Transition from endogenous to exogenous feeding in longfin yellowtail Seriola rivoliana larvae under simultaneous effects of daily temperature fluctuation and rotifer Brachionus rotundiformis enrichment.

Daily temperature fluctuation interacts with the mean temperature to increase the toxicity of a pyrethroid insecticide in a moth

Effect of environmental daily temperature fluctuations over one year storage on the prediction of non-enzymatic browning in reduced-moisture foods stored at “ambient” temperature

Can Senegalese sole post-larvae effectively grow on low dietary DHA and lipid levels during weaning?

The littoral zone of lakes and lagoons is often used by fish for feeding or reproduction. However, the large changes in temperature that are typical of natural environments, including the littoral zone, represent a potential stressor for fish. Despite the importance of this habitat, little is known about the effect of daily temperature fluctuations on the stress responses of fish. We monitored daily temperature changes in the near-shore and offshore regions of a natural lagoon between May and July 2008–2010. We observed large temperature fluctuations more frequently in the near-shore zone than the offshore zone. We then exposed common carp (Cyprinus carpio) to a temperature regime similar to that observed in the near-shore zone and measured the levels of cortisol released into the water. The rate of cortisol release increased when carp were exposed to an increase in temperature of ~0.6°C/h over a 5-h period. Conversely, there was no change in the rate of release when temperatures decreased. Our results highlight the importance of maintaining high temporal resolution when evaluating the stress response to daily fluctuations temperature.

Corals and their associated microbiota form a “holobiont,” which includes symbiotic algae and other associated microbiota dominated by bacteria. The composition of holobiont is influenced by various environmental factors, such as increasing sea water temperatures. Previous studies of the effects of temperature changes on coral physiology and associated bacterial communities have been conducted based on stable water temperatures set by mean temperatures, or by slowly increasing/decreasing temperatures. However, the daily temperature fluctuations that corals experience in nature are not stable. The current understanding of the effects of large daily temperature fluctuations on coral and associated bacterial community dynamics is limited. Hence, we conducted a four-week tank experiment using different large daily temperature fluctuations (±5 °C and ±7 °C) accompanied by continuous warming conditions (26 °C to 29 °C) to investigate the effects on two common reef-building corals, Stylophora pistillata and Pocillopora acuta. During the experiment, the activity of coral host catalase and superoxide dismutase were measured, the photosynthetic ability of symbiotic algae was recorded, and the variation in bacterial communities was analyzed using the V6-V8 region of 16S rDNA. According to the results, different parts of the holobionts of two coral species exhibited varying response rates to the continuous warming conditions and diurnal temperature fluctuations. Additionally, it was found that diurnal temperature fluctuations may mitigate the heat stress on the host and reduce the changes in bacterial response to warming. Therefore, it is suggested that the holobionts of different coral species may adopt different adaptation and survival strategies in response to diurnal temperature fluctuations and warming. Finally, based on the response of these two coral species under the conditions of diurnal temperature fluctuations and continuous warming, Acinetobacter and Rhodobacteraceae were identified as potential indicator coral-associated bacteria. This is the first study to investigate the tripartite dynamic response of coral, symbiotic algae and bacteria to daily temperature fluctuations.

The aim of the present study was to investigate how EPA, DHA, and lipoic acid (LA) influence the different metabolic steps in the n-3 fatty acid (FA) biosynthetic pathway in hepatocytes from Atlantic salmon fed four dietary levels (0, 0.5, 1.0 and 2.0%) of EPA, DHA or a 1:1 mixture of these FA. The hepatocytes were incubated with [1-14C] 18:3n-3 in the presence or absence of LA (0.2mM). Increased endogenous levels of EPA and/or DHA and LA exposure both led to similar responses in cells with reduced desaturation andelongation of [1-14C] 18:3n-3 to 18:4n-3, 20:4n-3, and EPA, in agreement with reduced expression of the Δ6 desaturase gene involved in the first step of conversion. DHA production, on the other hand, was maintained even in groups with high endogenous levels of DHA, possibly due to a more complex regulation of this last step in the n-3 metabolic pathway. Inhibition of the Δ6 desaturase pathway led to increased direct elongation to 20:3n-3 by both DHA and LA. Possibly the route by 20:3n-3 and then Δ8 desaturation to 20:4n-3, bypassing the first Δ6 desaturase step, can partly explain the maintained or even increased levels of DHA production. LA increased DHA production in the phospholipid fraction of hepatocytes isolated from fish fed 0 and 0.5% EPA and/or DHA, indicating that LA has the potential to further increase the production of this health-beneficial FA in fish fed diets with low levels of EPA and/or DHA.

