A light intensity threshold for schooling in the Atlantic mackerel, Scomber scombrus

The schooling behaviour of Atlantic mackerel was studied in a large tank at different light intensities in the range 12.6–1.8 × 10⁻¹⁰μEs⁻¹ m⁻². Variable light intensity was produced by accurately controlling the current to a green light-emitting diode (LED) 3 m above the experimental tank. Under high light levels (1.8 × 10⁻⁶μEs⁻¹ m⁻²) mackerel always formed a single school, whereas at lower levels (1.8 × 10⁻⁸μEs⁻¹ m⁻²) they swam as individuals. At light levels down to 1.0 × 10⁻⁶μEs⁻¹ m⁻² the mean nearest neighbour distance in a school remained relatively constant (0.3–0.9 body lengths), and individual mackerel swam along a path which deviated from the position of their nearest neighbours by less than 14°. As light dropped below 1.8 × 10⁻⁷μEs⁻¹ m⁻², both nearest neighbour distance and heading angle between nearest neighbours increased, with mean values of 1–1.8 body lengths and 23–92°, respectively, at 1.8 × 10⁻⁹μEs⁻¹ m⁻². The results are discussed in terms of ambient light conditions in the sea.     

Permeability of the Chara cell membrane for ethylene glycol, glycerol, meso-erythritol, xylitol and mannitol

The permeability of internodal cells of Chara australis R. Brown for polyol molecules was determined by using a turgor balance to measure the increase in the osmotic pressure of an internodal cell incubated in artificial pond water containing one of the polyol compounds tested. The permeabilities for ethylene glycol, glycerol, meso -erythritol, xylitol and mannitol were (4. 39 ± 0. 52) × 10⁻⁹, (1. 49 ± 0. 40) × 10¹⁰, (4. 92 ± 0. 27) × 10⁻¹⁰ (9. 9 ± 3. 4) × 10¹¹ and (7. 6 ± 4. 8) × 10⁻¹² m s⁻³, respectively. The permeability for glycerol was slightly smaller than that for meso -erythritol, whose molecular weight is larger than that of glycerol in this homologous series: but the reason for this is not clear.     

Olfactory sensitivity of the herbivorous grass carp, Ctenopharyngodon idella, to amino acids

The olfactory sensitivity of a herbivore, the grass carp, Ctenopharyngodon idella , to ten amino acids was investigated using electrophysiological recording techniques. Underwater electroolfactogram recordings increased exponentially with logarithmic increases of stimulus concentration from threshold to 1 × 10⁻³ m. Calculated detection thresholds ranged from 1 × 10^−7.15 m to 1 × 10^−8.7 M and are similar to those previously reported for carnivorous fish species. The relative stimulatory efficacy (RSE) of the ten amino acids determined at 1 × 10⁻⁴ M revealed five groups of stimuli, with cysteine the most stimulatory and proline the least. Measures of amino acid RSE did not differ significantly from those of previously studied carnivores, except for arginine. Grass carp showed strong responses to this compound, whereas it has produced only limited responses in carnivores. Differences in the responsiveness of herbivores and carnivores were not observed, suggesting that feeding niche segregation is probably not facilitated by differential olfactory sensitivities to feeding stimuli.     

Protoporphyrinogen oxidation coupled to nitrite reduction with membranes from Desulfovibrio gigas

Abstract The oxidation of protoporphyrinogen by membranes from Desulfovibrio gigas with nitrite as the electron acceptor proceeds at the ratio of 1 mol protoporphyrin produced for each mol of nitrite reduced. Coupled to the protoporphyrinogen-nitrite reaction is the esterification of ortho-phosphate with a P/2e⁻ value of 0.92. Pentachlorophenol, 3 × 10⁻⁵ M, and carbonyl cyanide m -chlorophenyl hydrazone, 3 × 10⁻⁶ M, serve as uncouplers of phosphorylation while rotenone, 9 × 10⁻⁶ M, and hydroxyquinoline- N -oxide, 0.1 × 10⁻⁶ M, inhibit electron flow from protoporphyrinogen oxidase to nitrite reductase.     

Emission rate of amino acids and ammonia and their role in olfactory preference behaviour of juvenile Arctic charr, Salvelinus alpinus (L.)

