Are brood sex ratios adaptive?-The effect of experimentally altered brood sex ratio on nestling growth, mortality and recruitment.

Brood sex ratios (BSRs) have often been found to be nonrandom in respect of parental and environmental quality, and many hypotheses suggest that nonrandom sex ratios can be adaptive. To specifically test the adaptive value of biased BSRs, it is crucial to disentangle the consequences of BSR and maternal effects. In multiparous species, this requires cross-fostering experiments where foster parents rear offspring originating from multiple broods, and where the interactive effect of original and manipulated BSR on fitness components is tested. To our knowledge, our study on collared flycatchers (Ficedula albicollis) is the first that meets these requirements. In this species, where BSRs had previously been shown to be related to parental characteristics, we altered the original BSR of the parents shortly after hatching by cross-fostering nestlings among trios of broods and examined the effects on growth, mortality and recruitment of the nestlings. We found that original and experimental BSR, as well as the interaction of the two, were unrelated to the fitness components considered. Nestling growth was related only to background variables, namely brood size and hatching rank. Nestling mortality was related only to hatching asynchrony. Our results therefore do not support that the observed BSRs are adaptive in our study population. However, we cannot exclude the possibility of direct effects of experimentally altered BSRs on parental fitness, which should be evaluated in the future. In addition, studies similar to ours are required on various species to get a clearer picture of the adaptive value of nonrandom BSRs.

The interactive effect of ambient temperature and brood size manipulation on nestling body mass in blue tits: an exploratory analysis of a long-term study.

BACKGROUND: Relatively few studies have examined the interactive effects of ecological factors on physiological responses in wild animals. Nearly all of them have been short-term investigations that did not include experimental manipulations, limiting our ability to understand how climate change will affect natural populations. Using a 10-year brood size manipulation experiment in wild blue tits (Cyanistes caeruleus), we quantified the impact of weather conditions and brood competition on the body mass and structural size (tarsus length) of nestlings just prior to leaving the nest. RESULTS: We found that variation in nestling body mass on day 14 after hatching was explained by an interactive effect between average ambient temperature experienced during nestling period and brood size treatment. Specifically, in control broods nestling body mass was correlated with temperature in a non-linear manner (concave) with the vertex point (maximum body mass) at ca. 13 °C. In contrast, in enlarged broods nestling body mass permanently increased (also non-linearly) as temperature advanced. CONCLUSIONS: Our results highlight the importance of considering the effects of brood rearing conditions alongside other environmental factors experienced during growth while investigating early-life environmental effects on body condition.

Neglecting larval rearing conditions in Drosophila melanogaster can negatively impact research on ageing.

The developmental conditions of Drosophila melanogaster flies can modify the phenotypic traits of adults. However, the control of these conditions is neglected by some authors in their articles and the readers are unaware, for instance, whether flies developed in crowded cultures or fed on a new or used medium. Controlling developmental conditions allows to know precisely the viability of flies, their duration of development and sex-ratio, which can be warning signals of bad rearing conditions. As developmental conditions can modify the results of experiments on the effects of ageing it is necessary to strictly control them.

Modulations of lipid metabolism and development of the Atlantic salmon (Salmo salar) fry in response to egg-to-fry rearing conditions.

In stocking program, the use of artificial incubation conditions in hatcheries from the fertilisation of eggs to the release of unfed fry could reduce their ability to adapt to the natural environment. This study evaluates the effects of three factors on the fitness and physiology of salmon fry at their emergence, the origin of water (river vs drilling), the type of support in the incubator (support matrix vs plastic sheets) and the type of incubators (Californian vs vertical trays), and compares them to a semi-natural incubation method in river. Key biological functions including nutritional and immune status were compared among experimental conditions using biometric parameters, lipid composition and gene expression analyses. Our findings demonstrated that fry incubated in vertical trays supplied with river water had no significant difference in growth and lipid composition compared to those in semi-natural incubators. Besides, fry incubated on a substrate matrix in Californian trays exhibited phenotypic characteristics closest to those incubated in river. This support matrix improved fish growth, lipid consumption and distribution compared to fry on plastic sheets. Moreover, the large amounts of several PUFAs in these fry could allow a better membrane fluidity ensuring a better adaptation to temperature variation under cold conditions. In addition, drilling water improved the survival rate compared to river water due to lower numbers of fine particles, known to be responsible for the clogging of eggs. To conclude, using a substrate combined with drilling water in artificial incubators could increase fry fitness and its adaption to wild life.

