•We estimate skipped spawning for Northeast Arctic (NEA) haddock.•A time-series of population level fraction of skipping was estimated.•Large interannual variation in skipped spawning at the stock ...level was observed.•The frequency of skipped spawning was negatively associated energy reserves.
Although the phenomenon of skipped spawning has been described in numerous fishes, time-series are scarce. We used the presence of post-ovulatory follicles in histological gonad slides from females not developing oocytes for Northeast Arctic (NEA) haddock Melanogrammus aeglefinus from 2009 to 2012 to construct a length-based statistical model giving the probability that a non - developing female was skipping spawning, as opposed to not being sexually mature. This model was then applied on demographic winter survey data from the Barents Sea from 1989 to 2014. This indicated large annual variation in skipping numbers. Comparing these survey estimates to the total annual ICES stock numbers, we found that skipping peaked in the years 1994–1996 and 2009–2014, when the median yearly estimate of skipped spawners was 20–45 % of all females aged ≥ 3 years. In contrast, only ∼ 3 % of females at age ≥ 3 years skipped spawning in 2007. The proportional representation of skipped spawners at the stock level appeared linked to stock energy reserves with more skipping occurring when energy levels were low. Skipping also became more frequent with increasing population age, i.e. when immatures were less abundant, although the very largest/oldest fish tended to spawn. Because the proportion of NEA haddock that skips spawning is variable and can be high, understanding variation in this phenomenon and its drivers may improve population dynamic models.
Mass coral bleaching events caused by elevated seawater temperatures result in extensive coral loss throughout the tropics, and are projected to increase in frequency and severity. If bleaching ...becomes an annual event later in this century, more than 90% of coral reefs worldwide may be at risk of long‐term degradation. While corals can recover from single isolated bleaching and can acclimate to recurring bleaching events that are separated by multiple years, it is currently unknown if and how they will survive and possibly acclimatize to annual coral bleaching. Here, we demonstrate for the first time that annual coral bleaching can dramatically alter thermal tolerance in Caribbean corals. We found that high coral energy reserves and changes in the dominant algal endosymbiont type (Symbiodinium spp.) facilitated rapid acclimation in Porites divaricata, whereas low energy reserves and a lack of algal phenotypic plasticity significantly increased susceptibility in Porites astreoides to bleaching the following year. Phenotypic plasticity in the dominant endosymbiont type of Orbicella faveolata did not prevent repeat bleaching, but may have facilitated rapid recovery. Thus, coral holobiont response to an isolated single bleaching event is not an accurate predictor of its response to bleaching the following year. Rather, the cumulative impact of annual coral bleaching can turn some coral species ‘winners’ into ‘losers’, and can also facilitate acclimation and turn some coral species ‘losers’ into ‘winners’. Overall, these findings indicate that cumulative impact of annual coral bleaching could result in some species becoming increasingly susceptible to bleaching and face a long‐term decline, while phenotypically plastic coral species will acclimatize and persist. Thus, annual coral bleaching and recovery could contribute to the selective loss of coral diversity as well as the overall decline of coral reefs in the Caribbean.
Abstract
Assessment of embryo quality and viability has traditionally been based on morphological evaluation. However, morphological evaluation, though somewhat reliable, is subjective in nature and ...varies greatly depending upon the skill and experience of the evaluator. Although research has been conducted with the goal of identifying more accurate and objective methods of evaluation, the issue of repeatability and consistency in predicting the likelihood of a successful pregnancy remains. Previous research has proposed the ability to utilize specific gravity to predict developmental energy reserves based on embryonic weight, theoretically identifying those embryos with an increased chance of success following standard embryonic transfer. The objective of this study was to determine if specific gravity could accurately identify those embryos that were most likely to succeed in generating positive pregnancies. Bovine embryos (n = 20) were dropped through media in a specific gravity chamber. Utilizing an embryo tracking software program, researchers recorded the time elapsed as the embryos descended 1 cm through the media. Embryos were then transferred into recipient cattle, and pregnancy was detected via ultrasound approximately 40 days post transfer. Of the 20 embryos transferred, 12 resulted in positive pregnancies. Descent times of these positive pregnancies ranged from 25.96 to 90.27 seconds, with an average descent time of 59.72 seconds. An analysis of the relationship between descent time and pregnancy outcome showed no significant difference (P > 0.05). Although there was no significance in the findings of this study, additional trials will be performed to thoroughly evaluate the potential of this technology as an objective measurement of embryonic viability.
The risks of depletion of energy reserves and encountering lethally low temperatures are considered as two important mortality factors that may limit winter survival of mosquito, Culex pipiens f. ...pipiens populations. Here we show that the autumn females carry lipid reserves, which are safely sufficient for at least two overwintering periods, provided the females diapausing at temperatures typical for underground spaces (0 °C - 8 °C) would continuously rest at a standard metabolic rate (SMR). The overwintering females, however, switch from SMR to much higher metabolic rate during flight, either seeking for optimal microhabitat within the shelter or in response to disturbances by air current or predator attack. These behaviors result in fast oxidation of lipid reserves and, therefore, the autumn load of energy reserves may actually limit winter survival under specific circumstances. Next, we show that the level of females' cold hardiness is physiologically set relatively weak for overwintering in open field, above-ground habitats, but is ecologically entirely sufficient for overwintering in most underground spaces. The characteristics of suitable overwintering shelters are: no or limited risk of contact with ice crystals, no or limited air movements, winter temperatures relatively stable between +2 and + 6 °C, winter minimum does not drop below −4 °C for longer than one week, or below −8 °C for longer than 1 day.
