Experimental clearance rate and intraguild predation of jellyfish Cyanea nozakii

Cyanea nozakii,a common jellyfish distributed in offshore China,has a complex trophic relationship with other zooplankton groups.However,few studies have reported the predation rates and prey selection patterns of C.nozakii medusae on different prey items.Research is also lacking on the intraguild predation of Aurelia coerulea(another common bloom jellyfish in offshore China)by C.nozakii.To address the knowledge gaps,the clearance rates of C.nozakii for different prey items,including copepods(small<1000μm and large>1000μm),fish larvae,and gelatinous prey(hydromedusae,A.coerulea ephyrae,and chaetognaths),were measured.The influence of predator size on the clearance rate was also determined.Additionally,we examined the intraguild predation of C.nozakii on A.coerulea medusae.The clearance rates of C.nozakii varied widely with prey organisms,being independent of prey concentrations.Gelatinous organisms,except for chaetognaths,were captured with considerably high efficiency,followed by fish larvae and copepods,indicating the preferential prey selection of gelatinous organisms by C.nozakii.The clearance rate increased linearly with the cross-sectional area of C.nozakii.Body size in medusae may,to some extents,underpin their capacity to capture more prey by increasing the encounter rate and capture success through ontogeny.C.nozakii preyed voraciously on A.coerulea in high feeding efficiency,but the clearance rate decreased with increasing A.coerulea(as prey)size.This phenomenon of intraguild predation suggests a speculative hypothesis of potential population regulation of A.coerulea by C.nozakii.The information regarding the feeding ecology of C.nozakii reported in this study is important for understanding plankton dynamics in marine ecosystems with extensive occurrences of this jellyfish.

Biochar-Based Seed Coating as an Effective Strategy to Reduce Seed Predation When Restoring Forests on Degraded Land

As ecosystem degradation becomes more widespread, there is a growing need for efficient and effective forest restoration methods. Direct seeding is one such method that can be used to cover a relatively large area, particularly places with difficult-to-access terrain. One major obstacle hampering successful restoration via direct seeding is seed predation, as seeds are damaged or eaten. We tested the effectiveness of encrusting six species of native seeds with biochar-based coating in reducing the seeds’ chances of being predated on degraded hillsides and landslide scars in Hong Kong. The six seeded species are native trees and shrubs, including both late-successional and pioneer species that are present in forests and shrublands. Our results show that biochar-based seed coats were able to significantly reduce overall seed predation by 5.77% (SE = 1.41, p < 0.05). Additionally, we found varied effectiveness of the biochar-based seed coats across species and seed morphology. Of the six species that were included, four of them had significantly reduced seed predation after encrusting with biochar-based seed coats, while two other species were not significantly affected by the biochar-based seed coats. When we investigated seed predation against seed morphology, we found that while the species with larger seeds were more likely to be predated when sown without any biochar-based seed coat, the effectiveness of the biochar-based seed coat to reduce predation also increased with larger seeds. Our results suggest that encrusting seeds with biochar-based seed coats is an effective means of reducing seed predation.

Preliminary Study of Predation Effectiveness of the Assassin Bug Rhynocoris rapax Stal (Heteroptra: Reduviidae) on Fall Armyworm Spodoptera frugiperda Smith (Lepidoptera: Noctuidae), a Major Pest of Maize Crops

Maize is a staple food in many sub-Saharan African countries, grown on large surfaces and with high production. However, maize’s cultivation is often confronted with attacks by the fall armyworm, which considerably reduces production. Thus, the use of biological agents in the control of the fall armyworm would contribute effectively to the sustainability of agriculture. It is in this context that this study, conducted at the La Mé station of the National Centre for Agronomy Research, aims to test the effectiveness of Rhynocoris rapax, a powerful predator of various insect families, on the fall armyworm Spodoptera frugiperda, for biological control of this maize pest in Côte d’Ivoire. Therefore, 3 batches of 1 adult individuals of Rhynocoris rapax were captured in trial plots set up at the La Mé station. These individuals were then put in contact with 3 batches of 5, 20 and 40 larvae of the pest in rearing boxes at an average temperature of 26.4°C and an average relative humidity of 60%, in order to evaluate the efficiency of the predation. The results showed that Rhynocoris rapax kills more larvae when these are in large numbers. The mortality of the high number of larvae was observed during the first three days, probably due to the voracity and aggressiveness of Rhynocoris rapax that period. So R. rapax is a potential predator of fall armyworm and should be protected.

