Effects of acute temperature or salinity stress on the immune response in sea cucumber, Apostichopus japonicus

Invertebrates are increasingly raised in mariculture, where it is important to monitor immune function and to minimize stresses that could suppress immunity. The activities of phagocytosis, superoxide dismutase (SOD), catalase (CAT), myeloperoxidase (MPO), and lysozyme (LSZ) were measured to evaluate the immune capacities of the sea cucumber, Apostichopus japonicus, to acute temperature changes (from 12 °C to 0 °C, 8 °C, 16 °C, 24 °C, and 32 °C for 72 h) and salinity changes (from 30‰ to 20‰, 25‰, and 35‰ for 72 h) in the laboratory. Phagocytosis was significantly affected by temperature increases in 3 h, and by salinity (25‰ and 35‰) changes in 1 h. SOD activities decreased significantly in 0.5 h to 6 h samples at 24 °C. At 32 °C, SOD activities decreased significantly in 0.5 h and 1 h exposures, and obviously increased for 12 h exposure. CAT activities decreased significantly at 24 °C for 0.5 h exposure, and increased significantly at 32 °C in 3 h to 12 h exposures. Activities of MPO increased significantly at 0 °C in 0.5 h to 6 h exposures and at 8 °C for 1 h. By contrast, activities of MPO decreased significantly in 24 °C and 32 °C treatments. In elevated-temperature treatments, activities of LSZ increased significantly except at 32 °C for 6 h to 12 h exposures. SOD activity was significantly affected by salinity change. CAT activity decreased significantly after only 1 h exposure to salinity of 20‰. Activities of MPO and LSZ showed that A. japonicus tolerates limited salinity stress. High-temperature stress had a much greater effect on the immune capacities of A. japonicus than did low-temperature and salinity stresses.     

Hibernation and daily torpor in an armadillo, the pichi (Zaedyus pichiy)

Hibernation and daily torpor are physiological strategies to cope with energetic challenges that occur in many mammalian and avian taxa, but no reliable information exists about daily torpor or hibernation for any xenarthran. Our objective was to determine whether the pichi (Zaedyus pichiy), a small armadillo (Xenarthra, Dasypodidae) that inhabits arid and semi-arid habitats in central and southern Argentina and Chile, enters shallow daily torpor or prolonged deep hibernation during winter when environmental temperature and food availability are low. We studied body temperature changes during winter in semi-captive pichis by means of temperature dataloggers implanted subcutaneously. All individuals entered hibernation, characterized by torpor events of 75 ± 20 h during which the subcutaneous temperature (T_sc) decreased to 14.6 ± 2.1 °C. These events were interrupted by periods of euthermia of 44 ± 38 h with a T_sc of 29.1 ± 0.7 °C. After the hibernation season, daily torpor bouts of 4 to 6 h occurred irregularly, with T_sc dropping to as low as 24.5 °C. We conclude that the pichi is a true hibernator and can enter daily torpor outside of the hibernation season.     

Simultaneous exposure of Xenopus A6 kidney epithelial cells to concurrent mild sodium arsenite and heat stress results in enhanced hsp30 and hsp70 gene expression and the acquisition of thermotolerance

In this study, we examined the effect of concurrent low concentrations of sodium arsenite and mild heat shock temperatures on hsp30 and hsp70 gene expression in Xenopus A6 kidney epithelial cells. RNA blot hybridization and immunoblot analysis revealed that exposure of A6 cells to 1–10 µM sodium arsenite at a mild heat shock temperature of 30 °C enhanced hsp30 and hsp70 gene expression to a much greater extent than found with either stress individually. In cells treated simultaneously with 10 µM sodium arsenite and different heat shock temperatures, enhanced accumulation of HSP30 and HSP70 protein was first detected at 26 °C with larger responses at 28 and 30 °C. HSF1 activity was involved in combined stress-induced hsp gene expression since the HSF1 activation inhibitor, KNK437, inhibited HSP30 and HSP70 accumulation. Immunocytochemical analysis revealed that HSP30 was present in a granular pattern primarily in the cytoplasm in cells treated simultaneously with both stresses. Finally, prior exposure of A6 cells to concurrent sodium arsenite (10 µM) and heat shock (30 °C) treatment conferred thermotolerance since it protected them against a subsequent thermal challenge (37 °C). Acquired thermotolerance was not observed with cells treated with the two mild stresses individually.     

