Explore the vast range of titles available.

• Vitellogenin (Vg) is a well-known nutritious protein involved in reproduction in nearly all oviparous animals, including insects. Recently, Vg has been detected in saliva proteomes of several piercing–sucking herbivorous arthropods, including the small brown planthopper (Laodelphax striatellus, SBPH). Its function, however, remains unexplored. • We investigated the molecular mechanism underlying SBPH orally secreted Vg-mediated manipulation of plant–insect interaction by RNA interference, phytohormone and H₂O₂ profiling, protein–protein interaction studies and herbivore bioassays. • A C-terminal polypeptide of Vg (VgC) in SBPH, when secreted into rice plants, acted as a novel effector to attenuate host rice defenses, which in turn improved insect feeding performance. Silencing Vg reduced insect feeding and survival on rice. Vg-silenced SBPH nymphs consistently elicited higher H₂O₂ production, a well-established defense mechanism in rice, whereas expression of VgC in planta significantly hindered hydrogen peroxide (H₂O₂) accumulation and promoted insect performance. VgC interacted directly with the rice transcription factor OsWRKY71, a protein which is involved in induction of H₂O₂ accumulation and plant resistance to SBPH. • These findings indicate a novel effector function of Vg: when secreted into host rice plants, this protein effectively weakened H₂O₂-mediated plant defense through its association with a plant immunity regulator.

Heat tolerance at the immobile embryonic stage is expected to be critical in determining species vulnerability to climate change. However, how the mean and developmental plasticity of embryonic heat tolerance vary geographically, and how these geographic variations affect species' vulnerability under climate change remain unknown. We experimentally determined the mean and developmental plasticity of embryonic acute heat tolerance (EAHT, i.e., heat shock temperature at which embryonic heartbeats ceased) for three latitudinally distributed populations of an oviparous lacertid lizard. The experimental results suggested that the mean EAHT decreased with decreasing latitude and that the reaction norms of EAHT in relation to developmental temperatures showed \"flat,\" \"bell-shaped,\" and \"decreasing\" patterns at high, medium, and low latitudes, respectively. Based on the means and plasticity of EAHT and weather data across China, we project that the heat stress frequency would increase from the present to the future and increase toward low latitudes. Furthermore, heat stress becomes more extensive with the incorporation of developmental plasticity. Incorporating the mean EAHT during the embryonic development season, heat stress frequency, and climate variables in a species distribution model projects that suitable habitats could move northward in response to ongoing climate change and shrink due to the loss of southern habitat. More-over, even lizards within the areas that are predicted to remain highly suitable are expected to experience increases in heat stress over time, particularly at medium and low latitudes. Our study reveals geographic variation in the mean and developmental plasticity of EAHT and highlights its importance for predicting species vulnerability and range shifts in response to climate change.

Hypersaline Great Salt Lake’s (GSL: Utah, USA) pelagic food web is dominated by the herbivore, Artemia franciscana . Artemia demographic responses (survival, developmental transition, and reproduction) to GSL salinities, temperatures, common phytoplankton and yeast, and food levels were examined by factorial experiment. Survival across developmental stages was best at 90 ppt salinity, and decreased as temperature increased. Transition between life stages was best at 45 ppt salinity, and increased as temperature increased. Food was most important with both survival and transitioning responding similarly to food types and increasing with amount of food. Artemia reproduce in two ways (diapausing cysts – oviparity, live young – ovoviviparity): ovoviviparous and total reproduction were greatest at 90 ppt salinity and 20 °C, while oviparous reproduction was weakly affected by salinity and greatest at 20 °C. Oviparity was greatest at low food availability, while ovoviviparity and total reproduction increased with food availability, so reproduction shifted from oviparity to ovoviviparity as food increased. Maternal effects were observed for cyst hatchability, and ovoviviparous nauplii survival and transitioning to the juvenile stage. Combinations of salinity, temperature, food taxa and food amount strongly affect demography, making single factor studies of limited value. Results explain Artemia abundance in different parts of GSL and among years.

