Photoperiodic Cycle Research Articles

Photoperiodism, testosterone and adult neurogenesis in canaries (Serinus canaria).

Domestic strains of canaries (Serinus canaria) variably respond to photoperiod changes and apparently stay in breeding state for extended periods. Fife Fancy canaries are supposed to be similar to the native species living at 27-39° north where photoperiod significantly changes across the year. Our birds showed reproductive cycles when exposed to light regimes mimicking the annual cycle of photoperiod. However after 6 months in short days (SD: 8L:16D), males developed large testes, as observed by X-ray tomography, and intense singing. Switching to long days (LD: 16L:8D) did not further increase song rate nor testes size but increased song duration, number of syllables per song, and trill occurrence frequency. No sign of regression was observed after 12 weeks in LD but return to SD produced a rapid decrease in testes size and singing activity below values in birds maintained throughout in SD. Fife Fancy thus does not seem to develop absolute but only relative refractoriness. The relatively high singing activity expressed by SD-photosensitive males does not seem to depend on high testosterone (T) concentrations. Singing did not correlate with plasma testosterone (T). Treatment with ATD + Flutamide only marginally decreased song rate and did not affect song quality nor song control nuclei volume. These birds are either supersensitive to low T levels or their reproductive physiology is activated by other mechanisms. Neurogenesis is increased by T and by LD but the function of new neurons incorporated in HVC is poorly understood. We developed a procedure based on X-ray focal irradiation to deplete neural progenitors adjacent to HVC and study the functional consequences. The decrease in neurogenesis increased the variability of T-induced songs in females and decreased their bandwidth. Neurogenesis in HVC thus plays a role in song production and X-ray focal irradiation represents an excellent tool to analyze adult neurogenesis.

The Effect of Various Photoperiodic Conditions and Zn2+ Concentrations on Growth Rate and Metabolite Content in Euglena sp.

The application of Euglena as a carbon capture organism has generated considerable interest among scientists. Through the photosynthesis process, many kinds of metabolites are produced by Euglena, such as lipids, proteins, and pigments. Due to the metabolites produced by Euglena, it is vital to optimize the carbon capture ability and cell growth rate by adding Zn2+ content and giving photoperiodic into Euglena culture. The purpose of this study is to identify the optimal photoperiod and Zn2+ concentration to increase the growth rate, biomass, and metabolite content of Euglena sp. This study is a laboratory experiment involving the cultivation of Euglena sp. in various photoperiod cycles (light: dark), namely 24:0, 12:12, 14:10, and 16:8. In addition, Euglena sp. was also cultivated using different concentrations of Zn2+ (0 ppm, 5 ppm, 10 ppm, and 15 ppm). The growth of Euglena sp. was monitored for 18 days before being harvested every three days to measure the research parameters, including primary and secondary metabolites. The results showed that the photoperiod treatment and various concentrations of Zn2+ had a significant impact (P<0.05) on the growth rate, biomass, lipid, carbohydrate, protein, chlorophyll, and carotenoid levels of Euglena sp.

Spawning performance of 3-year-old Pacific bluefin tuna Thunnus orientalis exposed to a phase-shifted photoperiod regime