Discrimination of viable and dead Vibrio vulnificus after refrigerated and frozen storage using EMA, sodium deoxycholate and real-time PCR

The effect of refrigerated and frozen storage on the viability of Vibrio vulnificus was evaluated using cell suspensions (1 × 10⁸ CFU/ml). Ethidium bromide monoazide (EMA) was utilized to selectively allow real-time (Rti) PCR amplification of target DNA from viable but not dead cells. Bacterial survivors from the EMA Rti-PCR were evaluated by comparison with the plate count assay following different temperature exposures (− 20 and 4 °C) every 24 h for 72 h. The log CFU values from the EMA Rti-PCR assays were erroneously higher than that from plate counts. DNA amplification was not completely suppressed by EMA treatment of low temperature destroyed cells suggesting that membrane damage was not sufficient to allow effective EMA penetration into the cells. The optimal concentration of sodium deoxycholate (SD) was also determined to enhance discrimination of viable and dead cells following exposure of cells to low temperatures. The use of 0.01% or less of SD did not inhibit the Rti-PCR amplification derived from viable bacterial cells. A rapid decrease of the log CFU was observed with cell suspensions subjected to frozen storage and a slow decline in the log CFU occurred at 4 °C. The combination of SD and EMA treatments applied to cells of V. vulnificus held at − 20 °C and 4 °C resulted in a high level of correlation between the log of CFU (plate counts) and the log of the number of viable cells determined from SD+EMA Rti-PCR.     

Formamide denaturation of chromosomal DNA for in situ hybridization and C-band preparation in the guinea pig, Cavia porcellus

Cytological preparations were incubated in 0.07 N NaOH at room temperature or 90% formamide (final salt concentration 2 × SSC) at either 65 °C or 37 °C for 2.5 h to denature guinea pig chromosomes. Chromosomes treated with NaOH or formamide at 65 °C showed a large amount of DNA loss, while chromosomes treated with formamide at 37 °C showed little or no DNA loss. Repeated sequences were isolated from guinea pig DNA and [³H]cRNA was transcribed with Escherichia coli RNA polymerase for in situ hybridization. Localization of the [³H]cRNA occurred in the centromeric regions and C-band positive short arms of almost all of the chromosomes in the NaOH preparations. Chromosomes treated with formamide at 65 °C showed the same grain distribution with a decrease in the number of grains/cluster. Slides incubated in formamide at 37 °C showed localization in only a few chromosomes and the number of grains/cluster was greatly diminished. Thermal denaturation of isolated chromatin indicated that incubation of chromosomes in formamide at 37 °C did not fully denature the DNA. C-bands could be induced by treating slides in formamide at either 65 °C or 37 °C when followed by a “reassociation” in 2 × SSC at 65 °C for 16 h. If the “reassociation” step was omitted, C-bands were found in the 65 °C formamide slides but not the 37 °C formamide slides.     

Febrile response to infection in the American alligator (Alligator mississippiensis)

Temperature probes were inserted into the stomachs of juvenile American alligators (Alligator mississippiensis) maintained outdoors at ambient fluctuating temperatures. Internal body temperatures (T_b) were measured every 15 min for two days, and then the alligators were injected with bacterial lipopolysaccharide (LPS), pyrogen-free saline, or left untreated. Alligators injected intraperitoneally with LPS exhibited maximum T_bs 2.6 ± 1.1 °C and 3.5 ± 1.2 °C higher than untreated control animals on days one and two after treatment, respectively. T_bs for these animals fell to within control ranges by day three postinjection. Similarly, mean preferred body temperatures (MPBTs) were significantly higher for LPS-injected alligators on days one (4.2 ± 1.8 °C) and two (3.5 ± 1.6 °C) after treatment. Intraperitoneal injection of heat-killed Aeromonas hydrophila, a gram-negative bacterium known to infect crocodilians, resulted in a fever while injection of Staphylococcus aureus (gram positive) did not elicit a febrile response. Injection of LPS in alligators maintained indoors in a constant temperature environment resulted in no increase in internal T_b. These results indicate that alligators did not exhibit a febrile response in the absence of a thermal gradient, and suggest that febrile responses observed are probably behavioral in nature.     

