Maternal effects are long‐lasting and influence female offspring's reproductive strategy in the swordtail fish Xiphophorus multilineatus

The adaptive benefits of maternal investment into individual offspring (inherited environmental effects) will be shaped by selection on mothers as well as their offspring, often across variable environments. We examined how a mother's nutritional environment interacted with her offspring's nutritional and social environment in Xiphophorus multilineatus, a live‐bearing fish. Fry from mothers reared on two different nutritional diets (HQ = high quality and LQ = low quality) were all reared on a LQ diet in addition to being split between two social treatments: exposed to a large adult male during development and not exposed. Mothers raised on a HQ diet produce offspring that were not only initially larger (at 14 days of age), but grew faster, and were larger at sexual maturity. Male offspring from mothers raised on both diets responded to the exposure to courter males by growing faster; however, the response of their sisters varied with mother's diet; females from HQ diet mothers reduced growth if exposed to a courter male, whereas females from LQ diet mothers increased growth. Therefore, we detected variation in maternal investment depending on female size and diet, and the effects of this variation on offspring were long‐lasting and sex specific. Our results support the maternal stress hypothesis, with selection on mothers to reduce investment in low‐quality environments. In addition, the interaction we detected between the mother's nutritional environment and the female offspring's social environment suggests that female offspring adopted different reproductive strategies depending on maternal investment.     

建鲤和异育银鲫摄食不同质量饲料时的氮收支和能量收支比较

实验探讨了建鲤和异育银鲫摄食低质和高质饲料时氮和能量的收支情况.低质饲料以豆粕为主要蛋白源,饲料蛋白含量为33.91%,高质饲料以鱼粉为主要蛋白源,饲料蛋白含量为45.59%.55d的生长结果显示,氮收支和能量收支受到饲料质量和鱼类种类的显著影响:摄食低质饲料时,建鲤的生长氮和生长能比例显著低于异育银鲫,排泄氮、排泄能和代谢能比例显著高于异育银鲫;摄食高质饲料时,两种鱼的氮收支和能量收支无显著差异;建鲤的氮收支和能量收支受饲料质量的显著影响,摄食低质饲料时,其生长氮和生长能比例均显著低于摄食高质饲料时,而排泄氮、粪能和代谢能比例均显著高于摄食高质饲料时;异育银鲫的氮收支、生长能和代谢能比例不受饲料质量的显著影响.结果表明,在低质饲料条件下,建鲤利用氮和能量的能力弱于异育银鲫,在高质饲料条件下,两种鱼没有显著差异.与异育银鲫相比,建鲤利用氮和能量的能力受饲料质量的影响更为显著.       

Sex-specific patterns of yolk androgen allocation depend on maternal diet in the zebra finch

Females are predicted to adjust their reproductive investmentin relation to resource quality. In zebra finches (Taeniopygiaguttata), diet quality has been found to influence egg massboth between and within clutches. We tested the prediction thatdiet quality also affects the quantity of maternally allocatedyolk testosterone and 5-dihydrotestosterone (DHT) between andwithin clutches. We also investigated whether this pattern differedbetween male and female eggs. Females laid eggs on a high-quality(HQ) or a low-quality (LQ) diet. Eggs were removed at layingand artificially incubated for 72 h, after which time embryoswere sexed and yolk androgens assayed. Diet treatments werethen swapped and the experiment repeated. Because there wasevidence of a carry-over effect between breeding rounds, webased our conclusions mainly on the results from the first breedinground. On the HQ diet, but not on the LQ diet, infertile eggscontained more testosterone than did fertile eggs in round one.Although there were no overall differences in within-clutchpatterns of androgen deposition between the diets, this changedwhen embryo sex was taken into account. On the HQ diet, testosteronedecreased with laying sequence for male eggs but increased withlaying sequence for female eggs. On the LQ diet, mothers' maleeggs contained more testosterone and DHT than did female eggsregardless of position in the laying sequence. Our data suggestthat there are complex, context-dependent mechanisms of sex-specificandrogen allocation in this species.     

