of fat and toxin consumption for 52 placental species. By including data from 31 fossil taxa, we reconstructed the ancestral diets in major lineages (grundplan reconstruction). We found support that PNLIPRP1 loss is primarily associated with low levels of fat intake and not simply with herbivory/carnivory. In particular, PNLIPRP1 loss also occurred in carnivorous lineages feeding on a fat-poor diet, suggesting that the loss of this gene may be beneficial for occupying ecological niches characterized by fat-poor food resources. Similarly, we demonstrated that carnivorous species are indeed less exposed to diet-related toxins, suggesting that the loss of NR1I3 and related genes (NR1I2 and UGT1A6) resulted from relaxed selection pressure. This study illustrates the need of detailed phenotype studies to obtain a deeper understanding of factors underlying gene losses and to progress in understanding genomic causes of phenotypic variation in mammals.

Evolutionary and dietary relationships of wild mammals based on the gut microbiome.

Gut microbiome influence the health and evolution of mammals and multiple factors modulate the structure and function of gut microbiome. However, the specific changes of the diets and phylogeny on the gut microbiome were unclear. Here, we compared the gut microbiome of 16 rare wild mammals. All data (>200G 16S rRNA gene sequences) were generated using a high-throughput sequencing platform. Firmicutes and Bacteroidetes were the most predominant phyla in all mammals. However, Proteobacteria was an additionally dominant phylum specifically detected in the microbiome of carnivores and omnivores. Moreover, the dominant phyla in canids were Firmicutes, Bacteroidetes, Proteobacteria, and Fusobacteria. Phylogenetic reconstructions based on the gut microbiome and mitochondrial genome of these mammals were similar. The impact of the host on the microbiome community composition was most evident when considering conspecific and congeneric relationships. Similarity clustering showed that the gut microbiome of herbivores was clustered together, and the other clade comprised both omnivores and carnivores. Collectively, these results revealed that phylogenetic relationships and diet have an important impact on the gut microbiome, and thus the gut microbiome community composition may reflect both the phylogenetic relationships and diets. This study provides valuable basic data to facilitate future efforts related to animal conservation and health.

Early Pleistocene faunivorous hominins were not kleptoparasitic, and this impacted the evolution of human anatomy and socio-ecology.

Humans are unique in their diet, physiology and socio-reproductive behavior compared to other primates. They are also unique in the ubiquitous adaptation to all biomes and habitats. From an evolutionary perspective, these trends seem to have started about two million years ago, coinciding with the emergence of encephalization, the reduction of the dental apparatus, the adoption of a fully terrestrial lifestyle, resulting in the emergence of the modern anatomical bauplan, the focalization of certain activities in the landscape, the use of stone tools, and the exit from Africa. It is in this period that clear taphonomic evidence of a switch in diet with respect to Pliocene hominins occurred, with the adoption of carnivory. Until now, the degree of carnivorism in early humans remained controversial. A persistent hypothesis is that hominins acquired meat irregularly (potentially as fallback food) and opportunistically through klepto-foraging. Here, we test this hypothesis and show, in contrast, that the butchery practices of early Pleistocene hominins (unveiled through systematic study of the patterning and intensity of cut marks on their prey) could not have resulted from having frequent secondary access to carcasses. We provide evidence of hominin primary access to animal resources and emphasize the role that meat played in their diets, their ecology and their anatomical evolution, ultimately resulting in the ecologically unrestricted terrestrial adaptation of our species. This has major implications to the evolution of human physiology and potentially for the evolution of the human brain.

Serial disparity in the carnivoran backbone unveils a complex adaptive role in metameric evolution.

Organisms comprise multiple interacting parts, but few quantitative studies have analysed multi-element systems, limiting understanding of phenotypic evolution. We investigate how disparity of vertebral morphology varies along the axial column of mammalian carnivores - a chain of 27 subunits - and the extent to which morphological variation have been structured by evolutionary constraints and locomotory adaptation. We find that lumbars and posterior thoracics exhibit high individual disparity but low serial differentiation. They are pervasively recruited into locomotory functions and exhibit relaxed evolutionary constraint. More anterior vertebrae also show signals of locomotory adaptation, but nevertheless have low individual disparity and constrained patterns of evolution, characterised by low-dimensional shape changes. Our findings demonstrate the importance of the thoracolumbar region as an innovation enabling evolutionary versatility of mammalian locomotion. Moreover, they underscore the complexity of phenotypic macroevolution of multi-element systems and that the strength of ecomorphological signal does not have a predictable influence on macroevolutionary outcomes.

