Freeze tolerance and intolerance as strategies of winter survival in terrestrially-hibernating amphibians

• 1.1. The ability to tolerate extracellular freezing as an adaptation for winter survival was tested in seven species of terrestrially-hibernating amphibians found in eastern Canada.
• 2.2. All species had only moderate supercooling abilities, with whole animal supercooling points of −1.5 to −3°C.
• 3.3. Two salamander species, Plethodon cinereus and Ambystoma laterale, and the toad, Bufo americamts, were freezing intolerant and were killed when frozen for 24 hr at temperatures just below their supercooling points. The major winter strategy of these animals appears to be behavioural avoidance of subzero temperatures.
• 4.4. Four species of frogs Rana sylvatica, Hyla versicolor, Hyla crucifer and Pseudacris triseriata, survived extracellular freezing at moderate subzero temperatures (−2 to −4°C) for periods of time ranging up to 2 weeks.
• 5.5. All four frog species accumulated low molecular weight carbohydrates as cryoprotectants, glycerol being the major cryoprotectant in adult H. versicolor, while immature adults of this species as well as the other three species all produced high levels of glucose as the cryoprotectant.

     

The effects of osmotic stressors on the stenohaline carp (Cyprinus carpio)

• 1.1. Carp were acclimatized to different concentration of urea and mannitol.
• 2.2. The fish survived in 300 mOsm urea and 262 mOsm mannitol for a longer period. Higher concentrations were only tolerated for a short time.
• 3.3. Urea penetrated into the animals. The internal concentration of urea in plasma was nearly equal to the outside concentration after 7 days. Therefore a very high internal osmolality was adjusted (sum of normal and urea osmolality).
• 4.4. Urea treatment only resulted in changes of Ca level, while the concentration of other electrolytes was not clearly varied.
• 5.5. Extracellular space of muscle was reduced while the intracellular space remained unchanged after urea treatment.
• 6.6. Mannitol treatment resulted in changes of electrolyte concentrations due to dehydration.
• 7.7. After 1 day of treatment the concentration of Na in plasma decreased which might indicate the limitation of tolerance.
• 8.8. Immediate shrinkage of ICS and, later, reduction of ECS were clear reactions to mannitol influence.

     

The effect of reduced salinity on tissue and plasma composition of the dogfish,Squalus acanthias

• 1.1. Dogfish (Squalus acanthias) were acclimated to reduced salinities and their plasma, muscle tissue and erythrocytes subsequently analysed.
• 2.2. Decrease in the osmolarity of the plasma was principally due to a fall in urea concentration and a significant fall in the concentrations of sodium and chloride.
• 3.3. Changes in the muscle and erythrocytes in dilute media were a decrease in urea, potassium, sodium and chloride concentrations.
• 4.4. The concentrations of the free amino acids in the muscle and the red blood cells decreased more than would be expected by the movements of water only.
• 5.5. The results were discussed in relation to the regulation of cellular volume and the involvement of the free amino acid pool of the tissues in this process.

     

Electrolyte changes,cell volume regulation and hormonal influences during acclimation of rainbow trout (Salmo gairdnerii) to salt water

• 1.1. Rainbow trout were acclimated to salt water (1.5, 2.0 or 3.0%, which means 40, 60 or 85% concentrated sea-water) and the electrolyte, glucose and cortisol concentrations of the plasma as well as the extra- and intracellular muscle space, the muscle electrolyte concentrations and the ATPase activity were analysed.
• 2.2. Plasma osmolality, Na⁺, Ca²⁺ and Mg²⁺ concentrations of the plasma had a maximum at 24 hr after the start of acclimation when acclimated to 3.0% salt water. Plasma osmolality, Na⁺ and Mg²⁺ concentrations were significantly higher during the whole acclimation time when exposed to 3.0% salt water.
• 3.3. Variations and regulations of ECS and ICS were clearly demonstrated. The intracellular electrolyte concentrations were also maximal at 24 hr.
• 4.4. The plasma glucose level was just slightly elevated, but the cortisol level clearly indicated a stress response at 24 hr.
• 5.5. The activity of gill Na-K-ATPase increased during the acclimation time.
• 6.6. The regulatory processes in trout during acclimation to salt water are compared with those occurring in tilapia and carp.

