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Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Juvenile Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) form seasonal aggregations near the salt wedge in their natal river systems. We used an array of Vemco positioning system acoustic receivers to track fine-scale movement within aggregation sites in two rivers in the Saint John River Basin. We used the t-LoCoH convex hull construction algorithm to map space use and aggregation behavior and nonmetric multidimensional scaling to test for differences among rivers, seasons, and photoperiods. Aggregation sites consisted of small core areas, where juvenile Atlantic sturgeon remained for long periods, that are adjacent to foraging grounds. This structure was largely consistent between rivers and seasons. Directional movement within aggregation sites differed between rivers. In areas of high flow velocity, directional movement was parallel to flow and largely restricted to littoral areas, whereas areas of low flow exhibited no distinct patterns in directional movement. This indicates flow may be an important driver of fine-scale distribution within aggregation sites. Studies of fine-scale space use can inform future investigations of rearing capacity, aid in the identification of critical habitat, and inform management decisions. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Light regime is an important zeitgeber for Antarctic krill (Euphausia superba Dana, 1850), which seems to entrain an endogenous timing system that synchronizes its life cycle to the extreme light conditions in the Southern Ocean. To understand the flexibility of Antarctic krill's seasonal cycle, we investigated its physiological and behavioural responses to different light regimes and if an endogenous timing system was involved in the regulation of these seasonal processes. We analysed growth, feeding, lipid content, and maturity in a 2-year laboratory experiment simulating the latitudinal light regimes at 52°S and 66°S and constant darkness under constant food level. Our results showed that light regime affected seasonal cycles of growth, feeding, lipid metabolism, and maturity in Antarctic krill. Seasonal patterns of growth, feeding, and maturity persisted under constant darkness, indicating the presence of an endogenous timing system. The maturity cycle showed differences in critical photoperiods according to the simulated latitudinal light regime. This suggests a flexible endogenous timing mechanism in Antarctic krill, which may determine its response to future environmental changes. [ABSTRACT FROM AUTHOR]

Gymnocarpos decandrus Forssk. (Caryophyllaceae) is a perennial plant widely used for its ability to protect the soil from erosion. The aim of this study was to evaluate the effects of salt stress on its seed germination, with the potential objective to sow seeds instead of planting adult individuals in salt-damaged areas, which would greatly reduce the economic costs of ecological restoration activities. Germination tests were conducted under two photoperiods and three thermoperiods, and with several concentrations of NaCl. The ability of seeds to recover their germinability after salt exposure was also evaluated. The highest rates of germination occurred at 20/30 °C in the light, but no seed germinated in the salt substrate. When exposed to NaCl, only a few seeds (no more than 20%) recovered their germinability and only at the lowest salinity, indicating that this species is highly glycophytic. The inability of its seeds to germinate in saline soils or to successfully recover from exposure to NaCl shows that G. decandrus may be used in rehabilitation programs of degraded lands in arid regions, but only when planting adult plants. Our results will help conservation biologists or people involved in ecological restoration activities to avoid the economic waste associated with unsuccessful sowing of G. decandrus seeds in saline soils. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sympatry of amphimictic and parthenogenetic lineages in species with mixed reproductive systems is rarely observed in nature. On Lampedusa Island (Pelagie Islands, Italy), amphimictic and parthenogenetic lineages of Heterocypris barbara (Gauthier and Brehm, 1928) co-occur in a temporary pond. Their sympatric persistence calls for an ecological differentiation. We investigated the role of seasonal variation of temperature and photoperiod conditions by two different approaches: microcosms set up by inundation of dry sediments from the temporary pond and life-table experiments. Microcosms recreate conditions similar to the field and in their sediments random samples of resting eggs of both amphimictic and parthenogenetic females are stored. Life-table experiments supplied individual-based estimates of survivorship, adult life span, fecundity, and sex ratio in the progeny. We carried out the experiments at 24 °C and a photoperiod of 12 h light (L) : 12 h dark (D) (simulating fall conditions) and at 16 °C and a photoperiod of 10 h L : 14 h D (simulating winter conditions). Males and amphimictic females were the most numerous forms at 24 °C and 12 h L : 12 h D; parthenogenetic females were dominant at 16 °C and 10 h L : 14 h D. Life-table experiments showed that amphimictic forms do not complete development at 16 °C and 10 h L : 14 h D. Our results suggest that sympatry of amphimictic and parthenogenetic females in the field depends on seasonal niche partitioning and the storage effect of resting eggs that allows survival through adverse-season conditions. [ABSTRACT FROM AUTHOR]

Many mammals use the change in day length to time physiological and behavioural activities on a seasonal basis. Particularly, mammals from temperate regions use photoperiod to regulate reproductive functions; however, information on the role of photoperiod in small mammals from the tropics and subtropics is scarce. We studied the response of the reproductive system of male eastern rock sengis ( Elephantulus myurus Thomas and Schwann, 1906) from southern Africa to photoperiods of differing length. Elephantulus myurus breeds seasonally during the spring and summer months of the southern hemisphere despite its subtropical distribution. It is one of only three sengi species known to breed seasonally. Fourteen male E. myurus were subjected to either long-day (LD; 16 h light (L) : 8 h dark (D)) or short-day (SD; 8 h L : 16 h D) photoperiods and the photoperiodic effects on the testes, testosterone concentration, and body mass were examined. Testicular volume and mass, seminiferous tubule diameter, and body mass were not significantly different between LD and SD conditions. However, plasma testosterone concentration was significantly lower in males on LD photoperiods compared with SD photoperiods. Male E. myurus may not use photoperiod as a cue to control seasonal reproductive changes. Other environmental factors such as temperature, rainfall, food abundance, or social factors are possibly influencing seasonal reproduction in this species. [ABSTRACT FROM AUTHOR]

