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1.
The theory of resource allocation assumes that a resource not allocated to one function may be reallocated to another. Thus, in hermaphroditic species, an individual that suppresses the use of one sex function may free resources for the other sex function. We determined the relative importance of male copulatory organs in terms of their fraction of the total dry body weight and tested whether in the pulmonate land slug Deroceras laeve (Müller), individuals that lack the male copulatory organs (aphallics) reallocate this resource towards the female structures and/or towards life-history traits. To this end, we raised 13 families under uniparental reproduction and compared growth, length of the juvenile period, number of eggs produced, percentage of hatched eggs and hatching time among a- and euphallics. We also measured the reproductive and sex allocation of all individuals. Six out of 13 families contained no euphallic individuals. In the other seven families, the proportion of euphallic individuals ranged from 0.13 to 0.43. There was an enormous variation in life-history traits and reproductive and sex allocation among individuals, even among individuals of the same family. Allocation to the male function was very low in euphallic slugs (i.e. 1.35% of the total body dry mass and 12.33% of the total reproductive dry mass). Our results did not reveal a reallocation from the lost male function towards the female function, nor towards one of the life-history traits. Finally, we propose a scenario that could explain the maintenance of phally polymorphism in D. laeve.  相似文献   

2.
Life-history theory predicts that parents refer to the resources they hold to determine their breeding strategy. In multi-brooded species, it is hypothesized that single-brooded parents produce larger clutches and raise offspring with a brood survival strategy, whereas multi-brooded parents only do this under good breeding conditions. Under poor conditions, they produce smaller clutches and raise offspring with a brood reduction strategy. We tested this hypothesis in the Brown-cheeked Laughing Thrush Trochalopteron henrici, which can breed twice a year on the Tibetan Plateau, by investigating the life-history traits and provisioning behaviours of single- and double-brooded parents. Single-brooded parents laid larger clutches of smaller eggs and produced more and larger fledglings than double-brooded parents in their first brood. Double-brooded parents produced smaller clutches of larger eggs but fledged larger nestlings in their first brood than in their second brood. As single-brooded parents only need to raise one brood a year, then producing and raising as many offspring as possible (i.e. the brood survival strategy in a large brood) can maximize their reproductive success. For double-brooded parents, producing and raising fewer offspring in the first brood (i.e. the brood survival strategy in a small brood) can ensure their nesting success during a short breeding cycle. Additionally, producing more offspring but raising larger nestlings in the second brood (i.e. the brood reduction strategy in a large brood) can select for offspring of higher quality within the brood. Our findings indicate that different tradeoffs between single- and double-brooded parents in egg-laying and nestling-raising may be an adaptation to the seasonal variation in environmental conditions.  相似文献   

3.
A female specific protein is found in queens, workers, and gvnandromorphsof several species of social Hymenoptera. Possibly it is presentalso in experimentally produced diploid males, but it couldnot be found in normal haploid drones. A high tiler of the femalespecific protein (vitellogenin) is found in the hemolymph ofhoneybee queens during periods of oviposition and even duringperiods when no eggs are laid. A high titer is also observedin egg-laying workers of the honeybee and the stingless bees.Rates of synthesis of vitellogenin are negatively correlatedwith the concentration in the hemolymph. In nursing workersrates of vitellogenin synthesis are twice as high as in egg-layingworkers. In non-laying workers vitellogenin normally only occurs in thehemolymph of nursing workers; this period of nursing is moreextended in A. florea than in A. mellifica, a fact which maysignal a more primitive level of female caste differentiationin A. florea. Aspects of genetic, endocrine, and social regulationof vitellogenin synthesis are discussed.  相似文献   