Molecular phyloecology suggests a trophic shift concurrent with the evolution of the first birds.

Birds are characterized by evolutionary specializations of both locomotion (e.g., flapping flight) and digestive system (toothless, crop, and gizzard), while the potential selection pressures responsible for these evolutionary specializations remain unclear. Here we used a recently developed molecular phyloecological method to reconstruct the diets of the ancestral archosaur and of the common ancestor of living birds (CALB). Our results suggest a trophic shift from carnivory to herbivory (fruit, seed, and/or nut eater) at the archosaur-to-bird transition. The evolutionary shift of the CALB to herbivory may have essentially made them become a low-level consumer and, consequently, subject to relatively high predation risk from potential predators such as gliding non-avian maniraptorans, from which birds descended. Under the relatively high predation pressure, ancestral birds with gliding capability may have then evolved not only flapping flight as a possible anti-predator strategy against gliding predatory non-avian maniraptorans but also the specialized digestive system as an evolutionary tradeoff of maximizing foraging efficiency and minimizing predation risk. Our results suggest that the powered flight and specialized digestive system of birds may have evolved as a result of their tropic shift-associated predation pressure.

Sight of parasitoid wasps accelerates sexual behavior and upregulates a micropeptide gene in Drosophila.

Parasitoid wasps inflict widespread death upon the insect world. Hundreds of thousands of parasitoid wasp species kill a vast range of insect species. Insects have evolved defensive responses to the threat of wasps, some cellular and some behavioral. Here we find an unexpected response of adult Drosophila to the presence of certain parasitoid wasps: accelerated mating behavior. Flies exposed to certain wasp species begin mating more quickly. The effect is mediated via changes in the behavior of the female fly and depends on visual perception. The sight of wasps induces the dramatic upregulation in the fly nervous system of a gene that encodes a 41-amino acid micropeptide. Mutational analysis reveals that the gene is essential to the behavioral response of the fly. Our work provides a foundation for further exploration of how the activation of visual circuits by the sight of a wasp alters both sexual behavior and gene expression.

Communication hubs of an asocial cat are the source of a human-carnivore conflict and key to its solution.

Human-wildlife conflicts occur worldwide. Although many nonlethal mitigation solutions are available, they rarely use the behavioral ecology of the conflict species to derive effective and long-lasting solutions. Here, we use a long-term study with 106 GPS-collared free-ranging cheetahs (Acinonyx jubatus) to demonstrate how new insights into the socio-spatial organization of this species provide the key for such a solution. GPS-collared territory holders marked and defended communication hubs (CHs) in the core area of their territories. The CHs/territories were distributed in a regular pattern across the landscape such that they were not contiguous with each other but separated by a surrounding matrix. They were kept in this way by successive territory holders, thus maintaining this overdispersed distribution. The CHs were also visited by nonterritorial cheetah males and females for information exchange, thus forming hotspots of cheetah activity and presence. We hypothesized that the CHs pose an increased predation risk to young calves for cattle farmers in Namibia. In an experimental approach, farmers shifted cattle herds away from the CHs during the calving season. This drastically reduced their calf losses by cheetahs because cheetahs did not follow the herds but instead preyed on naturally occurring local wildlife prey in the CHs. This implies that in the cheetah system, there are "problem areas," the CHs, rather than "problem individuals." The incorporation of the behavioral ecology of conflict species opens promising areas to search for solutions in other conflict species with nonhomogenous space use.

Phenotypic integration in feliform carnivores: Covariation patterns and disparity in hypercarnivores versus generalists.

