Persistency of egg production of common coturnix is affected by early light regimens

The quantity and quality of light during the growing period was studied in 3 experiments to determine the effect on subsequent egg production of $\text{Coturnix}$$\text{coturnix}$$\text{japonica}$. Females were individually caged and kept in climatic chambers. Either short days (LD 8:16), or long days (LD 16:8) were given from hatching until 10 weeks of age. Later the birds were exposed to short and long light periods of 6 weeks duration alternately, until 34 or 36 weeks of age. Parameters measured were age at first egg, total egg production, and rate of lay under LD 8:16.Although no treatment resulted in all of the birds of a group being persistent layers, rearing on short-days, blinding and fluorescent light each contributed to persistency in adults. Early light regimens in coturnix are important in establishing persistency of egg production performances as adults.     

First feeding of Atlantic salmon (Salmo salar L.) under different photoperiods

Juvenile Atlantic salmon ( Salmo salar L. ) were first fed under four different static photoperiods (LD 24:0, LD 21:3, LD 18:6, LD 12:12) in two experiments. Under LD 24:0, continuous feeding or feeding 12 hours per day did not affect growth rate. In both experiments the roup on continuous light (LD 24:0) had highest growth rate. Growth was reduced on reduced dayfength. It is suggested that the difference in growth between long day (LD 21:3) and continuous light (LD 24:0) was caused by a growth inhibition during the dark period.

Zusammenfasung

Erste Nahrung des Atlantischen Lachses (Salmo salar L .)
Jungfische des atlantischen Lachses ( Salmo ralar L. ) wurden unter vier verschiedenen Photoperioden in zwei Experimenten erstmals gefüttert (LD 24:0; LD 21:3; LD 18:6; LD 12:12). Bei kontinuierlicher Fütterung (LD 24:0) oder Fütterung über 12 Stunden pro Tag, war die Wachsturnsrate nicht beeinflußt. In beiden Exerimenten hatte die Gruppe, die unter durchgehender Beleuchtung aufgezogen wurde, die höchste Wacgstumsrate. Das Wachsturn war bei kürzerer Tageslänge reduziert. Aus den Daten wird geschlossen, daß die Differenz im Wachstum zwischen dem Langtag (LD 21:3) und der durchgehenden Beleuchtung (LD 24:0) durch eine Wachtumshemmung während der Dunkelzeit verursacht wurde.     

The adult eclosion rhythm in Hyphantria cunea (Lepidoptera: Arctiidae): Endogenous and exogenous light effects

Abstract

Endogenous and exogenous effects of light on adult eclosion in Hyphantria cunea were tested by exposure to various light regimes. Regression analysis showed that the position of the eclosion peak after lights on was proportional to the length of the photophase, and that the peak was influenced by the timing of both lights‐on and lights‐off. Under photoperiods of 2–12 hours LD cycle, the eclosion peak was situated after lights‐off, but moved into the light phase as the photophase increased to 22 hours. Pupae were exposed to 3 “skeleton”; photoperiods of LDLD2:2:6:14, 4:2:4:14 and 6:2:2:14. Under the first of these, most adults emerged at the start or just before the longest dark period. Under the second and third skeleton regimes, 20% and 70% respectively of pupae emerged during the shorter dark period. When the compound eyes of the pharate adults were covered, adults smerged 1–4 hours before lights‐off under LD10:14, compared to a control group which emerged just after lights‐off. When pupae were transferred from LD to LL or DD conditions, the eclosion peak occurred approximately every 24 hours after the last LD peak. Results suggest that light received by the compound eyes influences the eclosion rhythm, either through an exogenous masking effect, or by altering the phase of the pacemaker controlling eclosion.     