4.
Clutch size and malarial parasites in female great tits   总被引:4,自引:0,他引:4  
life-history models predict an evolutionary trade-off in theallocation of resources to current versus future reproduction.This corresponds, at the physiological level, to a trade-offin the allocation of resources to current reproduction or tothe immune system, which will enhance survival and thereforefuture reproduction. For clutch size, life-history models predicta positive correlation between current investment in eggs andthe subsequent parasite load. In a population of great tits,we analyzed the correlation between natural clutch size of femalesand the subsequent prevalence of Plasmodium spp., a potentiallyharmful blood parasite. Females that showed, 14 days after hatchingof the nestlings, an infection with Plasmodium had a significantlylarger clutch (9.3 eggs ± 0.5 SE, n = 18) than uninfectedfemales (8.0 eggs ± 0.2 SE, n = 80), as predicted bythe allocation trade-off. Clutch size was positively correlatedwith the prevalence of Plasmodium, but brood size 14 days afterhatching was not. This suggests that females incur higher costsduring laying the clutch than during rearing nestlings. Infectionstatus of some females changed between years, and these changeswere significantly correlated with a change in clutch size aspredicted by the trade-off. The link between reproductive effortand parasitism may represent a possible mechanism by which thecost of egg production is mediated into future survival andmay thereby be an important selective force in the shaping ofclutch size  相似文献   

5.
空心莲子草叶甲室内大量繁殖研究   总被引:3,自引:1,他引:3  
为了大量繁殖供环境释放的空心莲子草叶甲Agasicles hygrophila以实现空心莲子草区域减灾, 我们探索出室内大量饲养与繁殖空心莲子草叶甲的方法与流程, 包括用叶片法或苗水培法孵化卵粒、用盒养法饲养各龄幼虫与成虫并供成虫产卵、用栽培活苗笼养法化蛹羽化。在室内成虫终日均能取食、交配、产卵, 产卵前期约4~5 d, 产卵高峰期在羽化后第7~24 天, 每雌平均产卵21.08块, 约570粒。盒养法叶片平均可着卵4.28块, 叶背与叶面着卵量相近; 笼养法叶片平均着卵为1.46块, 卵主要产于叶背。盒养法与笼养法得到的卵孵化率分别为94.02%与92.50%。空心莲子草叶甲除化蛹需在栽培活苗上完成外, 各龄幼虫与成虫均可用离体新鲜苗盒养法密集饲养。初孵1龄幼虫转株(叶)期、3龄老熟幼虫转化蛹苗期是室内大量饲养与繁殖空心莲子草叶甲的关键时期, 高密度成功饲养与繁殖空心莲子草叶甲的最适化蛹接虫量是每株8头, 产卵期雌虫的最适密度是每株5头。  相似文献   

6.
It is generally accepted that breeding terns are sensitive to food supply and that their reproductive effort could be substantially affected by the availability and access to resources. In this study we examined reproductive parameters in the whiskered tern Chlidonias hybrida in relation to food supply during the courtship feeding period (food brought by males to females) over a 2-year period (2004–2005). We also studied whether the condition of the nestlings [body condition index (BCI)] was related to a proxy of the reproductive investment of the adults (the clutch size) during a season of food shortage. Behavioural observations showed a decrease in the intensity of male courtship feeding between years (2004 > 2005), and a strong shift in the relative abundance of the two prey groups (invertebrates/fish; invertebrate prey dropped from 88.0 to 49.3%) brought by males. This change in food delivery rates did not result in a delay in laying, but there was a significant difference in mean clutch size between years (2.71 ± 0.49 eggs in 2004 and 2.05 ± 0.78 eggs in 2005) without any within-year variation in relation to the laying dates. The egg size (volume and length) was related to the year (2004 < 2005), suggesting a trade-off in the quantity and the quality of eggs between the two seasons. We also found no evidence that the investment in a large clutch affected nestling BCI in the course of the food shortage season. Since many pairs (about 60%) interrupted breeding during the incubation stage, we assumed that parents that succeeded in rearing nestlings in these conditions were probably ‘high-quality’ individuals. Our results therefore showed that whiskered terns are sensitive to the varying food conditions they experienced throughout the courtship period. The diversity of prey types could be a key factor in the reproductive investment of this tern species.  相似文献   

