Influence of yeast quality on performance of gnotobiotically grown Artemia

Using axenically grown Artemia, a model system was developed to evaluate the effect of bacteria on the survival and development of this crustacean. Two strains of baker's yeast (Saccharomyces cerevisiae) were used in all experiments as feed for Artemia: a wild-type strain and its mnn9 mutant, defective in the synthesis of mannoproteins in the outer cell wall. The genetic background, yeast growth phase and growth medium appeared to be important parameters determining the quality of yeast cells as feed for Artemia. A strong positive correlation between Artemia performance and the yeast cell wall chitin and glucan content was obtained, while the mannoprotein content was negatively correlated. Mnn9 yeast cells grown till exponential phase in minimal medium proved to be excellent feed for Artemia, yielding an average 95% survival and 4-mm growth after 6 days at 28 °C, which is comparable to the best results obtained with algal feed. The standard growth test yields highly reproducible results and can become an excellent tool to study the mode of action of bacteria. Furthermore, yeast cell viability and the method used to kill/sterilize the cells are important parameters influencing nauplii performance.     

Thermal stability of Artemia HGPRT: effect of substrates on inactivation kinetics

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT, E.C. 2.4.2.8) from Artemia cysts exhibits maximum activity at 70°C. Its thermal stability has been examined following enzymatic activity as a function of temperature. Cold-induced renaturation experiments of samples heated at increasing temperatures showed that reversibility of thermal inactivation depends on the incubation time and final temperature. Prolonged incubation of the thermoinactivated enzyme at 0°C did not afford any further increase of the catalytic activity at 37°C. The complex substrate PRPP:Mg protects HGPRT from thermal inactivation. However, incubations with hypoxanthine rendered a less thermostable enzyme at any temperature tested. The irreversible inactivation of HGPRT proceeds in two exponential steps. The analysis of the apparent rate constants for the fast and the slow phases, λ₁ and λ₂ as per the Lumry and Eyring model suggests the existence of more than three states in the thermal denaturation pathway of the free enzyme. In the presence of PRPP:Mg the irreversible process follows a single exponential and proceeds very slowly below 70°C. PRPP:Mg also protects the enzyme from inactivation by NEM and pCMB, suggesting that -SH groups may be in the vicinity of the active site     

Temperature and acclimation effects on salinity preferences of post-larvae of the giant Malaysian prawn, Macrobrachium rosenbergii (de Man)

The movement of individual post-larvae of Macrobrachium rosenbergii (de Man) among horizontally-juxtaposed salinity layers of 0, 7, 14, 21, and 28%. was observed during 135-min test periods. The time that post-larvae spent in each salinity was measured at 20, 27, and 34 °C with prawns acclimated to 0, 14, and 28%. salinity.

The young prawns generally moved readily into salinities lower than the acclimation salinity at 27°C, and less frequently into higher salinities. At both 27 and 34°C, post-larvae tended to spend more time in lower salinities than in the salinities to which they were acclimated. Post-larvae acclimated to fresh water rarely reentered saline waters.

Temperature effects on activity resulted in little movement of the prawns at 20°C. High temperature shortened the range of salinities post-larvae occupied for significant periods of time.     

Temperature as a factor regulating growth and toxin content in the dinoflagellate Alexandrium catenella

Controlled laboratory culture of Alexandrium catenella was used to determine the effects of a range of temperatures between 10 and 16 °C on the growth and saxitoxin content of this dinoflagellate, using strain ACC02 isolated from seawater at Aysen, XI Region, Southern Chile. Cell cultures were made using L1 culture medium at 30‰ salinity, and a photon flux density of 59.53 μmol m² s⁻¹. The results showed that the duration of the exponential growth phase was determined by the experimental temperature, with maximum cell concentrations obtained at 12 °C; significantly lower cell concentrations and growth rates were obtained at 16 °C. Cell dry weight and chlorophyll a values followed cell growth trends. The toxicity of A. catenella was variable at all the experimental temperatures, with a tendency towards having an inverse relation to temperature, with the highest values occurring at 10 °C and the lowest at 16 °C. The optimal range of temperature for the growth of the Chilean strain of A. catenella differed from rates reported for this species isolated at other latitudes, and was correlated with natural temperature conditions predominant in the environment from which it was isolated. The inverse relation of toxicity with temperature in the laboratory was broadly reflected in observations on the toxicity of this dinoflagellate in the field, and coincided with results from the literature.     

