Natural Photoperiod Research Articles

Analyses of mathematical models for Yangzhou geese egg-laying curves

Mathematical models of the egg-laying curves for Yangzhou geese exposed to both natural and artificial photoperiods were established to optimise the parameters for maximising geese reproductive performance and for the development of precision feeding methods. With the natural photoperiod, egg-laying starts in autumn when daily photoperiod decreases, but accelerates after the winter solstice, and reaches the peak in spring when photoperiod increases. An accumulating model was constructed based on the hypothesis that the egg-laying capacity of geese was determined by two components of the photoperiod: photo-stimulation and photo-inhibition. In addition, a second segmented model was constructed based on the hypothesis that the photo-stimulation only occurred with lengthening photoperiods after the winter solstice, and the lesser laying rate in autumn could be attributed to the non-photo-dependent animal-husbandry technologies. This model consists of a logistic model before the winter solstice, and an accumulating model after this solstice. The use of the logistic and accumulating resulted in more precise predictions that occurred with use of Model 1 with a greater R2 and lesser RMSE, AIC and BIC. Likewise, the egg-laying curves when there was consideration of artificial photoperiods could also be constructed with consideration of stimulatory and inhibitory photoperiodic effects. The model consists of an initial logistic and subsequently a quadratic polynomial model. With use of this model, there is consideration of changes in egg-laying patterns when there is a fixed photoperiod, with the model parameters reflecting the effects by photoperiod control-programs and age of the geese. In conclusion, new mathematical models have been developed to best fit egg-laying curves when there are both natural and artificial photoperiods. These models can contribute to development of precision-feeding technologies for breeding geese in future.

Advanced puberty triggered by bi-weekly changes in reproductive factors during the photolabile period in a male teleost fish, Dicentrarchus labrax L.

This study evaluated the impact of continuous light (LL) within the photolabile period on advanced puberty in juvenile male European sea bass. The exposure to an LL regime for 1 month, from August 15 to September 15 (LLa/s), was compared to a constant simulated natural photoperiod (NP) and constant continuous light conditions year-round (LLy). Somatic growth, hormone plasma levels, rates of testicular maturation and spermiation, as well as the mRNA levels of some reproductive genes were analyzed. Our results demonstrated that both LLa/s and LLy treatments, which include LL exposure during the photolabile period, were highly effective in inhibiting the gametogenesis process that affects testicular development, and clearly reduced the early sexual maturation of males. Exposure to an LL photoperiod affected body weight and length of juvenile fish during early gametogenesis and throughout the first year of life. Interestingly, LL induced bi-weekly changes in some reproductive factors affecting Gnrh1 and Gnrh2 content in the brain, and also reduced pituitary fshβ expression and plasmatic levels of 11-KT, E2, Fsh throughout early gametogenesis. We suggest that low levels of E2 in early September in the LL groups, which would be concomitant with the reduced number of spermatogonial mitoses in these groups, might indicate a putative role for estrogens in spermatogonial proliferation during the early gonadal development of this species. Furthermore, a significant decrease in amh expression was observed, coinciding with low plasma levels of 11-KT under LL regimes, which is consistent with the idea that this growth factor may be crucial for the progress of spermatogenesis in male sea bass.

The Effects of Seasonal Temperature and Photoperiod Manipulation on Reproduction in the Eastern Elliptio Elliptio complanata

The eastern elliptio Elliptio complanata is a species of freshwater mussel common to streams and rivers of the Atlantic Coast. Egg fertilization, larval brooding, and glochidial release are reported to occur within a period of several weeks during early to midsummer. In this study, mussels were exposed to manipulated photoperiod and water temperatures to prolong the availability of glochidia for use in artificial propagation and research. Brooding mussels were collected from Pine Creek, Tioga County, PA, in late December and were housed in groups subjected to one of four environmental treatments: natural temperature and photoperiod, 6-wk delay in natural conditions, 12-wk delay in natural conditions, and natural temperature and photoperiod with a winter low of 10°C. Reproductive activity was monitored for 1 y. Mussels subjected to natural conditions released mature glochidia between 16°C and 19°C with a photoperiod of 15 h of light. Temperature and photoperiod delays of 6 and 12 wk delayed reproduction proportional to the treatment, and constant 10°C winter low temperatures slightly shifted the timing of glochidial release. Survival during the study was high (96%–100%). Data indicate that the seasonal availability of E. complanata glochidia can be extended 3-fold using photoperiod and temperature manipulation.

