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At least 307 records · Page 17Linked to original sources
PubMed1999

Phytosterol metabolism and absorption in the generalist grasshopper, Schistocerca americana (Orthoptera: Acrididae).

A series of experiments, using GLC, RP-HPLC, and GC-MS techniques, were performed to examine the metabolic fate and absorption of different dietary sterols in the grasshopper Schistocerca americana. In the first experiment, grasshoppers were reared on diets containing different sterols presented singly. Cholesterol was the dominant tissue sterol recovered from cholesterol and "soybean sitosterol" fed grasshoppers but among the grasshoppers fed diets with stigmasterol and spinach sterols (both unsuitable for growth and development), the amount of cholesterol recovered was not different from that of newly hatched grasshoppers. In the second experiment, grasshoppers were given diets containing mixtures of soybean sitosterol and stigmasterol and the metabolic fate of these dietary sterols was recorded. Results from this experiment suggest that the presence of an unsuitable dietary sterol does not interfere with cholesterol production from sitosterol. They also demonstrate that large quantities of unmetabolized dietary sterols with C-24 ethyl groups are recovered from grasshoppers fed diets containing stigmasterol. Finally, tissue sterol profiles of grasshoppers with and without their midguts were compared. Results suggest that the midgut is the major tissue where unmetabolized dietary sterols accumulate. How these sterol metabolic constraints impact development and survival is discussed as well as the impact they might have on grasshopper feeding behavior. Arch.

Absorption↗
PubMed1992

Morphological and behavioral adaptations for foraging in generalist primates: the case of the cebines.

In addition to being frugivorous, Cebus and Saimiri stand out among the New World primates of similar body size in being heavily dependent on animal matter for protein (faunivory). A detailed description of the morphology and behavior of the two genera is presented with the object of evaluating the interaction and respective contributions of morphological and behavioral adaptations to foraging patterns. Our conclusions include the following: First, body size is extremely important in explaining the observed variation in diet. Second, the emphasis on faunivory is facilitated more by behavioral than by morphological specialization. Third, whatever morphological specializations are present, particularly in Cebus, are probably favored by diet at the most food-depauperate time of year. Fourth, although morphology may well reveal what a primate may potentially eat, to map this potential onto actual diet requires a detailed knowledge of its natural ecosystem. Finally, we consider whether the behavioral data support the tenuous morphological evidence for grouping Cebus and Saimiri within the clade Cebinae.

Adaptation, Physiological↗
PubMed2026

Population Genomics Approaches Identify a Cryptic, Emerging Generalist Pest Complex.

Information about biological traits essential for pest management, such as species identity, diet and movement often require laborious and time-intensive studies on pest natural history, in both laboratory and field settings. However, new agricultural pest threats are continually emerging, often requiring prompt responses with limited information. Using a combination of molecular gut content analysis and RAD-seq, we examined the species identities, plant diet composition, and population genetic structure of an emerging and important agricultural pest in the US, the peanut burrower bug, Pangaeus bilineatus Say (Hemiptera, Cydnidae). We found that two, morphologically similar, burrowing bug species (including P. bilineatus) were commonly caught in light traps near peanut fields, one of which (Dallasiellus lugubris) was not previously considered a pest of peanut. Molecular gut content analysis revealed a wide, but somewhat distinct, variety of plants among the diets of both bug species. Surprisingly, peanut was a rare part of the diet of either species. RAD-seq analysis revealed evidence consistent with weak isolation-by-distance and modest spatial genetic differentiation for both species. Together, these results suggest a potential pest complex where previously only one species was in focus. Moreover, their broad diets and spatially restricted population dispersal patterns may also explain the sporadic nature of damage that has been recorded for this potential pest complex. Responses to emerging pest challenges can benefit from insights generated by population genomics techniques, opening up new avenues for research and supporting efforts to quickly tailor management strategies for novel pests.

burrower bug↗
PubMed2003

Reduced resistance of invasive varieties of the alien tree Sapium sebiferum to a generalist herbivore.