Characterization of the heat shock protein 90 gene in the plant parasitic nematode Meloidogyne artiellia and its expression as related to different developmental stages and temperature

The full-length cDNA and the corresponding gene of the heat shock protein 90, Mt-Hsp90, were isolated and characterized in the plant parasitic nematode Meloidogyne artiellia. The full-length Mt-Hsp90 cDNA contained a 5′ untranslated region (UTR) of 45 bp with the 22 bp trans-spliced leader SL1, an ORF of 2172 bp encoding a polypeptide of 723 amino acids and a 3′ UTR of 191 bp. The deduced amino acid sequence of Mt-hsp90 showed high similarity with other known Hsp90s. Five conserved amino acid signatures indicated that Mt-hsp90 is a cytosolic member of the Hsp90 family. The gene consists of 10 exons and 9 introns, a more expanded gene structure compared to the corresponding Caenorhabditis elegans gene, daf-21. Mt-hsp90 gene was constitutively expressed at high levels in all developmental stages of M. artiellia. Egg masses and second stage juveniles (J2s) were exposed at 5° and 30 °C for different periods of times in order to explore the impact of adverse temperature on Mt-hsp90 gene expression. Expression levels of Mt-hsp90 were examined by fluorescent real-time PCR. At 30 °C a burst of expression for Mt-hsp90 was observed in J2s after 2 h of heat shock treatment, then expression dropped with longer exposing times, although remaining still relatively high after 24 h. This temperature did not affect Mt-hsp90 gene expression in the egg masses. However, egg masses exposed at 5 °C showed a little but gradual increase in the mRNA level with time. By contrast, no significant changes in the Mt-hsp90 level were observed in J2s exposed to cold. These data show that egg masses and J2s exposed to cold and heat stresses have different expression profiles suggesting that Mt-Hsp90 may provide a link between environmental conditions and the life cycle of the nematode.     

Seasonal variation in thermal energetics of the Australian owlet-nightjar (Aegotheles cristatus)

Many birds living in regions with seasonal fluctuations in ambient temperatures (T_a) typically respond to cold by increasing insulation and adjusting metabolic rate. Seasonal variation in thermal physiology has not been studied for the Caprimulgiformes, an order of birds that generally have basal metabolic rates (BMR) lower than predicted for their body mass. We measured the metabolic rate and thermal conductance of Australian owlet-nightjars (Aegotheles cristatus) during summer and winter using open-flow respirometry. Within the thermoneutral zone (TNZ; 31.3 to 34.8 °C), there was no seasonal difference in BMR or thermal conductance (C), but body temperature was higher in summer- (38.2 ± 0.3 °C) than winter-acclimatized (37.1 ± 0.5 °C) birds. Below the TNZ, resting metabolic rate (RMR) increased linearly with decreasing T_a, and RMR and C were higher for summer- than winter-acclimatized birds. The mean mass-specific BMR of owlet-nightjars (1.27 mL O₂ g^− 1 h^− 1) was close to the allometrically predicted value for a 45 g Caprimulgiformes, but well below that predicted for birds overall. These results suggest that owlet-nightjars increase plumage insulation to cope with low winter T_a, which is reflected in the seasonal difference in RMR and C below the TNZ, rather than adjusting BMR.     

Human telomeric G-quadruplex formed from duplex under near physiological conditions: Spectroscopic evidence and kinetics

The structural interconversion between the G-quadruplex and duplex in vivo is an important subject. In the present study, we used human telomeric DNA duplex composed of GGG(TTAGGG)₃/CCC(TAACCC)₃ as a model system to investigate its properties under near physiological conditions by spectroscopic methods. Circular dichroism and fluorescence spectra demonstrated that G-quadruplex structure can be formed from duplex at near physiological pH (pH 7.4), salt concentration (150 mM K⁺), and temperature (37 °C) in the presence of molecular crowding agent PEG (400 g/l), whereas the G-quadruplex structure cannot be formed at 25 °C in buffer containing 150 mM K⁺ in the presence of PEG. It is found that the formation rate of G-quadruplex structure depends on the temperature and the concentrations of both PEG and K⁺. This work suggests that human telomeric G-quadruplex structure may be potentially formed from Watson–Crick duplex in vivo.     

