Escape manoeuvres of schooling Clupea harengus

The escape behaviour of schooling herring startled by an artificial sound stimulus was observed by means of high speed video filming. Response latencies showed two distinct peaks, at 30 ms and c . 100 ms. Escape responses belonging to the two latency groups showed different turning rates during the first stage of the response, and showed different escape trajectories. We suggest that long latency escapes may be responses to startled neighbours or simply weak responses to the sound stimulus. In addition, the different contraction rates during the C-bend formation seen in the two latency groups may imply differences in the neuronal commands. The escape responses of herring were directed away from the stimulus more often than towards it (88% of the total). These away responses were more common in long latency responses, suggesting that the latter enable herring to be more accurate in discerning the direction of the threat. Startled fish contracting their body towards the stimulus (performing a towards response) appear to correct their escape course, since their escape trajectory distribution is non-uniformty distributed around 360° and directed away from the stimulus. We hypothesize that when herring are schooling, the ability of each fish to correct its trajectory following turns towards the stimulus is enhanced.     

Experimental modification of stepping course in spontaneously initiated locomotor behavior in the crayfish Procambarus clarkii Girard

The stepping course in spontaneously initiated walking of crayfish was quantitatively analyzed using a spherical treadmill system. In complete darkness, some animals stepped either forward or backward at random whereas others showed individually a consistent tendency of stepping in a specific direction although no external sensory cue was provided. The tendency was statistically significant and invariable for at least 6-8 h. When a light stimulus was present in front of the animal, the stepping course tended to be backward or curved forward to avoid the stimulus. Either in complete darkness or in the presence of a light stimulus, the animal's tendency to step in a specific direction could be modified experimentally by applying electrical stimulation to a part of the animal body upon stepping in the preferred direction. The newly acquired tendency of stepping direction could be retained for 6 h and modified again by a similar procedure of electric stimulation. Both before and after modification of the stepping course tendency, animals seldom changed their stepping direction once the walking was initiated. These findings suggest that the stepping course in spontaneously initiated walking is significantly affected by animal's previous experience and could be predetermined at the onset of walking.     

Sensitization and habituation of the swimming behavior in ascidian larvae to light

Ascidian larvae of Ciona intestinalis change their photic behavior during the course of development. Newly hatched larvae show no response to a light stimulus at any intensity. At 4 hr after hatching, larvae were induced to start to swimming upon the cessation of illumination, and to stop swimming upon the onset of illumination. At a weaker light intensity (5.0 x 10(-3) J/m (2).s), the larvae showed similar responses to either a single stimulus or repeated stimuli of onset and cessation of light until 10 hr after hatching. At a stronger light intensity (3.2 x 10(-1) J/m(2).s), when the stimulus was repeated, they showed sensitization and habituation of the swimming response. At 3 hr after hatching the larvae failed to show any response to an initial stimulus at any intensity of light, but after several repeated stimuli (sensitization) they showed a swimming response at light intensities above 4.0 x 10(-2) J/m (2).s. At 5 hr and with intensity above 1.0 x 10 (-2) J/m(2).s, the larvae showed photoresponses to the first stimulus, but after several repetitions the larvae failed to stop swimming upon the onset of light (habituation). A repeated series of stimuli at stronger intensities of light caused greater habituation; this habituation was retained for about 1 min. Since the larval central nervous system in Ciona is comprised of only about 100 neurons, learning behavior in ascidian larvae should provide insights for a minimal mechanism of memory in vertebrates.     

Circadian control of spontaneous flight activity in the blowfly, Lucilia cuprina

ABSTRACT. Under laboratory light: dark cycles, the flight activity of adult Lucilia cuprina (Wied.) was low during darkness and uniformity high during light. This pattern persisted as a rhythm both in constant darkness and in constant light of intensity up to 1lx, with a period of approximately 22 h in each. Light pulses of 15 min at l00lx applied to the free-running rhythm in constant darkness generated phase shifts of up to 60°, 12-h light pulses of the same intensity generated maximal (180°) phase shifts. The phase response curves had shapes similar to those of a number of other insect rhythms. When exposed to light periods (70 lx) of greater than 12 h followed by constant darkness, the rhythm reinitiated at the light-dark transition from a constant phase equivalent to that at the time of the light-dark transition in the LD 12:12 cycle.     

