Relating goat milk production according to the Normalized Difference Vegetation Index and precipitations in the Chaco forest throughout the 2016-2018 period

This work aimed to quantify and relate goat milk production and the Normalized Difference of Vegetation Index of the semiarid Chaco forest and the monthly average precipitation along the 2016-2018 period. The work was carried out in El Polear, in Santiago del Estero, Argentina. Even though the NDVI of the forest and its lower strata biomass productivity were affected by drought, its milk production curve remained unaffected. This may be due to the forest stability resulting from the deep rooted trees that includes, to the strategic displacement of the phenophase in its lower strata (broadleaves, herbaceous) in drought seasons and the adaptation to the changes in the goat diet selectivity before forage fluctuations. Winter NDVI peaks should be considered for new lines of research on their contribution to the energetic reserves of the goat component at the beginning of winter. Significant straight relationships (p<0.05) were found between the average goat milk production and the average monthly precipitation (r=0.64) as well as the NDVI and the semiarid Chaco forest (r=0.59). The resulting linear models involving goat milk production with both precipitation and NDVI had moderate and significant (p<0.05) explaining power (R2=0.41) and (R2=0.35), respectively. These models make the seasonal goat milk production predictable and the planning and the making decision process of both producers and the agroindustry easier.

Feeding and thermal conditioning enhance coral temperature tolerance in juvenile Pocillopora acuta

Scleractinian corals form the foundation of coral reefs by acquiring autotrophic nutrition from photosynthetic endosymbionts (Symbiodiniaceae) and use feeding to obtain additional nutrition, especially when the symbiosis is compromised (i.e. bleaching). Juvenile corals are vulnerable to stress due to low energetic reserves and high demand for growth, which is compounded when additional stressors occur. Therefore, conditions that favour energy acquisition and storage may enhance survival under stressful conditions. To investigate the influence of feeding on thermal tolerance, we exposed Pocillopora acuta juveniles to temperature (ambient, 27.4°C versus cool, 25.9°C) and feeding treatments (fed versus unfed) for 30 days post-settlement and monitored growth and physiology, followed by tracking survival under thermal stress. Feeding increased growth and resulted in thicker tissues and elevated symbiont fluorescence. Under high-temperature stress (31–60 days post-settlement; ca 30.1°C), corals that were fed and previously exposed to cool temperature had 33% higher survival than other treatment groups. These corals demonstrated reduced symbiont fluorescence, which may have provided protective effects under thermal stress. These results highlight that the impacts of feeding on coral physiology and stress tolerance are dependent on temperature and as oceans continue to warm, early life stages may experience shifts in feeding strategies to survive.

Southern king crab larval survival: from intra- and interfemale variations to a fishery-induced mortality

The southern king crab (Lithodes santolla) supports one of the most important fisheries in southern South America. Lecithotrophic larvae hatch over an extended period, in which brooding females can be fished, but must be discarded due to regulations. Larval mortality by female fishing was evaluated. Samples of newly hatched zoeae I were obtained the day before (control) and after female treatment (aerial exposure or aerial exposure + free fall). Independently of the mothers’ treatment, larvae survived less than those from the control, explained by the air-exposure effects. The intraclutch variability in larval survival and their variability in energetic reserves were studied. Females were maintained during the hatching period, and zoea I samples were taken during 3 successive days. We found high variation in larval survival within a single egg clutch and between different females, only ascribable to the initial larval glycogen content. The intraclutch variability in larval survival combined with extended hatching may be an adaptation that allows mothers to find an adequate substrate as larvae hatch and may constitute a diversified bet-hedging strategy.

