Evolution of sex-biased maternal effects in birds. IV. Intra-ovarian growth dynamics can link sex determination and sex-specific acquisition of resources

The evolutionary importance of maternal effects is determined by the interplay of maternal adaptations and strategies, offspring susceptibility to these strategies, and the similarity of selection pressures between the two generations. Interaction among these components, especially in species where males and females differ in the costs and requirements of growth, limits inference about the evolution of maternal strategies from their expression in the offspring phenotype alone. As an alternative approach, we examine divergence in the proximate mechanisms underlying maternal effects across three house finch populations with contrasting patterns of sex allocation: an ancestral population that shows no sex-biased ovulation, and two recently established populations at the northern and southern boundaries of the species range that have opposite sequences of ovulation of male and female eggs. For each population, we examined how oocyte acquisition of hormones, carotenoids and vitamins was affected by oocyte growth and overlap with the same and opposite sexes. Our results suggest that sex-specific acquisition of maternal resources and sex determination of oocytes are linked in this system. We report that acquisition of testosterone by oocytes that become males was not related to growth duration, but instead covaried with temporal exposure to steroids and overlap with other male oocytes. In female oocytes, testosterone acquisition increased with the duration of growth and overlap with male oocytes, but decreased with overlap with female oocytes. By contrast, acquisition of carotenoids and vitamins was mostly determined by organism-wide partitioning among oocytes and oocyte-specific patterns of testosterone accumulation, and these effects did not differ between the sexes. These results provide important insights into three unresolved phenomena in the evolution of maternal effects - (i) the evolution of sex-specific maternal allocation in species with simultaneously developing neonates of both sexes; (ii) the link between sex determination and sex-specific acquisition of maternal products; and (iii) the evolution of context-dependent modulation of maternal effects.     

Parent–egg–progeny Relationships in Teleost Fishes: An Energetics Perspective

Age-related variations in chemical composition of egg matter were found in females in some studies, but they do not seem to be a universal phenomenon. In contrast, egg size can be well predicted from female age. The relationship has a parabolic shape, but the predicted size decrease of eggs from old females has not always been documented. Female size is an important contributor to egg size, both at intra- and inter-specific levels. Dependence of fecundity on body size has usually been described by a power function. A trade-off between egg number and size is considered in light of life history strategies. During a spawning season egg size may differ between successive batches, but lack of effects of egg batch sequence was reported in some studies. In yolk-feeding fish three discrete periods of elevated mortality are typically observed: shortly after egg activation, during hatching, and at final yolk resorption. The positive relationships between female size, egg size and offspring size/resistance to starvation and predation are a key pathway in parent–egg–progeny relationships. Both maternal and paternal effects contribute to the total survival of offspring, but they operate in different ways and at different times. In contrast to the importance of female size, no paternal size effects were revealed, but density and motility of spermatozoans were decisive. Typically, paternal effects diminish earlier in ontogeny. Major factors governing embryonic survival (fertilisation success and hatching success) differ from factors to which starvation mortality of yolk-feeding larvae is related. Embryonic survival is affected by female age via egg matter composition, by egg ripeness and paternal factors such as sperm density and motility. In contrast, starvation mortality of yolk-feeding larvae depends largely on female attributes (age, size and fecundity) via egg size, and, in some batch spawners, on egg batch sequence. Among teleost species egg size varies across a wide range (from 0.3 to 85–90 mm in diameter). Species that spawn large eggs are relatively rare. Caloric value of egg dry matter varies within a narrow range of 20–30 J mg⁻¹. Ecosystem and evolutionary components, and reproductive style are factors that contribute to egg endowment and yolk quality. During the last decade considerable progress was made in the methodology and understanding of paternal effect on progeny performance in fishes. This paper reviews these of parent–egg–progeny relationships.     

