Thermoregulatory behavior of a tropical marine fish: Canthigaster jactator (Jenkins)

Ten Canthigaster, jactator, tropical marine puffers from Hawaii, were tested individually for 3-day periods in electronic shuttle-boxes (Ichthyotrons) to determine their ability to thermoregulate behaviorally. These fish thermoregulated with a degree of precision comparable to that of temperate freshwater fishes: range 23–31°C, S.D. 1.8–2.4°C, S.E. 0.3–0.5° C. The modal final thermal preferendum was 27°C, comparable to temperate warmwater fishes. The mean preferred temperature did not differ significantly between night (26.5°C) and day (26.9°C); the 24-hr mean was 26.7°C. Apparently at least some tropical marine fishes are capable of thermoregulatory behavior similar to that of temperate freshwater fishes.     

Thermoregulatory behavior of juvenile cromileptes altivelis (serranidae), a tropical marine fish

Ten juvenile Cromileptes altivelis were tested individually for 3-day periods in electronic shuttleboxes to measure their thermoregulatory behavior. The fish voluntarily occupied a 21–27°C span, out of a potentially available 0–50°C range. The mean final thermal preferendum was 24.5°C for all individuals. The thermoregulatory performance of this species is similar to that of cool temperate freshwater fishes.     

Behavioral thermoregulation in the spiny lobster Panulirus Argus (latreille)

Ten spiny lobsters (Panulirus argus) were allowed to thermoregulate individually for 3-day periods in an electronic thermoregulatory shuttlebox which allowed them to control water temperatures (and thereby their own body temperatures) by their movements. The range of preferred (voluntarily occupied) temperatures was 25–35°C (mean 29.9°C; mode 30.0°C; median 30.0°C; midpoint 30.0°C; S_k (skewness, Pearson's coefficient) –0.04; s.e.m. 0.19°C; S.D. 2.32°C). The final thermal preferendum (by the gravitation method) in this species is 30°C.     

Behavioral thermoregulatory abilities of tropical coral reef fishes: a comparison with temperate freshwater and marine fishes

Synopsis Eight species in six different families of tropical marine reef fishes from the Indo-West Pacific region (Naso lituratus, Zebrasoma.flavescens, Balistes fuscus, B. vidua, Forcipiger longirostris, Echidna zebra, Cromileptes altivelis, Canthigaster jactator) were tested for ability to thermoregulate behaviorally in electronic shuttleboxes. All of these species preferred mean temperatures between 20 and 30°C, but differed considerably in thermoregulatory precision. All species avoided lethal high or low temperatures (i.e., they did not die during the tests), and some species thermoregulated as precisely as temperate species. Some temperate species prefer higher temperatures (above 30°C) than do these tropical reef species.     

Low Temperature Tolerance of Pacu, Piaractus mesopotamicus

Pacu, Piaractus mesopotamicus (=Colossoma mitrei), is a South American warm water fish species found in the temperature range of 15–35°C. The culture of a warm water species in temperate regions demands knowledge on its temperature requirements. Pacu introduction into the Israeli fish culture system is being considered. Temperature range in the region is 8–33°C, thus the minimum winter water temperatures might be a limiting factor. To determine what is the minimum temperature pacu would tolerate, and hence which overwintering operations in warm-temperate regions are required for this warm water species, low temperature tolerance tests in the laboratory and observations in the field were carried out. Laboratory experiments reducing temperature by 1–3°C per day were carried out with fish of 150–200g, about the size pacu reach after one culture season. The field observations compared survival of two-year-old pacu of 1.3kg mean weight overwintered in outdoors and in greenhouse ponds. For one-year-old fish 7.5°C was found to be the lower temperature tolerance limit. Two-year-old fish withstand short exposures to this temperature rather well and their lower tolerance limit might be lower. This indicates that in warm-temperate regions pacu should survive in outdoors ponds. In this case some loss of weight should be expected, and suspension of feeding when temperature drops below 16–18°C is recommended to avoid wasting feed that the fish will not consume anyway. To be in the safe side, inflow of the warmest available water into the ponds is recommended if maximum water temperature drops to 10°C or below. Overwintering in greenhouses or other heated facilities would be recommended if an exceptionally cold winter is expected and for regions with lower winter minimum temperatures.     

