Estimating reaction norms for predictive population parameters,age specific mortality,and mean longevity in temperature‐dependent cohorts of Culex quinquefasciatus Say (Diptera: Culicidae)

Culex quinquefasciatus plays a major role in the transmission of important parasites and viruses throughout the world. Because temperature is an important limiting factor on growth and longevity of all mosquito species, estimating the reaction norms provides very important basic information for understanding both plasticity and individual variations of the population. In the present study, Cx. quinquefasciatus were maintained at five different constant temperatures (15°, 20°, 23°, 27°, and 30°C) for two subsequent generations. Reproductive population parameters in blood‐fed mated females and longevities of virgin and blood‐fed mated adults reared at different temperatures were compared for the two generations. Longevity increased as temperature decreased within a range of 15° to 30°C for the unmated adults, and 15° to 27°C for the mated and blood‐fed adults. Generation times were as long as 124.07 and 106.76 days for two subsequent generations reared at 15°C, and the highest intrinsic rate of increase (r_m) values were estimated at 0.22 and 0.18, respectively, from the cohorts reared at 27°C. For survival rates, reproductive rates (R₀), and r_m values, 30°C was found to be a critical temperature for this species. These cohorts produced the smallest amount of eggs (R₀= 5.06), r_m values decreasing across generations (from 0.11 to 0.06), and the survival rates from egg to adult were found to be insufficient (16.1 and 10.8%). Additionally, the rate of exponential increase with age and age specific mortalities (b) were calculated for the virgin cohorts. Age specific mortality rates increased as temperature decreased. The increase in mortality rates started to accelerate at 27°C and was more pronounced at 30°C, for both females and males. We estimated the coefficients of variation for the b values in which females have smaller coefficients than those of the males at all temperatures.     

Temperature-dependent energy allocation to growth in Antarctic and boreal eelpout (Zoarcidae)

Antarctic fishes display slower annual growth rates than congeneric species from temperate zones. For an analysis of growth in relation to energy turnover, body composition was analysed in two benthic fish species to establish a whole animal energy budget. The Antarctic eelpout, Pachycara brachycephalum, was maintained at 0, 2, 4 and 6°C and the boreal eelpout, Zoarces viviparus at 4, 6, 12 and 18°C. At maximum food supply the weight gain was highest for P. brachycephalum at 4°C. Routine metabolic rate in acclimated Antarctic eelpouts did not differ between temperatures, whereas in Z. viviparus maximized growth benefited from a reduction of metabolic energy demands at 12°C. The lipid content of liver declined with increasing temperature in both species. The thermal window for growth is based on food conversion efficiency and the level of metabolic energy demand and is limited according to the level of aerobic scope available between pejus temperatures.     

Experimental investigation of the effects of temperature and feeding regime on scale growth in Atlantic salmon Salmo salar post-smolts

Salmo salar post-smolts were reared in seawater under controlled laboratory conditions for 12 weeks. The fish were exposed to three constant temperature treatments (15, 10.5 and 6°C) and four feeding treatments (constant feeding, food withheld for 7 days, food withheld for 14 days and food withheld intermittently for four periods of 7 days). Scale growth was proportional to fish growth across all treatments, justifying the use of scale measurements as a proxy for growth during the early marine phase. The rate of circuli deposition was dependant on temperature and feeding regime and was generally proportional to fish growth but with some decoupling of the relationship at 15°C. Deposition rates varied from 4.8 days per circulus at 15°C (constant feeding) to 15.1 days per circulus at 6°C (interrupted feeding). Cumulative degree day (^°D) was a better predictor of circuli number than age, although the rate of circuli deposition ^°D⁻¹ was significantly lower at 6°C compared with 15 and 10.5°C. Inter-circuli distances were highly variable and did not reflect growth rate; tightly packed circuli occurred during periods without food when growth was depressed, but also during periods of rapid growth at 15°C. The results further current understanding of scale growth properties and can inform investigations of declining marine growth in S. salar based on interpretations of scale growth patterns.     