The reproductive response to the male effect of 7- or 10-month-old female goats is improved when photostimulated males are used

The exposure of adult, female, Mediterranean goats during anoestrus to males with induced sexual activity via photostimulation, induces a very high percentage of ovulations. The present work examines the ability of photostimulated bucks to improve the male effect-induced reproductive response of young does over that induced by non-stimulated bucks. A 2×2 factorial experiment was designed, consisting of doe age and buck photoperiod treatments. During seasonal anoestrus, 41 does aged 7 (n=19) or 10 (n=22) months were subjected to the male effect on 10 April; half of each group was exposed to males rendered sexually active by prior exposure to 3 months of long days (16 h of light/day) from 31 October (PHOTO bucks), and half to males maintained under the natural photoperiod (CONTROL bucks). Oestrous activity was recorded daily by direct visual observation of the marks left by male-worn marking harnesses over the 32 days following the bringing of the sexes together (introduction). Doe body weight and body condition were determined weekly. Ovulation was detected by measuring plasma progesterone concentrations twice per week over the 3 weeks after introduction. The ovulation rate was assessed by transrectal ultrasonography. Fecundity, fertility, prolificacy and productivity were also determined. The interaction doe age × buck photoperiod treatment had no effect on any outcome. The percentage of females showing ovulation or oestrus was higher in the does exposed to PHOTO bucks (85% v. 43% for those exposed to CONTROL bucks) they also showed higher fertility (75% v. 43%) and productivity (1.05±0.17 v. 0.57±0.16 kids born per doe serviced) (all P values at least P<0.05). The 10-month-old group showed higher percentage of females showing ovulation, oestrus, fertility and productivity than the 7-month-old does after the male effect (females showing ovulation: 82% v. 42%; showing oestrus: 73% v. 42%; fertility: 73% v. 42% and productivity: 1.09±0.17 v. 0.47±0.14 goat kids born per doe serviced; respectively, all P values at least P<0.05). The present results show that the use of photostimulated males improves the reproductive performance of 7- and 10-month-old does, and may contribute towards increasing their productivity and lifetime reproductive performance.

Natural post-flowering photoperiod and photoperiod sensitivity: Roles in yield-determining processes in soybean

Promising yield-determining responses to artificial photoperiod manipulation during post-flowering phases have been identified in soybean [Glycine max (L.) Merrill]. These responses enhance resource capture as a result of changes in phase duration, and resource use efficiency as a result of changes in node production and pod development, alleviating intra-node pod interference. This work aims to evaluate the relevance of these responses under natural conditions and discriminate direct from indirect photoperiodic effects, that is, effects caused by changes in the capture of resources. Two field experiments were conducted with a combination of sowing dates, with similar pre- and different post-flowering photoperiod, indeterminate genotypes including near isogenic lines and commercial varieties with different photoperiod sensitivity, and shadings with different incident radiation during post-flowering. Longer post-flowering photoperiod and higher plant photoperiod sensitivity delayed crop development, particularly in lines with alleles E2, E3 or Clark background. This delay resulted in extra radiation capture and node production, which were positively related to yield. Direct photoperiodic effects on nodes per m2 were evidenced in response to changes in post-flowering photoperiod and plant photoperiod sensitivity. The distribution of available resources such as radiation in more nodes per m2 increased use efficiency. Longer post-flowering photoperiod and higher plant photoperiod sensitivity enhanced pod establishment on usually dominated positions such as lateral racemes, affecting pods per m2. Finding these relevant yield-determining effects under natural conditions suggests that processes related to post-flowering photoperiodic responses are a plausible way to enhance resource capture and use efficiency and yield in soybean production systems. In cropping systems in which the whole growing season is used to maximize yield, these post-flowering photoperiodic responses could be adopted at the expense of the pre-flowering phase duration.