Differential effects of early growth conditions on colour-producing nanostructures revealed through small angle X-ray scattering and electron microscopy.

The costs associated with the production and maintenance of colour patches is thought to maintain their honesty. Although considerable research on sexual selection has focused on structurally coloured plumage ornaments, the proximate mechanisms of their potential condition dependence, and thus their honesty, is rarely addressed, particularly in an experimental context. Blue tit (Cyanistes caeruleus) nestlings have ultraviolet (UV)-blue structurally coloured tail feathers, providing a unique opportunity for investigation of the causes of variation in their colour. Here, we examined the influence of early growing conditions on the reflectance and structural properties of UV-blue-coloured tail feathers of blue tit nestlings. We applied a two-stage brood size manipulation to determine which stage of development more strongly impacts the quality of tail feather colouration and microstructure. We used small-angle X-ray scattering (SAXS) and electron microscopy to characterise the nanoscale and microscale structure of tail feather barbs. Nestlings from the broods enlarged at a later stage of growth showed a sex-specific rectrix development delay, with males being more sensitive to this manipulation. Contrary to predictions, treatment affected neither the quality of the barbs' nanostructures nor the brightness and UV chroma of feathers. However, at the microscale, barbs' keratin characteristics were impaired in late-enlarged broods. Our results suggest that nanostructure quality, which determines the UV-blue colour in tail feathers, is not sensitive to early rearing conditions. Furthermore, availability of resources during feather growth seems to impact the quality of feather microstructure more than body condition, which is likely to be determined at an earlier stage of nestling growth.

Preliminary investigation of an idiopathic muscle disease in farmed burbot Lota lota.

The rearing of less established fish species in recirculating aquaculture systems (RASs) is increasing, but may require adaptations of the rearing facilities if health impairments occur. We observed several health issues in burbot Lota lota reared for up to 2 yr in a RAS and used microbiological, histological and molecular-biological methods to identify the causative agents. Minor skin trauma led to the development of ulcers. In addition, several fillets of burbot showed pronounced granulomatous inflammation and calcification with signs of muscle fiber degeneration which resembled a condition called 'sandy flesh disease' in North American walleye. Several infectious agents were able to be excluded as a cause for the disease. Carnobacterium maltaromaticum was isolated in high numbers in some of the affected muscle tissue. However, the role of this bacterium or other causative agents or husbandry conditions remains to be elucidated.

Reproductive performance in generalist haematophagous ectoparasites: maternal environment, rearing conditions or both?

We tested whether and how the maternal environment (i.e. host species exploited by a mother), rearing conditions (i.e. host species exploited by her offspring) or both (i.e. matches and mismatches in host species exploited by a mother and her offspring) affect reproductive performance in the offspring. We experimentally manipulated maternal and rearing environments in two generalist fleas (Xenopsylla conformis and Xenopsylla ramesis) implementing a factorial cross-rearing design. Mothers exploited either the principal host (PH) or auxiliary hosts that were either closely (CAH) or distantly related (DAH) to the PH. After six generations of infesting a given host species, we cross-reared fleas within and between host species. These fleas reproduced and we measured their reproductive performance both quantitatively (i.e. egg number) and qualitatively (i.e. egg size, development time, body size of the next generation). We found that identity of the host a flea was reared on (=actual host) had the strongest effect on its performance. Individuals reared on the PH performed considerably better than those reared on either auxiliary host. Moreover, fleas reared on a CAH performed better than those reared on a DAH. Actual host identity also had a stronger effect on reproductive performance in X. ramesis than in X. conformis. Nevertheless, there was no difference in performance between match and mismatch maternal and actual host identities. We conclude that rearing environment has the strongest effect on fitness in generalist parasites. Moreover, phylogenetic distance between an auxiliary host and the PH determines the level of suitability of the former.