Effects of delta 9-THC on growth hormone and ACTH secretion in rats

In three separate experiments adult male BALB/C or AJAX mice were housed for 3 weeks in a room equipped with a regulated 12:12 LD lighting regime. These animals were provided with food and water $\text{ad libitum}$. At the end of 3 weeks these animals were sacrificed in groups of 6 at 4 hour intervals over a 24 hour period, and the levels of serotonin and 5-HIAA were quantitated in the cerebral cortex of each animal. Significant daily changes in the content of both serotonin and 5-HIAA were demonstrated. In confirmation of earlier investigations, serotonin content was elevated late in the dark phase or in the early hours of the light phase. The pattern of changes in the level of 5-HIAA did not correlate well with that observed for serotonin. 5-HIAA content was usually elevated just before the onset of the dark phase or during the early hours of the dark phase. These data suggest that serotonergic neurons in the cerebral cortex may be more active in the early hours of the dark phase.     

Temperature regulation in the mouse,Peromyscus leucopus: Effects of various photoperiods,pinealectomy and melatonin administration

The white-footed mouse,Peromyscus leucopus, exhibits two responses to a decreasing series of photoperiods. The winter molt and reproductive regression occur in mice maintained on a photoperiods of 12 hours of light per day or less. Daily torpor and weight of lipid-free brown fat increase gradually between photoperiods of LD 13:11 — LD 12:12 and LD 10:14 — 9:15 LD. Pinealectomized mice maintained on a LD 9:15 photoperiod fail to exhibit the extent of daily torpor and increased nesting which are characteristic of sham-operated animals. Replacement therapy with chronically implanted beeswax pellets containing 3 mg of melatonin reverses the effects of pinealectomy.Presented at the Eighth International Congress of Biometeorology, 9–14 September 1979, Shefayin, Israel.     

Daily light regulates seasonal responses in the migratory male redheaded bunting (Emberiza bruniceps)

This study analyzed the role of day length in regulation of seasonal body fattening and testicular growth in a latitudinal Palaearctic-Indian migrant, the redheaded bunting (Emberiza bruniceps). When exposed to increasing photoperiods (hours of light: hours of darkness; 11.5L:12.5D, 12L:12D, 12.5L:11.5D, 13L:11D, 14L:10D, and 18L:6D) for 9-12 weeks, buntings responded in a photoperiod-dependent manner and underwent growth and regression cycle under photoperiods of > or =12 hr per day. Also, the response to a long photoperiod of birds that were held under natural photoperiods at 27 degrees N for 2 years was similar to those who arrived the same year from their breeding grounds ( approximately 40 degrees N), suggesting that the experience of higher amplitude day-night (light-dark, LD) cycles during migratory and breeding seasons were not critical for the subsequent response (initiation-termination-reinitiation) cycle. Another experiment examined entrainment of the circadian photoperiodic rhythm in buntings by subjecting them to T=24+/-2 hr LD-cycles with 8 hr photophase and to T=22 and 24 hr with 11 hr photophase. The results showed a reduction in critical day length under T=22 hr LD-cycle. In the last experiment, we constructed an action spectrum for photoperiodic induction by exposing birds for 4.5 weeks to 13L:11D of white (control), blue (450 nm), or red (640 nm) light at irradiances ranging from 0.028 to 1.4 W m(-2). The threshold light irradiance for photoinduction was about 10-fold higher for blue light, than for red and white lights. These results conclude that the daily light of the environment regulates the endogenous program that times seasonal responses in body fattening and testicular cycles of the redheaded bunting.     

Support for a rare pattern of temperature-dependent sex determination in archaic reptiles: evidence from two species of tuatara (Sphenodon)

Background

In many birds, day length (=photoperiod) regulates reproductive cycle. The photoperiodic environment varies between different seasons and latitudes. As a consequence, species at different latitudes may have evolved separate photoperiodic strategies or modified them as per their adaptive need. We studied this using house sparrow as a model since it is found worldwide and is widely investigated. In particular, we examined whether photoperiodism in house sparrows (Passer domesticus) at 27°N, 81°E shared features with those exhibited by its conspecifics at high latitudes.