Sea lampreys (Petromyzon marinus L., 1758) are nocturnal, so experiments evaluating their behaviour to chemosensory cues have typically been conducted at night. However, given the brief timeframe each year that adult P. marinus are available for experimentation, we investigated whether P. marinus exposed to a 12 h shifted diurnal cycle (reversed photoperiod) could be tested in a darkened arena during the day and show the same response to chemosensory cues as natural photoperiod P. marinus that were tested during the night. Ten replicates of 10 P. marinus, from each photoperiod, were exposed to deionized water (negative control), 2-phenylethylamine hydrochloride (PEA HCl, putative predator cue), or P. marinus whole-body extract (conspecific alarm cue). All P. marinus demonstrated a significant avoidance response to both cues. No significant differences were found in avoidance to PEA HCl between photoperiods. Avoidance of P. marinus whole-body extract was significantly stronger in natural compared with reversed photoperiod P. marinus. The use of reversed photoperiod subjects is suitable for examining the presence or absence of avoidance in response to novel chemosensory alarm cues, or the change in the magnitude of antipredator response. Studies investigating the natural magnitude of antipredator response should use natural photoperiod experimental subjects. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the ontogeny of digestive enzymes and effects of photoperiod on pancreatic enzyme activity in rainbow trout (Oncorhynchus mykiss (Walbaum, 1792)) alevin and fry. After hatching, 3600 individuals of first-feeding alevin with a mean (±SD) mass of 119 ± 0.01 mg were reared in plastic tanks at four photoperiod levels (llight (L) : dark (D) cycle) for 6 weeks. Each replicate contained 300 alevin. Photoperiod treatments consisted of 14 h L : 10 hD, 10 h L : 14 h D, 4 h L : 20 h D, and 24 h L : 0 h D. During the rearing period, environmental variables including water temperature, oxygen, and pH were checked. Random sampling of alevin and fry was done at 0, 1, 3, 5, 8, 10, 15, 20, 25, 30, 39, and 44 days after the beginning of the first feeding (equal to 18, 19, 23, 25, 28, 30, 35, 40, 45, 50, 58, 63 days post hatching (dph)). The digestive enzyme activities in alevin and fry had a similar variation trend with age at all photoperiod levels. The specific activities of trypsin, chymotrypsin, and α-amylase at 24 h L : 0 h D were significantly higher than other treatments, but there was no significant difference in specific activity of lipase among treatments. The results demonstrated that growth, feeding efficiency, and digestive enzyme activity improved with longer exposure to photoperiod in rearing conditions. [ABSTRACT FROM AUTHOR]

Photoperiodism involves the use of both absolute measures of day length and the direction in which day length is changing as a cue for regulating seasonal changes in physiology and behaviour so that birth and lactation coincide with optimal resource availability, increasing offspring survival. Induced ovulation and opportunistic breeding is often found in species that are predominantly solitary and territorial. In this study, the photoperiodic reproductive responses of male greater red musk shrews ( Crocidura flavescens (I. Geoffroy Saint-Hilaire, 1827)) were investigated in the laboratory. The presence of spermatozoa regardless of the light cycle, suggest that although the shrews are photoresponsive, they may be capable of breeding throughout the year. Significantly greater testicular volume and seminiferous tubule diameter following exposure to a short day-light cycle suggests that these animals may have breeding peaks that correspond to short days. The presence of epidermal spines on the penis indicates that the shrew is likely also an induced ovulator. Flexible breeding patterns combined with induced ovulation affords this solitary species the greatest chance of reproductive success. [ABSTRACT FROM AUTHOR]

Artificial lighting, especially but not exclusively through street lights, has transformed the nighttime environment in much of the world. Impacts have been identified across multiple levels of biological organization and process. The influences, however, on population dynamics, particularly through the combined effects on the key demographic rates (immigration, births, deaths, emigration) that determine where individual species occur and in what numbers, have not previously been well characterized. The majority of attention explicitly on demographic parameters to date has been placed on the attraction of organisms to lights, and thus effectively local immigration, the large numbers of individuals that can be involved, and then to some extent the mortality that can often result. Some of the most important influences of nighttime lighting, however, are likely more subtle and less immediately apparent to the human observer. Particularly significant are effects of nighttime lighting on demography that act through ( i) circadian clocks and photoperiodism and thence on birth rates; ( ii) time partitioning and thence on death rates; and ( iii) immigration/emigration through constraining the movements of individuals amongst habitat networks, especially as a consequence of continuously lit linear features such as roads and footpaths. Good model organisms are required to enable the relative consequences of such effects to be effectively determined, and a wider consideration of the effects of artificial light at night is needed in demographic studies across a range of species. [ABSTRACT FROM AUTHOR]

The environmental cues that regulate smoltification and trigger downstream movement by salmon should vary across space in response to differences in the predictability of favorable conditions for migration and ocean entry. To examine this, we modeled the short-term outmigration probability of four coho salmon ( Oncorhynchus kisutch) populations in three distinct geographic regions in relation to photoperiod, temperature, streamflow, lunar phase, and interactions among these variables. For smolts in Deer and Flynn creeks, Oregon (1960-1972), migration probability was influenced by numerous factors, including photoperiod, temperature (absolute and change), flow (absolute and change), and lunar phase, with certain factors interacting. Smolts from Carnation Creek, British Columbia (1972-1986) responded to a similarly diverse suite of factors (excluding lunar phase), though in somewhat different ways. In contrast, migration timing of smolts in Sashin Creek, Alaska (1959-1969) was best explained by a model that included only photoperiod, temperature, and the interaction between these terms. These population differences suggest fundamental differences across regions in the selection processes operating in both marine and freshwater environments. [ABSTRACT FROM AUTHOR]

