Moon orientation in adult and young sandhoppers

In the last 30 years, lunar orientation has received little attention from students of animal orientation. Even in Talitrus saltator, the first animals in which the lunar compass was demonstrated, research did not continue. Our studies have demonstrated that: 1) chronometrically compensated lunar orientation is independent of the earth's magnetic field (an ever present non-chronometric orientation reference); 2) lunar orientation is independent of the lunar shape; and 3) the lunar compass is also used by young animals born in the laboratory (without experience in nature). Accepted: 30 September 1998     

Phenotypic plasticity in sun orientation of sandhoppers

Summary Littoral sandhoppers perform zonal orientation mainly by means of sun orientation, which in Mediterranean populations was shown to be inborn, associated with a genetically determined directional tendency adapted to the shoreline of each population. In case of changes of the shoreline the genetic heterogeneity of populations and learning ability may cooperate in providing adaptation both at the population and at the individual level. This hypothesis has been tested carrying on studies on the ontogenesis of the reactionnorm of this behavioural trait inTalitrus saltator (Montagu) (Crustacea: Amphipoda) of a Tyrrhenian population which from previous results shows a well adapted seaward orientation. Sun orientation was analysed away from the sea shore, both in laboratory-raised individuals of different ages and in individuals captured in the field, by repeated releases on dry flat sand or in a glass bowl. Results showed variability within and between individuals of directional tendency, which varies in the individual life depending on age and experience. Particularly, age seems to bring canalization as variability within individuals tends to decrease with age. In order to evaluate the role of experience, we trained individuals to direct themselves towards a direction different from that genetically determined. The majority of the individuals showed a learning ability in the training situation. The importance of phenotypic plasticity in the oriented behaviour of sandhoppers is discussed.Dedicated in gratitude to Prof. Dr. Drs. h.c. M. Lindauer     

Moon and sun compasses in sandhoppers rely on two separate chronometric mechanisms

The relationship between the chronometric system of compensation for the apparent movement of the sun and that for the moon has been the subject of several, never proven, hypotheses. Our studies on sandhoppers have demonstrated that the chronometric mechanism of the moon compass is separate from that of the sun compass. They show (i) that a period of seven days in constant darkness has no influence on the capacity for orientation, either solar or lunar, and indicates the presence of one or more continuously operating timing mechanisms; (ii) that two different shifts in the light–dark phase have no effect on the chronometric mechanism of lunar orientation, but they do affect that of solar orientation; and (iii) that exposure to an artificial moon delayed by seven days with respect to the natural cycle causes the expected change in the mean direction of individuals tested under the natural moon, but not of those tested under the sun.     

Seasonal variations of melatonin secretion in young females under natural and artificial light conditions in Fukuoka, Japan

The purpose of this study was to examine the seasonal variations of melatonin secretion of subjects and of their surrounding light conditions. Eight Japanese female students (20.1+/-2.6 yrs, Mean+/-SD) living in Fukuoka, Japan, participated in the present study. Saliva samples were collected every 3 hours over the course of a day, and the light intensity during daily life was measured every 1 min for 5 days in the four seasons. Almost all subjects had different melatonin secretory profiles in autumn, with only two subjects showing similar rhythms in all four seasons. The peak values of melatonin secretion calculated by a spline interpolation were higher in autumn than those in other seasons (p<0.001, Fisher's PLSD) and its peak time in this season was significantly delayed compared with those in spring and summer (p<0.05, Fisher's PLSD). The amount of time during daytime exposure to light of >1,000 lux was at least thirty minutes in all the seasons, and there were no significant differences among them. The relationship between peak level of melatonin secretion and amount of time of daytime light exposure to >1,000 lux was significant only in the autumn. During this season, there was a significant positive correlation (r=0.83, p<0.05, n=6), except for two subjects, whose melatonin secretion remained low.     

