Environmental stress linked to consumption of maternally derived carotenoids in brown trout embryos (Salmo trutta)

The yellow, orange, or red colors of salmonid eggs are due to maternally derived carotenoids whose functions are not sufficiently understood yet. Here, we studied the significance of naturally acquired carotenoids as maternal environmental effects during embryo development in brown trout (Salmo trutta). We collected eggs from wild females, quantified their egg carotenoid content, fertilized them in vitro in full‐factorial breeding blocks to separate maternal from paternal effects, and raised 3,278 embryos singly at various stress conditions until hatching. We found significant sire effects that revealed additive genetic variance for embryo survival and hatching time. Dam effects were 5.4 times larger than these sire effects, indicating that maternal environmental effects play an important role in determining embryo stress tolerance. Of the eight pigment molecules that we targeted, only astaxanthin, zeaxanthin (that both affected egg redness), and lutein were detected above our confidence thresholds. No strong link could be observed between carotenoid content in unfertilized eggs and embryo mortality or hatching timing. However, the consumption of carotenoids during our stress treatment was negatively correlated to embryo survival among sib groups and explained about 14% of the maternal environmental variance. We conclude that maternally derived carotenoids play a role in the ability of embryos to cope with environmental stress, but that the initial susceptibility to the organic pollution was mainly determined by other factors.     

The embryo pancreas is a source of increased yolk amylase in the fertilized eggs of domestic fowls.

The amylases were studied in the yolk of fertilized eggs and in the pancreases of the embryos of domestic fowls. The amylase activity in the yolk increased markedly from 13 days of incubation until hatching, but the activity decreased when the embryos were taken out of the eggs. The isoamylases in the yolk and in the pancreas of the embryo were identical electrophoretically. The amylase occurs mainly in the pancreas of the embryo. We think that the increase in amylase activity in the yolk of fertilized eggs during incubation depends upon the accumulation of pancreatic amylase synthesized by the developing embryo in the egg.     

Diversity and stability of egg‐bacterial assemblages: The role of paternal care in the glassfrog Hyalinobatrachium colymbiphyllum

Embryos of oviparous organisms must cope with harsh environments and are especially susceptible to disease, considering that many immune mechanisms do not develop until later in life. Parents may transmit symbiotic microflora to eggs, which can contribute to embryo immune defense. Despite the importance of symbiotic microbes for immune function and survival of adult amphibians, vertical transfer of symbionts in amphibians has received less attention than in other taxa. Here, we test the role of male‐only parental care in establishing and maintaining the diversity of egg‐bacterial assemblages in a Neotropical glassfrog (Centrolenidae). Previous research suggests that father Hyalinobatrachium colymbiphyllum may transfer bacterial symbionts to their eggs. We combined a male‐removal experiment in situ with 16S rRNA gene amplicon sequencing to determine whether egg attendance by father H. colymbiphyllum influences the bacterial community and survival of eggs. We found that eggs harbor a diverse and stable bacterial assemblage. Despite different host environments, we found that adult skin and eggs supported very similar bacterial assemblages—even after removing fathers. While we found overlap in the bacteria present on eggs and their fathers, our experiment reveals that extended male care does not contribute to the maintenance of egg‐bacterial communities, so there may be other potential routes of transfer. This study contributes to our understanding of the diversity and maintenance of egg microbiomes, and motivates further research on how initial bacteria are acquired and the ontogenetic development of host–symbiont communities.     

The role of biogeography in shaping diversity of the intestinal microbiota in house mice

The microbial communities inhabiting the mammalian intestinal tract play an important role in diverse aspects of host biology. However, little is known regarding the forces shaping variation in these communities and their influence on host fitness. To shed light on the contributions of host genetics, transmission and geography to diversity in microbial communities between individuals, we performed a survey of intestinal microbial communities in a panel of 121 house mice derived from eight locations across Western Europe using pyrosequencing of the bacterial 16S rRNA gene. The host factors studied included population structure estimated by microsatellite loci and mitochondrial DNA, genetic distance and geography. To determine whether host tissue (mucosa)‐associated communities display properties distinct from those of the lumen, both the caecal mucosa and contents were examined. We identified Bacteroides, Robinsoniella and Helicobacter as the most abundant genera in both the caecal content and mucosa‐associated communities of wild house mice. Overall, we found geography to be the most significant factor explaining patterns of diversity in the intestinal microbiota, with a comparatively weaker influence of host population structure and genetic distance. Furthermore, the influence of host genetic distance was limited to the mucosa communities, consistent with this environment being more intimately coupled to the host.     