Bioenergetic model of planktivorous fish feeding, growth and metabolism: theoretical optimum swimming speed of fish larvae

The feeding activity of an individual fish larva is described by an equation which includes parameters for the area successfully searched, probability of food capture multiplied by the cross-sectional perceptive visual field, larval swimming speed and the time required to consume a unit of food energy. The proportion of ingested food energy used for metabolism increases exponentially with increasing swimming speed. The model predicts that food consumption rate increases asymptotically whereas metabolic rate increases exponentially. This results in a predicted growth rate curve that reaches a maximum at a certain swimming speed and decreases at both higher and lower speeds. The model can be used to predict the influence of type of prey, prey density, water temperature etc. on larval growth. An expression describing how many hours per day fish larvae must forage in order to grow at a certain daily body weight gain allows the limits of environmental conditions for positive, zero and negative growth rate to be set. Results of simulations demonstrated that the optimum swimming speed for maximum growth of coregonid larvae increased with an increase in food density, decrease in water temperature or decrease of prey vulnerability. At optimum ‘theoretical’ swimming speed an increase in water temperature from 5 to 17° C required the food density to be increased from 20 to 80 copepods l^?1 in order to maintain a daily growth increment of 2%. The minimum Artemia density required for maintenance metabolism increased from 10 to 30 items 1¹ over the same temperature increase from 5 to 17° C, and food densities required for 8% growth rates were 26 and 56 Artemia nauplii l^?1 at 5 and 17° C, respectively. Contrary to previous findings, results of the present study suggest that metabolic rates of actively feeding fish larvae may be from 5 to 50 times the standard metabolic rate: earlier studies suggested that a factor of 2–3 may be generally applicable.     

Effects of temperature and food level on growth and development of a planktonic water mite

We analysed the relative effects of food availability and temperature on rates of growth and development of a predatory planktonic water mite, Piona exigua. Growth in length of mites fed Daphnia, Ceriodaphnia and Chydorus was analysed by Gompertz or von Bertalanffy curves; these curves were compared by parallel curve analysis. Growth rates of nymphs and adult female mites increased with temperature; the duration of the imagochrysalis stage decreased. Females grown at 10 °C were smaller at final size than females grown at 15 °C, 18 °C or 22 °C. Females reared at food levels of 15 or 30 prey l⁻¹ grew more slowly and were smaller than those provided with 60 or 120 prey l⁻¹. Nymphs grew more slowly when Daphnia were the only prey, than when smaller prey were available. Food level did not affect nymph growth at 10 °C or 15 °C, but growth at 18 °C or 22 °C may have been slowed at the lowest food levels. Synergistic effects of temperature and food level on nymph growth were apparent only from analysis of growth curves and not from stage duration data.     

Feeding rate and efficiency in an apex soil predator exposed to short-term temperature changes

As extreme climate events become more frequent and intense, short-term temperature responses of ectothermic organisms can lead to decreased performance and survival. However, organisms may acclimate to these conditions through behavioural and physiological mechanisms as exposure time increases. We used a reciprocal temperature (16  °C and 24  °C) transplant experiment to determine how feeding rate and body size of an apex soil mite predator (Stratiolaelaps scimitus) (formerly Hypoaspis miles) consuming prey (Carpoglyphus lactis) (dried-fruit-mite) changed along a gradient of acclimation time (1, 3, and 7 days, with control). In the control treatments, mites reared at 24  °C fed more, but were smaller than mites reared at 16  °C. When transferred to new temperature conditions, predators that experienced cooling events had reduced feeding efficiencies driven by decreased feeding performance, despite an absence of metabolic costs, while under warming events, predators also had reduced feeding activity, but feeding increased with acclimation time. Yet predators lost more weight the longer they were exposed to warming, and continued to experience reduced feeding efficiencies (i.e., lack of weight gain after feeding); this result suggests increased metabolic costs at higher temperatures and provides a mechanism for community downsizing under warming. Overall, our results suggest that ectothermic predators can acclimate to warming events with increased exposure time, but both warming and cooling events decrease overall performance.     

