Influence of ambient temperature on maternal thermoregulation and neonate phenotypes in a viviparous lizard, Eremias multiocellata, during the gestation period

To assess the potential gestational effects on post-hatching morphology, locomotor performance, and early growth rate, we maintained gravid Eremias multiocellata under four constant treatment temperatures (25, 29, 31, and 35 °C). Ambient temperature had significant effects on some morphometric traits of offspring, including tail length, head size, forelimb length and hindlimb length, but not on body mass or snout-vent length. The data of females' body temperature indirectly support the maternal manipulation hypothesis. Juvenile E. multiocellata had better locomotor performance and faster early growth rate at 29 °C than at the other three treatment temperatures (25, 31, and 35 °C). Our results suggest that gestation temperature may be optimized at 29 °C for E. multiocellata from Tianzhu, Gansu Province, China.     

Effect of gestation temperature on sexual and morphological phenotypes of offspring in a viviparous lizard, Eremias multiocellata

It has been documented in some reptiles that thermal environment can induce variation in sex ratio and morphological phenotypes of offspring. Here, the viviparous lizards (Eremias multiocellata) were maintained under different temperatures during pregnancy to test the effects of this treatment on sexual and morphological phenotypes of offspring, and to investigate whether this lizard is subject to temperature-dependent sex determination (TSD). The warmer temperatures resulted in shorter gestation periods and a higher ratio of male: female births; however, gestation temperature did not affect the neonates’ body mass or snout–vent length (SVL). The gestation temperatures also had significant effects on the mean litter size. Therefore, our results show that the viviparous lizard E. multiocellata might be a TSD species, providing the mothers the opportunity to manipulate the sex ratio of their offspring.     

A novel incubator to simulate the natural thermal environment of sea turtle eggs

A novel sea turtle egg incubator was developed in which the heating element is placed above the clutch, which more closely simulates solar heating in nature. An electronic thermometer in conjunction with a thermostat located in sand beneath a heater plate was used to obtain the desired temperature in the placed eggs, as compared to previous methods of controlling global temperature within the interior of a chamber. To test the new incubator, Lepidochelys olivacea eggs were incubated under different thermal conditions in order to identify the temperature-dependent sex determination (TSD) period more precisely. Four incubation experiments were designed to test the performance of the incubator where the temperature was lowered from 32 to 28 °C during 60 h and then reestablished at 32 °C until hatching occurred. A significant mean hatching success rate of 89.6% was obtained for all the experiments. The main result from these preliminary findings was that the sex determination period to produce males was reduced from 15 (days 15–30) to eight days (days 19–27). Overall, the incubator provides precise control and simulates a natural thermal environment that may improve control of TSD in sea turtles.     

Embryonic development rate and hatchling phenotypes in the Chinese three-keeled pond turtle (Chinemys reevesii): The influence of fluctuating temperature versus constant temperature

Although the effects of constant temperatures on hatchling traits have been extensively studied in reptiles, the effects of fluctuating temperatures remain poorly understood. Eggs of the Chinese three-keeled pond turtle (Chinemys reevesii) were incubated at a constant temperatures (28 °C) and two fluctuating temperatures (28±3 °C and 28±6 °C) to test for the influence of thermal environment on incubation duration, hatchling traits, and post-hatching growth. Incubation duration was shorter at constant temperature than at fluctuating temperatures. The sex ratio of hatchlings varied among temperature treatments, with more females from 28±6 °C than from 28 °C. The size and mass were greater for hatchlings from a constant temperature than from fluctuating ones, but this difference in body size disappeared when the hatchlings were 3 months old. In addition, the swimming ability, survival, and growth of hatchlings from fluctuating temperatures did not differ from those of hatchlings from constant temperature, when they were kept at an artificial environment without food scarcity or predation. Therefore, the thermal environments with various temperature fluctuations used in this study do not significantly affect fitness-related hatchling traits in this species.     

