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Estuaries are essential habitats for recreational and commercial fish that are shaped by both natural and anthropogenic processes. In Louisiana a combination of climate change and planned coastal restoration actions is predicted to increase freshwater introduction to coastal estuaries. As such there is a need to quantify the relationships between estuarine fish ecology and salinity to aid in predicting how species will respond to shifts in salinity. We investigated the relative abundance and dietary niches of adult (24.5 ± 5.4 cm standard length) spotted seatrout Cynoscion nebulosus across varying salinity regimes (oligohaline, mesohaline, and polyhaline) within Barataria Bay, Louisiana, using a combination of net sampling and gut content and stable isotopes analysis. We found that the relative abundance of C. nebulosus was lowest at the oligohaline site, translating to approximately five fewer fish captured for every single psu decrease in a site's average annual salinity. In contrast, we found that diets and, to a lesser extent, isotopic niches had a high degree of overlap across sites with differing salinity regimes. Fish and penaeid shrimp were the most common and important prey taxa recovered from guts at all sites. The small isotopic differences found among sites were likely due to spatial variation in hydrogeochemical baselines, and the observed isotopic overlap provides support for the idea that C. nebulosus move between adjacent salinity regimes and forage throughout Barataria Bay. Our results contribute to a greater understanding of the salinity preference and trophic ecology of C. nebulosus that can aid in predicting their responses to future salinity and habitat changes within Barataria Bay associated with predicted climate change and planned coastal restoration actions. [ABSTRACT FROM AUTHOR]

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Metabarcoding approaches are powerful tools to unravel trophic relationships between predators and prey. To apply metabarcoding analyses on invertebrate gut contents, specimens must be well preserved from DNA degradation, thus the trapping method should be selected accordingly. Dry pitfall traps are commonly assumed to provide a better DNA preservation than traps that use a killing agent. However, this assumption has never been specifically tested for gut content analyses. In our study, we compared how two types of pitfall trapping, dry vs. with brine, affect the conservation of prey DNA contained in the digestive tract of predators and subsequent metabarcoding analyses. We placed dry and 'classic' pitfall traps in oilseed rape fields within an intensive agricultural area in the French Nouvelle‐Aquitaine region. Traps were set up in autumn and compared for carabid trapping efficiency as well as our capacity to retrieve dietary information from the digestive tract of the main carabid species, Nebria salina (Fairmaire & Laboulbène) and Calathus fuscipes (Goeze) (both Coleoptera: Carabidae). The PCR success rate was higher in dry pitfall traps compared to classic ones for N. salina. We hypothesise that this was due to the presence of PCR inhibitors in the gut of this species. The ability to sequence prey DNA did not differ between specimens caught in both trap types. The list of preyed species was similar between both trap types. However, sequencing yielded more prey operational taxonomic units (OTUs) from specimens caught in dry pitfall traps, leading to differences in prey community composition and a greater ability to reconstruct prey community. Our analyses also shed light on the prey spectrum of C. fuscipes and N. salina in oilseed rape in autumn. [ABSTRACT FROM AUTHOR]

We evaluated the potential of the euryhaline copepod Pseudodiaptomus inopinus as a prey to enhance the feeding activity of red sea bream Pagrus major larvae. Pseudodiaptomus inopinus was used to evaluate free amino acid composition and dietary effects on the rearing performance of fish larvae, in comparison to rotifers (control prey). Among free amino acids, alanine, arginine, and glycine were markedly higher in P. inopinus than in rotifers. Larvae were reared for 20 days post-hatching under three feeding treatments: rotifers (control), rotifers supplemented with copepods, and copepods only. Larvae fed copepods alone had a higher growth rate than those in the other treatments. However, the survival rates of these larvae were lower than those under control or copepod supplementation. While equivalent stocking densities of rotifers were employed in the rearing water for both larvae, whether supplemented with copepods or not, the supplemented treatment yielded diminished larval survival and failed to enhance growth rates. According to gut content analysis, larvae receiving supplemented treatment preferentially fed on copepods, and the number of ingested rotifers was reduced. As a result, total ingested mass was lower in the supplemented larvae. This study suggests that copepods containing free amino acid species negatively affect prey acceptance of fish larvae. [ABSTRACT FROM AUTHOR]

Investigating biological aspects of migratory marine animals like sea turtles is challenging. The Adriatic Sea is a key Mediterranean foraging ground for loggerhead turtles, yet certain feeding behaviors remain poorly known, including winter feeding and foraging within the neritic area of the Gulf of Manfredonia. With high fishing effort, this area experiences considerable turtle bycatch from trawlers during winter, representing an important conservation issue. Insights on how and to what extent the species interacts with anthropogenic threats such as trawlers and debris can be obtained from diet analysis. We examined feces and gut contents from 57 bycaught or stranded turtles to assess active feeding and digestion time during winter, identify and quantify prey items, evaluate feeding patterns among size classes, and ascertain the anthropogenic impact via debris and fishing discard ingestion. Our findings show that turtles feed actively during winter, primarily on benthic items, starting from a small size (32 cm Curved Carapace Length). No size effect was observed on dietary diversity or biomass percentage. We identified 37 Operational Taxonomic Units (OTUs) across 10 dietary groups, with crustaceans and mollusks being most prevalent. Osteichthyes and cephalopods, likely scavenged from trawl discard, were also common, implying intensive local trawling may attract turtles, increasing bycatch and mortality rates. The frequency of anthropogenic material ingestion was comparable to other Mediterranean regions and its presence in feces suggests non-lethal effects, if any. This study shows how information on seasonal feeding behavior can provide insights into how the relationship of the species with the environment and threats changes over time, ultimately steering conservation efforts. [ABSTRACT FROM AUTHOR]

Background: This study focused on the diet of Clithon retropictum, level II endangered species in Korea. Since the development of brackish water zones has led to a decline in the population of this species, to obtain information on the ecology of C. retropictum required for its conservation and restoration. To investigate the actual preys of C. retropictum in south coast of Korea, we conducted high-throughput sequencing and metabarcoding techniques to extract DNA from gut contents and periphyton in their habitats.Results: Total 118 taxonomic groups were detected from periphyton samples. 116 were Chromista and Cyanobacteria dominated in the most samples. In gut contents samples, 98 taxonomic groups were detected. Similar to the results of periphyton, 96 were Chromista and Cyanobacteria dominated in the most samples. In the principal component analysis based on the presence/absence of taxonomic groups, gut content composition showed more clustered patterns corresponding to their habitats. Bryophyta was the most crucial taxonomic group explaining the difference between periphyton and gut contents compositions of C. retropictum.Conclusions: Our finding suggests that C. retropictum may not randomly consume epilithic algae but instead, likely to supplement their diet with Bryophyta.

Abstract The feeding habits of Chironomidae in hill streams in the pampean region have not been described. In this study, we analyzed the gut contents of this insect family with an aim at establishing their diet in an intermittent stream in the Ventania-Hill system. We sampled three sites with different habitat characteristics (i. e., altitude, substrate type, and current velocity). Of the total of nine taxa were recorded, the only one present at all sites was Corynoneura sp. 1. The food items found were detritus, diatoms, filamentous chlorophytes, euglenophytes, vascular plants, fungi, and animal remains. Most of the taxa could be classified as gathering collectors, with those having a higher proportion of detritus in the gut contents although the guts of Pentaneura nr. cinerea, Cricotopus sp. 1, and Onconeura analiae included high proportions of animal remains. No differences in the feeding habits were attributable to the location in the stream. This research contributes to our understanding of the trophic habits of Chironomidae in an intermittent hill stream system of South America.

