Effects Of Light Cycles Research Articles

Effects of light cycle on circadian feeding activity and digestive physiology in Haliotis discus hannai

The abalone Haliotis discus hannai is a typical nocturnal animal. It generally feeds and moves at night but evades light by hiding in the shade during the day. However, the effects of different light cycles on the feeding physiology and potential molecular mechanisms responsible for such effects in H. discus hannai have not yet been reported. We examined the feeding patterns of abalones under different light (L)/dark (D) cycles (0 L:24D, 12 L:12D, 24 L:0D) using an infrared camera and analyzed the relationships between circadian digestive enzyme activities, gene expression levels of neuropeptide Y (NPY) and its receptor (NPYR), which can promote appetite, and feeding rhythms. Feeding in abalones, including searching for food and, food capture and intake, was examined by observation of videos. The percentage of abalones feeding under different light/dark cycles had two peaks, at 20:00–22:00 and 02:00–04:00. The ingestion rate was significantly higher in abalones maintained under 12 L:12D compared with 24 L:0D conditions. The percentage of feeding individuals and food intake were significantly lower in the “daytime” compared with at “night” irrespective of the light/dark cycle, suggesting the existence of an independent internal timing mechanism and the possible involvement of circadian clock genes in the regulation of periodic feeding activity in abalones. In abalones maintained under 12 L:12D and 24 L:0D cycles, protease, cellulase, and α-amylase activities started to increase from 18:00, 2 h before the first peak of food intake. Expression levels of NPY peaked at 20:00 and expression levels of NPYR increased again at 04:00, suggesting that NPY and NPYR might be induced before and after the two peak periods of food intake in abalones, respectively. These findings demonstrate the feeding rhythm and ingestion rate of abalones under different light/dark cycles, as well as the relationships among digestive enzyme activities, gene expression levels of NPY and NPYR, and feeding activity, which in turn provides a useful reference for the development of optimal feeding strategies and improved food utilization in abalone aquaculture production.

Effects of light cycle on motion behaviour and melatonin secretion in Haliotis discus hannai

The abalone Haliotis discus hannai is a typical nocturnal marine invertebrate. In this study, a quantitative analysis was performed on the motion behaviour characteristics of abalones exposed to different light cycles (0 L:24D, 12 L:12D, 24 L:0D) using infrared camera and behavioural analysis software. A preliminary analysis of the intrinsic correlations between melatonin secretion and abalone behaviour rhythms was also conducted. The results showed that the cumulative moving distance and duration of movement for abalone in the 0 L:24D group were significantly higher than those in the 12 L:12D and 24 L:0D groups (P < 0.05). The mean and maximum moving velocities of abalones in the 12 L:12D group were significantly higher than those in the 0 L:24D group (P < 0.05). The maximum cumulative moving distance and duration of movement for abalone in the 12 L:12D and 24 L:0D groups occurred between 00:00–03:00. In the 0 L:24D group, peak cumulative moving distance and duration movement were recorded between 00:00–03:00 and 15:00–18:00. According to the results of cosine analysis, melatonin content and expression levels of aralkylamine N-acetyl transferase (AANAT) and N-acetylserotonin O-methyltransferase (ASMT) in the 12 L:12D and 24 L:0D groups showed significant circadian cosine rhythms (P < 0.05) and tended to be higher during the day and lower at night. Compared with the variation trend of melatonin, the expression levels of melatonin receptor (MTR) in each group showed significant circadian cosine rhythms (P < 0.05). Especially in the 0 L:24D group, the expression levels of MTR also tended to be higher during the day and lower at night, indicating that MTR may mediate other factors which participate in the regulation of abalone circadian rhythms. The results of this study provide a quantitative description of the motion behaviour characteristics of abalone exposed to different light cycles. The intrinsic correlation between melatonin secretion and abalone motion behaviour rhythms was also examined in this study, which in turn provides a reference for light regulation and feeding strategies in aquaculture production.