Review of rearing-related factors affecting the welfare of laying hens.

Laying hens may face a number of welfare problems including: acute and chronic pain caused by beak trimming; exaggerated fearfulness that may cause stress and suffocation; difficulties in locating resources, resulting potentially in emaciation and dehydration; frustration and boredom, caused by an environment that is barren; feather pecking; cannibalism; foot lesions; and bone fractures. In Europe, a greater proportion of laying hens are housed in non-cage systems compared to the rest of the world. The extent of the different welfare problems may therefore vary between countries as the type of housing system influences the risk of suffering. More generally, many of these welfare problems are influenced by the rearing environment of the pullets. This article therefore focuses on welfare problems in laying hens that can be traced back to rearing. Factors that have been studied in relation to their effects on bird welfare include beak trimming, housing type, furnishing, enrichment, feeding, stocking density, flock size, sound and light levels, concentration of gasses, age at transfer from rearing to production facilities, similarity between rearing and production facilities, competence of staff, and interactions between bird strain and environment. The present review aims to summarize rearing-related risk factors of poor welfare in adult laying hens housed according to European Union legislation. It aims to identify gaps in current knowledge, and suggests strategies for improving bird welfare by improving rearing conditions. Two main conclusions of this work are that attempts should be made to use appropriate genetic material and that beak trimming should be limited where possible. In addition to this, the rearing system should provide constant access to appropriate substrates, perches, and mashed feed, and should be as similar as possible to the housing system used for the adult birds. Finally, young birds (pullets) should be moved to the production facilities before 16 weeks of age. The measures outlined in this review may be useful for improving the welfare of pullets and adult laying hens.

Validation of daily microincrement deposition in otoliths of juvenile and adult Peruvian anchovy Engraulis ringens.

Wild adult specimens of the Peruvian anchovy Engraulis ringens were captured and reared to validate the daily periodicity of otolith microincrement formation. The postcapture stress generated spontaneous spawning, making it possible to conduct a rearing trial on larvae first in an artificial nutrient-enriched system (ANES) for 52 days followed by an artificial feeding regime in a culture tank until day 115 post-hatch. Microincrements of the sagittal otoliths of sacrificed juveniles [mean ± S.D. total length (LT ) = 5·13 ± 0·37 cm, range 5-6 cm; c.v. = 7·5%] showed very distinct light and dark zones. The slope of the relationship between the total number of increments after the hatch check and days elapsed after hatching was not significantly different from 1. The transfer from ANES to the artificial feeding regime induced a mark in the sagittal otoliths. The number of microincrements after this induced mark coincided with the number of days elapsed after the transfer date. In parallel experiments, adult E. ringens (mean ± S.D. LT = 14·92 ± 0·55 cm, range 13-16 cm) were exposed to one of two fluorescent marking immersion treatments with either alizarin red S (ARS; 25 mg l(-1) per 6 h) or oxytetracycline hydrochloride (OTC; 200 mg l(-1) per 10 h). The microincrements between fluorescent bands were distinct, ranging from 0·89 to 2·75 µm (mean ± S.D. =1·43 ± 0·28 µm; c.v. = 32%) and from 0·71 to 2·89 µm (1·53 ± 0·27 µm; c.v. = 35%) for ARS and OTC, respectively. The relationship between the number of microincrements between marks and the number of elapsed days for ARS and OCT treatments indicated that there was a significant correspondence between the number of increases observed and the number of days. Hence, daily microincrements of otoliths of E. ringens are likely to be formed in juveniles and adults under natural conditions.

Review: Production factors affecting poultry carcass and meat quality attributes.