The behaviour of juvenile Arctic charr, Salvelinus alpinus (L.) , to an abrupt concentration step of L-amino acids, L-alanine and ammonium chloride was studied by fluviarium technique. The emission rates of these substances were studied. Juvenile Arctic charr emit 8.0 × 10⁻⁴ mol total ammonia-N kg⁻¹ h⁻¹ and 3.3 × I0⁻⁵ mol amino acids kg⁻¹ h⁻¹. In behaviour tests the charr avoided 5.6x 10⁻⁶and 5.6 × 10⁻⁷ M ammonium chloride. The 17 L-amino acid mixture, ranked as observed in the analysis of emission, was avoided at 4.6 × 10⁻⁷ M, while 100 times dilution of this value gave neither avoidance nor attraction. The charr avoided L-alanine tested alone at the concentration of 4.6 × 10 ⁻⁷ M. Anosmic charr showed neither avoidance nor attraction to the mixture of 17 amino acids tested at 4.6 × 10⁻⁷ M. The results indicate that ammonia as well as emitted amino acids are not responsible for the olfactory mediated attraction to conspecific odour shown earlier in Arctic charr. On the contrary, these substances may have a negative effect by reducing the strength of attraction.     

Factors related to gizzard shad and the threadfin shad occurrence and abundance in Florida lakes

Gizzard shad Dorosoma cepedianum were collected in 23 and threadfin shad D. petenense were collected in 22 of the 60 Florida lakes sampled. Logistic regression equations were 94% effective for predicting gizzard shad occurrence from chlorophyll and lake surface area, and 84% effective for predicting threadfin shad occurrence from lake surface area and lake volume inhabited (PVI). Occurrence of both shad species was related positively to lake size. In lakes where gizzard shad or threadfin shad were collected, shad density and biomass of both shad species were related positively to chlorophyll. Gizzard shad populations were generally vulnerable to predation in lakes, with the per cent of gizzard shad ≤200mm L _T values exceeding 60% with few exceptions. Effects of gizzard shad and threadfin shad on fish community dynamics may be confined to relatively large (>100 ha) and fertile (chlorophyll >20–30μg l⁻¹) Florida lakes.     

Foraging success of largemouth bass at different light intensities: implications for time and depth of feeding

Laboratory feeding trials were conducted to determine how light intensity affects foraging success by the visual piscivore, the largemouth bass ( Micropterus salmoides ). Foraging success was greater than 95% at light levels ranging from low intensity daylight (2.43 × 10² lx) to moonlight (3 × 10⁻³ lx), but declined significantly to 62% at starlight (2 × 10⁻⁴ lx) and near 0% in total darkness. Over a range of low to high water clarities (0.5, 2.0, and 4.0 m Secchi depth), estimated depth limits for feeding during the day ranged between 5.5 to 44 m and from 1.6 to 13 m at night during a full moon. At starlight, light intensity rapidly attenuated to a level below the feeding threshold within 0.5 m of the surface at all water clarities. The depth of the water column available for feeding in low clarity water (0.5 m Secchi) was 67 and 75% less than at moderate (2.0 m Secchi) and high (4.0 m Secchi) water clarities. The findings illustrate how differences in the light environment can have important ramifications for predator-prey interactions.     

Flooding, gas exchange and hydraulic root conductivity of highbush blueberry

Highbush blueberry plants ( Vaccinium corymbosum L. cv. Bluecrop) growing in containers were flooded in the laboratory for various durations to determine the effect of flooding on carbon assimilation, photosynthetic response to varying CO₂ and O₂ concentrations and apparent quantum yield as measured in an open flow gas analysis system. Hydraulic conductivity of the root was also measured using a pressure chamber. Root conductivity was lower and the effect of increasing CO₂ levels on carbon assimilation less for flooded than unflooded plants after short-(i-2 days), intermediate-(10–14 days) and long-term (35–40 days) flooding. A reduction in O₂ levels surrounding the leaves from 21 to 2% for unflooded plants increased carbon assimilation by 33% and carboxylation efficiency from 0.012 to 0.021 mol CO₂ fixed (mol CO₂)⁻¹. Carboxylation efficiency of flooded plants, however, was unaffected by a decrease in percentage O₂, averaging 0.005 mol CO₂ fixed (mol CO₂)⁻¹. Apparent quantum yield decreased from 2.2 × 10⁻¹ mol of CO₂ fixed (mol light)⁻¹ for unflooded plants to 2.0 × 10⁻³ and 9.0 × 10⁻⁴ for intermediate- and long-term flooding durations, respectively. Shortterm flooding reduced carbon assimilation via a decrease in stomatal conductance, while longer flooding durations also decreased the carboxylation efficiency of the leaf.     