The skeleton is a complex arrangement of anatomical structures that covary to various degrees depending on both intrinsic and extrinsic factors. Among the Feliformia, many species are characterized by predator lifestyles providing a unique opportunity to investigate the impact of highly specialized hypercarnivorous diet on phenotypic integration and shape diversity. To do so, we compared the shape of the skull, mandible, humerus, and femur of species in relation to their feeding strategies (hypercarnivorous vs. generalist species) and prey preference (predators of small vs. large prey) using three-dimensional geometric morphometric techniques. Our results highlight different degrees of morphological integration in the Feliformia depending on the functional implication of the anatomical structure, with an overall higher covariation of structures in hypercarnivorous species. The skull and the forelimb are not integrated in generalist species, whereas they are integrated in hypercarnivores. These results can potentially be explained by the different feeding strategies of these species. Contrary to our expectations, hypercarnivores display a higher disparity for the skull than generalist species. This is probably due to the fact that a specialization toward high-meat diet could be achieved through various phenotypes. Finally, humeri and femora display shape variations depending on relative prey size preference. Large species feeding on large prey tend to have robust long bones due to higher biomechanical constraints.

Can a carnivore diet provide all essential nutrients?

PURPOSE OF REVIEW: The aim of this study was to summarize current contributions affecting knowledge and predictions about the nutritional adequacy of plant-free diets, contextualized by historical accounts. RECENT FINDINGS: As demonstrated in recent experiments, nutrient interactions and metabolic effects of ketogenic diets can impact nutritional needs, sometimes resulting in nutrient-sparing effects. Other studies highlight conflicting hypotheses about the expected effect on metabolic acidosis, and therefore mineral status, of adding alkaline mineral-rich vegetables. SUMMARY: A carnivore diet is a newly popular, but as yet sparsely studied form of ketogenic diet in which plant foods are eliminated such that all, or almost all, nutrition derives from animal sourced foods. Ketogenic diets are already nutritionally controversial due to their near-complete absence of carbohydrate and high dietary fat content, but most ketogenic diet advocates emphasize the inclusion of plant foods. In this review, we discuss the implications of relying solely on animal sourced foods in terms of essential nutrient status.

Evolution of digestive enzyme genes associated with dietary diversity of crabs.

Crabs feed on a wide range of items and display diverse feeding strategies. The primary objective of this study was to investigate 10 digestive enzyme genes in representative crabs to provide insights into the genetic basis of feeding habits among crab functional groups. Crabs were classified into three groups based on their feeding habits: herbivores (HV), omnivores (OV), and carnivores (CV). To test whether crabs' feeding adaptations matched adaptive evolution of digestive enzyme genes, we examined the 10 digestive enzyme genes of 12 crab species based on hepatopancreas transcriptome data. Each of the digestive enzyme genes was compared to orthologous sequences using both nucleotide- (i.e., PAML and Datamonkey) and protein-level (i.e., TreeSAAP) approaches. Positive selection genes were detected in HV crabs (AMYA, APN, and MGAM) and CV crabs (APN, CPB, PNLIP, RISC, TRY, and XPD). Additionally, a series of positive selection sites were localized in important functional regions of these digestive enzyme genes. This is the first study to characterize the molecular basis of crabs' digestive enzyme genes based on functional feeding group. Our data suggest that HV crabs have evolved an enhanced digestion capacity for carbohydrates, and CV crabs have acquired digestion capacity for proteins and lipids.

Solitary meat-eaters: solitary, carnivorous carnivorans exhibit the highest degree of sexual size dimorphism.

Although sexual size dimorphism (SSD) is widespread across the animal tree of life, the underlying evolutionary processes that influence this phenomenon remains elusive and difficult to tease apart. In this study, I examined how social system (as a proxy for sexual selection) and diet (as a proxy for natural selection) influenced the evolution of SSD in terrestrial carnivorans (Carnivora; Mammalia). Using phylogenetic comparative methods, I found that are territorial solitary and carnivorous carnivorans exhibited selection towards increased degree of male-biased SSD compared to other carnivorans with alternative social systems and diets. I also found the absence of Rensch's rule across most carnivoran clades, suggestion a relaxation of the influences of sexual selection on SSD. These results together suggest that sexual selection and niche divergence together are important processes influencing the evolution of male-biased SSD in extant terrestrial carnivorans.

Shaping of a three-dimensional carnivorous trap through modulation of a planar growth mechanism.