Investigation of lipid, carbohydrate and protein production from &lt;i&gt;Chlorella vulgaris&lt;/i&gt; in controlled environment minkery wastewater

In an effort to incorporate a novel bioremediation technology into minkery wastewater treatment systems, this study aimed to investigate the effect of light cycles on the simultaneous production of Chlorella vulgaris biomass, lipid, carbohydrate, and protein in controlled environment minkery wastewater. Diluted minkery cage-washing wastewater used in the experiments, which were designed as a completely randomised design with a single factor (light cycle) experiment. The single factor had four levels: six-day continuous light (photoautotrophic), 48-h light/24-h dark (mixotrophic), 24-h light/48-h dark (mixotrophic), and six-day continuous dark (heterotrophic) cycle, which were randomly assigned to the 2.25-litre vertical column controlled environment photobioreactors (PBR), each equipped with an independent cool-white fluorescent light (8 W, 6,700 K) operated at room temperature. The pH in each PBR was monitored and controlled using independent pH meters and air pumps. During six-day cultivations, continuous light and 48-h light/24-h dark cycles achieved the largest biomass (82.50 mg L−1 day−1 and 79.50 mg L−1 day−1, respectively) and protein productivities (42.62 mg L−1 day−1 and 38.79 mg L−1 day−1, respectively) out of Chlorella vulgaris in minkery wastewater; however, using 48-h light/24-h dark cycle instead of continuous light cycle would reduce the energy cost of cultivation. The light cycles of continuous light, 48-h light/24-h dark, and 24-h light/48-h dark achieved the highest lipid (15.06 mg L−1 day−1, 16.03 mg L−1 day−1, 12.82 mg L−1 day−1, respectively) and carbohydrate (11.15 mg L−1 day−1, 11.89 mg L−1 day−1, 8.08 mg L−1 day−1, respectively) productivities, and there was no statistically significant difference in between; however, using 24-h light/48-h light cycle would again reduce the energy cost of cultivation compared to the other two cycles. Overall, for the cultivation of Chlorella vulgaris in minkery wastewater, the most appropriate light cycle for the production of microalgae biomass and crude protein seems to be the mixotrophic growth under 48-h light/24-h dark cycle, while the mixotrophic growth of 24-h light/48-h dark cycle was the most appropriate system for the production of lipid and carbohydrate. Providing a supplemental organic carbon source, preferably from another waste stream, has a potential to change the story with respect to the competitiveness of continuous dark (heterotrophic) cycle, and studying other microalgae strains may make minkery wastewater even more competitive compared to traditional culture mediums.

The effects of light cycle phase on morphine-induced conditioned taste aversions in the Lewis, Fischer and Sprague-Dawley rat strains

The present experiment investigated the effect of light cycle phase on morphine-induced conditioned taste aversions in the Lewis (LEW), Fischer (F344) and Sprague-Dawley (SD) rat strains. Separate groups of rats from each strain were trained during either the light phase or the dark phase on a procedure in which saccharin was paired with one of two doses of morphine (or vehicle). With 3.2mg/kg morphine, strain differences were observed during the light phase, with F344 rats displaying a significantly stronger taste aversion than the LEW rats, who displayed a significantly stronger aversion than the SD rats. In contrast, during the dark phase, 3.2mg/kg morphine produced comparable, moderately strong aversions in all strains. With 10.0mg/kg morphine, F344 rats developed stronger aversions than either the LEW or SD rats in both phases of the light cycle. The effect of light cycle was most clearly seen in the SD rats, where stronger aversions were produced in the dark phase for both morphine doses. For the LEW rats, stronger aversions were produced in the dark as compared to the light only with the low dose of morphine. For the F344 rats, aversions of comparable strength were observed in both phases of the light cycle for both morphine doses. The finding that light cycle differentially affects morphine-induced taste aversions in these strains is consistent with what is known about strain differences in circadian patterns of corticosterone activity and with previous results relating corticosterone to morphine-induced taste aversions.

