Thermal tolerance and preference of exploited turbinid snails near their range limit in a global warming hotspot

Predicted global climate change has prompted numerous studies of thermal tolerances of marine species. The upper thermal tolerance is unknown for most marine species, but will determine their vulnerability to ocean warming. Gastropods in the family Turbinidae are widely harvested for human consumption. To investigate the responses of turbinid snails to future conditions we determined critical thermal maxima (CTMax) and preferred temperatures of Turbo militaris and Lunella undulata from the tropical-temperate overlap region of northern New South Wales, on the Australian east coast. CTMax were determined at two warming rates: 1 °C/30 min and 1 °C/12 h. The number of snails that lost attachment to the tank wall was recorded at each temperature increment. At the faster rate, T. militaris had a significantly higher CTMax (34.0 °C) than L. undulata (32.2 °C). At the slower rate the mean of both species was lower and there was no significant difference between them (29.4 °C for T. militaris and 29.6 °C for L. undulata). This is consistent with differences in thermal inertia possibly allowing animals to tolerate short periods at higher temperatures than is possible during longer exposure times, but other mechanisms are not discounted. The thermoregulatory behaviour of the turban snails was determined in a horizontal thermal gradient. Both species actively sought out particular temperatures along the gradient, suggesting that behavioural responses may be important in ameliorating short-term temperature changes. The preferred temperatures of both species were higher at night (24.0 °C and 26.0 °C) than during the day (22.0 °C and 23.9 °C). As the snails approached their preferred temperature, net hourly displacement decreased. Preferred temperatures were within the average seasonal seawater temperature range in this region. However, with future predicted water temperature trends, the species could experience increased periods of thermal stress, possibly exceeding CTMax and potentially leading to range contractions.     

The effects of increased constant incubation temperature and cumulative acute heat shock exposures on morphology and survival of Lake Whitefish (Coregonus clupeaformis) embryos

Increasing incubation temperatures, caused by global climate change or thermal effluent from industrial processes, may influence embryonic development of fish. This study investigates the cumulative effects of increased incubation temperature and repeated heat shocks on developing Lake Whitefish (Coregonus clupeaformis) embryos. We studied the effects of three constant incubation temperatures (2 °C, 5 °C or 8 °C water) and weekly, 1-h heat shocks (+3 °C) on hatching time, survival and morphology of embryos, as these endpoints may be particularly susceptible to temperature changes. The constant temperatures represent the predicted magnitude of elevated water temperatures from climate change and industrial thermal plumes. Time to the pre-hatch stage decreased as constant incubation temperature increased (148 d at 2 °C, 92 d at 5 °C, 50 d at 8 °C), but weekly heat shocks did not affect time to hatch. Mean survival rates and embryo morphometrics were compared at specific developmental time-points (blastopore, eyed, fin flutter and pre-hatch) across all treatments. Constant incubation temperatures or +3 °C heat-shock exposures did not significantly alter cumulative survival percentage (~50% cumulative survival to pre-hatch stage). Constant warm incubation temperatures did result in differences in morphology in pre-hatch stage embryos. 8 °C and 5 °C embryos were significantly smaller and had larger yolks than 2 °C embryos, but heat-shocked embryos did not differ from their respective constant temperature treatment groups. Elevated incubation temperatures may adversely alter Lake Whitefish embryo size at hatch, but weekly 1-h heat shocks did not affect size or survival at hatch. These results suggest that intermittent bouts of warm water effluent (e.g., variable industrial emissions) are less likely to negatively affect Lake Whitefish embryonic development than warmer constant incubation temperatures that may occur due to climate change.     

