Exploring the precision redox map during fasting-refeeding and satiation in C.elegans

Fasting is a popular dietary strategy because it grants numerous advantages,and redox regulation is one mecha-nism involved.However,the precise redox changes with respect to the redox species,organelles and tissues remain unclear,which hinders the understanding of the metabolic mechanism,and exploring the precision redox map under various dietary statuses is of great significance.Twelve redox-sensitive C.elegans strains stably expressing genetically encoded redox fluorescent probes(Hyperion sensing H_(2)O_(2) and Grx1-roGFP2 sensing GSH/GSSG)in three organelles(cytoplasm,mitochondria and endoplasmic reticulum(ER))were constructed in two tissues(body wall muscle and neurons)and were confirmed to respond to redox challenge.The H_(2)O_(2) and GSSG/GSH redox changes in two tissues and three organelles were obtained by confocal microscopy during fasting,refeeding,and satiation.We found that under fasting condition,H_(2)O_(2) decreased in most compartments,except for an increase in mitochondria,while GSSG/GSH increased in the cytoplasm of body muscle and the ER of neurons.After refeeding,the redox changes in H_(2)O_(2) and GSSG/GSH caused by fasting were reversed in most organelles of the body wall muscle and neurons.In the sati-ated state,H_(2)O_(2) increased markedly in the cytoplasm,mitochondria and ER of muscle and the ER of neurons,while GSSG/GSH exhibited no change in most organelles of the two tissues except for an increase in the ER of muscle.Our study systematically and precisely presents the redox characteristics under different dietary states in living animals and provides a basis for further investigating the redox mechanism in metabolism and optimizing dietary guidance.

Habitat fragmentation alters predator satiation of acorns

Aims Acorn weevils(Curculio spp.),endoparasitic granivorous insects,impede recruitment of fagaceous trees,and in turn affect community structure and ecosystem functioning.Previous studies have made considerable progress in elucidating local factors that contribute to seed predation by acorn weevils,but it is still not clear how habitat configurations interplay with local factors in influencing Curculio predation.In this study,we assessed the roles of crop size,landscape configurations(area and isolation)and their interactions on the predation rate of seeds by acorn weevils.Methods We studied acorn weevils feeding on the seeds of Castanopsis sclerophylla(Fagaceae)on two peninsulas and nine islands with varying areas and isolation levels in the Thousand-island Lake in Chun’an County,Zhejiang Province of China.Overall,crop size was estimated for 130 trees and predation status was assessed for 26207 seeds from these trees during two years.Generalized linear mixed models were performed to clarify how island area and isolation interplayed with crop size to determine predation rate on a single tree.Important Findings A negative relationship was detected between crop size and seed predation rate,indicating predator satiation at the tree level.This suggests that acorn weevils tend to stay sedentary once they have arrived at a suitable habitat.Habitat fragmentation had significant effects on seed predation such that predation rate was higher on larger,less isolated islands.Furthermore,the relationship between crop size and predation rate was significantly changed by both island area and isolation.This finding highlighted that the effects of habitat isolation might be overlooked relative to those of habitat loss.

Fruit availability, frugivore satiation and seed removal in 2 primate-dispersed tree species

During a mast-fruiting event we investigated spatial variability in fruit availability,consumption,and seed removal at two sympatric tree species,Manilkara bidentata and M.huberi(Sapotaceae)at Nouragues Natural Reserve,French Guiana.We addressed the question of how Manilkara density and fruits at the community level might be major causes of variability in feeding assemblages between tree species.We thus explored how the frugivore assemblages differed between forest patches with contrasting relative Manilkara density and fruiting context.During the daytime,Alouatta seniculus was more often observed in M.huberi crowns at Petit Plateau(PP)with the greatest density of Manilkara spp.and the lowest fruit diversity and availability,whereas Cebus apella and Saguinus midas were more often observed in M.bidentata crowns at both Grand Plateau(GP),with a lowest density of M.bidentata and overall greater fruit supply,and PP.Overall,nearly 53%and 15%of the M.bidentata seed crop at GP and PP,respectively,and about 47%of the M.huberi seed crop were removed,otherwise either spit out or defecated beneath trees,or dropped in fruits.Small-bodied primates concentrated fallen seeds beneath parent trees while large-bodied primate species removed and dispersed more seeds away from parents.However,among the latter,satiated A.seniculus wasted seeds under conspecific trees at PP.Variations in feeding assemblages,seed removal rates and fates possibly reflected interactions with extra-generic fruit species at the community level,according to feeding choice,habitat preferences and ranging patterns of primate species.

Utility Representations of Preferences on General Choice Spaces

The purpose of this paper is to reconsider the utility representation problem of preferences,Sev-eral representation theorems are obtained on general choice spaces.Preferences having continuous utility functions are characterized by their continuities and countable satiation.It is showed that on a pairwise separable choice space,the sufficient and necessary condition for a preference to be represented by a contin-uous utility function is that the preference is continuous and countably satiable.For monotone prefer-ences,we obtain that any space has continuous utility representations.