The effects of a phase-shifted photoperiod regime to advance maturation and spawning were examined in 3-year-old Pacific bluefin tuna Thunnus orientalis. Fish in three broodstock groups reared in sea cages were separately transferred at age 2 years to land-based indoor tanks, in June or July, in each of the three trial years; they were then exposed to a 2- or 2.5-month advanced photoperiod cycle. In all three trials, when the fish were 3 years old, the spawning was initiated 2–3 months before the normal spawning season. During the continuous spawning, the fish were maintained under a constant long photoperiod of 15 h light and water temperature of 24–25 °C. In the 2019/2020 trial, 114 spawning days were recorded between March and July 2020 in a group of 28–30 females and 23–28 males; in the 2020/2021 trial, 100 days were recorded between April and July 2021 in a group of 30–32 females and 20–22 males; and in the 2021/2022 trial, 138 days were recorded between April and September 2022 in a group of 6–8 females and 7–10 males. The number of eggs produced daily peaked 1–2 months after the onset of spawning and thereafter decreased. Egg diameter showed a negative relationship with days elapsed from the onset of spawning. The analysis of parentage assignment of the larvae in the 2019/2020 trial showed that at least 50% of females and 75% of males contributed to the spawning, whereas histological observation of gonads in the 2020/2021 trial showed that 33% of females completed vitellogenesis and 85% of males reached spermiation. The analysis of parentage assignment also showed that the spawning interval of females declined between March and June, and the mean number of eggs produced daily per female peaked in April and decreased until June. Our observations demonstrate that manipulation of a phase-shifted photoperiod regime is a powerful technique for advancing maturation and spawning in the Pacific bluefin tuna at age 3 years.

Effect of carbon dots supplementation in Chlorella vulgaris biomass production and its composition

Microalgae cultures have an excellent ability to capture CO2 and produce high, medium, and low valuable biocompounds such as proteins, carbohydrates, lipids, pigments, and polyhydroxyalkanoates; those compounds have shown excellent properties in the pharmaceutical, cosmetic, food, and medical industries. Recently, the supplementation of carbon dots (CDs) in autotrophic microalgae cultures has been explored as a new strategy to increase light capture and improve photoluminescence, which in turn enhances biomass growth and biocompounds production. In this work, we synthesized CDs through a simple carbonization method using orange juice as a natural precursor. The green synthesized CDs were analyzed in detail through characterization techniques such as Fourier-transform infrared spectroscopy (FTIR), UV–visible, fluorescence spectroscopy, and ζ potential analysis. Moreover, CDs were added to Chlorella vulgaris to analyze the response under different photoperiod cycles and CDs dosages. The optimal results were obtained with the addition of 0.5 mg l−1 of CDs under a photoperiod cycle of 16 h:8 h (light:dark). In these conditions, a maximum biomass production of 2.12 g l−1 was observed, which represents an enhancement of 112% and 17% in comparison to the control samples under the photoperiod of 12 h:12 h and 16 h:8 h (light/dark), respectively. Furthermore, the production of lipids, proteins, and carbohydrates was significantly increased to 249 mg g−1, 285 mg g−1, and 217 mg g−1 dry weight, respectively. These results suggest that the addition of CDs enhances cell growth and increases the production of lipids and proteins, being a strategy with great potential for the food and pharmaceutical industries.

Thick-billed Murres in breeding pairs migrate and overwinter far apart but in similar photic environments

Scheduling between mates in species with long-term pair bonds can be essential for positive fitness. The annual cycle in photoperiod is the primary environmental cue used by many animals to synchronize behavior and physiology among members of a population, and animals that migrate must have similar annual schedules to ensure successful breeding. However, we know little about whether members of mated pairs in migratory species experience similar photic environments across the year, which could allow for synchronization in annual phenology. Here, we used light-based geolocation to estimate positions of mated pairs of Thick-billed Murres (Uria lomvia, a seabird a.k.a. Brünnich’s Guillemot) which bred above the northern polar circle in Greenland. We tested the hypothesis that individuals in mated pairs occur in more similar locations and photic environments than randomly matched females and males. We found no difference in the amount of spatial separation or in the photic environment between mates and randomized heterosexual pairings. In general, the distance between females and males ranged from 1,198.5 km during August to 737.4 km during January. The sexes remained in photic environments with highly correlated photoperiods and moderately correlated times of solar noon in UTC. The spatial separation of, but similar photic environments experienced by, female and male murres regardless of pair status is probably adaptive by facilitating the synchronization of annual schedules between sexes, while allowing individuals in mated pairs the freedom to pursue the best foraging opportunities during migration and overwintering independent of their mate.

Effects of dopamine and melatonin treatment on the expression of the genes associated with artificially induced sexual maturation in Japanese eel, Anguilla japonica.

