scholarly journals The saccus vasculosus of fish is a sensor of seasonal changes in day length

2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Yusuke Nakane ◽  
Keisuke Ikegami ◽  
Masayuki Iigo ◽  
Hiroko Ono ◽  
Korenori Takeda ◽  
...  
Keyword(s):  
Seasonal Changes ◽  
Day Length ◽  
Saccus Vasculosus

Temperature modulation of photoperiodism and the timing of late-season changes in life history for an aphid, Acyrthosiphon pisum

2011 ◽  
Vol 143 (1) ◽  
pp. 56-71 ◽  
Author(s):  
M.A.H. Smith ◽  
P.A. MacKay ◽  
R.J. Lamb
Keyword(s):  
Sexual Reproduction ◽  
Seasonal Changes ◽  
Acyrthosiphon Pisum ◽  
Late Summer ◽  
Day Length ◽  
Temperature Modulation ◽  
Four Seasons ◽  
Aphid Clone ◽  
Photoperiodic Responses

AbstractWhere winters are severe, aphids reproduce parthenogenetically and viviparously in summer, switch to sexual reproduction in late summer, and produce winter-hardy eggs by the end of the season. The role of day length and temperature in initiating seasonal changes from parthenogenetic to sexual reproduction by pea aphids, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), are described and the selection pressures that affect the timing of this transition are investigated. Over four seasons, a pea aphid clone was sampled from field cages through late summer in southern Manitoba, Canada, and reared in the laboratory to determine the phenotypes of progeny produced as the season progressed. The timing of transitions from one phenotype to another under natural day length and temperature, and the critical day lengths that caused the transitions, coincided with expectations from laboratory studies of photoperiodic responses. Males and mating females appeared later when the weather in August was warm than when it was cool. The timing of seasonal changes was adapted to minimize the physiological time to the end of the season, which maximized the number of asexual summer generations. Ambient temperature modulated the response to day length and fine-tuned the timing of sexual reproduction to adapt for annual variation in autumn weather.

scholarly journals Photoperiodic regulation of prolactin secretion: changes in intra-pituitary signalling and lactotroph heterogeneity

2004 ◽  
Vol 180 (3) ◽  
pp. 351-356 ◽  
Author(s):  
JD Johnston
Keyword(s):  
Environmental Conditions ◽  
Seasonal Changes ◽  
Mammalian Species ◽  
Prolactin Secretion ◽  
Day Length ◽  
Pars Tuberalis ◽  
Photoperiodic Regulation ◽  
Pituitary Lactotroph

Many mammalian species utilise day-length (photoperiod) to adapt their physiology to seasonal changes in environmental conditions, via secretion of pineal melatonin. Photoperiodic regulation of prolactin secretion is believed to occur via melatonin-mediated changes in the secretion of a putative prolactin secretagogue, tuberalin, from the pituitary pars tuberalis. Despite the in vivo and in vitro evidence in support of this intra-pituitary signalling mechanism, the identity of tuberalin has yet to be elucidated. This paper reviews recent advances in the characterisation of tuberalin and the regulation of its secretion. Furthermore, the hypothesis that pituitary lactotroph cells display heterogeneity in their response to changing photoperiod and tuberalin secretion is examined.

scholarly journals Photoperiod-Induced Neuroplasticity in the Circadian System

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Alessandra Porcu ◽  
Malini Riddle ◽  
Davide Dulcis ◽  
David K. Welsh
Keyword(s):  
Seasonal Changes ◽  
Phase Distribution ◽  
Light Exposure ◽  
Brain Regions ◽  
Day Length ◽  
Light Conditions ◽  
Seasonal Adaptation ◽  
Circadian Oscillators ◽  
Plastic Changes ◽  
Mood And Cognition

Seasonal changes in light exposure have profound effects on behavioral and physiological functions in many species, including effects on mood and cognitive function in humans. The mammalian brain’s master circadian clock, the suprachiasmatic nucleus (SCN), transmits information about external light conditions to other brain regions, including some implicated in mood and cognition. Although the detailed mechanisms are not yet known, the SCN undergoes highly plastic changes at the cellular and network levels under different light conditions. We therefore propose that the SCN may be an essential mediator of the effects of seasonal changes of day length on mental health. In this review, we explore various forms of neuroplasticity that occur in the SCN and other brain regions to facilitate seasonal adaptation, particularly altered phase distribution of cellular circadian oscillators in the SCN and changes in hypothalamic neurotransmitter expression.