Photosynthesis under artificial light: the shift in primary and secondary metabolism

Providing an adequate quantity and quality of food for the escalating human population under changing climatic conditions is currently a great challenge. In outdoor cultures, sunlight provides energy (through photosynthesis) for photosynthetic organisms. They also use light quality to sense and respond to their environment. To increase the production capacity, controlled growing systems using artificial lighting have been taken into consideration. Recent development of light-emitting diode (LED) technologies presents an enormous potential for improving plant growth and making systems more sustainable. This review uses selected examples to show how LED can mimic natural light to ensure the growth and development of photosynthetic organisms, and how changes in intensity and wavelength can manipulate the plant metabolism with the aim to produce functionalized foods.     

Long-term chilling of young tomato plants under low light

The properties of two Calvin-cycle key enzymes, i.e. stromal fructose-1,6-bisphosphatase (sFBPase) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) were studied in the cultivated tomato (Lycopersicon esculentum Mill.) and in four lines of a wild tomato (L. peruvianum Mill.) from different altitudes. During chilling for 14 d at 10°C and low light, the activation energy (E_A) of the reaction catalyzed by sFBPase decreased by 5–10 kJ·mol^–1 inL. esculentum and the threeL. peruvianum lines from high altitudes. InL. peruvianum, no loss or only small losses of enzyme activity were observed during the chilling. Together with the change in E_A, this indicates that the latter species is able to acclimate its Calvin-cycle enzymes to low temperatures. InL. esculentum, the chilling stress resulted in the irreversible loss of 57% of the initial sFBPase activity. Under moderately photoinhibiting chilling conditions for 3 d, theL. peruvianum line from an intermediate altitude showed the largest decreases in both the ratio of variable to maximum chlorophyll fluorescence (F_v/F_m) and the in-vivo activation state of sFBPase, while the otherL. peruvianum lines showed no inhibition of sFBPase activation. Ribulose-1,5-bisphosphate carboxylase/oxygenase was isolated by differential ammonium-sulfate precipitation and gel filtration and characterized by two-dimensional electrophoresis. The enzyme fromL. esculentum had three isoforms of the small subunit of Rubisco, each with different isoelectric points. Of these, theL. peruvianum enzyme contained only the two more-acidic isoforms. Arrhenius plots of the specific activity of purified Rubisco showed breakpoints at approx. 17°C. Upon chilling, the specific activity of the enzyme fromL. esculentum decreased by 51%, while E_A below the breakpoint temperature increased from 129 to 189 kJ·mol^–1. In contrast, Rubisco from theL. peruvianum lines from high altitudes was unaffected by chilling. We tested several possibile explanations for Rubisco inactivation, using two-dimensional electrophoresis, analytical ultracentrifugation, gel filtration and inhibitor tests. No indications were found for differential expression of the subunit isoforms, proteolysis, aggregation, subunit disassembly, or inhibitor accumulation in the enzyme from chilledL. esculentum. We suggest that the activity loss in theL. esculentum enzyme upon chilling is the result of a modification of sulfhydryl groups or other sidechains of the protein.Abbreviations a.s.l. above sea level - Chl chlorophyll - DTT dithiothreitol - E_A activation energy - FBP fructose-1,6-bisphosphate - F_v/F_m ratio of variable to maximum chlorophyll fluorescence - HL high light (500 mol photons·m^–2·s^–1) - LSU large subunit of Rubisco - ME 2-mercaptoethanol - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase - RuBP ribulose-1,5-bisphosphate - sFBPase stromal fructose-1,6-bisphosphatase - SSU small subunit of Rubisco     

Long-term chilling of young tomato plants under low light and subsequent recovery

