Effects of photoperiod on the reproductive physiology of male flying foxes, Pteropus poliocephalus

1992 ◽  
Vol 4 (1) ◽  
pp. 43 ◽  
Author(s):  
MA McGuckin ◽  
AW Blackshaw
Keyword(s):  
Reproductive Physiology ◽  
Adult Males ◽  
Progressive Decrease ◽  
Natural Conditions ◽  
Timing Of Reproduction ◽  
Pteropus Poliocephalus ◽  
Natural Photoperiod ◽  
Short Days ◽  
Photoperiod Manipulation

Melatonion concentrations were determined in plasma pools obtained from adult male Pteropus poliocephalus (autumn mating season) at four times of the year. Melatonin levels increased within 3 h of sunset and remained elevated for the duration of the scotophase at all times of the year. Two photoperiod manipulation experiments were performed to examine the role of daylength in the regulation of the timing of the breeding season of this species. In Experiment 1, three adult males were transferred from natural short days to 16L:8D for 137 days and then photoperiod was progressively decreased over 120 days to 9L:15D; this photoperiod was then maintained for 350 days. Testicular volume (TV) peaked during decreasing photoperiod well before the time of maximal size in natural conditions. During the period in extended short photoperiod these bats showed several cycles of TV change with a progressively decreasing interval between cycles. In Experiment 2, nine adult males were exposed to the same shift to 16L:8D as in Experiment 1, but were subsequently split into three groups: 8L:16D, progressive decrease to 8L:16D and maintenance in 16L:8D. The 8L:16D and decreasing photoperiod groups showed coincident premature increases in TV, as in Experiment 1, whereas in the 16L:8D group TV increased at about the same time as in animals in natural photoperiod. Melatonin determination in the different experimental groups showed that duration of secretion was related to the length of the scotophase in all cases. These experiments demonstrate that regulation of the timing of reproduction in males of this species is influenced by changes in daylength.

The role of seasonally altering photoperiod in regulating physiology in Atlantic cod (Gadus morhua). Part I. Sexual maturation

2007 ◽  
Vol 64 (1) ◽  
pp. 84-97 ◽  
Author(s):  
Andrew Davie ◽  
Mark JR Porter ◽  
Niall R Bromage ◽  
Herve Migaud
Keyword(s):  
Sexual Maturation ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Reproductive Activity ◽  
Continuous Illumination ◽  
Natural Photoperiod ◽  
Artificial Photoperiod ◽  
Commercially Important ◽  
Photoperiod Manipulation

While the Atlantic cod (Gadus morhua) displays clear seasonality in its reproductive cycle, the exact photic signal that entrains this rhythm is yet undefined. This present work developed a model to describe the photic regulation of reproduction in the species in comparison with other commercially important temperate teleosts. This was achieved through the strategic masking of the natural photoperiod cycle during the first 2 years of life with the application of continuous illumination. The results demonstrated that it is the falling autumnal photoperiod signal after the summer solstice, more specifically after October, that is responsible for recruiting individuals to enter the sexual maturation cycle. Furthermore, in all treatments where this signal was masked through the application of continuous illumination, there was no significant reproductive activity and growth was improved by up to 60% at 27 months posthatch. This information is of particular value to the developing cod aquaculture industry in which the management of reproduction using artificial photoperiod manipulation will be of vital economic importance.

Role of prolactin in the photoperiodic control of moulting in the mink (Mustela vison)

1984 ◽  
Vol 103 (1) ◽  
pp. 9-15 ◽  
Author(s):  
L. Martinet ◽  
D. Allain ◽  
C. Weiner
Keyword(s):  
Physiological Role ◽  
Plasma Prolactin ◽  
Summer Solstice ◽  
Natural Lighting ◽  
Short Day ◽  
Lighting Conditions ◽  
Natural Photoperiod ◽  
Moulting Cycle ◽  
Short Days