Adrenocortical responses in zebra finches (Taeniopygia guttata): individual variation, repeatability, and relationship to phenotypic quality

Although individual variation is a key requirement for natural selection, little is known about the magnitude and patterns of individual variation in endocrine systems or the functional significance of that variation. Here we describe (1) the extent and repeatability of inter-individual variation in adrenocortical responses and (2) its relationship to sex-specific phenotypic quality, such as song duration and frequency and timing of egg laying. We measured adrenocortical responses to a standardized stressor in zebra finches (Taeniopygia guttata) at two life history stages: approximately day 16 (nestlings) and 3 months of age (sexually mature adults). Subsequently, we assessed phenotypic (reproductive) quality of all individuals as adults. Marked inter-individual variation in the adrenocortical response was seen in both sexes and ages, e.g., stress-induced corticosterone ranged from 2.2 to 62.5 ng/mL in nestlings and 5.0-64.0 ng/mL in adults. We found sex differences in (a) inter-individual variation in the adrenocortical response, (b) repeatability, and (c) relationships between corticosterone levels and phenotypic quality. In males, variation in nestling corticosterone was weakly but positively correlated with brood size and negatively correlated with nestling mass (though this relationship was dependent on one individual). There was no significant correlation of adrenocortical responses between two stages in males and adult phenotypic quality was significantly correlated only with adult corticosterone levels. In contrast, in females there was no relationship between nestling corticosterone and brood size or mass but adrenocortical response was repeatable between two stages (r2=0.413). Phenotypic quality of adult females was correlated with nestling baseline and adrenocortical response.     

Inter- and intra-sexual variation in immune defence in the cabbage white butterfly, Pieris rapae L. (Lepidoptera: Pieridae)

Abstract.  1. Immune defence imposes fitness costs as well as benefits, so organisms are expected to optimise, not maximise, their immune responses. This should result in variation in immune responses under varying environmental conditions.
2. Males and females are expected to exhibit different immune responses because life-history differences between the sexes affect optimal immune response. These life-history differences should usually result in a greater female, than male, immune defence. In this study, intra- and inter-sexual variation in one component of immune defence, the encapsulation response, in cabbage white butterflies ( Pieris rapae L.), was examined.
3. Encapsulation decreased with increasing age and in response to reduced diet quality.
4. Contrary to predictions, males generally had greater immune responses than females, although this pattern varied with age.
5. These patterns of inter- and intra-sexual variation in encapsulation may result from resource-based trade-offs with components of reproductive effort and/or because of sexual dimorphism in melanin-based wing patterns.     

Lipid and fatty acid composition of eggs producing larvae with high survival rate in the Japanese eel

Eggs of Japanese eel Anguilla japonica were obtained by artificial induction of maturation. Fertilization and hatching rates, and survival rates of normal larvae were examined. The levels of total lipids and polar lipids (PL) of high quality (HQ; >80% survival rate at 8 days post-hatch) eggs were significantly lower than low quality (LQ; hatching and survival rates were zero) eggs. The docosahexaenoic acid (DHA) level in PL of HQ eggs, however, was significantly higher than in LQ eggs. In contrast to DHA, arachidonic acid level was negatively correlated with egg quality variables and it was lower in HQ than in LQ eggs. Most of the egg lipid and fatty acid components showed larger variation in LQ than in HQ eggs.     

Host plant effects on the genetic variation and correlations in the individual performance of the Gypsy Moth

1. Quantitative genetic analysis of variation in host-use ability was performed in an extremely polyphagous species – the Gypsy Moth. Various life-history traits were investigated by applying a split-family two-environment experimental design, where 30 full-sibling families were reared on oak and Locust Tree leaves.
2. Feeding on Locust Tree leaves decreased preadult viability, prolonged development time, decreased pupal mass both in males and females, and decreased reproductive effort in females.
3. The majority of broad-sense heritabilities did not change across host plants.
4. Significant expression of genetic variation in diet breadth was observed for development time and pupal mass both in males and females, but not for female reproductive effort traits. The heritabilities of plasticities were, on average, lower than heritabilities of the traits themselves.
5. The majority of genetic correlations between the host plants were significantly positive. The only trade-off was found between reciprocal value of reproductive index and the average mass of a fertilized egg within oak. This means that selection for the decrease in relative reproductive investment (under starvation during gradation) will be followed by laying larger eggs. Given that the Gypsy Moth has a cyclic population dynamics, this negative genetic correlation could have a role in maintaining genetic variability in this species.     