Japanese eel (Anguilla japonica) is a commercially important fish species in Asia. Understanding factors like photoperiod, temperature, and lunar cycles is crucial for successful aquaculture and managing its reproduction. Melatonin and dopamine (DA) are essential for regulating reproduction in vertebrates, including fish. This study investigated the effects of melatonin and DA on the reproductive system of mature male Japanese eels to better understand reproductive regulation in fish. To clarify the effects of these hormones on sexual maturation in eels, a critical stage in the reproductive process, sexual maturation was induced by injecting human chorionic gonadotropin, which stimulates the production of sex hormones. To check the effect of melatonin and DA on sexual maturation, DA, melatonin, and DA + domperidone were intraperitoneally injected into fish from each group (six per treatment) at a dose of 1 mg/kg body weight. The fish were then examined using quantitative RT-PCR by comparing the messenger RNA level of reproduction-related genes (gonadotropin releasing hormone 1; gnrh1, gonadotropin releasing hormone 2; gnrh2, follicle stimulating hormone; fshβ, luteinizing hormone; lhβ and DA receptor 2b; d2b), involved in the gonadotropic axis in eels, to those that received a control injection. The results indicate significant differences in the expression levels of gnrh1, gnrh2 and d2b in the brain and d2b, fshβ, lhβ in the pituitary at different stages of sexual maturation. Melatonin appears to enhance the production of sex gonadotropins, whereas DA inhibits them. These findings suggest an interaction between melatonin and DA in regulating reproduction in Japanese eels.

Artificial nighttime lighting impacts Plasmodium falciparum mature stage V gametocytes infectivity in Anopheles stephensi

BackgroundMalaria is one of the most important vector-borne diseases of humans with an estimated 241 million cases worldwide in 2020. As an urban and periurban mosquito species, Anopheles stephensi is exposed to artificial human stimuli like light that can alter many aspects of mosquito behaviour, physiology and metabolism. Therefore, fluctuations in the light environment may influence the host, parasite and/or mosquito biology and hence modulate risk for disease transmission. In this study, the effect of artifitial light at night on mosquito infectivity by Plasmodium falciparum during the first hours of blood digestion was tested.MethodsA total of three independent standard membrane feeding assays were performed to artificially fed septic and aseptic mosquitoes with P. falciparum infected blood. After blood feeding, females were transferred to incubators with different photoperiod cycles, so digestion occurred under day artificial light or dark. At 7 and 16 days post blood feeding, mosquitoes were dissected for midguts and salivary glands, respectively. Percentage of mosquitoes fed, percentage of prevalence and P. falciparum oocyst intensity between septic and aseptic mosquitoes in the two different photoperiod regimes, were compared using a Kruskal-Wallis test followed by a Dunn´s multiple comparison test .ResultsThe exposition of mosquitoes to light after they took an infected blood meal has a negative effect on the successful progression of P. falciparum in the mosquito midgut. Antibiotic treatment significantly incremented the number of oocysts per midgut. Photophase significantly reduced the median oocyst intensity in both septic and aseptic mosquitoes. The percentage of oocyst reduction, understood as the percentage of reduction in the mean oocyst intensity of the parasite in the mosquito midgut between photophase and scotophase, was 51% in the case of aseptic mosquitoes and 80% for septic mosquitoes, both in the photophase condition.ConclusionAlthough there are still many gaps in the understanding of parasite-mosquito interactions, these results support the idea that light can, not only, influence mosquito biting behaviour but also parasite success in the mosquito midgut. Hence, light can be considered an interesting additional mosquito-control strategy to reduce mosquito-borne diseases.

Light Influences the Growth, Pigment Synthesis, Photosynthesis Capacity, and Antioxidant Activities in Scenedesmus falcatus.