Adventitious root formation 'in vitro' in apple rootstocks (Malus pumila) II. Uptake and distribution of indol-3yl-acetic acid during the auxin-sensitive phase in M.9 and M.26

During the auxin-sensitive phase of root initiation, rates of 3-indolyl- [2-¹⁴C] acetic acid (IAA) uptake into the 1 cm bases of shoots of the apple rootstock M.9 ( Malus pumila Mill.) 'in vitro' were not significantly affected by the presence of 10⁻³ M phloroglucinol (PG) using either liquid or agar-solidified media. The use of a liquid medium did however reduce rates of uptake over a 10-day period of auxin application. The distribution of labelled IAA between the 1-cm base and the shoot remainder was not affected by PG.
Exposure of shoots of the difficult-to-root M.9 and the easy-to-root M.26, to 2.8 × 10⁻⁵ M IAA containing [2-¹⁴C] IAA revealed no positive correlation between the amount of label taken up by the 1-cm base and rooting performance. M.9 bases absorbed almost twice as much label as M.26 after 9 days but had produced only one-third as many roots. Measurements of label distribution between the 1-cm base and the shoot remainder showed that less than 10% of the label moved to the shoot remainder over a 6-day period of auxin application. Dose-response curves of IAA and rooting over the range 1 × 10⁻⁵ M and 3 × 10⁻³ M showed that root number in M.9 was at an optimum at 1 × 10⁻³ M IAA after 6 days whilst M.26 required only 1 × 10⁻⁴ M for a similar response. These data support the hypothesis that differences in rooting of the two rootstocks reflect differences in the endogenous metabolism of exogenous IAA and not differences in its rates of uptake or distribution in the shoots.     

Retrospective approach to investigating the early life history of a diadromous fish: allis shad Alosa alosa (L.) in the Gironde–Garonne–Dordogne watershed

In this study, the identification of major ontogenetic events and the duration of the fresh water and estuarine phases before the seaward exit of young allis shad Alosa alosa were investigated retrospectively, using the otoliths of spawners. Daily growth increment periodicity in the otoliths was validated with an accuracy of 4 days (9·4%) for fish >30 days. The specific limits of the Sr:Ca ratios in the otoliths, indicating fish movements between salinity 'compartments', were up to 1·1 ×10⁻³ for the freshwater phase, 1·1 to 1·9 × 10⁻³ for the estuarine phase and 1·9 × 10⁻³ for the marine phase. In early life history, a major event occured at 22 days, which was marked on the otoliths by a change in the direction of the otolith growth axis. This event was related to a change in larval swimming behaviour. Juvenile freshwater residence time was between 58 and 123 days, with a median duration of 88 days. Contrary to what has been estimated in previous studies, the present study showed that the estuarine phase lasted from 4 to 36 days, with a median value of 11 days. Seaward exit occurred in fish aged from 63 to 150 days, with a median age of 99 days. These results have important implications for the sustainable management of this species.     

Conjugative transfer of the transposon Tn919 to lactic acid bacteria

Abstract The streptococcal transposon Tn 919 was transferred from Streptococcus faecalis GF590 to selected Group N Streptococcus strains and to one strain each of Lactobacillus plantarum and Leuconostoc cremoris , using the filter mating method. An S. lactis MG1363 Rif^r Tc^r transconjugant also acted as a donor, but was less efficient than GF590. Frequencies of transfer varied between 4.0 × 10⁻⁸ and 5.29 × 10⁻⁵ per recipient. Further analysis of S. lactis MG1363 Sm^r Tc^r transconjugants showed that insertion of Tn 919 into the chromosome was site-specific.     

Taste responses of the facial and glossopharyngeal nerves to amino acids in the rainbow trout

No significant differences were noted between responses of rainbow trout Oncorhynchus mykiss facial and glossopharyngeal nerves to 15 amino acids. Nine of these amino acids tested at 10⁻² M were stimulatory, whereas only two tested at 10⁻³ M were effective gustatory stimuli. For both nerve systems, ≤10⁻³ M L-proline was the most stimulatory amino acid, with an estimated threshold of 10⁻⁷ M; however, L-α-amino-β-guanidino-propionic acid (estimated threshold of 3×10⁻³ M), was the most potent compound at 10⁻² M. These results indicate that the same amino acids activate taste buds innervated by facial and glossopharyngeal nerves, respectively, and suggest that the same amino acids can be important in chemosensory feeding behaviour in the rainbow trout.     

