Generalist Feeding Research Articles

‛Trophic switch' by catfish community from predation to scavenging modulated by human food discard in an estuarine bay.

Benthic predatory catfishes are voracious and opportunistic predators and can easily shift their diet according to the availability of prey. In this study, feeding ecology of catfishes from two adjacent habitats of an estuarine bay is compared. The lower bay was relatively pristine as compared to the upper bay and was represented by two families of catfishes-Plotosidae and Ariidae, while the upper bay represented only ariid catfishes. Gut content analysis revealed that catfish predators from lower bay consumed conventional prey like teleosts and benthic invertebrates with a linear pattern of ontogenetic dietary shift. Plicofollis dussumieri and Plotosus canius occupied the position of top predators in the lower bay and were specialized feeders. Other predators like Plotosus lineatus, Arius arius, Arius jella, and Arius maculatus were generalist feeders occupying the position of mesopredators. However, in the upper bay, the catfish predators represented by Arius maculatus, Arius jella, and Arius arius predominantly fed on human discarded food. The easily available human food in the form of chicken, corn, and rice as noted from the investigated guts shows altered trophic guilds of ariid catfishes wherein only mid to large-sized catfish community was noted in this bay. A distinct "trophic switch" altered the trophic function from predation to scavenging which was observed in their feeding behavior. The anthropogenic impact in the form of unmanaged organic waste alters the role of predatory catfishes thereby restructuring the food web that may lead to unknown changes in the estuarine benthic ecosystems resulting in reduced ecosystem services.

A novel feeding platform design for behavioral research on wild Tanimbar corellas (Cacatua goffiniana)

The study of animal behaviour and cognition would not be complete without investigations of wild, free-ranging individuals in their natural environment. However, direct observations of species living in dense habitats can be challenging, leading many studies to focus on attracting target species to pre-selected, monitored locations baited with food. So far, researchers have rarely applied this approach to studying wild psittacines – an avian group of high scientific interest due to their advanced cognitive skills and conservation threats. We developed hoistable feeding platforms and tested their suitability for reliably attracting groups of wild Tanimbar corellas (hereafter: Goffins), opportunistic feeding generalists well-known for their advanced cognitive skills. To this end, we recorded the visitation rates of free-ranging groups at feeding platforms temporarily baited with dry corn. Moreover, we investigated the effects of several weather-related measures, the temporal distribution of foraging activity, and the effect of conspecific contact calls (playback stimulus). The results indicate that Goffins accepted the feeding platforms and reliably aggregated within their natural daily foraging bouts. While group size during visitation bouts depended on rainfall and resource abundance, platforms were still regularly visited by fewer, possibly locally residing individuals. These results provide the first systematic investigation of the temporal distribution and social dynamics of foraging bouts in wild Goffins. This study presents a novel method for reliably attracting wild opportunistic feeding generalist psittacines to a standardised, monitored location. It provides a suitable approach for observing foraging aggregations and, in the future, testing the problem-solving abilities of free-ranging Goffins in their natural habitat.

Diet composition and feeding habits of yellowfin tuna Thunnus albacares (Bonnaterre, 1788) from the Bay of Bengal

Though yellowfin tuna (Thunnus albacares) is one of the important fishery resources in the Bay of Bengal, knowledge on its ecology, diet composition and feeding habits are limited from this area. In view of that, present study focuses on the diet composition and feeding habits of yellowfin tuna (YFT) hooked during exploratory longline survey conducted in the Indian EEZ of the Bay of Bengal during 2019–2021. A total of 213 specimens in the length range of 42.0 to 171.0 cm fork length (FL) were examined, of which 28.2% were empty while the remaining 71.8% contained at least one prey item. The modified Costello graphical method shows a wide range of prey items, with a few prey species that are dominant and can be found in high densities in the Bay of Bengal. Due to the fact that this apex predator is a generalist feeder, this might be the case. Cluster analysis based on the %IRI (Index of relative importance) identified two size groups. YFT with smaller (<80 cm FL) is one group. Crustaceans was the most frequently eaten prey in that group followed by cephalopods and teleostea. The second group consists of two length groups medium (81–120 FL), and larger (>120 FL), Cephalopods were the dominant prey items of this group and accounts for 62.0% in %IRI followed by teleostea 31.3% of the diet. Cephalopods (Sthenoteuthis oualaniensis) were the primary food consumed in all the size groups, followed by crustaceans (Charybdis smithii) and Teleost fishes (Cubiceps pauciradiatus). The dietary breadth and the occurrence of empty stomachs were significantly related to size of the yellowfin tuna. With increasing body size, diet breadth gradually increased while the percentage of empty stomachs declined. The yellowfin tuna diet does not vary significantly during the seasons. However, cephalopods were found in 53.5% of the IRI in their diet. Furthermore, there were notable seasonal changes in the percentage of empty stomachs, with the highest percentage observed during the monsoon season (38.3%).