The influence of unfavourable climatic conditions at the onset of the growth period on chilling-sensitive tomato (Lycopersicon esculentum Mill., cv. Abunda) was studied by exposing young plants to combinations of low temperature and low light (60–100 mol quanta · m^–2 · s^–1) for several weeks. When the temperature did not decrease below a critical point (8 ° C) no loss of developmental capacity of the plants was detected. However, while new leaves were readily formed upon return to normal growth conditions (22/18 °C, day/night, in a greenhouse), net accumulation of biomass showed a lag phase of approximately one week. This delay was accompanied by a strong, irreversible inhibition of photosynthesis in the fully expanded leaves which had been exposed to the chilling treatment. When plants were subjected to temperatures below 8 ° C, survival rates decreased after three weeks at 6 ° C and irreversible damage of apical meristematic tissue occurred. Drought-hardening prior to chilling ensured survival at 6 ° C and protected the plants against meristem loss.Abreviation Chl chlorophyll Thanks are due to G.P. Telkamp for technical assistance. This research is financially supported by the Netherlands Technology Foundation (STW, Utrecht, The Netherlands), and is coordinated by the Foundation for Biological Research (BION, 's-Gravenhage, The Netherlands).     

Shape recognition and image orientation in young children]

A comparison was made of recognition of images in the direct and inverse "top-bottom" orientation. A child two and a half years old was to find the test image on the response card or to give a verbal reply. The verbal responses have shown that the child identifies well both the shape and orientation of the images. In experiments with the response card, the presentation of images in inverse orientation did not result in any mistakes in recognizing the shape nor did it prolong the latency of the reaction, and no correlation was found between the orientation of the presented and the response figures. A child trained to find images of both similar shape and orientation is incapable of indicating properly the orientation of an image presented for a limited time period. These facts are interpreted in terms of the hypothesis of multichannel transfer of information about the pattern in the visual system.     

Supplementary artificial light to increase egg production of geese under natural lighting conditions

A new supplementary lighting program was designed to increase the egg production of geese under natural light conditions. The objective of this study was to evaluate the effects of the supplementary lighting program on egg production of White Roman geese in an open housing system at the Tropic of Cancer. Forty mature White Roman geese were randomly allocated into two groups (male:female=1:4). The supplementary lighting program with a total daily photoperiod of between 12.0 h and 13.5 h was initiated on 1 November and withdrawn from the experimental group on 30 January. In contrast, the geese in the control group were kept under natural lighting conditions throughout this study. The results showed that the laying peak of the experimental group occurred earlier than normal in the reproductive season and the geese continued laying throughout the breeding season. The geese in the experimental group had 47.6 eggs/goose which was significantly (P<0.05) more than that of the control group having 26.4 eggs/goose. We can conclude that the supplemental lighting method will result in an earlier laying peak of the geese in the breeding season and higher egg production. The supplementary lighting program was able to maximize egg production in geese at the Tropic of Cancer.     

The effects of natural biofilms on the reattachment of young adult zebra mussels to artificial substrata

This laboratory study examined the effects of natural biofilms on the reattachment of young adult zebra mussels, Dreissena polymorpha, in Petri dishes. Natural biofilms were developed in glass and polystyrene Petri dishes using water samples collected at various times of the year. Biofilms were developed over 1, 3, 8, and 14 d. Controls were clean glass and polystyrene Petri dishes. Zebra mussels collected from the field (< or = 10 mm, ventral length) were placed in the dishes and their reattachment by byssal threads was recorded after 1 d. Zebra mussels reattached to the dish surface or the shells of other mussels in the dish, or remained unattached. The data indicate that reattachment to clean glass was greater than to clean polystyrene (p < or = 0.05, ANOVA), but there were no consistent differences between reattachment to filmed polystyrene and filmed glass dish surfaces. Zebra mussels in control and filmed glass dishes reattached in higher percentages to the dish surface compared to the shells of other mussels (p < or = 0.05, ANOVA). There was no difference in mussel of reattachment between the dish surface and the shells of other mussels in most control polystyrene dishes (p > 0.05, ANOVA), whereas in filmed polystyrene the percentage of reattachment to the dish surface was greater than to the shells of other mussels (p < or = 0.05, ANOVA). These results indicate that substratum wettability and the presence of biofilms on some types of substrata can be factors in the reattachment of young adult zebra mussels.     