Stability and conjugal transfer kinetics of a TOL plasmid in Pseudomonas aeruginosa PAO 1162

Abstract Batch mating experiments were employed to study the kinetics of the conjugal transfer of a TOL plasmid, using the transconjugant strain Pseudomonas aeruginosa PAO 1162 (TOL) as the plasmid donor and Pseudomonas putida PB 2442 and Pseudomonas aeruginosa PAO 1162N as the plasmid recipients. Transfer rates from PAO 1162 (TOL) to PAO 1162N and PB 2442 measured for exponentially grown PAO 1162 (TOL) were 1.81 × 10⁻¹⁴ (standard error (S.E.) 1.25 × 10⁻¹⁵) ml·cell⁻¹min⁻¹ and 3.32 × 10⁻¹³ (S.E. 4.42 × 10⁻¹⁴) ml·cell⁻¹min⁻¹, respectively. The instability of the TOL plasmid in PAO 1162 (TOL) was evaluated under conditions that were non-selective for maintenance of the TOL catabolic functions. The measured rates of instability were 6.7 10⁻⁶ to 8.3 10⁻⁶ min⁻¹, and the loss of the catabolic functions was mainly caused by structural instability of the plasmid.     

CONTENT OF ATP IN CULTIVATED NEURONS AND ASTROCYTES EXPOSED TO BALANCED AND POTASSIUM-RICH MEDIA

Abstract— The content of ATP was measured in neurons from dorsal root ganglia and in cortical and spinal astrocytes with the luciferase method. No ATP could be demonstrated in the cortical cells but in the dorsal root neurons and spinal astrocytes an average amount of 7·9 and 11·9 × 10⁻¹⁵ mol per cell respectively was found. An increase in the external potassium concentration had no effect on the content of ATP in neurons (7·1 × 10⁻¹⁵ mol/cell) but led to a significant ( P < 0·005) decline to 6·4 × 10⁻¹⁵ mol per cell in the astrocytes.     

Multisite Interactions Between Pb2+ and Protein Kinase C and Its Role in Norepinephrine Release from Bovine Adrenal Chromaffin Cells

Abstract: We investigated the interaction between Pb²⁺ and protein kinase C (PKC) in the Pb²⁺-induced release of norepinephrine (NE) from permeabilized adrenal chromaffin cells. Our analysis of endogenous PKC activity in permeabilized cells suggests that Pb²⁺ interacts with the adrenal enzyme at multiple sites. Pb²⁺ activates the enzyme through high-affinity ( K _A(Pb) = 2.4 × 10⁻¹² M ) interactions and inhibits the enzyme by competitive and noncompetitive interactions with nanomolar-( K _i = 7.1 × 10⁻⁹ M ) and micromolar- ( K '_i = 2.8 × 10⁻⁷ M ) affinity sites, respectively. Activation of PKC by 12- O -tetradecanoylphorbol 13-acetate (TPA) in Ca²⁺-deficient, Pb²⁺-containing medium, enhances the Pb²⁺-induced NE release from permeabilized chromaffin cells by lowering the concentration of Pb²⁺ required for half-maximal activation of the secretory response from 7.5 × 10⁻¹⁰ to 5.7 × 10⁻¹¹ M . The PKC inhibitors staurosporine and pseudosubstrate PKC (19–36) abolish the effect of TPA without affecting the Pb²⁺-induced secretion in the absence of TPA. These results indicate that (a) Pb²⁺ is a partial agonist of PKC, capable of both activating and inhibiting the enzyme and (b) synergistic activation of PKC by TPA and Pb²⁺ results in increased sensitivity of exocytosis to Pb²⁺ but is not obligatory for Pb²⁺-triggered secretion.     

Effect of triazinone on root growth and gravireaction

The effects of a synthetic growth promoter, 4-ethoxy-l-( p -tolyl)-S-triazine-2,6 (1H, 3H)-dione [TA], on growth and gravireaction of Zea mays L. (cv. LG 11) roots were investigated. In horizontal, intact roots, pretreatment with TA at 4 × 10⁻⁴ M inhibited the gravireaction. If the pretreated roots were rinsed with a buffer solution before incubation, the TA effect was reduced, indicating that a continuous presence of TA was necessary for its maximal activity. On the other hand, the TA pretreatment (1×10⁻⁵, 1×10⁻⁴ and 4 × 10⁻⁴ M ) promoted the elongation of these roots. The TA effect was stronger for illuminated roots than for those kept in darkness. TA also decreased the lateral curvature of half-decapitated roots maintained vertically in light. This indicates that the action of TA could be associated with some growth inhibiting substances produced or released in cap cells.     