Development and the influence of nurse egg allotment on hatching size in Searlesia dira (Reeve, 1846) (Prosobranchia : Buccinidae)

The reproductive biology of the intertidal prosobranch Searlesia dira (Reeve, 1846) was examined with special attention given to variability in the nurse egg to embryo ratio among capsules, among clutches and among geographically isolated populations. Embryos and nurse eggs were distributed among the capsules in a manner consistent with the hypothesis that nurse eggs were genetically predetermined, that each female had a genetically defined nurse egg to embryo ratio, and that each capsule represented a random sample of that ratio. The binomial distribution of embryos and nurse eggs among the capsules resulted in some capsules receiving many more embryos per nurse egg than others. The number of nurse eggs an embryo succeeded in eating was proportional to the number of capsule-mates sharing a capsule. Embryos eating more nurse eggs hatched out at a larger size. Differences in the nurse egg to embryo ratios among capsules in the same clutch were much larger than that of the mean ratios among clutches. Among-site differences in the mean nurse egg to embryo ratios suggest that selection pressure for different mean hatching sizes may have acted on the mean nurse egg to embryo ratios.In contrast to the predictions of optimal hatching size theory, hatching size varied widely within clutches as a consequence of differences in nurse egg to embryo ratios among capsules. This variance may be adaptive for species that lay their eggs months before juveniles emerge into an unpredictable environment, or simply be a consequence of an imperfect mechanism for increasing hatching size.     

Role of maternal provisioning in controlling interpopulation variation in hatching size in the marine snail Nucella ostrina

This study examined the role of maternal provisioning in controlling interpopulation variation in hatching size in nine isolated populations of the intertidal gastropod Nucella ostrina, in which development to the early juvenile stage takes place within an egg capsule. Variation among populations was almost entirely due to the ratio of nurse eggs to embryo, which explained 65% of the variation in hatching size. Egg size was not a significant predictor of hatching size. Differences among seven of these populations in the nurse egg/embryo ratio were entirely due to the number of nurse eggs allocated per capsule; these populations allocated different numbers of nurse eggs per capsule but allocated the same number of embryos. Intriguingly, the two most wave-sheltered populations allocated significantly more nurse eggs and more embryos to each capsule than did the seven other populations, but they maintained nurse egg/embryo ratios consistent with patterns observed in the other populations. Inter- and intrapopulation variation in hatching size appears to be controlled largely by different mechanisms: within-population variation being controlled mainly by differences in allocation of embryos per capsule, whereas most among-population variation being due to differences in allocation of nurse eggs per capsule.     

Dynamics of bacterial and fungal communities associated with eggshells during incubation

Microorganisms are closely associated with eggs and may play a determinant role in embryo survival. Yet, the majority of studies focusing on this association relied on culture‐based methodology, eventually leading to a skewed assessment of microbial communities. By targeting the 16S rRNA gene and internal transcribed spacer (ITS) region, we, respectively, described bacterial and fungal communities on eggshells of the homing pigeon Columba livia. We explored their structure, abundance, and composition. Firstly, we showed that sampling technique affected the outcome of the results. While broadly used, the egg swabbing procedure led to a lower DNA extraction efficiency and provided different profiles of bacterial communities than those based on crushed eggshell pieces. Secondly, we observed shifts in bacterial and fungal communities during incubation. At late incubation, bacterial communities showed a reduction in diversity, while their abundance increased, possibly due to the competitive advantage of some species. When compared to their bacterial counterparts, fungal communities also decreased in diversity at late incubation. In that case, however, the decline was associated with a diminution of their overall abundance. Conclusively, our results showed that although incubation might inhibit microbial growth when compared to unincubated eggs, we observed the selective growth of specific bacterial species during incubation. Moreover, we showed that fungi are a substantial component of the microbial communities associated with eggshells and require further investigations in avian ecology. Identifying the functional roles of these microorganisms is likely to provide news insights into the evolutionary strategies that control embryo survival.     