ABSTRACT Beginning at the summer solstice adult female mink were maintained in long- or short-day photoperiods and treated with bromocriptine or prolactin. In control females kept under natural lighting conditions the moult coincided with the seasonal decrease in prolactin and resulted in the growth of a dense winter coat which was completed by the end of November. Long days, which slowed the decrease in plasma prolactin relative to animals in the natural photoperiod, induced a more or less complete moult followed by growth of a thin summer coat. On the contrary we observed an accelerated decrease in plasma prolactin concentrations followed by an early and brief moult in females kept under long days but treated with bromocriptine and in females under short days. The growth of a dense winter coat was completed by the end of September in all the females of the short-day group and in six of eleven females treated with bromocriptine. In the other five females, moult was followed by the growth of a summer coat. These results may suggest that the decline of prolactin after the summer solstice is responsible for the onset of the autumn moult, but the early, abbreviated moult and the growth of a winter coat observed in females kept under short days and treated with prolactin do not seem to support this hypothesis. However, the huge non-physiological levels of prolactin measured in the plasma of these females and the appearance of abnormal white under-hairs might suggest that the hormonal balance in this group was completely disturbed by the treatment. The physiological role of prolactin in the seasonal moulting cycle in mink is discussed. J. Endocr. (1984) 103,9–15

Pineal denervation by cervical sympathetic ganglionectomy suppresses the role of photoperiod on pregnancy or pseudopregnancy, body weight and moulting periods in the mink (Mustela vison)

1985 ◽  
Vol 107 (1) ◽  
pp. 31-39 ◽  
Author(s):  
L. Martinet ◽  
D. Allain ◽  
Y. Chabi
Keyword(s):  
Body Weight ◽  
Environmental Factors ◽  
Prolactin Secretion ◽  
Corpora Lutea ◽  
Progesterone Secretion ◽  
Cervical Ganglion ◽  
Cervical Sympathetic ◽  
Implantation Period ◽  
Short Days

ABSTRACT In mink, termination of the delayed implantation period, following reactivation of the corpora lutea, and onset of the spring moult are associated with a rise in prolactin secretion triggered by increasing daylength, while decreasing daylength induces the autumn moult. To establish whether suppression of the function of the pineal rendered the mink unresponsive to daylength changes, the superior cervical ganglion was removed bilaterally 2–4 weeks before mating. Intact and operated females were then left outdoors or were put under a lighting regime of either 15 h light: 9 h darkness (15L: 9D) or 8L: 16D. In July, at the end of the spring moult, the 15L: 9D lighting regime was changed to one of 8L: 16D. Under artificial photoperiods ganglionectomy suppressed the stimulatory role of long days and the inhibitory role of short days on prolactin secretion, and consequently on progesterone secretion and spring moult. Neither was the autumn moult, induced early in intact females by the change to a short photoperiod, advanced in ganglionectomized females, showing that the latter were unresponsive to the artificial modification of the photoperiod. However, in animals kept outdoors, prolactin and progesterone secretion and spring moult were not changed by ganglionectomy. Increase in body weight and autumn moult were only slightly delayed by the operation suggesting that other environmental factors had replaced the synchronizing effect of the daylength changes. Alternatively the desynchronization between intact females responsive to photoperiodism and those rendered unresponsive may be too slow to be observed soon after ganglionectomy. J. Endocr. (1985) 107, 31–39

scholarly journals The Effect of Weak Electrolyte Solutions on the Hatching Rate of the Eggs of Tricho-Strongylus Retortaeformis (Zeder) and its Interpretation in Terms of a Proposed Hatching Mechanism of Strongyloid Eggs

1958 ◽  
Vol 35 (3) ◽  
pp. 584-601
Author(s):  
P. A. G. WILSON
Keyword(s):  
Water Permeability ◽  
Electrolyte Solutions ◽  
Hatching Rate ◽  
Natural Conditions ◽  
Ionic Solutions ◽  
Rate Of Increase ◽  
Egg Membrane ◽  
Hatching Eggs ◽  
Colligative Properties