The present study documents the changes in carbon and nitrogen metabolites occurring in apical buds and previous year stems of white spruce seedlings ( Picea glauca [Moench] Voss) with contrasting growth phenotypes (tall vs. small) after transfer to short day (SD; 8 h) photoperiod to induce bud formation. Concentrations of total nonstructural carbohydrates markedly increased in the developing buds within the days after transfer to SD, mainly as a result of increased concentrations of monosaccharides such as glucose, fructose, and pinitol. At the same time, starch levels declined, with the resulting carbohydrates presumably used to meet early carbon requirements of the SD-induced apical bud. Concentrations of glutamine, glutamic acid and proline also decreased immediately after transfer to SD in both organs. Later stages of SD-induced bud formation were characterized by an increase in starch, sucrose, and glutamine concentrations in previous year stems, concomitant with an increase in the steady-state levels of UDP-glucose pyrophosphorylase and glutamine synthetase protein. In contrast, arginine levels increased after 2 weeks of SD exposure, indicating a transition in arginine metabolism at the time of initiation of shoot stem primordia and bud elongation. Higher accumulation of total nonstructural carbohydrates and total amino acids in previous year stems of small trees could indicate lower sink strength of apical bud during its development, which could in turn impact subsequent tree growth. [ABSTRACT FROM AUTHOR]

Allergy prevalence and severity varies seasonally in humans, presumably due to intra-annual changes in allergen exposure. However, it is possible that seasonality of allergic responses is also influenced by seasonal changes in the immune system. Here, we asked whether extended exposure to different day lengths would alter allergic responses to pentadecylcatechol (PDC), an allergenic component of poison ivy ( Toxicodendron radicans (L.) Kuntze), in Siberian hamsters ( Phodopus sungorus (Pallas, 1773)), a species exhibiting extensive seasonal variation in immune functions. We found that contact dermatitis responses were larger in short day-length (SD) housed animals than in long day-length (LD) housed animals even though sensitization and challenge dosages of allergen were identical. Furthermore, SD animals were smaller and had regressed reproductive tissues compared with LD animals, results typically observed in this species in response to photoperiod. These data suggest that endogenous changes in immune functions, perhaps via melatonin, may underlie some seasonal variation in allergic responses. [ABSTRACT FROM AUTHOR]

A naturally variable life-history trait with underlying physiological variation is the photoperiodic response of many temperate-zone rodents, including white-footed mice ( Peromyscus leucopus (Rafinesque, 1818)). Male P. leucopus were obtained from a short photoperiod responsive (R) line, artificially selected for reproductive suppression in short-day conditions (SD) and a nonresponsive (NR) line selected for reproductive maturity in SD. We tested for variation in metabolic rate between lines in SD and long-day conditions (LD). NR mice consumed 34% more food than R mice, without concomitant increase in body mass in SD. Basal metabolic rate (BMR) was found to be significantly greater in NR than R mice, and NR mice were found to engage in significantly more spontaneous (daily) locomotor activity. Energy-use estimates based on 24 h respirometry matched closely the level of intake reported for individual mice. The increased BMR and average daily metabolic rate in NR mice was correlated with testis size, but not with major central organs or digestibility. No significant difference in BMR or activity was found in mice from the same lines held in LD. Elevated intake in SD mice appears to be associated with differences in fertility and not other aspects of physiology in the respective lines. [ABSTRACT FROM AUTHOR]

Under sink-limited conditions, source activity is modulated to remain in balance with the use of carbohydrates by the sink, but this feedback control has been studied in only a few systems so far. Sink and source activities were investigated throughout the season. Plants were subjected to two photoperiod regimes combined with two irradiance levels to produce three different daily amounts of photons. Net photosynthetic rate and the photochemical efficiency of photosynthesis were initially higher under a long photoperiod, but decreased early in the growth season, whereas they remained fairly constant until a few days before leaf senescence under a short photoperiod. The rates of starch and biomass accumulation in the bulb were also faster under a long photoperiod at the beginning of the season but reached similar levels under both short and long photoperiods later on. Response to photoperiod cannot be explained by changes in daily amounts of photons, as none of the variables reported were affected by instantaneous or daily irradiance. It appears that the total amount of carbohydrate synthesized under a long photoperiod was in excess compared to the ability of the sink to store or use them, inducing a feedback inhibition of net photosynthetic rate to restore the source-sink balance. [ABSTRACT FROM AUTHOR]

Hypovirulence in is associated with infection by (OMV3a). OMV3a is also present in asymptomatic isolates, with growth and virulence comparable to that of virus-free isolates. Hypovirulent isolates have impaired mitochondrial function resulting in increased activity of the alternative oxidase pathway, which is implicated in the reduction of reactive oxygen species in other fungi. In this study, hypovirulent, asymptomatic, and virus-free isolates were grown on potato dextrose agar amended with ascorbic acid or glutathione and were incubated under various photoperiods to determine the importance of reactive oxygen species, light, and OMV3a infection for differentiation of stromata and apothecia by S. homoeocarpa. Hypovirulent isolates did not form stromata or apothecia. Glutathione and darkness reduced stromata size and apothecia production by virulent and asymptomatic isolates. Apothecia formed under several different photoperiods, and ascorbic acid increased apothecia production. Ascospores were not detected in these apothecia. The results suggest that hypovirulence, light, and the superoxide radical are important factors in the formation of stromata and apothecia by S. homoeocarpa isolates. This is the first report of sterile apothecia production by North American isolates of S. homoeocarpa and provides a starting point for attempts to produce fertile apothecia. [ABSTRACT FROM AUTHOR]

