Differences In Feeding Ability Research Articles

Morphological divergences as drivers of diet segregation between two sympatric species of Serrapinnus (Characidae: Cheirodontinae) in macrophyte stands in a neotropical floodplain lake

Abstract Diet and morphology of Serrapinnus notomelas and Serrapinnus sp.1 were investigated across ontogeny, as a way to elucidate the key elements linked to the resource partitioning (a main driver for species coexistence). Fish sampling was conducted monthly between October 2010 and March 2012. Individuals were captured, identified, and classified into juvenile or adult. Our results show ontogenetic and interspecific differences in feeding abilities and morphological traits. Differences in body shape (relative area of the dorsal fin, length of head, height of the caudal peduncle, the aspect ratio of the pectoral and pelvic fin) favored divergent swimming performances (more maneuverability in S. notomelas and continuous swimming to Serrapinnus sp.1). We also observed divergences in trophic apparatus traits and correlations with different diets. In this context, it is highlighted that understanding the relationship between morphology and diet can assist in elucidating the processes that permeate the coexistence between sympatric species, and between ontogenetic periods. Besides, the relevant contribution of the measures of the trophic apparatus (gill raker length, the number of teeth cuspids, and intestinal coefficient) in trophic segregation seems to be a strong evidence in favor of the proposed discriminatory and predictive capacities of these traits.

Diet shifts by adult flightless dung beetles Circellium bacchus, revealed using DNA metabarcoding, reflect complex life histories.

Life history changes may change resource use. Such shifts are not well understood in the dung beetles, despite recognised differences in larval and adult feeding ability. We use the flightless dung beetle Circellium bacchus to explore such shifts, identifying dung sources of adults using DNA metabarcoding, and comparing these with published accounts of larval dung sources. C. bacchus is traditionally considered to specialise on the dung of large herbivores for both larval and adult feeding. We successfully extracted mammal DNA from 151 adult C. bacchus fecal samples, representing 16 mammal species (ranging from elephants to small rodents), many of which are hitherto undescribed in the diet. Adult C. bacchus showed clear dung source preferences, especially for large herbivores inhabiting dense-cover vegetation. Our approach also confirmed the presence of cryptic taxa in the study area, and we propose that this may be used for biodiversity survey and monitoring purposes. Murid rodent feces were the most commonly fed-upon dung source (77.5%) for adult C. bacchus, differing markedly from the large and megaherbivore dung sources used for larval rearing. These findings support the hypothesis of life history-specific shifts in resource use in dung beetles, and reveal a hitherto unsuspected, but ecologically important, role of these dung beetles in consuming rodent feces. The differences in feeding abilities of the larval and adult life history stages have profound consequences for their resource use and foraging strategies, and hence the ecological role of dung beetles. This principle and its ecological consequences should be explored in other scarabaeids.

Intraspecific food resource partitioning in Atlantic salmon ( Salmo salar) parr in a subarctic river

The food utilisation and partitioning between three age-groups of Atlantic salmon parr were studied in the subarctic river Tana (70° N, 27° E) by analysis of fish stomach contents and invertebrate composition in the three main lotic feeding habitats: bottom substratum, water column and surface. The salmon parr exhibited large seasonal variation in their food choice, but the different age-groups had a similar diet, dominated by mayfly and stonefly nymphs in May, flying insects and simuliid larvae and pupae in July, and caddis fly larvae in August and September. Some differences in the food resource use of the three age-groups were however also observed, mainly related to size-dependent differences in feeding abilities, but partly also to different use of feeding habitats. Small-sized stonefly and mayfly nymphs and simuliid larvae and pupae decreased in importance with increasing fish age, whereas Trichoptera larvae and flying insects increased. The low resource partitioning between the different age-groups of salmon parr suggests that intraspecific competition for food may occur. All age-groups mostly fed on prey types associated with the bottom habitat, and substantial drift feeding was only observed in July, probably due to low drift rates throughout most of the summer season in this subarctic river.