Impact of fluctuating temperatures on development of the koinobiont endoparasitoid Venturia canescens

The effect of temperature on the biology of Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae) is well understood under constant temperature conditions, but less so under more natural, fluctuating conditions. Herein we studied the influence of fluctuating temperatures on biological parameters of V. canescens. Parasitized fifth-instar larvae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) were reared individually in incubators at six fluctuating temperature regimes (15–19.5 °C with a mean of 17.6 °C, 17.5–22.5 °C with a mean of 19.8 °C, 20–30 °C with a mean of 22.7 °C, 22.5–27.5 °C with a mean of 25 °C, 25.5-32.5 °C with a mean of 28.3 °C and 28.5–33 °C with a mean of 30 °C) until emergence and death of V. canescens adults. Developmental time from parasitism to adult eclosion, adult longevity and survival were recorded at each fluctuating temperature regime. In principle, developmental time decreased with an increase of the mean temperature of the fluctuating temperature regime. Upper and lower threshold temperatures for total development were estimated at 34.9 and 6.7 °C, respectively. Optimum temperature for development and thermal constant were 28.6 °C and 526.3 degree days, respectively. Adult longevity was also affected by fluctuating temperature, as it was significantly reduced at the highest mean temperature (7.0 days at 30 °C) compared to the lowest one (29.4 days at 17.6 °C). Survival was low at all tested fluctuating temperatures, apart from mean fluctuating temperature of 25 °C (37%). Understanding the thermal biology of V. canescens under more natural conditions is of critical importance in applied contexts. Thus, predictions of biological responses to fluctuating temperatures may be used in population forecasting models which potentially influence decision-making in IPM programs.     

The effect of acclimation temperature on thermal activity thresholds in polar terrestrial invertebrates

In the Maritime Antarctic and High Arctic, soil microhabitat temperatures throughout the year typically range between ?10 and +5 °C. However, on occasion, they can exceed 20 °C, and these instances are likely to increase and intensify as a result of climate warming. Remaining active under both cool and warm conditions is therefore important for polar terrestrial invertebrates if they are to forage, reproduce and maximise their fitness. In the current study, lower and upper thermal activity thresholds were investigated in the polar Collembola, Megaphorura arctica and Cryptopygus antarcticus, and the mite, Alaskozetes antarcticus. Specifically, the effect of acclimation on these traits was explored. Sub-zero activity was exhibited in all three species, at temperatures as low as ?4.6 °C in A. antarcticus. At high temperatures, all three species had capacity for activity above 30 °C and were most active at 25 °C. This indicates a comparable spread of temperatures across which activity can occur to that seen in temperate and tropical species, but with the activity window shifted towards lower temperatures. In all three species following one month acclimation at ?2 °C, chill coma (=the temperature at which movement and activity cease) and the critical thermal minimum (=low temperature at which coordination is no longer shown) occurred at lower temperatures than for individuals maintained at +4 °C (except for the CTmin of M. arctica). Individuals acclimated at +9 °C conversely showed little change in their chill coma or CTmin. A similar trend was demonstrated for the heat coma and critical thermal maximum (CTmax) of all species. Following one month at ?2 °C, the heat coma and CTmax were reduced as compared with +4 °C reared individuals, whereas the heat coma and CTmax of individuals acclimated at +9 °C showed little adjustment. The data obtained suggest these invertebrates are able to take maximum advantage of the short growing season and have some capacity, in spite of limited plasticity at high temperatures, to cope with climate change.     

Similar metabolic rate-temperature relationships after acclimation at constant and fluctuating temperatures in caterpillars of a sub-Antarctic moth

Temperature compensation in whole-animal metabolic rate is one of the responses thought, controversially, to characterize insects from low temperature environments. Temperature compensation may either involve a change in absolute values of metabolic rates or a change in the slope of the metabolic rate – temperature relationship. Moreover, assessments of compensation may be complicated by animal responses to fluctuating temperatures. Here we examined whole animal metabolic rates, at 0 °C, 5 °C, 10 °C and 15 °C, in caterpillars of the sub-Antarctic moth, Pringleophaga marioni Viette (Tineidae), following one week acclimations to 5 °C, 10 °C and 15 °C, and fluctuating temperatures of 0–10 °C, 5–15 °C, and 10–20 °C. Over the short term, temperature compensation was found following acclimation to 5 °C, but the effect size was small (3–14%). By comparison with caterpillars of 13 other lepidopteran species, no effect of temperature compensation was present, with the relationship between metabolic rate and temperature having a Q₁₀ of 2 among species, and no effect of latitude on temperature-corrected metabolic rate. Fluctuating temperature acclimations for the most part had little effect compared with constant temperatures of the same mean value. Nonetheless, fluctuating temperatures of 5–15 °C resulted in lower metabolic rates at all test temperatures compared with constant 10 °C acclimation, in keeping with expectations from the literature. Absence of significant responses, or those of large effect, in metabolic rates in response to acclimation, may be a consequence of the unpredictable temperature variation over the short-term on sub-Antarctic Marion Island, to which P. marioni is endemic.     