A remarkable specimen of the actinopterygian fish Pachycormus macropterus from the Early Jurassic (Toarcian) Posidonienschiefer Formation of Germany exceptionally preserves an unusually large ammonite inside its gut. The ammonite was swallowed by the fish, likely by accident, and represents the first direct evidence for an actinopterygian fish consuming an ammonoid. Exceptional aragonite preservation of the conch retaining partial nacreous lustre, combined with only minor acid etching of the shell, strongly indicates that the ammonite was ingested immediately prior to and was directly responsible for the fish's death. The fish's stomach provided a microenvironment protecting the aragonite from chemical dissolution. [ABSTRACT FROM AUTHOR]

The sea urchin Tripneustes gratilla is a major grazer and is, hence, an excellent key model organism to study to gain a better understanding of responses to changes in its habitat. We investigated whether there are significant variations in the feeding and reproductive phenotypic traits of populations from three seagrass bed sites, with respect to their proximity to fish farms in Bolinao, northwestern Philippines. We established three stations in each of the three sites: the far, the intermediate, and those near the fish farms, and compared the sea urchins' phenotypic traits and determined whether these were related to seagrass productivity and water parameters. Regardless of the sampling period, adult sea urchins (66.92 ± 0.27 mm test diameter, TD, n = 157) from the areas intermediate and near to the fish farms had significantly lower indices of Aristotle's lantern, gut contents, gut and gonads, and lower gonad quality (high percentage of unusual black gonads), compared to those from the far stations. Multivariate analysis showed that the smaller feeding structures and gut, lower consumption rates and lower gonad indices and quality of sea urchins in the intermediate and near fish farms were positively related to lower shoot density, leaf production and species diversity, as well as lower water movement in those stations. The larger size of the Aristotle's lantern in the far stations was not related to food limitations. More importantly, the phenotypic variability in the feeding structures and gonads of sea urchins in the same seagrass bed provides new evidence regarding the sensitivity of this species to environmental factors that may affect variability in food quality. [ABSTRACT FROM AUTHOR]

Objective: The study was conducted to investigate the gut content and record morphometric and hematological parameters in the common hoopoe (Upupa epops). Materials and Methods: Twenty samples of healthy birds (10 from each sex) were collected from different locations in Okara District, Punjab, Pakistan, from September 2020 to March 2021. Birds were captured live for blood samples and morphometric and gut analyses. Results: It was revealed that the concentrations of different hematological parameters were as follows: hemoglobin, 20.03g/dl; red blood cells, 3.28 × 106/μl; white blood cells, 326.67 × 103/ μl; hematocrit, 56.47%; MCV, 173.33 FL; MCH, 57.4 pg; MCHC, 57.4 pg; PLT, 8.33/μl; and RDW, 8.33/μl. The percentages of neutrophils, lymphocytes, monocytes, and eosinophils were 84.67%, 11.67%, 2.00%, and 1.67%, respectively. The gut content of the common hoopoe mostly consisted of Coleoptera and Acrididae larvae. However, Lepidoptera, Gryllotalpidae, and sand were also recorded, along with seeds of Salvadora persica. Conclusions: There were no significant differences between male and female U. epops in feeding content, total weight of the gut, or weight of the empty gut. Regarding the morphometric param¬eters, there was a significant difference in both sexes' wingspan, body length, and body weight. Males were significantly heavier than females. [J Adv Vet Anim Res 2022; 9(2.000): 290-294]

The tiger-fly Coenosia attenuata Stein (Diptera: Muscidae: Coenosiini) is a generalist predator that preys on several pests of greenhouse crops and is considered a biological control agent in the Mediterranean region. Previous behavioural observations identified its preferred prey, but a more in-depth evaluation will benefit from using Polymerase Chain Reaction amplification of prey DNA remains in the gut of this predator. To evaluate the rate of decay and suitability of this method for use in the field assessments, we carried out a laboratory feeding calibration experiment on 355 females of C. attenuata, which were killed at different intervals of time after ingestion (10 time points from 0 to 48 h). The prey species tested were: Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae: Trialeurodini), Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae), Diglyphus isaea (Walker) (Hymenoptera: Eulophidae: Cirrospilini), Bradysia impatiens (Johannsen) (Diptera: Sciaridae) and Drosophila mercatorum Patterson & Wheeler (Diptera: Drosophilidae: Drosophilini). Based on a probit model, amplification success of prey DNA declined exponentially with increasing time after ingestion. The half-time molecular detection differed between species, ranging from an average of 5 h for T. vaporariorum and D. isaea, 6 h for B. impatiens, 15 h for L. huidobrensis to more than 40 h for D. mercatorum. This study confirmed the feasibility of using DNA based detection to identify prey species in the gut contents of C. attenuata and provided calibration curves for a better understanding of predation activity in this agroecosystem.

The sea urchin Tripneustes gratilla is a major grazer and is, hence, an excellent key model organism to study to gain a better understanding of responses to changes in its habitat. We investigated whether there are significant variations in the feeding and reproductive phenotypic traits of populations from three seagrass bed sites, with respect to their proximity to fish farms in Bolinao, northwestern Philippines. We established three stations in each of the three sites: the far, the intermediate, and those near the fish farms, and compared the sea urchins’ phenotypic traits and determined whether these were related to seagrass productivity and water parameters. Regardless of the sampling period, adult sea urchins (66.92 ± 0.27 mm test diameter, TD, n = 157) from the areas intermediate and near to the fish farms had significantly lower indices of Aristotle’s lantern, gut contents, gut and gonads, and lower gonad quality (high percentage of unusual black gonads), compared to those from the far stations. Multivariate analysis showed that the smaller feeding structures and gut, lower consumption rates and lower gonad indices and quality of sea urchins in the intermediate and near fish farms were positively related to lower shoot density, leaf production and species diversity, as well as lower water movement in those stations. The larger size of the Aristotle’s lantern in the far stations was not related to food limitations. More importantly, the phenotypic variability in the feeding structures and gonads of sea urchins in the same seagrass bed provides new evidence regarding the sensitivity of this species to environmental factors that may affect variability in food quality.