Determination of the maximum and minimum lethal temperatures (LT50) for Loxosceles intermedia Mello-Leitão, 1934 and L. laeta (Nicolet, 1849) (Araneae, Sicariidae)

In this study, the maximum and minimum lethal temperatures (LT₅₀) of L. intermedia and L. laeta were determined in two treatments: gradual heating (25–50°C) and cooling (25°C to −5°C), and 1 h at a constant temperature. In gradual temperatures change, L. intermedia mortality started at 40°C and the LT₅₀ was 42°C; for L. laeta, mortality began at 35°C and the LT₅₀ was 40°C. At low temperatures, mortality was registered only at −5°C for both species. In the constant temperature L. intermedia showed a maximum LT₅₀ at 35°C and L. laeta at 32°C; the minimum LT for both species was −7°C.     

Alexandrium catenella and Alexandrium minutum blooms in the Mediterranean Sea: Toward the identification of ecological niches

Annual recurrent blooms of the toxic dinoflagellates Alexandrium catenella and Alexandrium minutum were detected from 2000 to 2003 in harbours along the Catalan coast. The interrelation study between the occurrence of the blooms and specific external conditions at the study sites demonstrated that different factors are required for the bloom of each Alexandrium species. Concentrations higher than 10⁵ cells l⁻¹ of A. catenella were only detected in Tarragona harbour. These blooms were associated with water surface temperature between 21 and 25 °C and salinities of around 34 psu or higher than 37 psu. A. minutum appeared widely spread along the Catalan coast, though the most intensive and recurrent blooms of this species were observed in Arenys de Mar harbour. Concentrations of millions of cells per litre of A. minutum were associated with water temperatures below 14 °C and salinities of around 34–36 psu. A. minutum cell densities showed a positive significant correlation with NO₃ but a negative correlation with NH₄. On the other hand, A. catenella blooms dominated when both NO₃ and NH₄ levels were high. The prevailing inorganic nitrogen form (NO₃ vs. NH₄) could explain why these two species rarely coincide in the same harbours. Accumulation of cysts in the sediment was found to be an important potential factor for the recurrence of these species. The 4.3 × 10³ A. catenella cysts cm⁻³ of wet sediment in Tarragona harbour and the 3.02 × 10³ A. minutum cysts cm⁻³ of wet sediment in Vilanova harbour were the highest concentrations observed from the cyst study. Confined waters such as harbours play an important role as reservoirs for the accumulation of cysts and vegetative cells, which contributes to the expansion of these dinoflagellates in the region. However, the particular environmental conditions are also decisive factors of bloom intensity.     

The influence of salinity on certain aspects of the biology of Bulinus (Physopsis) africanus

The hatchability of eggs and the fecundity and survival of adult Bulinus (Physopsis) africanus was investigated in different salinities. Experimental results revealed egg masses and hatchlings to be considerably more sensitive to salinity than the adult snails. Egg-laying was recorded in salinities 4·5 ‰ and further increases in salinity resulted in a progressive reduction in the hatching success up to a lethal concentration of 5·25 ‰ Survival of these hatchings was adversely affected by salinities as low as 1·0 ‰ and a salinity of 4·5 ‰ was lethal within 6 days. In contrast, adult survival was unaffected in salinities < 3·5 ‰ while further increases in salinity resulted in significant reductions in survival up to a lethal salinity of 8·7 ‰, which caused 100% mortality within 24 h. The survival of B. africanus infected with Schistosoma haematobium and Schistosoma mattheei was lower in the different salinities and control than that of their uninfected counterparts.     

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.

Loss of Symbiodinium from bleached soft corals Sarcophyton ehrenbergi, Sinularia sp. and Xenia sp.

The deleterious effects of temperature-induced coral bleaching, a process by which corals lose their endosymbiotic algae (zooxanthellae; genus Symbiodinium) primarily at temperatures above mean yearly maximums, has not been well described for alcyonacean soft corals (Coelenterata, Octocorallia). The study of Symbiodinium cells lost from Sarcophyton ehrenbergi, Sinularia sp., and Xenia sp., which have not been compared in bleaching studies, indicate that the soft coral S. ehrenbergi released the greatest number of symbiont cells, however, it was less susceptible to heat stress surviving temperatures of 34 °C for >39 h. Sinularia sp. showed intermediate levels of bleaching tolerance to elevated temperatures, surviving prolonged exposures at 32 °C, but dying within 24 h at 34 °C. Xenia sp., however, was the most vulnerable to high heat stress maximally releasing Symbiodinium at temperatures ≤30 °C. This evidence indicates that Xenia sp. is even more susceptible to elevated temperatures than Acropora spp., previously reported to be the most vulnerable coral species to elevated temperature-induced bleaching.