Testosterone secretion in young and adult buffalo bulls

Studies were conducted to determine the 24-hour fluctuations in blood serum testosterone concentration in adult buffalo bulls, and to measure testosterone secretion before and after GnRH administration in male buffaloes of different age groups. Testosterone levels in three sexually mature bulls ranged from 0.2 to 2.7 ng/ml with a mean of 0.6 +/- 0.2 ng/ml. Samples collected in November had significantly higher (P<0.05) testosterone than those drawn in February (dry season) as did samples collected during the day as opposed to the night. Sera testosterone concentrations were lower in younger bulls with a range of 0.2 to 0.6 ng/ml. GnRH induced an increase in testosterone in 6, 12, 24 and 36-month old bulls with the greatest response being observed at 36 months. GnRH did not elicit a response in one-month old bulls. It may be concluded that baseline sera testosterone concentrations in buffalo bulls, as well as responsiveness to GnRH injection, increase with sexual maturity and are subject toseasonal and diurnal variations.     

Behavioural characterisation of young adult transgenic mice overexpressing galanin under the PDGF-B promoter

The behavioural phenotype of transgenic mice (3- to 5-months old) overexpressing galanin (GalOE) under the platelet-derived growth factor B (PDGF-B) promoter was evaluated in a battery of tests, including open field, locomotor cages, light-dark exploration test, elevated plus-maze and the Porsolt forced swim test. Learning and memory were assessed in the passive avoidance and the Morris water maze tasks. No difference between genotypes was found in exploratory activity in the open field. GalOE mice showed a slight increase in spontaneous locomotor activity assessed in the locomotor cages, but the amphetamine-induced increase in locomotor activity was somewhat lower in GalOE mice. Anxiety-like behaviour in the three different tests including open field, light-dark exploration and elevated plus-maze did not differ between genotypes. In the Porsolt forced swim test, GalOE mice displayed an increased time of immobility, indicative of increased learned helplessness possibly reflecting increased stress-susceptibility and/or depression-like behaviour. GalOE mice showed normal learning and memory retention in the passive avoidance and the Morris water maze tasks. These data support the hypothesis that galanin may have a role in functions related to mood states including affective disorders.     

Transient hypobaric hypoxia improves spatial orientation in young rats

To achieve a better understanding of learning and declarative memory under mild transient stress, we investigated the effect of brief hypobaric hypoxia on spatial orientation in rats. Young male Wistar rats aged 30 days were exposed for 60 min to hypobaric hypoxia, simulating an altitude of 7,000 m (23,000 ft) either shortly prior to attempting or after mastering an allothetic navigation task in the Morris water maze with a submerged platform. The post-hypoxic group performed significantly better in the navigation task than the control animals (the mean difference in escape latencies was 11 seconds; P=0.0033, two-way ANOVA with repeated measures, group x session). The experimental group also achieved a remarkably higher search efficiency (calculated as a percentage of successful trials per session), especially during the first four days following hypoxic stress (P=0.0018). During the subsequent training, the post-hypoxic group performed better than the control animals, whilst the efficiency levels of both groups progressively converged. Spatial memory retention and recall of well-trained rats were not affected by the transient hypobaric hypoxia. These results indicate that brief hypobaric hypoxia enhances rats' spatial orientation. Our findings are consistent with several studies, which also suggested that mild transient stress improves learning.     

Photosynthetic regulation under fluctuating light in field-grown Cerasus cerasoides: A comparison of young and mature leaves