Leaves display a remarkable range of forms, from flat sheets with simple outlines to cup-shaped traps. Although much progress has been made in understanding the mechanisms of planar leaf development, it is unclear whether similar or distinctive mechanisms underlie shape transformations during development of more complex curved forms. Here, we use 3D imaging and cellular and clonal analysis, combined with computational modelling, to analyse the development of cup-shaped traps of the carnivorous plant Utricularia gibba. We show that the transformation from a near-spherical form at early developmental stages to an oblate spheroid with a straightened ventral midline in the mature form can be accounted for by spatial variations in rates and orientations of growth. Different hypotheses regarding spatiotemporal control predict distinct patterns of cell shape and size, which were tested experimentally by quantifying cellular and clonal anisotropy. We propose that orientations of growth are specified by a proximodistal polarity field, similar to that hypothesised to account for Arabidopsis leaf development, except that in Utricularia, the field propagates through a highly curved tissue sheet. Independent evidence for the polarity field is provided by the orientation of glandular hairs on the inner surface of the trap. Taken together, our results show that morphogenesis of complex 3D leaf shapes can be accounted for by similar mechanisms to those for planar leaves, suggesting that simple modulations of a common growth framework underlie the shaping of a diverse range of morphologies.

Does faecal matter reflect location? An initial assessment of isotopic variability between consumed prey remains and faecal matter for wild jaguars.

Faecal isotopic analysis may complement other non-invasive wildlife survey tools for monitoring landscape use by carnivores, such as motion-detecting cameras and non-invasive genetic sampling. We analysed carbon, nitrogen, and strontium isotopes in faecal matter produced by jaguars (Panthera onca) as well as bones from consumed prey at the Mountain Pine Ridge Forest Reserve (MPR) in Belize, Central America. The MPR is ideally suited for a spatial isotope study as vegetation and geology both vary considerably. The isotopic composition of faecal matter should reflect the habitat and geology where consumed prey lived. We used bone from consumed prey recovered from jaguar scats as a proxy for diet. Faecal matter and bone showed comparable spatial isotopic trends, suggesting that the isotopic composition of jaguar faeces can be used to detect foraging in different habitats (pine forest versus broadleaf forest) or on different geologies (Mesozoic carbonates; Palaeozoic granite, contact metamorphics, and metasediments). This result is reassuring as bones are not always present in carnivore scats. Studying landscape use by cryptic and wide-ranging carnivore species like jaguars remains challenging. Isotopic analysis of faecal matter complements the existing array of non-invasive spatial monitoring tools.

Functional diversification of teleost Fads2 fatty acyl desaturases occurs independently of the trophic level.

The long-chain (≥C20) polyunsaturated fatty acid biosynthesis capacity of fish varies among species, with trophic level hypothesised as a major factor. The biosynthesis capacity is largely dependent upon the presence of functionally diversified fatty acyl desaturase 2 (Fads2) enzymes, since many teleosts have lost the gene encoding a Δ5 desaturase (Fads1). The present study aimed to characterise Fads2 from four teleosts occupying different trophic levels, namely Sarpa salpa, Chelon labrosus, Pegusa lascaris and Atherina presbyter, which were selected based on available data on functions of Fads2 from closely related species. Therefore, we had insight into the variability of Fads2 within the same phylogenetic group. Our results showed that Fads2 from S. salpa and C. labrosus were both Δ6 desaturases with further Δ8 activity while P. lascaris and A. presbyter Fads2 showed Δ4 activity. Fads2 activities of herbivorous S. salpa are consistent with those reported for carnivorous Sparidae species. The results suggested that trophic level might not directly drive diversification of teleost Fads2 as initially hypothesised, and other factors such as the species' phylogeny appeared to be more influential. In agreement, Fads2 activities from P. lascaris and A. presbyter were similar to their corresponding phylogenetic counterparts Solea senegalensis and Chirostoma estor.

Debris ingestion by carnivorous consumers: Does the position in the water column truly matter?