7.
The seasonal appearance and the intensity of diapausing-eggproduction in Eudiaptomus graciloides in five lakes of differentsize and trophic level were studied. In all lakes, diapausingeggs were produced in autumn. In the large mesotrophic lakeSelenter See, the population’s shift to the productionof diapausing eggs was more complete than in other lakes. Weexamined day length, temperature and food as proximate factorsfor the production of diapausing eggs with laboratory experiments.Eudiaptomus graciloides produced diapausing eggs in all treatments,but a significantly higher percentage of diapausing eggs wasfound under short day conditions except when algal food wasabundant and temperature was high. To investigate the adaptivesignificance of diapause in E. graciloides, we compared thesurvival of adult and juvenile at different temperatures forE. graciloides with Eudiaptomus gracilis, a sympatric speciesthat does not exhibit diapause. At 8°C, adult E. graciloidessurvived better than adult E. gracilis and exhibited reducedgut contents and accumulation of storage lipids, traits characteristicof adult diapause. Eudiaptomus graciloides nauplii did not reachthe copepodid stage at 6°C, but E. gracilis nauplii exhibitedhigh mortality and developed very slowly. We hypothesize thatadult diapause and production of diapausing eggs facilitatethe survival of E. graciloides during cold periods and enhancecoexistence with its congener, E. gracilis, in temperate zones.  相似文献   

8.
Summary Sixty female Antarctic krill (Euphausia superba Dana) spawned in shipboard experiments and the interval between egg-laying and ecdysis was noted. The number of eggs laid per female ranged from 263–3662, most females produced only one batch of eggs before moulting, and the post-spawn ovaries of all females contained few, if any, mature oocytes. As reported in other studies, the total number of eggs produced per female was not well correlated with body size. Females appeared to spawn at all times during the moulting cycle and although no diurnal rhythm in spawning was observed, moulting occurred mainly at night-time despite the animals being kept in near-constant darkness. No evidence of synchronous moutling was detected.  相似文献   

9.
Life-history theory predicts that the trade-off between parasite defense and other costly traits such as reproduction may be most evident when resources are scarce. The strength of selection that parasites inflict on their host may therefore vary across environmental conditions. Collared flycatchers (Ficedula albicollis) breeding on the Swedish island Öland experience a seasonal decline in their preferred food resource, which opens the possibility to test the strength of life-history trade-offs across environmental conditions. We used nested-PCR and quantitative-PCR protocols to investigate the association of Haemosporidia infection with reproductive performance of collared flycatcher females in relation to a seasonal change in the external environment. We show that despite no difference in mean onset of breeding, infected females produced relatively more of their fledglings late in the season. This pattern was also upheld when considering only the most common malaria lineage (hPHSIB1), however there was no apparent link between the reproductive output and the intensity of infection. Infected females produced heavier-than-average fledglings with higher-than-expected recruitment success late in the season. This reversal of the typical seasonal trend in reproductive output compensated them for lower fledging and recruitment rates compared to uninfected birds earlier in the season. Thus, despite different seasonal patterns of reproductive performance the overall number of recruits was the same for infected versus uninfected birds. A possible explanation for our results is that infected females breed in a different microhabitat where food availability is higher late in the season but also is the risk of infection. Thus, our results suggest that another trade-off than the one we aimed to test is more important for explaining variation in reproductive performance in this natural population: female flycatchers appear to face a trade-off between the risk of infection and reproductive success late in the season.  相似文献   

10.
Early experiences, including prenatal environment, are known to influence a wide variety of mechanisms involved in the phenotype elaboration. We investigated the effect of the addition of endocrine disruptors or of a methyltransferase inhibitor during the embryonic development of quails from different genetic backgrounds (four different quail lines) on their growth and egg-laying performances. Fifty-four pairs of parents per line were used and fertilised eggs from each pair were randomly divided into five groups: a control group without any injection, an injected control group treated by injection into the egg of sesame oil, and three groups treated by injection of Genistein, Bisphenol A or 5-Aza-2′-deoxycytidine. All quails were individually weighed at 8, 21, 36 and 78 days. The age at first egg laid and the number of eggs laid were recorded. These analyses revealed a significant impact of the treatment on growth but no influence on the egg-laying traits. All three molecules significantly affected at least one of the analysed growth traits. In conclusion, we showed that the injection of endocrine disruptors or DNA methyltransferase inhibitor into the egg had significant effects on quail development; these effects were specific to each treatment, but no interaction between line and treatment was observed.  相似文献   

