Incorporation of ω6 polyunsaturated fatty acids into phospholipids of the crab Carcinus maenas

The incorporation in vivo of ¹⁴C-18:2 ω6 and ³H-20:4 ω6 fatty acids in phospholipids isolated from gills, hepatopancreas and hemolymph of the crab Carcinus maenas was analysed. PC was the most heavily labelled phospholipid from these ω6-unsaturated fatty acids and appeared to play an important part in the phospholipids metabolism in Crustaceans. The pathway of fatty acids synthesis in phospholipids of C. maenas seems to be similar to those described for mammals. It is at the level of tissue Pl of C. maenas that the renewal of the 20:4 ω6 fatty acid is the most important. It is suggested that the rapid reorganization of phospholipid molecular species composition in the crab is checked by deacylation—reacylation cycle.     

Temperature and growth in Carcinus maenas L. (Decapoda: Portunidae) larvae reared in the laboratory from hatching through metamorphosis

Larvae of Carcinus maenas L. were reared in the laboratory from hatching through metamorphosis at 9, 12, and 18°C. Dry weight (DW) and elemental contents of carbon (C), nitrogen (N), and hydrogen (H) were analysed at short intervals through successive larval moulting cycles (four zoea-stages, megalopa), and newly metamorphosed crabs. C. maenas larvae grew significantly during all instars, at all temperatures tested. Biomass (DW, C, N, H) and energy (Joule) slightly declined shortly before ecdysis in zoea stages. This terminal decrease was more distinct in the megalopa stage, where ≈39 and 83% of the maximum energy attained, was lost at 12 and 18°C, respectively. Changes of biomass and energy in successive moult cycles showed best fits to quadratic equations, whereas their maximum in successive larval instars formed exponential sequences with time. Due to parabolic growth curves, biomass and energy accumulation within single instars were discussed as maximum (MG) and effective growth (EG), considering gain both at times of maximum biomass, and shortly before ecdysis. Metamorphosing larvae achieved EG with 1137% (DW), 1195% (C), 1108% (N), 1395% (H), 1339% (Joule) at 12°C, and 1140% (DW), 1099% (C), 1133% (N), 1225% (H), 1107% (Joule) at 18°C, relative to newly hatched zoea-1. Ash content and inorganic C in newly hatched zoea-1, were 29.4% and 5.5% ash, respectively. The stoichiometric C H N method of Gnaiger & Bitterlich was used to assess protein, lipid, and carbohydrate compositions. Obviously proteins formed the major part of larval biomass (>50% DW). C: N ratios indicate that more lipid than protein was built up shortly after moulting, but relatively more protein was subsequently accumulated. Temperature effects on larval growth (MG, EG), growth rates (GR), and gross growth efficiencies (K₁) were discussed. C. maenas zoea stages accumulated energy and biomass with higher efficiencies at 18 than at 12°C. Megalopa growth seemed to be limited at 18°C, showing lower K₁ values than at 12°C. N was accumulated with higher efficiencies than C in all larval stages. Characteristic variations in larval K₁ values between premoult and ecdysis were discussed. Cumulative gross growth efficiencies (MG-related) were calculated as ≈11 and 10%, at 12 and 18°C, respectively.     

Host-parasite relation between the shore crab Carcinus maenas and Sacculina carcini (Rhizocephala): Identification and characterization of a specific fraction correlated with parasitism

Two protein fractions have been revealed in the blood of infested crabs. These fractions do not occur in healthy animals. Their relations are analyzed. Both present the same electrophoretic mobility and have common antigenic determinants. They are characterized in relation to the major serologic components of the hemolymph.     

Effect of environmental temperature on biosynthesis of liver phosphatidyl-choline in the trout (Salmo gairdnerii)

1. 1.The changes in fatty acid composition of trout liver phosphatidyl-choline, when the environmental temperature was increased, resulted in modifications in the amounts of the different molecular species.