The effects of anthropogenic noise on nest predation with respect to predator species across different habitats and seasons

Noise pollution is a maj or component of sensory pollution that can disrupt the well-being and functioning of living organisms,affect a variety of life history traits in animals,and reduce their reproductive success.In this study,we used artificial nest experiments with noise manipulation to investigate the influence of anthropogenic noise on nest predation during the breeding and non-breeding seasons and in different forest habitats.We found that the noise treatment did not alter the predation rates or survival probabilities of birds in artificial nests.However,the diversity and species composition of nest predators in artificial pine forests varied between breeding and nonbreeding seasons,which may be explained by season-specific adaption of nest predators to bird nests or the unstable ecosystems of artificial forests.The diversity and species composition of nest predators differed between the different forests,probably because of differences in habitat heterogeneity.Predation time varied with treatment,season,and habitat,although most predators were nocturnal mammals.Niche segregation or changes in optimal foraging time may explain this phenomenon.

Predation of Pardosa pseudoannulata and Pardosa procurva Against Plutella xylostella

[Objective] This study was conducted to explore the predation of Pardosa pseudoannulata and Pirata procurva_ on Plutela xylostela larvae. [Method] The quantities of P. xylostela larvae predated by the two spider species at different temperatures and the quantities of P. xylostela larvae predated by P. pseudoannula-ta_in different volumes were analyzed. Based on three factors at five levels, the quadratic general regression rotation combination design was used to study the combined control effect of the two spider species on P. xylostela_larvae and the control effect of P. pseudoannulata on the larvae of P. xylostela and Spodoptera litura. [Result] The quantities of P. xylostela_ larvae predated by the two spider species increased first and then decreased with the increase of temperature, and the functional predation response of P. pseudoannulata and P. procurva_ on the fourth instar larvae of P. xylostela_fitted the Hol ing-Ⅱ model, and the Hol ing-Ⅲmodel could perfect the evaluation on the predation effect. Volume had great effect on the feeding of P. pseudoannulata. lnstantaneous attack ability （a’）, the time to handle one prey （Th） and predation function （a’/Th） in a smal er volume were al higher than that in a larger volume. The predation of the two spider species on P. xylostela_larvae was positively correlated with their densities. The overal effect of the three factors was： the density of P. xylostela＆gt;the density of P. procurva＆gt;the density of P. pseudoannulata. The densities of P. xylostela and S. litura larvae could affect the feeding amount of P. pseudoannulata. But there was no predation preference for P. pseudoannulata on the larvae of P. xylostela and S. litura. [Con-clusion] The results wil provide a reference for the evaluation of control effect of_P. xylostela_by P. pseudoannulata_and P. procurva in the field.

Two-way predation between immature stages of the hoverfly Eupeodes corollae and the invasive fall armyworm(Spodoptera frugiperda J.E.Smith)

