Interaction between eggshell temperature and carbon dioxide concentration after day 8 of incubation on broiler chicken embryo development

Carbon dioxide (CO₂) is considered to be an important factor during incubation of eggs. Effects attributed to higher CO₂ concentrations during experiment might be due to confounding effects of other environmental conditions, such as incubation temperature. To disentangle effects of eggshell temperature (EST) and CO₂ concentration, an experiment was conducted. A total of 630 Cobb 500 hatching eggs from 37 to 45 wk commercial breeder flocks were collected and incubated according to treatments. The experiment was setup as a complete randomized 2 × 3 factorial design, resulting in 6 treatments. From day 8 of incubation onward, broiler eggs were exposed to one of two EST (37.8 or 38.9 °C) and one of three CO₂ concentrations (0.1, 0.4 or 0.8%). Eggs were incubated in climate-respiration chambers and metabolic heat production was determined continuously. At day 18 of incubation and at 6 h after hatching, embryo and chicken quality were determined by evaluation of organ weights, navel condition, blood metabolites and hepatic glycogen. Hatching time and chicken length at 6 h after hatching showed an interaction between EST and CO₂ concentration (both P = 0.001). Furthermore, no effect of CO₂ concentration was found on embryo development or chicken quality. Metabolic heat production between day 8 and 18 of incubation was not affected by either EST or CO₂. At day 18 of incubation, an EST of 38.9 °C resulted in a higher egg weight loss, longer embryos, higher yolk free body mass (YFBM) and lower heart weight than an EST of 37.8 °C (all P < 0.008). At 6 h after hatching, an EST of 38.9 °C resulted in a higher residual yolk weight and lower YFBM, liver weight and heart weight than an EST of 37.8 °C (all P < 0.003). Lactate, uric acid and hepatic glycogen were not affected by EST at either day 18 of incubation or at hatch. Glucose was not affected by EST at day 18 of incubation, but at hatch, it was higher at an EST of 37.8 °C than at an EST of 38.9 °C (P = 0.02). It can be concluded that effects of CO₂ concentration (at concentrations ≤0.8%) on embryonic development and chicken quality appear to be limited when EST is maintained at a constant level. Moreover, a higher EST from day 8 of incubation onward appears to negatively affect chicken quality at hatch.     

Energy reserves during food deprivation and compensatory growth in juvenile roach: the importance of season and temperature

The effect of 21 days of starvation, followed by a period of compensatory growth during refeeding, was studied in juvenile roach Rutilus rutilus during winter and summer, at 4, 20 and 27° C acclimation temperature and at a constant photoperiod (12L : 12D). Although light conditions were the same during summer and winter experiments and fish were acclimated to the same temperatures, there were significant differences in a range of variables between summer and winter. Generally winter fish were better prepared to face starvation than summer fish, especially when acclimated at a realistic cold season water temperature of 4° C. In winter, the cold acclimated fish had a two to three‐fold larger relative liver size with an approximately double fractional lipid content, in comparison to summer animals at the same temperature. Their white muscle protein and glycogen concentration, but not their lipid content, were significantly higher. Season, independent of photoperiod or reproductive cycle, was therefore an important factor that determined the physiological status of the animal, and should generally be taken into account when fish are acclimated to different temperature regimes. There were no significant differences between seasons with respect to growth. Juvenile roach showed compensatory growth at all three acclimation temperatures with maximal rates of compensatory growth at 27° C. The replenishment of body energy stores, which were utilized during the starvation period, was responsible for the observed mass gain at 4° C. The contribution of the different energy resources (protein, glycogen and lipid) was dependent on acclimation temperature. In 20 and 27° C acclimated roach, the energetic needs during food deprivation were met by metabolizing white muscle energy stores. While the concentration of white muscle glycogen had decreased after the fasting period, the concentrations of white muscle lipid and protein remained more or less constant. The mobilization of protein and fat was revealed by the reduced size of the muscle after fasting, which was reflected in a decrease in condition factor. At 20° C, liver lipids and glycogen were mobilized, which caused a decrease both in the relative liver size and in the concentration of these substrates. Liver size was also decreased after fasting in the 4° C acclimated fish, but the substrate concentrations remained stable. This experimental group additionally utilized white muscle glycogen during food deprivation. Almost all measured variables were back at the control level within 7 days of refeeding.     