2. 2.In vivo, incorporation of ³²P occurred more rapidly in the molecular species with high degree of unsaturation.Temperature acclimation did not modify the relative proportions of label shown in the five subfractions.

3. 3.In vitro incorporation of ¹⁴C-methyl-choline also occurred more rapidly in the most unsaturated molecular species. However, when the incubation temperature was raised, the proportion of label decreased in the unsaturated fractions.

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.

Adaptation to salinity by fish. Macromolecular changes in mitochondria and microsomes of the gill

Mitochondria isolated from the gill tissues of the fishSarothredon mossambica were analysed for their macromolecular content, following transfer from freshwater to media of higher salinity. The results suggest a breakdown of mitochondria during the initial phases of the stress and a regeneration during continued exposure. Also all the synthetic machineries, in general, seem to be triggered in gill tissue during continuous exposure to hyperosmotic media.     

Temperature-induced changes in lipid composition and transition temperature of flight muscle mitochondria of Schistocerca gregaria

The lipid composition of flight muscle mitochondria was determined in adult male $\text{Schistocerca gregaria}$ acclimated for 30 days at 31°C and 45°C respectively. Locusts held at 31°C showed lower levels of phosphatidylcholine and higher levels of phosphatidylethanolamine than the 45°C-acclimated insects. A trend towards an increased cholesterol:phospholipid ratio was also observed at the higher temperature. Wide angle X-ray diffraction procedures indicated a difference of 5°C in the lipid phase transition temperatures of mitochondrial preparations derived from the two groups of insects with the 45°C-acclimated samples demonstrating the higher transition temperature.     

Temperature-induced changes in lipid composition and transition temperature of flight muscle mitochondria of

The lipid composition of flight muscle mitochondria was determined in adult male acclimated for 30 days at 31°C and 45°C respectively. Locusts held at 31°C showed lower levels of phosphatidylcholine and higher levels of phosphatidylethanolamine than the 45°C-acclimated insects. A trend towards an increased cholesterol:phospholipid ratio was also observed at the higher temperature. Wide angle X-ray diffraction procedures indicated a difference of 5°C in the lipid phase transition temperatures of mitochondrial preparations derived from the two groups of insects with the 45°C-acclimated samples demonstrating the higher transition temperature.     

Inactivation of complex I of the respiratory chain of maize mitochondria incubated in vitro by elevated temperature

The functional stability of the ‘external’ NADH dehydrogenase and complexes I–IV of the respiratory chain of maize mitochondria was studied during mitochondria incubation in vitro at elevated temperatures. The increase in the incubation temperature from 0°C to 37°C significantly changed the stability of the respiratory chain. At 27°C and higher, the rate of oxidation of NAD-depended substrates decreased drastically, which is related to inactivation of complex I. Complexes II, III and IV of the respiratory chain and the ‘external’ NADH dehydrogenase were functionally stable at elevated temperatures. Moreover, the possibility of electron transport during oxidation of NAD-dependent substrates, in particular malate, bypasses complex I using rotenon insensitive NADH dehydrogenase.     

Effect of short-and long-term exposure to low environmental temperature on brain regional GABA metabolism

Single exposure of adult male rats to low environmental temperature (LET, 12 ± 0.5°C) for 2 h significantly increased the hypothalamic and striatal GABA levels without affecting those in other regions of brain. The activity of glutamate decarboxylase (GAD) was elevated in hypothalamus (H) and corpus striatum (CS) under these conditions. GABA accumulation rate (measured with ethanolamine-O-sulfate, an inhibitor of GABA-transaminase) was also increased in both H and CS of rats exposed to LET for 2 h. Unlike after a single exposure, the repeated exposure (2 h/day) for 7, 15, and 30 onsecutive days did not change the hypothalamic GABA metabolism. No change in GABA metabolism was observed in CS when rats were repeatedly exposed to LET for 7 consecutive days. Prolongation of repeated exposure to LET (2 h/day) for 15 and 30 consecutive days decreased the striatal GABA level and increased the activity of GABA-transaminase, although GAD activity was not altered under these conditions. These results suggest that single exposure to LET accelerates GABA synthesis and may reduce the GABAergic activity in both H and CS; whereas repeated exposure to LET for 15 or 30 consecutive days enhances GABAergic activity with the stimulation of GABA utilization only in CS without affecting its synthesizing process. Thus, it may be suggested that the hypothalamic and striatal GABA system may play a characteristic role in response to short-and long-term exposure to LET.     

