Dietary–morphological relationships in a fish assemblage of the Bolivian Amazonian floodplain

Morphological correlates of diet were examined in 48 species of freshwater fishes from floodplain lakes in the central part of the Mamoré River (Bolivian Amazon). The species were classified, according to the percentage occurrence of seven food items, into eight broad trophic categories: mud feeders, algivores, herbivores, terrestrial invertivores and omnivores, carnivores, zooplanktivores, aquatic invertivores and piscivores. There were significant relationships between the diet and morphology of the fishes even when the effect of taxonomical relatedness between species was eliminated. Relative gut length was the main morphological variable used to order species on a carnivore to mud feeder gradient. Standard length and head and mouth size were the morphological variables most closely associated with prey size. Mud feeder, algivore and piscivore species appeared as the most dietary and morphologically specialized. These results support both the hypotheses that species morphology influences the diet and that morphological similarity is conserved even in comparison with taxonomically unrelated species.     

Ecological diversification associated with the benthic‐to‐pelagic transition by North American minnows

Ecological opportunity is often regarded as a key factor that explains why diversity is unevenly distributed across life. Colonization of novel environments or adaptive zones may promote diversification. North American minnows exhibit an ancestral benthic‐to‐pelagic habitat shift that coincided with a burst in diversification. Here, we evaluate the phenotypic and ecological implications of this habitat shift by assessing craniofacial and dietary traits among 34 species and testing for morphology–diet covariation, convergence and adaptive optima. There were several instances of morphology–diet covariation such as correlations between mouth angle and the consumption of terrestrial insects and between relative gut length and the consumption of algae. After accounting for size and phylogenetic nonindependence, benthic species had longer heads, longer snouts, eyes positioned higher on their head, smaller mouth angles and longer digestive tracts than pelagic minnows. Benthic minnows also consumed more algae but less terrestrial insects, by volume, than pelagic minnows. Lastly, there were three distinct evolutionary regimes and more convergence in morphology and dietary characteristics than expected under a Brownian motion model of evolution. These findings indicate that colonization of the pelagic zone by minnows involved myriad phenotypic and dietary changes associated with exploitation of terrestrial subsidies. Thus, minnows exhibit phenotype–dietary covariation, an expansion of ecological roles and a burst in diversification rates in response to the ecological opportunity afforded by the colonization of a novel habitat.     

Ontogenetic changes in morphology and diet in the snakehead, <Emphasis Type="Italic">Channa limbata</Emphasis>, a predatory fish in western Thailand

Synopsis We examined the diet of Channa limbata, a predatory fish from western Thailand, in relation to mass, mouth and body morphology and intestine length. The cluster analysis we performed on the prey-specific abundance values of the dietary items yielded four size-classes based on diet. There was a shift from detritus and smaller benthic invertebrates in the diet of the first size class, to a mainly piscivorous diet in the fourth size-class as well as a steep increase in mass at the onset of piscivory. We found no significant change in relative intestine length with ontogeny, and the average relative intestine length value for C. limbata indicated primarily carnivorous feeding habits throughout ontogeny. Ontogenetic changes in mouth dimensions account primarily for the shift in diet, however the ontogenetic change in body morphology is of secondary importance.     

Morphology–diet relationships in four killifishes (Teleostei, Cyprinodontidae, Orestias) from Lake Titicaca

This study explores the relationship between morphology and diet in four Andean killifishes ( Orestias ) from Lake Titicaca that are known to differ in habitat use. Species that fed preferentially on amphipods ( Orestias albus ) or molluscs ( Orestias luteus ) separated in multivariate space from other species that feed on cladocera and algae ( Orestias agassii and Orestias jussiei ). Generally, specimens feeding on cladocera were characterized by a short, blunt nose with a small mouth; whereas, specimens feeding on amphipods exhibited a long snout with a large mouth. Specimens including molluscs in their diet tended to have a larger posterior part of the head and the larger opercles than others; while the occurrence of substratum in gut content was generally related to a short but deep head. The present analysis suggests that the littoral O. jussiei has an intermediate phenotype and diet between the pelagic ( O. agassii ) and benthic ( O. albus and O. luteus ) species. Results suggest that resource partitioning was occurring and that several morphological traits relate to characteristics of the diet, and it is inferred that the benthic, the pelagic and the littoral zones in the lake host different prey communities constituting distinct adaptive landscapes.     

