A plastic interval timer synchronizes pubertal development of summer- and fall-born hamsters

2001 ◽  
Vol 281 (5) ◽  
pp. R1613-R1623 ◽  
Author(s):  
Michael R. Gorman
Keyword(s):  
Pubertal Development ◽  
Late Summer ◽  
Day Length ◽  
Late Winter ◽  
Developmental Patterns ◽  
Somatic Development ◽  
Siberian Hamsters ◽  
Interval Timer ◽  
Early Fall ◽  
Time Of Year

Summer and fall decreases in day length induce reproductive regression in adult hamsters and delay reproductive maturation of their young. The following year pubertal development is triggered by an interval timer (IT) that renders animals refractory to inhibitory short day lengths after ∼25 wk. Timing of gonadal and somatic development was examined among offspring born to Siberian hamsters in early-August vs. late-September day lengths. Pubertal maturation was delayed in both groups until late winter. Gonadal growth occurred at significantly later ages among August- vs. September-born males as did late-winter spurts in ponderal growth of both sexes. Timing of reproductive and somatic development depended on postnatal rather than prenatal photoperiod exposure and was unrelated to the circadian entrainment status of dams. When developmental patterns were assessed in relation to time of year, group differences were largely eliminated. Because the IT triggers these developmental events, its duration must be plastic. This plasticity facilitates a relative synchronization or entrainment of developmental milestones in hamsters born into different late-summer/early-fall photoperiods.

scholarly journals Intermediate-duration day lengths unmask reproductive responses to nonphotic environmental cues

2009 ◽  
Vol 296 (5) ◽  
pp. R1613-R1619 ◽  
Author(s):  
Matthew J. Paul ◽  
Jerome Galang ◽  
William J. Schwartz ◽  
Brian J. Prendergast
Keyword(s):  
Pubertal Development ◽  
Late Summer ◽  
Early Spring ◽  
Day Length ◽  
Environmental Cues ◽  
Local Conditions ◽  
Siberian Hamsters ◽  
Reproductive Axis ◽  
And Behavior

Many animals time their breeding to the seasons, using the changing day length to forecast those months when environmental conditions favor reproductive success; in Siberian hamsters ( Phodopus sungorus), long summer days stimulate, whereas short winter days inhibit, reproductive physiology and behavior. Nonphotic environmental cues are also thought to influence the timing of breeding, but typically their effects on reproduction are minor and more variable under categorically long and short photoperiods. We hypothesized that the influence of nonphotic cues might be more prominent during intermediate photoperiods (early spring and late summer), when day length is an unreliable predictor of year-to-year fluctuations in food availability. In hamsters housed in an intermediate photoperiod (13.5 h light/day), two nonphotic seasonal cues, mild food restriction and same-sex social housing, induced gonadal regression, amplified photoperiod history-dependent reproductive responses to decreasing day lengths, and prevented pubertal development indefinitely. These cues were entirely without effect in hamsters maintained under a long photoperiod (16 h light/day). Thus intermediate photoperiods reveal a heightened responsiveness of the reproductive axis to nonphotic cues. This photoperiod-dependent efficacy of nonphotic cues may explain how animals integrate long-term photic and short-term nonphotic cues in nature: intermediate day lengths open a seasonal window of increased reproductive responsiveness to nonphotic cues at a time when such cues may be of singular relevance, thereby allowing for precise synchronization of the onset and offset of the breeding season to local conditions.