Poultry meat mainly comes from standard production system using high growth rate strains reared under indoor intensive conditions. However, it is possible to find also different alternative systems using outdoor extensive rearing conditions and slow-growing lines. These different production systems can affect carcass and meat quality. In this review, quality has been broken down into six properties: commercial, organoleptic, nutritional, technological, sanitary and image, the latter covering the ethical, cultural and environmental dimensions associated with the way the meat is produced, as well as its origin and being particularly valued in many quality labels. The quality of meat is built and can deteriorate along the continuum from the conception of the animal to the fork. Our review details the different factors implicated in the determinism of poultry meat properties and pinpoints critical periods, such as the preslaughter and slaughter periods, and key factors, such as the feeding regimen, via its direct effect on the fatty acid profile, the antioxidant and volatile compound contents, and indirect effects mediated via the growth rate of the bird. Our review also highlights potential antagonisms between different dimensions of quality. The genetic selection for breast meat yield, for example, has been effective in producing carcasses with higher meat yield, but resulting since a decade in the increased occurrence of quality defects and myopathies (white striping, wooden breast, spaghetti meat and deep pectoral disease). Outdoor access has positive effects on the image and nutritional properties (through its effect on the fatty acid profile of meat lipids), but it increases the exposition risk to environmental contaminants and pathologies (parasites, virus, bacteria); it also increases the variability in meat quality linked to the variability of animal performance and slaughter age. The orientation towards more agro-ecological low-input farming systems may present benefits for the image and nutritional properties, but also risks for the commercial (low carcass weight and low breast yield, irregularity in supply), organoleptic (stronger flavour, less tender and darker colour of the meat) and in terms of variability of the different properties that constitute quality. Efforts should be made in the future to better take into account the various dimensions of quality, in consumer information, payment to farmers and genetic selection.

Productional data of primiparous dairy cows reared in different social environments during the first 8 weeks after birth.

This paper is composed of 5 datasets describing primiparous milk production, reproduction, body weight, activity and whole life longevity and reproductional data in dairy cows that had been reared either with or without mother for the first four days after birth and either in single housing or housing in groups of four between 1 and 8 weeks of age. The datasets contain the following variables- survival to the first lactation, date of first successful insemination, milk parameters per day (such as sum of milk yield, milk electrical conductivity and milking time), activity and body weight, all these collected during the first standardized lactation of 305 days. Cows' longevity, reproduction and other management events were recorded during the whole life of experimental animals (such as inseminations, pregnancy diagnostics, group changes etc.). Calves' body weight was measured first 12 weeks of life of the experimental animals. The data include the information about the type of housing (with or without mother, individual vs group housing) in the early ontogeny period and two different breeds (Holstein and Czech Fleckvieh). Data on the milk parameters, body weight and activity were collected twice a day by commercially used precision dairy monitoring technologies. Data on survival to the first lactation, longevity, first successful insemination and other events were recorded by farm managers on farm basis. Data on body weight of animals during early ontogeny were taken after birth, at 4 d of age, at 7 d of age, and then weekly until 12 weeks of age. The data can be used for further analyses of the influence of parameters from early ontogeny on cow performance, especially during the first lactation. This information can be useful for researchers and other stakeholders investigating the influence of early ontogenetic social environment on the dairy cattle performance and welfare.

Effect of Type of Cow-Calf Contact on Health, Blood Parameters, and Performance of Dairy Cows and Calves.