Effects of environmental factors on virulence of the entomopathogenic fungus, Nomuraea rileyi, against the corn earworm, Helicoverpa armigera (Lep., Noctuidae)

The effects of environmental factors on infection of the entomopathogenic fungus, Nomuraea rileyi , isolated from the corn earworm, Helicoverpa armigera , in Taiwan, to its host insect were studied in the laboratory. The fungus caused higher larval mortality at 20°C than at 30°C when 5 × 10⁶ conidia/ml were sprayed on the fourth instar. However, mortality of the fifth instar injected with 1 × 10³ conidia/larva was not significantly different when the inoculated larvae were incubated from 15 to 30°C. The fungal development in inoculated larvae was best at 20 and 25°C after shifting from 20°C to either lower or higher temperatures. The germination rate was higher at 20 and 25°C than at 30 or 35°C. Conidial germination was better on the wash-off of insect cuticle than on Sabouraud maltose agar with yeast extract. Sporulation on chill-dried cadavers was maximal at 95 or 100% relative humidity than at lower levels of relative humidity. The time required for sporulation was 2 days less at 100% than at 95% relative humidity. Although photoperiod did not affect fifth instar mortality caused by N. rileyi , the median lethal time (LT₅₀) values were shorter upon incubating under light than in darkness. Incubation of infected cadavers under 12 or 24 h light resulted in 20-fold more conidial production than under full darkness. Therefore, illumination is necessary for development of this isolate on insect cadavers.     

Influence of light and temperature on daily activity patterns of three Israeli forms of Ptyodactylus (Reptilia: Gekkoninae)*

Activity of the gecko Ptyodactylus hasselquistii was recorded by Aktograph in cyclic light and temperature, continuous darkness or light with constant 30°C or cyclic temperature. The northern P. h. puiseuxi was more diurnal and the southern P. h. cf. hasselquistii more nocturnal than the common P. h. guttatus. Except in constant temperature and continuous light, activity was not randomly distributed throughout the day. The more nocturnal the animal was, the more the temperature played a role in determining its daily activity pattern.     

Temporal Changes in Swimming Direction during the Phototactic Orientation of Individual Cells in Cryptomonas sp.

The response of individual Cryptomonas cells to continuous lightwas recorded using infrared video-micrography. Swimming directionsand temporal shifts in swimming direction of each cell weremeasured. White light of 0.1–1 W m^–2 elicited apositive phototactic orientation, but did not induce any photophobicresponse. Light of 100 W m^–2 induced a photophobic responseat the onset of actinic irradiation, but did not induce positivephototactic orientation. No correlation between positive phototacticorientation and photophobic response was found in this species.The direction toward the light source was defined as 0°,and the direction away from the source as 180°. Within 2s after the onset of lateral monochromatic light of 570 nm at0.1 W m^–2, cells which were swimming in a direction ofless than 120° predominantly shifted their course towardthe light source. Cells swimming in directions of larger than120° shifted their course as randomly as those in the dark.Thus, for phototactic orientation, the cells must perceive thelight from their anterior side. (Received July 29, 1985; Accepted November 4, 1985)     

Contrasting photo- and thermoperiod-induced changes in abscisic acid and lipid contents in leaves of mungbean seedlings

Seedlings of Phaseolus aureus ROXB were grown under 12/12 h light/dark cycles with the light period at 32.5°C and darkness at 10°C (normal conditions N) or with light at 10°C and darkness at 32.5°C (inverse conditions, I). I-conditions affected the level of chlorophyll and carotenoids (very low), monogalactosyldiacylgycerol (low) and phosphatidylinositol (high) in the leaves. Leaves of I-seedlings showed a sharp and durable decline of relative water content during the low temperature phase. For the N-seedlings, loss of water was restricted to the end of this period. The loss of water was accompanied by visible symptoms of wilting at specific times of day. Although the pigment content remained nearly unchanged, ABA content of leaves of both N-and I-seedlings increased during water stress. Upon return to the warm period, ABA level continued to increase after the leaves had regained turgor, this 'after stress'increase being more pronounced in the leaves of I-seedlings. Exogenous application of ABA induced a slight increase in the content of phospholipids in N- and I-leaves and a decrease in free fatty acids, whereas monogalactosyldiacylglycerol content was significantly reduced in N-leaves after application of ABA. Upon transfer of I-plants to 20°C for 12 h during the light period, pigment and chloroplastic lipid content increased rapidly whereas upon a further exposure to 10°C in light, pigments and especially monogalactosyldiacylglycerol were lost. The control of pigment and lipid metabolism and the role of ABA during chilling stress are discussed.     