Combined effects of temperature and cadmium on developmental parameters and biomarker responses in zebrafish (Danio rerio) embryos

To determine the interactions between temperature and cadmium on zebrafish (Danio rerio) development, fertilized eggs were exposed to combinations of three temperature levels (21 °C, 26 °C, and 33 °C) and six cadmium concentrations (0, 0.25, 0.5, 2.0, 5.0, and 10.0 mg/L). Endpoints used included LC₅₀ value (48 h), developmental rate, mortality, heart rate, hatching success, liver histopathology, embryo abnormalities, and heat shock protein (hsp) induction. Results showed a significant acceleration in the developmental rate with increasing temperature and irrespective of the presence of cadmium. Data on LC₅₀ and ELS-test revealed that simultaneous exposure to both cadmium ions and cold stress (21 °C) was highly detrimental to growing embryos, causing a pronounced mortality and a significant reduction in average heart rate and embryo hatchability. In contrast, no similar reactions to cadmium were observed in pre-hatched embryos exposed to both control (26 °C) and high temperature (33 °C), and this can be explained by the significantly higher expression of hsp (hsp70) in embryos at these temperatures. Upon hatching, however, the larvae showed increased sensitivity to cadmium. The severity of malformations in the post-hatched larvae was in the order: hot cadmium stress>cold cadmium stress>cadmium stress alone>no stress at all. Liver histopathology as well as depletion in glycogen reserves exhibited greater severity with increasing cadmium concentration, irrespective of temperature. The present study confirms that temperature effectively confounds cadmium toxicity and needs to be considered for the accurate prediction and assessment of cadmium-induced toxicity in fish.     

Hatching of Daphnia sexual eggs. II. The effect of age and a second stimulus

• 1 We examined the effect of age on the hatching response of Daphnia magna sexual eggs of specific families. For old eggs (>2 years), hatching characteristics were compared at two storage temperatures (4°C and 20°C). Also, the hatching response after a second dark incubation and subsequent incubation under conditions favourable for hatching was compared with that after the first stimulus.
• 2 Daphnia sexual eggs were found to remain viable for several (at least 4.5) years. The effect of age on the hatching rate was family dependent. At least in some families, hatching rate was higher for old (>2 years) than for young (<5 months) eggs. Low temperature (4°C) during dark incubation resulted in a higher hatching rate compared with incubation at 20°C.
• 3 The application of a second hatching stimulus resulted in a renewed hatching response. The overall hatching rate after the second stimulus was, however, lower than that of the first stimulus.
• 4 More than 80% of the hatchlings of young eggs appeared on Day 3 or 4, with minor between-family differences in time distribution of hatching. The timing of the response to hatching stimuli was more variable in old than in young eggs, with the average time at hatching being 6.4 instead of 4.0 days. The response to the application of hatching stimuli was also slower after the second stimulus compared with the first stimulus.

     

Effects of oxygen,carbon dioxide,and nitrogen on hatching behavior and hatching time in the katydid,Eobiana engelhardti subtropica Bey-Bienko (Orthoptera: Tettigoniidae)

The trigger for the hatching behavior and determination of hatching time of the katydids, Eobiana engelhardti subtropica (Orthoptera: Tettigoniidae) have been shown to be influenced by light–dark signals or temperature. In this study, I investigated the effects of oxygen, carbon dioxide, and nitrogen on the hatching behavior and hatching time of the katydid. Eggs rarely hatched under a constant temperature of 25°C and hatched sporadically at a constant temperature of 15°C under continuous light in the air. However, when eggs were exposed to 100% oxygen or a mixture of oxygen and nitrogen (2:1 or 1:1), hatching occurred within a few seconds. Hatching behavior was directly triggered by high concentrations of oxygen. It was inhibited by exposure to 100% carbon dioxide, 100% nitrogen, or a mixture of oxygen and nitrogen (1:2). The hatching time, determined by the temperature fall (transfer from 25°C to 15°C), was delayed by these gases, and was reset by the transfer back of eggs to the air. This suggests the existence of a time-measuring mechanism that is triggered by the transfer of eggs to the air. These results, indicating that hatching behavior was directly triggered by high concentrations of oxygen and that hatching time was set by the transfer from carbon dioxide or nitrogen to the air, are new findings to the best of my knowledge.     

