Cold stenothermal cave-dwelling beetles do have an HSP70 heat shock response

The response to high temperatures in adults of two cold stenothermal cave-dwelling leptodirins, Neobathyscia mancinii and Neobathyscia pasai (Coleoptera, Cholevidae) was evaluated by determinating levels of gene expression of two members of the family of heat shock proteins 70 kDa by qPCR. In both species, hsc70 mRNA level was constant with increasing temperature, whereas a significant increase in the inducible member (hsp70) mRNA was observed, higher in N. pasai. This difference could be due to their in-cave distribution: N. pasai colonizes the cave entrance where the temperature is more variable than the internal part where N. mancinii is confined. These results demonstrated for the first time the occurrence of a heat shock response in troglobite insects and suggest the correlation between the intensity of this response and the adaptation to the cave environment.     

Effects of acclimation and diapause on the thermal tolerance of the two-spotted spider mite Tetranychus urticae

The two-spotted spider mite, Tetranychus urticae, is a worldwide pest species that overwinters as diapausing females. Cold hardening is presumed to start during diapause development to ensure the successful overwintering of this species. To address this hypothesis, we compared cold tolerance between non-diapausing and diapausing females. We measured supercooling point (SCP) and survival to acute cold stress by exposing the mites at a range of sub-zero temperatures (from −4 to −28 °C for 2 h). The mean SCPs of non-diapausing and diapausing females were −19.6±0.5 and −24.7±0.3 °C respectively, and freezing killed the mites. Diapausing females were significantly more cold tolerant than non-diapausing ones, with LT₅₀ of −19.7 and −13.3 °C, respectively. Further, we also examined the effects of cold acclimation (10 d at 0 or 5 °C) in non-diapausing and diapausing females. Our findings indicated that diapause decreased SCP significantly, while cold acclimation had no effect on the SCP except for non-diapausing females that were acclimated at 5 °C. Acclimation at 5 °C enhanced survival to acute cold stress in diapausing and non-diapausing females, with LT₅₀ of −22.0 and −17.1 °C, respectively. Altogether, our results indicate that T. urticae is a chill tolerant species, and that diapause and cold acclimation elevate cold hardiness in this species.     

A comparison of low temperature tolerance traits between closely related aphids from the tropics, temperate zone, and Arctic

The survival of aphids exposed to low temperatures is strongly influenced by their ability to move within and between plants and to survive exposure to potentially lethal low temperatures. Little is known about the physiological and behavioural limitations on aphid movement at low temperatures or how they may relate to lethal temperature thresholds. These questions are addressed here through an analysis of the thermal ecology of three closely related aphid species: Myzus persicae, a ubiquitous temperate zone pest, Myzus polaris, an arctic species, and Myzus ornatus, a sub-tropical species. Lower lethal temperatures (LLT₅₀) of aphids reared at 15 °C were similar for M. persicae and M. polaris (range: −12.7 to −13.9 °C), but significantly higher for M. ornatus (−6.6 °C). The temperature thresholds for activity and chill coma increased with rearing temperature (10, 15, 20, and 25 °C) for all clones. For M. polaris and M. ornatus the slopes of these relationships were approximately parallel; by contrast, for M. persicae the difference in slopes meant that the difference between the temperatures at which aphids cease walking and enter coma increased by approximately 0.5 °C per 1 °C increase in rearing temperature. The data suggest that all three species have the potential to increase population sizes and expand their ranges if low temperature limitation is relaxed.     

Cold tolerance and freeze-induced glucose accumulation in three terrestrial slugs

Cold tolerance and metabolic responses to freezing of three slug species common in Scandinavia (Arion ater, Arion rufus and Arion lusitanicus) are reported. Autumn collected slugs were cold acclimated in the laboratory and subjected to freezing conditions simulating likely winter temperatures in their habitat. Slugs spontaneously froze at about − 4 °C when cooled under dry conditions, but freezing of body fluids was readily induced at − 1 °C when in contact with external ice crystals. All three species survived freezing for 2 days at − 1 °C, and some A. rufus and A. lusitanicus also survived freezing at − 2 °C. ¹H NMR spectroscopy revealed that freezing of body fluids resulted in accumulation of lactate, succinate and glucose. Accumulation of lactate and succinate indicates that ATP production occurred via fermentative pathways, which is likely a result of oxygen depletion in frozen tissues. Glucose increased from about 6 to 22 μg/mg dry tissue upon freezing in A. rufus, but less so in A. ater and A. lusitanicus. Glucose may thus act as a cryoprotectant in these slugs, although the concentrations are not as high as reported for other freeze tolerant invertebrates.     