Results

Initial experiment described in the wild and captive conditions the gonad development and molt (only in captives) cycles over a 12-month period. Both male and female sparrows had similar seasonal cycles, linked with annual variations in day length; this suggested that seasonal reproduction in house sparrows was under the photoperiodic control. However, a slower testis and attenuated follicular growth among captives indicated that other (supplementary) factors are also involved in controlling the reproductive cycle. Next experiment examined if sparrows underwent seasonal variations in their response to stimulatory effects of long day lengths. When birds were transferred every month over a period of 1 year to 16 hours light:8 hours darkness (16L:8D) for 17–26 weeks, there was indeed a time-of-year effect on the growth-regression cycle of gonads. The final experiment investigated response of house sparrows to a variety of light-dark (LD) cycles. In the first set, sparrows were exposed for 31 weeks to photoperiods that were close to what they receive in between the period from sunrise to sunset at this latitude: 9L:15D (close to shortest day length in December), 12L:12D (equinox, in March and September) 15L:9D (close to longest day length in June). They underwent testicular growth and regression and molt in 12L and 15L photoperiods, but not in 9L photoperiod. In the second set, sparrows were exposed for 17 weeks to photoperiods with light periods extending to different duration of the daily photosensitivity rhythm (e.g. 2L:22D, 6L:18D, 10L:14D, 14L:10D, 18L:6D and 22L:2D). Interestingly, a slow and small testicular response occurred under 2L and 10L photoperiods; 6L:18D was non-inductive. On the other hand, 14L, 18L and 22L photoperiods produced testicular growth and subsequent regression response as is typical of a long day photostimulation.

Conclusion

Subtropical house sparrows exhibit photoperiodic responses similar to that is reported for its population living at high latitudes. This may suggest the conservation of the photoperiodic control mechanisms in birds evolved over a long period of time, as a physiological strategy in a temporally changing environment ensuring reproduction at the best suited time of the year.     

Effect of photoperiod on incubation period in a wild passerine,Sylvia atricapilla

Time required for avian embryos to develop is influenced by incubation temperature and the amount of time adults incubate eggs. Experiments on poultry indicate that photoacceleration, the light‐induced stimulation of embryonic development, decreases the length of the incubation period as embryos receive more light. We hypothesized that eggs of wild birds exposed to longer periods of light should also have shorter incubation periods. We tested whether photoacceleration would occur in a species of open‐cup nesting passerine, the blackcap Sylvia atricapilla. We artificially incubated blackcap eggs under four different photoperiods, four hours of light (4L) and 20 h of dark (20D), 12L:12D, 20L:4D, and a skeleton photoperiod (1 h light, 2 times per day) that framed a 20 h day. While incubation periods were accelerated with increasing photoperiod length, the differences among photoperiods of 4, 12 and 20L were weak. Embryos exposed to skeleton photoperiods developed as fast as those exposed to 20L and significantly faster than those exposed to 4L and 12L treatments. Skeleton photoperiods may most closely approximate natural patterns of light exposure that embryos experience during dawn and dusk incubation recesses typically associated with adult foraging. If our results from this species also occur in other wild birds, exposure to different day lengths may help explain some of the variation in the observed seasonal and latitudinal trends in avian incubation period.     

Influence of Photoperiod, Daylength, and Feeding Schedule on Tadpole Growth and Development

The metamorphic rate of Rana pipiens tadpoles was studied under different photoperiods, daylengths, and feeding schedules. Tail resorption and hindlimb growth and development induced by immersion in 30 μg/l thyroxine (T₄) were accelerated under longer photoperiods and continuous light when 6L: 18D, 12L: 12D, 18L: 6D, and 24L regimes were compared. Constant light exposure did not produce faster development than an 18 hr photoperiod, and initially was less effective. The rate of spontaneous and T₄-induced metamorphosis was greater the shorter the day on 9L:9D, 12L: 12D, or 15L: 15D cycles, although all groups received the same overall amount of light, but in different dosages. When feeding schedule but not the LD cycle was varied, groups of tadpoles fed on 18, 24, or 30 hr regimes showed no differences in growth and development rate on 19L: 5D, and only random variations under continuous light. Differences in metamorphic rate on 18, 24, or 30 hr days are not due to the feeding schedules, but to the LD cycles. From these experiments we conclude that illumination, particularly the length and frequency of the photoperiod, affects the utilization of T₄. Development rates independent of the total amount of illumination, but related to daylength and light schedule, suggest interaction of light with an endogenous timing mechanism.     