     

Osmotic regulation in aqueous humor and blood in the euryhaline fish,Eugerres plumieri

• 1.1. The estuarine fish Eugerres plumieri was acclimated to sea-water concentrations ranging from 6 to 85% sea-water.
• 2.2. Serum and aqueous humor osmolalities were moderately well regulated over the range of concentrations studied.
• 3.3. Serum osmolality and aqueous humor osmolalities conformed to the following relations: serum osmolality = (319 ± 3) + (0.56 ± 0.03) (% sea-water); aqueous humor osmolality = (314 ± 4) + (0.35 ± 0.04) (% sea-water).
• 4.4. Aqueous humor osmolality was more strictly regulated than that of serum, indicating that the retina and nervous system of the fish, which are encased in inextensible structures, are well protected from variations in sea-water concentration in order to minimize osmotically induced changes in cell volume.

     

Sea-water tolerance in freshwater-resident arctic charr (Salvelinus alpinus)

• 1.1. Freshwater-resident Arctic charr acclimated for 2 months at 8°C, 15% were divided into four experimental groups in July and exposed to 1 and 8°C in 15 and 34% salinity.
• 2.2. Only slight changes in gill Na-K-ATPase activity, blood plasma osmolality and blood plasma concentrations of Cl⁻ and Mg²⁺ were found for the fish exposed to 1 or 8°C in brackish water.
• 3.3. When exposed to sea-water at 8°C, an increase in osmolality and in concentrations of Cl⁻ and Mg²⁺ took place during the first 2–3 days, after which it levelled off.
• 4.4. If exposed to sea-water at 1°C, however, marked increases were found for all parameters measured and all the fish were dead within 5 days of exposure.
• 5.5. These results show that freshwater-resident Arctic charr—if acclimated to brackish water—can survive in sea-water during summer if the environmental temperature is not too low.

     

Metabolic responses of the mussels Perna viridis and Perna indica to declining oxygen tension at different salinities

• 1.1. Oxygen uptake and ammonia loss were monitored during responses to reductions of both salinity and oxygen tension (PO₂) in the marine mussels Perna viridis and Perna indica from southern India.
• 2.2. The proportional contribution of protein to total catabolic substrates under natural environmental conditions was as much as 96% in P. viridis, relative to only 19% in P. indica.
• 3.3. Normoxic oxygen consumption remained statistically unchanged in P. viridis conditioned to salinities between 32 and 15‰, with no obvious signs of distress. Although equally unaffected at salinities between 32 and 20‰, P. indica showed significantly reduced oxygen uptake following transfer from 32 to 15‰, and had died within the next 7 days.
• 4.4. At salinities greater than 20‰, P. viridis was better able than P. indica to regulate oxygen consumption independent of PO₂.
• 5.5. P. indica showed a compensatory increase in oxyregulatory capacity at 15‰. This exceeded unstressed abilities, helping to maintain albeit reduced oxygen uptake throughout wider ranges of PO₂.
• 6.6. Different responses recorded in each of these tropical and often intertidal species were in accordance with their natural distributions. Nevertheless, the oxyregulatory capacity in both species was higher than in bivalves from temperate and/or subtidally restricted habitats.

     

Urea synthesis and osmotic stress in the terrestrial anurans Bufo woodhousei and Hyla cadaverina

• 1.1. Bufa woodhousei. a terrestrial toad, and Hyla cadarerina, a terrestrial treefrog, accumulate and tolerate high concentrations of urea in the body fluids during dehydration or reduced water turnover (up to 280 mM urea in B. woodhousei, 140 mM urea in H. cadaverina).
• 2.2. In contrast to Rana cancrivora. Xenopus laevis and Scaphiopus couchi (considered to be unusual in their ability to handle osmotic stress), B. woodhousei and H. cadaverina do not increase the rate of urea synthesis and therefore the rate of urea accumulation in the body fluids in response to dehydration.
• 3.3. Hepatic activity of CPS-I. the first enzyme of the urea-ornithine cycle, is correlated with a greater proportion of N waste being formed as urea rather than as NH₃ during times of reduced water turnover or osmotic stress. This results in preferential accumulation of urea rather than of NH₃ in the body fluids.
• 4.4. CPS-I activity is also correlated with the increased N waste production that follows from increased dietary N intake.

     

Adaptative features of amazon fishes: Hemoglobins,hematology, intraerythrocytic phosphates and whole blood Bohr effect of Pterygoplichthys multiradiatus (Siluriformes)

• 1.1. Hemoglobin, hematological parameters, intraerythrocytic phosphates and whole blood Bohr effect of Pterygoplichthys multiradiatus, from the Amazon river, were studied in three different conditions: in their natural environment, acclimated to normoxia and acclimated hypoxia conditions.
• 2.2. Nine anodal hemoglobin fractions were detected on starch gel electrophoresis. No qualitative differences in the Hb electrophoretic patterns were detected in the three studied groups.
• 3.3. Hematocrit, hemoglobin concentration, MCV, MCHC and MCH were different among studied conditions.
• 4.4. GTP was almost absent in the blood of animals in natural conditions and acclimated to hypoxia, but was present at a concentration similar to ATP in normoxic acclimated animals.
• 5.5. There is a tendency for higher Hb-O₂ affinity for hypoxic acclimated/acclimatized animals.