Fish trophic network in karst streams from Brazilian Pantanal headwaters

Abstract Trophic interactions have been a long-standing field of interest in ecology, helping to understand the relationships between organisms and how ecosystems function. In this study, we describe the trophic relationships of fish from karst environments in headwater streams of the upper Paraguai River basin. We analyzed the stomach contents of 81 fish species from the Serra da Bodoquena, calculated the metrics associated with the trophic network, incorporating the body size component in the analyses, and evaluated the participation of each species in network/module connectivity. The analyzed community trophic organization was based mainly on autochthonous items which were the most consumed items for about 30% of fish species. The trophic network showed a modular pattern without nestedness or specialization. However, nestedness was significant within each module, demonstrating a hierarchical compound topology (i.e., species with few connections interacted with subsets of the pairs of more connected species within each module). We also found a relationship between network connectivity and fish body size, in which small species tend to connect modules through generalist feeding strategies. Thus, we demonstrated a still little-known role of small species in fish trophic networks, and how trophic segregation occurs in a highly diverse community from Pantanal headwater streams.

Sea Turtle Eggs and Hatchlings are a Seasonally Important Food Source for the Generalist Feeding Golden Ghost Crab (Ocypode convexa)

Sea Turtle Eggs and Hatchlings are a Seasonally Important Food Source for the Generalist Feeding Golden Ghost Crab (Ocypode convexa)

High microplastic and anthropogenic particle contamination in the gastrointestinal tracts of tiger sharks (Galeocerdo cuvier) caught in the western North Atlantic Ocean

Few studies have documented microplastics (<5 mm) in shark gastrointestinal (GI) tracts. Here, we report microplastic contamination in the tiger shark (Galeocerdo cuvier), an apex predator and generalist feeder, at several different life stages. We examined seven stomachs and one spiral valve from eight individuals captured off the United States Atlantic and Gulf of Mexico coasts (eastern US) and conducted a literature review of publications reporting anthropogenic debris ingestion in elasmobranchs. Specimens were chemically digested in potassium hydroxide (KOH) and density separated using calcium chloride (CaCl2) before quantifying and categorizing suspected anthropogenic particles (>45 μm) by size, morphology, and colour. Anthropogenic particles were found in the stomachs and spiral valve of all sharks. A total of 3151 anthropogenic particles were observed across all stomachs with 1603 anthropogenic particles observed in a single specimen. A subset of suspected anthropogenic particles (14%) were chemically identified using Raman spectroscopy and μ-Fourier Transform Infrared spectroscopy to confirm anthropogenic origin. Overall, ≥95% of particles analyzed via spectroscopy were confirmed anthropogenic, with 45% confirmed as microplastics. Of the microplastics, polypropylene (32%) was the most common polymer. Diverse microparticle morphologies were found, with fragments (57%) and fibers (41%) most frequently observed. The high occurrence and abundance of anthropogenic particle contamination in tiger sharks is likely due to their generalist feeding strategy and high trophic position compared to other marine species. The literature review resulted in 32 studies published through 2022. Several methodologies were employed, and varying amounts of contamination were reported, but none reported contamination as high as detected in our study. Anthropogenic particle ingestion studies should continue in the tiger shark, in addition to other elasmobranch species, to further understand the effects of anthropogenic activities and associated pollution on these predators.

The influence of diet on gut microbiome and body mass dynamics in a capital-breeding migratory bird.