The effect of mycorrhizal infection of Abutilon theophrasti on competitiveness of offspring

1. Our goal was to determine whether mycorrhizal infection of one generation of plants could influence the competitiveness of the subsequent generation.
2. We grew the offspring of mycorrhizal (M) and non-mycorrhizal (NM) Abutilon theophrasti plants together in dense populations in large boxes in a greenhouse.
3. Offspring of M plants were larger than offspring of NM plants. As the experiment progressed, the difference in size was magnified and self-thinning occurred.
4. Compared with offspring of NM plants, offspring of M plants had a twofold greater survival and collectively produced a total of nearly four times as many seeds.
5. We conclude that mycorrhizal infection of the parent generation can increase the competitive ability of the offspring.     

不同家禽蛋类营养成分的比较

蛋类是人们生活中的重要食品 ,本实验通过比较土洋鸡蛋及鸭蛋中的几种主要营养物质蛋白质、胆固醇、卵磷脂的含量 ,得到如下结果 :鸡蛋中蛋白质在种类及含量上都多于鸭蛋 ,而土鸡蛋中的蛋白质含量又多于洋鸡蛋 ;卵磷脂含量最高的为鸭蛋 ,然后依次为土鸡蛋和洋鸡蛋 ;土鸡蛋中含有最高量的胆固醇 ,洋鸡蛋次之 ,最低的为鸭蛋     

Evolution of sex-biased maternal effects in birds: III. Adjustment of ovulation order can enable sex-specific allocation of hormones, carotenoids, and vitamins

Overlap in growth of offspring should constrain the opportunity for sex-biased maternal effects, yet sex-specific allocation of maternal resources among simultaneously growing ova is often observed in vertebrates. In birds, such allocation can be accomplished either by temporal clustering of ova that become the same sex, resulting in sex-biased egg-laying order, or by follicle-specific delivery of maternal resources. Two house finch populations at the northern and southern boundaries of the species range have opposite ovulation sequences of male and female eggs, and thus, in the absence of sex differences in ova growth or sex-specific maternal strategies, would be expected to have opposite sex-specific accumulation of maternal products. We found that the populations had strong and similar gradients of steroid distribution in relation to ovulation order, whereas distribution of carotenoids and vitamins correlated with each follicle's accumulation of steroids. In both populations, temporal bias in production of sons and daughters within a clutch enabled strongly sex-specific acquisition of maternal products, and oocytes of the same sex were highly interdependent in their accumulation of steroids. Moreover, in nests where the sex-bias in relation to ovulation order deviated from population-specific patterns, eggs had highly distinct concentrations of steroids, carotenoids and vitamins. These results and previous findings of sex-specific yolk partitioning among oocytes suggest that oocytes that become males and females are temporally or spatially clustered during their ovarian growth. We discuss the implication of these findings for the evolution of sex-specific maternal resource allocation.     

Maternal allocation strategies and differential effects of yolk carotenoids on the phenotype and viability of yellow-legged gull (Larus michahellis) chicks in relation to sex and laying order

Egg quality may mediate maternal allocation strategies according to progeny sex. In vertebrates, carotenoids have important physiological roles during embryonic and post-natal life, but the consequences of variation in yolk carotenoids for offspring phenotype in oviparous species are largely unknown. In yellow-legged gulls, yolk carotenoids did not vary with embryo sex in combination with egg laying date, order and mass. Yolk lutein supplementation enhanced the growth of sons from first eggs but depressed that of sons from last eggs, enhanced survival of daughters late in the season, and promoted immunity of male chicks and chicks from small eggs. Lack of variation in egg carotenoids in relation to sex and egg features, and the contrasting effects of lutein on sons and daughters, do not support the hypothesis of optimal sex-related egg carotenoid allocation. Carotenoids transferred to the eggs may rather result from a trade-off between opposing effects on sons or daughters.     