Temperature preference in two populations of juvenile coho salmon,oncorhynchus kisutch

Synopsis Two groups of coho salmon,Oncorhynchus kisutch, were raised under identical regimes to test the hypothesis that the group from a stream with lower and less variable temperatures would have a lower and less variable preferred temperature than would the group from a stream with warmer and more variable temperatures. The preferred (modal) temperatures in an electronic shuttlebox of coho salmon young from a relatively cool, groundwater-fed stream were slightly lower and less variable than those of young from a warmer and more heterothermal stream (mean = 9.6° C, range: 6–16° C vs. mean = 11.6° C, range: 7–21° C). However, there was a great deal of variation within and among individual fish. While some genetic variation in thermal preference may exist, the species seems best characterized as tolerant of relatively large temperature fluctuations.     

Diel activity and thermoregulatory behavior of a fully aquatic frog: Xenopus laevis

Ten adult Xenopus laevis were tested individually for 48-hr periods, following an initial 24-hr introductory period, in electronic shuttleboxes which allowed them to control water temperatures without operant conditioning. Locomotor activity was recorded via photocell-monitored light beams. The frogs were nocturnal, being nearly twice as active at night as during the day. The mean preferred temperature was 22.4°C, with no significant difference between night (22.5°C) and day (22.3°C), although the modal preferendum shifted from 24°C by day to 22°C at night, with a corresponding change in skewness. The range of voluntarily occupied temperatures was 14–32°C by day and 14–29°C at night. The median thermal preferendum was 22°C both day and night.     

Temperature adaptation and the contractile properties of live muscle fibres from teleost fish

Summary The contractile properties of swimming muscles have been investigated in marine teleosts from Antarctic (Trematomus lepidorhinus, Pseudochaenichthys georgianus), temperate (Pollachius virens, Limanda limanda, Agonis cataphractus, Callionymus lyra), and tropical (Abudefduf abdominalis, Thalassoma duperreyi) latitudes. Small bundles of fast twitch fibres were isolated from anterior myotomes and/or the pectoral fin adductor profundis muscle (m. add. p). Live fibre preparations were viable for several days at in vivo temperatures, but became progressively inexcitable at higher or lower temperatures. The stimulation frequency required to produce fused isometric tetani increased from 50 Hz in Antarctic species at 0°C to around 400 Hz in tropical species at 25°C. Maximum isometric tension (P_o) was produced at the normal body temperature (NBT) of each species (Antarctic, 0–2°C; North Sea and Atlantic, 8–10°C; Indo-West Pacific, 23–25°C). P₀ values at physiological temperatures (200–300 kN·m^–2) were similar for Antarctic, temperate, and tropical species. A temperature induced tension hysteresis was observed in muscle fibres from some species. Exposure to <0°C in Antarctic and <2°C in temperate fish resulted in the temporary depression of tension over the whole experimental range, an effect reversed by incubation at higher temperatures. At normal body temperatures the half-times for activation and relaxation of twitch and tetanic tension increased in the order Antarctic>temperate>tropical species. Relaxation was generally much slower at temperatures <10°C in fibres from tropical than temperate fish. Q₁₀ values for these parameters at NBTs were 1.3 2.1 for tropical species, 1.7–2.6 for temperate species, and 1.6–3.5 for Antarctic species. The forcevelocity (P-V) relationship was studied in selected species using iso-velocity releases and the data below 0.8 P₀ iteratively fitted to Hill's equation. The P-V relation at NBT was found to be significantly less curved in Antarctic than temperate species. The unloaded contraction velocity (V_max) of fibres was positively correlated with NBT increasing from about 1 muscle fibre length·s^–;1 in an Antarctic fish (Trematomus lepidorhinus) at 1°C to around 16 muscle fibre lengths·s^–1 in a tropical species (Thalassoma duperreyi) at 24°C. It is concluded that although muscle contraction in Antarctic fish shows adaptations for low temperature function, the degree of compensation achieved in shortening speed and twitch kinetics is relatively modest.Abbreviations ET environmental temperature - m. add. p major adductor profundis - m. add. s. major adductor superficialis - NBT normal body temperature - P ₀ maximum isometric tension - P-V force velocity - SR sarcoplasmic reticulum - T 1/2 a half activation time - T 1/2 r half relaxation time - V _max unloaded contraction     

Aspects of the thermal ecology of the rusty crayfish Orconectes rusticus (Girard)

