Oviposition patterns and photoresponsivity in Japanese quail (coturnix coturnix japonica)

Abstract

Plots of oviposition times for an unselected group of 84 female Coturnix using the circular mean time for each bird on a central index time indicated a regularity in the data for individual birds. An analysis of pooled data using a moving average showed agreement with the temporal occurrence of the photoresponsive interval reported in the literature for gonadal development. These data were used to support a modification of existing hypothesis on the control of oviposition and ovulation.     

DIURNAL CELL DIVISION REGULATED BY GATING THE G1/S TRANSITION IN ENTEROMORPHA COMPRESSA (CHLOROPHYTA)1

The cell‐cycle progression of Enteromorpha compressa (L.) Nees (=Ulva compressa L.) was diurnally regulated by gating the G₁/S transition. When the gate was open, the cells were able to divide if they had attained a sufficient size. However, the cells were not able to divide while the gate was closed, even if the cells had attained sufficient size. The diurnal rhythm of cell division immediately disappeared when the thalli were transferred to continuous light or darkness. When the thalli were transferred to a shifted photoperiod, the rhythm of cell division immediately and accurately synchronized with the shifted photoperiod. These data support a gating‐system model regulated by light:dark (L:D) cycles rather than an endogenous circadian clock. A dark phase of 6 h or longer was essential for gate closing, and a light phase of 14 h was required to renew cell division after a dark phase of >6 h.     

Effect of Melatonin on the Intensity of Adenosine Production in the Rat Forebrain under Conditions of Acute Hypoxia and Varied Photoperiodicity

We studied the effect of injections of melatonin and modifications of the duration of illumination on the activity of 5-nucleotidase, an enzyme providing synthesis of adenosine, in the forebrain of juvenile male albino rats. The measurements were performed under conditions of acute hypobaric hypoxia. We found that, under conditions of natural illumination, neither isolated injections of melatonin nor acute hypoxia noticeably changed the activity of 5-nucleotidase. At the same time, acute hypoxia combined with melatonin injections increased the activity of this enzyme. A similar noticeable rise in the activity of 5-nucleotidase was observed after melatonin injections in normoxic animals kept in constant darkness, and in rats subjected to hypoxia without the above injections but under conditions of constant illumination. These data allow us to suppose that melatonin (whose level in the extracellular medium is a factor providing synchronization of endogenous temporal rhythms) stimulates 5-nucleotidase-mediated production of adenosine in brain neurons. Acute hypoxia promotes such an effect of melatonin.     

The influence of seasonal changes in light on hormones in normal cats and in cats with lesions of the superior colliculi and pretectum

Abstract

Two groups of cats with lesions of the superior colliculi and adjacent pretectal nuclei and two groups of sham‐operated cats were subjected simultaneously to artificial “bright winter” and “dim summer” lighting conditions and their endocrine state determined. Urinary excretion of 11‐hydroxycorticoids, adrenalin, and norad‐renalin were specified with fluorometric techniques, and thyroid function was assessed with an uptake measure of radioiodide and with a rate of release measure of radioiodide‐labelled hormones from the thyroid gland. The results indicated that the cats in the bright winter condition had much higher indices of thyroid and glucocorticoid function. No effect of the lighting schedules on the catecholamines, urinary volume or body weight was detected, and no effect of the lesion was detected. A comparison of these data with our previous longitudinal studies in cats, as well as with the literature on other species, indicates that (1) light is the Zeitgeber for the annual glucocorticoid rhythm; (2) even though light influences the activity of the thyroid gland, it is difficult to consider it as the Zeitgeber because thyroid rhythms do not exhibit annual rhythms; (3) with regard to the role of light in entraining the catecholamines, the results were equivocal, possibly because of the sampling times. The raison d'etre of biological rhythms is considered, and it is suggested that their provision of order to the temporal milieu may be viewed as a higher order aspect of homeostasis.     

Temperature and light effects on the circadian rhythm and locomotory activity of the plains garter snake (Thamnophis radix hayendi)

Abstract

The Locomotory activity of the Plains Garter snake was determined under L/D: 12/12 conditions at five constant temperatures and three light intensities during the light period. The snakes were diurnal at low temperatures with nocturnal activity increasing in various amounts at higher temperatures. The different light intensities had relatively small effects on the activity rhythm.

Activity was recorded under four constant light conditions at five constant temperatures and the characteristics of the free‐running rhythm measured. A comparison of the characteristics of the free‐running rhythm to Aschoff's circadian rule indicates that this snake is an exception to this rule.

Increase light intensity decreased total activity under all conditions. Under a L/D: 12/12 cycle the decrease in activity was more pronounced during the dark period than the light period.