Improvement of natural spawning of black flounder, Paralichthys orbignyanus (Valenciennes, 1839) by photothermal and salinity conditioning in recirculating aquaculture system

Black flounder (Paralichthys orbignyanus) is an important commercial and recreational species inhabiting marine and estuarine waters from Rio de Janeiro (Brazil) to San Matías Gulf (Argentina) from 1 to 30 m depth, with a great potential for aquaculture in coastal or internal brackish waters. It is an estuarine-dependent species whose adults reproduce in marine water during the spring and summer. Since 2003, the reproduction of flounder broodstock in a recirculating aquaculture system (RAS) subject to a photothermal period and constant salinity of 34 psu has been carried out at the National Institute for Fisheries Research and Development (INIDEP). Final maturation of broodfish was regularly achieved through the use of a photoperiod and water temperature regimen simulating natural seasonal changes over a 10-month period, reaching 19–20 °C and 16 h L:8 h D by February. These spawning events were unstable and unpredictable, with wide variations in quality and quantity of eggs. Control of the reproductive cycle and development of cultured broodstocks are basic requirements for a successful aquaculture industry. In order to acquire a more precise control of egg production, the effect of salinity variation upon the quantity and quality of spawning eggs of the flounder broodstock in a RAS during three reproductive seasons was evaluated. For that purpose, salinity was changed according to photoperiod and temperature variations along the year as: a) fall-winter, 16–12 °C, salinity 25–15 psu, natural photoperiod at low light intensity (10 lx), and b) spring-summer, 16–19 °C, salinity 15–34 psu, artificial photoperiod and mean light intensity (200 lx). The result of the present study indicated that the combination of photothermal and salinity regimes effectively extended reproductive activity in the broodstock tank and increased both the number of spawning events and the amount of eggs in relation to previous years. 2015–2016 and 2016–2017 reproductive seasons lasted for >150 days, reporting a total of 52 and 53 spawning events and reaching 14,289,661 and 17,593,888 eggs released, of which 37.8% and 32.5% were viable eggs, respectively. The 2017–2018 reproductive season lasted 106 days with 55 spawning events and 27,548,896 eggs released (61.0% viable eggs), reaching the greatest number of total eggs obtained in any season at INIDEP since 2003.

When and where to hatch? Red-eyed treefrog embryos use light cues in two contexts.

Hatching timing is under strong selection and environmentally cued in many species. Embryos use multiple sensory modalities to inform hatching timing and many have spontaneous hatching patterns adaptively synchronized to natural cycles. Embryos can also adaptively shift their hatching timing in response to environmental cues indicating immediate threats or opportunities. Such cued shifts in hatching are widespread among amphibians; however, we know little about what, if anything, regulates their spontaneous hatching. Moreover, in addition to selection on hatching timing, embryos may experience benefits or suffer costs due to the spatial orientation of hatching. Amphibian eggs generally lack internal constraints on hatching direction but embryos might, nonetheless, use external cues to inform hatching orientation. The terrestrial embryos of red-eyed treefrogs, Agalychnis callidryas, hatch rapidly and prematurely in response to vibrational cues in egg-predator attacks and hypoxia if flooded. Here we examined A. callidryas’ use of light cues in hatching timing and orientation. To assess patterns of spontaneous hatching and the role of light cues in their diel timing, we recorded hatching times for siblings distributed across three light environments: continuous light, continuous dark, and a 12L:12D photoperiod. Under a natural photoperiod, embryos showed a clear diel pattern of synchronous hatching shortly after nightfall. Hatching was desynchronized in both continuous light and continuous darkness. It was also delayed by continuous light, but not accelerated by continuous dark, suggesting the onset of dark serves as a hatching cue. We examined hatching orientation and light as a potential directional cue for flooded embryos. Embryos flooded in their clutches almost always hatched toward open water, whereas individual eggs flooded in glass cups often failed to do so, suggesting the natural context provides a directional cue. To test if flooded embryos orient hatching toward light, we placed individual eggs in tubes with one end illuminated and the other dark, then flooded them and recorded hatching direction. Most embryos hatched toward the light, suggesting they use light as a directional cue. Our results support that A. callidryas embryos use light cues to inform both when and where to hatch. Both the spatial orientation of hatching and the timing of spontaneous hatching may affect fitness and be informed by cues in a broader range of species than is currently appreciated.