Context: Zooplanktivorous fish are a key link between abundant zooplankton and higher trophic levels but the foraging behaviour of zooplanktivorous fish is not fully understood. Selective feeding behaviours have been observed, with many species of planktivorous fish targeting certain species and sizes of zooplankton for prey. However, why certain size classes of zooplankton are preferred remains unclear. Aim: This study investigated prey selection by three zooplanktivorous fish species through the lens of optimal foraging theory. Methods: We assessed the size structure of zooplankton in the environment and compared this with the size distribution of zooplankton in gut contents from three zooplanktivorous fish. Key results: The targeted prey size of Atypichthys strigatus and Scorpis lineolata aligns with the prey size classes in the environment that contain the highest overall biomass. Trachurus novaezelandiae showed little evidence of targeting these size classes. Conclusions: These prey sizes therefore represent the most efficient prey to target because the return on foraging effort is greatest. By contrast, T. novaezelandiae showed only an underselection of large and small prey. Implications: By incorporating this information on this key trophic link between zooplankton and fish, ecosystem models could better resolve the size dependant predation, particularly in size-based models. This paper shows that 2 of 3 species of estuarine fish target specific sizes of zooplankton rather than eating everything they encounter. This pattern is driven by the fish attempting to maximise the biomass consumed by targeting the zooplankton size classes with the most overall biomass in the environment. [ABSTRACT FROM AUTHOR]

Objective: The study was conducted to investigate the gut content and record morphometric and hematological parameters in the common hoopoe (Upupa epops). Materials and Methods: Twenty samples of healthy birds (10 from each sex) were collected from different locations in Okara District, Punjab, Pakistan, from September 2020 to March 2021. Birds were captured live for blood samples and morphometric and gut analyses. Results: It was revealed that the concentrations of different hematological parameters were as follows: hemoglobin, 20.03g/dl; red blood cells, 3.28 × 106/µl; white blood cells, 326.67 × 103/ µl; hematocrit, 56.47%; MCV, 173.33 FL; MCH, 57.4 pg; MCHC, 57.4 pg; PLT, 8.33/µl; and RDW, 8.33/µl. The percentages of neutrophils, lymphocytes, monocytes, and eosinophils were 84.67%, 11.67%, 2.00%, and 1.67%, respectively. The gut content of the common hoopoe mostly consisted of Coleoptera and Acrididae larvae. However, Lepidoptera, Gryllotalpidae, and sand were also recorded, along with seeds of Salvadora persica. Conclusions: There were no significant differences between male and female U. epops in feeding content, total weight of the gut, or weight of the empty gut. Regarding the morphometric parameters, there was a significant difference in both sexes' wingspan, body length, and body weight. Males were significantly heavier than females. [ABSTRACT FROM AUTHOR]

Sustainable aquaculture requires the efficient use of natural pond resources as well as supplements to meet the dietary requirements of fish species. However, aquaculture diets are often produced without considering the lysine content of the natural production in the pond. As such, two plant-based diets, a control diet (L-Con) supplemented with 5.00 g lysine kg−1 diet and a lysine deficient diet (L-Def) without supplementation were fed to Nile tilapia raised in ponds with five replicates ponds for each diet. The aim was to investigate the effect of L-Def diet on plankton selectivity, metabolic growth, haemato-biochemical parameters, gut content and intestinal morphometry. Fish were fed a fixed ration of 18 g kg−0.8 d−1 for 10 weeks. During the experimental period, plankton species in the fish guts were identified and categorised to phylum level: phytoplankton phyla – Euglenophyta, Bacillariophyta, Cyanobacteria, and Chlorophyta; zooplankton phyla - Copepoda, Rotifera, and Cladocera. Fish in ponds receiving the L-Def diet selected positively for all phyto and zooplankton phyla but the selectivity was only significantly higher for Bacillariophyta with fish in ponds receiving the L-Con diet (P

Owing to rapid growth of the global population and increased consumption of natural resources, insects, as the largest biological group on Earth, are gradually gaining attention within the vision of a circular economy. Edible insects, rich in a variety of bioactive compounds possessing diverse biological functions, are gradually being explored as novel products for utilization. This review provides a comprehensive summary of the primary bioactive compounds and biological functions in edible insects, with a particular focus on the impact of various pretreatment methods. In light of industrialization, we have also summarized the potential for enriching bioactives via the substrate and fermentation, and proposed future research directions and applications for edible insects. Edible insects contain various bioactive compounds, including phenolics, polysaccharides, peptides, fatty acids and others. The consumption of edible insects has been associated with numerous health benefits, such as antioxidant, anti-obesity, anti-diabetic, anti-cancer, gastrointestinal protective, hepatoprotective, and immunomodulatory effects. Furthermore, pretreatment methods significantly influence the characterization of bioactive compounds and functions. Notably, the effect of gut contents on insects is often overlooked. Therefore, the characterization of bioactive compounds and functions is revealed based on various pretreatment and enrichment methods. Future research aims to capitalize on the benefits of edible insects, integrating a range of omics approaches and clinical trials, to advance their potential application in the functional food and health products industry. [ABSTRACT FROM AUTHOR]

This is the first study conducted on the food and feeding habits of the yellowtail mullet (Minimugil cascasia), in the Ganga River (India). The gut contents of 276 individuals (TL: 45.32–89.79 mm) were investigated. Dominant food items of the yellowtail mullet included three diatoms, namely Cyclotella sp., Amphora sp., and Aulacosiera sp.; one green alga, Scenedesmus sp.; two blue-green algae, Merismopedia sp. and Nostoc sp. The food composition varied according to the size class of fish, with small individuals feeding on the blue-green algae and large one feeding on the diatoms and green algae. Sand and detritus comprising 84.16% and 81.87% by frequency and 48.83% and 20.31% by volume, respectively, dominated in the gut contents of the yellowtail mullet. The relative gut length (RGL) of the yellowtail mullet suggested an omnivorous iliophagous feeding habit, where foods items are picked up from the bottom mud layer known as the iliotrophic layer. [ABSTRACT FROM AUTHOR]

Knowing the interactions between exotic and native species is essential to establish possible threats to the local fauna. In this study, we assessed the use of food resources and diet overlap between a recently introduced snail, Sinotaia quadrata, and a native species, Pomacea canaliculata. We analyzed the gut content and stable isotope of snails and resources in a lowland stream where both species coexist. Both Schoener's and isotope dietary overlap indexes supported dietary overlap. Conversely, gut content analysis showed differences in consumption: S. quadrata consumed more detritus and diatoms than P. canaliculata, whose diet was characterized by detritus and macrophyte remains. Macrophytes were the resource that most contributed to the diet of both species, as shown by stable isotope mixing models. The combination of both techniques, gut content and stable isotope analysis, indicated that S. quadrata consumed macrophyte detritus while P. canaliculata ate fresh macrophytes. This difference indicates differential use of food resources between the studied species coexisting in a lowland stream. Although no negative trophic interaction was found, we highlight the importance of continuing to monitor interactions for other resources and studying possible risks to the local fauna. [ABSTRACT FROM AUTHOR]

The present study aims to provide biological characteristics such as the Length-weight relationship, food and feeding habits, sex ratio, maturity stages, reproductive development and fecundity of Aluterus monoceros caught by trawlers landed at Veraval coast, the Gujarat state of India, from September 2019 to March 2020. The overall sex ratio observed was 1:1.057; the results indicated dominance of females in September, October, November 2019 and February 2020. ‘b’ value for male sex was 2.8159 and female was 2.7968. Immature stages (I & II) and mature stages (III, IV, & V) were observed in all the months. In contrast, spent condition (VI & VII) was observed only in September, October, January and March. The average fecundity per gram body weight was 6537 and the average fecundity determined for the study period of seven months was 116195. There was one peak in the fecundity from September to October. The percentage frequency of the ova diameter was estimated, and it revealed that the maximum number of ova were in the size category of 320-420µm. IRI estimates showed that the percentage composition of different food items varied in other months according to their availability and preference. The gut contents are clupeids, Acetes sp., Cnidarians, Gastropods, Portunidae, Euphylax sp., juveniles of finfishes, worms and green algae. The adult individuals of the species were cannibalistic. Long term monitoring of species biology will provide policy measures for Aluterus monoceros fishery for its sustainable fishery management for future generations. [ABSTRACT FROM AUTHOR]