     

The properties of “active” Cl transport across the cornea of the toad Bufo marinus

• 1.1. Active Cl transport occurs from the endothelial to epithelial side of the cornea of Bufo marinus. Na transport is much less and is in the opposite direction.
• 2.2. The rate of Cl transport is not saturable and is linearly related to the Cl concentration on the endothelial side.
• 3.3. Active efflux (endo to epi) of Cl is reduced (50%) by CN and abolished by IAA. Ouabain and Na-free solutions on the endothelial side also reduce Cl efflux.
• 4.4. O₂ consumption or lactate production are also decreased by ouabain or Na-free solutions. However, metabolism was not inhibited by Cl-free solutions or a specific Cl blocking drug bumetanide.
• 5.5. Cl transport exhibits some rather unusual characters and a model is proposed to account for them which involves an exchange of Cl for metabolically produced organic anions.

     

Taxonomic position of some rana species in a dendrogram from their globin composition

• 1.1. The aminoacidic composition of the globin of the genus Rana has been analyzed.
• 2.2. The resulting data and those from five other species of Ranidae, from one species of Pipidae and one of Bufonidae having been compared in pairs according to the formula of Harris and Teller gave origin to a “dissimilarity matrix”.
• 3.3. In a “Phylo” computer program, consistent with Moore's model, the data of the input matrix have been used to find the mutual taxonomic relations of the 11 anuran species examined.

     

Changes in plasma and coelomic fluid composition of the mature salmon (Oncorhynchus keta) during freshwater adaptation

• 1.1. A large amount of coelomic fluid appears at the moment of ovulation in Salmonidae, and the ovulated eggs lie free in the body cavity.
• 2.2. Ion composition and osmolality of the coelomic fluid of the mature female salmon, Oncorhynchus keta, were approximately the same as those of the blood plasma, although an excess of sodium chloride and low levels of organic constituents were noted in the coelomic fluid.
• 3.3. On transfer from seawater to freshwater, a significant reduction in ion concentrations and osmolality of the coelomic fluid was observed in close association with the changes in the plasma values.

     

The effects of temperature and eyestalk extracts on oxygen consumption of the crayfish Cambarus acuminatus (Faxon)

• 1.1. The pattern of VO₂ of 4 and 25°C acclimated Cambarus acuminatus was one of normal compensation with cold acclimation resulting in translation and clockwise rotation of the rate-temperature (R-T) curves.
• 2.2. Acclimation patterns were significantly influenced by the sequence in which crayfish experienced experimental temperatures.
• 3.3. Eyestalk extracts prepared from warm acclimated crayfish significantly decreased VO₂ in eyestalkless cold acclimated recipients.

     

Griffonia simplicifolia I-B4 isolectin receptors in the microcirculatory vessels of the gastrocnemius muscle and heart: Heterogeneity among families of anuran amphibians

• 1.1. A fluorescent derivative of the Griffonia simplicifolia I-B₄ isolectin was used to examine historically the distribution of terminal methyl-α-galactosyl residues in the microcirculatory vessels of the gastrocnemius muscle and the ventricles from four families of anuran amphibians.
• 2.2. The isolectin preferentially bound to capillaries in the gastrocnemius muscles from members of the families Ranidae, Bufonidae and Pipidae, but not from the family Hylidae.
• 3.3. Histological and ultrastructural analyses revealed a primitive sinusoidal endothelial system in the anuran heart, with a less extensive expression of the GSI-B₄ receptors than in skeletal muscle.
• 4.4. These results suggest phylogenetic differences among families of anuran amphibians with regard to the distribution of GSI-B₄ receptors in skeletal and cardiac muscle.

     

Seasonal effects of prolactin on aspects of carbohydrate and lipid metabolism in the goldfish,Carassius auratus

• 1.1. Diurnal and seasonal variations of certain aspects of carbohydrate and lipid metabolism to ovine prolactin (PRL) treatment in the goldfish, Carassius auratus, were examined.
• 2.2. PRL treatment late in the light phase of a long photoperiod during spring depletes liver glycogen stores. During fall liver glycogen levels are not affected by PRL treatment in fishes acclimated to long or short photoperiods. PRL is hypoglycaemic in fall and spring.
• 3.3. PRL administered late in the light phase of a long photoperiod during spring increases plasma and liver total lipids and plasma cholesterol, while decreasing plasma triglycerides. In fall PRL may increase or decrease plasma organic-bound P levels dependent upon injection time.