Tolerance of young allis shad Alosa alosa (Clupeidae) to oxy-thermic stress

The ecology of the young stages of allis shad Alosa alosa is poorly documented, although they can be exposed to many pressures during their freshwater phase and their downstream migration. When passing through systems such as the Gironde-Garonne-Dordogne watershed (GGD, SW France), they can be subjected to high temperatures and low levels of oxygen (hypoxia). The aim of this work is to assess the tolerance of young Alosa alosa at four ages (c. 10, 30, 60 and 85 days old) by challenging them to different temperatures (18, 22, 26 and 28°C) together with decreasing oxygen saturation levels (from 100% to 30%). Survival of the 10-day-old individuals was not influenced by oxy-thermic conditions, but high stress levels were detected and perhaps this age class was too fragile regarding the constraint of the experimental design. Survival at 30 and at 60 days old was negatively influenced by the highest temperatures tested alone (from 26°C and from 28°C, respectively) but no effect was detected at 85 days old up to 28°C. A combined effect of temperature and oxygen level was highlighted, with heat accelerating survival decrease when associated with oxygen level depletion: essentially, survival was critical (<50%) at 30 days old at temperature ≥22°C together with 30% O₂; at 60 days old, at temperature = 28°C with 30% O₂; at 85 days old, at temperature ≥26°C with ≤40% O₂. Tolerance to oxy-thermic pressures appeared to be greater among the migratory ages (60 and 85 days old) than among the 30-day-old group. Based on environmental data recorded in the GGD system and on our experimental results, an exploratory analysis allowed a discussion of the possible impact of past oxy-thermic conditions on the local population dynamics between 2005 and 2018. The oxy-thermic conditions that may affect Alosa alosa at ages when they migrate downstream (60 and 85 days old) were not frequently recorded in this period, except in cases of extreme episodes of heat together with hypoxia that occurred in some years, in summertime in the turbidity maximum zone of the Gironde estuary (particularly in the year 2006). Interestingly, oxy-thermic conditions that are likely to threaten the 30-day-old individuals occurred more frequently in the lower freshwater parts of the GGD system between the years 2005 and 2018. In the context of climate change, a general increase in temperature is predicted, as well as more frequent and severe hypoxic events, therefore we suggest that local Alosa alosa population recruitment could encounter critical oxy-thermic conditions more frequently in the future if no adaptive management of water resources occurs.     

Metabolism of lipid and carbohydrate in sea urchin spermatozoa

When the dry sperm of the sea urchin, Hemicentrotus pulcherrimus, were diluted 100 times in artificial sea water at 0°C and at 20°C, they became motile and the levels of ATP and creatine phosphate decreased rapidly. The level of ADP hardly changed, and the AMP level increased after the dilution. After the dilution, the respiratory rate at 2°C was almost one fifth that of 20°C. Both phospholipid and glycogen were used for the energy sources in sea urchin sperm. The level of phospholipid was 10-fold higher than that of glycogen in the dry sperm. The phospholipid level decreased after dilution at 20°C, though the level hardly changed at 0°C, suggesting that phospholipid was hardly metabolized the lower temperature. The level of α -glycerophosphate increased at 20°C after the dilution but did not change at 0°C. The level of glycogen decreased after the dilution, regardless of the temperature. The glycolysis was also activated after the dilution. Of the intermediates of the tricarboxylic acid cycle, the citrate concentration increased at 0°C and the malate concentration also increased at 0°C and especially strongly at 20°C.     