Influence of dietary protein levels and water temperature on growth,body composition and nutrient utilization of Cirrhinus mrigala (Hamilton, 1822) fry

The experiment was conducted to determine the protein requirement of Cirrhinus mrigala fry at three different water temperatures, 28, 30 and 32 °C, and to investigate the influence of dietary protein levels and water temperatures on weight gain, body composition, food and nutrient utilization. The 36% protein concentration in the diet yielded highest weight gain at all temperatures from 28 to 32 °C. However, daily protein intake was lower at 28 °C than at 30 and 32 °C. The diet with 36% dietary protein and 32.17% carbohydrate produced the best weight gain and gross conversion efficiency (GCE) at 30 °C. The protein-sparing effect was observed at temperatures 30 and 32 °C in diets 1 and 2, having carbohydrate levels 37.36–44.91%. Highest protein efficiency ratio (PER) was recorded at 28% dietary protein level, while it was lowest at 40% dietary protein level in all three temperatures. Lipid in the body of fishes increased at the end of the experiment in comparison to the initial body lipid. The body protein was found to be related to daily protein intake at 30 and 32 °C. Significant difference (P<0.05) was also noted between temperatures, the hepatosomatic index (HSI) and viscerosomatic index (VSI). The diet with 36% dietary protein and 32.17% carbohydrate was observed to be the best diet for C. mrigala fry at 28–32 °C.     

Thermal dependence of reproductive allocation in a tropical lizard

In ectotherms, environmental temperature is the most prominent abiotic factor that modulates life-history traits. We explored the influence of environmental temperature on reproduction in the Madagascar ground gecko (Paroedura picta) by measuring reproductive traits of females at constant temperatures (24, 27, 30 °C). Females of this species lay clutches of one or two eggs within short intervals. For each female, we measured egg mass for the first five clutches. For one clutch, we also measured the energetic content of eggs via bomb calorimetry. Temperature positively influenced the rate of egg production, but females at 30 °C laid smaller eggs than did females at either 24 or 27 °C. Dry mass of eggs scaled allometrically with wet mass, but this relationship was similar among thermal treatments. Females at all temperatures produced eggs with similar energy densities. Females at 24 °C allocated less energy per time unit (≈8 mW) to reproduction than did females from higher temperatures (≈12 mW). However, females at either 24 or 27 °C allocated significantly more energy per egg than did females at 30 °C. Our results demonstrate that a complex thermal sensitivity of reproductive rate can emerge from distinct thermal sensitivities of egg size, egg composition and clutch frequency.     

Ambient temperature-dependent thermoregulatory role of REM sleep

Changes in ambient temperature produce complex effects on sleep–wakefulness. In order to find out the mechanisms involved in temperature-sensitive changes in sleep in rats, their thermal preference, body temperature and sleep were studied before and after the destruction of both peripheral and central warm receptors, by systemic administration of 375 mg/kg capsaicin. Though the pre-treated rats preferred to stay mostly at the ambient temperature of 27 °C, post-treated rats strayed freely into chambers having ambient temperature of 30 °C and 33 °C. Sleep and body temperature of these rats were studied for six hours each, when they were kept at an ambient temperature of 18–36 °C. Total sleep time, especially REM sleep, was maximum at 30 °C in pre-treated rats, but this REM sleep peak at 30 °C disappeared after capsaicin administration. Body temperature increased sharply in post-treated rats, at ambient temperatures above 30 °C. Apart from the ability to defend body temperature at high ambient temperature, avoidance of warm ambient temperature and increase in REM sleep are the behavioral measures which are lost in post-treated rats. Results of this study suggest that the ambient temperature-related increase in REM sleep at 30 °C could be part of the thermoregulatory measures.     

The effects of CO2 and chronic cold exposure on fecundity of female Drosophila melanogaster

Carbon dioxide and chilling are sometimes used to immobilise insects for laboratory research. Both of these methods are known to have short-term effects on behaviour and physiology in Drosophila, but their long-term impacts are unknown. We exposed female D. melanogaster adults to high CO₂ concentrations (4 h at 18,000 ppm) and chronic cold (72 h at 4 °C). The carbon dioxide exposure increased chill coma recovery time, but did not result in changes in offspring number, sex ratio, or size. By contrast, the cold exposure resulted in fewer, smaller offspring, and resulted in a male-biased sex ratio compared to controls. There was no significant interaction between CO₂ and cold. We conclude that although caution must be used in choosing an immobilisation method, CO₂ appears to have less long-term impact than cold.     