11.
The life-history traits and population dynamics of species are increasingly being attributed to the characteristics of their preferred habitats. While coral reef fish are often strongly associated with particular habitats, long-term studies establishing the demographic and life-history consequences of occupying different reef substrata are rare and no studies have monitored individuals in situ over their lifetime and determined the fate of their offspring. Here, we documented a quasi-turnover and local reproductive success for an entire population of orange clownfish (Amphiprion percula) from Kimbe Island, Papua New Guinea, by taking bi-annual samples of DNA over a 10-yr period (2003–2013). We compared demographic and life-history traits of individuals living on two host anemone species, Heteractis magnifica and Stichodactyla gigantea, including female size, adult continued presence (a proxy for relative longevity range), early post-settlement growth, the number of eggs per clutch and ‘local’ reproductive success (defined for each adult as the number of offspring returning to the natal population). Our results indicate that while the relative longevity of adults was similar on both host anemone species, females living in H. magnifica were larger than females in S. gigantea. However, despite females growing larger and producing more eggs on H. magnifica, we found that local reproductive success was significantly higher for clownfish living in S. gigantea. Life-history traits also exhibited local spatial variation, with higher local reproductive success recorded for adults living on S. gigantea on the eastern side of the island. Our findings support a ‘silver-spoon’ hypothesis that predicts individuals that are fortunate enough to recruit into good habitat and location will be rewarded with higher long-term reproductive success and will make a disproportionate contribution to population renewal.  相似文献   

12.
Helisoma duryi, Biomphalaria alexandrine and Bulinus truncatuswere maintained in media with seven different sodium chlorideconcentrations ranging from 0.6 to 32 mM. Growth of H. duryiwas significantly reduced only in the 32 mM NaCl treatment,while no significant effects were observed in the net reproductiverate or in egg-laying rates. Bulinus truncatus showed optimalgrowth within the range of 1 to 8 mM NaCl and the net reproductiveand egg-laying rates were reduced in the 32 mM NaCl treatment.Growth of B. alexandrina was reduced in the 16 and 32 mM NaCltreatments, while the net reproductive rate was reduced in the16 and 32 mM NaCl treatments, while the net reproductive ratewas reduced in media with more than 2.0 mM NaCl. Hatching ofB. truncatus eggs was not affected by the high NaCl concentrations,while the hatchability of H. duryi eggs was reduced in the 32mM treatment. Survival of newly-hatched H. duryi was best inthe 1 mM NaCl treatment while for B. truncatus survival wasreduced only in the 32 mM treatment. (Received 28 March 1988; accepted 7 April 1989)  相似文献   

13.
Quantifying the costs and benefits of parental care in female treehoppers   总被引:4,自引:2,他引:2  
Zink  Andrew G. 《Behavioral ecology》2003,14(5):687-693
Parental protection of eggs represents one of the most basicforms of parental care. Theory suggests that even such basicparental investment represents a trade-off between current offspringsurvival and future reproductive success. However, few studieshave quantified the underlying costs and benefits of parentalcare for marked individuals across an entire lifetime. I markedand followed 370 females of Publilia concava (Hemiptera: Membracidae)that exhibited a range of guarding durations for their firstclutch. Greater hatching success was correlated with longerguarding durations, and a removal experiment verified that femalepresence was responsible for a twofold increase in hatchingsuccess. On the other hand, females that remained to guard eggshad a lower number and size of future broods, suggesting thatparental care may reduce lifetime fecundity. Marked femalesexhibited a bimodal distribution of guarding durations, reflectingthe extreme tactics of immediate abandonment or remaining throughhatching. Estimates of lifetime number of nymphs produced byfemales that abandon eggs early versus guard eggs through hatchingrevealed roughly equivalent levels of fitness. I discuss theconditions under which we might expect a female to adopt eachof the alternative tactics, given the costs and benefits ofparental care that were quantified in this study.  相似文献   