Functional maturation of the gonads of Turkish hamsters under various photoperiods

The golden hamster, Mesocricetus auratus, is the only photoperiodic rodent to date that has been shown to fail to respond to inhibitory (i.e., short, less than 12.5 h/day) photoperiods until after pubertal onset. In other photoperiodic hamsters, mice, and voles, short photoperiods greatly retard gonadal maturation. The Turkish hamster, Mesocricetus brandti, is a photoperiodic rodent that as an adult is reproductively competent only on photoperiods of 15-17 h of light per day; photoperiods of less than 15 or greater than 17 h of light promote gonadal regression. In this report we addressed two questions: a) are prepubertal M. brandti photoperiodic, and b) if so, is gonadal maturation enhanced or suppressed by exposure to photoperiods of greater than 17 h of light per day? Turkish hamsters were raised on photoperiods of 12, 16, 20, or 24 (= LL) h of light per day. Testicular growth was retarded for 16 wk by 12L:12D. Very long days, 20L:4D, or LL did not retard testicular development. In females, pubertal onset, as indicated by first vaginal estrus, was delayed in young raised on 12L:12D and in 2 of 18 and 4 of 19 young raised on 20L:4D and LL, respectively. These results demonstrate that prepubertal Turkish hamsters are photoperiodic, but respond differently from adults to photoperiods greater than 17 h of light per day.     

Effects of light (photoperiod,spectral composition) on the population dynamics of Tisbe holothuriae Humes (Copepods,Harpacticoida)

The harpacticoid copepod Tisbe holothuriae Humes was reared for several generations under different photoperiods (white light) and spectral quality (continuous illumination). The main life cycle parameters were measured and demographic variables were determined. Development time was retarded under green wavelengths and at photoperiods different from LD 12:12, especially under continuous white light. Total body length of females and males was shortest under LD 12:12 and longest under constant dark. Photoperiods different from LD 12:12 prolonged the interval between broods of egg sacs. Short photoperiods caused higher abortion rate, while long photoperiods retarded the maturation time of the egg sacs. Red wavelengths stimulated the abortion rate. Photoperiod LD 12:12 and blue wavelengths increased the production of offspring and the life span of females. Highest intrinsic rates of natural increase were estimated under LD 12:12 (rm =0.304) and blue wavelengths (rm = 0.254). These light conditions proved the most favourable for rearing Tisbe holothuriae.     

The influence of light wavelength on reproductive photorefractoriness in migratory blackheaded bunting (Emberiza melanocephala).