Summary Orconectes rusticus currently is undergoing an explosive range expansion in the midwestern U.S.A., but information on the potentially important effects of water temperature on the species' biology is lacking. The thermal ecology of O. rusticus in southwestern Ohio, U.S.A., was examined by determining 1) the effects of four water temperatures (16, 20, 25, and 29°C) on survival and growth of juveniles, 2) the responses of juveniles and adults to a thermal gradient (7–27° C), and 3) the thermal tolerances (critical thermal maximum, CTMax, and critical thermal minimum, CTMin) of free-living, field-acclimatized juveniles and adults on a biweekly basis throughout the summer. Month-long growth experiments predicted maximum growth rates of juveniles at water temperatures between 26 and 28°C, but greatest survival between 20 and 22° C. Laboratory-acclimated (22° C) adults and field-acclimatized (2.5° C) juveniles both had an acute preferred temperature of 22° C. CTMaxs and CTMins of juveniles were 0.5–2.6° C higher than those of adults throughout the summer, suggesting that juveniles were exposed to water temperatures 1.5–6.8° C warmer than those of adults. Juvenile and adult O. rusticus prefer habitats where water temperatures favor maximum survival, but they usually are not found together in the same habitat; adults apparently displace the juveniles into warmer habitats. Warmer temperatures can decrease survival of juveniles but improve their growth rates, leading to enhanced fecundity and competitive ability. The past and future success of O. rusticus in expanding its range may depend, in part, on the species ability to adjust to new thermal environments occupied by other species of crayfish.     

Effect of temperature,hydrogen ion concentration and osmotic potential on oospore germination of fivePythium spp. isolated from pond water

Oospore germination occurred over a temperature ranging of 15–35°C forPythium coloratum, 10–35°C forP. diclinum, 15–30°C forP. dissotocum, 7–30°C forP. monospermum, and 10–30°C forP. pleroticum. Optimum temperature was 25°C for all species tested. In case of pH, oospore germination occurred over a range of 4.76–8.55 with an optimum of 6.40–7.40. The least germination occurred at pH 4.76 forP. coloratum, P. diclinum, P. monospermum andP. pleroticum, whileP. dissotocum germinated from pH 5.02. Oospores of the all tested pythia were able to germinate at –0.13 to –1.65 MPa and could not germinate at –3.40 MPa, with the highest germination rate at –0.27 to –0.47 MPa. The effect of temperature, pH and osmotic potential on oospore germination was discussed in relation to pollution of pond water.     

Behavioral response of the New England dog whelk,Nassarius trivittatus,to a temperature gradient

Thirty New England dog whelks (Mollusca: Gastropoda: Nassariidae), Nassarius trivittatus, were tested as a group for 3 days in a long linear gradient trough encompassing a thermal gradient ranging from 5°C to 45°C. The modal thermal preferendum of the snails lay between 30°C and 35°C. The lowest temperature interval voluntarily occupied by the snails was 15–20°C, the highest 35–40°C. W e believe this to be the first published study of temperature preference and avoidance behavior of gastropod molluscs.     

Geographical and experimental assessment of the distribution ofGracilaria species (Rhodophyta: Gigartinales) in relation to temperature

Tolerance and growth at temperatures from 0° to 36°C were investigated using 15 species and strains ofGracilaria Grev. isolated from tropical and temperate coasts of the Atlantic and eastern Pacific Oceans. All survived a minimum of 15°C and, with two exceptions, a maximum of 28°C. Only two species tolerated 34°C and none 36°C which was rapidly lethal. Isolates intolerant of temperatures less than 15°C were generally species known only from tropical waters, whereas species isolated from temperate waters tended to be eurythermal, and most seemed not to be restricted to cooler waters. Maximum growth of warm-water isolates tended to occur over a broad range of warmer temperatures, 20°C and higher, and usually extended to the upper limits of thermal tolerance. Isolates from temperate waters showed maximum growth at 20° or 15°C, and there was no appreciable growth of any of the isolates below 10°C. These experimental results are in accord with known distributional patterns ofGracilaria. There is a correlation between temperature and number of species, with most species reported from warm-water areas where the mean water temperature is 25°C or more. Where the 3-month mean minimum temperature is less than 20°C, there is a rapid decline in number of species. In the eastern Atlantic, the relationship is less obvious as few species have been reported from the warm-water region. This is quite likely the result of other environmental factors.NRCC No. 23817Paper presented at the Seaweed Biogeography Workshop of the International Working Group on Seaweed Biogeography, held from 3–7 April 1984 at the Department of Marine Biology, Rijksuniversiteit Groningen (The Netherlands). Convenor: C. van den Hoek.     