Photosystem I (PSI) is a potential target of photoinhibition under fluctuating light. However, photosynthetic regulation under fluctuating light in field-grown plants is little known. Furthermore, it is unclear how young leaves protect PSI against fluctuating light under natural field conditions. In the present study, we examined chlorophyll fluorescence, P700 redox state and the electrochromic shift signal in the young and mature leaves of field-grown Cerasus cerasoides (Rosaceae). Within the first seconds after any increase in light intensity, young leaves showed higher proton gradient (ΔpH) across the thylakoid membranes than the mature leaves, preventing over-reduction of PSI in the young leaves. As a result, PSI was more tolerant to fluctuating light in the young leaves than in the mature leaves. Interestingly, after transition from low to high light, the activity of cyclic electron flow (CEF) in young leaves increased first to a high level and then decreased to a stable value, while this rapid stimulation of CEF was not observed in the mature leaves. Furthermore, the over-reduction of PSI significantly stimulated CEF in the young leaves but not in the mature leaves. Taken together, within the first seconds after any increase in illumination, the stimulation of CEF favors the rapid lumen acidification and optimizes the PSI redox state in the young leaves, protecting PSI against photoinhibition under fluctuating light in field-grown plants.     

沙漠人工植被的生态学取向及其途径

水是干旱沙漠植物生态系统中的最重要的限制因子。在干旱沙漠生境中建造人工植被的正确方向是要建造沙漠人工植被 ,就必须以提供额外的水资源为前提 ;在不能增加额外水资源的情况下不应增加沙漠人工植被 ;增加沙漠植被应保护现有植被和建造半人工植被为主。考察种群生态适应性的一般过程 :一是目前有无这种植物的天然种群 ,二是历史上是否有过这种植物的种群 ,三是目前的生境条件是否满足这种种群或群落的需要 ,四是有无人工提供生态资源的可能性。封育保护和建造半人工植被是建造沙漠植被的主要途径 ,保护地下水资源是根本途径。     

Gas exchange and antioxidative compounds in young beech trees under free-air ozone exposure and comparisons to adult trees

Three-year-old beech (Fagus sylvatica) seedlings growing in containers were placed into the sun and shade crown of a mature beech stand exposed to ambient (1 x O(3)) and double ambient (2 x O(3)) ozone concentrations at a free-air exposure system ("Kranzberg Forst", Germany). Pigments, alpha-tocopherol, glutathione, ascorbate, and gas exchange were measured in leaves during 2003 (a drought year) and 2004 (an average year). Sun-exposed seedlings showed higher contents of antioxidants, xanthophylls, and beta-carotene and lower contents of chlorophyll, alpha-carotene, and neoxanthin than shade-exposed seedlings. In 2003 sun-exposed seedlings showed higher contents of carotenoids and total glutathione and lower net photosynthesis rates (A(max)) compared to 2004. O(3) exposure generally affected the content of chlorophyll, the xanthophyll cycle, and the intercellular CO(2) concentration (c(i)). Seedlings differed from the adjacent adult trees in most biochemical and physiological parameters investigated: Sun exposed seedlings showed higher contents of alpha-tocopherol and xanthophylls and lower contents of ascorbate, chlorophyll, neoxanthin, and alpha-carotene compared to adult trees. Shade exposed seedlings had lower contents of xanthophylls, alpha-carotene, and alpha-tocopherol than shade leaves of old-growth trees. In 2003, seedlings had higher A(max), stomatal conductance (g(s)), and c(i) under 2 x O(3) than adult trees. The results showed that shade acclimated beech seedlings are more sensitive to O(3), possibly due to a lower antioxidative capacity per O(3) uptake. We conclude that beech seedlings are uncertain surrogates for adult beech trees.     

Adaptation-induced plasticity of orientation tuning in adult visual cortex

A key emergent property of the primary visual cortex (V1) is the orientation selectivity of its neurons. The extent to which adult visual cortical neurons can exhibit changes in orientation selectivity is unknown. Here we use single-unit recording and intrinsic signal imaging in V1 of adult cats to demonstrate systematic repulsive shifts in orientation preference following short-term exposure (adaptation) to one stimulus orientation. In contrast to the common view of adaptation as a passive process by which responses around the adapting orientation are reduced, we show that changes in orientation tuning also occur due to response increases at orientations away from the adapting stimulus. Adaptation-induced orientation plasticity is thus an active time-dependent process that involves network interactions and includes both response depression and enhancement.