Different amplitudes of temperature fluctuation induce distinct transcriptomic and metabolomic responses in the dung beetle Phanaeus vindex

ABSTRACTMost studies exploring molecular and physiological responses to temperature have focused on constant temperature treatments. To gain a better understanding of the impact of fluctuating temperatures, we investigated the effects of increased temperature variation on Phanaeus vindex dung beetles across levels of biological organization. Specifically, we hypothesized that increased temperature variation is energetically demanding. We predicted that thermal sensitivity of metabolic rate and energetic reserves would be reduced with increasing fluctuation. To test this, we examined the responses of dung beetles to constant (20°C), low fluctuation (20±5°C), or high fluctuation (20±12°C) temperature treatments using respirometry, assessment of energetic reserves and HPLC-MS-based metabolomics. We found no significant differences in metabolic rate or energetic reserves, suggesting increased fluctuations were not energetically demanding. To understand why there was no effect of increased amplitude of temperature fluctuation on energetics, we assembled and annotated a de novo transcriptome, finding non-overlapping transcriptomic and metabolomic responses of beetles exposed to different fluctuations. We found that 58 metabolites increased in abundance in both fluctuation treatments, but 15 only did so in response to high-amplitude fluctuations. We found that 120 transcripts were significantly upregulated following acclimation to any fluctuation, but 174 were upregulated only in beetles from the high-amplitude fluctuation treatment. Several differentially expressed transcripts were associated with post-translational modifications to histones that support a more open chromatin structure. Our results demonstrate that acclimation to different temperature fluctuations is distinct and may be supported by increasing transcriptional plasticity. Our results indicate for the first time that histone modifications may underlie rapid acclimation to temperature variation.

An Integrated Biomarker Approach Using Flounder to Improve Chemical Risk Assessments in the Heavily Polluted Seine Estuary

The objective of this study was to develop an integrative approach in ecotoxicology (from biomarkers to population genetics) to assess the ecological status of fish populations. Flounders (Platichthys flesus) collected after the spawning season in the heavily polluted Seine estuary were compared with the moderately polluted Bay of Douarnenez. The muscle energetic reserves were highly depleted in Seine vs. Douarnenez fish. The Seine fish displaying a reduced capacity to manage the oxidative stress and a higher energetic metabolism. An increase in the content of muscle membrane phospholipids (sphingomyelin, phosphatidylserine, free sterols) was detected in the Seine vs. Douarnenez fish. The data integration allowed to hypothesize relationships between membrane phospholipids, xenobiotic metabolism, bioenergetics, and antioxidant defence. The genetic diversity considering neutral markers was maintained in the heavily polluted Seine population compared with the Douarnenez population. Finally, we suggest that the high physiological cost of tolerance to toxicants in the Seine flounder population could compromise its capacity to respond in the future to an additional stressor like warming waters in shallow depth. Thus, this population could be submitted to an ecological risk.

Environmental conditions alter behavioural organization and rhythmicity of a large Arctic ruminant across the annual cycle

The existence and persistence of rhythmicity in animal activity during phases of environmental change is of interest in ecology, evolution and chronobiology. A wide diversity of biological rhythms in response to exogenous conditions and internal stimuli have been uncovered, especially for polar vertebrates. However, empirical data supporting circadian organization in behaviour of large ruminating herbivores remains inconclusive. Using year-round tracking data of the largest Arctic ruminant, the muskox ( Ovibos moschatus ), we modelled rhythmicity as a function of behaviour and environmental conditions. Behavioural states were classified based on patterns in hourly movements, and incorporated within a periodicity analyses framework. Although circadian rhythmicity in muskox behaviour was detected throughout the year, ultradian rhythmicity was most prevalent, especially when muskoxen were foraging and resting in mid-winter (continuous darkness). However, when combining circadian and ultradian rhythmicity together, the probability of behavioural rhythmicity declined with increasing photoperiod until largely disrupted in mid-summer (continuous light). Individuals that remained behaviourally rhythmic during mid-summer foraged in areas with lower plant productivity (NDVI) than individuals with arrhythmic behaviour. Based on our study, we conclude that muskoxen may use an interval timer to schedule their behavioural cycles when forage resources are low, but that the importance and duration of this timer are reduced once environmental conditions allow energetic reserves to be replenished ad libitum. We argue that alimentary function and metabolic requirements are critical determinants of biological rhythmicity in muskoxen, which probably applies to ruminating herbivores in general.