Free amino acids in the late embryogenesis and pre-hatching stage of two coregonid fishes

Developing eggs of vendace (Coregonus albula L.) and whitefish (C. lavaretus L.) were experimentally delayed in hatching by incubation at low water temperature (1–2°). Some eggs were taken during this period to a water temperature which was gradually raised up to 8° to provoke mass hatching of embryos. The pattern of free amino acids was followed in eggs incubated at both temperatures. During a 56 days period, the content of several essential amino acids significantly decreased in eggs of both species. For instance, the lysine content dropped from 703 to 270 mg/g dry matter and the arginine content from 257 to 13.3 mg/100 g dry matter in whitefish eggs. A similar pattern of decreasing level of free amino acids in embryonated ova up to hatching was characteristic for essential amino acids and serine. Methionine was exceptional; its level remained approximately the same. On the other hand, non-essential amino acids showed a significant increase in concentration during the experimental period. For instance, the glycine level increased 4.9 and 2.1 times in whitefish and vendace eggs, respectively. Transfer of eggs to 8° accelerated the decrease of nearly all free amino acids before hatching. The consequence of such amino acid metabolism for newly hatched larvae is discussed.     

Remote effects of short-term neonatal hyperthermia in Krushinsky–Molodkina rats prone to audiogenic seizures strain

Using the audiogenic seizure prone Krushinsky–Molodkina rat strain, it was demonstrated that short-term (5 min) exposure of 14-day-old pups to an elevated temperature (42°C) resulted in a significant decrease in audiogenic seizure severity at the age of 1 month. Presumably, this effect is determined by the activation of the heat-shock protein system (stress proteins).     

Temperature affects the limitation of Daphnia magna by eicosapentaenoic acid,and the fatty acid composition of body tissue and eggs

1. Poikilothermic animals incorporate more polyunsaturated fatty acids (PUFAs) into their cellular membranes as temperature declines, suggesting an increased sensitivity to PUFA limitation in cool conditions. To test this we raised Daphnia magna at different temperatures and investigated the effect of varying dietary PUFA on life history parameters (i.e. growth, reproduction) and the PUFA composition of body tissue and eggs. 2. Upon a PUFA‐rich diet (Cryptomonas sp.) females showed higher concentrations of several ω3 PUFAs in their body tissue at 15 °C than at 20 °C and 25 °C, indicating a greater structural requirement for ω3 PUFAs at low temperature. Their eggs had an equal but higher concentration of ω3 PUFAs than their body tissue. 3. In a life history experiment at 15 and 20 °C we supplemented a diet of a PUFA‐free cyanobacterium with the ω3 PUFA eicosapentaenoic acid (EPA). The growth of D. magna was more strongly EPA limited at low temperature. A greater requirement for structural EPA at 15 °C was indicated by a steeper increase in somatic EPA content with dietary EPA compared to 20 °C. 4. At 20 °C the development of eggs to successful hatching was high when EPA was supplied to the mothers. At 15 °C the hatching success was generally poor, despite of a higher maternal provision of EPA to eggs, compared to that at 20 °C, suggesting that EPA alone was insufficient for proper neonatal development at the low temperature. The growth of offspring from mothers raised at 20 °C without EPA supplementation was very low, indicating that the negative effects of EPA deficiency can be carried on to the next generation. 5. The fatty acid composition of Daphnia sp. in published field studies shows increasing proportions of saturated fatty acids with increasing environmental temperature, whereas ω3 PUFAs and EPA show no clear pattern, suggesting that variations in dietary PUFA may mask temperature‐dependent adjustments in ω3 PUFA concentrations of cladocerans in nature.     

Glutathione depletion in isolated rat hepatocytes caused by styrene and the thermal degradation products of polystyrene

Depletion of reduced glutathione (GSH) was induced in isolated rat hepatocytes incubated with styrene or exposed for 120 min to products from oxidative thermal degradation of polystyrene. The depletion depended on the concentrations of styrene and on the degradation temperature. Styrene (1 mM) or products from degradation of polystyrene at 200°C (concentration of styrene in exposure atmosphere 0.7 ppm) had no detectable effect on glutathione levels in isolated hepatocytes. At higher degradation temperatures (250°C and 300°C, with styrene concentrations of 2.5 and 25 ppm, respectively) a rapid depletion was detected as well as with 3 mM styrene in incubation mixture. The latency of lactate dehydrogenase was affected neither by the polystyrene degradation products nor by the styrene added to the incubation mixture.     