Dietary-morphological relationships of fishes in Liangzi Lake, China

Species in Liangzi Lake were clustered into four trophic groups: Hemiramphus kurumeus and Hemiculter bleekeri bleekeri fed predominantly on terrestrial insects; Carassius auratus auratus and Abbottina rivularis on non-animal food; Hypseleotris swinhonis, Ctenogobius giurinus, Pseudorasbora parva and Toxabramis swinhonis on cladocerans or copepods; Culterichthys erythropterus on decapod shrimps. Gut length, mouth width, mouth height, gill raker length and gill raker spacing, varied widely among species. With the exception of three species pairs ( H. swinhonis, C. giurinus; C. erythropterus, H. kurumeus; T. swinhonis, H. bleekeri bleekeri ), principal components analysis of morphological variables revealed over-dispersion of species. Canonical correspondence analysis of dietary and morphological data revealed five significant dietary-morphological correlations. The first three roots explained > 85% of the total variance. The first root reflected mainly the relationship of gut length to non-animal food, with an increase in gut length associated with an increase in non-animal food. The second root was influenced strongly by the relationship of the gill raker spacing to consumption of copepods, with an increase in gill raker spacing associated positively with copepods in the diet. The third root was influenced by the relationship of mouth gape to consumption of fish and decapod shrimps, with an increase in mouth gape associated with more fish and decapod shrimps in the diet. These significant dietary-morphological relationships supported the eco-morphological hypotheses that fish morphology influence food use, and morphological variation is important in determining ecological segregation of co-existing fish species.     

Morphology and diet are decoupled in nearshore notothenoids from King George Island,West Antarctica

Antarctic notothenioid fishes show wide adaptive morphological radiation, linked to habitat preferences and food composition. However, direct comparisons of phenotypic variability and feeding habits are still lacking, particularly in stages inhabiting nearshore areas. To assess these relationships, we collected juveniles and adults of the most common benthic species inhabiting shallow waters off the South Shetland Islands within a similar size range, the plunderfish Harpagifer antarcticus, the black rockcod Notothenia coriiceps, and the marbled rockcod Notothenia rossii. Individual size ranges varied from 44.0 to 98.9 mm standard length (LS) (H. antarcticus), from 95.8 to 109.3 mm LS (N. coriiceps), and from 63.0 to 113.0 mm LS (N. rossii). Notothenioid fish showed different morphospace variability, being larger for H. antarcticus than the other Notothenia species and associated with the position of the posterior end of the operculum, along with the location and relative size of the eye. The evolutionary allometry was low, but the static allometry was much higher, especially for H. antarcticus and N. rossii. The diet was mainly carnivorous, consisting of amphipods and euphausiids. Macroalgae were scarce or totally absent in the gut contents of all species. Only H. antarcticus showed an increase in the prey number and ingested prey volume with fish size. Finally, there was a significant covariation between shape changes and LS in all species (allometric effects), however, not with prey composition, probably due to the small size range or ontogenetic stage and the relative similarity (or lack of contrast) in the benthic environment that they utilized.     

Diet-morphology correlations in the radiation of South American geophagine cichlids (Perciformes: Cichlidae: Cichlinae)

Genera within the South American cichlid tribe Geophagini display specialized feeding and reproductive strategies, with some taxa specialized for both substrate-sifting and mouth brooding. Several lineages within the clade also possess an epibranchial lobe (EBL), a unique pharyngeal structure that has been proposed to have a function in feeding and/or mouth brooding. A recently published genus-level phylogeny of Neotropical cichlids was used as the evolutionary framework for investigating the evolution of morphological features presumably correlated with diet and mouth brooding in the tribe Geophagini. We tested for possible associations between the geophagine epibranchial lobe and benthic feeding and mouth brooding. We also addressed whether the EBL may be associated with unique patterns of diversification in certain geophagine clades. Tests of binary character correlations revealed the EBL was significantly associated with mouth brooding. We also tested for a relationship between diet and morphology. We analyzed stomach contents and morphometric variation among 21 species, with data for two additional species obtained from the literature. Principal Components Analysis revealed axes of morphological variation significantly correlated with piscivory and benthivory, and both morphology and diet were significantly associated with phylogeny. These results suggest that the EBL could be an adaptation for either feeding or mouth brooding. The EBL, however, was not associated with species richness or accelerated rates of phyletic diversification.     