Variability of yolk testosterone concentrations during the reproductive cycle of Japanese quail

Deposition of yolk androgens can vary among females as well as within eggs of one female. Numerous external and internal factors can contribute to this variability. In our study, we investigated the systemic variation of yolk testosterone concentrations during the laying cycle of Japanese quail reared in stable environmental and social conditions. Testosterone was analysed in three eggs collected per female at the beginning, top and the end of a reproductive period and the extent of inter- and intra-female differences in yolk deposition of this androgen was quantified. Yolk testosterone concentrations and the yolk testosterone content decreased from the early to the latest stage of reproductive period. Testosterone concentrations in the egg yolk as well as the age-dependent pattern significantly differed among individual females. We found high repeatability of yolk testosterone among 3 eggs of individual females together with high repeatability between 3 stages of the reproductive cycle. Testosterone in the egg yolk correlated positively with eggshell weight. Our results suggest that precocial birds with long laying sequences display higher inter-female differences in yolk testosterone concentrations compared with intra-individual variability. The decreased testosterone deposition with age may influence the development and behaviour of the young hatched at different stages of the female's reproductive cycle.     

禽坦布苏病毒诱导的宿主免疫应答

禽坦布苏病毒(Avian Tembusu virus,ATMUV)是近年来在我国新发现的一种病毒,可感染多种蛋禽,感染动物临床特征为采食量下降,产蛋量骤减,甚至停产,感染后期呈神经症状,如腿和翅膀麻痹、共济失调等。ATMUV在我国多个省市地区流行,给我国甚至世界养禽业带来严重影响。固有免疫是机体抵抗病原感染的第一道重要防线,是机体与生俱来的抵御病原微生物的能力。适应性免疫是机体免疫系统在抗原刺激下产生特异性抗体及免疫效应细胞的过程,以建立针对某种病原微生物的抵抗力,是机体免疫系统的重要部分。本文将从禽坦布苏病毒诱导宿主固有免疫应答和适应性免疫应答两方面进行综述。     

Reproductive investment is connected to innate immunity in a long-lived animal

Life-history theory predicts that organisms optimize their resource allocation strategy to maximize lifetime reproductive success. Individuals can flexibly reallocate resources depending on their life-history stage, and environmental and physiological factors, which lead to variable life-history strategies even within species. Physiological trade-offs between immunity and reproduction are particularly relevant for long-lived species that need to balance current reproduction against future survival and reproduction, but their underlying mechanisms are poorly understood. A major unresolved issue is whether the first-line innate immune function is suppressed by reproductive investment. In this paper, we tested if reproductive investment is associated with the suppression of innate immunity, and how this potential trade-off is resolved depending on physiological state and residual reproductive value. We used long-lived capital-breeding female eiders (Somateria mollissima) as a model. We showed that the innate immune response, measured by plasma bacteria-killing capacity (BKC), was negatively associated with increasing reproductive investment, i.e., with increasing clutch size and advancing incubation stage. Females in a better physiological state, as indexed by low heterophil-to-lymphocyte (H/L) ratios, showed higher BKC during early incubation, but this capacity decreased as incubation progressed, whereas females in poorer state showed low BKC capacity throughout incubation. Although plasma BKC generally declined with increasing H/L ratios, this decrease was most pronounced in young females. Our results demonstrate that reproductive investment can suppress constitutive first-line immune defence in a long-lived bird, but the degree of immunosuppression depends on physiological state and age.     