The herbaceous perennial weed Euphorbia esula L. (Euphorbiaceae) reproduces by vegetative and sexual means, characteristics that are key to its persistence and survival. In this study, we examined environmental effects on regrowth and flowering under controlled conditions to further validate field observations and set the stage for the future identification of molecular mechanisms involved in the regulation of these processes. Shoot cuttings were exposed to different combinations of decreasing temperatures, decreasing photoperiods, and vernalization, in growth chambers. Subsequently, shoots were removed and regrowth and flowering from new shoots were monitored in a warm temperature greenhouse under long-day conditions. Vernalization alone has no effect on regrowth and flowering. Plants required decreasing temperature followed by vernalization for rapid regrowth and flowering. Decreasing photoperiod at a constant temperature with or without vernalization had no significant effect on regrowth and flowering. In conjunction with previous field research, the results suggest that a gradually decreasing temperature is required as one of the components for flowering competence and vernalization is determinate for reproductive development under long-day conditions. [ABSTRACT FROM AUTHOR]

Short days induce winter-like adaptations in small mammals such as Siberian hamsters (Phodopus sungorus (Pallas, 1773)). Specifically, hamsters adjust food consumption, metabolic processes, and immune function to optimize energetic needs and promote winter survival. One potentially inexpensive behavioral adaptation to increase survival is avoidance of infection. We tested the hypothesis that photoperiod affects avoidance of potentially infected food. In experiment 1, hamsters were weaned into either short or long days with ad libitum food. Three weeks later, hamsters were presented with either skim milk treated with butyric acid (2%), a bacterial product that serves as a potent cue of spoilage, or unadulterated skim milk; consumption was measured. After milk presentation, blood samples were obtained to assess cortisol. In experiment 2, skim-milk consumption was again assessed after 3 weeks in either short or long days. In experiment 3, we tested the hypothesis that food avoidance was due to photoperiod-induced differential neophobia. Short-day hamsters increased milk consumption, which was blocked by butyric acid. Short days increased cortisol concentrations; neither food restriction nor butyric acid affected cortisol concentrations. Photoperiod did not alter neophobic responses. These experiments suggest that short-day hamsters avoid food treated with butyric acid possibly as an adaptive trait to avoid costly winter infections. [ABSTRACT FROM AUTHOR]

High-latitude arvicoline rodents usually reproduce in warmer months, but winter breeding has been documented in several species, including the northern red-backed vole (Myodes rutilus (Pallas, 1779) Wilson and Reader, 2005; formerly Clethrionomys rutilus (Pallas, 1779)). We tested whether the reproductive condition of the species is linked to changes in environmental parameters or its body condition, and we tested the frequencies at which different reproductive phenotypes are exhibited under field and laboratory conditions. Free-living voles in south-central Alaska reached peak reproductive organ masses in spring (females) and early summer (males). Between-subject comparisons showed an effect of body mass, photoperiod, percent fat, temperature, and snow depth on reproductive organ masses, depending on the sex and breeding period (p < 0.05). One instance of late-summer photoperiod nonresponsiveness was observed, but we detected no winter breeding. Captive male voles given food ad libitum and housed at room temperature exhibited strong phenotypic variation in testis mass in response to short photoperiods. The percentage of nonresponders was 28.2% and was within the known range of nonresponsiveness for lower latitude species (20%-40%). Thus, photoperiod nonresponsive morphs are conserved in at least one arctic and subarctic species at frequencies comparable to lower latitude voles despite no observance of winter breeding in the field. Voles exhibit reproductive elasticity and may breed in winter if environmental conditions enable them. Les rongeurs arvicolinés des hautes latitudes se reproduisent généralement durant les mois plus chauds, mais on a signalé des cas de reproduction hivernale chez plusieurs espèces, en particulier chez le campagnol boréal (Myodes rutilus (Pallas, 1779) Wilson and Reeder, 2005; antérieurement Clethrionomys rutilus (Pallas, 1779)). Vous avons testé si la condition reproductive chez cette espèce est reliée aux changements des variables environnementales ou à sa condition corporelle et avons vérifié les fréquences auxquelles les divers phénotypes reproductifs se présentent dans des conditions de terrain et de laboratoire. Chez les campagnols libres en nature dans le centre-sud de l’Alaska, la masse des organes reproducteurs atteint son maximum au printemps (femelles) et au début de l’été (mâles). Des comparaisons entre individus révèlent un effet de la masse corporelle, de la photopériode, du pourcentage de graisses, de la température et de la profondeur de la neige sur la masse des organes reproducteurs en fonction du sexe et de la période de reproduction (p < 0,05). Nous avons observé un cas d’absence de réaction à la photopériode en fin d’été, mais détecté aucune reproduction hivernale. Des campagnols mâles en captivité, nourris ad libitum et maintenus à la température de la pièce, montrent une importante variation phénotypique dans leur masse testiculaire en réaction aux photopériodes courtes. Le pourcentage d’individus sans réaction était de 28,2 %, ce qui est dans la gamme connue d’absence de réaction chez les espèces de latitudes plus basses (20 % - 40 %). Ainsi, les formes qui ne réagissent pas à la photopériode sont conservées chez au moins une espèce arctique et subarctique à des fréquences comparables à celles trouvées chez les campagnols de latitudes plus basses, même si aucune reproduction hivernale n’a été observée en nature. Les campagnols possèdent une plasticité reproductrice et peuvent se reproduire en hiver si les conditions du milieu le permettent. [ABSTRACT FROM AUTHOR]