Effects of temperature on growth and efficiency of food utilization in fifth-instar caterpillars of the tobacco hornworm, Manduca sexta

Fifth-instar larvae of Manduca sexta were reared from hatching on artificial diet at 15, 20, 25, 30 and 35°C. Total development time decreased with increasing temperature. Very few larvae (12%) survived at 15°C, so this temperature was not considered further. There was some mortality at 30°C (11%), and at 35°C (50%).The absolute rate of growth in the fifth instar was faster at 25 than at 20°C, but was similar at 25, 30 and 35°C. This was true both for caterpillars that were chronically exposed to experimental temperatures (i.e. since hatching) and for those acutely exposed (i.e. reared up to fifth instar at 25°C).There was a progressive decrease with higher rearing temperatures in both the initial and final sizes of chronically exposed fifth-instar larvae. Acutely exposed caterpillars matched for initial size showed smaller temperature related differences in final size. Because of these size differences there were differences in relative growth rate which did not reflect true differences in absolute growth rate.Total food consumed by chronically exposed caterpillars was greatest at the lowest temperature (20°C), and decreased progressively with increasing temperature. The absolute rate of food consumption increased from 20 to 25°C, but did not vary significantly between 25 and 35°C. Differences in the sizes of the insects at the different temperatures meant that there were differences among relative measures of consumption that did not reflect absolute food consumption.For chronically exposed caterpillars, none of the three usual indices of food conversion efficiency (AD, ECI and ECD) varied significantly with temperature between 20 and 35°C. This implies that the effects of temperature on metabolic costs are closely matched to food consumption.Oxygen consumption increased with temperature between 20 and 25°C but was temperature compensated between 25 and 35°C.These findings are discussed in terms of their implications for the optimal temperature for growth in Manduca.     

Body size development of captive and free‐ranging Leopard tortoises (Geochelone pardalis)

The growth and weight development of Leopard tortoise hatchings (Geochelone pardalis) kept at the Al Wabra Wildlife Preservation (AWWP), Qatar, was observed for more than four years, and compared to data in literature for free‐ranging animals on body weight or carapace measurements. The results document a distinctively faster growth in the captive animals. Indications for the same phenomenon in other tortoise species (Galapagos giant tortoises, G. nigra; Spur‐thighed tortoises, Testudo graeca; Desert tortoises, Gopherus agassizi) were found in the literature. The cause of the high growth rate most likely is the constant provision with highly digestible food of low fiber content. Increased growth rates are suspected to have negative consequences such as obesity, high mortality, gastrointestinal illnesses, renal diseases, “pyramiding,” fibrous osteodystrophy or metabolic bone disease. The apparently widespread occurrence of high growth rates in intensively managed tortoises underlines how easily ectothermic animals can be oversupplemented with nutrients. Zoo Biol 29:517–525, 2010. © 2009 Wiley‐Liss, Inc.     

Growth of juvenileArctica islandica under experimental conditions

In two laboratory experiments, the effects of temperature and food availability on the growth of 10- to 23-mm high specimens of the bivalveArctica islandica were estimated. Each experimental set-up consisted of 5 treatments in which either the food supply or the temperature differed. It was demonstrated thatArctica is able to grow at temperatures as low as 1°C. A tenfold increase of shell growth was observed at temperatures between 1° and 12°C. The greatest change in growth rate took place between 1° and 6°C. Average instantaneous shell growth varies between 0.0003 at 1°C to 0.0032/day at 12°C. The results suggest that temperature hardly affects the time spent in filtration, whereas particle density strongly influences that response. Starved animals at 9°C have their siphons open during only 12% of the time, whereas the siphons of optimally fed animals were open on average during 76% of the observations. Increased siphon activity corresponded to high shell and tissue growth. At 9°C, average shell growth at the optimum cell density of 20×10⁶ cell/l was 3.1 mm corresponding to an instantaneous rate of 0.0026/day. An algal cell density (Isochrysis galbana, Dunaliella marina) ranging between 5 and 7×10⁶ cell/l is just enough to keep shells alive at 9°C. Carbon conversion efficiency at 9°C is estimated to vary between 11 and 14%.     