There are two effects of long day length on reproductive responses in birds, one is the photoinduction of gonadal growth and maturation and the other is the induction of gonadal regression and photorefractoriness. Although it is likely that the same photoreceptors are involved in the photoinduction of gonadal growth and the onset and maintenance of photorefractoriness. and so the influence of wavelength should be similar, this has not been investigated. Therefore, we investigated the influence of light wavelength on reproductive photorefractoriness in the migratory male blackheaded bunting held under long photoperiods. In mid May, when photoperiod was approximately 14L:10D (14 hours light:10 hours darkness), eight groups of sexually mature birds were moved indoors on an artificial photoperiod of 14L:10D (L - 450 lux. D - 0 lux). Then after 3 weeks, for six groups, a 4-h light period in the morning (zt 0-4; zt 0 [zeitgeber time 0] refers to the beginning of lights-on period) or in the evening (zt 10-14) was substituted with green (428 nm), red (654 nm) or white light at 16 +/- 2 lux intensity. Of the remaining two groups, one was maintained on 14L: 10D and the other transferred to 10L:14D: these served as controls. At the end of 4 weeks, all birds were found to have undergone testicular regression, irrespective of LD cycle they were exposed to. When these gonadally regressed birds were subjected to 16L:8D for another 4 weeks, to test their responsiveness to the stimulatory effects of long day lengths, only those exposed to 10L:14D and 14L:10D with a 4-h green light period showed testicular regrowth. On the other hand, birds exposed to 14L:10D with a 4-h white or red light period remained fully regressed, similar to 14L:10D controls. Except for some individual difference, there was no difference in response between the groups that received a 4-h light period in the morning and that received it in the evening. These results suggest that the wavelengths of light influence induction of buntings from the photosensitive state into the photorefractory state. Whereas the short light wavelengths facilitated recovery from the photorefractoriness, the long light wavelengths were more effective in maintaining the photorefractoriness.     

Effects of lighting programs on onset of the ovulatory season in mares

Using 240 pony mares, lighting regimens were tested for their efficiency in hastening the onset of the ovulatory season. The mean number of days from January 1 to first ovulation was used as the end point. No advantage was gained by beginning a fixed lighting regimen ($\text{15.5L}\text{8.5D}$, hours light/hours dark) November 1 (66 ±8) versus December 1 (65 ±9), but beginning on January 1 was less efficient (98 ±8; controls, 132 ±5; P<0.05). In another experiment, daily three-hour interruptions of either the light phase (67 ±10) or the dark phase (71 ±11) did not significantly retard the effectiveness of a fixed regimen of $\text{15L}\text{9D}$ (54 ±5; controls, 142 ±6). A $\text{15L}\text{9D}$ regimen every other day (natural day length on alternate days) resulted in an interval (85 ±7) that was shorter (P<0.05) than for the controls and longer (not significant) than for the daily $\text{15L}\text{9D}$ regimen. When used with natural day length, a one-hour pulse of light in the evening (15 hours after sunrise) was not effective (141 ±6); a one-hour pulse in the morning 9.5 hours after sunset) was only partially effective (117 ±6). In another experiment, the interval was reduced (P<0.05) in a group with one hour of light fixed at 4:00 a.m. with natural day length (85 ±8; $\text{15L}\text{9D}$, 75 ±7; controls, 126 ±9). Results indicated that a fixed one-hour pulse of light at 4 a.m., used with natural day length, may provide an acceptable level of stimulation.     

Androgen metabolism by rat epididymis. 1. Metabolic conversion of 3 H-testosterone in vivo

The epididymis of adult rats metabolize ³H-testosterone by experiments $\text{in vivo}$. Thirty minutes after the injection of 100 μCi ³H-testosterone, some 10 per cent of the total radioactivity of the epididymis was found in the water-soluble fraction, whereas 90 per cent was found in the ether soluble fraction (free steroids). The free steroids were examined further and the following androgenic metabolites identified: $\text{testosterone}$ (17β-hydroxy-4-androsten-3-one) 8, 9%, $\text{androstendipne}$ (4-androstene-3, 17-dione, 2,7%,$\text{5α-A-dione}$ (5α-androstane-3, 17-dione) 6,5%, $\text{DHT}$ (17β-hydroxy-5α-androstan-3-one) 47, 2%, $\text{3β-diol}$ (5α-androstane-3β, 17β-diol) 4, 4%, $\text{3α-diol}$ (5α-androstane-3α,17β-diol) 20, 8% and $\text{androsterone}$ (3α-hydroxy-5α-androstan-3-one) 3,4%. The relative amount of each metabolite is given in per cent of total radioactivity in the ether soluble fraction.     