Small mammals use day length to adjust morphology and physiology to anticipate seasonal changes in environmental conditions. The canonical photoperiod-mediated annual adaptation is seasonal breeding. However, increasing evidence suggests that day-length information can induce plasticity in the nervous system, and thus provoke behavioral plasticity that can aid in winter survival. We hypothesized that low temperatures and reduced food availability in the winter would necessitate the evolution of increased pain tolerance mediated by short day lengths. Siberian hamsters (Phodopus sungorus (Pallas, 1773)) housed in short days regressed their reproductive tracts and molted to winter pelage. Short-day hamsters also displayed elevated latencies of nociceptive responses in the hot-plate test, suggesting reduced pain responsivity. Prior to assessing potential neuronal or neuroendocrine mediators of altered pain responses, however, we investigated the possibility that changes in fur characteristics mediated photoperiod differences in pain responsivity. Removal of fur with a depilatory cream eliminated photoperiod differences in pain responsivity. Taken together, these data indicate that day length regulates thermal pain responses via changes in fur properties; also, changes in pelage properties have both thermoregulatory and thermal insulatory properties. [ABSTRACT FROM AUTHOR]

Interactions between temperature and photoperiod on growth of Atlantic cod (Gadus morhua) juveniles (initial weight 9.1 g) were studied by rearing juvenile cod 3 months under simulated natural photoperiod (LDN) and continuous light (LD24:0) at 7, 10, and 13 °C. Juvenile Atlantic cod exposed to LD24:0 had higher growth rate and better feed conversion efficiency compared with cod reared under LDN. Optimal temperature for growth of juvenile Atlantic cod in the size range 5–50 g was influenced by photoperiod and was estimated to be 12.3 °C under LD24:0 and 15.7 °C under LDN. After termination of the laboratory study, the fish were reared in sea pens at ambient conditions for 17 months. The growth-enhancing effect of LD24:0 could be traced far beyond the duration of the laboratory trial, as the final mean weights in June 2005 of the fish reared at LD24:0 and 13 and 10 °C in the laboratory trial were 8% and 13% higher than those of the respective LDN groups. Our study indicates a physiological mechanism that might be linked to cod migrations, as maximal growth and feeding efficiency will be attained in areas during a season with extended day length or continuous light. [ABSTRACT FROM AUTHOR]

An experiment was performed to determine the relative effects of photoperiod at emergence and growth rate on smolting pattern and early male maturation rate in Sacramento River (California, USA) winter-run chinook salmon (Oncorhynchus tshawytscha) (listed as endangered under the US Endangered Species Act). Fry were ponded on the same day but at three different points in the seasonal photoperiod cycle (using artificial lighting) spanning the natural range of emergence timing in this population. Significant increases in gill Na+,K+-ATPase activity and seawater survival were found during March and April in all treatments, similar to yearling smolting patterns found in many salmonids. Fish that emerged early and grew at a relatively high rate also demonstrated signs of smolting in August–November. Male maturation was growth dependent, with HiFeed groups maturing at a rate double that found in LoFeed groups. Male maturation was also photoperiod dependent with a linear relation found between emergence date and rate of male maturation. These results demonstrate that individual life history pattern was variable and dependent on emergence timing and growth rate. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Research to date has not clearly defined the role of photoperiod in regulating somatic growth in Atlantic cod (Gadus morhua). The present study followed individual growth performance, plasma insulin-like growth factor-I, and relative liver size in response to a range of experimental photoperiod treatments where populations were transferred from an ambient photoperiod regime to continuous illumination at strategic times during the first 2 years of life. While this work demonstrated that application of continuous illumination could directly stimulate somatic growth, this growth stimulation is transitory with no accumulative effect of prolonged exposure to continuous illumination. Importantly, it was apparent that the photic inhibition of maturation realized a far more significant growth stimulation, and in populations where this occurred, sexually dimorphic growth patterns became apparent. Plasma insulin-like growth factor-I displays a seasonal rhythm correlated with ambient temperature under natural photic conditions and in certain circumstances could be used as an accurate predictor of growth rate. Overall, this work further refines the guidelines on photoperiod management during commercial ongrowing of the species to help realize the maximum economic potential of cod aquaculture. [ABSTRACT FROM AUTHOR]

According to previous studies, short-day (SD) treatment may increase frost hardiness in Picea abies (L.) Karst. seedlings during shoot elongation the next year. The purpose of this study was to examine how timing of the SD treatment affects spring frost hardiness. The following four treatments were applied in the first growth period: natural photoperiod (Nat), or SD treatment (8 h light : 16 h dark) either 14–28 July (SD1), 28 July – 11 August (SD2), or 11–20 August (SD3). After 125 days in cold storage (October–January), the seedlings were transferred to forcing conditions (20–25 °C, 24 h light) followed by freezing tests at –3, –5, –7, and –9 °C when most seedlings had reached bud break stage 7 (Krutzsch index). Seedling height measurements and analyses of carbohydrate status, nitrogen concentration, and dry mass of needles after cold storage were done to examine the treatments' impact on seedling quality. SD treatment reduced visual freezing injury to current- and first-year shoots. Mortality occurred at –7 and –9 °C and was significantly higher in the Nat and SD1 treatments (43% in both) than in the SD2 (23%) and SD3 (15%) treatments. Seedlings from the late SD treatments also showed better height growth and developed more shoots from dormant buds after freezing to –3 and –5 °C. Collectively, these findings demonstrate the importance of proper timing of the SD treatment in relation to the seedlings' natural growth rhythm. [ABSTRACT FROM AUTHOR]