Gut-associated microbial communities are known to play a vital role in the health and fitness of their hosts. Though studies investigating the factors associated with among-individual variation in microbiome structure in wild animal species are increasing, knowledge of this variation at the individual level is scarce, despite the clear link between microbiome and nutritional status uncovered in humans and model organisms. Here, we combine detailed observational data on life history and foraging preference with 16S rRNA profiling of the faecal microbiome to investigate the relationship between diet, microbiome stability and rates of body mass gain in a migratory capital-breeding bird, the light-bellied Brent goose (Branta bernicla hrota). Our findings suggest that generalist feeders have microbiomes that are intermediate in diversity and composition between two foraging specialisms, and also show higher within-individual plasticity. We also suggest a link between foraging phenotype and the rates of mass gain during the spring staging of a capital breeder. This study offers rare insight into individual-level temporal dynamics of the gut microbiome of a wild host. Further work is needed to uncover the functional link between individual dietary choices, gut microbiome structure and stability, and the implications this has for the reproductive success of this capital breeder.

Borrowing from the palaeolimnologists toolkit; the use of lake sediment cores in diagnosing the causes of freshwater species decline

Populations of freshwater species are experiencing dramatic declines globally. Tools that facilitate the diagnosis of decline and identify management solutions and/or restoration targets are thus vital. Typically approaches taken to diagnose decline are carried out over short timescales and rely upon identifying spatial associations between presence or abundance of declining species and variables hypothesised to be driving decline. The potential to contextualise observed declines on longer time scales, with a broader range of potential explanatory variables is frequently dismissed, because of a perceived lack of existing long-term data. In this study we explore the value of incorporating a longer-term perspective to decline diagnosis using the common scoter as a case study. The number of scoter breeding in Scotland has declined substantially since the 1970s. Hypotheses for decline include a reduction in macroinvertebrate food available for females and young at the breeding lakes. In this study we apply palaeolimnological techniques to generate standardised, long-term ecological data, enabling us to characterise recent changes at four common scoter breeding lakes. Our results demonstrate that the (macroinvertebrate) food resource of common scoter has, in fact, gradually increased in abundance at all four sites from ca. 1900, and that a further statistically significant increase in macroinvertebrate abundance occurred at ca. 1970. We draw on our palaeolimnological data, to explore alternative hypotheses for common scoter decline. Increases in overall abundance across multiple algal, macrophyte and macroinvertebrate taxa, combined with specific increases in nutrient tolerant taxa, and concurrent declines in nutrient sensitive taxa indicate that the lakes have experienced enrichment within their current oligotrophic state during the last 100 years, and that this trajectory has become more marked during the period of common scoter decline. There is no evidence of changes to habitat, turbidity or increased competition from fish. In the absence of within lake changes that could be detrimental to the benthic (and generalist) feeding common scoter, we conclude that factors outside of the lake, such as increased predation, associated with afforestation in the surrounding area, are the most plausible drivers of common scoter decline. Prioritisation/testing of management solutions that address these issues are indicated.

Double trouble: Leptodactylus latrans (Anura: Leptodactylidae) as prey of two Erythrolamprus miliaris (Serpentes: Dipsadidae)

Erythrolamprus miliaris is a Neotropical aglyph snake with a generalist feeding habit. We report herein the first observed instance of simultaneous predation on an adult Leptodactylus latrans by two adult individuals of E. miliaris. Although the ultimate outcome remains unknown, this report underscores the importance of comprehensive documentation in understanding predator-prey relationships and ecological dynamics in urban areas.

ANTI-APOSTATIC FEEDING BEHAVIOR IN TWO SPECIES OF ASSASSIN BUG, THE WHITE-SPOTTED ASSASSIN BUG PLATYMERIS BIGUTTATUS AND RED-SPOTTED ASSASSIN BUG PLATYMERIS RHADAMANTHUS (HEMIPTERA: REDUVIIDAE)