Effects of temperature on survival, development, growth and feeding of larvae of Yellowtail clownfish Amphiprion clarkii (Pisces: Perciformes)

To understand the physiological and ecological responses of marine fishes to the change of water temperature, newly-hatched larvae of Yellowtail clownfish Amphiprion clarkii were reared in captivity at water temperatures of 23, 26 and 29 °C till they completed the metamorphosis to juvenile phase, and larval survival, development, growth and feeding were evaluated during the experimental period. The results showed that water temperature influenced the physiological performance of larvae of A. clarkii significantly. The survival and growth rates of larvae of A. clarkii increased significantly with the increase of water temperature from 23 to 29 °C (P < 0.05). Water temperature also influenced larval development of A. clarkii significantly and larvae reared at 23 °C took longer time for post-larval development and metamorphosis compared to 26 and 29 °C (P < 0.05). Total length and body weight for post-larval development and metamorphosis decreased with the increase of water temperature from 23 to 29 °C (P < 0.05). Q₁₀ in developmental rate was higher than in daily growth rate at the same rearing temperature, indicating that at water temperature had greater influence on larval development than on growth. Water temperature also influenced larval feeding of A. clarkii significantly with feed ration (FR) and feed conversion efficiency (FCE) increased with the increase of water temperature from 23 to 29 °C (P < 0.05). There was a positive correlation between FR and specific growth rate (SGR) (P < 0.05) but not between FCE and SGR (P > 0.05), indicating that FR influenced growth rate significantly in larvae of A. clarkii. This study demonstrated that the physiological responses of larvae of A. clarkii to the change of water temperature and confirmed that water temperature influenced larval survival, development, growth and feeding significantly. This study suggests that the decline of larval survival and growth rates, extension of pelagic larval duration and reduction of larval feeding at lower temperature have ecological impacts on larval dispersal and metamorphosis, juvenile settlement and population replenishment in A. clarkii in the wild.     

The influence of temperature on size as an indicator of host quality for the development of a solitary koinobiont parasitoid

The influence of aphid size on the host quality assessment and progeny performance of aphidiine parasitoids was examined using the mealy plum aphid parasitoid, Aphidius transcaspicus Telenga (Hymenoptera: Braconidae) and the black bean aphid, Aphis fabae Scopoli (Homoptera: Aphididae), as a readily acceptable alternate host. Aphid size in relation to stage of development was manipulated by rearing synchronous aphid cohorts at either 15 or 30 °C. At 15 °C, 2nd instar aphids were approximately the same size as 4th instar aphids reared at 30 °C. Cohorts of 30 aphids from each instar, reared at each temperature, were exposed to parasitism by a single parasitoid female for a period of 5 h. Overall susceptibility to parasitism did not vary between aphid cohorts, but the parasitoid response to aphid size differed significantly between rearing temperatures for both progeny sex ratio (parent female assessment of host quality) and larval growth and development (host suitability for parasitoid development). For aphids reared at 15 °C, the proportion of female progeny and emerging adult size for the parasitoid increased linearly with aphid size at the time of attack, while development time remained constant. In contrast, for aphids reared at 30 °C, the proportion of female progeny, emerging adult size, and the development time of the parasitoid all declined with aphid size at the time of attack. The contrasting responses of the parasitoid to host size for aphids reared at the two temperatures suggest that host quality is only indirectly related to aphid size among aphidiine parasitoids. The possible effects of higher temperatures on nutritional stress, obligate endosymbionts, and future growth potential of the aphids are discussed as explanations for the variation in host quality for parasitoid development.     