14.
In Phytoseiulus persimilis Athias-Henriot and Amblyseius bibens Blommers a relation was found between the duration of copulation and the resultant egg production. After 15 min of copulation no eggs were produced but after respectively 30, 60 and 90 min an increasing number of eggs were deposited. In P. persimilis the total number of eggs can be produced after one copulation of long duration but in A. bibens several copulations are necessary for total egg production. Evidence was found that egg deposition depends on the quantity of sperm transferred during insemination. Relatively more males developed from eggs deposited during the first day of egg deposition but males are produced throughout the whole egg-laying period. Females of P. persimilis remain fertile throughout their life until they have deposited their total possible number of eggs. Three to 4 egg-laying periods could be induced by copulations of 30 min duration. At each period relatively more males developed from eggs laid during the first days. Males of P. persimilis were found to be very fertile. The results obtained are discussed in relation to the reproductive strategy of both species.
Zusammenfassung Bei Phytoseiulus persimilis Athias-Henriot und Amblyseius bibens Blommers wurde ein Zusammenhang gefunden zwischen Kopulationsdauer und der resultierenden Eiproduktion. Nach 15 Minuten Kopulation wurden keine Eier produziert; nach 30, 60 und 90 Minute Kopulation hingegen wurde eine steigende Zahl Eier abgelegt. Bei P. persimilis kann die totale Eizahl nach einer einzigen Kopulation von langer Dauer produziert werden, während bei A. bibens mehrere Kopulationen notwendig sind. Es wurden Anhaltspunkte gefunden, dass die Eizahl von der während der Besamung übertragenen Spermienmenge abhängt. Aus während der ersten Tage der Eiproduktion abgelegten Eiern entwickelten sich relativ mehr Männchen, doch wurden Männchen während der ganzen Eiablageperiode produziert. Weibchen von P. persimilis bleiben während ihres ganzen Lebens, bis sie alle Eier abgelegt haben, fertil. Drei bis vier Eiablageperioden konnten durch Kopulationen von 30 Minuten Dauer induziert werden. Bei jeder Periode entwickelten sich aus den in den ersten Tagen abgelegten Eiern relativ mehr Männchen. Männchen von P. persimilis erwiesen sich als sehr fertil. Die Resultate werden im Zusammenhang mit der Vermehrungsstrategie beider Arten diskutiert.
  相似文献   

15.
Conspecifics enhance egg production in an egg-carrying bug   总被引:1,自引:0,他引:1  
Variation in host availability and quality is likely to affectfemale decision making on when to lay eggs in arthropods. Inthe present study, we show a case in which female reproductionis limited by the availability of conspecifics in a speciesin which females preferably oviposit on conspecific bodies.Female golden egg bugs (Phyllomorpha laciniata; Heteroptera,Coreidae) deposit eggs mainly on the bodies of both male andfemale conspecifics. Bugs other than parents carry most eggs.Egg carrying is costly for individuals. A few eggs are laidon the bug's food plant, but in most habitats, those eggs donot survive owing to intensive ant predation. We explored ifconspecific presence affects female egg production (eggs laidand eggs in reproductive tract) in the field. In our experiment,conspecific presence (two females enclosed with food plant)increased female egg-laying rate and egg production comparedwith that of females that were alone with the food plant. Innature, gaining a conspecific host is difficult, and the encounterrate of conspecifics (i.e., operational host density) is likelyto be important for female reproduction. There are opposinginterests between an egg-laying female and the recipient (maleor female) because most eggs are dumped on individuals thatare not the parent of the eggs.  相似文献   

16.
Life-history theory posits trade-offs between fitness components. Reproduction negatively affects physiology and immune systemfunctioning, and the effect of this form of stress may be mediatedby glucocorticosteroids. We manipulated brood size of barnswallows (Hirundo rustica) to study the effect of stress arisingfrom reproductive effort on corticosterone levels of males.We also measured T-cell—mediated immunocompetence by intradermally injecting birds with phytohemagglutinin, whichis mitogenic to T-lymphocytes. The results confirmed the predictionof a negative effect of parental effort on lymphoproliferativeresponse. We found no covariation between immune response andcorticosterone levels. Males with long tails, an ornament currentlyunder directional sexual selection, had a relatively large T-cell response to the mitogen, consistent with models of parasite-mediated sexual selection predicting higher levels of immune defensein highly ornamented males. In addition, males with large sexualornaments had relatively low corticosterone levels at the endof the parental period. These results can be reconciled withthe hypothesis proposing a trade-off between parental activitiesand adaptive immunity and suggest that highly ornamented malesare less exposed or less susceptible to stress arising fromparental effort.  相似文献   