Trypsin from the pyloric caeca of bluefish (Pomatomus saltatrix)

Trypsin was purified from the pyloric caeca of bluefish (Pomatomus saltatrix) by ammonium sulfate precipitation, acetone precipitation and soybean trypsin inhibitor-Sepharose 4B affinity chromatography. Bluefish trypsin migrated as a single band using both sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and native-PAGE and had a molecular mass of 28 kDa. The optima pH and temperature for the hydrolysis of benzoyl-dl-arginine-p-nitroanilide (BAPNA) were 9.5 and 55 °C, respectively. The enzyme was stable over a broad pH range (7 to 12), but was unstable at acidic pH, and at temperatures greater than 40 °C. The enzyme was inhibited by specific trypsin inhibitors: soybean trypsin inhibitor (SBTI), N-p-tosyl-l-lysine chloromethyl ketone (TLCK) and the serine protease inhibitor phenylmethyl sulfonylfluoride (PMSF). CaCl₂ partially protected trypsin against activity loss at 40 °C, but NaCl (0 to 30%) decreased the activity in a concentration dependent manner. The N-terminal amino acid sequence of trypsin was determined as IVGGYECKPKSAPVQVSLNL and was highly homologous to other known vertebrate trypsins.     

Clean conversion of cellulose into fermentable glucose

We studied the process of conversion of microcrystalline-cellulose into fermentable glucose in the formic acid reaction system using cross polarization/magic angle spinning ¹³C-nuclear magnetic resonance, X-ray diffraction and Fourier transform infrared spectroscopy. The results indicated that formic acid as an active agent was able to effectively penetrate into the interior space of the cellulose molecules, thus collapsing the rigid crystalline structure and allowing hydrolysis to occur easily in the amorphous zone as well as in the crystalline zone. The microcrystalline-cellulose was hydrolyzed using formic acid and 4% hydrochloric acid under mild conditions. The effects of hydrochloric acid concentration, the ratio of solid to liquid, temperature (55–75 °C) and retention time (0–9 h), and the concentration of glucose were analyzed. The hydrolysis velocities of microcrystalline-cellulose were 6.14 × 10^− 3 h^− 1 at 55 °C, 2.94 × 10^− 2 h^− 1 at 65 °C, and 6.84 × 10^− 2 h^− 1 at 75 °C. The degradation velocities of glucose were 0.01 h^− 1 at 55 °C, 0.14 h^− 1 at 65 °C, 0.34 h^− 1 at 75 °C. The activation energy of microcrystalline-cellulose hydrolysis was 105.61 kJ/mol, and the activation energy of glucose degradation was 131.37 kJ/mol.     

Biosorption of acid violet dye from aqueous solutions using native biomass of a new isolate of Penicillium sp.

Laboratory investigation of the potential use of Penicillium sp. as biosorbent for the removal of acid violet dye from aqueous solution was studied with respect to pH, temperature, biosorbent, initial dye concentrations. Penicillium sp. decolourizes acid violet (30 mg l⁻¹) within 12 h agitation of 150 rpm at pH 5.7 and temperature of 35 °C. The pellets exhibited a high dye adsorption capacity (5.88 mg g⁻¹) for acid violet dye over a pH range (4–9); the maximum adsorption was obtained at pH 5.7. The increase of temperature favored biosorption for acid violet, but the optimum temperature was 35 °C. Adsorption kinetic data were tested using pseudo-first-order, pseudo-second-order and kinetic studies showed that the biosorption process follows pseudo-first-order rate kinetics with an average rate constant of 0.312 min⁻¹. Isotherm experiments were conducted to determine the sorbent–desorption behavior of examined dye from aqueous solutions using Langmuir and Freundlich equations. Langmuir parameter indicated a maximum adsorption capacity of 4.32 mg g⁻¹ for acid violet and R_L value of 0.377. Linear plot of log q_e vs log C_e shows that applicability of Freundlich adsorption isotherm model. These results suggest that this fungus can be used in biotreatment process as biosorbent for acid dyes.     

Growth and protein synthesis of barramundi, Lates calcarifer, fed lupin as a partial protein replacement