Plant ecotypes of Stellaria longipes Goldie from competitive, shade-adapted prairie habitat and less competitive, nonshaded alpine habitat were subjected to shortened or extended photoperiod conditions. Increasing daylength was positively correlated to increased stem elongation in both ecotypes. Leaf length and area for shade (prairie) plants was significantly altered with increased photoperiods, whereas sun (alpine) plants exhibited minimal leaf expansion in response to increased photoperiod. Increased ethylene evolution in the alpine genotype during rapid stem elongation and extended photoperiods suggests that ethylene plays a growth regulatory role in this sun-adapted genotype. The prairie genotype evolved less ethylene during these same periods, indicating either a diminished requirement for elevated ethylene to effect elongation and leaf expansion responses or possibly increased ethylene sensitivity because of interactions with other hormones, such as gibberellin or auxin. The sun genotype consistently produced more ethylene than the shade genotype under all photoperiod treatments. We conclude that photoperiod alters stem elongation and leaf expansion responses; similar trends were observed for extended photoperiods as were observed for shaded conditions, specifically low light intensity (photosynthetically active radiation) conditions. Further, ethylene levels altered during these responses, especially in sun-adapted alpine plants, which suggests that ethylene is involved in these growth responses. [ABSTRACT FROM AUTHOR]

Age-1+ to age-3+ Atlantic cod (Gadus morhua) were held at either constant (~9 °C) or ambient ocean temperatures (Newfoundland) from December 2000 to June 2002 under natural photoperiod and ad libitum feeding. Body mass and length, liver total lipids, triacylglycerols and free fatty acids, glycogen and protein from liver and muscle, plasma glucose, and lactate were assessed over this period. Both groups increased body mass, length, and liver mass, with a significantly greater increase for the constant group at all sampling dates. Both groups demonstrated a growth phase from August to October 2001, while the ambient group showed a compensatory growth phase from May to July 2001. Gonad mass significantly increased in males and females from both groups in June 2002. Most tissue metabolites demonstrated seasonal patterns consistent with photoperiod. The effect of temperature was primarily quantitative, implicating temperature changes food conversion efficiencies, as both groups of cod had the same access to food. Under the conditions of this study, Atlantic cod growth is controlled primarily by photoperiod, with temperature affecting the amounts of tissue metabolites. Des morues Atlantiques (Gadusmorhua) âgées de +1 à +3 années ont été maintenues à la température ambiante de l'océan à Terre-Neuve ou à une température constante (~9 °C) de décembre 2000 jusqu'en juin 2002, sous une photopériode naturelle, et nourries ad libitum. La masse et la longueur du corps, les lipides totaux, les triacylglycérols et les acides gras libres du foie, le glycogène et les protéines musculaires et hépatiques, le glucose et le lactate plasmatiques ont été mesurés à huit reprises pendant la période étudiée. Les deux groupes de poissons ont subi une augmentation de la masse corporelle, de la longueur totale et de la masse du foie durant la période étudiée, avec une augmentation plus grande à toutes les dates d'échantillonnage chez le groupe maintenu à température constante. Il y a une phase de croissance d'août à octobre 2001 chez les deux groupes et une seconde phase de croissance compensatrice de mai 2001 à juillet 2001 chez le groupe maintenu à température ambiante. La masse des gonades des mâles et des femelles a augmenté significativement en juin 2002 chez les deux groupes. La plupart des métabolites tissulaires ont suivi des patrons saisonniers reliés à la photopériode. L'effet de la température est surtout quantitatif et implique des changements des efficacités de conversion de la nourriture, puisque les deux groupes de morues ont un accès identique à la nourriture. Dans les conditions de notre étude, la croissance de la morue atlantique est contrôlée surtout par la photopériode, alors que la température affecte les quantités de métabolites tissulaires. [ABSTRACT FROM AUTHOR]

Atlantic cod (Gadus morhua) were held at either constant (~9 °C) or ambient ocean temperatures from December 2000 to June 2002 under natural photoperiod. The activities of gluconeogenic, glycolytic, lipid, and amino-acid-related enzymes were measured in liver and white muscle at eight time points over the experimental period. Principal component analysis reduced the 13 liver enzymes to two factors and the nine muscle enzymes to three factors. Factor scores were used to investigate the effects of season, temperature, and photoperiod on cod physiology. Liver factor I (FI) and muscle factor III (FIII) were significantly correlated with mass and length of the fish. Only liver FI was significantly correlated with tissue metabolites parameters. Significant differences between thermal groups were only observed for muscle FIII in June 2002. This study demonstrates that temperature is not a major factor determining the activity of the selected enzymes in ages-1+ to -3+ cod. Photoperiod and internal physiological cycles are more important in determining liver and muscle enzyme activities. Most liver enzymes measured are better indicators of fish growth than muscle enzyme, and liver protein is the parameter that best correlates with body mass, length, and liver mass. Des morues Atlantiques (Gadus morhua) ont été maintenues à une température constante (~9 °C) ou à la température océanique ambiante, de décembre 2000 jusqu'en juin 2002; les deux groupes ont été soumis à une même photopériode ambiante. Les activités des enzymes de la glyconéogenèse, de la glycolyse, du métabolisme des lipides et des protéines ont été mesurées dans le muscle blanc et le foie à huit reprises durant la période étudiée. Une analyse des composantes principales permis de réduire les 13 enzymes hépatiques à deux facteurs et les neuf enzymes musculaires à trois facteurs. Les positions de ces facteurs ont ensuite été utilisés pour rechercher les effets des saisons, des températures et de la photopériode sur métabolisme intermédiaire de la morue atlantique. Le facteur I (F1) du foie et le facteur III (F3) du muscle sont significativement corrélés à la masse et la longueur des poissons. F1 du foie est le seul facteur significativement corrélé aux métabolites tissulaires. Des différences significatives entre les groupes thermiques ont étés trouvées seulement chez F3 du muscle en juin 2002. Notre étude démontre que la température n'est pas un facteur déterminant majeur de l'activité des enzymes sélectionnées chez les morues âgées de +1 à +3 années. La photopériode et les cycles physiologiques internes sont plus importants pour déterminer l'activité enzymatique du foie et du muscle. La plupart des enzymes hépatiques mesurées sont de meilleurs indicateurs de la croissance des poissons que les enzymes musculaires. De plus, la quantité de protéines hépatiques est la variable le plus fortement corrélée à la masse et la longueur des poissons ainsi qu'à la masse du foie. [ABSTRACT FROM AUTHOR]