Immunocompetence of Galleria mellonella: sex- and stage-specific differences and the physiological cost of mounting an immune response during metamorphosis

The antibacterial immune response of the wax moth, Galleria mellonella, was analysed by use of an inhibition zone plate assay. We demonstrated significant stage-specific differences as the immune response was most effective in the pupal, next the larval and then the adult stage. In addition, we demonstrated that an immune challenge at the onset of, or during metamorphosis does not increase nor decrease the strength of the antibacterial immune response in the subsequent developmental stage(s). These findings illustrate that induced immunity is not preserved during metamorphosis but also deny any cost to the immune system itself. However, an immune challenge does induce a significant shortening of the direct development time and affects the mass loss during metamorphosis in a sex-dependent manner: males emerged smaller whereas the mass of females was not significantly affected. These observations indicate that there are sex-specific costs to mounting an immune response during metamorphosis which affect physiological traits, implicating a trade-off between immunity and development.     

Sex-Related Effects of Reproduction on Biomarkers of Oxidative Damage in Free-living Barn Swallows (Hirundo rustica)

According to life-history theory, the allocation of limiting resources to one trait has negative consequences for other traits requiring the same resource, resulting in trade-offs among life-history traits, such as reproduction and survival. In vertebrates, oxidative stress is increasingly being considered among the physiological mechanisms forming the currency of life-history trade-offs. In this study of the barn swallow (Hirundo rustica), we focus on the oxidative costs of reproduction, especially egg laying, by investigating the effects of breeding stage (pre- vs. post-laying) and progression of the season on three biomarkers of oxidative damage (OD) to plasma proteins, namely the concentration of malondialdehyde (MDA)-protein adducts and of protein thiol groups (PSH), and the protein carbonyl (PCO) content. Moreover, we investigated whether males and females differed in plasma OD levels, because the inherent sex differences in reproductive roles and physiology may originate sex-specific patterns of OD during breeding. We found that MDA-protein adduct levels were higher in the pre-laying than in the post-laying phase, that males had lower levels of MDA-modified proteins than females, and that the decline of MDA-protein adduct concentration between the pre- and the post-laying phase was more marked for females than males. In addition, MDA-protein adduct levels declined with sampling date, but only during the pre-laying phase. On the other hand, plasma PCO levels increased from the pre- to the post-laying phase in both sexes, and females had higher levels of PCO than males. PSH concentration was unaffected by breeding stage, sex or sampling date. On the whole, our findings indicate that biomarkers of protein oxidation closely track the short-term variation in breeding stage of both male and female barn swallows. Moreover, the higher protein OD levels observed among females compared to males suggest that egg laying entails oxidative costs, which might negatively affect female residual reproductive value.     

Seasonal changes in parasite load and a cellular immune response in a colour polymorphic lizard

Permanent colour polymorphisms may be maintained by complex interactions between physiological traits (e.g. immunity) and environmental pressures. In this study we investigate morph specific variation in parasite load and cellular immune response (induced by a Phytohaemagglutinin, PHA injection) in a colour polymorphic population of the Dalmatian wall lizard (Podarcis melisellensis), where adult males have bright white, yellow or orange throats and ventral sides. Orange males have larger heads and can bite harder than the others. To examine seasonal effects, analyses were performed at an early and late stage in the reproductive season (May and September). Infection with mites and ticks did not differ among morphs, but was more severe at the end of the reproductive season. Fewer orange individuals were infected with haemogregarines at the end of the season, but white males were always more infected (higher number of haemogregarines in their blood) than other morphs. White and yellow males showed an increased PHA response towards the end of the season, but PHA response decreased in the orange morph. Finally, across all morphs, a relationship was found between ectoparasite load and PHA response. Our study provides indications of alternative life-history strategies among colour morphs and evidence for an up-regulation of the immune function at the end of the reproductive season.     