泥鳅雄核发育纯合二倍体的产生

以机械方法挑去泥鳅(Misgurnus anguillicaudatus)×大鳞副泥鳅(Paramisgurnus dabryanus)(♀)属间杂交受精卵的雌核,得到泥鳅雄核发育单倍体胚胎。将这种单倍体胚胎的囊胚细胞核移植到大鳞副泥鳅去核卵中,获得了243个原肠胚胎,其染色体鉴定表明,29.6%的核移植体的染色体发生了加倍。在另一实验组中,从769个核移植卵得到了5尾2cm以上的个体。尾鳍染色体鉴定、肌肉LDH同工酶电泳和形态鉴别表明,这5尾核移植体为泥鳅雄核发育纯合二倍体。     

Artificial spawning and rearing of lake sturgeon,Acipenser fulvescens,in Wild Rose State Fish Hatchery,Wisconsin, 1982–1983

Synopsis Attempts to culture lake sturgeon, Acipenser fulvescens, in the past have generally met with limited success. The Wisconsin Department of Natural Resources has been experimenting with artificial propagation of this species since 1979. The intent has been to develop egg collection and handling techniques, hatching regimes, larva and juvenile diet formulations, and to evaluate juvenile survival after stocking. Eggs were collected by caesarian section and fertilized with milt from ripe males taken during annual sturgeon spawning runs on the Fox and Wolf rivers in central Wisconsin. After insemination, the eggs were treated in a saturated solution of Bentonite clay and transported to the hatchery. Eggs were incubated at temperatures ranging from 13–16° C and embryos began hatching within 4 to 8 days. Hatching success ranged from 42 to 96%. Yolksac absorption was complete within 10 days of hatching. Larvae then became positively phototactic and swam actively as if searching for food. Successful larval diets consisted of live brine shrimp nauplii followed by larger zooplankton, primarily Daphnia sp. Juveniles grew best on diets of live Tubifex sp. and chopped earthworms. Liver, fish mash (ground up trout) and pelleted dry food were poorly accepted. Hatchery reared sturgeon grew more slowly than did wild fish.     

Gut microbiota of invasive bullfrog tadpoles responds more rapidly to temperature than a noninvasive congener

Environmental temperature can alter the composition, diversity, and function of ectothermic vertebrate gut microbial communities, which may result in negative consequences for host physiology, or conversely, increase phenotypic plasticity and persistence in harsh conditions. The magnitude of either of these effects will depend on the length of time animals are exposed to extreme temperatures, and how quickly the composition and function of the gut microbiota can respond to temperature change. However, the temporal effects of temperature on gut microbiota are currently unknown. Here, we investigated the length of time required for increased temperature to alter the composition of gut bacterial communities in tadpoles of two frog species, the green frog, Lithobates clamitans, and its congener, the globally invasive American bullfrog, L. catesbeianus. We also explored the potential functional consequences of these changes by comparing predicted metagenomic profiles across temperature treatments at the last experimental time point. Bullfrog‐associated microbial communities were more plastic than those of the green frog. Specifically, bullfrog communities were altered by increased temperature within hours, while green frog communities took multiple days to exhibit significant changes. Further, over ten times more bullfrog bacterial functional pathways were temperature‐dependent compared to the green frog. These results support our hypothesis that bullfrog gut microbial communities would respond more rapidly to temperature change, potentially bolstering their ability to exploit novel environments. More broadly, we have revealed that even short‐term increases in environmental temperature, expected to occur frequently under global climate change, can alter the gut microbiota of ectothermic vertebrates.     

Eggshell characteristics and yolk composition in the common cuckoo Cuculus canorus: are they adapted to brood parasitism?

The developmental rate of cuckoo embryos and their hatching size is greater than that of host species, which may require more nutrient resources in the egg and more intensive gas exchange during development. In the present study, we compared various egg characteristics of a brood parasite, the common cuckoo Cuculus canorus, and its frequent host, the great reed warbler Acrocephalus arundinaceus. As maternally‐derived testosterone is known to enhance growth rate of embryos and hatchlings, cuckoo eggs are expected to contain higher concentration of testosterone than host eggs. In addition, we expected higher concentration of antioxidants in cuckoo eggs to protect embryos from oxidative stress associated with accelerated growth. Our results showed that cuckoo eggs had thicker shells and higher pore density than great reed warbler eggs. Yolk was significantly heavier in cuckoo eggs and contained higher concentrations of carotenoids and vitamin E, however, yolk androgen and immunoglobulin concentrations were lower in cuckoo eggs as compared to great reed warbler eggs. We also examined whether eggshell colour was associated to egg quality, and detected a positive association between blue‐green chroma and yolk antioxidant concentration in both species, suggesting that eggshell colour reflects the antioxidant investment of the female into the eggs. Our results suggest that cuckoo females increase the size, growth rate and competitive ability of their young by providing them with more nutrients and more dietary antioxidants for embryonic development, and not through elevated yolk testosterone or antibody levels. In addition, increased porosity of cuckoo eggshells may allow embryos to develop more rapidly because of a greater capacity of gas exchange.     