Since its 2018 invasion of eastern Asia,the fall armyworm Spodoptera frugiperda(Lepidoptera:Noctuidae)has become a key pest in local maize production.Though pesticides have been widely used to mitigate the initial S.frugiperda attack,biological control is receiving ample attention as a desirable,environmentally-sound alternative to chemical control.Hoverflies(Diptera:Syrphidae)are abundant natural enemies in Chinese maize fields and have been observed to consume S.frugiperda larvae.In this study,we use laboratory assays to study the two-way interaction between immature stages of S.frugiperda and the endemic syrphid Eupeodes corollae.To mimic natural conditions,assays were performed in the presence of fresh maize leaves.Those 2 nd or 3 rd instar larvae of E.corollae preyed on 1 st and 2 nd instar S.frugiperda larvae with a Holling type III response,consuming a respective theoretical maximum of 43.48 and 83.33 larvae over a 24-h period.Conversely,once S.frugiperda larvae reached 3 rd instar,they exhibited aggressive behavior and equally preyed on syrphid larvae with a Holling type III response.Those 5 th and 6 th instar larvae of S.frugiperda consumed a respective 16.39-19.23,6.02-19.61 and 6.76-8.26 of 1 st,2 nd and 3 rd instar E.corollae larvae per day.Though our results await field-level validation,S.frugiperda agonistic(i.e.,defensive)and consumptive behavior towards resident natural enemies such as E.corollae possibly degrades biotic resistance and raises its invasion potential.Our findings shine new light on the interaction between lepidopteran herbivores and their natural enemies,and can help advance the development of conservation biological control and other integrated pest management(IPM)strategies against S.frugiperda in China and abroad.

Effects of Predation by Invasive Western Mosquitofish(Gambusia affinis) on Survival of Eggs,Embryos and Tadpoles of Pelophylax nigromaculatus and Duttaphrynus melanostictus in South China

Alien species are one of the most serious threats to the decline and extinction of native amphibian populations. In this study, we examined the predation of invasive Western Mosquitofish Gambusia affinis on the eggs, embryos, and tadpoles of Duttaphrynus melanostictus and Pelophylax nigromaculatus in south China. Our results suggested that the survival of eggs and embryos remaining in the egg capsules of P. nigromaculatus and D. melanostictus was significantly higher than those removed from the egg capsule at 12-h intervals within 72 h in the presence of G. affinis. The survival of P. nigromaculatus eggs and embryos without egg capsules was significantly lower than those of D. melanostictus without egg capsules. The survival of P. nigromaculatus eggs and embryos with egg capsules was significantly higher than those of D. melanostictus with egg capsules from 24 h to 72 h except for 12 h. The survival of D. melanostictus tadpoles was significantly higher than that of P. nigromaculatus tadpoles in the presence of G. affinis. The survival of Gosner stage 26 tadpoles of P. nigromaculatus was significantly higher than that of Gosner stage 30 tadpoles from 12 h to 60 h, but there were no significant differences at 72 h. In contrast, the survival of Gosner stage 26 tadpoles of D. melanostictus was significantly lower than that of Gosner stage 30 tadpoles within 72 h, recording every 12 h. The increasing temperature caused a significant increase in predation by G. affinis on P. nigromaculatus eggs and embryos. The outer jelly capsule surrounding anurans eggs might serve as a mechanical defense against predation by G. affinis due to its large diameter, relatively stationary state and unpalatability. The differences in the vulnerability of P. nigromaculatus and D. melanostictus embryos and tadpoles to G. affinis probably due to differences in the unpalatability, black skin and activity. Based on the magnitude of predation by G. affinis on the eggs, embryos and tadpoles of these two species and the combined impact of temperature, we might speculate that invasive G. affinis and global warming would have more detrimental impacts on population viability of P. nigromaculatus than D. melanostictus in China.

Does bird photography affect nest predation and feeding frequency?

Bird photography is a popular and growing form of ecotourism that contributes to the economic growth of local communities,but its disturbance to bird reproduction remains understudied.We worked in a tropical forest of southern China,which has experienced a sharp increase in the number of photographers in recent years.We compared nests that were photographed and those that were not,in their nest predation and parental feeding rates.Including nests of 42 species,the results demonstrate that the predation rate of nests that were not photographed(incubation stage:43.3%of 194 nests;nestling stage:34.5%of 110 nests)was significantly higher than that of photographed ones(incubation:2.4%of 83 nests;nestling:11.1%of 81 nests).Among different nest types,open cup nests in shrub and trees were most affected by photography,in both incubation and nestling stages.Of five factors investigated,including three natural factors(nest stage,structure and position),and two anthropogenic factors(photography and distance to forest edge),only photographic disturbance and nest structure had significant effects(open nests had higher predation).The feeding frequency at nests when photographers were present was not strongly different from when they were not present.Human activity therefore had no negative effects on the birds,but showed a positive effect on their nesting success,in terms of reducing nest predation rates.However,there needs to be further assessment of other aspects of nesting(e.g.,clutch size,duration of nestlings in nests),and other kinds of stress responses(e.g.,hormonal changes),before the total effect of bird photography can be understood.