Abstract Predator-prey relationships are a driving force when examining community ecology. One question in predator-prey interactions is how a predator may respond to novel prey phenotypes, a form of frequency dependent prey selection. A predator may selectively target or avoid the novel prey, a behavior referred to as anti-apostatic or apostatic selection respectively. We examined apostatic prey selection by observing feeding behavior in two species of assassin bugs (Hemiptera: Reduviidae), the white-spotted assassin bug (Platymeris biguttatus) and the red-spotted assassin bug (Platymeris rhadamanthus) which were fed unmodified and modified (novel) phenotypes of Turkistan cockroaches, Blatta lateralis (Blattodea: Blattidae). The two species of assassin bugs represent either generalist (P. biguttatus) or specific feeders (P. rhadamanthus). We hypothesized that the generalist feeder would engage in anti-apostatic feeding while the specific feeder would engage in apostatic feeding. Our results indicated that there was no difference in feeding behavior between the two species, however an overall trend of apostatic feeding was observed in response to two of the four novel prey phenotypes. Factors beyond prey phenotype may also be influencing feeding choice in these insects. While the two predator species did not exhibit different feeding behaviors, the observation of apostatic feeding in this genus suggest an overall trend of utilizing specific prey images in feeding.

Feeding ecology of the African cuttlefish Sepia bertheloti (Cephalopoda: Sepiidae) in western Africa

The African cuttlefish, Sepia bertheloti, is a commercially exploited cephalopod in two productive system areas off West Africa. However, there is a lack of information on its feeding ecology, making it difficult to describe its ecological role (Morocco and Guinea-Bissau). In the present study, we analyse the gastric contents of 1.114 individuals, collected between July 2018 and January 2020 using the traditional analysis of stomach contents. A total of 65 and 49 prey items were identified as part of the diet of Moroccan and Guinean African cuttlefish, respectively. The sample size was evaluated using species cumulative curves and the methods used to describe the diet were the frequency of occurrence, number, and weight. Our results suggest that S. bertheloti does not present differences in diet between sexes or areas, although significant differences were observed in terms of prey abundance, richness, and diversity of species. According to the taxonomic groups, crustaceans were the most abundant prey taxa, followed by fish and cephalopods. Amphipods (Gammarus sp.) were the prey that showed the greater importance of occurrence in the diet at both study areas, showing a strictly benthic feeding behaviour. Niche breadth was evaluated using Levin’s index, indicating that S. bertheloti is an omnivorous species (Trophic level ∼3.6) with a heterogeneous diet and without a marked generalist or specialist feeding strategy.

Triatominae (Hemiptera: Reduviidae) fauna in bird nests: the case of Morrinhos, Ceará, Brazil.

Triatominae are associated with various Brazilian habitats, including bird nests, animal burrows, and peridomestic structures. Despite extensive studies on triatomines in domiciliary environments in Ceará, Brazil, there has been limited research on their presence in the wild. This study focuses on the municipality of Morrinhos in Ceará, which is characterized by a Caatinga biome and riparian forests along the Acaraú River. During the study, a total of 185 nests of Pseudoseisura cristata were analyzed in rural locations and triatomines were collected in 26 nests from 12 different locations. A total of 117 triatomines was collected, belonging to three species: Psammolestes tertius, Rhodnius nasutus, and Triatoma pseudomaculata. Rhodnius nasutus was the only species found in a nest inhabited by Didelphis albiventris. Nests of P. cristata serve as shelters for various animals, providing an ideal environment for triatomines to establish colonies due to their proximity to food sources and their generalist feeding habits. The incorporation of anthropogenic materials by birds in nest construction can indirectly affect the presence of other animals that may serve as food sources for triatomines. Understanding the interactions between triatomines, birds, and their habitats is essential for assessing the risks associated with triatomine infestation in wild ecosystems.

Functional and temporal facets of predation by marsh frogs across the aquatic–terrestrial ecotone of ponds and implications in the context of biological invasions