Optimal temperature and photoperiod for the cultivation of Agardhiella subulata microplantlets in a bubble-column photobioreactor

The optimal temperature and illumination photoperiod requirements for the phototrophic growth of a novel microplantlet suspension culture derived from the macrophytic marine red alga Agardhiella subulata were determined. The optimal growth temperature was 24 degrees C. The effects of illumination light-dark (LD) photoperiod (hour of light:hours of darkness within a 24 h cycle) on biomass production was studied within a bubble-column photobioreactor. The 4.5 cm diameter photobioreactor was maintained at near-saturation conditions with respect to light flux (38 mciromol photons m(-2) s(-1)), nutrient medium delivery (20% nutrient replacement per day), and CO(2) delivery (0.35 mmol CO(2) L(-1) h(-1)) so that the cumulative effects of photodamage on the cell density versus time curve at photoperiods approaching continuous light could be observed. Biomass production was maximized at 16:8 LD, where biomass densities exceeding 3.6 g dry cell mass L(-1) were achieved after 60 days in culture. Biomass production was proportional to photoperiod at low fractional photoperiods (< or =10:14 LD), but high fractional photoperiods approaching continuous light (> or = 20:4 LD) shut down biomass production. Biomass production versus time profiles under resource-saturated cultivation conditions were adequately described by a cumulative photodamage growth model, which coupled reversible photodamage processes to the specific growth rate. Under light-saturated growth conditions, the rate constant for photodamage was kd = 1.17 +/- 0.28 day(-1) (+/-1.0 SE), and the rate constant for photodamage repair was kr = 5.12 +/- 0.95 day(-1) (+/-1.0 SE) at 24 degrees C.     

Response to experimental photoperiods by a migratory bunting, Emberiza melanocephala

Little is known about the effects of photoperiod on avian migrants that visit southeast Asia. In this paper, we report experiments performed on an emberizid finch, the Black-headed Bunting Emberiza melanocephala , to investigate its photoperiodic responses under artificial photoperiods, and continuous light and darkness.
Two series of experiments were performed with the photosensitive male birds. In the first series, different groups were exposed to seven different artificial photoperiods: 3L/21D, 6L/18D, 8L./16D, 11L/13D, 12L/12D, 15L/9D and 20L/4D, for 30 days. They were weighed and laparotomized at the beginning and end of the experiments. The birds responded to 12L/12D, 15L/9D and 20L/4D, but not to 3L/21D, 6L/18D, 8L/16D and 11L/13D. In the second series, photosensitive birds were placed under continuous light (LL) and dark (DD) conditions for 130 and 90 days. Periodic observations indicated that testicular growth and fattening followed by involution and fat-depletion had resulted in birds under LL, indicating the onset of photorefractoriness, while DD had no effect either on gonads or fattening in the buntings.
Our results demonstrate that light stimulation is a prerequisite to reproductive and metabolic activities (pre-migratory and migratory changes, fattening and weight gain) in the Black-headed Bunting, which has a photoperiodic threshold to these events at between 11 and 12 h daily photoperiods.     

Circadian control of singing in crickets: Two different pacemakers for early-evening and before-dawn activity

