Effects of pinealectomy, melatonin injections and melatonin antibody production on the mean duration of individual hibernation bouts in Spermophilus tridecemlineatus

1. 1.|Pinealectomy did not significantly alter the length of the mean durations of individual hibernation bouts in adult Spermophilus tridecemlineatus.

2. 2.|Similarly, no statistically-significant differences in mean durations of individual hibernation bouts between pinealectomized and sham-pinealectomized group squirrels were observed for young-of-the year S. tridecemlineatus

3. 3.|Some apparent differences of pinealectomy are suggested as they relate to age, stage of hibernation cycle and time of year during which pinealectomies are performed.

4. 4.|Daily s.c. injections of 50 μg of melatonin late in the subjective photophase induced no statistically-significant differences in mean durations of individual hibernation bouts between either adult, female pinealectomized or intact S. tridecemlineatus and their respective controls.

5. 5.|Adult, female S. tridecemlineautus with reduced titres of endogenous melatonin displayed on statistically-significant difference in the mean duration of initial hibernation bouts compared with controls.

6. 6.|It is possible that melatonin per se or that pinealectomy or melatonin titre alterations are generally failing to induce any significant changes in the torpor/arousal cycles of seasonal hibernators; or that a parameter other than the duration of torpor/arousal cycles is being modulated by the pineal complex.

Thermosensitivity of the preoptic region and the spinal cord in the golden hamster

1. 1.|The effects of thermal stimulation of the preoptic region (POAH) and the spinal cord on non-shivering thermogenesis (NST) and shivering were studied in euthermic golden hamsters.

2. 2.|Shivering intensity is suppressed by heating the POAH but is independent of spinal cord temperature. Therefore, NST in the interscapular brown adipose tissue does not suppress shivering.

3. 3.|NST is inhibited by heating of the POAH as well as of spinal cord. It is discussed that the control of NST by two different central thermosensitive areas is significant for thermoregulation during exercise.

Seasonal acclimatization in the migratory hamster Cricetulus migratorius—the role of photoperiod

1. 1.|The migratroy hamster Cricetulus migratorius, a small nocturnal rodent, inhabits ecosystems characterized by dramatic seasonal fluctuations of ambient temperatures. The aim of this study was to assess seasonal acclimatization of its thermoregulatory system.

2. 2.|Heat production by means of oxygen consumption and body temperature in various ambient temperatures as well as non-shivering thermogenesis were measured in C. migratorius. The hamsters were acclimated to two different photoperiod regimes (16L:8D and 8L:16D) at a constant ambient temprature of 24°C. Overall thermal conductance was calculated for such hamsters.

3. 3.|The results of this study indicate that photoperiod manipulations adjust the thermoregulatory system of the migratory hamster mainly by affecting overall thermal conductance.

Thermal resistance of the ciliary activity in the gills of the fresh water mussel Anodonta anatina

1. 1.|The thermal resistance of the activity of frontal cilia in the median gills of the fresh water mussel Anodonta anatina was studied.

2. 2.|The resistance acclimation appeared in 2 days in the gills of intact animals, but not in the isolated gills kept at 4, 14 and 24°C, for between 1 to 3 days.

3. 3.|Warm-acclimation increased the ACh sensitivity of the gills of intact mussels.

4. 4.|Isolation of the gills enhanced the thermal resistance.

5. 5.|ACh, choline and tetramethylammonium enhanced the thermal resistance in the isolated gills. whereas atropine and physostigmine diminished it.

6. 6.|It is concluded that in A. anatina the control if the thermal resistance is probably neural.

Tolerances of Nauplii of Balanus balanoides (L.) and Elminius modestus (Darwin) exposed to cyclical temperature fluctuations

1. 1.|Newly-released larvae of both E. modestus and B. balanoides show similar tolerances to steady temperature levels.

2. 2.|Both species show an ability to withstand a wider range of temperatures when subjected to cyclic thermal shocks.