Animals use day length (photoperiod) to time seasonal adaptations to annual changes in their environment. Reproductive adjustments in deer mice (Peromyscus maniculatus (Wagner, 1845)) from high latitudes are more extensive in response to short days than in deer mice from low latitudes. These adjustments may permit individuals to survive the severe seasonal changes (e.g., temperature and food abundance) in high-latitude environments. Immune function is also affected by photoperiod. Short days were predicted to result in elevated immune and reproductive responses in meadow voles (Microtus pennsylvanicus (Ord, 1815)) from the Northwest Territories (NWT), Canada (~62°N), compared with voles from Ohio (OH), USA (~39°N). Male voles from both latitudes were maintained in long or short days for 10 weeks prior to a delayed-type hypersensitivity (DTH) immune challenge. Both populations displayed similar testicular regression and reduction of testosterone concentrations in short days. DTH immune responses, however, diverged between the two populations. DTH immune responses were enhanced in long-day NWT voles and short-day OH voles, but decreased in short-day NWT voles and long-day OH voles. Total and free corticosterone concentrations did not explain the latitudinal differences in immune responses. These results suggest that photoperiod affects reproductive and immune systems differently and that immune responses may reflect other environmental factors. [ABSTRACT FROM AUTHOR]

We tested whether male and female black-capped chickadees, Poecile atricapillus (L., 1766), were absolutely photorefractory according to Hamner's (1968) criteria of (i) spontaneous regression of gonads during prolonged long-day exposure and (ii) no subsequent recrudescence of gonads in response to constant light. We initially exposed black-capped chickadees to constant long-day photoperiods. Gonads regressed spontaneously, demonstrating that the birds met Hamner's first criterion for absolute photorefractoriness. Once their gonads fully regressed and the birds were in advanced prebasic moult, we exposed them to one of three photoperiods for an additional 2 weeks: constant light (24 h L), short days (8 h L), and controls (15 h L). Constant light challenge had no effect on gonadal condition or rate of moult, confirming that the birds met Hamner's second criterion for absolute refractoriness. We also compared volumes of song-control nuclei in the three groups and found that males overall had larger HVC, robust nucleus of arcopallium, and area X than females, but that longer days (24 h L) did not increase volumes and that shorter days (8 h L) did not decrease volumes compared with controls (15 h L). These data support the inference that black-capped chickadees do indeed become absolutely photorefractory, and that photorefractoriness precludes photo-induced plasticity of the song-control system. [ABSTRACT FROM AUTHOR]

Soybean near isogenic lines (NILs), contrasting for maturity and photoperiod sensitivity loci, were genotyped with approximately 430 mapped simple sequence repeats (SSRs), also known as microsatellite markers. By analysis of allele distributions across the NILs, it was possible to confirm the map location of the Dt1 indeterminate growth locus, to refine the SSR mapping of the T tawny pubescence locus, to map E1 and E3 maturity loci with molecular markers, and to map the E4 and E7 maturity loci for the first time. Molecular markers flanking these loci are now available for marker-assisted breeding for these traits. Analysis of map locations identified a putative homologous relationship among four chromosomal regions; one in the middle of linkage group (LG) C2 carrying E1 and E7, one on LG I carrying E4, one at the top of LG C2, at which there is a reproductive period quantitative trait locus (QTL), and the fourth on LG B1. Other evidence suggests that homology also exists between the E1 + E7 region on LG C2 and a region on LG L linked to a pod maturity QTL. Homology relationships predict possible locations in the soybean genome of additional maturity loci, as well as which maturity loci may share a common evolutionary origin and similar mechanism(s) of action. [ABSTRACT FROM AUTHOR]