1. The influence of solutions of NaCl on the hatching of eggs of Trichostrongylus retortaeformis is studied. It is shown that the effects are not the consequence of colligative properties, but are related to ionic phenomena. 0.05 N-NaCl slows down the rate of hatch without impairing the ultimate ‘hatchability’ of the eggs. Processes of development up to hatching are not slowed down. 2. The effect demonstrated in the case of NaCl is shown to be shared by eight other electrolytes, the depression in the rate of hatch being proportional to the mobility of the ions in solution. On the assumption that the effect of the ions is due to a penetration of the egg membrane(s) the rate of entry is shown to be controlled by the speed of the slower ion in any one salt. 3. The influence of NaCl on the permeability of hatching eggs to water is studied. It is shown that the rate of increase in permeability is slowed down sufficiently in NaCl to control the rate of hatch. The inference that water permeability is a necessary prerequisite for hatching is made, a further hypothetical process being invoked to account for the rate of hatch in the absence of NaCl, since it is not then controlled by changes in water permeability. 4. The probability that the net effect of ionic solutions on the eggs is one concerned with the rate of breakdown of the inner wax-like layer of the egg is strengthened by experiments demonstrating that the depressing influence of NaCl is antagonized by ‘Teepol’, though the comparable influence of other, non-emulsifying, compounds cannot be explained. 5. The role of water permeability in the hatching mechanism is investigated. 6. A hatching mechanism of strongyloid eggs is proposed which involves two processes, the first dependent upon the osmotic relationships of the unhatched larva to its environment, the second being some sort of chemical weakening of the outer shell. 7. It is suggested that the effect of ions on hatching rate assists the ‘embryonated egg’ to survive under natural conditions when the hatched first-stage larva might otherwise be destroyed by desiccation.

scholarly journals Castration, cult and agriculture. Perspectives on Greek animal sacrifice

2014 ◽  
Vol 7 ◽  
pp. 153-174 ◽  
Author(s):  
Gunnel Ekroth
Keyword(s):  
Ancient Greece ◽  
Adult Males ◽  
Animal Sacrifice ◽  
Economic Reality ◽  
The Sacrifice ◽  
Sacred Laws

The castration of most male animals seems to have been the rule in ancient Greece when rearing cattle, sheep, goats, and pigs; only very few adult males are needed for breeding purposes and flocks of bulls, rams, billy-goats and boars are difficult to keep, since they are too aggressive. Castrated males yield more and fattier meat, and, in the case of sheep, more wool. Still, sacred laws and sacrificial calendars stipulate the sacrifice of uncastrated victims, and vase-paintings frequently represent bulls, rams and billy-goats in ritual contexts. This paper will discuss the role of uncastrated male animals in Greek cult in the Archaic, Classical and Hellenistic periods, both from a religious and an agricultural perspective. Of particular interest are the relations between the practical, economic reality and the theological perception of sacrifice. These issues will be explored using epigraphical, literary, iconographical and zooarchaeological evidence.

scholarly journals The Potential of Building Tourist Cities by Using Existing Resources in Uzbekistan with an Innovative Approach

2020 ◽  
Vol 6 ◽  
Author(s):  
Madina M. Khashimova ◽  
Shakhzod F. Turakulov
Keyword(s):  
Highly Qualified ◽  
Natural Conditions ◽  
Foreign Countries ◽  
Economic Infrastructure ◽  
The Republic ◽  
High Level ◽  
Effective Use ◽  
Steep Slopes ◽  
Training Area

This article reflects the construction of tourist cities using the resources available on the territory of Uzbekistan. The benefits of utilisation for the development of tourism infrastructure from geological cities that are not exploited, included in the available resources, have been analyzed. The high level of efficiency in the use of geological cities is based on the availability of economic infrastructure, which is recognized as the application of this infrastructure in the construction of tourist cities is low in costs. The article shows the specific natural anchors of three ecotouristic objects, the srategic plans for effective use of these anchors. Proposals on the expediency of the establishment of camps, bags, summer recreation zones are included in these facilities. The abundance of excursion facilities and attractions in the objects of ecotourism expressed their views on the possibility of opening remarkable travel destinations. And the steep slopes of the mountain are shown to be a special training area for training highly qualified climbers. Reflecting the peculiarities of the nature of the objects of the ecosystem, the role of these settlements with unique natural conditions in the development of tourism is established. The potential for the construction of such ecotouristic cities in the Republic of Uzbekistan is high, and the growth in the efficiency of the use of such potentials is reported to increase the number of tourists coming from foreign countries to Uzbekistan.

scholarly journals Marketing analysis of the Villány wine region

2014 ◽  
pp. 119-123
Author(s):  
Klára Törökné Kiss
Keyword(s):  
Wine Industry ◽  
Natural Conditions ◽  
Wine Production ◽  
Wine Consumption ◽  
The Future ◽  
Marketing Analysis ◽  
Wine Region

Hungarian wine is not in such a bad position as it is considered. We have outstanding specialists and the country’s natural conditions are also proper. In Hungary, there are wine production and wine consumption has a major traditions. The role of marketing in our wine industry is growing more and more, and this trend is expected to continue in the future. The development of tourism in wine-growing regions and advertising would considerably promote the popularity of Hungarian wine.