Viviparity (live‐bearing) has independently evolved from oviparity (egg‐laying) in more than 100 lineages of squamates (lizards and snakes). We might expect consequent shifts in selective forces to affect per‐brood reproductive investment (RI = total mass of offspring relative to maternal mass) and in the way in which that output is partitioned (number vs. size of offspring per brood). Based on the assumption that newly born offspring are heavier than eggs, we predicted that live‐bearing must entail either increased RI or a reduction in offspring size and/or fecundity. However, our phylogenetically controlled analysis of data on 1,259 squamate species revealed no significant differences in mean offspring size, clutch size or RI between oviparous and viviparous squamates. We attribute this paradoxical result to (1) strong selection on offspring sizes, unaffected by parity mode, (2) the lack of a larval stage in amniotes, favouring large eggs even in the ancestral oviparous mode and (3) the ability of viviparous females to decrease the mass of uterine embryos by reducing extra‐embryonic water stores. Our analysis shows that squamate eggs (when laid) weigh about the same as the hatchlings that emerge from them (despite a many‐fold increase in embryo mass during incubation). Most of the egg mass is due to components (such as water stores and the eggshell) not required for oviductal incubation. That repackaging enables live‐born offspring to be accommodated within the mother's body without increasing total litter mass. The consequent stasis in reproductive burden during the evolutionary transition from oviparity to viviparity may have facilitated frequent shifts in parity modes. Viviparity evolved multiple times in squamates yet the effect of its evolution of viviparity on crucial aspects of the lives of offspring and their mothers are unclear. Analysing >1,250 species the authors find very little differences between oviparous and viviparous squamates in clutch size, offspring size or reproductive investment. The evolution of yolk‐laden eggs may have made the transition to viviparity less costly, while making egg‐laying equally viable.

The pea aphid, Acyrthosiphon pisum, is a paradigmatic photoperiodic species that exhibits a remarkable annual life cycle, which is tightly coupled to the seasonal changes in day length. During spring and summer, characterised by longer days, aphid populations consist exclusively of viviparous females that reproduce parthenogenetically. When autumn comes and the days shorten, aphids switch their reproductive mode and generate males and oviparous sexual females, which mate and produce cold-resistant eggs that overwinter and survive the unfavourable season. While the photoperiodic responses have been well described, the nature of the timing mechanisms which underlie day length discrimination are still not completely understood. Experiments from the 1960’s suggested that aphids rely on an ‘hourglass’ clock measuring the elapsed time during the dark night by accumulating a biochemical factor, which reaches a critical threshold at a certain night length and triggers the switch in reproduction mode. However, the photoperiodic responses of aphids can also be attributed to a strongly dampened circadian clock. Recent studies have uncovered the molecular components and the location of the circadian clock in the brain of the pea aphid and revealed that it is well connected to the neurohormonal system controlling aphid reproduction. We provide an overview of the putative mechanisms of photoperiodic control in aphids, from the photoreceptors involved in this process to the circadian clock and the neuroendocrine system.

Climate change plays a key role in the development and survival of oviparous ectotherms such as sea turtles. Higher environmental temperatures are expected to lead to increased production of female hatchlings and potential feminization of many populations, as well as reduced hatching success and hatchling fitness. We investigated how different sand temperatures affect sea turtle embryo mortality, hatchling phenotype, and hatchling predation during their crawl to the sea. The study was conducted in Cabo Verde, the only rookery of the endangered loggerhead turtle (Caretta caretta) in the Eastern Atlantic. During three consecutive seasons (2015–2017), 240 loggerhead clutches were exposed to three different incubation temperature regimes created by different sand colours. The warm treatment (mean = 32.3 °C ± 0.5) killed 33% more embryos than the cold treatment (mean = 29.7 °C ± 0.6). Hatchlings from the warm treatment were mostly females, smaller in size, and had lower performance. Hatchling predation by ghost crabs during seaward transit was higher for hatchlings incubated in the warm treatment. Combining embryo mortality and hatchling predation, the rate of female hatchling arrival at the sea was more than twice as high in the cold treatment (34.4 females per 100 eggs) than in the warm treatment (16.0 females per 100 eggs). This increase in mortality caused by warmer incubation temperatures may cancel any potential benefit of a female-biased sex ratio. Conservation planners should consider behavioural adaptations and the potential dispersal of the nesting areas to colder areas to increase resilience of loggerhead turtles to climate change.

Disease management is crucial for the global growth of aquaculture. Parasitic monogeneans present a high risk for finfish aquaculture industries and have been associated with reduced growth, morbidity and mortality. Monogeneans are extremely fecund and exhibit short generation times which can result in exponential population growth. Information on the reproductive biology of specific monogenean species can enable strategically timed treatments to break parasite life cycles. However, the diversity of reproductive strategies (oviparity, viviparity and self-fertilisation) presents considerable barriers in disease management. In addition, environmental conditions such as seasons, water temperature and salinity also influence parasite life cycles, including generation time, fecundity, egg embryonated period and age at sexual maturity. This review examines the diversity of reproductive strategies exhibited by monogenean parasites and the influence of environmental parameters on parasite life cycles. Various parasite management strategies including mechanical, biological and chemical treatments are evaluated.