Clarifying the role of fire heat and daily temperature fluctuations as germination cues for Mediterranean Basin obligate seeders

Daily temperature fluctuations can magnify the toxicity of pesticides.

This study was undertaken to evaluate the effects of temperature fluctuations on growth rates, hematological indices and body composition of Acipenser baerii juvenile during a 120 day trial. A total of 120 juveniles (initial body weight: 132 ± 4.2 g) were stocked in triplicate groups (10 individual per replicate) in 12 fiberglass tanks (500 L capacity). Four temperature regimes were applied: The first group was maintained as control at constant 22 ± 0.6°C (mean temperature around which the temperature of the other test trials fluctuated). The second group was exposed to temperature fluctuations between 19 and 25°C over a 24 h cycle, starting with the upward part of the cycle during daytime (feeding period). The third group started the exposure of the 24 h temperature cycle at the higher value (at 25°C; declining over the daytime) while the fourth group was exposed to two complete daily cycles of the same temperature fluctuations (between 19 and 25°C). Biometry of fish (total length and weight) was determined monthly. Blood samples were also collected every month and body composition was determined at the end of the experiment. After 17 weeks final weights were significantly affected by the daily temperature fluctuations (P < 0.05). The highest final weight and SGR was recorded in regime 2 followed by the control. The Highest body protein and lowest body lipid were recorded in fish exposed to the fourth temperature regime (two full temperature cycles in 24 h). Fish reared under this temperature regime also showed significantly lower blood plasma glucose levels than the other treatments (P < 0.05). Hemoglobin and hematocrit content in blood samples were not affected by any of the tested daily temperature fluctuations (P > 0.05). The leukocyte count increased slightly in regimes 2 and 4 compared to regime 1 (control) but differences were not significant (P > 0.05). These results tentatively suggest that some temperature fluctuations on a daily cycle can improve growth rates and enhance the immune system in Acipencer baerii. However, the optimum frequency and amplitude for temperature undulations remain to be investigated in more detail.

To clarify the effects of daily temperature fluctuation on the growth, development, and reproduction of a migratory agricultural pest, Loxostege sticticalis, we calculated its life-table parameters under a photoperiod of L16:D8 with three daily constant temperatures (22, 25, 28 ℃) and three daily fluctuating temperatures (L25.5 ℃:D15 ℃ with a mean of 22 ℃, Ⅰ; L30 ℃:D15 ℃ with a mean of 25 ℃, Ⅱ; L34.5 ℃:D15 ℃ with a mean of 28 ℃, Ⅲ) by using the theory of two-sex life table. We predicted population dynamics of L. sticticalis in the following 100 days. Compared to daily constant temperatures of 22 ℃ and 25 ℃, the pupal duration of L. sticticalis under fluctuating temperature regimes Ⅰ and Ⅱ was significantly shortened by 3.0% and 5.5%, while egg production was significantly increased by 31.3% and 31.1%, respectively. Compared to the constant temperature of 22 ℃, fluctuating temperature regime Ⅰ significantly shortened the larval duration by 8.6%, and the population reached its maximum intrinsic rate of increase (r=0.076 d-1), finite rate of increase (λ=1.078 d-1), and net reproductive rate (R0=34.82). Larval survival rate, pupal weight, and body weight of new adult under daily fluctuating temperatures were all lower than those under the corresponding daily constant temperature treatments. Additionally, only 2.6% of L. sticticalis completed life cycle under fluctuating temperature regime Ⅲ. Under daily constant temperature treatments, the adult pre-oviposition period of L. sticticalis was shortened with increasing temperature, averaging a reduction of 0.30 d·℃-1. Under daily fluctuating temperature, the adult pre-oviposition period of L. sticticalis initially increased and then decreased with rising temperature, among which treatment Ⅱ exhibiting the longest period (5.36 days). We concluded that daily temperature fluctuation could increase the growth and development rate and enhance fecundity and fitness of L. sticticali. The extreme daytime temperature is not conducive to the occurrence of the L. sticticalis population.