It is suggested that crepuscular or nocturnal activity shown by snakes at high temperatures may be an effect the temperature level has on the biological clock and activity controlling mechanisms rather than temperature selection by the snake.     

Reproductive behavior of the Lake Malawi cichlid fish, <Emphasis Type="Italic">Tramitichromis intermedius</Emphasis>

Synopsis We studied the reproductive behavior of wild caught and captive-born, first generation offspring of the Lake Malawi fish, Tramitichromis intermedius(Teleostei, Cichlidae), held in aquaria. Spawning behavior includes an exchange of actions with dominant males performing bower construction and courtship behaviors while females focus on oviposition and mouthbrooding. Egg counts per oviposition and brooding and interbrooding periods of wild caught T. intermedius follow records of other mouthbrooding cichlid fishes. Observation of circling behavior suggests this behavioral trait may be used in mate choice as longer circling, indicating a secure territory and thus male dominance, leads to more oviposition events and hence the potential for larger broods. Comparisons of clutch size and total length of young at release from full-sized females vs. first spawners reveal smaller clutches and young from the younger females, most likely stemming from differences in body size. Investigation of spawning photoperiodicity also noted distinctions between the two groups with wild caught T. intermedius spawning activity peaking in the middle of the light cycle and captive-born, first spawners exhibiting no significant peak in activity. The trend to spawn midday is most likely influenced by predation factors, while the lack of a spawning periodicity in the offspring may be explained by developmental processes, the absence of environmental cues or the tendency for smaller males to be opportunistic in spawning events. The details of spawning behavior recorded in this study provide a database to investigate species differences and to indicate changes due to chemical and physical disturbances.     

Feeding patterns of a specialist and a generalist grasshopper: electronic monitoring on their host plants

Abstract Hypochlora alba (Dodge) is a specialist grasshopper that lives and feeds almost exclusively on Artemisia ludoviciana Nutt., a sage plant mostly avoided as food by generalist or polyphagous grasshoppers, such as Melanoplus sanguinipes (Fabr.). Adaptations to feeding on the pubescent sage foliage containing high levels of allelochemics may involve behavioural as well as physiological specialization. Using an electronic device to monitor feeding activity, we compared feeding periodicity, bout length, bout frequency, and overall time spent feeding by H.alba on sage foliage and by M.sanguinipes on seedling ryegrass ( Lolium perenne L.), the plants on which they had been reared. Although both species fed for about the same amount of time per day (c. 4–5%), they achieved this by two different feeding patterns. H. alba had feeding bouts averaging c. 10 min each, compared to c. 4–5 min for M.sanguinipes. Bout frequency was reversed, with M.sanguinipes feeding about once every hour and H.alba about half as often. Bout length for both species was unaffected by phase of the photoperiod while bout frequency, and consequently the rate of feeding in min/h, was typically reduced by two-thirds or more during the dark phase. The relationship of grasshopper feeding behaviour to host plant specialization is discussed.     

Stimulus selection (light) in four subspecies of deermice (Peromyscus maniculatus)

Abstract

Four subspecies of deermice (Peromyscus maniculatus) were selected from habitats along a gradient from mesic hardwood forests (gracilis), tall grass prairie (bairdi), short grass prairie (nebrascensis), to desert grassland (labecula) in effort to relate the light preferences of the mice to the habitat of their origin. Six individuals of each subspecies were maintained in dark chambers for 25 days, during which they could turn on a dim light for 30 seconds on ten of these days. Mice from the mesic habitats turned the lights on more frequently (light reinforcement) than mice from xeric habitats. The same subspecies that exhibited light reinforcement when raised in laboratory light conditions failed to show light reinforcement when raised in total darkness. The circadian periodicities also differed significantly among the subspecies. Conclusions drawn from the results were: (1) selection for light is genetically influenced as indicated by subspecific differences, (2) some genotypes are readily modified by environmental light conditions than others, and (3) natural selection in each environment appears to contribute to the degree of genetic fixation or genetic plasticity.     

Light-dependent Proton Excretion of Wheat (Triticum aestivum L.) and Maize (Zea mays L.) Roots

We investigated the change of root net proton excretion of seedlings of Triticum aestivum L. and Zea mays L. with daily variation of illumination using a multi-channel pH-stat system. We found an increase of net proton excretion during darkness and a drop after the beginning of illumination. Inhibition of carotenoid biosynthesis by norflurazone and photooxidation of chlorophylls did not change the periodicity or its induction. The induction of diurnal periodicity was possible with blue, green and red light. After induction the oscillation of net proton excretion continued for at least two cycles under constant light. We conclude that net H⁺ excretion of wheat and maize roots may be regulated by an endogenous clock or by a signal from the leaves. The nature of such a hypothetical signal remains unknown.