Temperature-dependent development of Lista haraldusalis (Walker) (Lepidoptera: Pyralidae) on Platycarya strobilacea

The effect of constant temperatures on development and survival of Lista haraldusalis (Walker) (Lepidoptera: Pyralidae), a newly reported insect species used to produce insect tea in Guizhou province (China), was studied in laboratory conditions at seven temperatures (19 °C, 22 °C, 25 °C, 28 °C, 31 °C, 34 °C, and 37 °C) on Platycarya strobilacea. Increasing the temperature from 19 °C to 31 °C led to a significant decrease in the developmental time from egg to adult emergence, and then the total developmental time increased at 34 °C. Egg incubation was the stage where L. haraldusalis experienced the highest mortality at all temperatures. The survival of L. haraldusalis was significantly higher at 25 °C and 28 °C, whereas none of the eggs hatched at 37 °C. Common and Ikemoto linear models were used to describe the relationship between the temperature and the developmental rate for each immature stage of L. haraldusalis. The estimated values of the lower temperature threshold and thermal constant of the total immature stages using Common and Ikemoto linear models were 11.34 °C and 11.20 °C, and 939.85 and 950.41 degree-days, respectively. Seven nonlinear models were used to fit the experimental data to estimate the developmental rate of L. haraldusalis. Based on the biological significance for model evaluation, Ikemoto linear, Logan-6, and SSI were the best models that fitted each immature stage of L. haraldusalis and they were used to estimate the temperature thresholds. These thermal requirements and temperature thresholds are crucial for facilitating the development of factory-based mass rearing of L. haraldusalis.     

Effect of thermal stress on metabolic and oxidative stress biomarkers of Hoplosternum littorale (Teleostei,Callichthyidae)

The present study aimed to investigate in Hoplosternum littorale (Hancock, 1828) the effects of different water temperatures (10 °C, 25 °C-control group- and 33 °C) on physiologic and metabolic traits following acute (1 day) and chronic (21 days) exposures. We analyzed several biomarker responses in order to achieve a comprehensive survey of fish physiology and metabolism under the effect of this natural stressor. We measured morphological indices, biochemical and hematological parameters as well as oxidative stress markers. To evaluate energy consumption, muscle and hepatic total lipid, protein and glycogen concentrations were also quantified. Extreme temperatures exposures clearly resulted in metabolic adjustments, being liver energy reserves and plasma metabolites the most sensitive parameters detecting those changes. We observed reduced hepatosomatic index after acute and chronic exposure to 33 °C while glycogen levels decreased at both temperatures and time of exposure tested. Additionally, acute and chronic exposures to 10 °C increased liver lipid content and plasma triglycerides. Total protein concentration was higher in liver and lower in plasma after chronic exposures to 10 °C and 33 °C. Acute exposition at both temperatures caused significant changes in antioxidant enzymes tested in the different tissues without oxidative damage to lipids. Antioxidant defenses in fish failed to protect them when they were exposed for 21 days to 10 °C, promoting higher lipid peroxidation in liver, kidney and gills. According to multivariate analysis, oxidative stress and metabolic biomarkers clearly differentiated fish exposed chronically to 10 °C. Taken together, these results demonstrated that cold exposure was more stressful for H. littorale than heat stress. However, this species could cope with variations in temperature, allowing physiological processes and biochemical reactions to proceed efficiently at different temperatures and times of exposure. Our study showed the ability of H. littorale to resist a wide range of environmental temperatures and contributes for the understanding of how this species is adapted to environments with highly variable physicochemical conditions.     