Experience and social environment influence the ability of young brown trout to forage on live novel prey

Efficient feeding is crucial for the growth, survival and reproductive success of most animals. In artificial-rearing environments, however, animals are deprived of many stimuli normally experienced in the wild, which may alter feeding behaviour, and thus influence their survival and reproductive success upon release in nature. In a laboratory experiment, we investigated the effect of hatchery rearing on the ability of brown trout, Salmo trutta, to capture and consume a novel live prey item. Hatchery-reared and wild-caught trout, originating from the same river, were fed single black crickets, either in isolation or in visual and olfactory contact with another hatchery-reared or wild-caught fish. Total consumption, time to first bite and feeding efficiency were monitored. Wild-caught trout ate more, were quicker to attack, and consumed attacked prey more efficiently than hatchery-reared fish. Food consumption and efficiency increased in both wild and hatchery-reared trout during the experiment. We propose that the differences in feeding ability between wild-caught and hatchery-reared brown trout were mainly due to differences in previous experience of feeding on live prey. Wild-caught trout tended to eat more and sooner when in visual contact with another fish than when in isolation. This trend was not seen for the hatchery-reared fish, which may be due to environmental differences between the hatchery and the natural stream. The initial inability of hatchery-reared fish to forage on live prey may reduce their success when released in the wild, especially when in competition with resident wild fish.

Differences in predation among morphotypes of the rotifer Asplanchna silvestrii

Summary1. Interactions were observed between three morphotypes of the predatory rotifer Asplanchna silvestrii and six different prey (Brachionus plicatilis, B. rotundiformis, B. pterodinoides, B. satanicus, Hexarthra jenkinae and copepod nauplii) to understand the differences in feeding abilities among morphotypes that may have led to the evolution of this predator polymorphism. The outcome of predation events was affected significantly, both by predator morphotype and prey type. Predator morphotypes also interacted differently with different prey types.2. The two smaller morphotypes, the saccate and the cruciform, responded similarly to prey overall, except that the smallest morphotype (saccate) was unable to ingest the most mobile prey (nauplii) and less able to ingest relatively large prey (B. plicatilis). The largest morphotype, the campanulate, had the highest encounter rate with prey, but the lowest probability of attack after encounter, so that it consumed far fewer prey per feeding bout than did the smaller morphotypes. This may have been because campanulates prefer larger prey than used in this study.3. Highly mobile prey (H. jenkinae and copepod nauplii) were much less susceptible to predation than the less mobile Brachionus species. While evasiveness reduced attacks by saccates and cruciforms, campanulates did not have a significantly lower attack rate on H. jenkinae and copepod nauplii than on less evasive prey. Large body size moderately defended B. plicatilis against ingestion by saccates only. The short‐spined B. satanicus was the only prey that was rejected after capture, resulting in lower ingestion probabilities for B. satanicus than other brachionid prey.

Serotonin depletion affects blood-feeding but not host-seeking ability in Aedes triseriatus (Diptera: Culicidae).

The host-seeking and blood-feeding abilities of Aedes triseriatus (Say) were evaluated after treatment with the amine depleting drugs alpha-methyl-tyrosine (AMT) and alpha-methyl-tryptophan (AMTP). High-performance liquid chromatography with electrochemical detection (HPLCED) was used to demonstrate that AMTP depleted serotonin levels, whereas AMT reduced dopamine levels. The host-seeking ability (evaluated with an olfactometer) of Ae. triseriatus was not altered by treatment with either AMT or AMTP. Blood-feeding success was reduced significantly by either oral administration or injection of AMTP. Mosquitoes treated with AMTP responded positively when placed in close proximity to a host (rabbit), but fewer treated than untreated mosquitoes fed to repletion or fed at all. Those feeding to repletion took longer to do so. No differences in feeding ability were observed between control and AMT-treated mosquitoes. These observations indicate that serotonin plays a role in modulating blood-feeding activities of Ae. triseriatus.

Body Size and the Ontogeny of the Functional Response in Fishes

The development of foraging abilities is crucial to the survival and subsequent recruitment of young fishes. We examined experimentally the notion that the foraging abilities of species are so different that useful generalizations across taxa are impossible. We investigated the ontogeny of feeding, reflected in their functional responses, in three Great Lakes' fishes, alewife (Alosa pseudoharengus), yellow perch (Perca flavescens), and bloater (Coregonus hoyi). No strong evidence of species-specific differences in the ontogeny of feeding ability was found. A single size-based relationship explained 52–88% of the variation in the parameters of the functional response equation. We conclude that interspecific differences in feeding abilities of larval fishes may have been overemphasized, and we suggest that interspecific differences should only be addressed within a size-based framework. This approach appears to provide an acceptable basis for first-order predictions of foraging abilities across taxa, for the identification of exceptional abilities which may lead to advances in the understanding of foraging ability, and for estimating foraging rates for important species for which data are now lacking.