Effect of temperature on insulin binding and action in cultured human fibroblasts

Insulin stimulation of glycogen synthase activity and insulin binding were measured in fibroblast monolayers at 24, 32, and 37°C. Insulin stimulation of %$\text{I}$ glycogen activity increased with increasing temperature. Maximum response was greater at 37°C than at 32°C, and half maximal stimulation required at 2.0 nM insulin at 37°C vs. 10nM at 32°C. Insulin stimulation of glycogen synthase was greater and somewhat faster at 37°C than at 32°C. No insulin effect was observed at 24°C. ¹²⁵I-insulin binding to monolayers became maximal in 15 min at 37°C, 60 min at 32°C, and 120 min at 24°C. However, insulin binding decreased with increasing temperature, and this decline was due to decreased numbers of receptors. Insulin binding and stimulation of glycogen synthase were comparable at 32°C, with half maxima at 10 nM, indicating no evidence of “spare” receptors. The data indicate that temperature effects on insulin binding and action in fibroblasts are not directly related. The results also suggest that a rate limiting step(s) of insulin action is temperature sensitive, and that this step is not insulin binding.     

Heart rate during development in the turtle embryo: effect of temperature

 Growth and development can occur over a wide range of physical conditions in reptiles. Cardiovascular function must be critical to this ability. However, information on cardiovascular function in developing reptiles is lacking. Previous work indicated that in reptiles the effects of temperature on growth and metabolism are largely restricted to early development. This study examined whether the previously observed effects of temperature and different perinatal patterns of metabolism observed in amniotic vertebrates are correlated with cardiovascular function. Embryonic and hatchling carcass mass, heart mass and heart rate (HR) were compared for snapping turtle eggs (Chelydra serpentina) incubated at 24 ° and 29 °C. Incubation time was shorter at 29 °C (56.2 days) than at 24 °C (71.1 days). Carcass and heart growth showed a sigmoidal pattern at both temperatures. However, cardiac growth showed a relative decrease as incubation proceeded. Incubation temperature significantly affected the HR pattern during development. The HR of embryos incubated at 24 °C was constant for most of incubation (51.8±4.8 min^-1). A small decrease was observed just prior to and a large decrease immediately following hatching (posthatch, 22.3±4.1 min^-1). At 29 °C embryonic HR was greater than at 24 °C early in development (72.3±3 min^-1). The HR steadily decreased to values equivalent to those at 24 °C. The HRs of 24 °C and 29 °C hatchlings were not different. Cardiac output (estimated as the product of heart mass and HR) increased rapidly during early development and then slowed dramatically at both temperatures. These data are consistent with the suggestion that temperature exerts its effects primarily early in development. Furthermore, the changes in cardiovascular function are correlated with metabolic changes in hatching vertebrates. Accepted:12 June 1996     

Effects of temperature during early life history on embryonic and larval development and growth in haddock

The effect of incubation temperature (2, 4, 6, 8 and 10° C) on haddock Melanogrammus aeglefinus development and growth during the embryonic period and in subsequent ontogeny in a common post‐hatch thermal environment (6° C) was investigated. Hatching times were inversely proportional to incubation temperature and ranged from 20·3 days at 2° C to 9·1 days at 10° C. Growth rates were directly proportional to incubation temperature during both the embryonic and larval periods. There was a significant decline in growth rates following hatch in all temperature groups. Compared to the endogenously feeding embryos, growth rates in the exogenous period declined by 4·4‐fold at 4° C to 3·9‐fold at 8° C, indicative of the demarcation between the endogenous and exogenous feeding periods. Yolk utilization varied from 17 days at 2° C to 6 days at 10° C and followed a three‐stage sigmoidal pattern with the initial lag period inversely proportional to incubation temperature. Time to 50% yolk depletion varied inversely with temperature but occurred 1–1·5 days post‐hatch at all temperatures. Additionally, the period between 10 and 90% yolk depletion also decreased with increased temperature. Overall developmental rate was sequential with and directly proportional (2·3‐fold increase) to incubation temperature while the time spent in each developmental stage was inversely proportional to temperature. Larger embryos tended to be produced at lower temperatures but this pattern reversed following hatch, as larvae from higher temperature groups grew more rapidly than those from other temperature groups. Larvae from all temperatures achieved a similar length (c.total length 4·5 mm) upon complete yolk absorption. The study demonstrated the significant impact that temperature has upon developmental and growth rates in both endogenous and exogenous feeding periods. It also illustrated that temperature changes during embryogenesis had significant and persistent effects on growth in subsequent ontogeny.     