Embryonic duration and post-embryonic growth rates of the tropical freshwater shrimp Caridina nilotica (Decapoda:Atyidae) under laboratory and experimental field conditions

SUMMARY. Embryonic durations and post embryonic growth rates of Caridina nilotica were determined under laboratory conditions at constant temperatures near 18, 24 and 30°C. Embryonic durations and intermoult intervals were negative curvilinear functions of temperature. At a given temperature moulting frequency varied inversely with shrimp size and slight sexual differences were apparent. Moulting frequency of berried females was governed by the temperature-specific embryonic durations. Growth rates were determined from changes in carapace length (CL) of individual shrimps (laboratory) or batches of shrimps (field enclosures) over 1 month and these data were used to calculate temperature-specific life-long growth curves for males and females. Growth in body mass was estimated indirectly from the carapace length-mass relationship of C. nilotica. On average, males grew marginally faster than females during the first 2 months of life, but growth of males larger than CL= 4 mm was considerably depressed relative to that of females. Inflexions in growth rate, apparently related to the onset of sexual maturity, were apparent in both sexes. Under laboratory conditions, the growth rate of males increased with temperature, but temperature-related differences were not as marked in females. Notwithstanding the more rapid moulting rate at 30°C the growth rate of females was slightly slower at 30 than at 24°C as a result of marginally but significantly smaller per moult growth increments observed at 30°C in animals up to CL= 5.5 mm. Possible reasons for this depressed growth are discussed. Growth rates of animals in field enclosures in Lake Sibaya over 1 month in winter (20 ± 3°C) were generally comparable to those estimated for the 18°C laboratory experiments. Growth rates in enclosures containing tripled standing stocks were almost identical to those containing the naturally occurring biomass of animals, suggesting a non-limited environment at least during the time of the experiment.     

Elevated temperature restricts growth potential of the coral reef fish <Emphasis Type="Italic">Acanthochromis polyacanthus</Emphasis>

In order to test the effect of temperature variation on the growth of a common coral-reef fish, Acanthochromis polyacanthus, juveniles, sub-adults and adults were reared on either high or low food rations at temperatures corresponding to the long-term (14 year) minimum, average and maximum summer sea-surface temperatures (26, 28 and 31°C respectively) at Orpheus Island, Great Barrier Reef, Australia. Both temperature and food supply affected the growth of juvenile and adult A. polyacanthus. Individuals grew more on high food rations, but growth declined with increasing temperature. Importantly, at 31°C, the growth of juveniles and adults on the high food ration was nearly identical to growth on the low food ration. This indicates that the capacity for growth is severely limited at higher ocean temperatures that are predicted to become the average for Orpheus Island within the next 100 years as a result of rapid climate change. Communicated by Biology Editor Dr Mark McCormick     

The influence of temperature transfers on subsequent growth of the European peacock butterfly <Emphasis Type="Italic">Inachis io</Emphasis> (Lepidoptera,Nymphalidae)

The study addresses the effects of higher and lower temperatures experienced during the early stages of ontogeny on the parameters of the subsequent growth and development of the butterfly Inachis io. The caterpillars reared at a temperature of 22°С during instars I–III and then transferred to lower temperatures (16, 18, and 20°C) had higher instantaneous growth rates, larger body mass, and shorter duration of instars IV and V than the caterpillars that developed permanently at these lower temperatures. Vice versa, the caterpillars reared at 16°С during instars I–III and transferred to higher temperatures (18, 20, and 22°C) developed and grew slower than the caterpillars reared at these higher temperatures from the beginning. Possible physiological mechanisms underlying the observed phenomena and their ecological consequences are discussed. Our results are compared with the previously published data on fish—another group of ectothermic organisms, on which similar experiments have been carried out.     

Effect of water temperature,feeding frequency,and protein percent in the diet on water quality,growth and behavior of Nile tilapia Oreochromis niloticus (Linnaeus, 1758)

This study evaluated how water temperature (26, 28, and 30°C), number of meals per day (one or two meals), and protein percent in diet (20, 25 and 30%) impact growth performance, biometric indices, and feeding behavior of Nile tilapia, Oreochromis niloticus. Fish were randomly allocated into 18 equal replicate groups. Higher final body weight was observed in fish reared at 30°C and fed one meal per day containing 30% crude protein. Better weight gain, weight gain %, feed conversion ratio, specific growth rate, and condition factor were recorded in fish reared at 26°C and fed one meal per day containing 30% protein. The best length weight relationship was obtained in fish reared at 26°C and fed one meal per day containing 30% crude protein. Shorter feeding duration and duration of appetite inhibition latency were recorded in fish reared at 30°C, fed one meal per day, and given a diet containing 30% protein. The highest proactivity was recorded in fish reared at 30°C, received one meal per day, and with 25% crude protein in their diet. Conclusively, rearing Nile tilapia at 26–30°C with a lower feeding frequency (one meal/day) and a 30% crude protein diet achieved better performance and feeding behavior.     