Chemical Signals of Conspecifics and Their Role in Seasonal Relationships in the Mongolian Hamster (Allocricetulus curtatus) (Cricetinae, Rodentia)

Abstract—The hormonal response of Mongolian hamster Allocricetulus curtatus males to the urine and midventral gland secretion (MVGS)) of conspecific females during several seasons was studied. The animals were kept under natural photoperiod and temperature. In autumn no significant changes in the testosterone level in the blood of males in response to any of the exposed signals were observed. In winter and summer, this parameter increased in response to the diestrous female odors of urine and MVGS . In the spring the urine of conspecific estrous females stimulated a significant increase in the levels of both testosterone and cortisol. Moreover, the cortisol level did not increase in response to exposure of the odors of diestrous females in any season of the year. The level of progesterone significantly increased only when MVGS was exposed in the spring and summer periods, and the absolute values of this parameter were significantly higher in spring than in summer. Differences in responses to chemical signals in two closely related species (Eversmann’s and Mongolian hamsters) are discussed in connection with the peculiarities of the intraspecific social relationships.

The effects of a prolonged photoperiod and light source on growth, sexual maturation, fin condition, and vulnerability to fungal disease in brook troutSalvelinus fontinalis

The effects of an artificially prolonged photoperiod on growth, survival rate, colouration, and sexual maturation in brook trout Salvelinus fontinalis during pre- and post-spawning periods from 21 June to 06 November were investigated. Fish of mean initial weight ˜150 g were reared at ambient photoperiod as well as with an artificially prolonged photoperiod produced by either a light-emitting diode or a metal-halide light. The fish groups subjected to a prolonged period of artificial light grew significantly larger and had a higher survival rate (p < 0.05), regardless of sex, and showed lower occurrence of fungal disease compared to controls reared in the natural photoperiod. We found a significantly higher number of sexually mature fish in the control groups compared with experimental groups. The increased photoperiod effectively delayed gonad development and increased somatic growth in both male and female brook trout, and also increased resistance to fungal disease. The increased photoperiod produced an observable difference in fish colouration, with control groups exhibiting more intensive spawning colouration.

Artificial long-day photoperiod in the subtropics increases body weight in goat kids born in the autumn

To determine whether exposure to artificial long days increases the body weight of subtropical goat kids born in autumn, sixty-four goat kids were distributed in a completely randomized design with a factorial arrangement. Experimental groups consisted of two photoperiod treatments (natural or artificial photoperiod, 16 h light: 8 h darkness), and two suckling types (natural or artificial). The mean body weight, recorded at day 27 of age, was higher in goat kids subjected to artificial long days (7.7 ± 0.2 kg) than in those maintained under a natural photoperiod (7.0 ± 0.2 kg; P < 0.05). The mean daily gain was higher in light-treated kids (163 g/d) than in those maintained on a natural photoperiod (141 g/d; P < 0.001). Likewise, the mean blood glucose concentration was higher in goat kids submitted to artificial long days (102.0 ± 1.3 mg/dL) than in those kids maintained on the natural photoperiod (92.5 ± 1.3 mg/dL; P < 0.001). The suckling type had an effect on the plasma insulin-like growth factor-1 concentrations (IGF-1) of the kids (P < 0.01), and this effect was more pronounced in goat kids under artificial long days (P < 0.05). The results of the present study show that in subtropical goat kids born during the autumn, exposure to an artificial long-day photoperiod promotes a high body weight during the early phase of growth, independent of whether they are reared or not by their dams. In addition, these results also showed that, depending on suckling type, exposure to artificial long days increase the concentrations of IGF-1 in goat kids.