Food and feeding habits of fishes helps to explore their nature, environmental use (specially niche) and trophic interactions in the ecosystem. A study on stomach content analysis is vital in giving useful information of fish diets, role of fish in their habitat and to inducement stock assessment models. The Cyprinus carpio (Common carp) and Oreochromis niloticus (Nile Tilapia) are a freshwater fish species widely distributed in eutrophic waters of Asia, Europe and Africa. O. niloticus fed primarily on detrital aggregate. Plant material was the second most heavily consumed food and varied in its dietary contribution. C. carpio showed an overwhelming reliance on detrital aggregate throughout the season, there was a distinct but small dietary prey component which consisted mainly of chironomids. Both species have a great socioeconomic importance for the region and keeps providing for a population of about 1000 to 1500 fishermen at Prayagraj region, India. The fish samples of C. carpio and O. niloticus were collected from the fish markets of Teliarganj and Daraganj, Prayagraj, Uttar Pradesh during July 2017 to June 2019. The length of fishes varied from 132 to 826 mm for C. carpio and 89 to 427 mm for O. niloticus. Green algae, blue green algae, diatoms, protozoans, rotifers, insect parts, sands and unidentified items were recorded from gut during all seasons in both species which were collected from the Ganga river. Present study indicated that C. carpio and O. niloticus were herbivorous fish species from the Ganga river at Prayagraj, India. [ABSTRACT FROM AUTHOR]

Between 2000-2020, more than ten new populations of the invasive American bullfrog (Lithobates catesbeianus) have been reported in the southern cone of South America. We studied the stomach contents of 126 bullfrogs from a population at an early invasion stage in Uruguay (Aceguá, Cerro Largo Department). We observed a rich diet, with extensive prey volume range (1 mm3 to more than 7 000 mm3); the most frequent items were Hymenoptera (19.6%), Coleoptera (16.4%), Amphipoda (13.3%), Anura (8.9%) and Heteroptera (8.7%). Despite some overlap, differences were observed in volume (X2 = 54.6, p <0.001, d.f. = 2) and prey quantity (F = 8.1, p <0.001, d.f. = 79) between males, females, and juveniles. Juveniles showed significantly higher consumption of terrestrial prey by count (82% of their total ingestion) than adults (29% for males and 32% for females) (X2 = 28.5, p <0.001, d.f. = 2). Adults, especially females, showed a high frequency of cannibalism (33% of their total ingestion; X2 = 20.9, p <0.001, d.f. = 2). Comparing our data with other bullfrog regional studies, we found great plasticity in trophic habits and differences in the incidence of cannibalism (higher incidence in the populations of Aceguá, Uruguay, and Buenos Aires, Argentina). These differences could be related to local biodiversity, but also could be affected by the invasion phase. Cannibalism frequency was higher in small bullfrog populations, where it could be favoring the establishment success. This shift in foraging strategies during the invasion process had been insufficiently evaluated in amphibians. Knowing the ecological determinants for the invasion by bullfrogs can be useful to the development of management strategies. [ABSTRACT FROM AUTHOR]

DNA metabarcoding analysis for gut contents has been shown to compensate the disadvantage of traditionally morphological identification and offer higher resolution of prey items in an efficient way. Holland's carp (Spinibarbus hollandi) is a freshwater fish native to southern and eastern Taiwan. In the past two decades, this species has been introduced as a sport fish into the river basins of northern and western Taiwan. The large body size and active predation make it a potential threat for native fishes, but which native species are preyed by Holland's carp remains unknown. In this study, the diet from the gut contents of Holland's carp from the Zhonggang River, an invaded basin, was examined using DNA metabarcoding from 51 individuals and by morphological examinations on 140 samples. Detritus of plants were found in 83.6% samples (117 individuals). Twenty fish species of seven families were identified by DNA metabarcoding, including species of all water layers. Taiwan torrent carp (Acrossocheilus paradoxus) and Rhinogobius spp. are the most common prey items. Based on the results of this study, Holland's carp is considered an opportunistic omnivore because of its diverse diet items, which is an important trait for successful invasive fish species. The population decline of Opsariichthys pachycephalus may not result from the invasion of Holland's carps. Nonetheless, the time lag between successful invasion and the samplings of this study may be a concern because the population size of O. pachycephalus may have declined and become difficult to prey. The Holland's carps consumed the least species in winter; nonetheless, the occurrence frequencies of preys among seasons were not significantly different probably because of limited temperature fluctuation. The smallest Holland's carps consumed the least prey species compared to other size categories, similar to the relationship of prey species number to size of invasive largemouth bass (Micropterus salmoides). [ABSTRACT FROM AUTHOR]

The tiger-fly Coenosia attenuata Stein (Diptera: Muscidae: Coenosiini) is a generalist predator that preys on several pests of greenhouse crops and is considered a biological control agent in the Mediterranean region. Previous behavioural observations identified its preferred prey, but a more in-depth evaluation will benefit from using Polymerase Chain Reaction amplification of prey DNA remains in the gut of this predator. To evaluate the rate of decay and suitability of this method for use in the field assessments, we carried out a laboratory feeding calibration experiment on 355 females of C. attenuata, which were killed at different intervals of time after ingestion (10 time points from 0 to 48 h). The prey species tested were: Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae: Trialeurodini), Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae), Diglyphus isaea (Walker) (Hymenoptera: Eulophidae: Cirrospilini), Bradysia impatiens (Johannsen) (Diptera: Sciaridae) and Drosophila mercatorum Patterson & Wheeler (Diptera: Drosophilidae: Drosophilini). Based on a probit model, amplification success of prey DNA declined exponentially with increasing time after ingestion. The half-time molecular detection differed between species, ranging from an average of 5 h for T. vaporariorum and D. isaea, 6 h for B. impatiens, 15 h for L. huidobrensis to more than 40 h for D. mercatorum. This study confirmed the feasibility of using DNA based detection to identify prey species in the gut contents of C. attenuata and provided calibration curves for a better understanding of predation activity in this agroecosystem. [ABSTRACT FROM AUTHOR]

Palinustus waguensis Kubo, 1963, is the deep-sea Japanese blunthorn lobster belonging to the Family Palinuridae. It is a species that has been rarely reported, living in rocky habitats on deep-reef slopes at a depth of 100-250 m. An estimated catch of 100 kg of P. waguensis consisting of 113 males, 54 females, and 23 berried lobsters were collected during the first fortnight of January 2019 from the multi-day shrimp trawls operating off Sakthikulangara, Kerala, India. The mean total length was recorded as 112.3 mm in males, 102.6 mm in females. The parameters of the lengthweight relationship were estimated as, a = 0.041, b = 2.84 for males and a = 0.05, b = 2.86 for females, which were not significantly different (P > 0.05, r2 > 0.90) between the males and females. The relative condition factor (K) in the males and females of P. waguensis ranged from 2.07-4.96 and 1.87-3.86, respectively, attributing to the better feeding efficiency in males. Food and feeding analysis revealed the dietary content as fish (53 %), crab (23.5 %), shrimp (7.8 %), digested matter (11.6 %), and foraminifera (4 %). Feeding intensity analysis about the fullness of the stomach showed the specimens bearing full stomachs (11.3 %), three-fourth full (9.9 %). Length at 50 % maturity (Lm50) was 96.9 mm. Gonado-somatic index (GSI) ranged from 3.39 to 8.13. The present study forms the first report on the biology of the deep-water Japanese blunthorn lobster, P. waguensis from India. [ABSTRACT FROM AUTHOR]