Effect of light cycles (night/day) on CO 2 fixation and biomass production by microalgae in photobioreactors

The objective of this study was to evaluate the effect of the photoperiod on the biomass production and carbon dioxide fixation rates using a photosynthetic culture of the cyanobacterium Aphanothece microscopica Nägeli in bubble column photobioreactors. The cultures were carried out at temperatures of 35 °C, air enriched with carbon dioxide at concentrations of 15% and photon flux density of 150 μmol m −2 s −1. The light cycles evaluated were 0:24, 2:22, 4:20, 6:18, 8:16, 10:14, 12:12, 14:10, 16:8, 18:6, 20:4, 22:2 and 24:0 (night:day), respectively. The results obtained indicated that the duration of the light periods was a determinant factor in the performance of the photobioreactors. A linear reduction in biomass production and carbon dioxide fixation with reductions in the duration of the light period was evident, with the exception of the 12:12 (night:day) cycles. Reductions of up to 99.69% in the carbon-fixation rates as compared with cultures under continuous illumination were obtained.

Conservation of locomotor behavior in the golden hamster: effects of light cycle and a circadian period mutation

OSIEL, S., D. A. GOLOMBEK AND M. R. RALPH. Conservation of locomotor behavior in the golden hamster: Effects of light cycle and a circadian period mutation. PHYSIOL BEHAV 65(1) 123–131, 1998.—Locomotor activity in rodents is restricted temporally by the animal’s circadian system. The relative stability of both the species-specific pattern and the amount of locomotor activity per cycle suggested that this behavior may be regulated by conservative mechanisms. In these experiments, the wheel-running behavior of golden hamsters carrying the circadian period mutation, tau, was analyzed in animals housed in a 24-h light:dark cycle (LD) and in constant dark (DD) conditions to determine which aspects of this behavior were conserved. In DD, apart from the change in period which defines the mutation, no main effects of allele combination were found in either average amount of activity, activity profile, or length of the activity phase. In LD, wild-type behavior did not differ from that in DD; however, heterozygous mutants exhibited early onsets of activity, significant fragmentation of both activity and rest, an increase in the duration of the active phase, and an overall decrease in the amount of activity. Despite these differences, the total amount of time spent on the wheel in LD or DD was the same for all environment/genotype combinations. The data show that a conservative mechanism that may influence daily patterns of locomotor behavior is related more to a drive to perform the behavior than the quantity or timing of the behavior itself.

Circadian Rhythm of Emergence in the Mosquito Wyeomyia mitchellii and the Effects of Light Cycles on the Pupation Rhythm of Culex nigripalpus1

The rhythmic control of emergence was studied in 2 Florida mosquitoes, Wyeomyia mitchellii (Theobald) and Culex nigripalpus Theobald. In W. mitchellii , there were no indications of a pupation rhythm in the various light cycles tested but there was a pronounced emergence rhythm. This rhythm proved to be an endogenous circadian rhythm of the kind reported in Drosophila pseudoobscura . It showed distinct phase shifts and resetting under altered light regimes, was synchronized by a non-repeated light signal of 12 h, and, once initiated during the pupal stage, continued in DD for at least 4 days. This is the 1st report of an endogenous circadian rhythm of emergence, as opposed to a pupation rhythm, in mosquitoes. In C. nigripalpus , where a pupation rhythm occurred in LD 12:12, other light cycles during the pupal stage shifted the onset and the mean time of the emergence peak 1–3 h. This slight shift was not due to entrainment, however, but the result of the light cycles affecting the developmental period, and hence, the timing of the pupation and emergence peaks.

Effect of Light Cycles on Ovipositions and Egg Production

VARIATIONS in the egg production rates of individual birds are undesirable in some fields of research. The precision with which experiments are conducted may be improved by reducing the uncontrolled variation or obtaining more observations. The present report suggests a way of reducing variation caused by unequal rates of production.The use of artificial light to increase egg production has stimulated considerable research on the mechanism of light stimulus. Most of these studies have been limited to intensity and to light/dark ratios within a 24-hour day. The “light-dark cycle” is associated with two expressions of laying behavior, rate of egg production and the time at which eggs are laid.The effect of the length of the light-dark cycle on egg production was demonstrated by Byerly and Moore (1941) who reported that both clutch length and total egg production were significantly greater during short periods of lay which were subdivided into .