The use of photoperiods to provide year round spawning in lumpfish Cyclopterus lumpus

In order to provide year round spawning broodstock, lumpfish (initial size 746 g and 24.9 cm) were reared under four different photoperiod regimes from January 2017 to July 2018. One group was reared under simulated natural photoperiod (LDN, control group) for Tromsø (70°N). The second group was transferred to continuous light (LD240) on 30 January 2017 and reared at LD24:0 throughout the trial period. Two compressed and phase advanced photoperiods were also established. Both groups were moved from LDN to LD24:0 on 30 January 2017, and after that reared at compressed natural photoperiods where the annual photoperiod was compressed down to six months (L6) or nine months (L9) for the duration of the study. Spawning time was shifted in both compressed groups during both years of the study. Spawning activity in the second year of the study was higher and followed more closely the expected spawning period in the compressed and the LDN groups. Spawning in the LD240 group was spread out over the experimental period with no distinct peak in spawning. A seasonal and pronounced drop in condition factor was found for females in the L9, L6 and the LDN groups. This post-spawning loss in condition was closely related to the spawning activity of each group. The current findings suggest that photoperiod has a strong influence on the timing of lumpfish maturation and can be used as an efficient and inexpensive tool to secure lumpfish reproduction operations i.e. year-round supply of egg and milt and/or timing with optimal temperature regimes.

Description of the Annual Reproductive Cycle of Wreckfish Polyprion americanus in Captivity

Successful spontaneous reproduction and the production of viable offspring of wild fish in captivity can take some years of adaptation, and may also involve different environmental conditions, sex ratios and densities compared to natural populations. We followed the reproductive cycle of wreckfish Polyprion americanus—a late maturing, deep-sea benthic species—in captivity in three different broodstocks in Spain under natural photoperiod and temperature, and one broodstock in Greece under a constant temperature of 16 °C for two consecutive years, to describe the reproductive cycle of the species and the associated sex steroid hormone profiles. Oogenesis begun in the fall and post-vitellogenic oocytes of 1250 μm were present between March and June. Males were in spermiation condition and produced good-quality sperm throughout the year, regardless of the temperature profile to which they were exposed. Some females completed oogenesis, underwent oocyte maturation, and spawned spontaneously under both constant and fluctuating temperatures. The sex steroid hormones of both males and females followed the already-known profiles during fish gametogenesis, except for 17,20β-dihydroxy-progesterone, which did not seem to be related to either female or male maturation. The female reproductive dysfunctions that were identified included (a) the arrest of oogenesis at the cortical alveoli stage in certain females; (b) the failure to undergo oocyte maturation in others; and (c) the production of large percentages of unfertilized eggs from the females that spawned spontaneously. Our study suggests that reproduction in captivity is possible in wreckfish maintained under typical marine aquaculture conditions, but that reliable spawning and production of high-quality eggs may require some years of adaptation to captivity, before the reproductive dysfunctions will be overcome.