Experimental clearance rates of Aurelia coerulea ephyrae and medusae,and the predation impact on zooplankton in Jiaozhou Bay

The population explosion of jellyfish Aurelia coerulea occurred in Jiaozhou Bay,China in 2009.The potential predation impact of A.coerulea on zooplankton was investigated.Population clearance potential and residence time(t 1/2)for copepods were calculated from laboratory clearance rates and measurements of jellyfish size and abundance from May to August 2009 in Jiaozhou Bay.Clearance rates varied widely with prey organisms,but they were not significantly different among various prey concentrations.Medusae captured rotifers,fish larvae and hydromedusae more efficiently than fish eggs,copepods and chaetognaths.Ephyrae captured rotifers and hydromedusae more efficiently than fish larvae and copepods.Clearance rate linearly increased with the cross sectional area of A.coerulea(size from 0.3 to 7.1 cm).Water temperature also had a marked effect on clearance rate and this was related to the increased beat frequency as water temperature increased.In early May 2009,A.coerulea potentially cleared the volume of water in the Bay less than 0.001 times a day,but this value was estimated to be more than 0.3 times a day in July.The t 1/2 for copepods was less than 6 d in June and July.Abundances of copepods,hydromedusae and chaetognaths were extremely low in 2009 compared to 2008 and 2010(jellyfish non-bloom years).Large predation pressure by the A.coerulea population occurred to control zooplankton communities in Jiaozhou Bay.A.coerulea,when present at a high population level,can be a keystone species in Jiaozhou Bay and control the trophic structure here.

Intraguild predation by polyps of three scyphozoan jellyfish:Nemopilema nomurai,Aurelia coerulea,and Rhopilema esculentum

Jellyfish blooms occur worldwide and have resulted in serious problems in tourism,fisheries,coastal industries,and the marine ecosystem.The life cycle of scyphozoan jellyfish consists of a pelagic medusa stage and a benthic polyp stage.Success of asexual reproduction of the polyps determines directly the number of medusae;thus,the polyp stage is the key to understanding the population dynamics of medusae.Nemopilema nomurai,Aurelia coerulea,and Rhopilema esculentum are three scyphozoan jellyfish commonly inhabit in Chinese coastal waters.Polyps of A.coerulea are easily visible,while those of N.nomurai and R.esculentum remain yet to be found in the wild.However,distribution of the medusa indicates that the polyps of all three species may occur together.To evaluate the distribution pattern of polyps of the three species and explore intraguild predation by the polyps,we conducted a laboratory experiment that considered the attachment sequence and size relationship of calyx diameter of the polyps.We found that the polyps of A.coerulea preyed on polyps of the other two species in all treatments,except when polyps of R.esculentum were bigger than those of A.coerulea.The polyps of R.esculentum preyed on the polyps of N.nomurai only when polyps of R.esculentum attached first and were bigger than those of N.nomurai.Colonies of N.nomurai polyps were rarely found in the places inhabited by A.coerulea polyps.In addition,A.coerulea polyps are known to inhabit at depths of less than 20 m in coastal sea,thus,we speculate that N.nomurai polyp colonies might occur at depths of more than 20 m.Therefore,our finding that polyps of A.coerulea aggressively preyed on polyps of other species may help understand other such systems of jellyfish bloom in the world.