     

Aestivation in the teleost fish Lepidogalaxias salamandroides (Mees)

• 1.1. Lepidogalaxias salamandroides does not lose water during the first 43 days of aestivation even though it is burrowed in extremely dry soil.
• 2.2. Little urea was accumulated in the body, which suggests that urea production is greatly diminished and/or urea is eliminated in the urine.
• 3.3. Theoretical considerations predict that water fluxes will, in the initial stages of aestivation, be positive until the soil moisture tension is equivalent to the plasma water potential.

     

Breeding and moulting fasts in macaroni penguins: Do birds exhaust their fat reserves?

• 1.1. Plasma concentrations of urea, uric acid and total lipid were compared in pre- and late-fast breeding and moulting macaroni penguins (Eudyptes chrysolophus) to test the hypothesis that birds exhaust their lipid reserves and initiate marked protein utilisation towards the end of natural fasts.
• 2.2. Male and female macaroni penguins fasted for a minimum of 29–32 days and 20 days during the breeding and moult fasts, and the difference in body weight over the sample period (reflecting body weight loss) was 31–34% and 41–47%, respectively.
• 3.3. There was no significant increase in plasma urea or uric acid at the end of either fast, nor any decrease in plasma lipid concentrations compared to pre-fast birds.
• 4.4. These results suggest that macaroni penguins continue to rely mainly on lipid reserves during the later stages of natural fasts. This is consistent with post-fast body composition data for other small penguin species.

     

In vivo responses in plasma osmolality,and intracellular water and solute concentrations in flounder (Platichthys flesus) heart ventricles under acclimation to fresh and sea water

• 1.1. Flounders transferred abruptly from sea to fresh water displayed a gradual decrease in plasma osmolality for 5–6 days (10–15 mOsm daily). When returned to sea water the osmolality increased to the original level within 1 day.
• 2.2. Heart ventricle cell water content remained unchanged during the acclimations, except for a temporary 1.4% reduction within the first 4 hr of sea water acclimation.
• 3.3. During acclimation to sea water intracellular K⁺ increased rapidly in parallel with plasma osmolality. During fresh water acclimation, however, cellular K⁺ decreased rapidly in the first day only, whereas plasma osmolality decreased further.
• 4.4. Cellular taurine remained unchanged during the initial 4 days of fresh water acclimation and then declined 32% within the next 3 days. Upon retransfer to sea water, cellular taurine increased gradually to its original level in the course of 7 days.

     

Cardiac frequency compensation responses of adult blue crabs (Callinectes sapidus Rathbun) exposed to moderate temperature increases

• 1.1. Cardiac frequency patterns of Callincctes sapidus Rathbun were used to evaluate potential thermal stress after exposure to 5°C increases over a range of acclimation temperatures from 5° to 30°C.
• 2.2. An acclimated rate-temperature curve (R-T curve), acute R-T curves of the stabilized rates at the increased temperatures and Q₁₀ temperature coefficients were used to assess the significance of the changes in rate frequency.
• 3.3. The acclimated R-T curve showed that blue crabs go through a series of seasonal adaptation types characterized by a plateau of perfect adaptation for both cold and warm adapted organisms. Paradoxical adaptation occurred between the transition from cold to warm acclimation temperatures.
• 4.4. The acute R-T curves showed that cardiac frequency was highly responsive to a 5°C increase when the organisms were acclimated to low temperatures.
• 5.5. The Q₁₀'s of the acute R-T curves at the warm acclimation temperatures approximated those values derived for the acclimated R-T curve.
• 6.6. This suggests that the temperature increase had a negligible effect on the warm adapted crabs, that is, little or no thermal stress occurred.

     

Effects of acclimation temperature,season, and time of day on the critical thermal maxima and minima of the crayfish Orconectes rusticus

• 1.1. The critical thermal minima (CTMin) and maxima (CTMax) were determined for field-acclimatized and laboratory-acclimated crayfish (Orconectes rusticus) throughout 1984.
• 2.2. The CTMin and CTMax of field-acclimatized crayfish were seasonally adjusted by 9.7 C and 14.7 C respectively.
• 3.3. Seasonal variation in both tolerance regimes persisted in crayfish acclimated in the laboratory at 5 and 25°C for one week; however, no diel variation existed in either the CTMin or CTMax of laboratory-acclimated crayfish.
• 4.4. Integration of thermal acclimation of the CTMin and CTMax with seasonal conditioning may influence the functional capacities of this species when considered in relation to the seasonal ranges in stream temperature.