Molecular analysis showed that the more resistant soft coral species (S. ehrenbergi) had the same type of Symbiodinium (clade C) as less resistant soft corals (Xenia sp.). In comparison to scleractinian corals collected from the same region that show similar bleaching resistance to high temperatures (e.g. Porities solida—more robust; Favites complanata—moderate resistance; Acropora hyacinthus—less robust), all scleractinian corals were symbiotic with Symbiodinium from clade C. A. hyacinthus, however, was found to possess multiple symbionts (clades B and C), and this represents a first report of Clade B in any Acropora species.     

Effects of temperature on tilt evoked swimming in the crabs Carcinus and Macropipus

1. 1.|Integrated muscle activity, total number of limb beats and the maximum instantaneous limb beat frequency were measured in crabs during a standardized tilt regime at a series of different water temperatures between 10 and 25°C.

2. 2.|Total integrated activity and total number of limb beats showed a general increase for a decrease in temperature in all groups. Frequency of limb beat was always higher for Macropipus depurator than for Carcinus maenas, with M. depurator showing an increase and C. maenas a decrease in frequencies at extreme temperatures.

3. 3.|The temperature of acclimation of C. maenas affected the response of the crab in all parameters studied while all the results can be related to the size and normal environmental temperature range of the two species studied.

The effect of temperature on caecal fermentation processes in a poikilothermic mammal, Heterocephalus glaber

1. 1.|The effect of temperature on caecal function was examined in the naked mole-rat Heterocephalus glaber, a poikilothermic mammal, which consumes a high proportion of fibre in its natural diet.

2. 2.|The temperature of optimal caecal function was determined from fermentation data measure at three specifically chosen temperatures (28, 33 and 40°C).

3. 3.|There was no significant difference between gas production at 33 and 40°C, however, gas production was significantly lower at 28°C.

4. 4.|The relative proportions of the gases produced were markedly different at 33 and 40°C (P ≤ 0.01). More methane and hydrogen were produced at 33°C than at 40°C.

5. 5.|These data suggest that microbial organisms within the caecum were active and functioning more effectively at 33°C (the preferred body temperature of the naked mole-rat) than at the other two temperatures.

Geographic variation in field body temperature of sceloporus lizards

1. Using data from the literature, I assessed how broad climatic patterns affected field body temperatures (T_b’s) of lizards in the genus Sceloporus.

2. Sceloporus at temperate latitudes had mean T_b’s of 35°C throughout their elevational range. This pattern is associated with “tropical” temperatures that extend into high north latitudes during the summer and the relatively low elevations occupied by the lizards.

3. At tropical latitudes, mean T_b declined from 35°C at low elevations to 31°C at high elevations. This pattern is associated with low seasonal variation in temperature at tropical latitudes and the relatively high elevations occupied by the lizards.     

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.

Influence of salinity and temperature on the germination of Ruppia maritima L. from the North Atlantic and Gulf of Mexico

Seeds from the seagrass Ruppia maritima L. collected in North Carolina and Florida were tested for their germination at 17, 23 and 29°C and at 0, 15 and 30%. salinities. Percent germination was significantly higher for seeds from North Carolina and the seeds from Florida did not germinate in 30%. salinity. The northern population also had a more rapid rate of germination. These germination patterns suggest that ecotypic differentiation in germination occurred between the two populations in relation to salinity but not temperature.     

Comparative aspects of the thermal biology of the short-tailed gerbil, Desmodillus auricularis, and the bushveld gerbil, Tatera leucogaster

1. 1. The response of oxygen consumption (VO₂), thermal conductance (C_d and C_min, body temperature (T_b), and evaporative water loss (EWL) of Tatera leucogaster and Desmodillus auricularis were measured over the range of ambient temperatures (T_a) from 5–35°C.

2. 2. Basal metabolic rate (BMR) of T. leucogaster was 0.841 ± 0.049 ml O₂ g⁻¹ h⁻¹ and lower than predicted, while that of D. auricularis was similar to the expected value (1.220 ± 0.058 ml O₂ g⁻¹ h⁻¹). D. auricularis had a high, narrow thermoneutral zone (TNZ) typical of nocturnal, xerophilic, burrowing rodents.

3. 3. D. auricularis and T. leucogaster regulated T_b over the range T_a = 5–35°C and kept EWL and dry thermal conductance at a minimum below the TNZ. However, the EWL of T. leucogaster increased rapidly above T_a = 30°C.

4. 4. After comparison with data from other species, it was concluded that there is an optimum size for xeric, nocturnal, burrowing rodents.