Research activity does not affect nest predation rates of the Silver-throated Tit,a passerine bird building domed nests

Background:Research activities have often been thought to potentially influence avian nesting success by increasing nest predation rates.Although recent studies of species building open nests and cavity nests suggest that research disturbance does not generally induce nest predation,whether it is also the case in species building domednests remains unknown.In birds,domed-nest species exist in about half of the passerine families,and research disturbance to the domed nests may differ from that to the nests of other types for their different nest structures.Methods:We investigated if research activities affected nest predation rate by analyzing the relationships of the daily nest survival rate with the research activities at the egg and nestling stages of a domed-nest species,the Silverthroated Tit(Aegithalos glaucogularis).Results:Our results showed that nest daily survival rate was significantly affected by the laying date and nest age during the egg stage,and by the hatching date only during the nestling stage.By contrast,there were no significant effects of research activities,in terms of visiting nests and filming nests,on the nest survival of the Silver-throated Tit at both the egg and nestling stages.Conclusions:Our results coincide with the findings in species building other types of nests that research activities do not always have negative effects on avian nesting success.

Coyote Predation Effects on White-Tailed Deer Fawns

Coyotes (Canis latrans) are a relatively new predator to the southeastern United States, and may be negatively impacting white-tailed deer (Odocoileus virginianus;hereafter, deer) populations. Our objectives were to evaluate the impacts of coyotes on deer fawns by assessing deer fawn survival and cause-specific mortality, and gain an understanding of factors affecting fawn survival and coyote predation. We captured and radio collared 30 fawns in the Red Hills region of Florida and Georgia, USA (2012-2013). Fawns were monitored for 12 weeks for survival and cause-specific mortality, and we quantified habitat and environmental characteristics of birth sites. Predation (n = 19;95%) was the leading cause of fawn mortality (n = 20;67%), with coyote predation (n = 14;74%) being the most important type of predation. Survival rates for all fawns were greater (P = 0.048) where coyotes were removed compared to non-removal sites, with 50% and 25% of fawns surviving to 12 weeks on coyote-removal and non-removal sites, respectively. Survival rates of fawns ultimately predated by coyotes were greater (P = 0.096) on coyote-removal than non-removal sites, with 40% and 50% of fawns predated by coyotes within 12 weeks on coyote-removal and non-removal sites, respectively. Survival of all fawns and those predated by coyotes was lower when fawns were born at sites with greater hardwood basal area, total basal area, and canopy closure;and survival improved if born in or near hardwood, natural pine, and managed (planted) pine cover types. Increased canopy cover within 10 m of the birth site was selected by adult females for birth sites of all fawns and those that were predated by coyotes. Compared with fawns that lived, all dying fawns and those predated by coyotes had less shrub cover within 5 m and less grass cover at and within 10 m of the birth site. Coyote removal increased fawn daily survival rates, and habitat played a role in fawn survival.

Field and Laboratory Observations on Predation and Prey Selectivity of the Scyphomedusa Chrysaora cf.caliparea in Southeast Indian Waters

Chrysaora cf.caliparea,one of the most abundant medusae species in India,seems to be an important predator in the coastal waters of Bay of Bengal.The ability of Chrysaora cf.caliparea to feed at maximum rate in high prey concentrations implies that this jellyfish can efficiently exploit dense prey patches,at least for a short period.This study presents preliminary information regarding digestion and feeding rate upon copepods in a warm water environment.The ingestion rate of the average-sized medusae Chrysaora cf.caliparea is well balanced in nature,which in turn implies that this jellyfish is tuned for optimal utilization of available prey resources.Comparison with earlier research indicates that prey escape speed is one important factor governing which prey will be captured.A full understanding of predation mechanics awaits further investigation of both predator and prey behavior.However,because of the scarcity of long-term quantitative population data most insights have to be made indirectly.Nevertheless,low abun-dance of Chrysaora cf.caliparea in the water column during summer (May 2007) and the overall annual abundance seem not to con-siderably affect the zooplankton population,especially copepods.The present work contributes to the knowledge of prey-predator relationship of the forgotten fauna in Indian waters,which is especially crucial for understanding the process of ecological recovery of coastal water environment.

