The site where peripherally administered cholecystokinin-8 elicits satiety was investigated by injecting rats with cholecystokinin-8 (1 to 8 micrograms per kilogram of body weight, intraperitoneally) after they had received bilateral lesions of the ventromedial hypothalamus or after they had undergone bilateral abdominal vagotomy or selective vagotomies. Abdominal vagotomy or gastric vagotomy abolished or reduced the satiety effect of cholecystokinin, but lesions of the ventromedial hypothalamus did not. These results demonstrate that peripherally administered cholecystokinin acts in the abdomen through gastric vagal fibers and not directly on the brain to produce satiety in the rat.
Intraspecific variation in floral visitor behaviour and pollination efficiency has been much less studied than interspecific variation. Nevertheless, it is clear that large differences in these traits exist within species, and in particular between sexes within species. With the exception of a few well‐studied interactions, however, the consequences of these differences in the pollinators and visited plants remain to be investigated. In this review, we document large and consistent differences in the foraging patterns of male and female pollinators that have been demonstrated to directly affect plant reproduction or that have clear potential to do so. Males and females differ in visitation frequency, type of flowers visited, and per‐visit pollen transfer. Females gather more and different resources from flowers compared to males, and males generally tend to show more mobile foraging patterns than females. We argue that these sex‐associated patterns have broad generality across pollinators, and that sex‐associated differences can in some cases be larger than differences between species. We offer predictions about how these patterns will influence pollinator preference, specialization, and fidelity, as well as the cost, quality and quantity of pollination service to plants. In the face of increasing threats to plant–pollinator interactions, understanding their basic functioning and the variation inherent in their component parts is critical. We advocate for more attention to sex‐based differences among pollinators in particular, and the consequences of intraspecific variation more broadly.
Recent work [Ecoscience (2000) vol. 7, 395–397] suggests that the burying beetle Nicrophorus pustulatus may have undergone a remarkable host shift, exploiting snake eggs rather than carrion as resources for breeding. We conducted behavioural and physiological experiments to examine the hypothesis of a host shift and to formulate hypotheses on its origin. Two congeners of N. pustulatus, Nicrophorus orbicollis and Nicrophorus defodiens did not respond to snake eggs with typical breeding behaviour. When N. pustulatus male–female pairs (n = 14) were presented with clutches of snake eggs, the number of offspring but not the mean size of offspring varied with snake egg mass, indicating effective regulation of brood size. When breeding on turtle eggs, N. pustulatus had a more variable response than when exploiting snake eggs, suggesting that turtle eggs are not a primary resource for breeding. Nicrophorus pustulatus presented with both snake eggs and a mouse carcass combined and exploited the two resources within the same nest (10 of 12 trials). Mouse carcasses and snake eggs were treated differently. Carcasses were moved, buried and stripped of hair in a manner characteristic of burying beetles, whereas snake eggs were not moved or buried. Females that discovered a mouse carcass also had a significantly greater juvenile hormone increase than did females discovering snake eggs. Some responses to the two resources, however, were similar. Female N. pustulatus oviposited rapidly in response to either a mouse carcass or snake eggs, and males elevated sex pheromone emission in response to either resource. The efficient use of snake eggs, the ability to regulate brood size and the different responses to snake eggs and carrion suggest that N. pustulatus is well adapted to exploiting snake eggs for breeding. The use of snake eggs by N. pustulatus has potential implications for conservation of oviparous reptiles.
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