Perinatal photoperiod organizes adult immune responses in Siberian hamsters (Phodopus sungorus)

2006 ◽  
Vol 290 (6) ◽  
pp. R1714-R1719 ◽  
Author(s):  
Zachary M. Weil ◽  
Leah M. Pyter ◽  
Lynn B. Martin ◽  
Randy J. Nelson
Keyword(s):  
Immune System ◽  
Immune Function ◽  
Breeding Season ◽  
Somatic Growth ◽  
Developmental Trajectory ◽  
Day Length ◽  
Phodopus Sungorus ◽  
Siberian Hamsters ◽  
Time Of Year ◽  
Induced Changes

Individuals of many nontropical rodent species display reproductive, immunological, and somatic responses to day length. In general, short day (SD) lengths inhibit reproduction and enhance immune function in the laboratory when all other conditions are held constant. Most studies to date have focused on seasonal variation in immune function in adulthood. However, perinatal photoperiods also communicate critical day length information and serve to establish a developmental trajectory appropriate for the time of year. Nontropical rodents born early in the breeding season undergo rapid reproductive development, presumably to promote mating success during their first reproductive season. Rodents born late in the breeding season suspend somatic growth and puberty until the following vernal breeding season. We tested the hypothesis that perinatal day lengths have similar enduring effects on the immune system of rodents. Siberian hamsters ( Phodopus sungorus) were maintained prenatally and until weaning (21 days) in either SDs (8 h light:16 h dark) or long days (LD) (16 h light:8 h dark), then they were weaned into either the opposite photoperiod or maintained in their natal photoperiod, forming four groups (LD-LD, LD-SD, SD-LD, and SD-SD). After 8-wk in these conditions, cell-mediated immune activity was compared among groups. SD-SD hamsters of both sexes enhanced immune function relative to all other groups. The reproductive effects of perinatal photoperiod were not evident by the end of the experiment; circulating testosterone and cortisol sampled at the end of the experiment reflected the postweaning, but not the perinatal photoperiod. This experiment demonstrates long-lasting organizational effects of perinatal photoperiod on the rodent immune system and indicates that photoperiod-induced changes in the immune system are dissociable from changes in the reproductive system.

The biology of Harveyella mirabilis (Cryptonemiales, Rhodophyceae). IV. Life history and phenology

1976 ◽  
Vol 54 (3-4) ◽  
pp. 281-292 ◽  
Author(s):  
Lynda J. Goff ◽  
Kathleen Cole
Keyword(s):  
Water Temperature ◽  
Seawater Temperature ◽  
Environmental Parameters ◽  
Late Summer ◽  
Early Spring ◽  
Day Length ◽  
Late Winter ◽  
Temperature Sensitive ◽  
The North ◽  
The North Pacific

A 20-month field study of the reproductive biology of the parasitic red alga Harveyella mirabilis was undertaken to investigate the effects of environmental parameters on the reproductive periodicity of Harveyella in the intertidal habitat. In the northeast Pacific, tetraspores have been observed in the late winter - early spring; apparently they are produced in response to increased available sunlight and water temperature. Gametogenesis appears to be temperature sensitive; it occurs between a narrow temperature range (9–11 °C). Carpospores are produced in the late summer when both water temperature and day length reach a peak. The phenology of H. mirabilis in the North Atlantic differs from that which is observed in the North Pacific in the timing of gametogenesis and carposporogenesis. The significance of this is discussed in relation to the possible effects of differences in seawater temperature on gametogenesis.

Testicular regression and recrudescence without subsequent photorefractoriness in Siberian hamsters

1995 ◽  
Vol 269 (4) ◽  
pp. R800-R806 ◽  
Author(s):  
M. R. Gorman ◽  
I. Zucker
Keyword(s):  
Adult Male ◽  
Day Length ◽  
Siberian Hamsters ◽  
Testicular Regression ◽  
Interval Timer

Adult male Siberian hamsters transferred from 16 h light/day (16L) to 14 h light/day (14L) underwent gonadal regression and recrudescence over the course of 24 wk; the duration of reproductive quiescence was shorter by 10 wk than in hamsters transferred from 16L to 10L. A decrease in day length (DL) at week 12 from 14L to 10L greatly extended the duration of testicular involution, whereas transfer at week 12 from 10L to 8L was without effect. Hamsters that had manifested gonadal regression and recrudescence in 14L immediately initiated a second regression when challenged with 10L. Intermediate DLs induce gonadal regression and recrudescence without rendering hamsters refractory to shorter DLs. Intermediate DLs sufficient to initiate gonadal regression may be too long to trigger the interval timer that eventually induces refractoriness to shorter DLs and may be successively interpreted as short and long days, respectively, by Siberian hamsters.

