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Long Photoperiod (long + photoperiod)
Selected AbstractsSeasonal changes in wing dimorphism of the lygaeid bug Dimorphopterus japonicus (Heteroptera: Lygaeidae) in relation to environmental factorsENTOMOLOGICAL SCIENCE, Issue 2 2003Rikiya SASAKI Abstract The lygaeid bug Dimorphopterus japonicus Hidaka, which mainly feeds on a eulalia, Miscanthus sinensis, shows marked wing dimorphism of brachyptery and macroptery. Its production of macropters is stimulated in rearing conditions such as high temperature, long photoperiod and crowding during the nymphal stage. In this study, we investigated the seasonal prevalence in occurrence and the seasonal change in incidence of macroptery in D. japonicus for field populations in Okayama, western Japan. The results demonstrated that nymphal density was a key factor in determining the proportion of macropters, indicating an escape strategy from crowded populations. The field surveys also revealed that this bug has a univoltine life cycle in Okayama. There was a seasonal change in the incidence of macroptery in the new generation. The combined effects of temperature and photoperiod on wing-form determination explained this seasonality trait. [source] The effects of delaying the start of moult on the duration of moult, primary feather growth rates and feather mass in Common Starlings Sturnus vulgarisIBIS, Issue 3 2004Alistair Dawson In many species of birds there is a close relationship between the end of breeding and the start of moult. Late-breeding birds therefore often start to moult late, but then moult more rapidly. This is an adaptive mechanism mediated by decreasing day lengths that allows late-breeding birds to complete moult in time. This study asked how these birds complete moult of the primary feathers more rapidly, and the consequences of this on the mass of primary feathers. Common Starlings Sturnus vulgaris were induced to moult rapidly in one of two ways. In the first experiment, one group was exposed to artificially decreasing photoperiods from the start of moult, whereas the control group remained on a constant long photoperiod. The second experiment was a more realistic simulation. Two groups were allowed to moult in an outdoor aviary. One group started to moult at the normal time. In the other, the start of moult was delayed by 3 weeks with an implant of testosterone. The duration of moult was significantly reduced in both the group experiencing artificially decreasing photoperiods and the group in which the start of moult was delayed. The faster moult rate was achieved by moulting more feathers concurrently. The rate of increase in length of each of the primary feathers, and their final length, did not differ between groups. The rate at which total new primary feather mass was accumulated was greater in more rapidly moulting birds, but this was insufficient to compensate for the greater numbers of feathers being grown concurrently. Consequently, the rate of increase in mass of individual feathers, and the final feather mass, were less in the rapidly moulting birds. A 3-week delay in the start of moult is not an unrealistic scenario. That this caused a measurable decrease in feather mass suggests that late-breeding birds are indeed likely to suffer a real decrease in the quality of plumage grown during the subsequent moult. [source] Effects of photoperiod and temperature on the development and diapause of the bark beetle Ips typographusJOURNAL OF APPLIED ENTOMOLOGY, Issue 3 2007P. Dole Abstract:, Diapause was induced in a Central European population of Ips typographus grown at 20°C when the day length decreased below 16 h [50% diapause incidence occurred in the 14.7:9.3 h L:D (light:dark) regime]. The non-diapausing adults fed on days 2,6 and 10,14 after the ecdysis and swarmed after the second feeding bout with chorionated eggs in the ovaries and sperm in the spermiducts. Neither gonads nor the flight muscles matured and no swarming occurred in the diapausing adults. The development from egg to adult took about 34 days in both 18:6 h (no diapause) and 12:12 h L:D (diapause) regimes, but it was extended by up to 30% without diapause induction when only larvae or pupae were exposed to L:D 12:12 h. Diapause was induced in insects reared at L:D 12:12 h through the last larval and the pupal instars and/or in the adult stage. Temperature , 23°C prevented diapause induction at L:D 12:12 h but diapause occurred at L:D 14:10 h associated with 26:6°C thermoperiod. The effect of thermoperiods on the developmental rate requires further research. Exposure of the non-diapausing adults to 5°C for several days blocked feeding and evoked a diapause-like state, whereas diapausing adults fed and their gonads slowly developed at this temperature. Diapausing adults exposed in forest to low night temperatures and transferred in October to 20°C readily reproduced at 18:6, but not 12:12 h L:D photoperiods. After 2-months at 5°C and darkness, they became insensitive to the photoperiod, matured