The effect of daily photoperiod on the wool growth of Merino rams subjected to unrestricted and restricted feeding regimes

1964 ◽  
Vol 4 (13) ◽  
pp. 124 ◽  
Author(s):  
AJ Williams
Keyword(s):  
Body Weight ◽  
Food Intake ◽  
Seasonal Changes ◽  
Period Variation ◽  
Day Length ◽  
Growth Responses ◽  
Significant Treatment ◽  
Significant Period ◽  
Wool Growth ◽  
Daily Food

Twelve adult Merino rams were divided into two groups matched for body weight and previous fleece weights. One group was subjected to a reversed and accentuated rhythm of seasonal changes in day length. The second group received normal seasonal changes in day length (latitude 32�s). There was no temperature control for either group. For eighteen months, these rams were fed a constant ration ad lib. Daily food intakes and wool growth from a tattooed mid-side patch were recorded. Although the periodic differences in wool growth were very highly significant (P<0.001), no well defined rhythm of wool growth was expressed. There was a highly significant treatment x period interaction (P<0.001). Examination of daily food intake values revealed very highly significant period interaction ; due to a positive relation between day length and food intake during part of the eighteen months. In each treatment group, 75 per cent of the period variation in wool growth could be accounted for by variations in food intake. During a further period of fifteen months, when all rams received the same quantity of a constant diet, there was a progressive loss of body weight which amounted to 18 per cent of the initial weight in each group. The wool growth responses of the two groups were similar, and there was no significant interaction term. The very highly significant period variation in wool growth was confined largely to the first three months following the decreased intake. It appears that temperature and day length have little direct effort on wool growth of Merino sheep. However, day length may influence wool growth indirectly through its effect on voluntary food intake.

Effect of seasonal environmental changes on selected reproductive parameters in mares

2021 ◽  
Vol 24 (2) ◽  
pp. 208-218
Author(s):  
Z. Vilhanová ◽  
F. Novotný ◽  
I. Valocký ◽  
V. Hura ◽  
P. Horňáková ◽  
...  
Keyword(s):  
Veterinary Medicine ◽  
Seasonal Changes ◽  
Environmental Changes ◽  
Jugular Vein ◽  
Day Length ◽  
Reproductive Parameters ◽  
Spearman Correlation ◽  
Microsoft Excel ◽  
Average Temperature ◽  
Preovulatory Follicles

The aim of this study was to monitor and evaluate the seasonal changes on selected reproductive parameters in mares. Ninety-six mares of different breeds, aged 3 to 23 years were evaluated during the breeding season 2015–2018 at the Equine clinic at University of Veterinary Medicine and Pharmaco­logy in Košice, Slovakia (48°42´N, 21°15´E). The beginning of the estrus was determined by history or observation, mares were examined every 6 hours, blood for progesterone analysis was taken from the jugular vein. Correlation analyses were performed using both the Pearson and the Spearman correlation coefficient. Statistical analysis was performed using the functions of Microsoft Excel and GraphPad Prism. The day length (r = -0.708, P<0.0001) and the average ambient temperature (r = -0.754, P<0.0001) had a statistically significant effect on the duration of estrus. The shortest estrus was recorded in July with day length of 15 hours 40 minutes at an average temperature of 21.4 ± 0.52 °C, with duration 4.67 ± 0.58 days. The longest estrus was recorded in April with day length of 11 hours 48 minutes at average temperature of 6.9 °C. The environmental factors did not affect the size of the preovulatory follicles, the concentration of progesterone, the internal changes of uterus and the external manifestations of estrus.

scholarly journals Seasonal Changes in Reproductive Productivity, Growth Rate, and Food Intake in Mice Exposed to Different Regimes of day Length and Environmental Temperature

1972 ◽  
Vol 25 (3) ◽  
pp. 627 ◽  
Author(s):  
Pamela R Pennycuik
Keyword(s):  
Growth Rate ◽  
Food Intake ◽  
Constant Temperature ◽  
Productivity Growth ◽  
Seasonal Changes ◽  
Environmental Temperature ◽  
Day Length ◽  
Seasonal Fluctuations

Groups of mice were maintained in three different environments: (1) constant day length and constant temperature; (2) seasonal fluctuations in day length and constant temperature; (3) seasonal fluctuations in day length and seasonal fluctua-tions in temperature.