scholarly journals Winter ecology of the Porcupine caribou herd, Yukon: Part III, Role of day length in determining activity pattern and estimating percent lying

Rangifer ◽  
1986 ◽  
Vol 6 (2) ◽  
pp. 253 ◽  
Author(s):  
D. E. Russell ◽  
A. M. Martell
Keyword(s):  
Activity Pattern ◽  
Cycle Length ◽  
Day Length ◽  
Late Winter ◽  
Early Winter ◽  
Late Fall ◽  
Early Fall ◽  
The Relationship

Data on the activity pattern, proportion of time spent lying and the length of active and lying periods in winter are presented from a 3 year study on the Porcupine caribou herd. Animals were most active at sunrise and sunset resulting in from one (late fall, early and mid winter) to two (early fall and late winter) to three (spring) intervening lying periods. Mean active/lying cycle length decreased from late fall (298 mm) to early winter (238 min), increased to a peak in mid winter (340 min) then declined in late winter (305 min) and again in spring (240 min). Mean length of the lying period increased throughout the 3 winter months from 56 min m early winter to 114 min in mid winter and 153 min in late winter. The percent of the day animals spent lying decreased from fall to early winter, increased throughout the winter and declined in spring. This pattern was related, in part, to day length and was used to compare percent lying among herds. The relationship is suggested to be a means of comparing quality of winter ranges.

scholarly journals Early fall and late winter diets of migratory caribou in northwest Alaska

Rangifer ◽  
2018 ◽  
Vol 38 (1) ◽  
pp. 27-38 ◽  
Author(s):  
Kyle Joly ◽  
Matthew D. Cameron
Keyword(s):  
Rangifer Tarandus ◽  
Physiological Stress ◽  
Late Summer ◽  
Late Winter ◽  
Winter Habitat ◽  
Pregnant Females ◽  
Winter Diet ◽  
Early Fall ◽  
Forage Type ◽  
Winter Diets

Lichens are the primary winter forage for large herds of migratory caribou (Rangifer tarandus). Caribou select for lichens more than they are available across the landscape and they generally avoid, during winter, habitat that has been burned by wildfires for decades while lichen abundance recovers. However, the relative importance of lichens in the diet is subject to debate. From 2010-2013, we conducted one of the largest microhistological studies of the early fall (58 samples from 1 site) and late winter (338 samples from 58 sites) diets of barren-ground caribou. Lichens con­stituted ~ 71% of the late winter diets of caribou in northwest Alaska, whereas moss (11%) and shrubs (9%) were the next most common forage items. Early fall diets were very similar to late winter, perhaps because deciduous vegetation is senescent during both periods. Diets of males, non-pregnant females and pregnant females were not significantly different. Pregnancy was not associated with the abundance of any forage type during winter but was associated with higher physiological stress. This result was expected as fall body condition dictates conception, caribou are ‘capital’ breeders, and gestation can be energetically demanding. Caribou that migrated south (i.e., wintered south of 67.1°N) had lower levels of nutritional stress, higher levels of lichen in the diet, and lower levels of moss and shrubs compared to caribou that did not migrate south. Future investigations into the potential connection between lichen abundance in the winter diet and survivorship, as well as linking the late summer diets of individuals to their reproductive success, should be undertaken.

scholarly journals Decrease in Enteroviral Meningitis - An Unexpected Benefit of COVID-19 Mitigation?