Diapause pupal color diphenism induced by temperature and humidity conditions in Byasa alcinous (Lepidoptera: Papilionidae)

We investigated whether diapause pupae of Byasa alcinous exhibit pupal color diphenism (or polyphenism) similar to the diapause pupal color polyphenism shown by Papilio xuthus. All diapause pupae of B. alcinous observed in the field during winter showed pupal coloration of a dark-brown type. When larvae were reared and allowed to reach pupation under short-day conditions at 18 °C under a 60 ± 5% relative humidity, diapause pupae exhibited pupal color types of brown (33%), light-brown (25%), yellowish-brown (21%), diapause light-yellow (14%) and diapause yellow (7%). When mature larvae reared at 18 °C were transferred and allowed to reach pupation at 10 °C and 25 °C under a 60 ± 5% relative humidity after a gut purge, the developmental ratio of brown and light-brown, yellowish-brown, and diapause light-yellow and diapause yellow types was 91.2, 8.8 and 0.0% at 10 °C, and 12.2, 48.8 and 39.0% at 25 °C, respectively. On the other hand, when mature larvae reared at 18 °C were transferred and allowed to reach pupation at 10 °C, 18 °C and 25 °C under an over 90% relative humidity after a gut purge, the developmental ratio of brown and light-brown, yellowish-brown, and diapause light-yellow and diapause yellow types was 79.8, 16.9 and 3.3% at 10 °C, 14.5, 26.9 and 58.6% at 18 °C, and 8.3, 21.2 and 70.5% at 25 °C, respectively. These results indicate that diapause pupae of brown types are induced by lower temperature and humidity conditions, whereas yellow types are induced by higher temperature and humidity conditions. The findings of this study show that diapause pupae of B. alcinous exhibit pupal color diphenism comprising brown and diapause yellow types, and suggest that temperature and humidity experienced after a gut purge are the main factors that affect the diapause pupal coloration of B. alcinous as environmental cues.     

Effect of water temperature on dietary protein requirement,growth and body composition of Asian catfish, Clarias batrachus fry

This study aimed to evaluate the protein requirement of Clarias batrachus fry, were estimated at two different water temperatures, 28 and 32 °C. The influence of dietary protein level and water temperature on body composition, weight gain, food and nutrient utilization were estimated. The Asian catfish, C. batrachus fry were fed four diets containing 28% (diet 1), 32% (diet 2), 36% (diet 3) and 40% (diet 4) protein levels and reared at two water temperatures 28 and 32 °C for 60 days. Fry fed with diet 3 containing 36% protein showed the highest mean final body weight at 32 °C. Final body weight was significantly (P<0.05) affected by dietary treatments and temperatures. Clarias batrachus fry raised at 28 °C had higher feed efficiency (93.20%) than the fry reared at 32 °C (87.58%) with 28% dietary protein level. Further, feed efficiency decreased with increase in dietary protein level. Higher daily protein retention (0.089%) observed at lower (0.0217 g) daily protein intake at 28 °C than 0.0283 g at 32 °C. While, optimal (0.0282 g) daily protein intake showed higher daily weight gain at 32 °C. Productive protein value (% PPV) was maximum (1.76%) at 32 °C than at 28 °C (0.76%). Final body lipid recorded higher value than initial body lipid at both the temperatures. Hepatosomatic index (HSI) observed to have been influenced (P<0.05) by diets and temperatures, while viscerosomatic index (VSI) affected (P<0.05) by only diets and not (P>0.05) by temperatures. The study concluded that the diet 3 containing 36% protein was optimal for growth of C. batrachus fry at both the temperatures.     

Geographic variation in diapause induction and termination of the cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

Overwintering diapause in Helicoverpa armigera, a multivoltine species, is controlled by response to photoperiod and temperature. Photoperiodic responses from 5 different geographical populations showed that the variation in critical photoperiod for diapause induction was positively related to the latitudinal origin of the populations at 20, 22 and 25 °C. Diapause response to photoperiod and temperature was quite different between northern and southern populations, being highly sensitive to photoperiod in northern populations and temperature dependence in southern populations. Diapause pupae from southern population showed a significantly shorter diapause duration than from northern-most populations when they were cultured at 20, 22, 25, 28 and 31 °C; by contrast, overwintering pupae from southern populations emerged significantly later than from northern populations when they were maintained in natural conditions, showing a clinal latitudinal variation in diapause termination. Diapause-inducing temperature had a significant effect on diapause duration, but with a significant difference between southern and northern populations. The higher rearing temperature of 22 °C evoked a more intense diapause than did 20 °C in northern populations; but a less intense diapause in southern population. Cold exposure (chilling) is not necessary to break the pupal diapause. The higher the temperature, the quicker the diapause terminated. Response of diapause termination to chilling showed that northern populations were more sensitive to chilling than southern population.     