The hypothesis that carnivorous consumers associated with the seabed are more likely to ingest marine debris was tested based on stomach content analysis of fish (Trichiurus lepturus and species of Ariidae) and cetaceans (Sotalia guianensis and Pontoporia blainvillei). Among 596 stomach contents, only 22 (3.7%) contained debris. The debris was flexible plastic, nylon yard, paper, latex, styrofoam and cigarette filter. The proportion of stomach contents with debris varied among species: P. blainvillei (pelagic demersal consumer) presented the highest frequency of ingestion (15.7%), while T. lepturus (pelagic consumer), S. guianensis (pelagic consumer) and Ariidae (demersal consumer) presented similar frequencies (1.3-1.8%). Therefore, a feeding site in the water column does not predict the probability of debris ingestion. Concerning these species, this probability seems to be more associated with prey-capture strategies (or feeding behavior), regardless of debris availability in the environment.

Defense of pyrethrum flowers: repelling herbivores and recruiting carnivores by producing aphid alarm pheromone.

(E)-ß-Farnesene (EßF) is the predominant constituent of the alarm pheromone of most aphid pest species. Moreover, natural enemies of aphids use EßF to locate their aphid prey. Some plant species emit EßF, potentially as a defense against aphids, but field demonstrations are lacking. Here, we present field and laboratory studies of flower defense showing that ladybird beetles are predominantly attracted to young stage-2 pyrethrum flowers that emitted the highest and purest levels of EßF. By contrast, aphids were repelled by EßF emitted by S2 pyrethrum flowers. Although peach aphids can adapt to pyrethrum plants in the laboratory, aphids were not recorded in the field. Pyrethrum's (E)-ß-farnesene synthase (EbFS) gene is strongly expressed in inner cortex tissue surrounding the vascular system of the aphid-preferred flower receptacle and peduncle, leading to elongated cells filled with EßF. Aphids that probe these tissues during settlement encounter and ingest plant EßF, as evidenced by the release in honeydew. These EßF concentrations in honeydew induce aphid alarm responses, suggesting an extra layer of this defense. Collectively, our data elucidate a defensive mimicry in pyrethrum flowers: the developmentally regulated and tissue-specific EßF accumulation and emission both prevents attack by aphids and recruits aphid predators as bodyguards.

Artificial reefs facilitate tropical fish at their range edge.

Spatial planning increasingly incorporates theoretical predictions that artificial habitats assist species movement at or beyond range edges, yet evidence for this is uncommon. We conducted surveys of highly mobile fauna (fishes) on artificial habitats (reefs) on the southeastern USA continental shelf to test whether, in comparison to natural reefs, artificial reefs enhance local abundance and biomass of fishes at their poleward range margins. Here, we show that while temperate fishes were more abundant on natural reefs, tropical, and subtropical fishes exhibited higher abundances and biomasses on deep (25-35 m) artificial reefs. Further analyses reveal that this effect depended on feeding guilds because planktivorous and piscivorous but not herbivorous fishes were more abundant on artificial reefs. This is potentially due to heightened prey availability on and structural complexity of artificial reefs. Our findings demonstrate that artificial habitats can facilitate highly mobile species at range edges and suggest these habitats assist poleward species movement.

Selection of carbohydrate-active probiotics from the gut of carnivorous fish fed plant-based diets.

The gastrointestinal microbiota plays a critical role on host health and metabolism. This is particularly important in teleost nutrition, because fish do not possess some of the necessary enzymes to cope with the dietary challenges of aquaculture production. A main difficulty within fish nutrition is its dependence on fish meal, an unsustainable commodity and a source of organic pollutants. The most obvious sustainable alternatives to fish meal are plant feedstuffs, but their nutritive value is limited by the presence of high levels of non-starch polysaccharides (NSP), which are not metabolized by fish. The composition of fish-gut microbial communities have been demonstrated to adapt when the host is fed different ingredients. Thus, we hypothesized that a selective pressure of plant-based diets on fish gut microbiota, could be a beneficial strategy for an enrichment of bacteria with a secretome able to mobilize dietary NSP. By targeting bacterial sporulating isolates with diverse carbohydrase activities from the gut of European sea bass, we have obtained isolates with high probiotic potential. By inferring the adaptive fitness to the fish gut and the amenability to industrial processing, we identified the best two candidates to become industrially valuable probiotics. This potential was confirmed in vivo, since one of the select isolates lead to a better growth and feed utilization efficiency in fish fed probiotic-supplemented plant-based diets, thus contributing for sustainable and more cost-effective aquaculture practices.