Deep-sea hemichordates Torquaratoridae gen. sp. reach high abundance up to 12 spec. m–2 at the depths of 1830–2130 m on the slope of the Volcanologists Massif in the south-western part of the Bering Sea, dominating in the benthic community at these depths. Their abundance exceeds by two orders the values recorded earlier. In order to clarify this phenomenon, we examined the gut contents of Torquaratoridae gen. sp. The detritus particles and frustules of planktonic diatoms Thalassiosira, Coscinodiscus, Actinocyclus, Chaetoceros, Neodenticula, and Grammatophora were the most common in the gut, as well as the remains of skeletons of benthic invertebrates with little admixture of mineral particles. According to obtained data, Torquaratoridae gen. sp. are mobile deposit feeders with high selectivity to fresh phytodetritus, able to compete with holothurians occupying similar trophic niche. Unusually high abundance of acorn worms is apparently related to high organic matter flux to the seafloor as a result of spring phytoplankton bloom in the surface water layer of the Bering Sea. [ABSTRACT FROM AUTHOR]

A 2-year study was undertaken to understand feeding preferences of the eastern oyster Crassostrea virginica when growing in conditions of eutrophication and variable flow. Oysters were suspended in the Rhode River, a tributary of Chesapeake Bay, Maryland, USA, and a subset of these oysters was collected monthly, measured in height to determine growth, and the phytoplankton in their gut were examined both microscopically and using indicator pigments and compared with phytoplankton abundance and composition in the water column. The data herein summarize the oyster growth and the gut contents with respect to phytoplankton cell numbers and composition and with respect to signature pigments.

Coastal and estuarine nurseries are composed of habitats with different biotic and abiotic features. Quantifying the contribution of different habitats within nurseries to juvenile fish feeding would help identify those that are essential in the completion of their life cycle, by providing food resources that maximise growth and survival. Essential habitats for four bentho-demersal fish species (whiting, sea bass, plaice and common sole) in an estuarine nursery were identified using gut contents and stable isotopes. Habitats differed in isotopic ratios and benthic communities. The estuarine gradient defined the macrofauna communities and sources of organic matter used by primary consumers. Trophic niche overlaps and trophic contribution of habitats highlighted that the species used both intertidal and subtidal habitats as feeding grounds. Flatfish were local feeders and fed on prey available mainly in the habitat in which they were caught, suggesting feeding behaviour that required little energy for movement. Sea bass were concentrated in upstream habitats, with intertidal mudflats contributing for nearly half of its diet. Whiting had an ubiquitous feeding strategy, suggesting that it may target prey with the most energetic gain in the habitats. Hence, habitats were used simultaneously during the same season or asynchronously throughout the year by the juvenile fish studied, suggesting no preference for a specific habitat at the community scale. Finally, both trophic tracers demonstrated the trophic importance of intertidal mudflats, especially for the sea bass and common sole, with contributions up to the half and two-third of their diet respectively. Graphical abstract [ABSTRACT FROM AUTHOR]

The hypothesis of community-wide character displacement (CWCD) predicts that coexisting species in the same guild should differ in morphological traits associated with resource acquisition, such that interspecific competition is unlikely. Hypothesis tests often focus on trophic structures involved in food acquisition, because variations in the morphology of foraging apparatus and diet composition may be directly related. Empirical evidence of such associations among sympatric guild members is, however, uncommon. The predatory larvae of caddisflies in the family Hydrobiosidae are ideal for studies of CWCD because the morphology of the prehensile foreleg, used to capture prey, varies markedly among genera. Further, hydrobiosids typically occur as species-rich guilds, often with 10-20 species in a single community. Although the larvae are known to be predatory, detailed information on the diet of coexisting species is scarce. This study tested whether larval diet varied among multiple, sympatric species of hydrobiosid caddisflies that differed in foreleg morphology. Larval specimens were collected in summer and primarily from one river in central Victoria, Australia. Gut contents of late instar larvae were examined to describe diet composition, and diet was compared among taxa using measures of diet breadth and overlap. Seven sympatric species from six genera that differed in foreleg morphology were collected and late instar larvae were exclusively carnivorous. Diet composition and breadth varied markedly among some species, and diet was associated with morphology of the prehensile foreleg. Specialist predator species consumed predominantly chironomids and had high diet overlap. Generalists consumed primarily chironomids and mayflies, but overlap varied depending upon the preferred mayfly family and representation of other prey items, such as blackflies and insect eggs. All predator species consumed some caseless caddisflies and intraguild predation was strong in at least one species. The marked differences in diet and foreleg morphology among hydrobiosid species are consistent with the notion that CWCD influences guild membership and may facilitate species coexistence within guilds that are typically species-rich. Although rarely considered for freshwater communities, CWCD may help explain species membership within other guilds. The magnitude of diet variations among genera within this family are more usually found across multiple families or orders, demonstrating that assumptions about the diet of even closely related taxa may be erroneous. [ABSTRACT FROM AUTHOR]

Analysis of feeding habits was performed for early life stages of Brachyplatystoma rousseauxii and Brachyplatystoma filamentosum in the Madeira River, Brazil. Stomach contents of B. rousseauxii and B. filamentosum were identified and analysed to provide the percentage of frequency of occurrence (%FO) and area (%A) and the alimentary index (IAi). The order Diptera represented the most important item consumed by both species. This is the first analyses of the trophic ecology of these ecologically and economically important species of the Amazonian region in early life stages. [ABSTRACT FROM AUTHOR]

In the present study, an attempt has been made to investigate the food and feeding habits of the N. mesoprion landed at Veraval harbour along the Saurashtra coast. The specimens were collected every fortnight interval from August 2018 to March 2019. During the present study, a total of 228 specimens were collected. The studies showed that N. mesoprion is a demersal carnivorous. Food items mainly consist of Crustaceans, Fish, Molluscs and Digested material. The diet included Acetes spp., Penaeid shrimp, Crab, Lobster, Squilla, Saurida spp., Trichiurus spp., Bregmaceros spp., Stollephorus spp., Flatheads, Scads, Lizard fishes, Octopus and Squid. Fish and Crustacean especially Acetes spp. and Penaeid shrimps were the common dietary component. The Gastrosometic index of the male and female was higher in August and September. The percentage of empty stomachs and one-fourth stomachs were present in all the months with a high percentage that indicates poor feeding intensity during most of the months. [ABSTRACT FROM AUTHOR]

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ABSTRACT Studies of trophic networks and the evaluation of processes that occur along altitudinal gradients in river systems are of great importance because they allow an understanding of energy flow dynamics and provide scientific tools for the planning and management of river ecosystems. This research describes the trophic network of aquatic macroinvertebrates along an altitudinal gradient of the Gaira River, a mountain Neotropical watercourse located in the Sierra Nevada de Santa Marta in northern Colombia. The organisms were collected in the upper, middle and lower reaches of the river during the rainy and dry seasons (between 2010 and 2013). Trophic relationships were evaluated through gut content analysis. The contents were determined and quantified using photographs and expert review, and a binary consumption matrix was used to determine the characteristics of the trophic network. We characterized the diet composition at each site for each season using discriminant analysis. Trophic networks during the dry seasons showed higher trophic species richness and linkage density, and the predominance of coarse particulate organic matter (CPOM) and fine particulate organic matter (FPOM) in the high and medium sections of the river. During the dry seasons the diets had a lower number of basal species, but in the low river section there was a high percentage of fungi and microalgae. During the rainy seasons, no patterns were observed for the percentage of resources. Results indicated a direct relation between periods of hydrologic stability and an increase of CPOM during dry seasons and an increase of resource diversity consumed by macroinvertebrates at all sites during the rainy season, showing that changes in trophic networks of the Gaira River were more important during seasonal periods than along the altitudinal gradient.