Effects of reduced salinities on development and bioenergetics of early larval shore crab, Carcinus maenas

The shore crab, Carcinus maenas L. (Portunidae), is a coastal and estuarine species, which can live and reproduce under brackish water conditions; freshly hatched larvae have been observed in the field at salinities below 15‰. In the present laboratory study, the tolerance of hypo-osmotic stress was experimentally investigated in early larvae of a marine (North Sea) population of C. maenas reared at four different salinities (15, 20, 25, 32‰). Two and 4 days after hatching, the Zoea I larvae were moult-staged microscopically, and their rates of respiration and growth (changes in dry weight, W, carbon, C, nitrogen, N, and hydrogen, H) were measured. Survival and development were monitored until the megalopa was reached: 15‰ did not allow for development beyond the first zoeal stage, while metamorphosis to the megalopa was reached at salinities ≥20‰. At 20‰, development was significantly delayed and mortality enhanced as compared with 25 and 32‰. Rates of growth and respiration decreased during exposure to reduced salinities ≤25‰. Hence, the suppression of growth could not be explained as a consequence of enhanced metabolic losses per larva. Instead, a partial C budget indicates that the Zoea I larvae suffered from decreased capabilities of assimilating ingested and subsequently converting assimilated matter to tissue growth. Net growth efficiency (K₂, C-based) was at 25 and 32‰ initially high (>60% during the postmoult and intermoult stages of the Zoea I moult cycle), but decreased during the later stages (down to ≤30% in premoult). An inverse pattern of C partitioning was observed at ≤20‰, with initially low K₂ values (≤21% during the first 2 days of the moult cycle), and a later increase (up to ≥46% in premoult). Thus, larval growth was initially suppressed under conditions of reduced salinity, but this was later (during premoult) partially compensated for by an increase in C assimilation and K₂. Our observations indicate that Zoea I shore crab larvae react during the late stages of their moulting cycle less sensitively against reduced salinities than during postmoult and intermoult. This suggests that the transition between moult cycle stages C and D₀ may be a critical point for effects of hypo-osmotic stress, similarly as already known in relation to effects of nutritional stress. Negative effects were found also when freshly hatched Zoea I shore crab larvae were exposed only transitorily (for 24–72 h) to 20‰, with significantly lower rates of survival, development, growth, respiration, and K₂. These effects increased with increasing duration of initial exposure to reduced salinity.     

Effect of ethanol on cholesterol and phospholipid composition of HeLa cells

Chronic exposure of animals to ethanol leads to changes in membrane lipid composition which may be related to the development of tolerance and physical dependence. The object of the present study was to investigate this phenomenon at a cellular level. HeLa cells were grown in the presence of ethanol (86 mM) for periods of up to 9 days. Both the cholesterol and phospholipid concentration of these cells increased during this period but the cholesterol:phospholipid ratio remained unchanged. Among the phospholipid classes phosphatidic acid decreased while phosphatidylethanolamine, phosphatidylcholine and phosphatidylserine increased rapidly, returning toward control values by 9 days. Significant decreases were observed in saturated (14:0, 16:0) and monoenoic (16:1, 18:1) fatty acids while the major polyenoic fatty acid (20:4) increased. It is concluded that cultured mammalian cells represent a useful model for investigation of the direct effects of ethanol on membrane lipid metabolism.     