Invasive plants are often larger in their introduced range compared to their native range. This may reflect an evolved reduction in defense and increase in growth in response to low herbivory in their introduced range. Key elements of this scenario include genetic differences in defense and growth yet uniformly low rates of herbivory in the field that dissociate defense and herbivore damage for alien species. We conducted a laboratory experiment with Melanoplus angustipennis grasshoppers and Chinese Tallow Tree seedlings ( Sapium sebiferum) from its native range (China) and its introduced range (Texas, USA) where it is invasive. We caged grasshoppers with pairs of Sapium seedlings from the same continent or different continents. The amounts of leaf area removed from Texas and China seedlings, and their height growth rates, were indistinguishable when both seedlings in the pair were from the same continent. However, when grasshoppers had a choice between seedlings from different continents, they removed more Texas Sapium foliage than China Sapium foliage and height growth rates were higher for China Sapium seedlings compared to Texas seedlings. Grasshopper growth rates increased with greater Sapium foliage consumption. In a common garden in Texas, Sapium seedlings from Texas grew 40% faster than those from China. Chewing insect herbivores removed little Sapium foliage in the field experiment. Although grasshoppers preferred to feed on Texas Sapium when offered a choice in the laboratory, extremely low herbivory levels in the field may have allowed the Texas seedlings to outperform the China seedlings in the common garden. These results demonstrate post-invasion genetic differences in herbivore resistance and growth of an invasive plant species together with a decoupling of defense and herbivore choice in the introduced range.

Adaptation, Physiological↗
PubMed2005

Reproduction, foraging and the negative density-area relationship of a generalist rodent.

While many species show positive relationships between population density and habitat patch area, some species consistently show higher densities in smaller patches. Few studies have examined mechanisms that may cause species to have negative density-area relationships. We tested the hypothesis that greater reproduction in edge versus interior habitats and small versus large fragments contributes to higher densities of white-footed mice (Peromyscus leucopus) in small versus large forest fragments. We also examined vegetation structure and foraging tray utilization to evaluate if greater reproduction was a result of higher food availability. There were greater number of litters and proportion of females producing litters in the edge versus interior of forest fragments, which may have contributed to greater population growth rates and higher densities in edge versus interior and small versus large fragments. Data on vegetation structure and giving-up densities of seeds in artificial patches suggest that food availability may be higher in edge versus interior habitats and small versus large fragments. These results, in an area with few or no long-tailed weasels, provide a distinct contrast to the findings of Morris and Davidson (Ecology 81:2061, 2000) who observed lower reproduction in forest edge habitat as a result of high weasel predation, suggesting that specialist predators may be important in affecting the quality of edge habitat. While we cannot exclude the potential contributions of immigration, emigration, and mortality, our data suggest that greater reproduction in edge versus interior habitat is an important factor contributing to higher densities of P. leucopus in small fragments.

Analysis of Variance↗
PubMed2005

Effects of Bt maize-fed prey on the generalist predator Poecilus cupreus L. (Coleoptera: Carabidae).

We investigated the effects of transgenic maize (Zea mays) expressing Bacillus thuringienses toxin (Bt maize) on larval and adult Poecilus cupreus carabid beetles in laboratory studies. In no-choice trials, neonate P. cupreus larvae were fed exclusively with Spodoptera littoralis caterpillars, which had been raised on Bt maize. S. littoralis raised on conventional maize or "high quality" Calliphora sp. pupae were fed to the beetle larvae in two control treatments. Bt-maize-fed caterpillar prey increased mortality to 100% within 40 days. The experiment was repeated with 10-day-old beetle larvae. Bt treatment resulted in fewer pupae than in both controls, and in a higher mortality than in the Calliphora control. S. littoralis was suitable as exclusive prey in no-choice tests, at least for 40 days, although prey quality seemed to be low compared to Calliphora pupae. The observed effects are most likely indirect effects due to further reduced nutritional prey quality. However, direct effects cannot be excluded. In the second part of the study, exposure of P. cupreus to Bt intoxicated prey was examined in paired-choice tests. Adult beetles were offered a choice between different prey conditions (frozen and thawed, freshly killed or living), prey types (S. littoralis caterpillars, Calliphora sp. pupae, cereal aphids) and prey treatments (raised on Bt or conventional maize). Living prey was preferred to frozen and dead prey. Caterpillars were only preferred to fly pupae and aphids when living. Prey treatment seemed to be least important for prey selection. The tests showed that P. cupreus ingested caterpillars readily and there was no evidence of them avoiding Bt containing prey, which means exposure in the field could occur. The presented protocols are a first step towards ecological risk assessment for carabid beetles.

Animals↗
PubMed2001

The management of the red eye for the generalist.

Patients often present to primary care physicians with acute or chronic red eyes. Benign conditions may be evaluated and treated by primary care practitioners. Red eyes due to serious conditions may be vision threatening and require early detection and referral.

Conjunctival Diseases↗