3. 3.|E. modestus shows a greater tolerance to short-term thermal shocks than B. balanoides.

Metabolic effects of thyroid hormones at a low temperature in the snake

1. 1.|The metabolic role of the thyroid gland was studied in intact snakes, Naja naja and Ptyas korros treated with tri-iodo-thyronine (T₃) and thyroxine (T₄) and in thyroidectomized (Tx) N. naja kept at 21°C by analyzing tissue composition and glycogen phosphorylase a activity.

2. 2.|Liver weight was unaffected by thyroid hormone injection in both species but decreases in liver glycogen followed T₃ or T₄ injection, and there was an increase in liver glycogen in N. naja. These changes in liver glycogen were accompanied by a decrease in glycogen phosphorylase a activity with T₃ injection. T₃ decreased muscle glycogen in Ptyas and Tx increased it in N. naja.

3. 3.|T₃ increased % liver lipid in Ptyas but not in Naja.

4. 4.|Between species, there were differences in liver weight, blood glucose level, cholesterol level and % muscle lipid.

5. 5.|The results showed that thyroid hormones affected carbohydrate and lipid metabolism at a low temperature of 21°C, although the significance is not known.

Effect of temperature on growth and bioenergetics of a tropical moth

1. 1.|Larval development and metamorphosis of Achaea junta were prolonged at 22°C, compared to 27, 32 and 35°C.

2. 2.|Overall rates of consumption, assimilation, production and metabolism of the larvae increased with temperature.

3. 3.|Efficiencies of assimilation and conversion of the digested food were significantly altered by life stage and temperature.

4. 4.|About 60% of the pupal energy was transferred to the imago at the tested temperatures.

Cold-hardiness in several species of land snails

1. 1.|Mean supercooling points (SCP) of Anguispira alternata (Say) gradually declined in autumn and increased in spring. SCP also declined in autumn in Discus conrkhitei (Newcomb) and Gastrocopta armifera (Say).

2. 2.|Supercooling ability varied among the species, being the greatest in G. armifera.

3. 3.|Prolonged exposure of winter animals to high temperatures resulted in only a modest increase in SCP.

4. 4.|Low temperature survival of D. cronkhitei and G. armifera was slightly poorer than predicted by the mean SCP.

Thermosensitivity during embryonic development of Lymnaea stagnalis (Mollusca)

1. 1.|The percentage of survival after 1 hr at 40.0°C is lowest at the larval trochophore stage and at hatching of the young snail.

2. 2.|Heat resistance depends on the stage of development.

3. 3.|From the early cleavage stage onwards a higher percentage of embryos can withstand high temperature after a previous heat treatment than without it.

4. 4.|The pattern of thermosensitivity is discussed in relation to the organizational level of the stage of development.

5. 5.|It is concluded that the developing Lymnaea is a suitable system to study heat resistance and thermotolerance at the level of cells, organs and organism.

Interactions of season and temperature acclimation in the control of metabolism in Amphibia

1. 1.|Studies concerning the seasonal variation and the temperature acclimation of metabolism and their control in Amphibia are reviewed.

2. 2.|Both season and temperature acclimation affect the activities of the central and autonomic nervous systems.

3. 3.|These changes are mediated especially by alterations in the activity of the thyroid and through the autonomic nerves.

4. 4.|The fact that common control mechanisms are involved may explain some of the often observed metabolic interactions of season and temperature acclimation.

Thermal acclimation and hardening in tadpoles of the bullfrog, Rana catesbeiana

1. 1.|Critical thermal maxima (CTMax) and minima (CTMin) were measured to evalute thermal hardening in Rana catesbeiana.

2. 2.|Tadpoles show heat hardening and CTMax acclimation, and both responses are influenced by developmental stage.

3. 3.|The first evidence of cold hardening in vertebrates is reported here.

4. 4.|Heat hardening significantly reduces cold tolerance, but there is otherwise no evidence of a cross-hardening effect.