Information from a field perspective on temperature thresholds related to physical dormancy (PY) alleviation and seed resistance to high temperatures of fire is crucial to disentangle fire- and non-fire-related germination cues. We investigated seed germination and survival of four leguminous species from a frequently burned open Neotropical savanna in Central Brazil. Three field experiments were conducted according to seed location in/on the soil: (1) fire effects on exposed seeds; (2) fire effects on buried seeds; and (3) effects of temperature fluctuations on exposed seeds in gaps and shaded microsites in vegetation. After field treatments, seeds were tested for germination in the laboratory, together with the control (non-treated seeds). Fire effects on exposed seeds decreased viability in all species. However, germination of buried Mimosa leiocephala seeds was enhanced by fire in an increased fuel load treatment, in which we doubled the amount of above-ground biomass. Germination of two species (M. leiocephala and Harpalyce brasiliana) was enhanced with temperature fluctuation in gaps, but this condition also decreased seed viability. Our main conclusions are: (1) most seeds died when exposed directly to fire; (2) PY could be alleviated during hotter fires when seeds were buried in the soil; and (3) daily temperature fluctuations in gaps also broke PY of seeds on the soil surface, so many seeds could be recruited or die before being incorporated into the soil seed banks. Thus seed dormancy-break and germination of legumes from Cerrado open savannas seem to be driven by both fire and temperature fluctuations.

To assess long-term impacts of global warming on species, there is growing interest in latitudinal intraspecific patterns in thermal adaptation. Yet, while both mean temperatures and daily temperature fluctuations (DTFs) are expected to increase under global warming, latitudinal differences in the effects of DTFs have not been documented. We tested whether low-latitude populations of an ectotherm deal better with greater DTF than high-latitude populations, especially at a high mean temperature close to the optimal temperature for growth where DTF causes exposure to extreme high temperatures. We evaluated the impact of DTFs when assessing the effect of gradual thermal evolution at the high latitude with a space-for-time substitution. We compared effects of both mean temperatures (20 and 24°C) and DTFs (constant=0°C, low=5°C and high=10°C) on growth rates between low-latitude and high-latitude populations of the damselfly Ischnura elegans in a common-garden experiment. DTFs, if anything, reduced growth and were generally stressful as indicated by reductions in body condition, antioxidant defence and metabolic rate, and increases in oxidative damage. Most negative effects of DTFs were only present at a mean of 24°C when too high temperatures were reached during a daily cycle. Notably, while 4°C warming was beneficial in terms of growth rate at both latitudes at a constant temperature regime, this changed in a negative effect at high DTF. Moreover, this modulating effect of the mean temperature by DTF differed between latitudes indicating local thermal adaptation. While 4°C warming at low DTF still caused faster growth in low-latitude larvae, it already slowed growth in high-latitude larvae. This supports the emerging insight that warming would increase growth in high-latitude larvae in the absence of DTF, yet would decrease growth in the more realistic scenarios with DTF. In contrast, a space-for-time substitution approach suggested that under gradual thermal evolution, the evolved high-latitude larvae would no longer suffer a growth reduction in the presence of DTF. Our study provided important proof-of-principle that jointly integrating gradual thermal evolution and the expected increase in DTF generates opposing predictions of effects of global warming on this ectotherm.

The costs of living in a thermal fluctuating environment for the tropical haematophagous bug, Rhodnius prolixus

Three types of subterranean spaces are described according to their depth and degree of isolation: (1) subsurface spaces in upper soil layers, in which daily temperature fluctuations penetrate; (2) shallow spaces in stony accumulations and in the void systems in rocks, in which daily temperature fluctuations do not reach; (3) deep subterranean spaces more isolated from the surface, developed in rock massifs, i.e. void systems, caves included, in which annual temperature fluctuations do not penetrate. The shallow spaces offer a microclimatic gradient between the soil surface, with great daily and annual temperature and moisture fluctuations, and stable environments in deep subterranean spaces. Shallow spaces represent the transition zone, in which gradual adaptation to the stable environment of deep subterranean spaces take place. All troglomorphic spiders in Central Europe occur in shallow subterranean spaces. It is evidenced, that subterranean forms can develop from species inhabiting: (1) forest litter; (2) various stony habitats (rocks, surface of scree fields); (3) the surroundings of mountain snow fields and (4) peatbogs.

Current and future daily temperature fluctuations make a pesticide more toxic: Contrasting effects on life history and physiology