Behavioral thermoregulation and critical thermal limits of giant keyhole limpet Megathura crenulata (Sowerby 1825) (Mollusca; Vetigastropoda)

The thermoregulatory behavior of the giant keyhole limpet Megathura crenulata was determined in a horizontal thermal gradient during the day at 18.9 °C and 18.3 °C for the night. The final preferendum determined for giant keyhole limpets was of 18.6±1.2 °C.Limpets' displacement velocity was 10.0±3.9 cm h⁻¹ during the light phase and 8.4±1.6 cm h⁻¹ during the dark phase. The thermotolerance (measured as CTMax at 50%) was determined in a keyhole limpet in three acclimation temperatures 17, 20, and 23 °C. Limpets were subjected to water increasing temperatures at a rate of 1 °C every 30 min, until they detached from the substrate. The critical thermal maximum at 50% was 27.2, 27.9 and 28.3 °C respectively.     

The in vitro effect of temperature on motility and antioxidant response of common carp Cyprinus carpio spermatozoa

The effect of temperature on Cyprinus carpio spermatozoa in vitro was investigated with spermatozoa activated at 4, 14, and 24 °C. At 30 s post-activation, motility rate was significantly higher at 4 °C compared to 14 and 24 °C, whereas highest swimming velocity was observed at 14 °C. The thiobarbituric acid-reactive substance (TBARS) content was significantly higher at 14 °C and 24 °C than at 4 °C in motile spermatozoa. No significant differences in catalase and superoxide dismutase activity relative to temperature were observed. This study provides new information regarding effect of temperature on lipid peroxidation intensity and spermatozoon motility parameters in carp. The elevation of TBARS seen at higher temperatures could be due to inadequate capacity of antioxidant enzymes to protect the cell against the detrimental effects of oxidative stress induced by higher temperatures.     

Development response of Spodoptera exigua to eight constant temperatures: Linear and nonlinear modeling

Temperature-dependent development of Spodoptera exigua (Hübner) were evaluated at eight constant temperatures of 12, 15, 20, 25, 30, 33, 34 and 36 °C with a variation of 0.5 °C on sugar beet leaves. No development occurred at 12 °C and 36 °C. Total developmental time varied from 120.50 days at 15 °C to 14.50 days at 33 °C. As temperature increased from 15 °C to 33 °C, developmental rate (1/developmental time) of S. exigua increased but declined at 34 °C. The lower temperature threshold (T_min) was estimated to be 12.98 °C and 12.45 °C, and the thermal constant (K) was 294.99 DD and 311.76 DD, using the traditional and Ikemoto–Takai linear models, respectively. The slopes of the Ikemoto–Takai linear model for different immature stages were different, violating the assumption of rate isomorphy. Data were fitted to three nonlinear models to predict the developmental rate and estimate the critical temperatures. The T_min values estimated by Lactin-2 (12.90 °C) and SSI (13.35 °C) were higher than the value estimated by Briere-2 (8.67 °C). The estimated fastest development temperatures (T_fast) by the Briere-2, Lactin-2 and SSI models for overall immature stages development of S. exigua were 33.4 °C, 33.9 °C and 32.4 °C, respectively. The intrinsic optimum temperature (T_Φ) estimated from the SSI model was 28.5 °C, in which the probability of enzyme being in its native state is maximal. The upper temperature threshold (T_max) values estimated by these three nonlinear models varied from 34.00 °C to 34.69 °C. These findings on thermal requirements can be used to predict the occurrence, number of generations and population dynamics of S. exigua.     

Unusual change in activity pattern at cool temperature in a reptile (Sphenodon punctatus)

Animals that can be active both during day and night offer unique opportunities to identify factors that influence activity pattern. By experimental manipulations of temperatures under constant photoperiod, we aimed to determine if emergence, activity and thermoregulatory behaviour of juvenile tuatara (Sphenodon punctatus) varied at different temperatures (20 °C, 12 °C and 5 °C). To help clarify its activity pattern, we compared tuatara with two lizard species endemic of the South Island of New Zealand for which activity pattern is known and clearly defined: the nocturnal common gecko Woodworthia “Otago/Southland” and the diurnal McCann׳s skink Oligosoma maccanni. Tuatara showed similar responses to both species of lizards. Similar to the diurnal skinks, tuatara emerged quickly at 20 °C and 12 °C while nocturnal geckos took more time to emerge. Like nocturnal geckos, tuatara continued to be active at 5 °C, but only during the day. Interestingly, tuatara shifted from diurno-nocturnal activity at 20 °C and 12 °C to being strictly diurnal at 5 °C. We suggest that this temperature-dependent strategy maximises their survival during cold periods.     