Light plays a significant role in microalgae cultivation, significantly influencing critical parameters, including biomass production, pigment content, and the accumulation of metabolic compounds. This study was intricately designed to optimize light intensities, explicitly targeting enhancing growth, pigmentation, and antioxidative properties in the green microalga, Scenedesmus falcatus (KU.B1). Additionally, the study delved into the photosynthetic efficiency in light responses of S. falcatus. The cultivation of S. falcatus was conducted in TRIS-acetate-phosphate medium (TAP medium) under different light intensities of 100, 500, and 1000 μmol photons m-2·s-1 within a photoperiodic cycle of 12 h of light and 12 h of dark. Results indicated a gradual increase in the growth of S. falcatus under high light conditions at 1000 μmol photons m-2·s-1, reaching a maximum optical density of 1.33 ± 0.03 and a total chlorophyll content of 22.67 ± 0.2 μg/ml at 120 h. Conversely, a slower growth rate was observed under low light at 100 μmol photons m-2·s-1. However, noteworthy reductions in the maximum quantum yield (Fv/Fm) and actual quantum yield (Y(II)) were observed under 1000 μmol photons m-2·s-1, reflecting a decline in algal photosynthetic efficiency. Interestingly, these changes under 1000 μmol photons m-2·s-1 were concurrent with a significant accumulation of a high amount of beta-carotene (919.83 ± 26.33 mg/g sample), lutein (34.56 ± 0.19 mg/g sample), and canthaxanthin (24.00 ± 0.38 mg/g sample) within algal cells. Nevertheless, it was noted that antioxidant activities and levels of total phenolic compounds (TPCs) decreased under high light at 1000 μmol photons m-2·s-1, with IC50 of DPPH assay recorded at 218.00 ± 4.24 and TPC at 230.83 ± 86.75 mg of GAE/g. The findings suggested that the elevated light intensity at 1000 μmol photons m-2·s-1 enhanced the growth and facilitated the accumulation of valuable carotenoid pigment in S. falcatus, presenting potential applications in the functional food and carotenoid industry.

Growth and Metabolite Enhancement of Acidophile Euglena sp. Isolated from Indonesia under Different Photoperiod Cycles

Abstract Euglena sp. is a unicellular, flagellated microalga considered one of the most promising microalgal feedstock species for biofuels. Reducing the level of liquid waste pollutants can be done biologically by using microalgal organisms. Its metabolites, including lipids, proteins, carbohydrates, and pigments, are appropriate for producing biorefinery products such as biodiesel and jet fuels. They can be isolated from extreme environments, such as highly acidic and ammonia-rich environments, that are not conducive to their proliferation. This study sought to determine the effect of the photoperiod or (light: dark) cycle (24 L:0 D, 12 L:12 D, 14 L:10 D, and 16 L:8 D) on the growth, biomass, metabolite content consisting of lipids, carbohydrates, and proteins, and the rate of CO­2 uptake by Euglena sp. As stated previously, the study was conducted by cultivating Euglena sp. on a laboratory scale with four photoperiod regimens. The results indicated that optimal growth, biomass content, and metabolite content were obtained with a 24 D:0 L lighting cycle. The control treatment (24 L: 0 D) had the highest biomass productivity (0.032 g.L-1.day-1 ± 0.004), lipid content (0.387 g.L-1 ± 0.031), protein content (0.542 mg.Ml-1 ± 0.007), carbohydrate content (0.409 x104 g.L-1), chlorophyll a (6.237 g.L-1 ± 0.184), chlorophyll b (2.838 g.L-1 ± 0.253), and total carotenoid (1.566 g.L-1 ± 0.105). Full light illumination (24 L:0 D) was significantly producing carotenoid content, including phaeophytin a, phaeophytin b, violaxanthin, 9’-cis-neoxanthin, dino xanthin, and fucoxanthin. Highlight Research The growth rate was higher when Euglena was cultivated under continuous illumination. The biomass productivity of Euglena increased significantly under continuous illumination. The metabolite content of Euglena (lipids, proteins, and pigments) was higher in continuous illumination.