Prolonged cow-calf contact (CCC) could potentially improve dairy calf welfare. However, it is currently unknown how different types of CCC affect animals' biological functions. We evaluated health and performance parameters of dairy calves and their dams, where calves: (i) had no contact with their dam (NC), in which the calf was removed from the dam directly after birth (n = 10); (ii) were allowed to have partial contact (PC) with their dam, in which the calf was housed in a calf pen adjacent to the cow area allowing physical contact on the initiative of the dam but no suckling (n = 18); (iii) were allowed to have full contact (FC) with their dam, including suckling, in which calves were housed together with their dams in a free-stall barn (n = 20). Throughout the first 7 weeks postpartum, data were collected on the health status, fecal microbiota, hematological profile, immune and hormonal parameters, and growth rates of calves, and on the health status, metabolic responses, and performance of dams. Overall, FC calves had more health issues (P = 0.02) and a tendency for higher antibiotic usage (P = 0.07) than NC calves. Additionally, FC calves showed elevated levels of erythrocytes, hematocrit, hemoglobin, and leukocytes on day 49 compared to NC calves (P < 0.001). Calf fecal microbiota changed over time, and we found preliminary evidence that fecal microbiota is affected by the type of CCC, as reflected by differences in relative abundances of taxa including Lactobacillus in FC calves compared to NC and PC calves except on days 7 and 66. The FC calves had a greater average daily gain in body weight than NC and PC calves (P = 0.002). Cow health was not affected by the type of CCC, although in the first 7 weeks of lactation FC cows had a lower machine-gained milk yield accompanied by a lower fat percentage than NC and PC cows (P < 0.001). These results indicate that full contact posed a challenge for calf health, presumably because the housing conditions of FC calves in this experimental context were suboptimal. Secondly, ad libitum suckling leads to higher weight gains and negatively affected milk fat content besides machine-gained yields. More research into strategies to improve cow-calf housing and management in CCC systems is warranted.

The fear hypothesis and tonic immobility (TI) modulation: Early studies in chickens.

The hypothesis that fear is involved in the mechanisms of tonic immobility (TI) has been supported by early studies conducted in newborn and adult chickens. The susceptibility to TI changes during development in parallel to other fear responses. TI duration increases following exposure before induction to threatening stimuli such as electric shock, loud sound, stuffed sparrow hawk, as well as in unfamiliar conditions applied before and/or during testing. TI duration and susceptibility are increased by prey/predator eye contact and inversely related with the predator distance. TI duration increases following exposure before induction to threatening stimuli such as electric shock, loud sound, stuffed sparrow hawk, as well as in unfamiliar conditions applied before and/or during testing. The fact that the experimenter presence or the experimenter eye visibility represent a potential source of fear like a natural predator in chicks and in adult hens is controversial. The likely explanations for the contradictory results are discussed in the text. The rearing conditions, for instance, seem to be critical: repeated handling in the first days after hatching reduces the fear of human beings, decreasing TI duration in adulthood with a parallel increase in proximity scores to the experimenter. In chicks, exposure to withdrawal from a positive imprinting stimulus increases and decreases TI duration, respectively.

Characterization of life-history parameters of an Anopheles funestus (Diptera: Culicidae) laboratory strain.

The colonization of the African malaria vector Anopheles funestus has been hampered by inadequate knowledge of its mating and development under laboratory conditions. Life-tables are routinely used to provide baseline biological characteristics needed for colonization. This study characterized age-specific life-table attributes of an existing An. funestus laboratory strain to gain insight into factors that are critical for its colonization. To achieve this, the An. funestus laboratory strain was reared from eggs to adulthood under standard insectary conditions, monitoring and characterizing each developmental stage. The mean insemination rate of females was 74.8% with an average egg load of 67.1 eggs/female and a mean fertility of 86.7%. The mean developmental time from 1st instar larvae (L1) to pupation was 16.4 days. The mean proportion of L1 that survived to pupation was 72.9%. On average, 78.8% of the pupae successfully eclosed as adults. The median longevity for adult males and females was 44 and 28 days, respectively. This work constitutes the first report on life-table characterization of an An. funestus strain. The larval developmental time was within the range reported for wild An. funestus while adult longevity was higher compared to survivorship observed in wild populations. These data demonstrate that the colonized An. funestus strain has potential to be re-colonized under standard insectary conditions. The study provides base-line information for further studies on identifying critical parameters for the maintenance of An. funestus under artificial conditions.

Effects of Sex and Group Size on Behavior and Brain Biogenic Amines in Short-Lived Turquoise Killifish (Nothobranchius furzeri).