Restoration of the superficial facial musculature in nimravids

The size, shape and position of the mouth and sensory features such as the nose, eyes and ears in the nimravid barbourofelins are reconstructed. The earliest barbourofelin studied, Sansanosmilus , is the most similar to both pantherine and nonpantherine felids in sensory structure morphology. Through time, the species of the barbourofelin lineage diverge from felids with regard to facial features. Evolutionary trends include expansion of the nasal region, a more lateral orientation of the eyes and lowered position for the ears. Increased width and shortening of the muzzle accommodates the large oral opening required by the large gape of Barboumfelis , culminating in B. fricki with eyes oriented laterally enough to reduce stereoscopic vision. The ear position in this species is also significantly lower than in the earlier barbourofelins or felids. This may reflect an anatomic compromise between sensory structure position and changes in relative size, shape and position of other skull features. These changes correlate with increased canine tooth length and increased gape, exemplified by Barboumfelis fricki. Cranial soft tissue structures are restored through scars of attachment on the fossil bones, and the proportions of these features to one another determined. New observations provide criteria for reconstructing soft tissue anatomy in extinct animals.     

Evolutionary divergence of enterobacterial genes coding for the glucose phosphotransferase system components

Abstract The DNA relatedness of 64 enterobacterial species to Escherichia coli genes pts I, pts H, crr , pts G, and pts LPM, was determined by quantitative filter hybridization. DNA relatedness was expressed relative to E. coli K-12 DNA. Enterobacterial DNAs were 0 to 100% related to E. coli genes and the level of relatedness (except for crr data) reflected the known taxonomic (phylogenetic) position of species with respect to E. coli . When pts I relatedness data were plotted against pts H data, correlation was excellent. In pts G versus pts LPM plots, the data points (species) were scattered along the diagonal with a large gap separating E. coli strains (80–100% relatedness to both probes) from the 63 other species (1 to 40% relatedness to E. coli genes). Serratia (9 species), Buttiauxella agrestis , and Klebsiella planticola gave higher relatedness values with crr probe than with the other probes tested.     

Early sexual dimorphism in the developing gut microbiome of northern elephant seals

The gut microbiome is an integral part of a species' ecology, but we know little about how host characteristics impact its development in wild populations. Here, we explored the role of such intrinsic factors in shaping the gut microbiome of northern elephant seals (Mirounga angustirostris) during a critical developmental window of 6 weeks after weaning, when the pups stay ashore without feeding. We found substantial sex differences in the early‐life gut microbiome, even though males and females could not yet be distinguished morphologically. Sex and age both explained around 15% of the variation in gut microbial beta diversity, while microbial communities sampled from the same individual showed high levels of similarity across time, explaining another 40% of the variation. Only a small proportion of the variation in beta diversity was explained by health status, assessed by full blood counts, but clinically healthy individuals had a greater microbial alpha diversity than their clinically abnormal peers. Across the post‐weaning period, the northern elephant seal gut microbiome was highly dynamic. We found evidence for several colonization and extinction events as well as a decline in Bacteroides and an increase in Prevotella, a pattern that has previously been associated with the transition from nursing to solid food. Lastly, we show that genetic relatedness was correlated with gut microbiome similarity in males but not females, again reflecting early sex differences. Our study represents a naturally diet‐controlled and longitudinal investigation of how intrinsic factors shape the early gut microbiome in a species with extreme sex differences in morphology and life history.     

Variability and convergence in benthic communities along the longitudinal gradients of four physically similar Rocky Mountain streams

1. High‐gradient mountain streams are ideal for studying longitudinal biological patterns, although the degree of similarity in the biological gradient among physically similar streams in a region is poorly known. Our first objective was to evaluate variability in benthic communities along four streams in the central Rocky Mountains of Colorado. We analysed the relative influence of longitudinal position versus reach‐scale physical variables on community structure and measured community similarity at comparable longitudinal positions on the four streams. 2. Our second objective was to evaluate the relative utility of taxonomically versus functionally defined communities to characterise assemblage structure: are taxonomic patterns more predictable along the gradient than are patterns of ecologically important species traits? 3. Redundancy analyses (RDA), including measures of both reach‐scale environmental variables (substratum properties, periphytic cover, local channel slope) and longitudinal position (altitude, stream size), confirmed that the longitudinal position of a site was most important in determining taxonomic composition. Functional community structure was also influenced by longitudinal position, but reach‐scale variables (especially periphyton and median particle size) were of greater importance. 4. Redundancy analyses explained 29.3% of total taxonomic variance and 26.0% of functional variance, indicating that defining assemblages functionally provides no greater understanding of community patterns given several known environmental variables. Strict longitudinal limits of taxa, the presumably identical regional species pool across our sites, and/or trade‐offs among different types of species traits probably explain this result. 5. Redundancy analyses did suggest, however, that traits related to longer life (semivoltinism, long‐lived adults, and slow larval development) were more common downstream, while long‐distance dispersal ability and high fecundity were associated with higher altitude and its associated harsher conditions. 6. When sampling sites were grouped into three ecological zones defined by altitude, mean community similarity (measured both taxonomically and functionally) was lowest across streams at the highest altitude. This pattern could be driven by increased insularity of alpine‐zone streams, resulting from a combination of harsh terrestrial environment, lack of hydrological connectivity, and limited species ranges along the longitudinal continuum.     