Thermal responses of the fresh water turtle Mauremys caspica to step-function changes in the ambient temperature

1. 1.|The turtle Mauremys caspica cools significantly faster than it heats in air. The heating/cooling ratio is 0.49.

2. 2.|The variation of body temperature in relation to time-course in response to a step-function change of environmental temperature, fitted to a second-order system improves that of a first-order system.

3. 3.|The gradient between ambient temperature (T_a) and equilibrium body temperature (T_b) increases significantly and progressively when ambient temperature rises over 25°C.

4. 4.|At 40°C thermoregulatory hyperventilation was detected, implying an increase in air convection requirement (ventilation relative to O₂ consumption, ).

Hatching of freshwater sponge gemmules after low temperature exposure: Ephydatia mülleri (Porifera: Spongillidae)

1. 1.|Gemmules of Ephydatia mülleri can withstand exposure to temperatures down to −80°C for 63 days without loss of hatchability.

2. 2.|Hatching is slowed following exposure to temperatures below −27°C.

3. 3.|There is a slight but significant relationship between gemmule size and the time to hatch.

4. 4.|This species can withstand long-term exposure to winter air temperatures occurring within its known geographic range.

Non-shivering thermogenesis in winter-acclimatized and in long-scotophase and cold-acclimated Apodemus mystacinus (Rodentia)

1. 1.|Resistance to cold through non-shivering thermogenesis (the absolute increase in O₂ consumption caused by noradrenaline injection) was increased 3-fold in individuals of the broad-toothed mouse A. mystacinus, kept for 3 weeks under a short photoperiod (long scotophase 8L:16D) at an ambient temperature of 28°C, compared to control conditions (12L:12D; 28°C), and did not differ significantly from the winter-acclimatized group.

2. 2.|Acclimation of the same individuals to long scotophase and cold (8L:16d; 7°C) caused a significant (P < 0.01) increase in absolute O₂ consumption and maximal body temperature, as a response to noradrenaline injectin, when compared to long-scotophase individuals (8L:16D; 28°C).

3. 3.|The results of this study support the idea that winter acclimatization of heat-production mechanisims may be induced by the extension of scotophase, which cycles very regulary in nature and in the Mediterranean region occurs before the beginning of the cold season.

Behavioural thermoregulation in two species of robber flies occupying different grassland microhabitats

1. 1.|The robber flies Machimus occidentalis and Machimus formosus are ambush predators that occur sympatrically in grassland habitats of southwestern Montana, U.S.A., although the former occurs earlier in the season.

2. 2.|Early in daily foraging periods, when ambient temperatures are relatively low, the two species exhibited similar behaviours. They perched in a crouched posture on fully insolated bare soil surfaces and oriented their longitudinal and dorsoventral axes to maximize the incident solar radiation intercepted by the broad lateral surface of the thorax. Measurements of operative body temperature of flies in different locations, orientations, and postures indicate that such basking can significantly raise body temperature.

3. 3.|Their thermoregulatory tactics diverged as daily temperatures and solar radiation loads rise.

4. 4.|Like previous grassland species studied, M. occidentalis moved upward onto vegetation, where crouched postures and orientation to the sun disappeared.

5. 5.|Machimus formosus, on the other hand, took refuge in the shaded portions of ground squirrel (Citellus sp.) and badger (Taxidea taxus) burrows.

6. 6.|In both cases, the vertical movements resulted in lower body temperatures than would occur if flies remained on the fully insolated soil surfaces.

7. 7.|We compare the tactics of these two species with those of previous grassland species studied.

Stereological analysis of mitochondria from brains of temperature acclimated goldfish, Carassius auratus L. (5 and 30°C)

1. 1.|The mitochondrial population in hypothalamic and hypophysial brain tissue from warm (30°C) and cold (5°C) acclimated goldfish (Carassius auralus L.) was analyzed using sterological techniques.

2. 2.|It was revealed that there is a significantly larger volume density (Vv) in the cold acclimated tissue, with no significant difference in either of the surface densities (Svext and Svint) from either of the brain areas.