Short-lived turquoise killifish (Nothobranchius furzeri) becomes a popular model species for neuroscience. However, the effects of sex and rearing conditions on behavior and brain monoamines in N. furzeri are unknown. In this article, we study the body mass, behavior in the novel tank diving test, levels of noradrenaline (NA), dopamine (DA), serotonin (5-HT), 3,4-dihydroxyphenylacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5-HIAA) in the brain of 108 day-old N. furzeri males and females reared in small (one male and one or two females in 4-L tanks) and large (four males and four females in 25-L tanks) groups. Males were heavier and had a lower NA level in the brain compared with females. The behavior of males and females did not differ in the novel tank diving test. Their DA, 5-HT, DOPAC, and 5-HIAA levels in the brain did not differ too. Males from small groups spent more time near the tank's bottom. Rearing in small groups reduced the DA level in the female brain and the DOPAC level in female and male brains. However, group size did not affect body mass, 5-HT and 5-HIAA levels in the brain. Thus, group size is important for behavior and neuroscience studies of N. furzeri.

Differential DNA methylation in somatic and sperm cells of hatchery vs wild (natural-origin) steelhead trout populations.

Environmental factors such as nutrition, stress, and toxicants can influence epigenetic programming and phenotypes of a wide variety of species from plants to humans. The current study was designed to investigate the impacts of hatchery spawning and rearing on steelhead trout (Oncorhynchus mykiss) vs the wild fish on a molecular level. Additionally, epigenetic differences between feeding practices that allow slow growth (2 years) and fast growth (1 year) hatchery trout were investigated. The sperm and red blood cells (RBC) from adult male slow growth/maturation hatchery steelhead, fast growth/maturation hatchery steelhead, and wild (natural-origin) steelhead were collected for DNA preparation to investigate potential alterations in differential DNA methylation regions (DMRs) and genetic mutations, involving copy number variations (CNVs). The sperm and RBC DNA both had a large number of DMRs when comparing the hatchery vs wild steelhead trout populations. The DMRs were cell type specific with negligible overlap. Slow growth/maturation compared to fast growth/maturation steelhead also had a larger number of DMRs in the RBC samples. A number of the DMRs had associated genes that were correlated to various biological processes and pathologies. Observations demonstrate a major epigenetic programming difference between the hatchery and wild natural-origin fish populations, but negligible genetic differences. Therefore, hatchery conditions and growth/maturation rate can alter the epigenetic developmental programming of the steelhead trout. Interestingly, epigenetic alterations in the sperm allow for potential epigenetic transgenerational inheritance of phenotypic variation to future generations. The impacts of hatchery exposures are not only important to consider on the fish exposed, but also on future generations and evolutionary trajectory of fish in the river populations.

Effects of Rearing Conditions and Sex on Cecal Microbiota in Ducks.

The intestinal microbiome influences the health of animals. However, little is known about the impact of indoor conditions and sex on intestinal microbiome diversity and composition in ducks. The present study aimed to investigate differences in the cecal microbiome between male and female ducks reared on the floor (PY group) or in cages (LY group). We also determined the relationships between cecal microbiota composition and slaughter traits, and the expression levels of mucosal and intestinal structural genes in ducks. There was a slight difference in slaughter traits among the groups, with cecum weight being significantly lighter in the LY compared with the PY group, especially in females (p < 0.05). Analysis of the alpha diversity of the cecal microbiota between males and females in the LY and PY groups showed that LY males had significantly lower diversity and richness. Beta diversity analysis demonstrated differences in the microbiota composition in relation to rearing conditions, and a significant difference between the sexes in the PY groups. The dominant bacterial phyla in duck cecum were Bacteroidetes, Firmicutes, Proteobacteria, and Fusobacteria. The relative abundances of the most common bacteria revealed that the intestinal microbiota diversity and composition were affected by both feeding conditions and sex. Several bacterial genera were detected differentially among the groups. These genera were correlated with slaughter traits and expression levels of mucosal and cecal structural genes in ducks. In conclusion, rearing conditions, sex, and associated changes in the cecal microbiota are thus associated with gut barrier functions in ducks.