Cold tolerance of the harlequin ladybird Harmonia axyridis in Europe

As an essential aspect of its invasive character in Europe, this study examined the cold hardiness of the harlequin ladybird Harmonia axyridis. This was done for field-collected populations in Belgium overwintering either in an unheated indoor or an outdoor hibernaculum. The supercooling point, lower lethal temperature and lower lethal time at 0 and −5 °C were determined. Possible seasonal changes were taken into account by monitoring the populations during each winter month. The supercooling point and lower lethal temperature remained relatively constant for the overwintering populations in the outdoor hibernaculum, ranging from −17.5 to −16.5 °C and −17.1 to −16.3 °C, respectively. In contrast, the supercooling point and lower lethal temperature of the population overwintering indoors clearly increased as the winter progressed, from −18.5 to −13.2 °C and −16.7 to −14.1 °C, respectively. A proportion of the individuals overwintering indoors could thus encounter problems surviving the winter due to premature activation at times when food is not available. The lower lethal time of field populations at 0 and −5 °C varied from 18 to 24 weeks and from 12 to 22 weeks, respectively. Morph type and sex had no influence on the cold hardiness of the overwintering adults. In addition, all cold tolerance parameters differed greatly between the laboratory population and field populations, implying that cold tolerance research based solely on laboratory populations may not be representative of field situations. We conclude from this study that the strong cold hardiness of H. axyridis in Europe may enable the species to establish in large parts of the continent.     

Thermoregulatory behavior and oxygen consumption of Octopus mimus paralarvae: The effect of age

Octopus mimus is an important cephalopod species in the coastal zone of Peru and Chile that is exposed to temperature variations from time to time due to El Niño/Southern Oscillation (ENSO) episodes when surface temperatures can reach 24 °C, 6 °C above typical temperatures in their habitat. The relationships between temperature and food availability are important factors that determine the recruitment of juveniles into the O. mimus population. The present study was to evaluate the relationship between thermoregulatory behavior and the age of paralarvae (summer population) to determine whether changes in this behavior occur during internal yolk consumption, making larvae more vulnerable to environmental temperature change. Oxygen consumption of paralarvae when 1–4 d old was determined to establish if respiration could be used to monitor the physiological changes that occur during yolk consumption. Horizontal thermal selection (17–30 °C), critical thermal maxima (CTMax), minima (CTMin), and oxygen consumption experiments were conducted with fasting paralarvae 1–4 d old at 20 °C. Preferred temperatures were dependent on the age of O. mimus paralarvae. One day old paralarvae selected a temperature 1.1 °C (23·4 °C) higher than 2 – 4 d old paralarvae (22·3 °C). The CTMax of paralarvae increased with age with values of 31·9±1.1 °C in 1-d-olds and 33·4±0.3 to 4-d-olds. CTMin also changed with age with low values in 2-d-old paralarvae (9.1±1·3 °C) and 11·9±0·9 °C in 4-d-old animals. The temperature tolerance range of paralarvae was age-dependent (TTD=difference between CTMax and CTMin) with higher values in 2 and 3 d old paralarvae (25–26 °C) as compared to 1 d old (23·1 °C) and 4 d old animals (22.7 °C). Oxygen consumption was not affected by the age of paralarvae, suggesting that mechanisms exist that compensate their metabloism until at least 4 d of age. The temperature tolerance range of a planktonic paralarvae of octopus species is presented for the first time. This range was dependent on the age of paralarvae, and so rendered the paralarvae more vunerable to a combination of high temperature and food deprivation during first days of life. Results in the present study provide evidence that O. mimus could be under ecological pressure if a climate change causes increased or decreased temperatures into their distribution range.     