Some like it hot: Mouse temperature preferences in laboratory housing

In standard laboratory environments mice are housed at 20–24 °C. However, their thermoneutral zone ranges between 26 °C and 34 °C. This challenge to homeostasis is by definition stressful, and could therefore affect many aspects of physiology and behavior. We tested the hypothesis that mice under standard laboratory conditions are not housed at a preferred temperature, and predicted that this would be evident in thermotaxis and other behavioral responses to ambient cage temperature. We assessed the temperature preferences of C57BL/6J mice in standard laboratory housing from 4 to 11 weeks of age. Forty-eight mice (24 male and 24 female in groups of three) all born on the same day were randomly assigned to one of eight age treatments. One cage of males and one cage of females were tested each consecutive week. Mice were tested in a set of three connected cages with each cage's temperature set using a water bath. On days 1–3 each group of mice was acclimated to each of the three temperatures (20 °C, 25 °C, or 30 °C) in a random order. Then each group was given free access to all temperatures on days 4–6, and video taped continuously. The location of each mouse and the occurrence of three behavioral categories (Active, Inactive, and Maintenance) were recorded by instantaneous scan samples every 10 min over the 3 days, and time budgets calculated. While both sexes chose warmer temperatures overall (P < 0.001), they preferred warmer temperatures only for maintenance and inactive behavior (P < 0.001). This effect was most pronounced in females (P = 0.017). As temperature selection varied with time of day (P < 0.001), these behavioral differences cannot be due to ambient temperature dictating behavior. We conclude that C57BL/6J mice at 20–24 °C are not housed at their preferred temperature for all behaviors or genders, and that it may not be possible to select a single preferred temperature for all mice.     

Culture temperature affects gene expression and metabolic pathways in the 2-methylisoborneol-producing cyanobacterium Pseudanabaena galeata

A volatile metabolite, 2-methylisoborneol (2-MIB), causes an unpleasant taste and odor in tap water. Some filamentous cyanobacteria produce 2-MIB via a two-step biosynthetic pathway: methylation of geranyl diphosphate (GPP) by methyl transferase (GPPMT), followed by the cyclization of methyl-GPP by monoterpene cyclase (MIBS). We isolated the genes encoding GPPMT and MIBS from Pseudanabaena galeata, a filamentous cyanobacterium known to be a major causal organism of 2-MIB production in Japanese lakes. The predicted amino acid sequence showed high similarity with that of Pseudanabaena limnetica (96% identity in GPPMT and 97% identity in MIBS). P. galeata was cultured at different temperatures to examine the effect of growth conditions on the production of 2-MIB and major metabolites. Gas chromatograph–mass spectrometry (GC–MS) measurements showed higher accumulation of 2-MIB at 30 °C than at 4 °C or 20 °C after 24 h of culture. Real-time-RT PCR analysis showed that the expression levels of the genes encoding GPPMT and MIBS decreased at 4 °C and increased at 30 °C, compared with at 20 °C. Furthermore, metabolite analysis showed dramatic changes in primary metabolite concentrations in cyanobacteria grown at different temperatures. The data indicate that changes in carbon flow in the TCA cycle affect 2-MIB biosynthesis at higher temperatures.     

Comparative analysis of milk fat decomposition activity by Mrakia spp. isolated from Skarvsnes ice-free area,East Antarctica

Milk fat curdle is difficult to remove from sewage. In an attempt to identify an appropriate agent for bio-remediation of milk fat curdle, Mrakia strains were collected from the Skarvsnes ice-free area of Antarctica. A total of 27 strains were isolated and tested for their ability to decompose milk fat at temperatures ranging from 4 °C to 15 °C. All strains could decompose milk fat at 4 °C and 10 °C. Phylogenetic analysis and comparison of the decomposition ability of milk fat (DAMF) revealed that the DAMF may be useful for predicting the outcome of phylogenetic analysis based on ITS sequences.     