Development, surface exposure, and embryo behavior affect oxygen levels in eggs of the red-eyed treefrog, Agalychnis callidryas

Oxygen stress can slow development, induce hatching, and kill eggs. Terrestrial anamniote embryos face a potential conflict between oxygen uptake and water loss. We measured oxygen levels within eggs to characterize the respiratory environment for embryos of the red-eyed treefrog, Agalychnis callidryas, a Neotropical frog with arboreal egg masses and plastic hatching timing. Perivitelline oxygen partial pressure (Po2) was extremely variable both within and among eggs. Po2 increased with air-exposed surface of the egg and declined over the developmental period before hatching competence. Through the plastic hatching period, however, average Po2 was stable despite continued rapid development. Development was synchronous across a wide range of perivitelline Po2 (0.5-16.5 kPa), and hatching-competent embryos tolerated Po2 as low as 0.5 kPa without hatching. The variation in Po2 measured over short periods of time within individual eggs was as great as that measured across development or surface exposure, including sharp transients associated with embryo movements. There was also a strong gradient of Po2 across the egg from superficial to deep positions. Ciliary circulation of fluid within the egg is clearly insufficient to keep it mixed. Embryos may maintain development under hypoxic conditions by strategic positioning of respiratory surfaces, particularly external gills, to exploit the patchy distribution of oxygen within their eggs.     

A genetic component of resistance to fungal infection in frog embryos

The embryo has traditionally been considered to completely rely upon parental strategies to prevent threats to survival posed by predators and pathogens, such as fungi. However, recent evidence suggests that embryos may have hitherto neglected abilities to counter pathogens. Using artificial fertilization, we show that among-family variation in the number of Saprolegnia-infected eggs and embryos in the moor frog, Rana arvalis, cannot be explained by maternal effects. However, analysed as a within-females effect, sire identity had an effect on the degree of infection. Furthermore, relatively more eggs and embryos were infected when eggs were fertilized by sperm from the same, compared with a different, population. These effects were independent of variation in fertilization success. Thus, there is likely to be a significant genetic component in embryonic resistance to fungal infection in frog embryos. Early developmental stages may show more diverse defences against pathogens than has previously been acknowledged.     

Genetic inactivation of Leuciscus idus L. (ide) oocytes using UV irradiation

Oocytes of Leuciscus idus were genetically inactivated using ultraviolet (UV) irradiation. Eggs for the experiment were obtained from dark-coloured females, whereas milt was taken from yellow-coloured (recessive marker) males. The survival at the eleutheroembryo stage (free embryo) in all experimental groups fertilized with genetically inactivated spermatozoa was much lower than in control groups. All haploid embryos showed morphological abnormalities, such as a stunted body and a poorly formed retina, and the condition was referred to as the haploid syndrome. The androgenetic origin (haploid or diploid embryos) was checked using a recessive colour marker ('blond'). The optimal doses of UV irradiation were 3,456-4,608 Jm(-2) at which almost 100% haploid embryos were produced at a hatching rate of >15%. Lower UV-ray doses influenced abnormal embryo development. Ploidy level recognition showed a typical value of mean active nucleoli per cell in haploid and diploid (control fish and spontaneous androgenotes) specimens. Abnormal dark embryos were classified as aneuploids.     

池沼公鱼移殖放流试验研究

作者于1984—1986年进行了池沼公鱼移殖放流试验研究,移入水库的池沼公鱼已能自然产卵繁殖,形成了经济群体。本文论及了移殖放流的理论依据、移殖放流技术、移殖放流效果、移殖池沼公鱼的生态效益的分析和池沼公鱼的资源管理。     

Precopulatory mate guarding and mating behaviour in the rotifer Epiphanes senta (Monogononta: Rotifera)

Epiphanes senta is a littoral rotifer species that occurs in temporary waters and displays a mating behaviour which has not, to my knowledge, so far been described for monogonont rotifers. Monogonont rotifers show distinctive periods within their life cycle during which mictic females appear. Mictic females produce haploid eggs that develop into males or into diapausing eggs if fertilized. The females of E. senta are mostly stationary on the substrate while males are more active swimmers. If they encounter eggs with female embryos of their own species, they attend them and mate with the hatching female. Experiments showed that males are able to discriminate between male, female and diapausing eggs. They exhibit a strong preference for female eggs that are only a few hours away from hatching compared with eggs in early developmental stages. Further experiments did not show any significant differences in male attendance of mictic and amictic eggs. It is hypothesized that males judge the age of a female egg by sensing a chemical that is produced by the growing embryo and diffuses through the egg shell. The male mating behaviour is similar to precopulatory mate guarding known from arthropods but it lacks the monopolization of the female by the male.     