Suppression of men's responses to seasonal changes in day length by modern artificial lighting

1995 ◽  
Vol 269 (1) ◽  
pp. R173-R178 ◽  
Author(s):  
T. A. Wehr ◽  
H. A. Giesen ◽  
D. E. Moul ◽  
E. H. Turner ◽  
P. J. Schwartz
Keyword(s):  
Urban Environment ◽  
Rectal Temperature ◽  
Seasonal Changes ◽  
Day Length ◽  
Constant Darkness ◽  
Artificial Light ◽  
Active Secretion ◽  
Artificial Lighting ◽  
Natural Photoperiod ◽  
Low Levels

We recently reported that humans have conserved mechanisms, like those that exist in other animals, which detect changes in day length and make corresponding adjustments in the duration of nocturnal periods of secretion of melatonin and of other functions. We detected these responses in individuals who were exposed to artificial "days" of different durations. The purpose of the present study was to determine whether men who are exposed to natural and artificial light in an urban environment at 39 degrees N are still able to detect and respond to seasonal changes in duration of the natural photoperiod. We measured profiles of circadian rhythms during 24-h periods of constant darkness (< 1 lx) and found no summer-winter differences in durations of nocturnal periods of active secretion of melatonin, rising levels of cortisol, high levels of thyrotropin, and low levels of rectal temperature. The results of this and our previous study suggest that modern men's use of artificial light suppresses responses to seasonal changes in the natural photoperiod that might otherwise occur at this latitude.

Seasonal changes in reproductive and pelage status during the initial ‘quiescent’ and first ‘active’ breeding seasons of the peripubertal pony colt

2001 ◽  
Vol 72 (1) ◽  
pp. 55-64 ◽  
Author(s):  
C. McG. Argo ◽  
M.G. R. Collingsworth ◽  
J. E. Cox
Keyword(s):  
Breeding Season ◽  
Seasonal Changes ◽  
Day Length ◽  
Low Concentrations ◽  
Lh Release ◽  
Group 2 ◽  
Plasma Prl ◽  
Breeding Seasons ◽  
Biphasic Profile ◽  
Group 1

AbstractPony colts (~12 m) are generally infertile during the breeding season of mature stallions. The mechanism which ‘delays’ puberty beyond the first potential breeding opportunity has not been described. Four pre- and four post-pubertal colts were monitored from November for 13 (group 1, 6 to 19 months of age) and 9 months (group 2, 18 to 27 months of age). Fortnightly, 15 blood samples were collected at hourly intervals from each colt to determine concentrations of prolactin (PRL), LH, FSH and testosterone (T). Testicular biopsies were collected monthly to evaluate spermatogenic activity. Puberty occurred between 17 and 19 months, and at the onset of the 2-year-old breeding season, all colts were fertile. Seasonal changes in the concentrations of all four hormones were observed in both groups. Prolactin concentrations were correlated with changes in day length (r = 0·88) in both groups, but a biphasic profile was noted in group 1. Moulting of the winter coat was coincident with seasonally increased PRL concentrations (P < 0·001). Seasonal changes in FSH, LH and T concentrations were similarly timed between groups and levels were maximal in mid April, mid March and mid May, respectively. However, overall mean concentrations of LH and T in group 1 animals were only 0·33 and 0·22 of group 2 values (P < 0·001). Suppression of gonadal activity during the colts’ first ‘quiescent’ breeding season was associated with low concentrations of circulating LH. Appropriately timed changes in plasma PRL, FSH and T concentrations and pelage indicated that the photoperiodic mechanism was functional in the pre-pubertal colt but pituitary LH release may be blocked by immaturity or active suppression.