Artificial light at night and captivity induces differential effects on leukocyte profile, body condition, and erythrocyte size of a diurnal toad

Light pollution or artificial lighting at night (ALAN) is an emerging threat to biodiversity that can disrupt physiological processes and behaviors. Because ALAN stressful effects are little studied in diurnal amphibian species, we investigated if chronic ALAN exposure affects the leukocyte profile, body condition, and blood cell sizes of a diurnal toad. We hand-captured male toads of Melanophryniscus rubriventris in Angosto de Jaire (Jujuy, Argentina). We prepared blood smears from three groups of toads: "field" (toads processed in the field immediately after capture), "natural light" (toads kept in the laboratory under captivity with natural photoperiod), and "constant light" (toads kept in the laboratory under captivity with constant photoperiod/ALAN). We significantly observed higher neutrophil proportions and neutrophils to lymphocytes ratio in toads under constant light treatment. In addition, we observed significantly better body condition and higher erythrocyte size in field toads compared with captive toads. In summary, ALAN can trigger a leukocyte response to stress in males of the diurnal toad M. rubriventris. In addition, captivity can affect the body condition and erythrocyte size of these toads.

MATURAÇÃO OVARIANA DE Astyanax altiparanae APÓS DESOVA EM SISTEMA DE RECIRCULAÇÃO DE ÁGUA

Neste estudo, avaliamos a possibilidade de obtenção de desovas sucessivas de Astyanax altiparanae mantidos em biotério. Para isso, 104 indiví­­duos foram distribuí­­dos aleatoriamente em quatro caixas (10 fêmeas e 16 machos em cada) e mantidos a uma temperatura média de 29,24 ± 0,42°C, sob fotoperí­­odo natural, por 30 dias. No iní­­cio do experimento, machos e fêmeas foram induzidos í­Â reprodução com uma dose de extrato de hipófise de carpa (6 mg kg-1). Posteriormente, amostras de ovário (para cálculo do í­­ndice gonadosomático e avaliação estereológica) e de sangue (para avaliação de esteroides) foram coletadas de oito fêmeas (duas por caixa) nos seguintes perí­­odos: imediatamente após a indução hormonal (dia 0) e 1, 6, 16 e 30 dias após a desova. No dia 6, as fêmeas desovadas já apresentavam ovários maduros completos similares aos descritos no dia 0. No dia 6 não foram mais observados complexos pós-ovulatórios, indicando que a sua reabsorção foi relativamente rápida. Concomitantemente, os ní­­veis de esteroides aumentaram gradativamente até o dia 6, corroborando uma atividade vitelogênica intensa neste perí­­odo. Neste estudo demonstramos que fêmeas de A. altiparanae apresentam-se aptas para indução hormonal seis dias após a reprodução, quando mantida a 29,24 ± 0,42 ° C, em um sistema mantido com água recirculada.

Efficiency of night interruption treatments with red and far-red light-emitting diodes (LEDs) in preventing bud set in Norway spruce seedlings

Terminal bud set can be prevented by interrupting night with short pulses of light when the natural photoperiod is too short to maintain growth. Norway spruce (Picea abies Karst.) seedlings originating from 61°N and 64°N were grown in growth chambers under conditions that mimic growth conditions in a heated greenhouse in early spring in Finland (experiment 1) or under constant growth conditions (experiment 2). The seedlings were exposed to the following night interruption (NI) treatments using light-emitting diodes (LEDs) that generated red (R, peak at 660 nm) and far-red (FR, peak at 735 nm) wavelengths in 20 s pulses at 15 min intervals: (i) red light alone (R); (ii) R combined with FR (R + FR); and (iii) control (no NI treatment). The R + FR treatment was more effective in preventing terminal bud set than the R treatment. Seedling responses depended on the provenance and growth conditions. The R treatment reduced the proportion of seedlings with terminal buds in the 61°N seedlings and delayed bud set in the 64°N seedlings. The fluctuating growth conditions or longer dark period between the photoperiod and NI treatments reduced the efficiency of the R + FR treatment. A combination of R and FR LEDs with adequate light intensity and duration is suitable for intermittent NI treatment in Norway spruce seedlings.

Effects of photoperiod on nutrient digestibility, hair follicle activity and cashmere quality in Inner Mongolia white cashmere goats.