ATPase Activity in Isolated Flagella from Euglena gracilis

SYNOPSIS. The ATPase activity of isolated flagella was studied in Euglena gracilis strain Z in the presence of Mg⁺⁺ or Ca⁺⁺. With Mg⁺⁺, the optimum activity was at pH 7 and with Ca⁺⁺, at pH 9. The K _m values were respectively 6.6 × 10⁻⁴ and 3.6 × 10⁻⁴. Activity was influenced also by temperature and ionic strength. Results with inhibitors of membrane ATPase suggest the presence of a specific contractile system in the flagella. Our results are compatible with a multicomponent enzymic system containing 2 active ATPases.     

Conjugal plasmid transfer between lactococci on solid surface matings and during cheese making

Abstract The concept of deliberate use of genetically enginereed microorganisms in dairy products requires a clear understanding of their behaviour and of the dissemination of introduced DNA in these strains. Thus, transfer of a self-transmissible plasmid and a non-self-transmissible but mobilizable plasmid from an engineered strain of Lactococcus lactis subsp. lactis IL 1403 to wild-type strains of L. lactis subsp. lactis and subsp. cremoris of technological interest was studied on standard solid surface matings and in cheese during manufacture. On solid surface matings, transfer of the conjugative plasmid occurred at frequencies ranging from < 2.3 × 10⁻⁹ to 2.8 × 10⁻⁴. Mobilization of the non-conjugative plasmid was observed at a lower frequency (ca. 10⁻⁵) in only one recipient which was then selected along with another recipient strain (presenting intermediate transfer frequencies) for making Camembert cheese. During cheese making, only the transfer of the self-transmissible plasmid was observed. It occurred in the early stages of manufacturing. The transfer frequencies were 7.0 × 10⁻⁸ or 7.6 × 10⁻¹ 1, depending upon the recipient strain. These were about 3 to 4 orders of magnitude lower than on solid surface matings. Mobilization of the non-conjugative plasmid was never detected in cheese.     

Sublethal effects of imidacloprid and pymetrozine on population growth parameters of cabbage aphid, Brevicoryne brassicae on rapeseed, Brassica napus L.

Efficiency of imidacloprid and pymetrozine on population growth parameters of cabbage aphid, Brevicoryne brassicae L. （Homoptera： Aphididae） was determined using demographic toxicology by leaf dip method. At first, bioassay tests were performed. The LC50 value and confidence limit for imidacloprid and pymetrozine were 1.61 × 10^-5 mol/L （0.74 × 10^-5-2.66 × 10^-5） and 2.14 × 10^-4 mol/L （1.24 × 10^-4-3.40 × 10^-4）, respectively. To evaluate the sublethal effect of two insecticides on population growth parameters of cabbage aphid, LC30 concentrations of imidacloprid and pymetrozine were used at 5 mol/L and 30 mol/L. The experiments were carried out in a incubator at 20±1℃, 60% ± 5% RH and 16：8 （L：D） photoperiod on canola seedlings, Brassica napus L. var. ＇PF＇. Net fecundity rate decreased in both insecticide-treated populations. Intrinsic rates of increase （rm） were lower in imidacloprid and pymetrozine treatments than in controls. Intrinsic birth rates also decreased in treated populations. There was a relative increase in intrinsic death rates of treated populations. The mean generation times and doubling time were also lower in populations treated with insecticides than in controls. There was a considerable reduction in the average numbers of nymphs reproduced per female as compared with the control. The average longevity of female adults in the control was significantly different from those treated with imidacloprid and pymetrozine. However, there was no significant differences in aphid life-table parameters between the two insecticide-treated populations （P 〉 0.01）.     

β-Adrenergic antagonists and carp (Cyprinus carpio L.) sperm motility

We studied the effects of two β-adrenergic antagonists, atenolol and propranolol, on carp sperm motility. Atenolol (10⁻³−10⁻⁸ m ) has no appreciable effects while propranolol (6 × 10⁻⁵−3 × 10⁻⁶ m ) affects the percentage of sperm motility in a dose-dependent fashion.