and most of them also swarmed at 20°C in the 12:12 h L:D regime. In a Scandinavian population, diapause occurred at 18:6 h L:D and was terminated either by exposure to 5°C or by very long photoperiod (L:D 20:4 h) combined with high temperature (23°C). [source] Effects of photoperiod on the reproductive condition of Nile grass rats (Arvicanthis niloticus) from an equatorial populationAFRICAN JOURNAL OF ECOLOGY, Issue 3 2002Scott Nunes Abstract We evaluated the effects of photoperiod on the reproductive condition of male and female Nile grass rats (Arvicanthis niloticus) descended from members of an equatorial population trapped 2°S of the equator. Study animals housed in 12:12 light:dark (LD) cycles were transferred either to short photoperiod (9:15) or long photoperiod (15:9) for 9 weeks (males) or 11 weeks (females), and various reproductive parameters were assessed. We observed no differences between short- and long-day males with respect to plasma concentration of testosterone, testicular mass, seminal vesicle mass, or spermatogenesis. Similarly, we observed no differences between short- and long-day females with respect to oestrous cycles, uterine mass, follicle size, or presence of corpora lutea. Reproductive parameters of male and female A. niloticus housed in short- and long photoperiods were similar to those typically observed among animals descended from the same equatorial population and housed in LD 12:12. Thus, photoperiod appears not to elicit changes in reproductive condition among A. niloticus from populations whose native habitat lies within 2° of the equator. These data contrast with the results of other studies indicating that photoperiod alters reproductive condition in A. niloticus populations living >10° from the equator. Résumé Nous avons étudié les effets de la photopériode sur la condition reproductive des mâles et des femelles des rats Arvicanthis niloticus, issus de membres d'une population équatoriale attrapée à 2° au sud de l'Equateur. Les animaux de l'étude soumis à des cycles 12 : 12 lumière : obscurité (LD) ont été transférés dans des conditions de photopériodes courtes (9 : 15) ou longues (15 : 9) pendant 9 semaines (mâles) ou 11 semaines (femelles), et on a étudié les différents paramètres de la reproduction. Nous n'avons constaté aucune différence entre les mâles soumis aux jours longs ou courts, en ce qui concerne la concentration de testostérone dans le plasma, le poids des testicules, celui de la vésicule séminale ou la spermatogenèse. De même, nous n'avons observé aucune différence entre les femelles soumises aux jours longs ou courts en ce qui concerne le cycle oestral, le poids de l'utérus, la taille des follicules ou la présence de corps jaune. Les paramètres reproducteurs des A. niloticus mâles et femelles soumis à des photopériodes longues ou courtes étaient semblables à ceux que l'on observe classiquement chez les animaux issus de cette même population équatoriale et logés dans des conditions LD 12 : 12. Il semble donc que la photopériode ne suscite aucun changement de l'état reproductif chez les A. niloticus issus de populations dont l'habitat original se situe à 2° sous l'Equateur. Ces données sont en contradiction avec les résultats d'autres études qui montraient que la photopériode altère l'état reproductif des populations de A. niloticus vivant à plus de 10° de l'Equateur. [source] Photoperiod at conception predicts C677T-MTHFR genotype: A novel gene-environment interactionAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 4 2010Mark Lucock Data is presented, which suggest that the day length a woman experiences during the periconceptional period predicts the C677T-MTHFR genotype of her child. Logistic regression analysis involving 375 neonates born in the same geographical location within a three year period demonstrated that photoperiod (minutes) at conception predicts both genotype (P = 0.0139) and mutant allele carriage (P = 0.0161); the trend clearly showing that the 677T-MTHFR allele frequency increases as photoperiod increases. We propose a number of explanations, including a hypothesis in which a long photoperiod around conception decreases maternal systemic folate because of UVA induced dermal oxidative degradation of 5-methyl-H4folate, leading to a lower cellular 5,10-methylene-H4folate status. In this scenario, 5,10-methylene-H4folate would be more efficiently used for dTMP and DNA synthesis by 677T-MTHFR embryos than wildtype embryos giving the 677T-MTHFR embryos increased viability, and hence increasing mutant T-allele frequency. Alternate hypotheses include: increased seasonal availability of folate rich foods that genetically buffer any negative effect of 677T-MTHFR in embryos; seasonal oxidative stress lowering embryo-toxic homocysteine; an undefined hormonal effect of photoperiod on the neuroendocrine axis, which mediates genotype/embryo selection. The effect of photoperiod on genotype seems clear, but the speculative molecular mechanism underpinning the effect needs careful examination. Am. J. Hum. Biol., 