A comparison of the responses of tropical and temperate flies (Diptera: Sarcophagidae) to cold and heat stress

Summary Two flesh fly species from the tropical lowlands (Peckia abnormis and Sarcodexia sternodontis) were more susceptible to both cold-shock and heatshock injury than temperate flies (Sarcophaga crassipalpis and S. bullata) and a fly from a tropical high altitude (Blaesoxipha plinthopyga). A brief (2-h) exposure to 0°C elicits a protective response against subsequent cold injury at–10°C in the temperate flies and in B. plinthopyga but no such response was found in the flies from the tropical lowlands. However, both tropical and temperate flies could be protected against heat injury (45°C) by first exposing them to a mild heat shock (2 h at 40°C). The supercooling point is not a good indicator of cold tolerance: supercooling points of pupae were similar in all species, ranging from–18.9 to–23.0°C, and no differences were found between the tropical and temperate species. Among the temperate species, glycerol, the major cryoprotectant, can be elevated by short-term exposure to 0°C, but glycerol could not be detected in the tropical flies. Low-temperature (0°C) exposure also increased hemolymph osmolality of the temperate species, but no such increase was observed in the tropical lowland species. Adaptations to temperature stress thus differ in tropical and temperate flesh flies: while flies from both geographic areas share a mechanism for rapidly increasing heat tolerance, only the temperate flies appear capable of responding rapidly to cold stress. The presence of a heat shock response in species that lack the ability to rapidly respond to cold stress indicates that the biochemical and physiological bases for these two responses are likely to differ.     

Behavioural thermoregulation of the Andean toad (Bufo spinulosus) at high altitudes

Summary The body temperature of free-ranging Andean toadsBufo spinulosus was measured either directly or radiotelemetrically during two 15-day periods at 3200 m elevation in the Mantaro Valley, Central Perú. All toads attempted to maintain their diurnal sum of body temperature within a narrow range. Consequently thermoregulatory behaviour differed according to cloud cover and precipitation. If the sky was clear, toads emerged from their hiding place and exposed themselves to solar radiation during 3–5 h in the morning. Core temperature increased up to 15° C above the air temperature in shade and reached maximum values of about 32° C. At air temperatures (in sun) exceeding 29° C, toads maintained body temperatures below 32° C by evaporative cooling. Following heliothermic heating during the moring toads retreated to the shade, thereby decreasing body temperature below air temperature. Under overcast sky toads remained exposed during the whole day displaying body temperatures at or slightly above ambient levels. Quantitative models to predict the core temperature of toads under the different weather conditions demonstrated that the substrate temperature was the main energy source accounting for 64.6–77.9% of total variance whereas air temperature was of minor importance (1.5–4.4%). The unexplained variance was probably due to evaporative cooling. The volume of urine stored into the urinary bladder of toads varied diurnally; during basking in the morning hours most bladders contained large volumes of urine, whereas during the afternoon the bladders were mostly empty. The bladder contents probably serve as water reserves during basking when evaporative water loss was high. Toads preferred sites that provided shady hiding places as well as sun-exposed bare soil within a radius of 5 m. However, they frequently changed their centers of activity and moved to other sites in 20–70 m distance after periods of 2–5 days. The helio-and thigmothermic behaviour of the Andean toad permits the maintenance of high core temperature during morning which probably increases the digestion rate and accelerate growth. Evaporative cooling and preference of shady sites were employed to regulate body temperature below the morning levels in response to the constraints of water balance. Periodic changes between thigmothermic behaviour and locomotory activity during the night maintains body temperature above air temperature and prolongs the period of food uptake.Dedicated to Prof. Dr. H. Schneider on the occasion of his sixtieth birthday     

Behavioral thermoregulation by Ammocoete larvae of the sea lamprey (Petromyzon marinus) in an electronic shuttlebox

Ammocoete larvae of the sea lamprey Petromyzon marinus, a member of the primitive vertebrate class Agnatha, were tested for thermoregulatory behavior in an electronic shuttlebox (ichthyotron). The final preferendum derived from pooled data for 24 individually tested ammocoetes was characterized by a mean of 13.6 ± 0.17 (s.e.m.)°C, a mode and median of 140°C, and a range of voluntarily occupied temperatures from 10–19°C over a 3-day period.     

Interspecific variation for thermal dependence of glutathione reductase in sainfoin

Summary Understanding the biochemical and physiological consequences of species variation would expedite improvement in agronomically useful genotypes of sainfoin (Onobrychis spp.) Information on variation among sainfoin species is lacking on thermal dependence of glutathione reductase (B.C. 1.6.4.2.), which plays an important role in the protection of plants from both high and low temperature stresses by preventing harmful oxidation of enzymes and membranes. Our objective was to investigate the interspecific variation for thermal dependency of glutathione reductase in sainfoin. Large variation among species was found for: (i) the minimum apparent Km (0.4–2.5 M NADPH), (ii) the temperature at which the minimum apparent Km was observed (15°–5°C), and (iii) the thermal kinetic windows (2°–30°C width) over a 15°–45°C temperature gradient. In general, tetraploid species had narrower (17°C) thermal kinetic windows than did diploid species (30°C), with one exception among the diploids. Within the tetraploid species, the cultivars of O. viciifolia had a broader thermal kinetic window (7°C) than the plant introduction (PI 212241, >2 °C) itself.This work was supported by USDA Specific Cooperative Agreement No. 58-7MN1-8-143 from the Plant Stress and Water Conservation Unit, USDA-ARS, Lubbock, Texas. Joint contribution of Texas Tech University, Lubbock, Texas and the USDA-ARS. TTU Journal No. T-4-291     