Effects of carotenoid availability during laying on reproduction in the blue tit

Carotenoids are antioxidant pigments involved in several physiological processes and signalling in animals that cannot synthesise them and therefore must acquire them from food. We experimentally investigated the effects of carotenoid availability in the diet during egg laying on antioxidant deposition in egg yolk and the related effects on nestling condition, female body condition and parental investment in the blue tit (Parus caeruleus). Carotenoid supplementation of egg-laying females resulted in a significant increase in carotenoid concentration in egg yolk, but not in vitamin E or A concentration. There was no relationship between yellow plumage colour of adult females and carotenoid deposition in eggs, and no differential effect of feeding treatment depending on female colour. Nestlings from eggs laid by carotenoid supplemented females had longer tarsi, had faster development of the immune system as reflected by leukocyte concentration in blood, and grew brighter yellow feathers than nestlings from control females. However, nestlings from the two groups did not differ significantly in body mass, plasma antioxidants or plumage colour hue. At the time of chick rearing, carotenoid-fed females had increased plasma vitamin E levels compared to controls. However, females from the two treatment groups did not differ significantly in body condition or feeding rate. These results suggest that carotenoid availability is limiting during egg laying, and that females may have to balance the benefits of investing in egg quality against the potential costs of impairing their own future antioxidant protection. In addition, there may be considerable variation in carotenoid availability not only across seasons, but also among different stages of the breeding season.     

Within‐ and between‐season repeatability of eggshell colouration in the great reed warbler Acrocephalus arundinaceus

While avian eggshell colouration has attracted biologists for decades, little is known about its variation within individuals. The main goal of this study was to explore within‐ and between‐season repeatability of eggshell appearance in the great reed warbler Acrocephalus arundinaceus. To achieve this, we measured eggshell reflectance of first and replacement clutches of individual females within one breeding season, and the reflectance of their first clutches in two following breeding seasons. As environmental conditions may affect egg colouration, repeatability was estimated from linear mixed‐effects models where we initially included temperature and rainfall during egg laying, as well as year, clutch order and egg‐laying date as fixed effects, and clutch identity nested in females as random effects. Eggshell appearance within clutches showed moderate repeatability, while both within‐ and between‐season repeatability in clutch colouration for individual females was low. Our findings indicate that low intra‐clutch variation may have a function within the context of brood parasitism, i.e. in facilitating host recognition of alien eggs. With variable eggs between successive clutches, however, host females may need to relearn the appearance of their eggs with every clutch they lay. This could represent a significant constraint for host egg‐discrimination abilities. Yet, whether environmental or intrinsic physiological factors are responsible for the variation in eggshell colouration between successive clutches of the same females still remain to be discovered.     

Consequences of metamorphosis for the locomotor performance and thermal physiology of the newt Triturus cristatus

During metamorphosis, most amphibians undergo rapid shifts in their morphology that allow them to move from an aquatic to a more terrestrial existence. Two important challenges associated with this shift in habitat are the necessity to switch from an aquatic to terrestrial mode of locomotion and changes in the thermal environment. In this study, I investigated the consequences of metamorphosis to the burst swimming and running performance of the European newt Triturus cristatus to determine the nature and magnitude of any locomotor trade-offs that occur across life-history stages. In addition, I investigated whether there were any shifts in the thermal dependence of performance between life-history stages of T. cristatus to compensate for changes in their thermal environment during metamorphosis. A trade-off between swimming and running performance was detected across life-history stages, with metamorphosis resulting in a simultaneous decrease in swimming and increase in running performance. Although the terrestrial habitat of postmetamorphic stages of the newt T. cristatus experienced greater daily fluctuations in temperature than the aquatic habitat of the larval stage, no differences in thermal sensitivity of locomotor performance were detected between the larval aquatic and postmetamorphic stages. The absence of variation across life-history stages of T. cristatus may indicate that thermal sensitivity may be a conservative trait across ontogenetic stages in amphibians, but further studies are required to investigate this assertion.     

Impact of life stage specific immune priming on invertebrate disease dynamics

The immune response of a host can have important impacts on host‐pathogen interactions, but investment in immunity often changes dynamically across the life history of a host. One form of investment involves the induction of a primed immune response against previously encountered pathogens that protects the host from re‐infection. In addition to providing immediate protective effects, immune priming can also provide two types of ‘delayed’ protection against pathogens: priming across life stages (ontogenic priming) and priming across generations (trans‐generational priming). Consequently both types of immune priming have the potential to mediate life history variability in host–pathogen interactions, which could have important consequences for disease prevalence and dynamics as well as for the demographic structure of the host population. Here we develop a stage‐structured SIRS model for an invertebrate host to explore the relative and combined impact of ontogenic priming and trans‐generational priming on infection prevalence, host population size, and population age structure. Our model predicts that both types of immune priming can dramatically reduce disease prevalence at equilibrium, but their individual and combined effects on population size and age structure depend on the magnitude of tradeoffs between immune protection and reproduction as well as on the symmetry of infection parameters between life stages. This model underscores the potential importance of life‐history based immune investment patterns for disease dynamics and highlights the need for wide‐spread empirical estimation of parameters that represent the maintenance of immune priming in insects.     