Patterns of morphological and genetic variability in UK populations of the shore crab, Carcinus maenas Linnaeus, 1758 (Crustacea: Decapoda: Brachyura)

Previous research has identified extensive inter-population variability in the morphology of the shore crab (Carcinus maenas L.). To determine the source of this variation (genetic or environmental), morphological and genetic data were analysed from crabs collected from eight sites around the coast of the UK. Ten morphometric traits were measured from over 800 crabs and the degree of morphological similarity among sites was calculated using multivariate techniques. Allozyme electrophoresis was used to investigate patterns of genetic similarity. Extensive morphological variability was detected: eight out of the ten morphometric traits analysed were useful when discriminating between crabs from each site. Discriminant function analysis revealed that over 35% of individuals could be classified to their site of origin on the basis of their morphology. In contrast, the allozyme analysis revealed low levels of genetic variability, both within the meta-population and among the crab population at each site. Pairwise comparisons revealed a moderate correlation between the degree of morphological and genetic similarity of crabs at each site, which suggests that the observed phenotypic variability has a genetic component. However, only around 20% of the phenotypic variability detected was associated with the patterns of genetic similarity. This means that patterns of morphological variability in this species are largely determined by the local environmental conditions: local factors could have a within-generation selective influence on mean trait values or C. maenas may exhibit phenotypic plasticity.     

Effect of Cobalamin Deficiency on the Biosynthesis of Phosphatidylcholine in Euglena gracilis

Euglena gracilis requires cobalamin (Cbl) as an essential growth factor. Phosphatidylcholine (PC) synthesis was greatly reduced by Cbl deficiency. Rapid cell division occurred after Cbl was replenished, and PC was actively synthesized during the cell divisions. When the deficient cells were given methionine (a precursor for the choline moiety), active synthesis of PC occurred even without the Cbl supplement, although cell division was not induced. As methionine synthase in Euglena requires methylcobalamin as a coenzyme, decrease in methionine synthesis may account for reduced PC synthesis under Cbl-deficient conditions. Phosphatidyleth-anolamine and phosphatidylserine synthesis were also suppressed, commensurate with decrease of PC synthesis, under Cbl deficiency, even though Cbl is not thought to participate in their synthesis. In contrast, a lot of triglyceride and wax ester accumulated in Cbl-deficient cells. Moreover, Cbl depletion altered fatty acid composition, notably due to increased proportion of odd-numbered fatty acids     

Effect of experimentally induced thyrotoxicosis on oxidative energy metabolism in rat heart mitochondria

Treatment of rats with T₃ resulted in a significant decrease in body weight, while the heart weight increased. T₄ treatment had less marked effect on body weights but resulted in decreased heart weights. Serum T₄ levels decreased significantly with simultaneous increase of T₃ level following T₃ treatment, whereas with T₄ treatment, levels of both T₄ and T₃ increased in the serum. Low doses of T₃ (0.5 μg ) caused decrease in mitochondrial protein content while high dose of T₄ (1 μg), caused significant increase in mitochondrial mass. The state 3 respiration rates were significantly depressed following T₃ and T₄ treatments, in a substrate specific manner with the effects being more pronounced with T₃; these responses with T₄ were dose-dependent for succinate and ascorbate + N,N,N′,N′-tetramethyl-p-phenylenedíamme. State 4 respiration rates also exhibited similar corresponding changes. ADP/O ratios were not changed but ADP-phosphorylation rates were decreased significantly particularly so with the T₃-treated animals. Treatment with T₃ also resulted in lowering of intramitochondrial cytochrome contents. Similar effects were seen also with higher doses of T₄. The results thus indicate that T_3- and T_4- thyrotoxicosis results in impaired energy metabolism in heart mitochondria.     