Techniques for hand-rearing tree-shrews (Tupaia belangeri) from birth

In captivity, Tupaia belangeri (Thailand tree-shrew) frequently show aberrant patterns of maternal care which result in the death of offspring. In order to maximize the potential of the tree-shrew as an animal resource for experimental studies we have developed a program for hand-rearing tupaiidae from birth. Newborn tree-shrews were removed from mothers with a history of poor parental care to a nursery maintained under conditions of controlled relative humidity (70 ± 10%) and temperature (25 ± 1°C) on a 12 h dark: 12 h light cycle. The young tree-shrews were fed on a liquid formula until the eyes opened (Day 18–23) and for the subsequent 10 days on a transitional diet until they could feed themselves on solid food. Our hand-rearing protocol appears to conform to the natural weaning pattern of tupaiids. Food consumption during the liquid diet phase was linearly related to age and the increase in body weight in both sexes. The initial growth rate of male and female hand-reared tree-shrews was slower than that of maternally reared animals during the liquid diet phase. The growth rate accelerated subsequently and the body weight of hand-reared tree-shrews eventually reached that of maternally reared animals of the same sex. Various developmental changes occurred during the same period in artificially and naturally reared animals. In both hand-reared and maternally reared groups, the growth rate of male tree-shrews exceeded that of females from about Day 40 onward. The accelerated growth rate of male tree-shrews was in apparent association with an increase in androgen secretion at the onset of puberty. The high fecundity of tree-shrews in captivity reinforced with a program for hand-rearing the young make T belangeri a potential alternative to more conventional laboratory species in specific areas of biomedical research.     

Impacts of temperature on metabolic rates of adult Extatosoma tiaratum reared on different host plant species

Access to balanced nutrition enables optimum health and development, body repair, fat storage, increased fecundity and longevity. In the present study, we assessed the responses of a generalist leaf feeder (the phasmid Extatosoma tiaratum) reared continuously on one of three host plants, tree lucerne (Chamaecyisus palmensis), bramble (Rubus fruticosus) and Eucalyptus species, in a low fluctuating temperature environment until adulthood. Once all individuals reached adulthood, we exposed each individual to a ramping temperature event (starting at 25 °C and ramping the temperature at 0.25 °C min⁻¹) and assessed their metabolic rates () responses at specific temperature 'bins' (25, 30, 35, 40 and 42 °C). Sex but not diet influenced respiration and metabolic rate. Male individuals, on average, had a higher than females. Sex and diet were significant influences on at different temperatures. Metabolic rates at lower temperatures were not affected by sex or diet type. At 35 °C, metabolic rates were influenced by sex and diet, with males reared on bramble and tree lucerne having a higher metabolic rate than females reared on the same foodplant, whereas Eucalypt reared animals showing an opposite trend. Lifetime egg production by females was 150% higher on bramble compared with the other host plants. Incorporating fluctuating temperature ranges into experiments will further help to understand the impact that thermal stress will have on the growth, development, performance and survival of insects in a more variable climatic and nutritional landscape.     