Environmental sex determination in a splash pool copepod

The sex-determining mechanism has important demographic and genetic consequences by virtue of its effect on the population sex ratio. Here we investigate the effect of temperature dependent sex determination (TSD) on the primary sex ratio of the harpacticoid copepod, Tigriopus californicus . At the two experimental temperatures (15° and 22°C) used in this study, the primary sex ratio is almost always biased in favour of males. Higher temperatures induce masculinization and the change in sex ratio is not caused by differential mortality of the sexes. The mean level of TSD in the population is small (proportion of males increases by ~5% between 15° and 22°C) because only one-third of the families actually exhibit a significant sex-ratio response while the rest of the population is insensitive to temperature. A comparison of the primary sex ratio and the level of TSD between two locations reveals few differences among populations. Finally, individuals still exhibited TSD after having been maintained under constant temperature conditions in the lab for several generations. In addition the proportion of temperature-sensitive individuals remained unchanged. This suggests that the observed level of TSD is not an artefact of testing field-captured individuals in a novel laboratory environment. At this point the adaptive significance of temperature-dependent sex determination in T. californicus remains unknown.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 511–520.     

Evaporative water loss and energy metabolic in two small mammals,voles (Eothenomys miletus) and mice (Apodemus chevrieri), in Hengduan mountains region

Evaporative water loss (EWL) and energy metabolism were measured at different temperatures in Eothenomys miletus and Apodemus chevrieri in dry air. The thermal neutral zone (TNZ) of E. miletus was 22.5–30 °C and that of A. chevrieri was 20–27.5 °C. Mean body temperatures of the two species were 35.75±0.5 and 36.54±0.61 °C. Basal metabolic rates (BMR) were 1.92±0.17 and 2.7±0.5 ml O₂/g h, respectively. Average minimum thermal conductance (C_m) were 0.23±0.08 and 0.25±0.06 ml O₂/g h °C. EWL in E. miletus and A. chevrieri increased with the increase in temperature; the maximal EWL at 35 °C was 4.78±0.6 mg H₂O/g h in E. miletus, and 5.92±0.43 mg H₂O/g h in A. chevrieri. Percentage of evaporative heat loss to total heat production (EHL/HP) increased with the increase in temperature; the maximal EHL/HP was 22.45% at 30 °C in E. miletus, and in A. chevrieri it was 19.96% at 27.5 °C. The results may reflect features of small rodents in the Hengduan mountains region: both E. miletus and A. chevrieri have high levels of BMR and high levels of total thermal conductance, compared with the predicted values based on their body masses, while their body temperatures are relatively low. EWL plays an important role in temperature regulation.     

Low temperature induces the delivery of mature and immature CFTR to the plasma membrane

Deletion of phenylalanine 508 (ΔF508) is the most prevalent disease-causing mutation resulting in retention of the immature CFTR in the endoplasmic reticulum. The most common strategy to induce the delivery of ΔF508-CFTR to the surface of cells is by reducing the incubation temperature (≈28 °C). Cell surface biotinylation of HEK293T cells grown at 37 °C for 48 h, confirmed the presence of mature wild-type CFTR, but not ΔF508-CFTR at the cell surface. On the other hand, cells incubated at 28 °C for 16 h showed both mature and immature ΔF508-CFTR at their surface. The trafficking of immature ΔF508-CFTR, but not mature ΔF508-CFTR, to the cell surface occurred at low temperature even upon addition of BFA, suggesting the involvement of a Golgi-independent pathway. These results suggest that low temperature induces the appearance of a mix population of mature and immature CFTR molecules at the plasma membrane through distinct pathways.     

Do operational sex ratios influence sex allocation in viviparous lizards with temperature‐dependent sex determination?

Under certain environmental situations, selection may favour the ability of females to adjust the sex ratio of their offspring. Two recent studies have suggested that viviparous scincid lizards can modify the sex ratio of the offspring they produce in response to the operational sex ratio (OSR). Both of the species in question belong to genera that have also recently been shown to exhibit temperature-dependent sex determination (TSD). Here we test whether pregnant montane water skinks (Eulamprus tympanum) utilise TSD to select offspring sex in response to population wide imbalances in the OSR, by means of active thermoregulation. We use a combination of laboratory and field-based experiments, and conduct the first field-based test of this hypothesis by maintaining females in outdoor enclosures of varying OSR treatments throughout pregnancy. Although maternal body temperature during pregnancy was influenced by OSR, the variation in temperature was not great enough to affect litter sex ratios or any other phenotypic traits of the offspring.     