Protein synthesis is an essential growth process in all animals. Little information is available on post-prandial protein synthesis and even less where different protein sources are compared. Protein synthesis was measured at 4 and 24 h after feeding juvenile barramundi in order to determine the effect of using lupin as a partial protein replacement for fish meal on the post-prandial protein metabolism. Juvenile barramundi (4.3 ±0.6 g) were held in a recirculation system (27 °C, salinity 10‰ and 24 h light) for 15 days. Fish were fed one of two isonitrogenous isoenergetic diets (40% crude protein, 16% lipid and 18.5 GE MJ kg^− 1). One diet was formulated with 100% fish meal as the protein source while the other had 45% of the protein replaced with lupin ingredients (lupin kernel meal (Lupinus angustifolius) and lupin protein concentrate). All fish were fed a ration of 6%·d^− 1 and feed intake was not significantly different between the two diets. Specific growth rate (SGR) and growth efficiency (in relation to protein (PPV) and energy (PEV)) were 6.5 ± 0.14%·d^− 1, 43.8 ± 2.72% and 38.31 ± 1.56%, respectively, and were not significantly different between the two diets. There was no significant difference in protein synthesis between the two diets at 4 and 24 h after feeding, however protein synthesis was significantly higher 4 h after feeding than at 24 h (p = 0.02). Neither growth performance nor protein metabolism was altered by replacing 45% of the protein with lupin protein and indicated this to be a suitable protein source for barramundi feeds.     

Photoperiod and water temperature regulation of seasonal reproduction in male round stingrays (Urobatis halleri)

This study characterizes the seasonal reproductive cycle of male round stingrays (Urobatis halleri) in Seal Beach, California. Mature round stingrays were collected monthly by beach seine near the San Gabriel River outfall from August 2004–September 2006, and rays were assessed for gametogenesis and steroid hormone levels. Male round stingrays exhibit a seasonal pattern of increased gonadosomatic index (GSI), spermatogenesis, and production of testosterone (T) and 11-ketotestosterone (11-KT). Based on GSI, the male reproductive cycle was broken into three distinct phases. TUNEL positive staining was only observed in the Sertoli cells of mature spermatocysts during the degenerative testicular phase, suggesting that Sertoli cell death potentially plays a role in testicular degeneration and the regulation of sperm release. GSI, T, and 11-KT were all inversely correlated with daylength, while only T was inversely correlated with temperature. Captive male round stingrays subjected to water temperatures of 25 °C showed a significant decrease in plasma testosterone concentrations, but the same males exposed to ambient water temperatures (18 °–20 °C) exhibited T concentrations observed in wild male round stingrays during the recrudescent phase. Together, these findings suggest that temperature plays an important role in the regulation of testosterone, and may serve as an ultimate cue for reproduction in male round stingrays.     

Thin layer chromatographic analysis of glucose and maltose in estivated Biomphalaria glabrata snails and those infected with Schistosoma mansoni

Thin layer chromatography was used to analyze the glucose and maltose concentrations of the digestive gland–gonad complex (DGG) of uninfected-estivated Biomphalaria glabrata snails and estivated B. glabrata patently infected with Schistosoma mansoni. All snails were estivated in a most chamber at a relative humidity of 98 ± 1% and a temperature of 23 ± 1 °C for 14 days. Carbohydrates were extracted from the DGG with 70% aqueous ethanol, and extracts were analyzed on silica gel preadsorbent plates using ethyl acetate–glacial acetic acid–methanol–water (60:15:15:10) mobile phase, α-naphthol–sulfuric acid detection reagent, and quantification by densitometry. The concentrations of glucose and maltose were significantly reduced in both uninfected-estivated snails and infected-estivated snails.     

Isolation and partial characterization of three isoamylases of Rhyzopertha dominica F. (Coleoptera: Bostrichidae)

Three isoamylases of Rhyzopertha dominica (termed RdA70, RdA79, and RdA90 according to their relative mobility in gel electrophoresis) were isolated by ammonium sulfate fractionation and hydrophobic interaction chromatography. RdA70 and RdA79 showed an optimal pH of 7.0, whereas for RdA90 the optimal pH was 6.5. The three isoamylases remained stable at 50 °C for 1 h, but at 60 °C, all lost 50% of their activity in 20 min and were completely inactivated in 1 h. RdA70 and RdA79 were inhibited by albumin extracts from wheat samples varying widely in amylase inhibitory activity; however, RdA90 was highly resistant to inhibition. β-Mercaptoethanol up to 30 mM increased the activity of the three isoamylases by 2.5-fold. The action pattern of the three isoamylases was typical of endoamylases; however, differences were observed on the hydrolytic efficiency rates measured as V_max/K_m ratio on starch, amylopectin, and amylose. The hydrolyzing action of RdA90 on starch and amylopectin (V_max/K_m = 90.4 ± 2.3 and 78.9 ± 6.6, respectively) was less efficient than that on amylose (V_max/K_m = 214 ± 23.2). RdA79 efficiently hydrolyzed both amylopectin and amylose (V_max/K_m = 260.6 ± 12.9 and 326.5 ± 9.4, respectively). RdA70 hydrolyzed starch and amylose at similar rates (V_max/K_m = 202.9 ± 5.5 and 215.9 ± 6.2, respectively), but amylopectin was a poor substrate (V_max/K_m = 124.2 ± 7.4). The overall results suggest that RdA70 and RdA79 appear to belong to a group of saccharifying isoamylases that breaks down long fragments of oligosaccharide chains produced by the hydrolytic action of RdA90. The simultaneous action of the three isoamylases on starch, aside from the high resistance of RdA90 to wheat amylase inhibitors, might allow R. dominica to feed and reproduce successfully on the wheat kernel.     