Abstract Freshwater vertebrate predators can exert trophic control over aquatic and littoral communities. Among these predators, post‐metamorphic anurans exhibit a biphasic trophic spectrum by foraging in both terrestrial and aquatic habitats. Many studies have described their diet through the classical taxonomic classification of prey. However, these singular diet habits imply a complex, time‐dependent, realised trophic niche in which predation pressure occurs over many consumers that fill diverse functional roles throughout the aquatic and terrestrial interface of ponds. Among anurans, marsh frogs (Pelophylax ridibundus) have been introduced outside their range in many countries and are now invading nationwide areas, particularly in western Europe. Focusing on their foraging specificities will therefore further the understanding of the trophic role of these alien taxa in pond environments that are highly colonised. We collected stomach contents from 761 marsh frogs from introduced populations in 19 ponds in southern France once a month over 4 months of their active period in the spring. The populations of marsh frogs were studied in a geographic area that was devoid of native water frogs and their origin tracks back as far as south‐eastern Europe (i.e., more than 1,000 km from the studied sites, as evidenced previously by genetic analyses). Marsh frogs exhibited generalist and opportunistic feeding strategies. The trophic niche was strongly asymmetrical and broader in the terrestrial environment than in the aquatic environment. However, predation occurred in communities of large freshwater macroinvertebrates and amphibians. Whereas the composition of the terrestrial diet exhibited strong seasonal variations, predation pressure was continuously exerted on the same aquatic organisms over time. Primary consumers and consumers at higher trophic levels frequenting aquatic benthic, vegetated, pelagic, and surface microhabitats were preyed upon, underlying the multidimensional extent of the predation spectrum. The diversified feeding strategies of alien marsh frogs highlight the extent of potential ecological control by predation on pond communities. Because of their wide trophic niche, they exert predation pressure on most pond organisms, triggering possible top‐down control of the overall aquatic communities. Our results show that the integration of the functional traits and microhabitats of consumed prey may aid in a better understanding of how predation by anurans may target specific components of pond communities. More particularly, this study raises concerns about the predatory role of introduced anurans in the context of biological invasions.

Insights into Ontogenetic Niche Changes in Bluegill, Lepomis macrochirus, Applying Combined Analyses of Stomach Content and Stable Isotopes

We integrated stomach content analysis (SCA) and stable isotope analysis (SIA) to understand ontogenetic niche shifts in the invasive freshwater fish, bluegill, Lepomis macrochirus, inhabiting the Yedang Reservoir in Korea. Based on the total length (TL), we classified L. macrochirus as small (23–57 mm), medium (61–99 mm), or large (100–163 mm). Across all study sites, the index of relative importance (IRI) of zooplankton was high for small individuals, whereas those of benthic macroinvertebrates were high for the medium and large groups. Isotopic niche width estimates based on carbon and nitrogen isotope ratios (δ space) also increased with growth, indicating an ontogenetic niche shift in L. macrochirus. In particular, the δ space and diet plasticity of large fish was higher in the littoral population, implying L. macrochirus are generalist feeders as adults. Individuals classified as small showed confined and constant δ space, regardless of habitat condition. Thus, together with the results on the significantly high IRI of zooplankton, these individuals seem to have strong specialistic feeding ecology. Our study demonstrates the applicability strength of combining SCA and SIA for ecological niche research by providing clear evidence of an ontogenetic niche shift in L. macrochirus and elucidates their feeding ecology.

Common but not connected: high genetic structure and cryptic genetic diversity in the ubiquitous biting midge Culicoides peregrinus Kieffer.

The biting midge Culicoides peregrinus Kieffer is a significant pest and vector species, and knowledge of its genetic diversity and genetic structure is critically important for designing an effective control program. However, such information is limited to only small sample-size DNA barcoding studies. Therefore, in this study, we used mitochondrial cytochrome c oxidase I (COI) to examine genetic structure and diversity of C. peregrinus from northeastern Thailand. In addition, we also inferred genetic relationships between C. peregrinus from Thailand and those reported from other countries across the geographic range of the species. Maximum intraspecific genetic divergence (3.83%) within Thai specimens was relatively high compared to other Culicoides species. Genetic structure analysis revealed that 71% (32 from 45) of population comparisons were highly significantly different. A high level of genetic structure among populations, even between those in close geographic proximity (22 km geographic distance) suggested that there has been little or no movement between local populations. This is possibly due to the ability to exploit diverse types of breeding site and a generalist feeding habit which enables C. peregrinus to complete its life cycle within cattle pens. Genetic relationships between Thai C. peregrinus and those reported from other countries revealed three genetically divergent lineages (A, B and C) associated with geographic origins. Specimens from Thailand + China formed lineage A, those from Australia formed lineage B and India + Bangladesh belonged to lineage C. These genetically divergent lineages also agree with morphological variation of the wing pale marking spots. Further investigation using independent genetic loci from nuclear genes will be very useful to resolve taxonomic status of these divergent lineages.