Transgenerational acclimatization in an herbivore–host plant relationship

Twenty years ago, scientists began to recognize that parental effects are one of the most important influences on progeny phenotype. Consequently, it was postulated that herbivorous insects could produce progeny that are acclimatized to the host plant experienced by the parents to improve progeny fitness, because host plants vary greatly in quality and quantity, and can thus provide important cues about the resources encountered by the next generation. However, despite the possible profound implications for our understanding of host-use evolution of herbivores, host-race formation and sympatric speciation, intense research has been unable to verify transgenerational acclimatization in herbivore–host plant relationships. We reared Coenonympha pamphilus larvae in the parental generation (P) on high- and low-quality host plants, and reared the offspring (F₁) of both treatments again on high- and low-quality plants. We tested not only for maternal effects, as most previous studies, but also for paternal effects. Our results show that parents experiencing predictive cues on their host plant can indeed adjust progeny''s phenotype to anticipated host plant quality. Maternal effects affected female and male offspring, whereas paternal effects affected only male progeny. We here verify, for the first time to our knowledge, the long postulated transgenerational acclimatization in an herbivore–host plant interaction.     

Ultrasound imaging of reproductive organs and eggs in Galapagos tortoises,Geochelone elephantopus spp

This study demonstrates the efficacy of using ultrasound to determine the presence of ovarian developing, preovulatory, and atretic follicular structures and oviductal eggs in the Galapagos tortoise, Geochelone elephantopus spp. Ultrasound was effective in locating both right and left ovarian structures in 92% (n = 100 ovaries) of the trials. Developing and preovulatory follicles and oviductal eggs were echogenically visualized and had measurements ranging from 18 to 44 mm (n = 93) and 55 to 68 mm (n = 9), respectively. Atretic follicles ranged in size from 10 to 38 mm (n = 10). In one trial with four G. elephantopus, ultrasound observations were validated with the use of laparoscopy. All procedures were accomplished without general anesthesia on a specifically designed restraining table. Ultrasound provides an effective, safe modality for determining the reproductive status of adult female tortoises.     

Age at maturity in wild baboons: genetic, environmental and demographic influences

The timing of early life-history events, such as sexual maturation and first reproduction, can greatly influence variation in individual fitness. In this study, we analysed possible sources of variation underlying different measures of age at social and physical maturation in wild baboons in the Amboseli basin, Kenya. The Amboseli baboons are a natural population primarily comprised of yellow baboons (Papio cynocephalus) that occasionally hybridize with anubis baboons (Papio anubis) from outside the basin. We found that males and females differed in the extent to which various factors influenced their maturation. Surprisingly, we found that male maturation was most strongly related to the proportion of anubis ancestry revealed by their microsatellite genotypes: hybrid males matured earlier than yellow males. In contrast, although hybrid females reached menarche slightly earlier than yellow females, maternal rank and the presence of maternal relatives had the largest effects on female maturation, followed by more modest effects of group size and rainfall. Our results indicate that a complex combination of demographic, genetic, environmental, and maternal effects contribute to variation in the timing of these life-history milestones.     

Diapause in Monogonont Rotifers

This review focuses on more recent findings on the diapause in Monogonont rotifers, since the major reviews by Pourriot & Snell (1983, Hydrobiologia 104: 213–224) and Gilbert (1992, Rotifera. In Adiyodi, K. G. & R. G. Adiyodi (eds), Reproductive Biology of Invertebrates, Vol. 5 – Sexual Differentiation and Behaviour. IBH Publishing Co., Oxford: 115–136; Vol. 6A – Asexual Propagation and Reproductive Strategies. IBH Publishing Co., Oxford: 231–263.). It covers diapausing egg formation, diapausing egg survival, and diapausing egg hatching as well as possible strategies involved in these processes. Data from laboratory and field studies exist, but little information is available on diapausing egg hatching in the field. Resting or diapausing egg production can be mictic and in some cases amictic. Mictic diapausing egg production depends on the balance between cues promoting and inhibiting mictic female production. Such cues can be either environmental or endogenous. Our knowledge on factors inducing mixis is still limited to a few species, but effects of crowding on mixis induction may be more widespread. Recent results also show that male mating behavior may play an important role in the successful production of diapausing eggs. Hatching may be induced by factors related to temperature and light conditions; also desiccation may have a role. However, desiccation of temporary habitats may also be damaging to diapausing stages. Although few data are available, those existing point to distinct differences between populations and the importance of clonal variation within populations regarding the initiation as well as the termination of diapause.