Maintenance of permanent sexual activity throughout the year in seasonal bucks using short photoperiodic cycles in open barns

Seasonality of reproductive activity in rams and bucks is the major constraint in temperate and subtropical zones. Rapid alternation between 1 month of short days and 1 month of long days (LD) over three years in lightproof buildings eliminates this seasonality. We examined if this would also work in open barns, using only supplementary light. Over two years, one group of bucks (n = 7) was subjected to alternate 1 month of LD and 1 month of permanent light (LD–LL) and another group (n = 7) to alternate 1 month of LD and 1 month of natural light (LD–NL). A simultaneous control group, used for both experiments (CG1, n = 6; CG2, n = 6), remained under natural photoperiod. BW, testis weight (TW), plasma testosterone (T) and cortisol (C) were evaluated in all bucks. CG1 and CG2 bucks showed identical dramatic seasonal variations in BW (stable or decreasing in summer), TW (from 85 ± 12 g in February to 127 ± 7 g in July) and T (from 2.7 ± 1.2 ng/mL in January–April to 24.3 ± 3.2 ng/mL in June–October). By contrast, BW of LD–LL and LD–NL bucks increased regularly during the experiment. From 5 and 9 months after the experiment onset, LD–LL and LD–NL bucks, respectively, maintained constant TW of 115 ± 5 g until the experiment end. After the first 3 months <5 ng/mL, T of LD–LL bucks remained constant (5–10 ng/mL) until the experiment end. By contrast, T of LD–NL bucks showed four periods of low (<5 ng/mL) and two periods of high concentrations (18.1 ± 2.6 and 11.9 ± 3.4 ng/mL). Plasma C remained low (5–8 ng/mL) and did not change with group or light treatment. These results show for the first time in any seasonal photoperiodic species that it is possible to maintain the sexual activity of males all year round in open buildings using alternating periods of LD and LL. By contrast, return to NL instead of LL every other month does not prevent seasonality in T concentration. These results raise interesting questions about the photoperiodic control of neuroendocrine regulation of seasonal sexual activity and suggest that these treatments can be used to manage males in open barns in farms and in artificial insemination centres. (Spanish and French versions of the full text are available as Supplementary Materials S1 and S2).

Differential transcriptome and metabolite profile with variable fluoride tolerance and altered genomic template stability in the identification of four fluoride-tolerant or fluoride-sensitive rice cultivars

Fluoride toxicity is the most commonly experienced challenge to rice plants due to irrigation with fluoride-polluted groundwater. In the present study, four hydroponically grown rice cultivars (Badshahbhog, Swarna, Sukumar and Shatabdi) were screened for fluoride tolerance on the basis of physiological and molecular parameters. Rice cultivars were maintained at 37 °C under 16/8 h light/dark photoperiodic cycle with 700 μmol photons m−2 s−1 intensity and relative humidity (50 %) in a plant growth chamber for 20 days. Treatment with NaF (50 mg L−1) caused considerable fluoride accumulation in Shatabdi which hindered its growth and triggered the formation of H2O2 and enhanced lipoxygenase and protease activity that eventually led to higher malondialdehyde formation and electrolyte leakage from the cells. This was accompanied with degradation of photosynthetic pigments (chlorophyll a, b, total chlorophyll, xanthophyll and carotenes) and inhibition in Hill activity. Higher formation of osmolytes (proline, amino acids and glycine betaine) and activity of enzymatic antioxidants (SOD, CAT, APX and GPX) reversed the effect of fluoride toxicity in Badshahbhog, concomitant with proper maintenance of the expression of gene concerned with photosynthetic mechanism (PsbA, PsbY, PsaH, PetC, PetH, Rbcs, Rca and rsp9) which preserved the photosynthetic machinery, providing sufficient energy to the seedlings to overcome the stressed conditions. RAPD profiling and GTS also established the superiority of Badshahbhog over the three cultivars, making it an efficient fluoride-tolerant variety.