The effect of volatile anaesthetics on levels of metabolites and on metabolic rate in brain

Anaesthesia with ether, halothane, methoxyflurane (Penthrane) and Ohio 347 (Ethrane) increased the energy stores in mouse brain as much as 1·7-fold above the control values. The greatest increases were observed in glucose and glycogen. Glucose-6-P was increased in some cases and UDP glucose was consistently lower in the anaesthetized animals. Hypothermia in conjunction with anaesthesia modified some of the observed changes. Hypothermia alone was associated with an increase in P-creatine and glucose and a decrease in UDPglucose in the brain. The cerebral metabolic rate was depressed by all the anaesthetic agents to about 50 per cent of the control value. When the body temperature was lowered to 25°, the cerebral metabolic rate fell to 73 per cent of the control rate. A temperature coefficient of 1·035 was calculated as the fractional change/degree between 25° and 34°.     

PRECONVULSIVE CHANGES IN BRAIN GLUCOSE METABOLISM FOLLOWING DRUGS INHIBITING GLUTAMATE DECARBOXYLASE

—Brain glucose and glycogen concentrations have been studied in mice treated with allylglycine, 4-deoxypyridoxine and isoniazid, and the effects compared with the preconvulsive increase in brain glucose and glycogen concentration that follows d , l -methionine sulphoximine treatment. Allylglycine (180 mg/kg), 4-deoxypyridoxine (250 mg/kg), isoniazid (150 mg/kg) and d ,l -methionine sulphoximine (300 mg/kg) when given to mice at room temperature, cause a fall in rectal temperature which can be prevented by maintaining the mice in an incubator at 33-34°C. An increase in brain glucose concentration is seen after allylglycine (+ 133%), d ,l -methionine sulphoximine (+ 113%) and 4-deoxypyridoxine (+ 70%) treatment when mice are kept at room temperature and killed before convulsions occur. This is associated with a rise in blood glucose concentration after allylglycine, but not after the other drugs. Preventing the fall in rectal temperature reduces, but does not abolish, the rise in brain glucose concentration seen after allylglycine, d ,l -methionine sulphoximine and 4-deoxypyridoxine. Brain glycogen concentration increases at room temperature after D,L-methionine sulphoximine and 4-deoxypyridoxine, but in mice with maintained body temperature only 4-deoxypyridoxine produces an increase in brain glycogen. Isoniazid does not increase brain glucose or glycogen at room temperature, but reduces their concentration in mice kept in the incubator. All four drugs are known to act on amino acid metabolism; d ,l -methionine sulphoximine potently inhibits glutamine synthetase whereas 4-deoxypyridoxine, allylglycine and isoniazid inhibit glutamate decarboxylase. The connection, if any, between a block in the further metabolism of glutamate and an increase in brain glucose and glycogen is unknown.     

Effect of temperature on the morphometric development of eggs in the prawn Macrobrachium americanum (Caridea: Palaemonidae) and larval success under experimental conditions

Abstract

This study evaluated the effect of temperature on morphometric features of the egg during the embryonic development of the prawn Macrobrachium americanum and the relationship with hatching and the survival of the larvae. Berried females were grouped (n = 3) and reared at three different temperatures, 26, 29, and 33 °C, for which seven developmental stages were recognized. At each stage, the apical and sagittal diameters of the eggs were measured, the volume was calculated, and the weights were recorded. Additionally, the duration of embryonic development, hatching percentage, and larval survival were determined. At 29 and 33 °C, the eggs’ volume increased by 50%, but at 26 °C, the increase was 25%. Larvae from eggs incubated at 33 °C died one day after hatching. At 29 °C, larvae survived until Zoea VII. Larvae from eggs incubated at 26 °C died at the end of Zoea I. The number of days of embryonic development was 20.5 ± 1.5 (26 °C), 15 ± 1 (29 °C), and 12 ± 1 (33 °C). A temperature of 29 °C was the most favorable for embryonic development in M. americanum.     