Respiration rate and oxy-regulatory capacity in cold stenothermal chironomids

The effects of temperature and oxygen saturation on the respiration rate of two cold stenothermal chironomids, Diamesa insignipes and Pseudodiamesa branickii were investigated. Fourth instar larvae were collected in winter in a glacio-rhithral stream (1300 m a.s.l., Alps, NE-Italy) and their respiration rate was measured with a Clark's electrode in the range 0-14 °C. The respiration rate was significantly higher in D. insignipes than in P. branickii at low temperatures (≤4 °C), higher in P. branickii between 8 and 12 °C and comparable at 14 °C. Higher values of R (regulation value), R_25% (respiration rate at 25% oxygen saturation) and b₁/b₂ (slope ratio in piecewise linear regression), and lower values of P_c (critical pressure) and I (initial decrease) were recorded in P. branickii than in D. insignipes. These values are compatible with oxy-regulatory behaviour in P. branickii, whereas D. insignipes appeared to be almost an oxy-conformer. On the basis of this autoecological information, new implications regarding survival of species from cold, high altitude habitats under changing climatic conditions are made.     

Variation in gestation length among captive reindeer (Rangifer tarandus tarandus)

An estimated 90% of reindeer females are mated in a 10- to 21-d interval and give birth in an equally synchronized manner. Reported gestation length in reindeer is highly variable (range, 203 to 240 d), almost twice the reindeer estrous cycle length. Previously, we identified a significant, negative relationship between gestation length and conception date in a small group of reindeer. In the current study, the negative relationship was investigated in a switchback design, where reindeer were divided into two groups synchronized for early and late mating over a 2-yr trial. Regression analysis of 11 paired observations produced a negative (P < 0.001) association between gestation length and conception date (slope = − 0.31). Dam weight at breeding and prior to parturition, calf birth weight, and calf sex were not significant variables in the regression. Regression analysis of a larger data set from two University of Alaska Fairbanks reindeer herds, where conception date (verified by systemic progesterone) and gestation length were recorded (historical data set), supported previous conclusions (n = 70; slope = −0.37; P < 0.001). Although the calf sex ratio did not differ with gestation length, there was a positive relationship (r² = 0.19; P = 0.014) between male birth weight and gestation length in the larger data set. The negative relationship between conception date and gestation length enhanced calving synchrony, though the limits of gestation plasticity and underlying mechanisms are not clear. The potential role of photoperiod on early embryonic development is discussed.     

Segregating variation for temperature-dependent sex determination in a lizard

Temperature-dependent sex determination (TSD) was first reported in 1966 in an African lizard. It has since been shown that TSD occurs in some fish, several lizards, tuataras, numerous turtles and all crocodilians. Extreme temperatures can also cause sex reversal in several amphibians and lizards with genotypic sex determination. Research in TSD species indicates that estrogen signaling is important for ovary development and that orthologs of mammalian genes have a function in gonad differentiation. Nevertheless, the mechanism that actually transduces temperature into a biological signal for ovary versus testis development is not known in any species. Classical genetics could be used to identify the loci underlying TSD, but only if there is segregating variation for TSD. Here, we use the ‘animal model'' to analyze inheritance of sexual phenotype in a 13-generation pedigree of captive leopard geckos, Eublepharis macularius, a TSD reptile. We directly show genetic variance and genotype-by-temperature interactions for sex determination. Additive genetic variation was significant at a temperature that produces a female-biased sex ratio (30 °C), but not at a temperature that produces a male-biased sex ratio (32.5 °C). Conversely, dominance variance was significant at the male-biased temperature (32.5 °C), but not at the female-biased temperature (30 °C). Non-genetic maternal effects on sex determination were negligible in comparison with additive genetic variance, dominance variance and the primary effect of temperature. These data show for the first time that there is segregating variation for TSD in a reptile and consequently that a quantitative trait locus analysis would be practicable for identifying the genes underlying TSD.