Diets of syntopic finescale dace,Phoxinus neogaeus,and northern redbelly dace,Phoxinus eos: a reflection of trophic morphology

Synopsis We examined relative abundance, distribution, and gut contents of Phoxinus eos and P. neogaeus in a small northern Michigan bog lake. P. eos were usually 5–100 x more abundant than P. neogaeus, but both species were more abundant near the lake margin than offshore. Both species fed primarily on algae and invertebrates associated with the bog mat, but differences in diet were associated with differences in trophic morphology. As expected, because of its relatively longer intestine and smaller mouth, P. eos consumed relatively more plant matter, especially green algae, and fewer macroinvertebrates than P. neogaeus. These dietary conclusions were supported by analysis of two independent data sets. Further work is needed to discriminate between the effects of body size and trophic morphology on diet.     

Application of Methods for Identifying Broiler Chicken Gut Bacterial Species Linked with Increased Energy Metabolism

A high-throughput microbial profiling tool based on terminal restriction fragment length polymorphism was developed to monitor the poultry gut microbiota in response to dietary manipulations. Gut microbial communities from the duodena, jejuna, ilea, and ceca of 48 birds fed either a barley control diet or barley diet supplemented with exogenous enzymes for degrading nonstarch polysaccharide were characterized by using multivariate statistical methods. Analysis of samples showed that gut microbial communities varied significantly among gut sections, except between the duodenum and jejunum. Significant diet-associated differences in gut microbial communities were detected within the ileum and cecum only. The dissimilarity in bacterial community composition between diets was 73 and 66% within the ileum and cecum, respectively. Operational taxonomic units, representing bacterial species or taxonomically related groups, contributing to diet-associated differences were identified. Several bacterial species contributed to differences between diet-related gut microbial community composition, with no individual bacterial species contributing more than 1 to 5% of the total. Using canonical analysis of principal coordinates biplots, we correlated differences in gut microbial community composition within the ileum and cecum to improved performance, as measured by apparent metabolizable energy. This is the first report that directly links differences in the composition of the gut microbial community with improved performance, which implies that the presence of specific beneficial and/or absence of specific detrimental bacterial species may contribute to the improved performance in these birds.     

Diet of the small-spotted catshark Scyliorhinus canicula in the Aegean Sea (eastern Mediterranean)

The diet of the small-spotted catshark Scyliorhinus canicula, captured in the Aegean Sea by bottom-trawl from 2006 to 2012, was investigated with respect to sex, maturity condition, sampling location and season. The stomach contents of 432 specimens, measuring from 144 to 517?mm in total length, were analysed. The cumulative prey curve showed that the sample size was adequate to describe the species’ diet, which was quantified using the percentage gravimetric composition (%W). The identified prey items belonged to eight major groups: Teleostei, Chondrichthyes, Crustacea, Cephalopoda, Annelida, Echinodermata, phanerogams and macroalgae, with Teleostei, Crustacea and Cephalopoda being the most consumed in both females (%W?=?48.1, 16.0 and 31.4, respectively) and males (%W?=?33.9, 31.6 and 29.8, respectively). Higher diet diversity was observed in males than females, in immature individuals than mature ones, regardless of sex, as well as in spring in comparison to autumn and winter. Feeding intensity seemed to be influenced mainly by sex and maturity condition. No significant dietary overlap was observed for all possible combinations of the factors examined. Gut indices were compared between the two sexes with females showing statistically significantly higher median relative gut length, as well as a longer gut than males of the same length. Based on the diet composition, S. canicula can be considered a generalist predator consuming, with geographical differentiation, a wide variety of benthic taxa. The estimated fractional trophic level (τ?=?4.22) classified the species as a carnivore with a preference for Teleostei and Cephalopoda, thus confirming its key role in the food web.     

Optical parameters of the eyes of some benthic decapods as a function of habitat depth (Crustacea,Decapoda)

Summary Eye diameter relative to body length, and interommatidial angle, rhabdom length and rhabdom width as a function of eye size, were determined for specimens of 19 benthic macruran decapod species in 8 genera and 5 families, spanning a wide range of habitat depths. For these species, eye diameter relative to body length tends to increase with adult habitat. In addition, rate of eye growth relative to body growth increases with habitat depth, a trend opposite to that of pelagic crustaceans previously investigated. Interommatidial angle decreases with increasing eye diameter, and therefore with depth for an individual of a particular size. Rhabdom length and width tend to increase with eye diameter. Visual sensitivity may increase with depth among these species as a result of both larger eyes and the associated increase in rhabdom dimensions. Differences in energetic limitations and visual environments might produce the difference in trends of eye size relative to body size between benthic and pelagic crustaceans.     