17.
Natural selection can favor songbirds that desert nests containingeggs of the parasitic brown-headed cowbird (Molothrus ater).However, the high variability in desertion of parasitized nestswithin species is perplexing in light of the typically highcosts of parasitism. Because nest desertion can also be a responseto partial clutch predation, we first asked if Bell's vireos(Vireo bellii) deserted nests in response to the presence ofcowbird eggs (antiparasite response hypothesis) or to egg removalby predators and female cowbirds (egg predation hypothesis).Second, we asked whether variation in nest desertion was dueto intrinsic differences among individuals or to variation innest contents. We monitored a large number of nests (n = 494)and performed a clutch manipulation experiment to test thesehypotheses. The number of vireo eggs that remained in a nestwas a strong predictor of desertion both within and among pairs.Neither the presence of a single cowbird egg, which leads tonest failure for this host, nor the number of cowbird eggs receivedin a vireo nest influenced nest desertion. Furthermore, vireosdid not desert experimental nests when we immediately exchangedcowbird eggs for vireo eggs but deserted if we removed vireoeggs and replaced them with cowbird eggs the following morning.Desertion of parasitized nests by Bell's vireos can be almostentirely explained as a response to partial or complete clutchloss and does not appear to have been altered by selection frombrood parasitism.  相似文献   

18.
Life-history traits such as offspring size, number and sex ratio are affected by maternal feeding rates in many kinds of animals, but the consequences of variation in maternal diet quality (rather than quantity) are poorly understood. We manipulated dietary quality of reproducing female lizards (Amphibolurus muricatus; Agamidae), a species with temperature-dependent sex determination, to examine strategies of reproductive allocation. Females maintained on a poor-quality diet produced fewer clutches but massively (twofold) larger eggs with lower concentrations of yolk testosterone than did conspecific females given a high-quality diet. Although all eggs were incubated at the same temperature, and yolk steroid hormone levels were not correlated with offspring sex, the nutrient-deprived females produced highly male-biased sex ratios among their offspring. These responses to maternal nutrition generate a link between sex and offspring size, in a direction likely to enhance maternal fitness if large body size enhances reproductive success more in sons than in daughters (as seems plausible, given the mating system of this species). Overall, our results show that sex determination in these animals is more complex, and responsive to a wider range of environmental cues, than that suggested by the classification of 'environmental sex determination'.  相似文献   

19.
This study documents substantial variation in reproductive traits among populations of stream-dwelling brown trout ( Salmo trutta L.) at a very small geographic scale. Within two streams, we found a parallel pattern of variation, where females living above major waterfalls produced fewer and larger eggs than conspecifics from below the waterfalls. Four additional streams were represented with either a below-waterfall site ( n =2) or an above-waterfall site ( n =2). When these streams were included in the analyses, there was no consistent difference in reproductive traits between females from above- and below-waterfall sites. There was no significant difference in total reproductive investment among sites within streams, but considerable variation among streams. Female first-year growth rates was estimated from scales, and differed significantly among populations. Within streams, females from below waterfalls experienced higher first-year growth rates as compared to females from above the waterfalls. Within seven out of eight populations, egg size increased significantly with increasing female body length. Within three populations, we found evidence for a trade-off between offspring size and offspring number, as a negative association between fecundity and egg size independently of adult body size. Within three populations egg size decreased significantly with increasing maternal first-year growth, independently of adult body size. We suggest that the within-stream differences in offspring size/number strategies are influenced by population density and growth effects. Earlier, we have shown that population densities are consistently lower below the waterfalls in these streams. The Alpine bullhead ( Cottus poecilopus ) is found only below the waterfalls and could influence brown trout demography.  相似文献   

20.
杨本清  窦亮  马洪  邓春国  李贵仁 《四川动物》2012,31(2):264-265,268
观察并分析了1993 ~2011年四川蜂桶寨国家级自然保护区笼养绿尾虹雉的产卵数、受精率和产卵持续天数等3个繁殖参数.结果发现,笼养绿尾虹雉的雌鸟平均产卵数为3.62枚(n=19),平均产卵天数为41.63 d(n=19),平均受精率为14.13% (n=19).与北京笼养种群相关数据比较,其产卵数、产卵持续天数没有显著差异(均P >0.05),但受精率远低于北京种群(P<0.05).  相似文献   

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