Growth and decline of arboreal fungi that prey on Bursaphelenchus xylophilus and their predation rate

Pine wilt disease caused by pine wood nema-todes is a deadly disease of the genus Pinus requiring strong quarantine measures.Since its discovery,it has been widely distributed throughout the world.China is one of the coun-tries with a severe rate of infections due to its abundant pine resources.In this study,nematode-trapping fungi were collected from pine trees in Ninghai City,Zhejiang Prov-ince,which is the key area of pine wilt control in Febru-ary,May,September,October and November.The results showed that nematode-trapping fungi of pine are abundant,especially the number and species detected in each month and are quite different;species of fungi in July,Septem-ber and November were more numerous and had higher separation rates.The dominant species in November was Arthrobotrys oligospora followed by Arthrobotrys cladodes;July and September it was A.cladodes.In each part of the tree,A.cladodes was the most widely distributed with a high separation rate.Therefore,it is the dominant fungal species in the area.Arboreal Bursaphelenchus xylophilus-trapping fungi are dependent on pine wood nematodes,and none were isolated from healthy pine trees.More arboreal B.xylophilus-trapping fungi were found under the bark than in the xylem.There is a close relationship between arboreal B.xylophilus-trapping fungi and pine wood nematodes.How to make use of these resources to reduce the damage of pine wood nematode fusarium is the focus of future research.

Nest predation pressure on Chinese Bulbuls decreases along the urbanization gradient in Hangzhou,China

Nest predation is an essential factor affecting bird population density,reproductive ecology and life cycle.However,there are still contradictory results about how nest predation pressure changes with urbanization.One of the reasons for the controversy is that previous studies often use artificial nests to investigate nest predation,but the result of artificial nests is often biased and contrary to that of natural nests.Therefore,it is important to perform nest predation experiments simultaneously with both natural and artificial nests.In this study,we examined the change of nest predation pressure on the Chinese Bulbul(Pycnonotus sinensis)along the urbanization gradient in Hangzhou,China.We detected 148 natural nests of Chinese Bulbuls and continuously monitored them in two continuous breeding seasons from 2012 to 2013.After the breeding season,we placed artificial eggs in natural nests of Chinese Bulbuls to investigate the changes in nest predation pressure and used infrared cameras to record the predators.We then calculated the urbanization synthetic index(USI)as the measure of the degree of urbanization and examined its relationship with nest predation pressure.We found that no matter whether natural nests or artificial eggs were used,the nest predation pressure always decreased significantly with the degree of urbanization.The average height of shrubs within 10 m of the nest differed significantly between the predated and unpredated nests,which also affected the risk of nest predation.Our study highlights the importance of using natural and artificial nests simultaneously to conduct nest predation experiments,which can reduce the bias or errors caused by only using artificial nests.We also recommend the use of infrared cameras in future nest predation studies,which has obvious advantages in monitoring and identifying potential predators.

A Stage-structured Three-species Model with Intra-guild Predation and Disturbing Pulse

This paper considers a stage-structured three species model with intra-guild predation and disturbing pulse. Sufficient conditions which guarantee the global attractivity of boundary periodic solution and permanence of the system are obtained. Our results show that the pulse and time delay bring great effect on the dynamical behaviors of the model.

Risk of predation: a critical force driving habitat quality perception and foraging behavior of granivorous birds in a Nigerian forest reserve