ObjectiveThis study investigated the effects of photoperiod on nutrient digestibility, hair follicle (HF) activity and cashmere quality in Inner Mongolia white cashmere goats.MethodsTwenty-four female (non-pregnant) Inner Mongolia white cashmere goats aged 1 to 1.5 years old with similar live weights (mean, 20.36±2.63 kg) were randomly allocated into two groups: a natural daily photoperiod group (NDPP group:10 to 16 h light, n = 12) and a short daily photoperiod group (SDPP group: 7 h light:17 h dark, n = 12). All the goats were housed in individual pens and fed the same diets from May 15 to October 15, 2015. The digestibility of crude protein (CP), dry matter (DM), and neutral detergent fiber (NDF) were measured in different months, along with secondary hair follicle (SHF) activity, concentration of melatonin (MEL), and cashmere quality.ResultsAlthough there was no significant difference in the live weights of goats between the SDPP and NDPP groups (p>0.05), the CP digestibility of goats in the SDPP group was significantly increased compared to the NDPP group in July, September, and October (p<0.05). For the DM and NDF digestibility of goats, a significant increase (p<0.05) was found during in September in the SDPP group. Furthermore, compared to the NDPP group, the SHF activity in July, the MEL concentration in July, and the cashmere fiber length and fiber weight in October were significantly increased in the SDPP group (p<0.05).ConclusionThe cashmere production of Inner Mongolia white cashmere goats was increased without obvious deleterious effects on the cashmere fibers in the SDPP group (metabolizable energy, 8.34 MJ/kg; CP, 11.16%; short daily photoperiod, 7 h light:17 h dark).

Comparative evaluation of daily rhythm of urinary excretion in Equus caballus and Bos taurus by means of fractional clearance

ABSTRACTThe aim of this study was to evaluate the daily variations of urinary excretion of the main electrolytes in Equus caballus and Bos taurus maintained under natural photoperiod. Animals were housed in individual indoor stalls under natural conditions. Urine and blood samples were taken from all the subjects every 4 h for 24 h period and were analyzed to assess the creatinine, calcium, phosphorus, magnesium, and chloride concentration. The fractional excretions of Na (%CrNa), K (%CrK), Cl (%CrCl), P (%CrP), Ca (%CrCa), and Mg (%CrMg) were calculated. Daily oscillations with nighttime acrophases of %CrNa, %CrK, and %CrCl are observed in horse; the acrophases of the parameters which resulted periodic in cow, including %CrNa, %CrCa, and %CrMg, are verified during the light phase. This study brings a contribution to the knowledge of the periodic phenomenon of the urinary excretion in the equine and bovine species. The results suggest that horse and cow are characterized by different circadian patterns for renal fractional clearance and that in these species, in addition to the external circadian stimuli, the renal excretion rhythms are also controlled by a self-sustained intrinsic renal clock that contribute to define the temporal patterns (daytime and nighttime).

Effects of C/N ratio and light on ammonia nitrogen uptake in Litopenaeus vannamei culture tanks

A 49-day trial was conducted to study the effect of the C/N ratio and light on water quality, growth performance, and antioxidant enzyme activities in hepatopancreas and plasma of Litopenaeus vannamei juveniles in an outdoor tank system. Four treatments with three replicates were created: heterotrophic without light (HD), heterotrophic with light (HL), chemoautotrophic without light (CD), and chemoautotrophic with light (CL). The HD and CD systems were kept in the dark and natural photoperiod was maintained in the HL and CL systems. Molasses was added to the heterotrophic treatments and the chemoautotrophic treatments received no added molasses. The accumulation of nitrite and nitrate was observed in CD. However, water quality parameters were managed properly in the HD and the heterotrophic treatments were less dependent on light than the chemoautotrophic treatments. Heterotrophic bacteria effectively assimilated ammonia and maintained good water quality in the HD and HL treatments after 14 days. The heterotrophic bacterial counts were not different among the four treatments. The total bacteria counts tended to be higher in the heterotrophic systems than the chemoautotrophic systems, but the difference was not significant. The CL treatment had the highest survival rate, lowest feed conversion ratio (FCR), and the lowest total antioxidant capacity (T-AOC), glutathione (GSH) and malondialdehyde (MDA) concentrations in the hepatopancreas indicating better health status of the shrimp. These results indicate that differences in light and C/N management can lead to substantial disparities in system function and performance of shrimp.