Marine diets of anadromous Arctic char (Salvelinus alpinus) and pink salmon (Oncorhynchus gorbuscha) in Svalbard, Norway

During summer, native anadromous Arctic char (Salvelinus alpinus) and the alien species pink salmon (Oncorhynchus gorbuscha) now coexist in marine environments in Svalbard, following the introduction of the latter in the Barents Region. To investigate potential dietary competition between these two salmonid species, stomach contents from Arctic char (n = 301) and pink salmon (n = 28) were sampled from different areas within the archipelago. The most important prey in terms of biomass for both salmonid species were amphipods; Themisto libellula (B = 26.0%) for Arctic char and Onisimus litoralis (B = 35.0%) for pink salmon. Pianka’s niche overlap revealed that dietary overlap between the two species was moderately high (Oobs = 0.59); both species had strong associations with intertidal invertebrates in areas where direct comparisons were possible (Kongsfjorden/Krossfjorden). However, both salmonid species did also eat some fish, with Arctic char consuming more offshore pelagic fish, while the small number of fish eaten by pink salmon were primarily coastal demersal fish species. Arctic char was a more generalist feeder, while pink salmon was more of a dietary specialist. Furthermore, the diet composition of the Arctic char consisted of 32.9% Atlantic prey while the pink salmon, surprisingly, ate only Arctic species, likely due to their tightly coastal feeding habits. Even though the sample size for pink salmon was low, this study contributes new insights into salmonid diets in Svalbard and the potential for introduced species to compete with native Arctic endemics, particularly in the expected warmer Arctic of the future.

Golf course living leads to a diet shift for American alligators.

Human-driven land use change can fundamentally alter ecological communities, especially the diversity and abundance of large-bodied predators. Yet, despite the important roles large-bodied predators play in structuring communities through feeding, there have been only a few investigations of how the feeding patterns of large-bodied predators change in human-dominated landscapes. One group of large-bodied predators that has been largely overlooked in the context of land use change is the crocodilians. To help fill these gaps, we studied the feeding patterns of juvenile American alligators (Alligator mississippiensis) on neighboring barrier islands on the southeast coast of Georgia, USA. Jekyll Island has multiple golf courses and substantial amounts of human activity, while Sapelo Island does not have any golf courses and a much smaller amount of human activity. We found that juvenile alligator populations on both islands ate the same types of prey but in vastly different quantities. Sapelo Island alligators primarily consumed crustaceans while alligators that lived on Jekyll Island's golf courses ate mostly insects/arachnids. Furthermore, the Jekyll Island alligators exhibited a much more generalist feeding pattern (individuals mostly ate the same types of prey in the same quantities) than the more specialized Sapelo Island alligators (diets were more varied across individuals). The most likely explanation for our results is that alligators living on golf courses have different habitat use patterns and have access to different prey communities relative to alligators in more natural habitats. Thus, land use change can strongly alter the feeding patterns of large-bodied predators and, as a result, may affect their body condition, exposure to human-made chemicals, and role within ecological communities.

The shark and ray teeth of the Lower Miocene (Upper Marine Molasse) from Ballendorf, Baden-Württemberg, Southern Germany