Microcrustacean prey and macroinvertebrate predators in a stream food web

1. The consumption of microcrustacea by two polyphagous predators, larvae of the caddisfly Plectrocnemia conspersa (Curtis) and the alderfly Sialis fuliginosa Pictet, was investigated in an English stream with a well-known macro- and microinvertebrate fauna. Benthic samples were collected in August, November, December and April, and the gut contents of all individuals of both predators were examined. 2. All the microcrustacean groups (Cyclopoida, Harpacticoida, Chydoridae and Ostracoda) were identified in gut contents. Of the ten taxa present in the benthos, all occurred in the diet of P. conspersa; nine were found in S. fuliginosa. 3. Ontogenetic shifts in the diets of both predators were found, and microcrustacea were consumed more frequently by small than large instars. 4. There was little evidence of selective feeding by P. conspersa, whereas ostracods were over-represented in the diet of S. fuliginosa, compared with benthic relative densities. The Chydoridae were under-represented in the diet of both predators. 5. The food web of Broadstone Stream is perhaps the most detailed web available for any running water habitat. Increased taxonomic resolution produced marked changes in values of connectance and predator-prey ratios. Linkage density remained fairly constant at different levels of resolution and were high, indicative of a web of generalist species. Omnivory was pronounced and may be characteristic of donor-controlled systems where organic detritus is the primary energy base.     

On the measurement of species diversity incorporating species differences

When pairwise differences (relatedness) between species are numerically given, the average of the species differences weighted by relative frequencies can be used as a species diversity index. This paper first theoretically develops the indices of this type, then applies them to forestry data. As examples of diversity indices, this paper explores the taxonomic diversity and the newly introduced amino acid diversity, which is a modification of the nucleotide diversity in genetics. The first, mathematical part shows that both indices can be decomposed into three inner factors; evenness of relative frequencies (=the Simpson index), the simple average over species differences regardless of relative frequencies, and the taxonomic or genetic balance in relative frequencies. The taxonomic diversity has another decomposition: the sum over the Simpson indices at all the taxonomic levels. The second part examines the effects of different forest management techniques on diversity. It is shown that a thinning operation for promoting survival of specific desirable species also contributed to increasing the taxonomic diversity. If we calculated only conventional indices that do not incorporate species relatedness, we would simply conclude that the thinning did not significantly affect the diversity. The theoretical developments of the first part complement the result, leading us to a better interpretation about contrasting vegetation structures. The mathematical results also reveal that the amino acid diversity involves redundant species, which is undesirable when measuring diversity; hence, this index is used to demonstrates crucial points when we introduce species relatedness. The results suggest further possibilities of applying diversity indices incorporating species differences to a variety of ecological studies.     

Influence of morphology and amphibious life-style on the feeding ecology of the mudskipper Periophthalmus argentilineatus

The potential feeding advantages that are offered to the barred mudskipper Periophthalmus argentilineatus by its amphibious life-style were investigated. To this end the feeding ecology of these fish, the position they occupy in the mangrove food web and the importance of different morphological factors for their diet were studied. Analysis of gut contents showed that the major component of the barred mudskipper diet changes during growth from small crustaceans ( e.g. copepods and amphipods) to polychaetes to mangrove crabs. This dietary shift was found to be facilitated through enlargement of the mouth, as well as elongation of the gut. The use of stable isotope analysis revealed that barred mudskippers had a similar trophic position as other zoobenthivore fish species, but that their diet did not appear to be affected by competition for food with other zoobenthivores. The amphibious habits of the barred mudskipper provide specific advantages to its feeding ecology, such as access to an abundant food source of mangrove crabs, which are mostly inaccessible for other fish species.     

Seed protein electrophoresis of some cultivated and wild species of <Emphasis Type="Italic">Chenopodium</Emphasis>

Seed protein profiles of 40 cultivated and wild taxa of Chenopodium have been compared by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The relative similarity between various taxa, estimated by Jaccard’s similarity index and clustered in UPGMA dendrogram, is generally in accordance with taxonomic position, crossability relationships and other biochemical characters. Eight accessions of C. quinoa studied are clustered together and show genetic similarity with closely related C. bushianum and C. berlandieri subsp. nuttalliae. The taxa included under C. album complex are clustered in two groups which show that these taxa are a heterogenous assemblage and their taxonomic affinities need a reassessment. Other wild species studied are placed in the dendrogram more or less according to their taxonomic position.