To present quantitative knowledge of photoperiod and temperature on frost hardiness for mathematical modelling, we carried out a growth chamber experiment for second-year Scots pine (Pinus sylvestris L.) seedlings. There were three treatments involved in the trial: a short photoperiod (7 h light : 17 h dark cycle) with a high temperature (15 °C) (SDHT), a short photoperiod (7 h light : 17 h dark cycle) with a low temperature (2 °C), and a long photo period (16 h light : 8 h dark cycle) with a low temperature (2 °C). The following variables were measured: (i) the frost hardiness of stems, needles, buds, and roots by controlled freezing tests, (ii) the electrical impedance spectroscopy (EIS) parameters of the stems, (iii) the chlorophyll fluorescence (F[sub v] /F[sub m] ) of the needles, (iv) the dry mass/fresh mass ratio, and (v) the total soluble sugar and starch concentration of the stems, needles, and roots in the non-frost-exposed organs. There was a clear difference in hardiness among the organs by the end of the experiment. Stems by some EIS parameters, needles by F[sub v] /F[sub m] , and stems, needles, and roots by sugar concentration differed among treatments. A stationary level of frost hardiness was reached or asymptotically approached in all organs and treatments except in the SDHT treatment of buds. Very little support was found for the concept of additive effects by photoperiod and temperature. The results show that the additive model needs revision, since the hardening response is dependent on organ, and there is an interaction in the responses to photoperiod and temperature.Une expérience en chambres de croissance a été réalisée afin de modéliser l'effet quantitatif de la photopériode et de la température sur la tolérance au gel de semis de pin sylvestre (Pinus sylvestris L.) âgés de 2 ans. Les semis ont été exposés à trois traitements: une photopériode courte (cycle de 7 h lumière : 17 h obscurité) à une température élevée (15 °C) (PCTE), une photopériode courte (cycle de 7 h lumière : 17 h obscurité) à une température basse (2 °C) et une photopériode longue (cycle de 16 h lumière : 8 h obscurité) à une température basse (2 °C). On a mesuré (i) la tolérance au gel des tiges, des aiguilles, des bourgeons et des racines à l'aide de tests de congélation, (ii) les paramètres spectroscopiques d'impédance électrique des tiges (IE), (iii) la fluorescence de la chlorophylle (F[sub v] /F[sub m] ) des aiguilles, (iv) le rapport masse sèche/masse fraîche et (v) la concentration en sucres solubles totaux et en amidon des tiges, des aiguilles et des racines non exposées au gel. La tolérance au gel différait nettement selon les organes à la fin de l'expérience. On a observé des différences entre les traitements pour quelques paramètres d'IE des tiges, pour le rapport F[sub v] /F[sub m] des aiguilles ainsi que pour la concentration en sucres des tiges, des aiguilles et des racines. Un niveau de tolérance au gel stationnaire a été atteint ou approché de façon asymptotique pour tous les organes et tous les traitements à l'exception des bourgeons sous le traitement de PCTE. Il y a peu d'évidence pour supporter le concept d' addi tivité de l'effet de la photopériode et de la température sur la tolérance au gel. Les résultats montrent que le modèle additif exige une révision puisque l'endurcissement varie selon l'organe et qu'il existe une interaction dans les réponses à la photopériode et à la température.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The paper examines neural and gonadal responses to photoperiod in a late-summer-breeding finch called the American goldfinch or carduelis tristis. The seasonal changes in gonads of free-living goldfinches have been measured. The hypothalamic gonadotropin-releasing hormone system and song-control system of breeding and postbreeding birds were compared. The results confirm that the gonads of wild goldfinches regress in late summer and show that the gonads of goldfinches held on constant long days regress spontaneously.

Three species within the Entomophthora muscae (Cohn) Fresenius complex (Entomophthora schizophorae Keller & Wilding, E. muscae s.str., and E. muscae "group B") were investigated for resting spore formation in vivo in the house fly (Musca domestica L.). Resting spores of E. muscae group B were experimentally induced from August to the beginning of February, while no resting spores were ever observed in E. schizophorae infected M. domestica or in flies infected by E. muscae s.str. originating from M. domestica. When newly dead fly cadavers containing E. muscae group B resting spores were kept moist, cystidia emerged from the abdomen; this is the first report of cystidia in the genus Entomophthora. Resting spore production was significantly affected by both temperature and E. muscae group B strain. More infected flies formed resting spores when kept 1 week at 10°C compared with constant exposure at 22°C, but the tendency of the different E. muscae group B strains to form resting spores persisted with shifting temperatures. After 4 months of incubation under natural winter conditions in Denmark, E. muscae group B resting spores germinated on water agar at 20°C with a 16 h light : 8 h dark photoperiod within 1 week, but no germ conidia were observed.Key words: Entomophthorales, Entomophthora muscae complex, Diptera, Musca domestica, resting spore formation, resting spore germination.Les auteurs ont examiné, chez la mouche de maison (Musca domestica L.), la formation in vivo des spores de repos de trois espèces du complexe Entomophthora muscae (Cohn) Fresenius (Entomophthora schizophorae Keller & Wilding, E. muscae, s.str., et E. muscae "groupe B"). Les auteurs ont induit expérimentalement la formation de spores de repos de l'E. muscae groupe B, à partir du mois d'août jusqu'en février, alors qu'aucune spore de repos n'a jamais été observée chez les M. domestica infectées par l'E. schizophorae, ou chez des mouches infectées par l'E. muscae s.str., provenant de M. domestica. Lorsque qu'on maintient humide des cadavres de mort récente, contenant des spores de repos de l'E. muscae groupe B, des cystides émergent de l'abdomen; il s'agit de la première mention de cystides pour le genre Entomophthora. La production des spores de repos est significativement affectée à la fois par la température et par la souche d'E. muscae groupe B. Un plus grand nombre de mouches infectées forment des spores de repos lorsqu'on les maintient à 10°C pendant une semaine comparativement à une exposition constante à 22°C, mais la tendance des différentes souches de l'E. muscae groupe B à former des spores de repos persiste avec des températures changeantes. Après 4 mois d'incubation sous les conditions hivernales naturelles du Danemark, les spores de l'E. muscae groupe B germent sur eau gélosée à 20°C et sous une photopériode de 16 h : 8 h L:O, en moins d'une semaine, sans qu'on puisse observer de conidies de germination.Mots clés : Entomophthorales, complexe Entomophthora muscae, Diptères, Musca domestica, formation de spores de repos, germination de spores de repos.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]