Heat tolerance, behavioural temperature selection and temperature-dependent respiration in larval Octopus huttoni

This study reports temperature effects on paralarvae from a benthic octopus species, Octopus huttoni, found throughout New Zealand and temperate Australia. We quantified the thermal tolerance, thermal preference and temperature-dependent respiration rates in 1-5 days old paralarvae. Thermal stress (1 °C increase h⁻¹) and thermal selection (∼10-24 °C vertical gradient) experiments were conducted with paralarvae reared for 4 days at 16 °C. In addition, measurement of oxygen consumption at 10, 15, 20 and 25 °C was made for paralarvae aged 1, 4 and 5 days using microrespirometry. Onset of spasms, rigour (CT_max) and mortality (upper lethal limit) occurred for 50% of experimental animals at, respectively, 26.0±0.2 °C, 27.8±0.2 °C and 31.4±0.1 °C. The upper, 23.1±0.2 °C, and lower, 15.0±1.7 °C, temperatures actively avoided by paralarvae correspond with the temperature range over which normal behaviours were observed in the thermal stress experiments. Over the temperature range of 10 °C-25 °C, respiration rates, standardized for an individual larva, increased with age, from 54.0 to 165.2 nmol larvae⁻¹ h⁻¹ in one-day old larvae to 40.1-99.4 nmol h⁻¹ at five days. Older larvae showed a lesser response to increased temperature: the effect of increasing temperature from 20 to 25 °C (Q₁₀) on 5 days old larvae (Q₁₀=1.35) was lower when compared with the 1 day old larvae (Q₁₀=1.68). The lower Q₁₀ in older larvae may reflect age-related changes in metabolic processes or a greater scope of older larvae to respond to thermal stress such as by reducing activity. Collectively, our data indicate that temperatures >25 °C may be a critical temperature. Further studies on the population-level variation in thermal tolerance in this species are warranted to predict how continued increases in ocean temperature will limit O. huttoni at early larval stages across the range of this species.     

Pre-freeze mortality in three species of aphids from sub-Antarctic Marion Island

Understanding the mechanisms by which aphids survive low temperature is fundamental in forecasting the risk of pest outbreaks. Aphids are chill susceptible and die at a temperature close to that at which a small exothermal event is produced. This event, which can be identified using differential scanning calorimetry (DSC), normally occurs at a higher temperature than the supercooling point (SCP) and has been termed a pre-freeze event (PFE). However, it is not known what causes the PFE or whether it signifies the death of the aphid. These questions are addressed here by using a sensitive DSC to quantify the PFE and SCP and to relate these thermal events to the lower lethal temperature (LT₅₀) of sub-Antarctic aphids acclimated to low temperatures. PFEs were observed in each of the 3 species of aphids examined. They occurred over a narrower temperature range and at a higher temperature range than the SCP (−8.2 to −13.8 and −5.6 to −29.8 °C, respectively). Increased acclimation temperature resulted in increased SCPs in Myzus ascalonicus but not in Rhopalosiphum padi. The LT₅₀ reduced by approximately 1 °C from −9.3 to −10.5 °C with reduced acclimation temperature (10–0 °C). The LT₅₀ was close to the temperature at which the PFE occurred but statistically significantly higher than either the PFE or the SCP. In the majority of cases the PFE exotherm occurred well before the main exotherm produced by the bulk of the insect’s body water freezing (SCP). However, in a few cases it occurred at the same temperature or before the super-cooling point making the term, pre-freeze event (PFE), rather misleading. The possible origins of the PFE are discussed.     

Poikilothermic traits in Mashona mole-rat (Fukomys darlingi). Reality or myth?