The effect of environmental temperature on olfactory perception in Drosophila melanogaster

Olfaction provides chemical information to an animal about its environment. When environmental conditions change, individuals should be able to adequately maintain function. Temperature may influence olfaction in a double manner, as it modifies the concentrations of gaseous compounds and affects biological processes. Here, we address acclimatization to environmental temperature in the olfactory system of Drosophila melanogaster using heat and cold treatments. Because the consequences of temperature shifts persist for some time after the treatment's end, comparison of olfactory behaviors at the same temperature in treated and untreated flies allows us to infer the biological effects of temperature in olfaction.At intermediate odorant concentrations heat always generates a reduction of olfactory sensitivity, as they would be expected to compensate for the increase of volatiles in the air. Cold produces the opposite effect. These changes are observed in both sexes and in natural populations as well as in standard laboratory stocks.Short applications suffice to cause detectable olfactory perception changes, but even prolonged temperature treatments have only a transitory effect. Together, these results suggest that olfaction in Drosophila underlies acclimatization to environmental temperature. However, sensitivity changes are not immediate and may cause imperfect adjustment of olfactory function for short time periods.     

Comparative study on the properties of saturated phosphatidylethanolamine and phosphatidylcholine bilayers: Barrier characteristics and susceptibility to phospholipase A2 degradation

Comparative studies on bilayer systems of saturated phosphatidylcholines and phosphatidylethanolamines revealed a maximum in ionic permeability in phosphatidylcholine bilayers at the temperature of the gel to liquid-crystalline phase transition but such an increase in permeability was not detectable in bilayers of phosphatidylethanolamine. Furthermore, it was found that at the phase transition temperature the phosphatidylcholine bilayers are subject to rapid hydrolysis by pancreatic phospholipase A₂ whereas phosphatidylethanolamine bilayers are not. These differences are discussed in view of detailed information on the molecular organization in the gel and liquid crystalline phases of the two phospholipid classes.     

Predatory impact of the green crab (Carcinus maenas Linnaeus) on post-settlement winter flounder (Pseudopleuronectes americanus Walbaum) as revealed by immunological dietary analysis

Predation on flatfish during the early juvenile stage is an important factor regulating year-class strength and recruitment. In this study, immunological dietary analysis was performed on green crabs (Carcinus maenas) collected from the Niantic River, Connecticut, in an effort to evaluate the predatory impact of this species on post-settlement winter flounder (Pseudopleuronectes americanus). Through the use of species-specific antiserum, winter flounder proteins were identified in 4.8% of the green crab stomachs analyzed (n = 313, size range = 14-74 mm carapace width, CW), revealing that crabs ≥ 29 mm CW are predators of post-settlement winter flounder in natural populations. The most significant factor underlying the predator-prey interaction was the relative size relationship between species, such that the incidence of winter flounder remains in the stomach contents of green crabs was positively correlated with predator-to-prey size ratio. Results from dietary analysis were incorporated into a deterministic model to estimate the average daily instantaneous mortality and cumulative mortality of winter flounder owing to green crab predation. Accordingly, green crabs may account for 0.4% to 7.7% (mean = 2.2%) of the daily mortality of winter flounder and consume 1.1% to 32.3% (mean = 10.2%) of the flounder year-class. Model simulations further indicate that variations in green crab abundance and size-structure account for the greatest variability in winter flounder mortality. Relative to other macro-crustacean predators, however, predation by green crabs has a minimal effect on winter flounder survival, due in large part to the low densities of these crabs in temperate estuaries.     

Effect of temperature on the electrical activity of the rat epididymis in vitro

1. 1.|Regional differences in the frequency of electrical activity in rat epididymis were maintained at all temperatures below 39°C.

2. 2.|The change in frequency per deg C increased with temperature and was highest in the temperature region of 34–39°C and the Arrhenius plots of the frequency were linear and parallel in all parts of the epididymis.

3. 3.|The Q₁₀ of the frequency varied between 2.2.–4.3.

4. 4.|The conduction velocity at the cauda epididymis was highest (2.8 mm/s) at 37°C. The Q₁₀ of the conduction velocity was 2.3 in the temperature region of 24–37°C.