Skeletal Anomalies in Senegalese Sole (Solea senegalensis, Kaup) Fed with Different Commercial Enriched Artemia: A Study in Postlarvae and Juveniles.

The high incidence of skeletal anomalies in Senegalese sole (Solea senegalensis) still constitutes a bottleneck constraining its production. There are diverse commercially available products for the enrichment of live preys, but few reports of their influence on skeletogenesis in Senegalese sole. This study evaluated the presence of vertebral anomalies in postlarvae and juvenile Senegalese sole fed with Artemia spp. metanauplii enriched with four commercial products (EA, EB, EC, and ED) in a fish farm. The most frequent alterations consisted of deformations of the neural/haemal arches and spines and fusions and deformations of hypurals, epural, or parhypural. The correspondence analysis ordered fish from each age in separated semiaxis, indicating the presence of different anomaly patterns for the two sampled stages. The results showed only very light changes in the frequency of vertebral abnormalities among tested enrichment products, i.e., individuals from EC and EA lots displayed less vertebral body anomalies and/or vertebral column deviations at 31 and 105 days after hatching, respectively. The existence of a large shared malformation pattern in all the experimental groups leads to impute to the rearing conditions as the main driving factor of the onset of such group of anomalies, probably masking some dietary effect.

Two experimental designs generate contrasting patterns of behavioral differentiation along a latitudinal gradient in Lestes sponsa-Common-garden not so common after all?

Understanding why and how behavioral profiles differ across latitudes can help predict behavioral responses to environmental change. The first response to environmental change that an organism exhibits is commonly a behavioral response. Change in one behavior usually results in shifts in other correlated behaviors, which may adaptively or maladaptively vary across environments and/or time. However, one important aspect that is often neglected when studying behavioral expressions among populations is if/how the experimental design might affect the results. This is unfortunate since animals often plastically modify their behavior to the environment, for example, rearing conditions. We studied behavioral traits and trait correlations in larvae of a univoltine damselfly, Lestes sponsa, along its latitudinal distribution, spreading over 3,300 km. We compared behavioral profiles among larvae grown in two conditions: (a) native temperatures and photoperiods or (b) averaged constant temperatures and photoperiods (common-garden). We hypothesized latitudinal differences in behavioral traits regardless of the conditions in which larvae were grown, with northern populations expressing higher activity, boldness, and foraging efficiency. When grown in native conditions, northern larvae were bolder, more active and more effective in prey capture than central and low latitude populations, respectively, as well as showed the strongest behavioral correlations. In contrast, larvae reared in common-garden conditions showed no differences between regions in both individual traits and trait correlations. The results suggest different selective pressures acting on the studied traits across populations, with environment as a central determinant of the observed trait values. Common-garden designed experiments may evoke population-dependent levels of plastic response to the artificial conditions and, hence, generate results that lack ecological relevance when studying multi-population differences in behavior.

Social behavior in dog puppies: Breed differences and the effect of rearing conditions.

INTRODUCTION: Most of the studies investigating the effect of early rearing environment in dogs used laboratory dogs and reported that early experiences markedly affect the puppies' behavior. However, the subjects of these experiments cannot be considered as representatives of family dogs. METHODS: In this study, we investigated whether different raising conditions shape social behavior toward humans in 8-week-old family dog puppies of two breeds, Labrador and Czechoslovakian wolf dog. The puppies were tested in a series of tests that represented typical situations of family dogs. RESULTS: We found that Czechoslovakian wolf dog puppies were more active than Labrador puppies in general, as they were more likely to explore the environment and the objects and spent more time doing so. Tendency to gaze at humans also varied between breeds, but in a context-specific way. Additionally, puppies housed separately from their mother interacted more with toys, puppies housed in a kennel tended to stay closer to the experimenter than puppies raised in the house, and puppies housed in a kennel tended to stay in the proximity of the experimenter more than puppies raised in the house. CONCLUSIONS: Our results provide evidence for early keeping conditions influencing social behavior and also highlight breed differences in puppies' behavior. Whether these differences are due to different developmental patterns and/or behavioral predispositions remains to be explored.