Gut contents of Pacific saury Cololabis saira during their feeding migration through a transition zone between subtropical and subarctic waters in the North Pacific Ocean are reported. Geographic changes in feeding habits and preferences are described for the months of June and July, for the years 2012, 2016, and 2017. Pacific saury prey comprised 27 taxa. Cluster analysis based on numerical abundance of these prey taxa in guts indicated six Pacific saury feeding types (A to F) existed. Of these, types A–E occurred in low sea surface temperature waters (ca 14°C). Feeding patterns reveal N. plumchrus/flemingeri tended to be important prey species in areas west of ca 175°E, whereas Pacific saury feed mainly and selectively on N. cristatus in eastern areas, indicating a longitudinal difference in the trophic pathway from zooplankton prey to Pacific saury. These spatial differences in trophic pathways improve our understanding of nutritional intake in the commercially important Pacific saury during its feeding migration, and the effects this might have on fish size and weight, and associated commercial value. [ABSTRACT FROM AUTHOR]

Various research projects in Europe and North Africa have recently intended to breed temperate holothurians to alleviate fishing pressure on natural populations. However, to date little is known about the nutritional requirements of East Atlantic and Mediterranean species. In this study, we propose a "natural population"‐oriented approach to characterize food sources, digestive efficiency and resources allocation based on the composition of pigments and fatty acids (FA) in gut contents and tissues (muscles, gonads and digestive tract walls) of wild individuals of the species Holothuria (Panningothuria) forskali (Delle Chiaje, 1823) sampled in Brittany (France). Our study reveals that neither green nor red algae enter the diet of H. forskali in spring and that the only fresh vegetal material found in gut contents is brown algae (very likely diatoms). The high nutritional quality of gut contents however contrasts with the detrital nature of the ingested food sources, suggesting that a trophic upgrading of organic matter occurs before digestion. In addition, unusual FA (i.e. only present in a few groups of living species) such as long‐chain monounsaturated FA (especially the FA 23:1ω9) were found in large proportions in muscles and gonad and their effect on sea cucumber fitness needs further investigation. [ABSTRACT FROM AUTHOR]

Introduction: The benthic fauna of the littoral zone in lakes is important in transferring energy to other trophic levels, habitat coupling, and helping to keep habitat stability. The study of this type of interactions in lentic systems is priority, since functional aspects about biological communities are unknown. Objective: Describing the trophic relations of aquatic invertebrates of the littoral zone in a tropical high mountain lake by characterizing gut content and stable isotope analysis of δ13C and δ15N. Methods: Samples of benthic invertebrates were collected in the littoral zone of the Lago de Tota where Egeria densa was present using a handheld net method. Samples were processed in the laboratory, organisms were identified, counted and weighed. Gut contents and δ13C and δ15N stable isotopes analysis were performed as well. Results: Records of the trophic relations of aquatic invertebrates, which live in the littoral in high mountain lentic ecosystem in the Neotropics are shown. The analysis of gut contents distinguished seven food items, microphytes and MOPF were the most frequent, and through the stable isotopes analysis (δ15N) we identified four trophic levels, among resources (macrophytes and POM), and consumers (detritivores, herbivores, and predators). The two upper trophic levels concentrated greater diversity and biomass. Conclusion: Most of the organisms studied were linked to omnivorous habits, evidenced in a wide spectrum of food items in their diet. The δ15N values show an enrichment, which occurs due to the effects of the tendency towards eutrophication of the system or due to unknown values of protozoa and bacteria that plays a fundamental role in the diet of these organisms, besides the δ13C values reported in organisms consumes, allows us to suggest an affinity with native resources of the littoral zone. [ABSTRACT FROM AUTHOR]

Estimating changes in organic matter flow from resource to consumer using trophic basis of production (TBP) is a way to examine resource limitation effects on ecosystem function. We examined diet shifts and production of insect detritivores to assess changes with reduced detrital inputs to a forested headwater stream. Organic matter was excluded for 7 years using a canopy net. Small and large wood were removed from the stream after the 3rd and 5th year, respectively. Detritivore production declined after 3 years of litter exclusion. After wood removal, production of detritivores declined again. Steepest declines in Pycnopsyche gentilis production occurred within year 1. Tipula spp. and Tallaperla spp. production declined after wood removal. Diets shifted from leaves to wood to fine particulate organic matter (FPOM) for Tipula spp. and Tallaperla spp., but not for P. gentilis. Resource flows to detritivores shifted in the exclusion stream from leaves to wood to FPOM after leaf standing crops declined and wood removal. Small wood was an important food resource. TBP results showed shifts in food resource use by two detritivores with terrestrial input reduction. These findings suggest that maintaining diverse riparian inputs of organic matter is important for detritivore productivity in forested headwater watersheds. [ABSTRACT FROM AUTHOR]

The study aims to study the impact of the diet shift and feeding behavior of the paddlefish different age groups on the growth during the spawning season. Habitat affected paddlefish prey selection or foraging success is a striking force that promotes either dominance or submissiveness of brood fish to reproductive or growth performance under Russian aquaculture conditions. Four age groups were studied depending on years of commissioning (age composition: 23, 18, 17, 16; for years 1997, 2002, 2003 and 2004, respectively) and registered divergence in their growth rates throughout spawning season 2020. Growth patterns of 59 mature paddlefish were studied based on length-weight relationship, length frequency, and the growth coefficient (K). The results revealed that moderate growth pattern was observed in the 2nd group Isometric (b = 3), whereas the rest groups recorded negative allometric growth (b < 3). The data obtained from gut contents were consistent with the previous growth performance results. Major five prey categories (benthic macro-invertebrates, macro-invertebrate larvae, detritus, zooplankton and phytoplankton) were observed within fish stomach, which exposed through natural feeding in the rearing ponds. The values of chisquare test (χ²) results showed that frequencies in one or more prey items of a four age were strong significance (p-value = 8.93E-17 & χ² = 1.219, 1.051, 1.066 & 1.032; for 2nd, 3rd, 4th and 1st, respectively). Overall results propose maternal paddlefish prey election and growth patterns can be highly variable, and merely heavily reliant on feeding habitat and swimming behavior across spawning season. [ABSTRACT FROM AUTHOR]