Developmental temperature responses of Chrysoperla agilis (Neuroptera: Chrysopidae), a member of the European carnea cryptic species group

Chrysoperla agilis Henry et al. is one of the five cryptic species of the carnea group found in Europe. Identification of these species is mainly based on the distinct mating signals produced by both females and males prior to copulation, although there are also morphological traits that can be used to distinguish among different cryptic species. Ecological and physiological cryptic species-specific differences may affect their potential as important biological agents in certain agroecosystems. To understand the effects of temperature on the life-history traits of C. agilis preimaginal development, adult longevity and reproduction were studied at seven temperatures. Temperature affected the development, survival and reproduction of C. agilis. Developmental time ranged from approximately 62 days at 15 °C to 15 days at 30 °C. Survival percentages ranged from 42% at 15 °C to 76% at 27 °C. One linear and five nonlinear models (Briere I, II, Logan 6, Lactin and Taylor) used to model preimaginal development were tested to describe the relationship between temperature and developmental rate. Logan 6 model fitted the data of egg to adult development best according to the criteria adopted for the model evaluation. The predicted lower developmental threshold temperatures were 11.4 °C and 11.8 °C (linear model), whereas the predicted upper threshold temperatures (Logan 6 model) were 36.6 and 36.9 °C for females and males, respectively. Adult life span, preoviposition period and lifetime cumulative oviposition were significantly affected by temperature. The effect of rearing temperature on the demographic parameters is well summarized with the estimated values of the intrinsic rate of increase (r_m) which ranged from 0.0269 at 15 °C to 0.0890 at 32 °C and the highest value recorded at 27 °C (0.1530). These results could be useful in mass rearing C. agilis and predicting its population dynamics in the field.     

Germination response and viability of an endangered tropical conifer Widdringtonia whytei seeds to temperature and light

The tropical conifer Widdringtonia whytei Rendle is an endangered species endemic to Mulanje Mountain in Malawi. A study was conducted for the first time under controlled conditions in order to assess the effects of temperature and light on germination and viability of W. whytei seeds. Seeds incubated at a constant temperature of 20 °C attained the highest cumulative germination percentage (100%) followed by 87% germination under fluctuating temperatures of 15 °C night/25 °C day. No seed germination occurred at temperatures below 15 °C. Seeds that failed to germinate at temperatures below 15 °C showed the highest (> 90%) viability compared to the seeds incubated at 25 °C (60%). Across temperature regimes, germination was significantly higher under light (44.7%) than dark (35.6%) conditions. It is concluded that temperature is one of the critical factors for germination of W. whytei seed. The ability of W. whytei seeds to germinate both in light and darkness implies that the species would unlikely form a persistent soil seed bank, an attribute which is common in species that survive in habitats frequently disturbed by fires.     

Metal complexes of crosslinked chitosans: Correlations between metal ion complexation values and thermal properties

A series of heavy metal complexes of crosslinked chitosans were evaluated by thermogravimetric studies. The metal complexes with Cu, Cd and Hg ions exhibiting the highest complexing ability to chitosans (Hg 354–364, Cu 100–112, and Cd 121–160, in mg/g chitosan), had the lowest onset of degradation temperatures (range 194–210 °C) and the lowest final degradation temperatures (generally less than 294–304 °C for Hg, 296–338 °C for Cu, and 305–368 °C for Cd complexes). Mn ion, with the lowest binding to chitosans (Mn 5–7 mg/g), showed the reverse behavior, having onset (240–248 °C) and final degradation temperatures (range 300–368 °C). Zn (binding 74–87 mg/g) and Pb (binding 39–62 mg/g) ions have a binding ability intermediate to Cu/Cd/Hg and Mn extremes, and therefore the effects on onset and final degradation temperatures are intermediate to these values.     