Pérdida de semillas en fase de pre-dispersión en dos especies de Prosopis (Fabacea: Mimosoidea) del Desierto del Monte, Argentina

Pre-dispersal flters imposed on the seed stage can alter the likelihood of seed dispersal. We evaluate pre-dispersal seed loss due to predation by insects and abortion in Prosopis flexuosa and P. chilensis . This study was conducted in two protected areas in the Monte Desert. We collected P. flexuosa and P. chilensis fruits from different trees, from two plots and two years. Samples were maintained for 50 days in translucent PVC boles stored in a laboratory under stable temperature (25 °C) and natural photoperiod, awaiting the emergence of insects. Then we opened the fruits and individually examined all seeds to determine their condition. We found that total pre-dispersal seed loss was 32% in P. flexuosa and 21% in P. chilensis . Seed predation by insects was the major source of pre dispersal seed loss (19% in P. flexuosa and 14% in P. chilensis ). The main seed predator was the apionid weevil (Brentidae: Apioninae) in P. flexuosa , and bruchid beetles (Chrysomelidae: Bruchinae) in P. chilensis . Some bruchid beetles prey upon seeds, completing their life cycle, whereas others remain inside seeds (41% in P. flexuosa and 49% in P. chilensis , of total seed damaged by bruchid beetles). Seed abortion was another important source of seed loss, especially for P. flexuosa , but its cause still remains unknown. We show and discuss the extent of a proposed methodology to account for pre-dispersal seed predation that includes the immature stages of non-emergent bruchid. Pre-dispersal seed loss by insects and abortion represent an ecological flter that limits the amount of seeds available for dispersal and establishment of these species. Understanding seed loss process may contribute to know and predict Prosopis population dynamics, revealing the natural regeneration mechanisms to forest recovery. https://doi.org/10.25260/EA.18.28.2.0.576

Experimental evidence of masculinization by continuous illumination in a temperature sex determination teleost (Atherinopsidae) model: is oxidative stress involved?

The present study evaluates the influence of continuous light on phenotypic sex ratios in Chirostoma estor, a temperature sex determination animal model. Relative gene expression levels of 5 day old larvae were performed on two early gonad differentiation genes (sox9 and foxl2), two stress axis activation genes (gcr1 and crf) and four reactive oxygen species (ROS) antagonist effector genes (sod2, ucp2, gsr and cat). Two light treatments were applied from fertilization; control (12L:12D) simulated natural photoperiod and a continuous illumination photoperiod. By the end of the trial (12 weeks after hatching), differentiated and normal gonads were clearly identifiable in both treatments by histological observations. Regarding sex ratio, 73% of phenotypic males were found in continuous illumination compared with 40% in controls. Consistently, the sox9 gene (involved in early testis differentiation) showed an over expression in 64% of the individual larvae analysed compared with foxl2 (ovarian differentiation) suggesting a masculinization tendency in continuous illumination. On the other hand, only 36% of individuals showed the same tendency in the control treatment consistent with phenotypic sex ratios found under normal culture conditions. Relative gene expression results did not show significant difference in sod2, ucp2 and gcr1 levels, but cat, gsr and crf showed significantly higher expression levels in the continuous illumination treatment suggesting that both, the stress axis and ROS response mechanisms were activated at this time. This study suggests, a link between continuous light, oxidative stress and environmental sex determination in vertebrates. However, further research is necessary to describe this possible upstream mechanism that may drive some aspects of sexual plasticity in vertebrates.