Trans‐generational immune priming is constrained by the maternal immune response in an insect

Immune‐challenged vertebrate and invertebrate females can transfer immunity to their offspring. This trans‐generational immune priming (TGIP) is beneficial for the offspring if the maternal infection risk persists across generations. However, because immunity is costly, fitness consequences of TGIP have been found in primed offspring. Furthermore, transferring immunity to offspring may be costly for immune‐challenged females who are also carrying the costs of their immune response. A negative relationship between levels of immunity between mothers and offspring might therefore be expected. Consistent with this hypothesis, we show that in the insect, Tenebrio molitor, the magnitude of antibacterial immune response of immune‐challenged females negatively correlates with levels of antibacterial activity of their eggs. This negative relationship was only present in small females that are inherently of lower quality. Furthermore, female body size did not affect immune responsiveness to the challenge, indicating that small females favoured their immunity at the expenses of that of their eggs.     

Trypsin and chymotrypsin as indicators of nutritional status of post-weaned sea bass larvae

The aim of the present work was to evaluate to what extent variation in the activity of either trypsin or chymotrypsin could be a sensitive and reliable indicator of nutritional deficiencies during post-weaning stages in a marine fish. Sea bass Dicentrarchus labrax larvae obtained from two different spawns classified as high quality (HQ) or low quality (LQ) on the basis of their hatching variables, were used to evaluate if enzyme production could be conditioned by factors other than those related to the feeding regime. In addition, larvae in each group were either fed normally or received a ration reduced by 60%. Trypsin and chymotrypsin activities were separately measured in larvae at days 3 and 15 after weaning. Changes in mass and final survival were also recorded. Food limitation resulted in a lower final mass only in the HQ larvae. Survival was significantly higher in HQ larvae, but also in larvae suffering food restriction, irrespective of the quality of the spawn. In both groups of larvae, lower food availability was correlated to increased values of trypsin, and particularly, of chymotrypsin. Variations were high enough to support the usefulness of such enzymes as indicators of a modified nutritional status. It is suggested that the noticeable increase in the activity of both enzymes observed in the restrictedly fed larvae could compensate initial deficiencies and explain the good results in growth and survival obtained in LQ larvae.     

Experimental evidence of early costs of reproduction in conspecific viviparous and oviparous lizards

Reproduction entails costs, and disentangling the relative importance of each stage of the reproductive cycle may be important to assess the costs and benefits of different reproductive strategies. We studied the early costs of reproduction in oviparous and viviparous lizard females of the bimodal reproductive species Zootoca vivipara. Egg retention time in oviparous females is approximately one-third of the time in viviparous females. We compared the vitellogenesis and egg retention stages that are common to both reproductive modes. Precisely, we monitored the thermoregulatory behaviour, the weight gain and the immunocompetence of the females. Moreover, we injected an antigen in half of the females (immune challenge) to study the trade-offs between reproductive mode and immune performance and between different components of the immune system. Finally, we experimentally induced parturition in viviparous females at the time of egg laying in oviparous females. Oviparous and viviparous females did not show strong differences in response to the immune challenge. However, viviparous females spent more time thermoregulating while partially hidden and gained more weight than oviparous females. The greater weight gain indicates that the initial period of egg retention is less costly for viviparous than for oviparous females or that viviparous females are able to save and accumulate energy at this period. This energy may be used by viviparous females to cope with the subsequent costs of the last two-third of the gestation. Such an ability to compensate the higher costs of a longer egg retention period may account for the frequent evolution of viviparity in squamate reptiles.