Background:Understanding the factors that influence the foraging behavior and perception of habitat quality by animals has long been the focus in ecology. Due to the direct effect resource acquisition has on an individual's fitness and species' survival, predation risk is considered widely to be a major driver of foraging decision. The objectives of this study were to investigate how predation risk is perceived by granivorous bird species with respect to different habitat and microhabitat types, time of day and food types in Amurum Forest Reserve, Nigeria, with a view to direct future conservation planning. Methods: For 3 months, we conducted field experiments to measure giving-up densities (GUD, the amount of food left behind in artificial patches after birds cease to forage in it) and how it differs with habitat types, microhabitats, times of day, and food types. General linear mixed-effect models (GLMMs) were fitted to investigate the differences in GUD with respect to the aforementioned variables. Model selection was done based on the Akaike's Information Criterion (AIC). Results: There was no significant difference in GUDs across habitats. However, there was a significant difference in GUDs between microhabitats. Higher food remnants were recorded in the open than in cover microhabitats, as birds exploited food patches in the cover more. Time of day influenced foraging behavior in the birds. They foraged more in the morning than afternoon across all three habitats except for the gallery forest where birds foraged less in the morning. Higher GUDs were recorded in open than cover microhabitats both in the morning and the afternoon. Birds had a preference for rice, millet, and groundnut respectively. Conclusion:The differences in GUDs were very indicative of differences in foraging behavior and perception of resource availability in response to perceived predation risk. Therefore, this study suggests that the understanding of foraging decisions can be a veritable method for assessing habitat quality as perceived by animals.

Study on Predation of Moon Jellyfish Aurelia aurita on Edible Jellyfish Rhopilema esculenta

In recent years, jellyfish blooms have attracted considerable scientific interest for the potential impacts on marine organism and ecosystem functioning, with much attention paid to jellyfish as predators. Other than qualitative data and observations, few studies have quantified direct predation on jellyfish. This study is designed to test the predation between edible jellyfish Rhopilema esculenta and moon jellyfish Aurelia aurita with the average time and captured rate. And comparisons are done using the least significant difference （LSD） test at P 〈 0.05 and P 〈 0.01. The young edible jellyfish and moon jellyfish are bred and observed on the predatory behavior in Qingdao aquarium. A total of 520 jellyfish are sampled to quantify predation between moon and edible jellyfish in four tests. The results show that moon jellyfish of 10-11 mm in umbrella diameter prey on edible jellyfish of 4-5 mm in 16 min, and the predation rate is 100%. Moon jellyfish of 18-20 mm spend a longer time to feed all edible jellyfish of 9-12 mm. Edible jellyfish can not be caught, if its umbrella diameter is more than 20 mm. Though edible jellyfish is bigger than moon jellyfish, the former can not prey on the later in a tank. The differences between the four groups are very significant （P 〈 0.01）. The observation indicates that moon jellyfish is one of the natural enemies of the young edible jellyfish. Early prediction and reduction of moon jellyfish can not only effectively defense adult jellyfish outbreaks, but also improve the yield of edible jellyfish. With the edible jellyfish growing, its defense is enhancing. Edible jellyfish can not prey directly on moon jellyfish, but they still interact in the food, water quality and the survival space.

Anthropogenic noise interacts with the predation risk assessment in a free-ranging bird

Anthropogenic noise can affect a number of behavioral,physiological,and ecological aspects of animals from major taxonomic groups,raising serious conservation concerns.For example,noise pollution impacts communicative behavior and perception of signals,movements and distribution,as well as predator–prey interactions,such as hunting success or predator detection and predation risk assessment.We have carried out an experimental playback study,in which we investigated whether exposure to anthropogenic noise(sound of a tractor)distracts free-ranging barn swallows Hirundo rustica from paying attention to an approaching human“predator”(the“cognitive distraction”hypothesis),or whether noise leads to increased responsiveness to this“predator”(the“increased threat”hypothesis).The subjects were male barn swallows attending their breeding territories during the time when the females were incubating.We found that barn swallow males initiated fight at signifcantly greater distances to the approaching human“predator”in the noise treatment than during the quiet control trials.These results suggest that anthropogenic noise causes increased vigilance and reactivity rather than a distraction,enabling birds to avoid the“predator”more quickly.We further discuss the mechanism behind the increased alertness in response to noise and contrast the“increased threat”mechanism,usually tested in previous studies,with an alternative“cognitive sensitization”mechanism.