2010. © 2010 Wiley-Liss, Inc. [source] Effect of the Photoperiod and Administration of Melatonin on the Pars Tuberalis of Viscacha (Lagostomus maximus maximus): An Ultrastructural StudyTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 5 2010Edith Perez Romera Abstract The pituitary pars tuberalis (PT) is a glandular zone exhibiting well-defined structural characteristics. Morphologically, it is formed by specific secretory cells, folliculostellate cells, and migratory cells coming from the pars distalis. The purpose of this work was to investigate differences in specific cellular characteristics in the PT of viscachas captured in summer (long photoperiod) and winter (short photoperiod), as well as the effects of chronic melatonin administration in viscachas captured in summer and kept under long photoperiod. In summer, the PT-specific cells exhibited cell-like characteristics with an important secretory activity and a moderate amount of glycogen. In winter, the PT-specific granulated cells showed ultrastructural variations with signs of a reduced synthesis activity. Also, PT showed a high amount of glycogen and a great number of cells in degeneration. After melatonin administration, the ultrastructural characteristics were similar to those observed in winter, but the amount of glycogen was higher. These results suggest possible functional implications as a result of morphological differences between long and short photoperiods, and are in agreement with the variations of the pituitary-gonadal axis, probably in response to the natural photoperiod changes through the pineal melatonin. The ultrastructural differences observed in PT, after melatonin administration, were similar to those observed in the short photoperiod, thus supporting the hypothesis that these cytological changes are induced by melatonin. Anat Rec, 293:871,878, 2010. © 2010 Wiley-Liss, Inc. [source] Effects of photoperiod on the reproductive condition of Nile grass rats (Arvicanthis niloticus) from an equatorial populationAFRICAN JOURNAL OF ECOLOGY, Issue 3 2002Scott Nunes Abstract We evaluated the effects of photoperiod on the reproductive condition of male and female Nile grass rats (Arvicanthis niloticus) descended from members of an equatorial population trapped 2°S of the equator. Study animals housed in 12:12 light:dark (LD) cycles were transferred either to short photoperiod (9:15) or long photoperiod (15:9) for 9 weeks (males) or 11 weeks (females), and various reproductive parameters were assessed. We observed no differences between short- and long-day males with respect to plasma concentration of testosterone, testicular mass, seminal vesicle mass, or spermatogenesis. Similarly, we observed no differences between short- and long-day females with respect to oestrous cycles, uterine mass, follicle size, or presence of corpora lutea. Reproductive parameters of male and female A. niloticus housed in short- and long photoperiods were similar to those typically observed among animals descended from the same equatorial population and housed in LD 12:12. Thus, photoperiod appears not to elicit changes in reproductive condition among A. niloticus from populations whose native habitat lies within 2° of the equator. These data contrast with the results of other studies indicating that photoperiod alters reproductive condition in A. niloticus populations living >10° from the equator. Résumé Nous avons étudié les effets de la photopériode sur la condition reproductive des mâles et des femelles des rats Arvicanthis niloticus, issus de membres d'une population équatoriale attrapée à 2° au sud de l'Equateur. Les animaux de l'étude soumis à des cycles 12 : 12 lumière : obscurité (LD) ont été transférés dans des conditions de photopériodes courtes (9 : 15) ou longues (15 : 9) pendant 9 semaines (mâles) ou 11 semaines (femelles), et on a étudié les différents paramètres de la reproduction. Nous n'avons constaté aucune différence entre les mâles soumis aux jours longs ou courts, en ce qui concerne la concentration de testostérone dans le plasma, le poids des testicules, celui de la vésicule séminale ou la spermatogenèse. De même, nous n'avons observé aucune différence entre les femelles soumises aux jours longs ou courts en ce qui concerne le cycle oestral, le poids de l'utérus, la taille des follicules ou la présence de corps jaune. Les paramètres reproducteurs des A. niloticus mâles et femelles soumis à des photopériodes longues ou courtes étaient semblables à ceux que l'on observe classiquement chez les animaux issus de cette même population équatoriale et logés dans des conditions LD 12 : 12. Il semble donc que la photopériode ne suscite aucun changement de l'état reproductif chez les A. niloticus issus de populations dont l'habitat original se situe à 2° sous l'Equateur. Ces données sont en contradiction avec les résultats d'autres études qui montraient que la photopériode altère l'état reproductif des populations de A. niloticus vivant à plus de 10° de l'Equateur. [source] | ||||||||||||||||||||||