Respiration and nitrogen excretion of Polinices alderi (Forbes) and Polinices catena (da Costa) (Gastropoda : Naticidae)

Measurements were made of oxygen consumption and NH₃-N excretion, at different temperatures, for two species of gastropod molluscs, Polinices alderi (Forbes) and P. catena (da Costa), preying on bivalve molluscs. Previous observations, for P. alderi, that the rate of oxygen consumption is influenced by diet were confirmed. The effect of temperature on the rates of respiration and excretion was compared for the two species. Oxygen consumption was temperature dependent, with Q₁₀ values of ≈2, in the temperature range 10–20°C, for both species. NH₃-N excretion was relatively insensitive to temperature over the same range. The ratio of oxygen consumed to nitrogen excreted (O:N ratio) was relatively independent of size for both species, but was influenced by diet.     

The effects of constant and changing tempertures on the development of eggs of the freshwater snail Lymnaea auricularia (L.)

The rate of development of Lymnaea auricularia eggs was studied at various constant temperatures between 10° and 36°C. Development was accelerated as the temperature increased and at 36°C the eggs failed to develop. Spring eggs showed differences in their rate of development when compared with summer eggs when measured at similar tempertures.

Both spring and summer eggs were more than 90% fertile. Hatching success was high at temperatures between 10° and 30° (100%–82/9%); while at 34°C it was reduced to 60.6% for spring eggs. It was above 87% at temperatures between 10° and 34°C but it dropped to 62.3% at 36°C for summer eggs.

In one regularly changing temperature experiment a significant acceleration (P < .05) was found. In two others there was no significant difference beween predicted and observed egg durations. In one suddenly changing temperature regime (1 day at 20°, 1 day at 30° and so on) a huge retardation of development was found. In the other suddenly changing experiment (1 day at 15°, 1 day at 25°) no significant difference was found.

The exposure of eggs to extreme temperature (4°C, freezing and 4°C caused a retardation in the race of subsequent development of eggs at 25°C.     

Behavioral thermoregulation of Bulla gouldiana (Gastropoda: Opisthobranchia: Cephalaspidea)

1. 1. The preferred temperature of Bulla gouldiana is 26.7–28.7°C.

2. 2. In constant scotophase, photophase, and light and dark photoperiod the organisms do not have a diel cycle of thermoregulation.

3. 3. It takes the animal 6–16 h to reach the preferred temperature.

4. 4. The lowest and highest temperatures visited were 11 and 33°C.

5. 5. Spawning of the species occurred in the thermal gradient between 27 and 28.5°C.

     

Metabolism and thermoregulation in Maximowiczi's voles (Microtus maximowiczii) and Djungarian hamsters (Phodopus campbelli)

1 Metabolic rates (Vo₂), body temperature (T_b), and thermal conductance (C) were first determined in newly captured Maximowiczi's voles (Microtus maximowiczii) and Djungarian hamsters (Phodopus campbelli) from the Inner Mongolian grasslands at a temperature range from 5 to 35 °C.

2 The thermal neutral zone (TNZ) was between 25 and 32.5 °C for Maximowiczi's voles and between 25 and 30 °C for Djungarian hamsters. Mean T_b was 37.0±0.1 °C for voles and 36.2±0.1 °C for hamsters. Minimum thermal conductance was 0.172±0.004 ml O₂/g h °C for voles and 0.148±0.003 ml O₂/g h °C for hamsters.

3 The mean resting metabolic rate within TNZ was 2.21±0.05 ml O₂/g h in voles and 2.01±0.07 ml O₂/g h in hamsters. Nonshivering thermogenesis was 5.36±0.30 ml O₂/g h for voles and 6.30±0.18 ml O₂/g h for hamsters.

4 All these thermal physiological properties are adaptive for each species and are shaped by both macroenvironmental and microenvironmental conditions, food habits, phylogeny and other factors.

Temperature acclimation of axonal functions in the crayfish Astacus astacus L.

1. 1.|Crayfish (Astacus astacus L.) were acclimated for 1–3 weeks at 5 and 20°C. The effects of temperature on the functions of the unicellular medial giant axon were studied.

2. 2.|The resting membrane potential of the giant axon increased slightly with the experimental temperature from 2 to 32°C. The temperature dependence of the resting membrane potential could be described by two lines, which intersected at about 12°C in cold-acclimated crayfish and at about 16°C in the warm-acclimated.

3. 3.|The amplitude of the action potential was stable at temperatures from 4 to 26°C. It decreased at temperatures above 26°C in both acclimation groups.

4. 4.|The duration of the falling phase of action potential was highly temperature dependent at low temperatures. A break in the slope of the dependence was found at about 14°C in cold-acclimated crayfish and at about 17°C in the warm-acclimated.