Thermal sensitivity of uncoupling protein expression in polar and temperate fish

Uncoupling proteins (UCP), capable of increasing proton leakage across the inner mitochondrial membrane, may play a role in the temperature-dependent setting of energy turnover in animals (and their mitochondria). Therefore, the genes and expression of fish UCP were investigated in the Antarctic eelpout Pachycara brachycephalum and a temperate confamilial species, the common eelpout Zoarces viviparus. UCP full-length cDNA was amplified from liver and muscle using RT–PCR and rapid amplification of cDNA ends (RACE). The fish UCP mRNA consists of 1906 bp in P. brachycephalum and of 1876 bp in Z. viviparus. Both zoarcid sequences contain open reading frames of 939 bp, encoding 313 amino acids, with 98% and 99% identity, respectively. Protein sequences of zoarcid UCP are closest related to fish and mammalian UCP2. For analysis of temperature-dependent expression common eelpouts were cold-acclimated from 10 °C to 2 °C and Antarctic eelpouts were warm-acclimated from 0 °C to 5 °C. Identical cDNA probes for both species were developed to investigate fish UCP mRNA expression, and protein expression levels were detected by Western Blot in the enriched membrane fraction. During cold-acclimation in Z. viviparus, mRNA levels increased by a factor up to 2.0, protein levels increased up to 1.5, in line with mitochondrial proliferation during cold-acclimation. Despite decreased mitochondrial protein content, in Antarctic eelpout UCP levels rose upon warm acclimation by a factor up to 2.0 (mRNA) and 1.6 (protein), respectively. Besides the ongoing discussion of UCP function in vertebrates, the data are indicative of a significant role of fish UCP in thermal adaptation of fish mitochondria.     

Eemian and Early Weichselian vegetation and climate history in Central Europe: A case study from the Klinge section (Lusatia, eastern Germany)

The paper presents vegetation and climate reconstructions for Eemian and Early Weichselian in Central Europe based on detailed pollen data of the Klinge section. The sediments exposed in this profile were accumulated from the Saalian termination up to the Early Weichselian glaciation. A succession of forest communities, typical for the Eemian interglacial has been recorded. Pollen data indicate some oscillations during the very end of the Eemian (biozone E7). The climatic reconstructions show the heat supply rising gradually from the beginning of the interglacial to its middle part. A long-term cooling trend in January temperature was reconstructed for the second half of the interglacial. The difference between the optimum (zone E4b) and Pinus-Picea-Abies zone (E6) amounts to 4 °C, during the Pinus zone (E7) the temperature further decreased by 8 °C. The changes in July temperature were not so dramatic (about 3 °C).     

Elevated spring temperature stimulates growth, but not smolt development, in anadromous Arctic charr

Parr–smolt transformation and growth were studied in captive offspring of anadromous Arctic charr (Salvelinus alpinus) from the Hals watercourse in northern Norway (70°N), held either at a natural temperature (< 1 °C until May) or at a temperature elevated to 6 °C in late March. In mid-May, 5 weeks after the increase in photoperiod from 8:16 h light:dark to continuous light, gill Na⁺, K⁺-ATPase activity started to increase in both temperature groups, concurrent with the final development of full seawater tolerance. Temperature had no effect on the development of gill Na⁺, K⁺-ATPase activity, or on hypoosmoregulatory ability. The fish in both treatments resumed growth in mid-May, but from then on growth was faster in the elevated than in the ambient temperature group. In the former group, fish mass doubled in 6 weeks (from 65 to 137 g), and growth ceased at the time when the fish were about to complete their parr–smolt transformation. These findings show that an early vernal temperature increase advances the seasonal growth cycle, but not the parr–smolt transformation, in anadromous Arctic charr.