scholarly journals Running on Empty: Of Hypopinealism and Human Seasonality

2021 ◽  
Vol 12 ◽  
Author(s):  
Dieter Kunz ◽  
Amely Wahnschaffe ◽  
Nina Kaempfe ◽  
Richard Mahlberg
Keyword(s):  
Repeated Measures ◽  
Seasonal Changes ◽  
Seasonal Affective Disorder ◽  
Seasonal Pattern ◽  
Pathological Finding ◽  
The Body ◽  
Day Length ◽  
Individual Capacity ◽  
The Individual ◽  
Sleep Length

The pineal hormone melatonin is the natural transducer of the environmental light–dark signal to the body. Although the responsiveness to photoperiod is well-conserved in humans, only about 25 percent of the human population experiences seasonal changes in behavior. As a consequence, humans seem to have adapted—at least partly—to the seasonal changes in day length. The aim of the study was to demonstrate that the individual melatonin deficit marker DOC (degree of pineal calcification) is related to variation of seasonal phenomena in humans. Out of 3,011 patients in which cranial computer tomography (cCT) was performed for diagnostic reasons, 97 consecutive “healthy” subjects (43 female, 54 male; age 18–68 yrs, mean ± SD: 35.0 ± 13.1) were included. Exclusion criteria were pathological finding in cCT, acute/chronic illness including alcohol/drug abuse, shift work, and medication, which are known to influence melatonin excretion. The degree of pineal calcification (DOC) was semiquantitatively determined using the previously validated method. The Seasonal Pattern Assessment Questionnaire (SPAQ) was performed in a telephone interview. Twenty-six subjects fulfilled the criteria for seasonal affective disorder (SAD) or subsyndromal (S) SAD. Seasonality was more pronounced in women than in men (SPAQ seasonality score: 7.8 ± 4.0 vs. 4.9 ± 4.5; p = 0.001) and negatively and significantly associated with age (r = −0.178; p = 0.04). The subjective sleep length significantly varied between seasons (one-way repeated measures ANOVA: F = 45.75; p &lt; 0.0001), with sleep during winter being 53 min (±70 min) longer than during summer. Controlling for age, the total seasonality score was negatively and significantly associated with DOC (r94 = −0.214; p = 0.036). Data confirm earlier studies with respect to distribution of seasonality with sex and age. The survival of seasonality in the sleep length of people living in an urban environment underlines functionality of the circadian timing system in modern societies. Moreover, data confirm for the first time that diminished experience of seasonality in behavior is associated with a reduced individual capacity to produce melatonin.

The effect of sowing date on the growth and yield of three sorghum cultivars in the Ord river valley. I. Agronomic aspects

1977 ◽  
Vol 28 (3) ◽  
pp. 369 ◽  
Author(s):  
AJ Millington ◽  
MIK Whiting ◽  
WT Williams ◽  
CAP Boundy
Keyword(s):  
Grain Yield ◽  
Seasonal Changes ◽  
Sowing Date ◽  
River Valley ◽  
Day Length ◽  
Growth And Yield ◽  
Maximum Temperature ◽  
Wet Season ◽  
Adverse Environmental Conditions ◽  
Sorghum Grain

The main aim of the experiment was to elucidate the causes of low sorghum grain yield in the Ord River valley. Three cultivars were studied: two dwarf, insensitive to day length (the hybrid RS610 and the inbred Meloland) and the day length-sensitive Q7844. The dwarf cultivars showed seasonal changes in time to maturity, but no seasonal changes in grain yield; sowing times need therefore depend only on mechanical difficulties of planting or harvesting in the wet season. Q7844 failed to initiate when the day length was longer than c. 12 hr 10 min, but the yield began to fall well before this day length was attained; a high stable yield was obtained only for sowings between about mid January and mid July. Overall mean yields were: RS610, 4694 kg/ha; Meloland, 4406 kg/ha; Q7844 (stable period only), 5074 kg/ha. Contrary to expectation, the yield of RS610 apparently increased with increase in maximum temperature. Meloland was less sensitive to temperature and to adverse environmental conditions. The causes of occasional yield failures are examined. It is suggested that Meloland deserves more attention than it has hitherto received, and that a dwarf photosensitive line might provide an acceptable 'wet season sorghum' for the Ord.

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