3. 3.|The hypothalamic brain tissue has a significantly lower specific surface (S/V) in the cold acclimated tissue but there is not a significant difference in this parameter for the hypophysial brain tissue.

4. 4.|The values for these three parameters (Vv, Svext and SVint, and S/V) indicate that mitochondria from acclimated brain tissue undergo shape changes in response to thermal stress.

5. 5.|We suggest that the shape changes may be related to the change in the phospholipid composition of the inner mitochondrial membrane with acclimation temperature.

Daphnia development and reproduction: Responses to temperature

1. 1.|The development times and reproduction were measured for Daphnia pulex and Daphnia magna from 5 to 30°C at 5°C increments.

2. 2.|The general trends for D. pulex and D. magna were for the duration of all juvenile instars to be less than that of adults and for the last juvenile (or adolescent) instar to be longer than all previous juvenile instars.

3. 3.|The number of juvenile instars both species pass through before adulthood is influenced by temperature with increasing numbers occurring at temperature extremes.

4. 4.|Duration of development time decreased over the entire range of increasing temperatures measured for D. pulex but increased for D. magna at 30°C in relation to 25°C.

5. 5.|Quadratic models were less desirable than simple linear logarithmic transformations of the form ln Y = ln a + b ln X for describing the temperature/development relationship.

6. 6.|The greatest young production occurs at 15 and 20°C with significant decreases occurring at temperatures above and below these.

7. 7.|The observed temperature-dependent phenomena an the ecological relationships for the two species are discussed.

How are neuronal thermosensitivity and lack of thermoreception related in the duck's hypothalamus? A tentative answer

1. 1.|In 15 conscious Pekin ducks, 40 “warm sensitive” hypothalamic neurons were identified according to their discharge rates at 40°C T_hy (F₄₀), local temperature coefficients (Δ/ΔT) and Q₁₀.

2. 2.|Q₁₀ and either F₄₀ or ΔF/ΔT were little or not related.

3. 3.|A positive correlation between F₄₀ and ΔF/ΔT was observed which was particularly close (r = 0.94 and 0.96) when the neurons were classified according to their Q₁₀ of <2 and >2.

4. 4.|The results suggest that neurons with positive temperature coefficients in the duck's hypothalamus mostly exhibit linear to exponential temperature-discharge relationships.

5. 5.|This is an contrast to observations on mammalian hypothalamic thermosensitive neurons and may relate to the absence of the thermosensory function in the duck's rostral brainstem.

Temperature gradients in the nasal cavity of the rabbit

1. 1.|Temperatures at four sites along the ventral nasal concha were recorded in four unrestrained rabbits exposed to ambient temperatures from 0 to 35°C.

2. 2.|The nasal temperatures decreased and temperature gradients from proximal to distal parts of the concha increased in cold-exposed rabbits.

3. 3.|The temperature gradients increased also during panting in heat-stressed rabbits.

4. 4.|The ventral nasal concha is suggested to be an efficacious heat exchanger both in cold and hot ambient, due to its geometry and vascularization.

Acute adjustment of thermal tolerance in vertebrate ectotherms following exposure to critical thermal maxima

1. 1.|Heat hardening in a transitory increase in heat tolerance following a sublethal exposure to lethal high temperatures.

2. 2.|Within 1–2 h of an initial exposure to the critical thermal maximum (CTM), the CTM of two species of amphibians and two species of fish had increased significantly above the initial level and then decreased to the initial level within 24 h.

3. 3.|Experiments with exposure to sub-CTM temperatures and multiple exposures to the CTM indicated that hardening requires exposure to the CTM and may be the maximum CTM attainable by the animal.

4. 4.|Diel and seasonal variation had significant effects on hardening ability.

5. 5.|Field evidence suggests that heat hardening is adaptive in that it provides an acute means of adjustment to extreme fluctuations in diurnal temperatures.