Global warming may disproportionately affect larger adults in a predatory coral reef fish

Global warming is expected to reduce body sizes of ectothermic animals. Although the underlying mechanisms of size reductions remain poorly understood, effects appear stronger at latitudinal extremes (poles and tropics) and in aquatic rather than terrestrial systems. To shed light on this phenomenon, we examined the size dependence of critical thermal maxima (CTmax) and aerobic metabolism in a commercially important tropical reef fish, the leopard coral grouper (Plectropomus leopardus) following acclimation to current‐day (28.5 °C) vs. projected end‐of‐century (33 °C) summer temperatures for the northern Great Barrier Reef (GBR). CTmax declined from 38.3 to 37.5 °C with increasing body mass in adult fish (0.45–2.82 kg), indicating that larger individuals are more thermally sensitive than smaller conspecifics. This may be explained by a restricted capacity for large fish to increase mass‐specific maximum metabolic rate (MMR) at 33 °C compared with 28.5 °C. Indeed, temperature influenced the relationship between metabolism and body mass (0.02–2.38 kg), whereby the scaling exponent for MMR increased from 0.74 ± 0.02 at 28.5 °C to 0.79 ± 0.01 at 33 °C, and the corresponding exponents for standard metabolic rate (SMR) were 0.75 ± 0.04 and 0.80 ± 0.03. The increase in metabolic scaling exponents at higher temperatures suggests that energy budgets may be disproportionately impacted in larger fish and contribute to reduced maximum adult size. Such climate‐induced reductions in body size would have important ramifications for fisheries productivity, but are also likely to have knock‐on effects for trophodynamics and functioning of ecosystems.     

Temperature‐specific acclimation effects on adult locomotor performance of inbred and crossbred Drosophila melanogaster

Climate change poses a serious threat to the existence of many species. The combination of habitat fragmentation and increasing temperatures is of particular concern because it can alter demographic and population genetic processes, which may ultimately lead to extinction. Locomotion is very important in mitigating the negative impacts of these processes by upholding migration and contributing to random mating within and between populations. In the present study, a T‐maze, constituting a relatively complex laboratory assay, is used to investigate whether inbreeding affects the capacity to reach a food source in male Drosophila melanogaster Meigen 1830 (Diptera: Drosophilidae) reared at 20, 25 or 30 °C, respectively. The effects of inbreeding and crossbreeding are highly temperature‐specific. Strong heterosis for the ability to reach food in the maze is observed in flies developed and maintained at 30 °C, whereas inbred flies locate the food significantly faster than crossbreds when reared at 25 °C in four of six runs. No clear pattern is evident in flies reared at 20 °C. The results suggest that complex traits such as locomotor performance in a maze are highly informative in the evaluation and detection of inbreeding depression under different thermal conditions. The effect of inbreeding is most pronounced at high temperature, which is a characteristic of the conditions that many natural populations may have to face under climate change.     

Cooler temperatures increase sensitivity to ultraviolet B radiation in embryos and larvae of the frog Limnodynastes peronii

Recent studies suggest that complex interacting processes are driving global amphibian declines. Increased ultraviolet B (UVB) radiation in the solar spectrum associated with ozone depletion has been implicated in declines, and evidence suggests that the effects of UVB radiation on amphibians may be greater at cooler temperatures. We tested the thermal sensitivity of UVB effects on amphibians in a controlled factorial experiment using the striped marsh frog, Limnodynastes peronii as a model species. We compared survival, growth and locomotor performance of embryonic and larval L. peronii reared under low and high UVB exposures at both 20 and 30 °C. Embryonic and larval L. peronii proved extremely sensitive to UVB damage and exhibited greater sensitivity at 20 °C compared with 30 °C. Embryonic survival to Gosner stage 25 was unaffected by UVB exposure at 30 °C, but at 20 °C survival was reduced to 52% under high UVB. Larval survival exhibited a similar trend. At 20 °C, all tadpoles survived under low UVB, whereas under high UVB there was 100% mortality after 15 days of exposure. At 30 °C, 86% survived under low UVB, but only 46% survived under high UVB. Sublethal effects such as, embryonic malformation, retarded larval growth and reduced larval swimming performance were also greater at 20 °C compared with 30 °C. Our results strongly indicate that UVB damage in amphibians is markedly increased at cooler temperatures. Thus, populations of UVB sensitive species occurring at cold climates may be at greater risk of declines due to increased solar UVB radiation.