The African mole-rats (Bathyergidae, Rodentia) is a mammalian family well known for a variety of ecophysiological adaptations for strictly belowground life. The smallest bathyergid, the hairless naked mole-rat from arid areas in Eastern Africa, is even famous as the only truly poikilothermic mammal. Another bathyergid, the Mashona mole-rat (Fukomys darlingi) from Zimbabwe, is supposed to have strong poikilothermic traits, because it is not able to maintain a stable body temperature at ambient temperatures below 20 °C. This is surprising because, compared to the naked mole-rat, this species, together with all congenerics, is larger, haired, and living in more seasonal environment. In addition, other Fukomys mole-rats show typical mammalian pattern in resting metabolic rates. In our study, we measured resting metabolic rate and body temperature of Mashona mole-rats from Malawi across a gradient of ambient temperatures to test its poikilothermic traits. We found that the adult mass specific resting metabolic rate was 0.76±0.20 ml O₂ g⁻¹ h⁻¹ and body temperature 34.8±1.1 °C in the thermoneutral zone (27–34 °C). Body temperature was stable (33.0±0.5 °C) at ambient temperatures from 10 to 25 °C. We thus cannot confirm poikilothermic traits in this species, at least for its Malawian population. Factors potentially explaining the observed discrepancy in Mashona mole-rat energetics are discussed.     

Duration tenacity: A method for assessing acclimatory capacity of the Antarctic limpet, Nacella concinna

The limpet, Nacella concinna, collected from the Antarctic Peninsula (67°S), was incubated at − 0.3 °C and 2.9 °C for 9 months to test if the previously reported absence of acclimation capacity in Antarctic marine ectotherms could be due to the extended time it takes for them to adjust their physiology to a new stable state. Acclimation was tested through acute measurements of upper lethal limit and a modified measure of tenacity, that tested muscle capacity by measuring the length of time that N. concinna were able to remain attached to the substratum at different temperatures. Both measures acclimated in response to incubation to the higher temperature. Lethal limits were elevated in N. concinna incubated at 2.9 °C (8.1 ± 0.3 °C) compared to those incubated at − 0.3 °C (6.9 ± 0.4 °C). 2.9 °C incubated N. concinna also had a maximum tenacity at 2.1 °C, a higher temperature than the maximum tenacity of those incubated at − 0.3 °C, which occurred at − 1.0 °C. This study is the first to show that the Antarctic limpet can acclimate its physiology, but that it requires a greater period of time for acclimation to occur than previous studies have allowed for.     

Cryopreservation of red snapper (Lutjanus argentimaculatus) sperm: Effect of cryoprotectants and cooling rates on sperm motility, sperm viability, and fertilization capacity

Sperm cryopreservation of red snapper (Lutjanus argentimaculatus) is essentially unexplored, although many species of the Lutjanidae family are considered to be high-value commercial species. The objective of this study was to develop a species-specific cryopreservation protocol for red snapper (L. argentimaculatus) sperm by optimizing cryoprotectants and cooling rates in the cryopreservation procedure. Ten cryoprotectants at four concentrations and two freezing protocols were examined in two separate experiments. In the first experiment, toxicity studies of dimethyl sulfoxide (DMSO), glycerol, propylene glycol (PG), ethylene glycol (EG), formamide, methanol, ethanol, sucrose, trehalose, and dimethylacetamide (DMA) on sperm motility were performed. Semen diluted 1:1 in Ringer solution were exposed to cryoprotectants at four final concentrations of 5%, 10%, 15%, or 20% for periods of 10, 20, 30, 40, 50, 60, 90, and 120 min at room temperature (25 °C). The cryoprotectants and concentrations that showed the least toxic effect on sperm motility were selected for cryopreservation trials. In the second experiment, selected cryoprotectants were then assessed for freezing capacity of sperm as follows: DMSO 5% and 10%, PG 5% and 10%, EG 5% and 10%, ethanol 5%, and methanol 5%. Semen was diluted 1:1 in Ringer solution and equilibrated with selected cryoprotectants for 10 min at room temperature. Sperm were frozen in a controlled-rate programmable freezer at four cooling rates of 3, 5, 10, and 12 °C/min from an initial temperature of 25 °C to final temperatures of −40 or −80 °C before plunging into liquid nitrogen. Sperm equilibrated in 10% DMSO and cooled at a rate of 10 °C/min to a final temperature of −80 °C had the highest motility (91.1 ± 2.2%) and viability (92.7 ± 2.3%) after thawing. The fertilization rate of frozen-thawed sperm (72.4 ± 2.4%) was not different (P > 0.05) from that of fresh sperm (75.5 ± 2.4%). This study apparently represents the first reported attempt for cryopreservation of L. argentimaculatus sperm.     