Illuminance preferences of nocturnal primates

Laboratory tests reveal a preference for illuminances in a broad range of night light by individuals belonging to four species of nocturnal primates (Aotus trivirgatus, Galago crassicaudatus, Galago senegalensis, andNycticebus coucang). In volitional tests the animals altered the light level very frequently, in one case as often as every 7 sec. In these tests the animals tended to avoid total darkness and extremely dim light as well as moderately bright light. These avoided levels, particularly extremely dim light and darkness, inhibited locomotor activity. The greater bush babies preferred dimmer light for manipulative activities than for locomotion. Nocturnal primates differ from nocturnal rodents in being much more highly motivated to seek variety and frequent stimulus change when in deprivation conditions, and in their avoiding and being markedly inhibited by darkness.     

Effects of changes in environmental lighting upon levels of hydroxyindole O-methyltransferase activity in the developing-chick gland.

The level of hydroxyindole O-methyltransferase (HIOMT) activity in the pienal gland of developing chicks raised under constant illumination rose more rapidly and to higher values than in the gland of birds maintained in constant darkness. Rates of net increase in activity, and levels of activity attained, for birds raised under a diurnal cycle of illumination were intermediate between those maintained in constant light or darkness. Under each of the lighting conditions, the course of increase in enzymic activity was markedly affected by variations in an unidentified factor, the source of which appeared to be the hatching eggs. Birds transferred from constant light to the dark showed either an arrest of increase in enzyme activity or a loss of activity until the levels equalled that observed for chicks of the same age raised in constant darkness. Chicks transferred from constant darkness to constant illumination showed marked increases in levels of enzyme activity at rates comparable with the maximal values observed with birds maintained under constant illumination, regardless of age and without delay. No diurnal cycle in level of HIOMT activity was observed in the pineals of 15-day birds.     

Triadimefon reduces transpiration and increases yield in water stressed plants

The total free amino acid pools in radicles of watermelon seeds, investigated during imbibition of water at 25°C, were higher under the most (darkness) than under the least (continuous broad spectrum far-red light) favourable light regime for germination. When seeds were imbibed in an appropriate osmotic solution of PEG-6000 (fully suppressing germination), in darkness or under continuous red or far-red light, the biochemical analyses of the radicles after 1,2,3 and 4 days from the onset of imbibition show that while the total soluble sugar content remains rather constant in all treatments, significant changes are observed in the total free amino acid pools. After the first day, a considerable increase characterizes the "darkness" pool in contrast to a moderate one under red, while the "far-red" pool remains constant. Ultimately, at 4 days, the three pools are 190,142 and 123% of the 0 day radicle one. The qualitative free amino acid determination of the 4 day darkness and far-red pools shows a considerably increased percentage contribution of glutamic acid, arginine and citrulline in the "darkness" pool. The free amino acid increase in non-illuminated radicles may be correlated to germinability; moreover, it is evidently a phytochrome-mediated, pre-germinatory event, probably due to the hydrolysis of proteins (known to be rich in glutamic acid and arginine), stored in the radicle.     

Phytochrome control of skotodormancy release in Grand Rapids lettuce achenes

Light-requiring Grand Rapids lettuce ( Lactuca sativa L.) achenes develop skotodormancy when imbibed in darkness for 7 days at 25°C. Redried skotodormant achenes maintain this type of dormancy upon subsequent rehydration. At 25°C full germination of skotodormant achenes can be induced by continuous and intermittent red light illumination as well as by several brief red irradiations given daily. One brief (10 min) red light irradiation can partly break skotodormancy at 20°C, while at lower temperatures the same treatment results in full induction of germination. Phytochrome control of the release from skotodormancy is proven by a) the dependence of the germination response on the relative sequence of red and far-red light in cyclic irradiations, and b) the reversion of red action by subsequent far-red irradiation. The time course of germination of skotodormant achenes treated with intermittent red light depends upon the length of dark interval between the light pulses. Germination is considerably delayed compared to that of non-skotodormant ones, induced by a single brief red light treatment. This fact in combination with the requirement, over a long period of time, of P_fr action for full manifestation of germination, indicates that skotodormancy is a deeper form of dormancy. It is concluded that the germination of lettuce achenes may always be subjected to phytochrome control.     