(1) Under LD 12:12 and constant temperature, calling song patterns of the Australian Field Cricket Teleogryllus commodus were frequently divided into two more or less distinct activity components. The first began 1–3 h before the $\text{L}\text{D}\text{-transition}$ and ended with the sudden lights-off, whereas the second was restricted mainly to the second half of the night. In subsequent continuous light (LL) the circadian activity pattern was usually a unimodal band. Its onset slope was always a continuation of the first onsets in the preceding LD-cycle. In those cases where shortly after the $\text{LD}\text{LL}$ transition the rhythm split into two components, both corresponded to those in LD. (2) In “atypical” LD-aatterns only the second component appeared during the late night. In such cases, the onset slope of the subsequent free-running rhythm did not start at the preceding LD-entrained onsets, but was advanced by several hours. (3) In free-running rhythms the mean value of the onset slopes ($\text{τ}{}_{\mathrm{o}}\text{= 25.1 ± 0.07}\text{h}$) did not differ significantly from that of the end slopes ($\text{τ}{}_{\mathrm{e}}\text{= 25.0 ± 0.07}\text{h}$). However, in individual activity patterns, simultaneous differences in onset and end slopes of up to 0.7 h were found. τ_o- and τ_e-values recorded directly after the $\text{LD}\text{LL}\text{-transition}$ did not correlate with the preceding phase angle difference between the entrained activity and the zeitgeber. (4) Under constant conditions after-effects such as spontaneous period changes and phase shifts in the slopes of activity onset and/or end occurred mainly between five and 20 days after the $\text{LD}\text{LL}\text{-transition}$. (5) Period changes and phase delays in the onset and end slopes were also found when crickets were exposed to low temperature pulses (2 ± 2°C, 2h duration). Following the cold treatment both period changes and phase shifts in the onset slope frequently differed from those in the end slope. (6) The results are consistent with a concept of two activity components controlled by weakly coupled circadian pacemakers. This is clearly evident in split rhythms but is also true for unimodal patterns. Normally the two components partly overlap and their existence is concealed in the undivided activity band. They are only revealed in unimodal patterns if individual oscillatory properties such as different period lengths or phase shifts appear in the onset or the end slope.     

Chemotactic migration of neutrophils under agarose.

A simple test for neutrophil chemotaxis is described. Wells were cut in soft agarose gel and filled with human peripheral blood leukocytes, chemotactin and control substances. Neutrophils consistently migrated under agarose towards the well with chemotactin, but not towards wells with control substances. Chemotaxis was quantitated as the mean distance travelled by 10 cells farthest from the well of origin, at specified time-intervals after filling the wells. Approximately $\text{1}\text{3}$ distance was covered in 2 hours, $\text{3}\text{4}$ in 4 hours and 90 per cent in 6 hours. The migrating cells examined after fixation and staining were found to be predominantly neutrophils with occasional eosinophils and monocytes.     

Influence of different photoperiods on development of gonad, cloacal gland and circulating thyroid hormones in male Japanese quail Coturnix coturnix japonica.

One day old chicks of Japanese quail were exposed to different photoperiods (LD, 8:16, 13.5:10.5, 16:8 and LL) and observations (testes weight, cloacal gland size, body weight and circulating thyroxine and triiodothyronine) were taken at the age of 3, 5, 7, 9 and 16 weeks. Results indicate that immediate reproductive development occurred in birds exposed to long photoperiods (greater than 12 hr). Growth under LD 8:16, was not apparent till 7th week and by 16 weeks, degree of gonadal development was similar in all the birds, irrespective of photoperiodic treatment. Whereas body weight of the intermediate and long day (LD 13.5:10.5, 16:8 and LL) treated birds increased upto 5th week and remained constant thereafter. But the chicks maintained under short day length (LD 8:16), showed spontaneous increase till the end of the study and birds were much heavier compared to all other groups. Plasma T4 concentration increased with increasing age till 9th week and remained unaltered thereafter. On the other hand T3 level did not change till 7th week followed by a decline. It is suggested that the initiation and degree of gonadal growth in quail depends on the availability of daily photoperiod, until the achievement of full breeding condition. Peak level of T4 observed in 9 week old birds may be involved in the development of photorefractoriness at that age.     

Responses of the cinnabar moth Hypocrita jacobaeae to various temperature/photoperiod régimes

Subjecting larvae of Hypocrita jacobaeae to temperatures of 21 and 28°C and photoperiods of $\text{0}\text{24}$, $\text{10}\text{14}$, $\text{12}\text{12}$, and $\text{18}\text{6}$ does not interfere with the phenomenon of diapause. The last larval instar is particularly affected by the higher temperature. Effects include numerous deaths, a high proportion of ill-formed pupae, and failure of adults to emerge properly from the pupal case. The significance of these findings is discussed.