Effects of masting on seedling establishment of a rodent-dispersed tree species in a warm-temperate region,northern China

Masting is an evolutionary strategy used by plants to promote seed survival and/or seed dispersal under animal predation,but its effects on seedling establishment in field condition are rarely tested by long-term experiments incorporating combined effects of seed and animal abundance.Here,we tracked seed production,rodent-mediated seed dispersal,and seedling establishment in Armeniaca sibirica from 2005 to 2014 in a warm-temperate forest in northern China,and examined the effects of seed abundance and per capita seed availability on seed fate and seedling recruitment rate.Our results showed that seed abundance or per capita seed availability generally benefited the seedling recruitment of A.sibirica through increasing dispersal intensity,supporting predator dispersal hypothesis.However,seedling recruitment showed satiated or even dome-shaped association with per capita seed availability,suggesting the benefit to trees would be decreased when seed abundance were too high as compared to rodent abundance(a satiated effect).Our results suggest that the predator dispersal and satiation effects of masting on seedling recruitment can operate together in one system and conditionally change with seed and animal abundance.

How seed defense and seed abundance predict dispersal and survival patterns in Camellia

Little is known about how seed defense and seed abundance interact with behavioral responses of seed dispersers to predict dispersal and survival dynamics in animal-dispersed plants.By tracking the fate of individual seeds in Camellia stands with high and low seed abundance in Southwest China in 2007,we investigated the dispersal and survival of 2 high-saponin Camellia species(Camellia oleifera and Camellia sinensis and 1 non-saponin species(peanut Arachis hypogaea)as a control.Saponins in Camellia seeds are chemical compounds that act as seed defense.Our results were most consistent with the predictions based on the predator satiation hypothesis and the plant defense hypothesis.At the abundant Camellia stand(predators and dispersers were satiated),more Camellia seeds survived at the source but fewer were hoarded and survived at cache sites.At the sparse Camellia stand(predators and dispersers were not satiated),no Camellia seeds survived at the source,but more Camellia seeds were hoarded and survived at cache sites.Unlike Camellia seeds,no peanuts survived at the source at both stands,while more peanuts were hoarded and then survived at cache sites in the abundant Camellia stand compared to none at the sparse Camellia stand.In addition,the 2 Camellia species showed similar trends for seed fates across different dispersal stages.Our study indicates that the combined effects of seed abundance and seed defense,compared to their separate effects,provide a more accurate prediction for dispersal and survival patterns in animal-dispersed Camellia species.

Fluctuation in seed abundance has contrasting effects on the fate of seeds from two rapidly germinating tree species in an Asian tropical forest

The seed predator satiation hypothesis states that high seed abundance can satiate seed predators or seed dispersers,thus promoting seed survival.However,for rapidly germinating seeds in tropical forests,high seed abundance may limit dispersal as the seeds usually remain under parent trees for long periods,which may lead to high mortality due to rodent predation or fungal infestations.By tracking 2 species of rapidly germinating seeds(Pittosporopsis kerrii,family Icacinaceae;Camellia kissi,family Theaceae),which depend on dispersal by scatter-hoarding rodents,we investigated the effects of seed abundance at the community level on predation and seed dispersal in the tropical forest of Xishuangbanna Prefecture,Southwest China.We found that high seed abundance at the community level was associated with delayed and reduced seed removal,decreased dispersal distance and increased pre-dispersal seed survival for both plant species.High seed abundance was also associated with reduced seed caching of C.kissi,but it showed little effect on seed caching of P.kerrii.However,post-dispersal seed survival for the 2 plant species followed the reverse pattern.High seed abundance in the community was associated with higher post-dispersal survival of P.kerrii seeds,but with lower post-dispersal survival of C.kissi seeds.Our results suggest that different plant species derive benefit from fluctuations in seed production in different ways.

How does the 120-year cycle mast seeding of dwarf bamboo affect the rodent population?

Background:In 2017,large-scale flowering,seeding,and dying events of dwarf bamboo(Sasa borealis)occurred in a wide range in central Japan for the first time in 120 years.This phenomenon of S.borealis,like the mast seeding of trees,could be expected to provide a large amount of food for seed-eating rodents and gradually affect their ecology and population dynamics.We captured rodents in survey plots in a secondary broad-leaved forest with the phenomenon from 2018 to 2019 to investigate the species,the number of individuals,growing stage,sex,and body mass.In addition,we also compared the capture data for 2 years(2018–2019)with that for the mast seeding year(2017)and 6 years before it(2011–2016).Results:The mast seeding of S.borealis greatly increased the population size of rodents,especially Apodemus speciosus and A.argenteus.Conversely,Eothenomys smithii did not show such an increase.Most of the captured rodent individuals were already adults at the time of new capture,and the proportion of male juveniles was extremely low.These results suggest that the mast seeding of S.borealis created unusually rich food availability for the population concentration of rodents due to their immigration.However,body mass was not significantly different before and after the mast seeding.In addition,the increased populations of the two Apodemus species did not decline 2 years after the S.borealis masting,contrary to the previously reported decrease of rodent populations after tree masting.Conclusions:Our results indicate that the mast seeding of S.borealis affected the population dynamics of Apodemus species over a long time and their individual composition of different growth stages.However,it did not affect their body mass.