Developmental biology of medaka fish (Oryzias latipes) exposed to alkalinity stress

Alkalinity stress is common in cultured aquatic animals and considered to be one of the major stress factors for fishes when they are transferred to saline‐alkali waters. To evaluate potential effects of alkalinity on the developmental biology of Oryzias latipes, fertilized eggs, larvae and breeding fish were exposed to different carbonate alkalinity concentrations of 1.5–64.5 meq l^?1, for 9, 120, and 60 days, respectively. The mortality of embryos significantly increased when exposed to the high concentrations (16.5–64.5 meq l^?1). Although more than 50% of survived embryos hatched in 16.5 and 31.4 meq l^?1 concentrations of carbonate alkalinity, most were not able to swim up after hatching. Morphological abnormalities such as coagulated embryos, halted embryo development, and hatching failure were observed at stages 15, 29–33 and 38 in high concentrations (31.4, 64.5 meq l^?1). Almost all larvae in 16.5 and 31.4 meq l^?1 treatments died 70 d post‐hatch. Growth of juveniles exposed to carbonate alkalinity of 5.3 and 8.8 meq l^?1 was not significantly different at 70 d and 120 d post‐hatch. The number of eggs released by breeders, the fertilization rate and the hatching rate of eggs were significantly lower in the 31.4 meq l^?1 treatment than in other treatments. Although medaka are capable of surviving in high alkalinities (31.4, 64.5 meq l^?1) for an extended period of time, these conditions are stressful to the fish, especially at the embryonic and reproductive stages.     

Fur seal microbiota are shaped by the social and physical environment,show mother–offspring similarities and are associated with host genetic quality

Despite an increasing appreciation of the importance of host–microbe interactions in ecological and evolutionary processes, the factors shaping microbial communities in wild populations remain poorly understood. We therefore exploited a natural experiment provided by two adjacent Antarctic fur seal (Arctocephalus gazella) colonies of high and low social density and combined 16S rRNA metabarcoding with microsatellite profiling of mother–offspring pairs to investigate environmental and genetic influences on skin microbial communities. Seal‐associated bacterial communities differed profoundly between the two colonies, despite the host populations themselves being genetically undifferentiated. Consistent with the hypothesis that social stress depresses bacterial diversity, we found that microbial alpha diversity was significantly lower in the high‐density colony. Seals from one of the colonies that contained a stream also carried a subset of freshwater‐associated bacteria, indicative of an influence of the physical environment. Furthermore, mothers and their offspring shared similar microbial communities, in support of the notion that microbes may facilitate mother–offspring recognition. Finally, a significant negative association was found between bacterial diversity and heterozygosity, a measure of host genetic quality. Our study thus reveals a complex interplay between environmental and host genetic effects, while also providing empirical support for the leash model of host control, which posits that bacterial communities are driven not only by bottom‐up species interactions, but also by top‐down host regulation. Taken together, our findings have broad implications for understanding host–microbe interactions as well as prokaryotic diversity in general.     

Major Histocompatibility Complex class IIb polymorphism influences gut microbiota composition and diversity

Animals harbour diverse communities of symbiotic bacteria, which differ dramatically among host individuals. This heterogeneity poses an immunological challenge: distinguishing between mutualistic and pathogenic members of diverse and host‐specific microbial communities. We propose that Major Histocompatibility class II (MHC) genotypes contribute to recognition and regulation of gut microbes, and thus, MHC polymorphism contributes to microbial variation among hosts. Here, we show that MHC IIb polymorphism is associated with among‐individual variation in gut microbiota within a single wild vertebrate population of a small fish, the threespine stickleback. We sampled stickleback from Cedar Lake, on Vancouver Island, and used next‐generation sequencing to genotype the sticklebacks’ gut microbiota (16S sequencing) and their MHC class IIb exon 2 sequences. The presence of certain MHC motifs was associated with altered relative abundance (increase or decrease) of some microbial Families. The effect sizes are modest and entail a minority of microbial taxa, but these results represent the first indication that MHC genotype may affect gut microbiota composition in natural populations (MHC‐microbe associations have also been found in a few studies of lab mice). Surprisingly, these MHC effects were frequently sex‐dependent. Finally, hosts with more diverse MHC motifs had less diverse gut microbiota. One implication is that MHC might influence the efficacy of therapeutic strategies to treat dysbiosis‐associated disease, including the outcome of microbial transplants between healthy and diseased patients. We also speculate that macroparasite‐driven selection on MHC has the potential to indirectly alter the host gut microbiota, and vice versa.