Diapause in a Glasgow strain of the flour moth, Ephestia kuehniella

ABSTRACT. The incidence of diapause in Ephestia kuehniella Zeller from an unhealed granary in Scotland was influenced by both photoperiod and temperature. At 25°C, nearly 50% of larvae entered diapause when reared in continuous darkness (DD) and up to 30% did so in short photoperiods. Little diapause was detected around LD 14:10 but a second, smaller peak of about 20% occurred at LD 16:8 and LD 18:6, falling away again to nearly zero in continuous light. More larvae entered diapause when reared continuously at 15 or 20°C than at 25 and 30°C. However, when larvae reared from hatch at 25°C in LD 16:8 were transferred after 1 week to 15°C in LD 9:15, almost twice as many entered diapause as did those reared at 15°C throughout. The sensitive phase for diapause induction occurred near the start of the final instar. The mean duration of diapause was between 2 and 3 months in most photoperiods at 20 and 25°C, and was shorter at 15°C. However, in DD at 25°C, it lasted about 7 months. Termination of diapause was hastened in larvae reared at 25°C in DD by transferring them to LD 14:10, and also by chilling them at 7.5°C for 6 weeks before returning to 25°C in DD. In an unhealed store in southern England, viable adults emerged from May to July and originated from larvae which terminated diapause relatively late. It would appear from the results of transferring larvae back to the laboratory at various times during the winter that some phases of diapause development were completed quite early after exposure to low temperatures, although no further development took place in the store until temperatures rose again in April.     

Light and temperature action in germination of seeds of the empress tree (Paulownia tomentosa)

Seeds of the empress tree ( Paulownia tomentosa Steud.) were imbibed for two weeks in darkness at constant temperatures (18, 23 or 28°C), and then irradiated with red light for 5 min. Germination was poor if it took place at the same temperature as imbibition, but a high percentage was achieved if the seeds were exposed to higher or lower temperatures before they were irradiated. Maximum germination was obtained when the difference between pretreatment and imbibition was about 10°C. The effect increased with the duration of the pretreatment and was optimal at 24 h. The effect decreased as the time lapse between temperature pretreatment and red light irradiation increased, and it was lost after two days. If pretreatment was shorter than 24 h (12 h). a high percent of germination was obtained by alternating pretreatment and imbibition temperatures. The germination of seeds imbibed in 40% heavy water was also stimulated by temperature pretreatments. Light and temperature also exhibited an interactive effect in the germination of seeds that were imbibed in darkness for only 3 days. For each of the germination phases there was a temperature at which the time needed for 50% germination was the shortest, namely 35°C during imbibition, 37.5°C in the period of P_fr activity. and 32.5°C during radicle protrusion. The data obtained are shortly discussed in relation to the domestication of empress tree in Southern Europe.     

Light effects on α-amylase activity and carbohydrate content in relation to lipid mobilization during the seedling growth of sunflower

The changes in α-amylase activity and in starch and free sugar content were investigated in correlation with lipid mobilization inHelianthus annuus during the first 15 days of seedling growth in discontinuous light and in darkness. Throughout the seedling development α-amylase activity increased more significantly in light than in darkness. It was always lower in cotyledons than in other tissues of the embryo axis. In both culture conditions, most of the transitory carbohydrates accumulated in germinating cotyledons were very likely synthesized by gluconeogenesis from the stored lipid breakdown. Nevertheless, in light-grown cotyledons, photosynthesis contributes to increase the carbohydrate levels. The study of several soluble sugars indicates that 1) sucrose stored in cotyledons of mature seeds was used at the onset of seedling growth, more rapidly in light than in darkness, 2) galactose and xylose, both involved as precursors of some cell-wall polysaccharides, remained at a very low level throughout the 15 days and 3) glucose, fructose and maltose accumulated in old etiolated cotyledons in contrast to what occurred in the light.     

Temperature dependent reduction of protochlorophyllide in darkness followed by the assembly of active photosystems in pigment mutant C-2A' of Scenedesmus obliquus

In the wild type of Scenedesmus obliquus strain D3 grown heterotrophically, the chlorophyll biosynthesis and thus the reduction of protochlorophyllide to chlorophyllide takes place in darkness. However, in pigment mutant C-2A' of Scenedesmus obliquus only traces of protochlorophyllide are reduced under optimal growth conditions in darkness. By lowering the growth temperature from 33° to 15–25°C, protochlorophyllide can be reduced in darkness. At 20°C this process is about 10 times more active than at 33°C, but reaches only about 13% of the light-dependent chlorophyll biosynthesis. The chlorophylls synthesized at the lower temperatures are inserted into the pigment-protein complexes and photosystem I as well as photosys-tem II capacities are developed. The rate of light-independent protochlorophyllide reduction at lower temperatures is not limited by the enzyme PChlide-oxidoreductase itself, but rather by its substrate, being in turn limited by the amount of 5-amino levulinic acid (ALA) available.     