2020 ◽  
Author(s):  
Kami D Kies ◽  
Amber S Thomas ◽  
Matthew J Binnicker ◽  
Kelli L Bashynski ◽  
Robin Patel
Keyword(s):  
Cerebrospinal Fluid ◽  
Laboratory Testing ◽  
Clinical Microbiology ◽  
Late Summer ◽  
Mitigation Strategies ◽  
Clinical Microbiology Laboratory ◽  
Microbiology Laboratory ◽  
Testing Data ◽  
Early Fall ◽  
Enteroviral Meningitis

Abstract Enteroviral meningitis is seasonal, typically exhibiting a rise in prevalence in late summer/early fall. Based on clinical microbiology laboratory testing data of cerebrospinal fluid, the expected August/September/October peak in enteroviral meningitis did not occur in 2020, possibly related to COVID-19 mitigation strategies.

scholarly journals Seasonal population dynamics of Octopus vulgaris in the eastern Mediterranean

2006 ◽  
Vol 63 (1) ◽  
pp. 151-160 ◽  
Author(s):  
Stelios Katsanevakis ◽  
George Verriopoulos
Keyword(s):  
Eastern Mediterranean ◽  
Late Summer ◽  
Main Peak ◽  
Octopus Vulgaris ◽  
Late Winter ◽  
Visual Census ◽  
The Common ◽  
Specific Growth Rates ◽  
Seasonal Population ◽  
Seasonal Population Dynamics

Abstract The population density of Octopus vulgaris was measured by visual census with scuba diving in coastal areas in Greece (eastern Mediterranean). A time-variant, stage-classified, matrix population model was developed to interpret the seasonal variation of octopus stage densities and to estimate several life cycle parameters. An annual and a semi-annual periodic cycle were found in the stage densities. A main peak of benthic settlement was observed during summer and a secondary, irregular one during late autumn. Two spawning peaks were estimated, a main one during late winter–spring and a secondary one during late summer–early autumn. More than 50% of the just-settled individuals will eventually die after 3 months. Mortality rate declines, as individuals grow larger, reaches a minimum approximately 6 months after settlement, and then grows again probably because of terminal spawning. The life expectancy of recently settled individuals (<50 g) during their summer peak is approximately 5 months. The lifespan of the common octopus is estimated to be between 12 and 15 months. The octopuses' mean specific growth rates (±s.d.) in their natural environment were 1.61 ± 0.30 d−1 for 50–200 g individuals and 1.19 ± 0.31 d−1 for 200–500 g individuals.

Impact of extrafloral nectar availability and plant genotype on ant (Hymenoptera: Formicidae) visitation to quaking aspen (Salicaceae)

2015 ◽  
Vol 148 (1) ◽  
pp. 36-42 ◽  
Author(s):  
Jonathon R. Newman ◽  
Diane Wagner ◽  
Patricia Doak
Keyword(s):  
Populus Tremuloides ◽  
Late Summer ◽  
Early Summer ◽  
Quaking Aspen ◽  
Plant Genotype ◽  
Free Living ◽  
Natural Induction ◽  
Formica Fusca ◽  
Time Of Year ◽  
Nectar Availability

AbstractFor quaking aspen (Populus tremuloides Michaux; Salicaceae) the rate of extrafloral (EF) sugar secretion is increased by defoliation and decreased by drought. Although wholesale blocking of EF nectar has been shown to reduce ant (Hymenoptera: Formicidae) visitation to aspen, the effect of more subtle and realistic variations in nectar availability on ant recruitment is unknown. Working in Alaskan boreal forest (United States of America), we reduced and supplemented EF nectar availability on potted aspen ramets of three genotypes and surveyed visitation by free-living Formica fusca (Linnaeus) (Hymenoptera: Formicidae). Ants were more responsive to a subtle increase in sugar availability than to a decrease. While nectar reduction had no effect on ant visitation, nectar supplementation increased ant visitation to one aspen genotype by 70% during an early summer trial. Average ant visitation to different aspen genotypes varied during the late summer, indicating that aspen genotype can influence attractiveness to ants. We conclude that natural induction of EF secretion in response to herbivory may benefit aspen through improved ant recruitment, though the response is dependent on aspen genotype and time of year. Differences among aspen genets in attractiveness to ants could influence the relative success of genotypes, especially in settings in which aspen regenerates from seed.

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