Supercooling capacity of Eurasian and North American populations of parasitoids of the Russian wheat aphid, >Diuraphis noxia

Supercooling points were estimated for seven populations of >Aphelinus albipodus, five populations of >Aphelinus asychis, and four populations of >Diaeretiella rapae to assess whether their supercooling points were sufficiently low to provide the potential for overwintering survival in colder temperate climatic areas. Test individuals from all 16 of the parasitoid populations were collected originally from mummies of the Russian wheat aphid, >Diuraphis noxia. Mummies containing parasitoid pupae were maintained for 1 wk under three different temperature conditions (treatments): at room temperature (24.8 ± 0.2 °C), 1 wk at 0 °C, and 1 wk –5 °C, and the supercooling points across treatments, and within and among species were compared. Statistical differences in supercooling points were found among populations of >A. albipodus for each treatment, and for >A. asychis when maintained for 1 wk at room temperature. No differences in supercooling points were found among populations of >D. rapae mummies maintained under the three temperature treatments. The lowest supercooling points obtained for the three parasitoid species maintained at room temperature were the >A. albipodus population from Montana (–31.68 °C), the >A. asychis population from Greece (–32.04 °C), and the >D. rapaepopulation from the Caucasus (–33.12 °C). Preconditioning the parasitoid mummies to cold had no effect on the supercooling points for >A. albipodus, and in some cases unexpectedly increased the supercooling points for >A. asychisand >D. rapae. In comparing the overall mean supercooling points of the three parasitoid species, no differences were found within species (among temperature treatments), nor among species (within temperature treatments). It was concluded that observed differences in supercooling points of only a few degrees Centigrade among parasitoid populations and species would not be expected to cause differences in their overwintering success, especially given the expected variability in temperatures within and among overwintering sites.     

Autecological investigations on marine diatoms 6:Rhizosolenia robusta Norman,Rhizosolenia imbricata Brightwell andRhizosolenia shrubsolei Cleve

The warm oligo-eurytherm diatomsRhizosolenia robusta Norman andRhizosolenia imbricata Brightwell were cultured to determine the temperature range for the best competitive position by growth. Comparison of their generation times with those of other diatoms indicate thatR. robusta reaches this position around 20 °C andR. imbricata above 25 °C. The temperature ranges for growth were 12 °C up to 28 °C forR. robusta and 12 °C to above 30 °C forR. imbricata. The use of both species as indicator species for warm water currents is discussed on account of their lower temperature limit. The cold oligo-eurytherm diatomRhizosolenia shrubsolei had a temperature range for growth of below –1.0 °C to 25 °C. Our experimental results demonstrate thatR. imbricata andR. shrubsolei can be considered separate species.     

The effects of acclimation and rearing conditions on the response of tropical and temperate populations ofDrosophila melanogaster andD. simulans to a temperature gradient (Diptera: Drosophilidae)

The effects of rearing and acclimation on the response of adultDrosophila to temperature were investigated in a gradient.D. melanogaster flies preferred a higher mean temperature and were distributed over a wider range of temperatures thanD. simulans flies. Acclimating adults at different temperatures for a week did not influence the response of either species. Adults reared at 28°C as immatures had a lower mean preference than those reared at cooler temperatures, suggesting that flies compensated for the effects of rearing conditions. Adults from tropical and temperate populations ofD. melanogaster andD. simulans did not differ in the mean temperature they preferred in a gradient, suggesting little genetic divergence for this trait within species. The species differences and environmental responses may be related to changes in optimal physiological conditions for the flies.     

Rheological properties of polysaccharides produced by a Zoogloea sp.

A newly isolated marine bacterium, identified as Zoogloea sp., produced two different polysaccharides: one was water-soluble and the other was cell-bound. Both had non-Newtonian, pseudoplastic fluid behaviour and the solutions had low activation energies. The solutions of these polysaccharides showed rheological behaviour over a wide range of pH (2–12) and temperature (20–80 °C), and compatibility with NaCl.