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

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

Morphological and physiological adaptive traits of Mediterranean narrow endemic plants: The case of Centaurea gymnocarpa (Capraia Island,Italy)

A case study on Centaurea gymnocarpa Moris & De Not., a narrow endemic species, was carried out by analyzing its morphological, anatomical, and physiological traits in response to natural habitat stress factors under Mediterranean climate conditions. The results underline that the species is particularly adapted to the environment where it naturally grows. At the plant level, the above-ground/below-ground dry mass (1.73 ± 0.60) shows its investment predominately in the above-ground structure with a resulting total leaf area per plant of 1399 ± 94 cm². The senescent attached leaves at the base of the plant contribute to limit leaf transpiration by shading soil around the plant. Moreover, the dense C. gymnocarpa leaf pubescence, leaf rolling, the relatively high leaf mass area (LMA = 12.3 ± 1.3 mg cm⁻²) and leaf tissue density (LTD = 427 ± 44 mg cm⁻³) contribute to limit leaf transpiration, also postponing leaf death under dry conditions. At the physiological level, a relatively low respiration/photosynthesis ratio (R/P_N) in spring results from high R [2.26 ± 0.59 μmol (CO₂) m⁻² s⁻¹] and P_N [12.3 ± 1.5 μmol (CO₂) m⁻² s⁻¹]. The high photosynthetic nitrogen use efficiency [PNUE = 15.5 ± 0.4 μmol (CO₂) g⁻¹ (N) s⁻¹] shows the large amount of nitrogen (N) invested in the photosynthetic machinery of new leaves, associated to a high chlorophyll content (Chl = 35 ± 5 SPAD units). On the contrary, the highest R/P_N ratio (1.75 ± 0.19) in summer is due to a significant P_N decrease and increase of R in response to drought. The low PNUE [1.5 ± 0.2 μmol (CO₂) g⁻¹ (N) s⁻¹] in this season is indicative of a greater N investment in leaf cell walls which may contribute to limit transpiration. On the contrary, the low R/P_N ratio (0.05 ± 0.02) in winter is resulting from the limited enzyme activity of the respiratory apparatus [R = 0.23 ± 0.08 μmol (CO₂) m⁻² s⁻¹] while the low PNUE [3.5 ± 0.2 μmol (CO₂) g⁻¹ (N) s⁻¹] suggests that low temperatures additionally limit plant production. The experiment of the imposed water stress confirms that the C. gymnocarpa growth capability is in conformity with the severe conditions of its natural habitat, likewise as it may be the case with others narrow endemic species that have occupied niches with similar extreme conditions.     

A cryoprotective and cold-adapted 1,3-β-endoglucanase from cherimoya (Annona cherimola) fruit