Deciphering the biochemical regulation of metabolic pathways in abating stress-induced damages during co-exposure of arsenic and fluoride in a non-aromatic and an aromatic rice variety.

The aim of the current work was to decipher the systemic damage and biochemical defense machinery due to combined arsenic (5mg L-1 Na3AsO4) and fluoride (50mg L-1 NaF) stress in two rice cultivars viz., IR-64 (non-aromatic) and Gobindobhog (aromatic), grown for 14days, under 16/8h light/dark photoperiodic cycle at 32°C. Higher accumulation of arsenic and fluoride in Gobindobhog generated higher levels of H2O2 that caused higher electrolyte leakage, along with malondialdehyde and methylglyoxal formation. Higher oxidative damages severely compromised seed germination and led to chlorophyll loss, inhibition of root and shoot growth and fresh and dry weight of the seedlings. On the contrary, oxidative damage was less pronounced in IR-64, as compared to that of Gobindobhog, which can be attributed to higher accumulation of protective metabolites, i.e., osmolytes and antioxidants. Higher levels of osmolytes (proline, glycine betaine and amino acids) in IR-64 helped in maintaining the osmotic balance of the cells and theintegrity of the cell membrane. Additionally, up regulated activity of enzymatic antioxidants (catalase, superoxide dismutase, ascorbate peroxidase, glutathione peroxidase and glutathione S-transferase) along with elevated levels of non-enzymatic antioxidants (flavonoids, phenolics, xanthophylls and carotenoids) played a pivotal role in controlling oxidative damages and strengthening the defense machinery in IR-64, as compared to that of Gobindobhog where lesser enhancement in the level of the above mentioned protective metabolites was noted. The present work illustrated differential phytotoxicity in rice seedlings and elucidated the yet uncharacterized biohazard associated with arsenic and fluoride co-contamination, with better adaptive features of IR-64, compared to Gobindobhog, which appeared as the sensitive variety.

Dual phytoremediation and biochar production by Eichhornia crassipes in hydroponic system receiving different 1,4-dioxane dosages

This study focuses on applying phytoremediation as a low-effective and simple process to treat wastewater laden with 1,4 dioxane (DIOX). A floating macrophyte (Eichhornia crassipes) was cultivated under hydroponic conditions (relative humidity 50–67%, photoperiod cycle 18:6 h light/dark, and 28-33 °C) and subjected to different DIOX loads between 0.0 (control) and 11.5 mg/g fresh mass (FM). The aquatic plant achieved DIOX and chemical oxygen demand (COD) removal efficiencies of 76–96% and 67–94%, respectively, within 15 days. E. crassipes could tolerate elevated DIOX-associated stresses until a dose of 8.2 mg DIOX/g, which highly influenced the oxidative defense system. Malondialdehyde (MDA) content, hydrogen peroxide (H2O2), and total phenolic compounds (TPC) increased by 7.3, 8.4, and 4.5-times, respectively, in response to operating the phytoremediation unit at a DIOX load of 11.5 mg/g. The associated succulent value, proteins, chlorophyll-a, chlorophyll-b, and pigments dropped by 39.6%, 45.8%, 51.5%, 80.8%, and 55.5%, respectively. The suggested removal mechanism of DIOX by E. crassipes could be uptake followed by phytovolatilization, whereas direct photodegradation from sunlight contributed to about 19.36% of the total DIOX removal efficiencies. Recycling the exhausted E. crassipes for biochar production was a cost-efficient strategy, making the payback period of the phytoremediation project equals to 6.96 yr.

A correlation between seasonally changing photoperiod, whole body lipid, and condition factor in juvenile spring Chinook salmon (Oncorhynchus tshawytscha).