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•Diapausing females of Culex pipiens arrive to winter shelters (cellars) with lipid reserves.•Lipids theoretically suffice for more than 500 days spent in shelter at standard metabolic rate.•Frequency of flights within shelter will decide whether the reserves suffice practically.•Physiological limits of females' cold hardiness are set relatively weak for survival in above ground microhabitats.•Physiological limits of cold hardiness guarantee safe overwintering in underground microhabitats.
Recently, the use of biodegradable and environment friendly plant-based bioinsecticides has received a great deal of attention from researchers to control insect disease vectors. The aim of this ...research is to determine the larvicidal efficacy of Ruta graveolens essential oil against third instar larvae of two species of mosquito (Culex pipiens and Culiseta longiareolata) and a biological model Drosophila melanogaster.
Culiseta longiareolata and Culex pipiens larvae were collected from untreated areas located in Tebessa and Drosophila melanogaster, the wild strain collected from rotten apples in the Tebessa region. Ruta graveolens essential oil has been tested at different concentrations between 2.5μ/mL and 140μL/mL against third instar larvae of the three species under standard laboratory conditions according to the recommendations from the Word Health Organization. The effects were examined on mortality, growth and the main components (proteins, carbohydrates, lipids).
The essential oil showed larvicidal activity with LC
and LC
values (10.85μL/mL, 70.95μL/mL and 39.4μL/mL), (26μL/mL, 144.5μL/mL and 89.57μL/mL) against third instar larvae of Drosophila melanogaster, Culex pipiens and Culiseta longiareolata respectively. In addition, it disrupted the growth and several morphological malformations were observed. It also affected growth and the main components (proteins, carbohydrates, lipids).
The essential oil affected growth and energy reserves for all three species. The results indicated that the essential oil of Ruta graveolens has good potential as a source of natural larvicides.
Offspring size is a key functional trait that can affect all phases of the life history, from birth to reproduction, and is common to all the Metazoa. Despite its ubiquity, reviews of this trait tend ...to be taxon‐specific. We explored the causes and consequences of offspring size variation across plants, invertebrates and vertebrates.
We find that offspring size shows clear latitudinal patterns among species: fish, amphibians, invertebrates and birds show a positive covariation in offspring size with latitude; plants and turtles show a negative covariation with latitude. We highlight the developmental window hypothesis as an explanation for why plants and turtles show negative covariance with latitude. Meanwhile, we find evidence for stronger, positive selection on offspring size at higher latitudes for most animals.
Offspring size also varies at all scales of organization, from populations through to broods from the same female. We explore the reasons for this variation and suspect that much of this variation is adaptive, but in many cases, there are too few tests to generalize.
We show that larger offspring lose relatively less energy during development to independence such that larger offspring may have greater net energy budgets than smaller offspring. Larger offspring therefore enter the independent phase with relatively more energy reserves than smaller offspring. This may explain why larger offspring tend to outperform smaller offspring but more work on how offspring size affects energy acquisition is needed.
While life‐history theorists have been fascinated by offspring size for over a century, key knowledge gaps remain. One important next step is to estimate the true energy costs of producing offspring of different sizes and numbers.
A plain language summary is available for this article.
Plain Language Summary
Woody plant species store nonstructural carbohydrates (NSCs) for many functions. While known to buffer against fluctuations in photosynthetic supply, such as at night, NSC stores are also thought to ...buffer against environmental extremes, such as drought or freezing temperatures by serving as either back‐up energy reserves or osmolytes. However, a clear picture of how NSCs are shaped by climate is still lacking. Here, we update and leverage a unique global database of seasonal NSC storage measurements to examine whether maximum total NSC stores and the amount of soluble sugars are associated with clinal patterns in low temperatures or aridity, indicating they may confer a benefit under freezing or drought conditions. We examine patterns using the average climate at each study site and the unique climatic conditions at the time and place in which the sample was taken. Altogether, our results support the idea that NSC stores act as critical osmolytes. Soluble Sugars increase with both colder and drier conditions in aboveground tissues, indicating they can plastically increase a plants' tolerance of cold or arid conditions. However, maximum total NSCs increased, rather than decreased, with average site temperature and had no relationship to average site aridity. This result suggests that the total amount of NSC a plant stores may be more strongly determined by its capacity to assimilate carbon than by environmental stress. Thus, NSCs are unlikely to serve as reservoir of energy. This study is the most comprehensive synthesis to date of global NSC variation in relation to climate and supports the idea that NSC stores likely serve as buffers against environmental stress. By clarifying their role in cold and drought tolerance, we improve our ability to predict plant response to environment.
We updated a global database of nonstructural carbohydrate (NSC) measurements of woody trees and examined how they vary with climate.
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