Flowering of Stylosanthes guianensis in controlled temperatures under natural photoperiod

1984 ◽  
Vol 35 (2) ◽  
pp. 219 ◽  
Author(s):  
RL Ison ◽  
LR Humphreys
Keyword(s):  
Floral Initiation ◽  
Minimum Duration ◽  
Stylosanthes Guianensis ◽  
Short Day ◽  
Long Day ◽  
Natural Photoperiod ◽  
Low Levels ◽  
Short Days

Seedlings of Stylosanthes guianensis var. guianensis cv. Cook and cv. Endeavour were grown in naturally lit glasshouses at Brisbane (lat. 27� 30' S.) at 35/30, 30/25 and 25/20�C (day/night), and were sown so as to emerge at 18-day intervals from 18 January to 11 June. Cook behaved as a long day-short day plant, with seedlings emerging after 5 February flowering incompletely or remaining vegetative until the experiment was terminated in mid-October. In the 25/20�C regimen flowering was incomplete in Cook; in Endeavour flowering was delayed but a conventional short-day response was observed. At 35/30�C Endeavour flowering was inhibited in the shortest days of mid-winter, suggesting a stenophotoperiodic response, but short days were confounded with low levels of irradiance. Minimum duration of the phase from emergence to floral initiation was c. 66-70 days in Cook and c. 40-45 days in Endeavour; the duration of the phase floral initiation to flower appearance was linearly and negatively related to temperature.

Regulation of the photoperiod-induced cycle in the peripheral blood concentrations of β-endorphin and prolactin in the ram: role of dopamine and endogenous opioids

1990 ◽  
Vol 127 (3) ◽  
pp. 461-469 ◽  
Author(s):  
E. Ssewannyana ◽  
G. A. Lincoln
Keyword(s):  
Plasma Concentrations ◽  
Prolactin Secretion ◽  
Endogenous Opioids ◽  
Fold Change ◽  
Opioid Antagonist ◽  
Light Cycle ◽  
Blood Concentrations ◽  
The Mean ◽  
Short Days

ABSTRACT In a group of adult Soay rams housed indoors under an artificial light cycle of alternating 16-week periods of long and short days, there was a conspicuous longterm cycle in the peripheral plasma concentrations of β-endorphin and prolactin. The levels of β-endorphin were highest under short days and lowest under long days (15-fold change), and inversely related to the changes in the plasma levels of prolactin (120-fold change). The role of dopamine in the control of β-endorphin and prolactin was investigated in a series of experiments, conducted under both long and short days, in which rams were treated with dopamine receptor agonists (dopamine and bromocriptine) and antagonists (pimozide and sulpiride). Naloxone (opioid antagonist) was also administered to assess the additional involvement of endogenous opioids. Dopamine injected i.v. (6·6 mg/kg every 10 min) did not significantly affect the mean plasma concentrations of β-endorphin and prolactin under either long or short days. Pimozide (0·08 mg/kg i.m. every 2 h) caused a large increase in the mean plasma concentrations of β-endorphin and prolactin under long days but not short days. Naloxone (1·6 mg/kg, i.v.), administered alone or in combination with dopamine or pimozide, had no effect on the mean plasma concentrations of β-endorphin and prolactin, except under short days when, combined with pimozide, it induced an increase in the plasma concentrations of the two polypeptides. Bromocriptine (0·06 mg/kg, s.c.) caused a significant decrease in the plasma concentrations of both β-endorphin and prolactin; this effect was most marked at the times of increased secretion (under short days for β-endorphin and under long days for prolactin). Sulpiride (0·59 mg/kg, s.c.) produced the converse effect and caused an increase in the plasma concentrations of β-endorphin and prolactin with the amplitude and duration of the effect varying with the stage of the photoperiod-induced cycle. From these results in the Soay ram, we conclude that dopamine inhibits β-endorphin and prolactin secretion by way of D2 receptors under both long and short days. Endogenous opioids interact with dopamine, augmenting this inhibition under short days. Differences in the acute responses in the secretion of β-endorphin and prolactin, and the inverse relationship between β-endorphin and prolactin during the cycle, indicate that different regulatory systems involving dopamine influence the two pituitary polypeptides. Journal of Endocrinology (1990) 127, 461–469

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