The relative importance of allochthonous and autochthonous resources in fueling tropical headwater streams remains an open topic. We combined estimates of secondary production and assessment of its trophic basis to determine which resources were responsible for animal production. We studied benthic insect assemblages in two streams in the Luquillo Experimental Forest, Puerto Rico. Habitat-weighted production estimates were similar in both streams (528.5 and 591.5 mg m−2 year−1), but production was over twice as high in pool versus riffle habitats. The mayfly Neohagenulus (Leptophlebiidae) was a major contributor to total production (259.1 and 352.2 mg m−2 year−1). All taxa relied heavily on amorphous detritus and plant tissue. Aquatic insect production was similar to that reported for shrimp assemblages in the same study area, but low relative to temperate region estimates. The trophic basis of production appears to be allochthonous organic matter, which agrees with the small size and closed canopy cover over the study streams. This is the first study quantifying the production and trophic basis of the non-shrimp macroinvertebrate assemblage in tropical island streams. We also provide support for the importance of riparian vegetation as the main energy sources for stream tropical stream food webs. [ABSTRACT FROM AUTHOR]

Tardigrades may be divided into the following feeding groups: herbivores, carnivores and omnivores. However, little is known about their specific feeding preferences. Here, we used a number of laboratory experiments with 18 potential food sources, representing a wide variety of organisms, to test feeding preferences, survival and fecundity of three tardigrade species, representing different feeding modes. We also tested for differences in preferences between juveniles and adults, and differences in survival between two age groups: one that started the experiment as juveniles and the other as adults. In our experiments, Milnesium inceptum is confirmed to be a carnivore, being able to reproduce only on animal prey. We also show that Hypsibius exemplaris is a herbivore, feeding on cyanobacteria, algae and fungi. Paramacrobiotus fairbanksi , on the other hand, is demonstrated to be an omnivore, feeding on cyanobacteria, algae, fungi and animals. In some cases, juveniles preferred different types of food than adults. Reproduction was strongly affected by food type. Finally, we demonstrate that tardigrades may ingest food types that they are not able to digest. Thus, gut content analysis may be misleading as a method of studying tardigrade feeding habits. [ABSTRACT FROM AUTHOR]

Despite the high abundance of the gobiid fish Glossogobius callidus in many freshwater ecosystems in South Africa, very few studies have assessed the biology and ecology of the species. Here, we investigated the diet of G. callidus populations sourced from Sundays River irrigation ponds. A total of 571 fish grouped into two size classes (TL, range ± SD: juveniles of 20–60 ± 45 mm; adults of 61–140 ± 85 mm) were sampled by seine netting; prey items were removed from the guts and identified and sorted to obtain dietary information for each prey group. Of the examined guts, 97% contained prey comprising 17 taxa within 10 taxonomic groups. Teleosts were identified to species level, whereas most dietary components were identified to a broad taxonomic group. Aquatic invertebrates were the most important component of the diet of G. callidus, but the index of relative importance (%IRI) of dominant invertebrate taxa varied according to ontogenetic stage of G. callidus and season. Prey taxa included: Diptera, Hemiptera, Trichoptera, Odonata, Cladocera, Copepoda, Hydracarina, Amphipoda, Mollusca and Teleostei. Dipteran prey taxa were consistently encountered in both size classes and across all seasons. G. callidus can therefore be regarded as a generalist invertivore. [ABSTRACT FROM AUTHOR]

The morphology of the orobranchial structures in fish generally reflects the feeding habits and food preferences of a species and is key in understanding the process and habits of fish feeding. This work describes the orobranchial structures of four neotropical silversides (Teleostei: Atherinopsidae): the Mexican pike silverside Chirostoma estor, the Mexican blacknose silverside Chirostoma promelas, the Argentinian silverside Odontesthes bonariensis and Patagonian pejerrey Odontesthes hatcheri, and correlates their morphological features with existing information on gut contents and feeding habits in adult fish. Results of the compared and analysed data in the present study portray an integrative view of the specialised habits of the different species. Significant morphological differences, which are related to primary feeding habits of four species, were found. C. promelas shows to be more piscivorous compared to O. hatcheri, which has main benthic habits, while O. bonariensis and C. estor have more zooplanktivorous preferences. This information provides knowledge of feeding habits and ecological interactions of these species and their prey. [ABSTRACT FROM AUTHOR]

Background Feeding habits are central to animal ecology, but it is often difficult to characterize the diet of organisms that are arboreal, nocturnal, rare, or highly mobile. Genetic analysis of gut contents is a promising approach for expanding our understanding of animal feeding habits. Here, we adapt a laboratory protocol for extracting and sequencing plant material from gut contents and apply it to Neotropical forest katydids (Orthoptera: Tettigoniidae) on Barro Colorado Island (BCI) in Panama. Methods Our approach uses three chloroplast primer sets that were previously developed to identify vegetation on BCI. We describe the utility and success rate of each primer set. We then test whether there is a significant difference in the amplification and sequencing success of gut contents based on the size or sex of the katydid, the time of day that it was caught, and the color of the extracted gut contents. Results We find that there is a significant difference in sequencing success as a function of gut color. When extracts were yellow, green, or colorless the likelihood of successfully amplifying DNA ranged from ~30–60%. When gut extracts were red, orange, or brown, amplification success was exceptionally low (0–8%). Amplification success was also higher for smaller katydids and tended to be more successful in katydids that were captured earlier in the night. Strength of the amplified product was indicative of the likelihood of sequencing success, with strong bands having a high likelihood of success. By anticipating which samples are most likely to succeed, we provide information useful for estimating the number of katydids that need to be collected and minimizing the costs of purifying, amplifying, and sequencing samples that are unlikely to succeed. This approach makes it possible to understand the herbivory patterns of these trophically important katydids and can be applied more broadly to understand the diet of other tropical herbivores.

Macroinvertebrate grazers mainly feed on periphyton comprising of algae and detritus in streams, and sometimes feed on plant detritus or other invertebrates. We determined food habits of 21 grazer species (19 mayflies, 1 caddisfly, and 1 net-winged midge) from their gut contents, and systematically examined whether taxonomic affiliation, flow habitat, or body size are responsible for variations in food habits among or within the grazer species on a forested stream. We obtained some evidence that the food habits of grazer species varied according to family or genus; for example, species of Ephemerellidae ingested more animal materials. Species inhabiting slow-flow areas in riffles ingested fewer diatoms, while those inhabiting rapid-flow areas in riffles ingested less plant detritus. Larger individuals ingested more plant detritus or animal materials within a particular species (five grazer species), whereas we did not find the opposite patterns. Understanding the trophic roles of stream macroinvertebrates and the energy flow in stream food webs requires systematic exploration of the factors responsible for inter- and intraspecific variation. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate if aquatic pollution promote diet shifts in two livebearer fishes (Poeciliidae): an exotic species, the guppy (Poecilia reticulata), and a native livebearer (Phalloceros uai). The study was carried out in a Brazilian basin highly impacted by anthropogenic activities, especially discharge of domestic and industrial sewage from a region with more than five million human inhabitants. To evaluate the trophic ecology of both native and exotic species it was analysed carbon (δ13C) and nitrogen (δ15N) stable isotopes of fish tissue, food resources and, sewage. Moreover, stable isotopes analyses were coupled with gut contents of the two species to provide additional information about fish diet. Exotic guppy abundance was high in the most polluted site, where P. reticulata assimilated carbon directly from sewage. The native species was absent in the most polluted site, but presented wider niches than the exotic species in almost all other sites. Gut content analyses indicated high consumption of aquatic insects by both species. However, while the native species consumed a diverse suite of insect taxa, the exotic species consumed mainly Chironomidae larvae. We conclude that aquatic pollution promotes diet shifts in both native and exotic species, with both species changing their trophic niches in a similar way according to the level of degradation of the environment. The ability to directly assimilate sewage, together with its capacity to survive in environments with poor water quality and its reproductive strategy, may favour the establishment of exotic guppies in strongly polluted sites. Unlabelled Image • We tested the influence of pollution in the diet of exotic and native fish species. • We used gut contents and stable isotopes analysis to access the information. • Both species showed trophic plasticity and changed their trophic niches similarly. • Exotic species assimilated carbon directly from sewage. • Sewage consume can facilitate the exotic species establishment at polluted sites. [ABSTRACT FROM AUTHOR]