Effects of different temperatures on the life history of Evania appendigaster L. (Hymenoptera: Evaniidae), a solitary oothecal parasitoid of Periplaneta americana L. (Dictyoptera: Blattidae)

The influence of temperatures on the life parameters of the solitary oothecal parasitoid Evania appendigaster, was investigated in the laboratory. Parasitized oothecae of Periplaneta americana were left to develop under seven constant temperatures: 15, 17, 20, 25, 30, 35, and 40 °C. At the end, we found that: (i) E. appendigaster was able to complete development within the temperature range of 17–34 °C; (ii) mean adult longevity decreased as temperature increased, with the temperature of 40 °C being fatal in a matter of hours; (iii) males lived longer than females between 15 and 30 °C; (iv) adult emergence rate was the highest at 25 °C, and (v) no wasps emerged at 15 or 40 °C. Non-emerged oothecae contained either unhatched eggs or dead larvae. We determined the theoretical lower developmental threshold and thermal constant for the complete development as 12.9 °C and 584.8 day-degrees for males, and 13.1 °C and 588.2 day-degrees for females, respectively. A good balance between faster development, maximum adult longevity and good egg viability was obtained between 25–30 °C, and that would be the best temperature range for rearing E. appendigaster.     

Incubation temperature affects hatching success,embryonic expenditure of energy and hatchling phenotypes of a prolonged egg-retaining snake,Deinagkistrodon acutus (Viperidae)

We used eggs of Deinagkistrodon acutus to study the effects of incubation temperature on hatching success, embryonic expenditure of energy and hatchling phenotypes. One egg from each of the 15 fertile clutches was dissected for determination of egg composition, and a total of 164 eggs were incubated at five constant temperatures. Embryonic mortality increased dramatically at 30 °C, and none of eggs incubated at 32 °C hatched. Within the range from 24 to 30 °C, temperature affected incubation length and most hatchling traits examined. The mean incubation length at 24, 26, 28 and 30 °C was 36.4, 28.7, 21.8 and 15.7 days, respectively. Embryos developing at higher temperatures (28 and 30 °C) consumed more energy but produced less developed (and hence smaller) hatchlings, which characteristically had larger residual yolks but smaller carcasses. A principal component analysis resolved two components (with eigenvalues ⩾1) from ten size (initial egg mass)-free hatchling variables, accounting for 79.3% of variation in the original data. The first component (43.8% variance explained) had high positive loading for size-free values of dry mass, lipid mass, energy contents and ash mass of hatchlings, and the second component (35.5% variance explained) had high positive loading for size-free values of SVL, carcass dry mass and fatbody dry mass. Hatchlings from different incubation temperatures did not differ in scores on the first axis of the principal component analysis, whereas hatchlings from higher incubation temperatures (28 and 30 °C) had significantly lower scores on the second axis than did those from lower incubation temperatures (24 and 26 °C). As the second axis mainly represents traits relating to the developmental condition at hatching, the analysis therefore provided further evidence that eggs incubated at higher temperatures produced less developed hatchlings. Taken together, our data show that the optimal temperatures for embryonic development are relatively low in D. acutus largely due to its use of relatively cool habitats.     

Effect of rearing temperature on growth and thermal tolerance of Schizothorax (Racoma) kozlovi larvae and juveniles

Effect of rearing temperature on growth and thermal tolerance of Schizothorax (Racoma) kozlovi Nikolsky larvae and juveniles was investigated. The fish (start at 12 d post hatch) were reared for nearly 6 months at five constant temperatures of 10, 14, 18, 22 and 26 °C. Then juvenile fish being acclimated at three temperatures of 14, 18 and 22 °C were chosen to determine their critical thermal maximum (CTMax) and lethal thermal maximum (LTMax) by using the dynamic method. Growth rate of S. kozlovi larvae and juveniles was significantly influenced by temperature and fish size, exhibiting an increase with increased rearing temperature, but a decline with increased fish size. A significant ontogenetic variation in the optimal temperatures for maximum growth were estimated to be 24.7 °C and 20.6 °C for larvae and juveniles of S. kozlovi, respectively. The results also demonstrated that acclimation temperature had marked effects on their CTMax and LTMax, which ranged from 32.86 °C to 34.54 °C and from 33.79 °C to 34.80 °C, respectively. It is suggested that rearing temperature must never rise above 32 °C for its successful aquaculture. Significant temperature effects on the growth rate and thermal tolerance both exhibit a plasticity pattern. Determination of critical heat tolerance and optima temperature for maximum growth of S. kozlovi is of ecological significance in the conservation and aquaculture of this species.