Extreme climate events, including rapid-onset flash droughts, are increasing with anthropogenic climate change. Flash droughts impact growth and survival of plants, microbes, and invertebrates, yet less is known about their ecological consequences in vertebrates. Although constant water deprivation during vertebrate embryonic development influences a range of offspring traits, the effects of acute, short-term hydric stress are less well-studied, particularly in the context of subsequent survival in the field. In this study, we combined experimental manipulation in the laboratory with a large-scale field experiment to examine the effects of the developmental timing of flash drought in an oviparous vertebrate model. We exposed common snapping turtle ( Chelydra serpentina ) eggs to simulated flash drought events at different stages of embryonic development and measured the effects on growth and offspring phenotypes. We then conducted an experimental release in the field to evaluate offspring survival during migration from the nest. Flash drought during mid-to-late development decreased egg mass, incubation time, and hatchling body size, while flash drought during late development substantially limited post-hatching survival in the field. This study is among the first to examine juvenile survival effects of flash drought during embryonic development in a vertebrate system. Our results suggest that early-life mortality is likely to increase as flash droughts intensify with climate change. This study contributes to a growing body of research on the ecological consequences of extreme climate events and highlights the importance of considering these events in a developmental context.

Animals breed at times of the year that ensure offspring production and growth during favorable periods. DNA methylation is one mechanism by which expression of genes necessary for reproduction may be regulated, enabling expression only at appropriate times. Much work on seasonal breeding in vertebrates has focused on the neuroendocrine system, however oviparous vertebrates, including birds, also rely on the liver for production of yolk precursors, such as vitellogenin (VTG) that will provide the nutrients necessary for development in ovo. We hypothesized that changes in DNA methylation in the promoter for VTG2 in the liver may be one mechanism ensuring appropriately timed seasonal breeding. DNA methyltransferases (DNMTs) facilitate de novo (DNMT3a) and maintenance (DNMT1) of DNA methylation. We observed that liver expression of VTG2 was lower in birds sampled during the pre‐breeding compared with the early‐breeding period, and also observed changes in liver expression of DNMT1 and DNMT3a between these two periods. Contrary to our predictions, we observed an increase in methylation from pre‐ to early‐breeding at one of three CpG sites in the promoter of the VTG2 gene, with no differences at the other two CpG sites. Finally, we asked if patterns of DNA methylation of VTG2 in liver were similar in the blood. Although we observed strong correlations between blood and liver in two sites that did not change between pre‐ and early‐breeding, there was only a trend for a significant association between blood and liver DNA methylation at the site that displayed an increase in liver DNA methylation between sampling periods. Together, these findings suggest that changes in DNA methylation in an important tissue outside of the reproductive endocrine axis (liver) may play a critical role in appropriate timing of seasonal clutch initiation, though it is unclear if these epigenetic changes are all reflected in blood.

Viviparity has evolved from oviparity approximately 142 times among vertebrates. Different theories have been proposed to explain the evolution of each of its traits in the different taxa. None, however, is applicable to all the viviparous vertebrates, since the derived ecological advantages such as controlling incubating temperature or protecting eggs against predation differ amongst clades. Most theories have been developed under a co-adaptive perspective, whereas less attention has been paid to conflict. We developed a broad panorama of the gradual evolution, from oviparity to advanced forms of viviparity, that includes the different environmental and co-adaptive selective pressures that have been suggested to be at the root of the different instances of viviparity and of the diverse maternal–foetal adaptations for nutrient transfer seen amongst vertebrates. Furthermore, we highlight the importance of conflict as a crucial driver of the evolution of many of those traits, including the evolution of epigenetic control of maternal resources. We suggest that the different types of matrotrophic viviparity, and probably also some reversals to oviparity, have been the result of an antagonistic coevolution between mothers, fathers and offspring, and their genomes. We additionally suggest that the appearance of a trait that allowed or favoured the evolution of internal development and matrotrophy generates a new selective environment that promotes further adaptations or counteradaptations, leading to the observed diversity of forms of embryonic development, nourishment, and transfer of maternal nutrients, and ultimately to the diversity of extant viviparous taxa.