Thermotolerance of IVM‐derived bovine oocytes and embryos after short‐term heat shock

A series of experiments were designed to study the effect of elevated temperatures on developmental competence of bovine oocytes and embryos produced in vitro. In experiment 1, the effect of heat shock (HS) by a mild elevated temperature (40.5°C) for 0, 30, or 60 min on the viability of in vitro matured (IVM) oocytes was tested following in vitro fertilization (IVF) and culture. No significant difference was observed between the control (39°C) and the heat‐treated groups in cleavage, blastocyst formation, or hatching (P > 0.05). In experiment 2, when the HS temperature was increased to 41.5°C, neither the cleavage rate nor blastocyst development was affected by treatment. However, the rate of blastocyst hatching appeared lower in the HS groups (13% in control group vs. 3.9% and 5.6% in 30 min and 60 min, respectively; P < 0.05). When IVM oocytes were treated at 43°C prior to IVF (experiment 3), no difference was detected in blastocyst and expanded blastocyst development following heat treatment for 0, 15, or 30 min, but heat treatment of oocytes for 45 or 60 min significantly reduced blastocyst and expanded blastocyst formation (P < 0.05). In experiment 4, the thermotolerance of day 3 and day 4 bovine IVF embryos were compared. When embryos were pre‐treated with a mild elevated temperature (40.5°C) for 1 hr, and then with a higher temperature (43°C) for 1 hr, no improvement in thermotolerance of the embryos was observed as compared to those treated at 43°C alone. However, a higher thermotolerance was observed in day 4 than day 3 embryos. In conclusion, treatment at 43°C, but not 40.5°C or 41.5°C significantly reduced oocyte developmental competence. An increase in thermotolerance was observed from day 3 to day 4 of in vitro embryonic development, which corresponds to the maternal to zygotic transition of gene expression in bovine embryos. Mol. Reprod. Dev. 53:336–340, 1999. © 1999 Wiley‐Liss, Inc.     

Stage-specific effects of temperature and dietary protein on growth and survival of Manduca sexta caterpillars

The effects of temperature and dietary protein concentration on growth and survival of Manduca sexta L. (Lepidoptera: Sphingidae) caterpillars during different larval stages were examined. Sets of caterpillars were raised from hatching at one of five constant temperatures (18, 22, 26, 30 or 34°C) and on one of two artificial diets (low or high protein concentration). Mass gain, duration (development time) and mean growth rate were measured for each caterpillar for the 1st to 3rd stadia, the 4th stadium, and the 5th stadium. Temperature significantly affected mass gain during each larval stage, resulting in smaller mass gains at higher temperatures at each stage. This effect was strongest at high temperatures during the 5th stadium. Temperature significantly affected durations of each larval stage, but the effect varied among stages: for example, the duration of stadia 1–3 decreased continuously with increasing temperature, whereas the duration of the 5th stadium was shortest at 26–30°C and increased at lower and higher temperatures. The effect of temperature on mean growth rate changed dramatically across larval stages: maximal growth rate occurred at 34°C during the 1st to 3rd stadia, at 30°C during the 4th stadium and at 26°C during the 5th stadium. Higher dietary protein concentration significantly decreased the duration of stadia 1–3 and of the 4th stadium, but had no significant effect on the duration of the 5th stadium. Temperature and dietary protein had little effect on mortality rates during any larval stadium, with one exception: mortality during the 5th stadium increased dramatically at temperatures of 30 and 34°C. These results demonstrate that the effects of temperature and dietary protein concentration on growth, development and survival in M. sexta vary markedly in different larval stadia during development; 5th instar caterpillars are particularly sensitive to higher temperatures.     

Environmental factors affecting hatching of rotifer (Brachionus plicatilis) resting eggs

Hatching experiments were carried out on a population of Brachionus plicatilis (Dor strain) resting eggs produced in batch laboratory cultures under controlled conditions and then stored for at least one month at 4 °C in the dark. Light was found to be obligatory for termination of dormancy. Over the temperature range of 10–30 °C (at 9.0‰ salinity), hatching was optimal (40–70%) at 10–15 °C and decreased linearly with the rise in incubation temperature. Resting eggs incubated over a salinity range of 9–40‰ (at 15 °C) showed optimal hatching at 16‰. Incubation of resting eggs in distilled water permitted normal embryonic development, but neonates died at eclosion. Presence of algae, Chlorella stigmatophora (0.5 × 10⁶ cell ml^?1), was found to aid hatching.