In an abandoned sand pit near Ballendorf (Alb-Donau District, Baden-Württemberg), sediments of the Upper Marine Molasse (Lower Miocene) are present. In these sediments, 39 shark and ray species belonging to 29 genera were identified (Aetobatus, Alopias, Araloselachus, Carcharhinus, Carcharias, Centrophorus, Chaenogaleus, Dasyatis, Galeocerdo, Hemipristis, Iago, Isistius, Keasius, Notorynchus, Pachyscyllium, Paragaleus, Physogaleus, Pristiophorus, Raja, Rhinobatos, Rhinoptera, Rhizoprionodon, Rhynchobatus, Scyliorhinus, Sphyrna, Squalus, Squatina, Taeniurops, Triakis). However, in this paper we only illustrate and describe the 23 taxa not already discussed in previous publications on the Upper Marine Molasse deposits of Äpfingen, Rengetsweiler and Ursendorf, apart from two exceptions: teeth from jaw positions not previously illustrated, and specimens that are better preserved than those in previous publications. Specimens only determined as “sp.” were illustrated because it cannot be ruled out that they represent different species to the ones published earlier. Nearly all of the taxa found have Recent relatives; only Araloselachus, Keasius and Physogaleus are extinct. Most of the recovered taxa lived on or near the bottom in the shelf region. Alopias and possibly also Keasius lived higher in the water column. With Isistius, a taxon living in the oceanic realm was present, and the Recent representatives of Centrophorus live in deeper waters. Nearly all taxa fed on invertebrates and/or fishes; Isistius also fed as an ectoparasite. Additionally, two generalist feeders (Galeocerdo, Notorynchus) and one filter feeder (Keasius) were identified. The species Carcharias crassidens, which is not common in the Upper Marine Molasse, was also verified. Other fossils found in this deposit include remnants of odontocete cetaceans, molluscs, balanid barnacles, algae, and teeth of terrestrial mammals. The palaeoenvironment was a warm, shallow-water habitat. Based on greater proximity to the palaeo-coastline, the water depth was probably less than in other Upper Marine Molasse deposits.

Risk assessment of microplastics in fish assemblage based on ecological preferences in an interconnected and polluted river system

Risk assessment of microplastics (MPs) contamination in the assemblage of 15 important fish species with different feeding habits and microhabitats was studied in the River Ravi, Pakistan. Fishes with different feeding habits (omnivore, herbivore, and carnivore) and microhabitat preferences (surface, column, and bottom dweller) were sampled at Balloki and Sidhnai barrages during the post-monsoon seasons of 2019–2020. The gastrointestinal tract (GIT) of fish samples were found to be contaminated with MPs, with an average of 28.1 ± 20.7 MPs/individual and 26.8 ± 15.9 MPs/individual at Balloki and Sidhnai barrages, respectively. The surface dweller fish exhibited the highest MPs abundance, followed by the bottom dweller and column dweller. In addition, the highest MPs recovered from the omnivore generalist feeding group as compared to herbivores and carnivores. The fibers were the most abundant shape and generally made up of polyethylene terephthalate (PET) and polyethylene (PE). These PET and PE (low-density MPs) exhibit low hazard level, whereas high-density MPs with high hazard level and rarely present in GIT of sampled fishes. Based on MP polymer toxicity assessment, nine fish species were categorized in minor risk, two species in medium risk, and four species in highrisk group. Bottom dwelling fishes were at the highest plastic polymer risk level III due to the presence of a high density of MPs with high toxicity hazards. The high-risk prone fishes are under direct threat from MPs pollution, which may disrupt the ecological integrity of the river ecosystem and human health. The findings of the current study highlight the urgent need to address plastic pollution issues in River Ravi, and will be helpful for managers, researchers, and fisheries experts to mitigate this emerging challenge.speciesspecies

Trophic ecology of common bottlenose dolphins in a pelagic insular environment inferred by stable isotopes

The common bottlenose dolphin (Tursiops truncatus) is a top marine predator widely dispersed in coastal and pelagic habitats and with a generalist feeding behavior. Yet, information on the trophic ecology of animals inhabiting pelagic environments is still scarce. Using carbon (δ13C: 13C/12C) and nitrogen (δ15N: 15N/14N) stable isotope ratios, we identified and quantified the main groups of prey assimilated by bottlenose dolphins inhabiting an oceanic habitat (Madeira Island, East Atlantic). Bottlenose dolphins assimilated pelagic, schooling fish (such as blue jack mackerel, Trachurus picturatus) and mesopelagic and demersal squids, which reinforces the pelagic dietary composition of insular/oceanic dolphins. Also, intra-seasonal differences were found in their stable isotope ratios, which suggest intraspecific variability in the feeding behavior among individuals living in the same area. Sex was not the main factor contributing to these differences, suggesting the lack of trophic niche segregation between adult males and females in this offshore environment. Nonetheless, further studies including different life stages and information on the ecophysiological requirements are necessary to disclose the factors responsible for the observed variability. This study showed that insular dolphins fed primarily on economically important pelagic prey, highlighting the need of developing management strategies that integrate conservation in fisheries plans.