A 1,3-β-glucanase with potent cryoprotective activity was purified to homogeneity from the mesocarp of CO₂-treated cherimoya fruit (Annona cherimola Mill.) stored at low temperature using anion exchange and chromatofocusing chromatography. This protein was characterized as a glycosylated endo-1,3-β-glucanase with a M_r of 22.07 kDa and a pI of 5.25. The hydrolase was active and stable in a broad acidic pH range and it exhibited maximum activity at pH 5.0. It had a low optimum temperature of 35 °C and it retained 40% maximum activity at 5 °C. The purified 1,3-β-glucanase was relatively heat unstable and its activity declined progressively at temperatures above 50 °C. Kinetic studies revealed low k_cat (3.10 ± 0.04 s⁻¹) and K_m (0.32 ± 0.03 mg ml⁻¹) values, reflecting the intermediate efficiency of the protein in hydrolyzing laminarin. Moreover, a thermodynamic characterization revealed that the purified enzyme displayed a high k_cat at both 37 and 5 °C, and a low E_a (6.99 kJ mol⁻¹) within this range of temperatures. In vitro functional studies indicated that the purified 1,3-β-glucanase had no inhibitory effects on Botrytis cinerea hyphal growth and no antifreeze activity, as determined by thermal hysteresis analysis using differential scanning calorimetry. However, a strong cryoprotective activity was observed against freeze-thaw inactivation of lactate dehydrogenase. Indeed, the PD₅₀ was 8.7 μg ml⁻¹ (394 nM), 9.2-fold higher (3.1 on a molar basis) than that of the cryoprotective protein BSA. Together with the observed accumulation of glycine-betaine in CO₂-treated cherimoya tissues, these results suggest that 1,3-β-glucanase could be functionally implicated in low temperature-defense mechanism activated by CO₂.     

Determination of the membrane permeability characteristics of Pacific oyster, Crassostrea gigas, oocytes and development of optimized methods to add and remove ethylene glycol

In order for cryopreservation to become a practical tool for aquaculture, optimized protocols must be developed for each species and cell type. Knowledge of a cell’s osmotic tolerance and membrane permeability characteristics can assist in optimized protocol development. In this study, these characteristics were determined for Pacific oyster oocytes and modified methods for loading and unloading ethylene glycol (EG) were tested. Oocytes were found to behave as ideal osmometers and their osmotically inactive fraction (V_b) was calculated to be 0.48. Oocytes exposed to NaCl solutions of 0.6 to 2.3 Osm fertilized at rates equivalent to oocytes left in seawater. This corresponds to volume changes of +27.3 and −38.1 ± 1.2%. The permeability of the oocytes to water (L_p) was determined to be 3.8 ± 0.4 × 10⁻², 5.7 ± 0.8 × 10⁻², and 13.2 ± 1.3 × 10⁻² μm min⁻¹ atm⁻¹, when measured at temperatures of 5, 10 and 20 °C. The respective EG permeability values (P_s) were 9.5 ± 0.1 × 10⁻⁵, 14.6 ± 1.2 × 10⁻⁵, and 41.7 ± 2.4 × 10⁻⁵ cm min⁻¹. The activation energies for L_p and P_s were determined to be 14.5 and 17.5 kcal mol⁻¹, respectively. Different models for EG loading and unloading from oocytes were developed and tested. Post-thaw fertilization did not differ significantly between a published step addition method and single step addition at 20 °C. This represents a considerable reduction in handling. The results of this study demonstrate that the cryobiological characteristics of a given cell type should be taken into account when developing cryopreservation methods.     

Effect of intercellular junction protein expression on water transport during freezing of MIN6 cells

A mouse insulinoma (MIN6) strain in which connexin expression has been inhibited by antisense technology holds promise as an experimental model system for investigating the role of gap junctions in intercellular ice propagation. However, to properly interpret measurements of intracellular ice formation kinetics, the effects of cell dehydration on cytoplasmic supercooling must be determined. Thus, the cell membrane water permeability in monolayer cultures of the antisense-transfected MIN6 strain was measured using a fluorescence quenching method. By repeating the experiments at 4 °C, 12 °C, 21 °C, and 37 °C, the activation energy for water transport was determined to be E_a = 51 ± 3 kJ/mol. Although differences between membrane permeability measurements in theantisense and wild-type strains were not statistically significant, simulation of water transport during rapid freezing (130 °C/min) predicted that intracellular supercooling in the genetically modified MIN6 strain may become significantly larger than the supercooling in wild-type cells at temperatures below −15 °C.     