The fossil record of the family Corydalidae (Megaloptera) is rare with only six reported species and several undescribed larvae from the Middle Jurassic to Eocene. Little is known about the food habits and digestive system of ancient insects. We report the first corydalid larva preserved with gut contents from the Lower Cretaceous Yixian Formation of northeast China, examining the contents using a scanning electron microscope with energy dispersive X-ray analysis. The results show that the main component of the gut contents is quartz gastroliths ('stomach stones'), providing the first fossil evidence of a gastric mill promoting digestion in a megalopteran larva, extending the record of this behaviour to the Early Cretaceous. [ABSTRACT FROM AUTHOR]

We performed 16S rDNA sequencing of tilapia fecal samples to analyze changes in tilapia gut contents after cultivation of the fish in the presence of sandwich-like floating beds of Chinese medicinal herbs (5 and 10% planting-areas; 5% Polygonum cuspidatum). The interactive effects between water quality and blood and hepatic pro- and anti-inflammatory concentrations were also assessed. Our results showed that the water quality (i.e., NO 3 −-N, NO 2 −-N, TP removal rates) improved, and the abundance of Chloroflexi and Cyanobacteria increased. The abundance of Bacteroidetes, Verrucomicrobia, Saccharibacteria, and Actinobacteria showed both significant seasonal decreases and increases in the presence of P. cuspidatum (increases in August and decreases in July). Fish blood and hepatic IL-10 and IFN-γ levels (together with fish sampled in September) significantly increased in the P. cuspidatum group sampled in August, while those of TNF-α (10% sandwich-like, P. cuspidatum), IL-1β (P. cuspidatum), IL-8 (5% sandwich-like in September, S905S) significantly decreased. Heat shock proteins 60 and 70 levels significantly increased in the P. cuspidatum group, and complement C3 and C4 concentrations significantly increased in S905S. This study demonstrated that enhanced immunity through the regulation of pro- and anti-inflammatory proteins was sustained throughout development until harvest, particularly in fish grown with P. cuspidatum. • Planting with sandwich-like floating bed or Polygonum cuspidatum improved the water quality. • Chloroflexi and Cyanobacteria increased. • Bacteroidetes, Verrucomicrobia, Saccharibacteria and Actinobacteria decreased and increased with P. cuspidatum. • Blood and hepatic IL-10 and IFN-γ levels increased in S805P, TNF-α, IL-1β, IL-8 decreased. • Hsp60 and Hsp70 increased with P. cuspidatum , C3 and C4 increased in S905S. [ABSTRACT FROM AUTHOR]

Background: Feeding habits are central to animal ecology, but it is often difficult to characterize the diet of organisms that are arboreal, nocturnal, rare, or highly mobile. Genetic analysis of gut contents is a promising approach for expanding our understanding of animal feeding habits. Here, we adapt a laboratory protocol for extracting and sequencing plant material from gut contents and apply it to Neotropical forest katydids (Orthoptera: Tettigoniidae) on Barro Colorado Island (BCI) in Panama. Methods: Our approach uses three chloroplast primer sets that were previously developed to identify vegetation on BCI. We describe the utility and success rate of each primer set. We then test whether there is a significant difference in the amplification and sequencing success of gut contents based on the size or sex of the katydid, the time of day that it was caught, and the color of the extracted gut contents. Results: We find that there is a significant difference in sequencing success as a function of gut color. When extracts were yellow, green, or colorless the likelihood of successfully amplifying DNA ranged from ~30–60%. When gut extracts were red, orange, or brown, amplification success was exceptionally low (0–8%). Amplification success was also higher for smaller katydids and tended to be more successful in katydids that were captured earlier in the night. Strength of the amplified product was indicative of the likelihood of sequencing success, with strong bands having a high likelihood of success. By anticipating which samples are most likely to succeed, we provide information useful for estimating the number of katydids that need to be collected and minimizing the costs of purifying, amplifying, and sequencing samples that are unlikely to succeed. This approach makes it possible to understand the herbivory patterns of these trophically important katydids and can be applied more broadly to understand the diet of other tropical herbivores. [ABSTRACT FROM AUTHOR]

Larvae of many odonate species commonly appear within the same freshwater ecosystem. However, it remains unknown whether there is a dietary separation among the larvae of different species. In this study, we collected different species of odonate larvae in different seasons at various sites on the floating mat of Mizorogaike Pond in Kyoto, Japan, and examined the abundance and gut contents of the dominant species. Our analyses showed that habitat and seasonal abundance of the odonate larvae did not significantly overlap between most pairs of the dominant species. Moreover, the degree of dietary overlap was not related to larval biomass in microhabitats. These results suggest that, although larval food habits were similar among species, the existence of various vegetation types on the floating mat allowed many odonate species to inhabit Mizorogaike Pond. [ABSTRACT FROM AUTHOR]

We quantified the predation of Acanthocyclops americanus from the shallow Mediterranean lake Albufera, using gut contents from field collections and laboratory feeding tests. For functional response studies, we used Brachionus plicatilis (at 6 concentrations, 400-4000 ind. 40 ml−1) and Diaphanosoma mongolianum (at 2-20 ind. 40 ml−1). Copepod feeding rates were also estimated using different proportions of rotifer prey and lake seston (0-67.5% of seston + 40 individuals of B. plicatilis). Prey selection studies were conducted using five zooplankton species: Brachionus angularis, Brachionus plicatilis, Keratella tropica, Daphnia magna and Diaphanosoma mongolianum. Gut contents of field-collected adult Acanthocyclops contained filamentous algae and cyanobacteria and 16 zooplankton species (Keratella cochlearis, unspined and spined forms, K. tropica, Brachionus plicatilis, Brachionus calyciflorus, Brachionus angularis, Brachionus variabilis, Asplanchna girodi, Polyarthra vulgaris, Synchaeta pectinata, Lepadella rhomboides, unidentified bdelloids, Alona rectangula, Chydorus sphaericus, Bosmina longirostris, D. magna, Ceriodaphnia dubia and copepod nauplii). When fed B. plicatilis or D. mongolianum, female A. americanus had higher prey consumption rates than males. Increased proportion of lake seston caused reduced consumption of brachionid prey. Our data suggest that A. americanus is omnivorous in nature. [ABSTRACT FROM AUTHOR]