Metabolic responses to long-term food deprivation in subterranean and surface amphipods

A long-standing hypothesis in subterranean biology posits that organisms living in poor resource subsurface habitats can withstand long periods of bioenergetic shortages due to an innate reduced metabolic rate when compared to their epigean counterparts. However, previous studies have proposed that caves with ample energy resources may not evolve organisms with reduced metabolic rate. The equivocal nature of previous findings suggests that there is a need to compare food deprivation responses of subterranean and surface species in order to elucidate whether there are widespread adaptations to low energy systems in subterranean taxa. The purpose of the study was to examine patterns in basal metabolism and the effects of food deprivation in closely related subterranean- and epigean- amphipods, Stygobromus pecki and Synurella sp. from central and east Texas, USA, respectively. Basal metabolic rates (measured as O2 consumption) differed between species, with S. pecki having substantially lower rates than Synurella. Individuals of both species were food deprived for a pre-determined time interval and changes in total body protein, lipids, and carbohydrates were measured throughout food deprivation experiments. Stygobromus pecki had larger initial energy stores than Synurella and were more conservative in the use of energetic reserves over a prolonged period of food deprivation. Thus, it appears that although S. pecki are currently found in shallow phreatic and spring opening environments, they have maintained more efficient metabolic adaptations to deal with prolonged periods of food deprivation.

Scaling the risk landscape drives optimal life-history strategies and the evolution of grazing

Consumers face numerous risks that can be minimized by incorporating different life-history strategies. How much and when a consumer adds to its energetic reserves or invests in reproduction are key behavioral and physiological adaptations that structure communities. Here we develop a theoretical framework that explicitly accounts for stochastic fluctuations of an individual consumer’s energetic reserves while foraging and reproducing on a landscape with resources that range from uniformly distributed to highly clustered. First, we show that the selection of alternative life histories depends on both the mean and variance of resource availability, where depleted and more stochastic environments promote investment in each reproductive event at the expense of future fitness as well as more investment per offspring. We then show that if resource variance scales with body size due to landscape clustering, consumers that forage for clustered foods are susceptible to strong Allee effects, increasing extinction risk. Finally, we show that the proposed relationship between resource distributions, consumer body size, and emergent demographic risk offers key ecological insights into the evolution of large-bodied grazing herbivores from small-bodied browsing ancestors.

Relationship between early body condition, energetic reserves and fitness in an iteroparous insect

Body condition can be defined as the amount of energetic reserves present within an individual after structural size had been accounted for (i.e. relative amounts of energetic reserves), and estimated by Body Condition indices (BCIs)Several methods have been proposed to calculate BCIs. However, they have traditionally been validated in vertebrate studies and evidence of their power to predict fitness in invertebrates is scarce. Ideally, the use of a particular BCI in an animal population should be validated based on its ability to accurately reflect the relative amount of reserves available to the animal as well as its relationship to fitness.We aimed at increasing the variance in female body condition of Tenebrio molitor beetles by subjecting them to restricted or optimal food conditions at both the larval and/or adult stage. We then explored the predictive power of several BCIs on both the absolute and relative amount of lipids and sugars present in the insect’s body, and their link with adult fitness. Using an iteroparous income breeder allowed us to assess the relative effects of larval vs. adult access to nutritional resources on fecundity along several reproductive events.Simple measurements of phenotypically plastic traits (i.e. mass and volume) correlated well with absolute, but poorly with relative, measures of body reserves. Conversely, we found that BCIs that corrected for the interdependence between phenotypically plastic traits and structural size strongly correlated with relative amounts of body components.We found that even though the adult feeding treatment had a stronger effect, body condition at emergence, but not larval feeding treatment, also affected fecundity. Moreover, while the effect of the adult feeding treatment varied along time (i.e. egg laying rank), the effect of body condition at emergence remained constant.These results show that by carefully using simple morphometric measures and BCIs, it is possible to distinguish between the effects of structural size and body condition on fitness traits in invertebrates, and to show that an iteroparous income breeder can partially rely on its early energetic state for its later fecundity.