Spermatozoa from the maned wolf (Chrysocyon brachyurus) display typical canid hyper-sensitivity to osmotic and freezing-induced injury,but respond favorably to dimethyl sulfoxide

We assessed the influences of medium osmolality, cryoprotectant and cooling and warming rate on maned wolf (Chrysocyon brachyurus) spermatozoa. Ejaculates were exposed to Ham’s F10 medium (isotonic control) or to this medium plus NaCl (350–1000 mOsm), sucrose (369 and 479 mOsm), 1 M glycerol (1086 mOsm) or dimethyl sulfoxide (Me₂SO, 1151 mOsm) for 10 min. Each sample then was diluted back into Ham’s medium and assessed for sperm motility and plasma membrane integrity. Although glycerol and Me₂SO had no influence (P > 0.05), NaCl and sucrose solutions affected sperm motility (P < 0.05), but not membrane integrity. Motility of sperm exposed to <600 mOsm NaCl or sucrose was less (P < 0.05) than fresh ejaculate, but comparable (P > 0.05) to the control. As osmolality of the NaCl solution increased, motility decreased to <5%. In a separate study, ejaculates were diluted in Test Yolk Buffer containing 1 M glycerol or Me₂SO and cooled from 5 °C to −120 °C at −57.8 °C, −124.2 °C or −67.0 °C/min, frozen in LN₂, thawed in a water bath for 30 s at 37 °C or 10 s at 50 °C, and then assessed for motility, plasma- and acrosomal membrane integrity. Cryopreservation markedly (P < 0.05) reduced sperm motility by 70% compared to fresh samples. Higher (P < 0.05) post-thaw motility (20.0 ± 1.9% versus 13.5 ± 2.1%) and membrane integrity (51.2 ± 1.7% versus 41.5 ± 2.2%) were observed in samples cryopreserved in Me₂SO than in glycerol. Cooling rates influenced survival of sperm cryopreserved in glycerol with −57.8 °C/min being advantageous (P < 0.05). The findings demonstrate that although maned wolf spermatozoa are similar to domestic dog sperm in their sensitivity to osmotic-induced motility damage, the plasma membranes tolerate dehydration, and the cells respond favorably to Me₂SO as a cryoprotectant.     

High-rate nitrogen removal by the Anammox process at ambient temperature

The purpose of this study is to investigate the nitrogen removal performance of the anaerobic ammonium oxidation (Anammox) process and the microbial community that enables the Anammox system to function well at ambient temperatures. A reactor with a novel spiral structure was used as the gas-solid separator. The reactor was fed with synthetic inorganic wastewater composed mainly of NH₄⁺-N and NO₂⁻-N, and operated for 92 days. Stable nitrogen removal rates (NRR) of 16.3 and 17.5 kg-N m⁻³ d⁻¹ were obtained at operating temperatures of 33 ± 1 and 23 ± 2 °C, respectively. To our knowledge, such a high NRR at ambient temperatures has not been reported previously. In addition, the experiments presented herein confirm that high influent NO₂⁻-N concentration of 460 mg L⁻¹ did not noticeably inhibit the Anammox activity. Furthermore, the freshwater Anammox bacterium KU2, which was identified as the dominant bacterial species in the consortium by 16S rRNA gene analysis, is considered to be responsible for the stable nitrogen removal performance at ambient temperatures.     

Thermopreference,tolerance and metabolic rate of early stages juvenile Octopus maya acclimated to different temperatures

Thermopreference, tolerance and oxygen consumption rates of early juveniles Octopus maya (O. maya; weight range 0.38–0.78 g) were determined after acclimating the octopuses to temperatures (18, 22, 26, and 30 °C) for 20 days. The results indicated a direct relationship between preferred temperature (PT) and acclimated temperature, the PT was 23.4 °C. Critical Thermal Maxima, (CTMax; 31.8±1.2, 32.7±0.9, 34.8±1.4 and 36.5±1.0) and Critical Thermal Minima, (CTMin; 11.6±0.2, 12.8±0.6, 13.7±1.0, 19.00±0.9) increased significantly (P<0.05) with increasing acclimation temperatures. The endpoint for CTMax was ink release and for CTMin was tentacles curled, respectively. A thermal tolerance polygon over the range of 18–30 °C resulted in a calculated area of 210.0 °C². The oxygen consumption rate increased significantly α=0.05 with increasing acclimation temperatures between 18 and 30 °C. Maximum and minimum temperature quotients (Q₁₀) were observed between 26–30 °C and 22–26 °C as 3.03 and 1.71, respectively. These results suggest that O. maya has an increased capability for adapting to moderate temperatures, and suggest increased culture potential in subtropical regions southeast of México.     