Phase response relationships between light pulses and the melatonin rhythm in rats.

There is some controversy whether phase response curves constructed from studies conducted after acute release into constant darkness (Type II) or after prolonged constant darkness are comparable. This study investigated the effects of brief low-intensity light pulses on the onset of 6-sulphatoxymelatonin excretion in rats 48 to 60 h after lights-off and after 14 days of continuous darkness. In the former condition, maximum phase delays occurred between 4 and 6 h after expected lights-off, but no phase advances were observed within 2 days of the presentation of the stimulus. When the times of the pulses were plotted in relation to the individual onsets, peak light-induced phase delays occurred 0 to 2 h after melatonin onset. After 14 days in continuous darkness, the peak phase delays also occurred 0 to 2 h after melatonin onset and were slightly but significantly smaller. No significant phase advances were observed. In a separate small series of experiments, the temperature rhythm of rats was shown to be delayed by a comparable degree to that of melatonin by light pulses 2 and 4 h after expected lights-off under the Type II conditions. It is concluded that phase response curves conducted under Type I and Type II conditions are comparable.     

Stem extension rate in light-grown plants. Evidence for an endogenous circadian rhythm in Chenopodium rubrum

Stem extension in light-grown plants of Chenopodium rubrum L. ecotype selection 184 (50°10'N; 150°35'W) was recorded continuously for periods up to one week at constant temperature. Stem extension rate measurements were made with linear voltage-displacement transducer devices. At the beginning of experiments, the 3rd intenode above the cotyledons was about 5 mm long. Stem extension rate exhibited a rhythmic behaviour in continuous white light (20 W m⁻²), and in continuous darkness with a period of approximately 23 h. In continuous darkness, the amplitude of the rhythm damped out very quickly after 24 h and a second peak was just measurable. The mean value of the stem extension rate was dependent on the light fluence before the experiments. This overt rhythm, which could be observed at the individual plant or even internode level, exhibited the characteristics of an endogenous circadian rhythm. There was no correlation of the peak time to local time. The peak time was determined by the time of transfer from dark to light for dark periods equal to or longer than 8 h, and the phase was shifted by the time of transfer from light to dark at the proper phase of a pre-existing rhythm.     

Response to directional light by leaves of a sun-tracking lupine (Lupinus succulentus)

Experiments were done to examine the phototrophic response of sun-tracking leaves of Lupinus succulentus Dougl. to fixed beams of white and broad band light. Upon irradiation with 15 W m⁻² white light that struck the laminae at an angle of 45°, there was a 45–60 min lag period prior to leaf movement. The greatest rate of movement was 15° h⁻¹, and reorientation ceased when leaves attained a position within 15° of perpendicular to the light beam. Laminar movement was largely pulvinar, and a 60 min inductive light treatment was sufficient to activate a maximum pulvinar response in subsequent darkness. Light striking the lamina at angles between 20 and 70° induced similar maximum pulvinar responses and only light that struck the upper (adaxial) leaf surface was effective. Leaf tracking was fully activated by blue light but not by red or yellow light.     

Annual cycles of body weight in the Namie's frosted bat, Vespertilio superans superans

In order to elucidate the circannual cycles of fat deposition and depletion in hibernating bats, annual rhythm of body weight was examined in Vespertilio superans superans under a variety of environmental conditions. Under near natural conditions, adult females put on weight rapidly from October to November. The laboratory born subadult females kept in constant darkness at warm temperature gained weight at the same time as the adults. The length of weight cycle was about 10 months in adult females kept in 14 L : 10 D at about 24°C. These results suggest that cycles of fat deposition and loss are controlled by a modifiable endogenous circannual rhythm. Body weight rhythm persisted normally under warmer environmental conditions preventing the bats from hibernation. It is considered that the circannual cycles of fat gain and loss are relatively stable and not dependent on the hibernation cycle. Prolonged gestation period and delayed beginning of lactation by cold environment in summer did not affect the body weight rhythm. Temperature may be a more important environmental stimulus (or Zeitgeber) for the circannual rhythm than light and its effects may vary with phases.