Investigating the deep supercooling ability of an Alaskan beetle, Cucujus clavipes puniceus, via high throughput proteomics

Cucujus clavipes puniceus is a freeze avoiding beetle capable of surviving the long, extremely cold winters of the Interior of Alaska. Previous studies showed that some individuals typically supercool to mean values of approximately − 40 °C, with some individuals supercooling to as low as − 58 °C, but these non-deep supercooling (NDSC) individuals eventually freeze if temperatures drop below this. However, other larvae, especially if exposed to very cold temperatures, supercool even further. These deep supercooling (DSC) individuals do not freeze even if cooled to − 100 °C. In addition, the body water of the DSC larvae vitrifies (turns to a glass) at glass transition temperatures of − 58 to − 70 °C. This study examines the proteomes of DSC and NDSC larvae to assess proteins that may contribute to or inhibit the DSC trait. Using high throughput proteomics, we identified 138 proteins and 513 Gene Ontology categories in the DSC group and 104 proteins and 573 GO categories in the NDSC group. GO categories enriched in DSC include alcohol metabolic process, cellular component morphogenesis, monosaccharide metabolic process, regulation of biological quality, extracellular region, structural molecule activity, and antioxidant activity. Proteins unique to DSC include alpha casein precursor, alpha-actinin, vimentin, tropomyosin, beta-lactoglobulin, immunoglobulins, tubulin, cuticle proteins and endothelins.     

Effect of temperature on isoproterenol-induced increases in left ventricular developed pressure

The goal of this project was to determine the effects of elevated cardiac temperature on preload-dependent and preload-independent regulation of left ventricular developed pressure (LVDP) in Langendorff-perfused, electrically paced (420 bpm), Sprague-Dawley rat hearts. LVDP responses to steady-state isoproterenol infusions (10⁻⁸ M) were determined at 37, 38, 39, and 40 °C. Preload-dependent LVDP was determined at 37 and 40 °C. Isoproterenol-induced LVDP and preload-dependent LVDP time controls were conducted in a separate group maintained at 37 °C. The percent increase in LVDP during isoproterenol infusion significantly decreased at 40 °C to 42±6 (SE), compared to 55±9, 55±6, and 53±7% at 37, 38, and 39 °C, respectively. No significant differences were observed in the percent increase in LVDP to isoproterenol among the corresponding time controls (50±6, 47±3, 56±4, and 56±5%). Preload-dependent LVDP decreased across the experimental protocol, but there were no cardiac temperature effects. These data indicate that β-adrenergic mediated contractility is not altered by moderate heating from normothermia but is compromised at very high temperatures (40 °C). Cardiac temperatures from 37 to 40 °C do not alter the inherent preload-dependent LVDP, indicating that the Frank–Starling relation is not directly affected within this temperature range.     

Temperature record in the oxygen stable isotopes of Pacific sardine otoliths: Experimental vs. wild stocks from the Southern California Bight

Pacific sardines (Sardinops sagax) are commercially fished in Canada, USA, and Mexico along approximately 5000 km of coastal waters that experience a wide range of temperatures. Trinational management of the species can be problematic because the connectivity between spawning, recruitment, stock residency, and migration in some years may not be well predicted. Oxygen isotopic value of otoliths (δ¹⁸O_otolith) has been used to infer stock residency and movement of fish populations within regions, but few studies have used laboratory data to establish a predictive temperature model to validate δ¹⁸O_otolith values of wild fish. We conducted a growth experiment with juveniles at different temperatures using Southern California Bight (SCB) seawater to test the assumption that Pacific sardine otoliths accurately record environmental water temperature in the presence of constant salinity. Sardine δ¹⁸O_otolith values were significantly and negatively correlated with temperature according to the linear model:

δ¹⁸Ootolith(‰)−δ¹⁸Owater(‰)=−0.132(±0.003 SE)×Temperature(°C)+2.455(±0.043 SE)