The regulation of lipid stores is a central process for the physiology and ecology of fishes. Seasonal variation in lipid stores has been directly linked to survival of fishes across periods of food deprivation. We assessed whether a seasonally changing photoperiod was correlated to seasonal changes in energetic status to help better understand these important processes. Groups of first feeding Chinook salmon fry were introduced to a seasonal photoperiod cycle, but the point of entrance into the seasonal cycle varied from near the winter solstice (December), to either side of the spring equinox (February & May). Temperature and feeding rate were similar for all treatments. Subsequently, condition factor and whole body lipid content were assessed through a seasonal progression. Throughout most of the experiment, length and weight did not differ between the different photoperiod treatments, however whole body lipid and Fulton's condition factor did. Furthermore, changes in both whole body lipid and Fulton's condition factor in all treatment groups followed a similar seasonal pattern that was inversely related to day length (highest K and lipid levels found during days with the least light). These results suggest that regardless of age or size, there is a correlation between seasonal changes in photoperiod and changes in body composition in juvenile Chinook salmonids.

Reproductive performance of hair ewes and rams implanted with melatonin previous to the anestrus season in northwest Mexico.

Ovine reproductive behavior depends on annual photoperiodic cycle and its impact on endogenous melatonin secretion. In this regard, exogenous melatonin administration previous to the physiological anestrus period could modify the reproductive performance of sheep in the northwest of Mexico. Two independent studies were performed to evaluate such hypothesis in hair sheep implanted with melatonin prior to the anestrus season in latitudes 24° and 25° of Mexico. Study 1 involved 15 rams assigned to one of three treatments receiving 0mg (n=5), 18mg (n=5), or 36mg (n=5) of melatonin subcutaneously. Study variables were measured monthly since implantation (d0) and included testosterone concentration, scrotal circumference, mass motility, individual motility, and sperm concentration. Study 2 included 50 ewes assigned to one of two treatments receiving 0mg (n=25) or 18mg (n=25) of melatonin subcutaneously. In ewes, progesterone concentration and the frequency of females in anestrus were measured during the implantation (-30d), as well as at the beginning (0d) and at the end (45d) of the mating period, while pregnancy rate was determined by ultrasonography 45d after. Continuous variables were analyzed using a mixed effects model considering treatment, time, and the treatment by time interaction as fixed effects. Animal nested within treatment was the random effect. Binary variables were analyzed using the chi-square test. In males, melatonin improved testosterone and sperm concentrations (P<0.05), while in females, a 28% higher pregnancy rate was observed in implanted ewes (P<0.05). Therefore, melatonin enhanced reproductive parameters in both sexes and its exogenous administration previous to the anestrus season in northwest Mexico could be more effective in rams.

Some reproductive characteristics in common donkey male (Equus asinus)-A mini review

In contrary to most domestic livestock species, the common donkey (Equus asinus) is widely known as an animal with a marked seasonality in reproductive activity .The annual cycle of daily photoperiod has been identified as the determining factor in the sexual activity. A synthesis of the particularities of donkey reproduction is important and constitutes a basis of scientific reflection for managing asine livestock farms and to establish a well conservation plan for the different breeds around the world. It is necessary to have a perfect knowledge of the seasonal physiological changes in order to optimize the reproductive characteristics in donkeys.The objective of this paper is to review the current state of knowledge on the reproductionseasonality in common donkey. We start with a remainder of some anatomical of the genital apparatus and sexual behavior aspects. Moreover, the investigations undertaken by many authors reveal the influence of the season on testicular biometry, histology, seminal and hormonal parameters in male donkeys’ populations. In conclusion, despite scientific controversy on reproductive seasonal character in donkeys, it could likely be influenced by several factors mainly the photoperiod.

Plant Melatonin: Regulatory and Protective Role

Melatonin is an antioxidant that is widely distributed in plants and animals. It is a conservative molecule. In early studies, scientists often used isolation and identification techniques to observe whether the endogenous melatonin cycle in plants was related to the external photoperiod, plant growth, and development cycles, including seed germination, plant rooting, and floral induction. With the development of isolation and identification technology, there is ample evidence that plants possess a variety of melatonin-synthesis pathways. The comprehensive application of molecular biology, genomics, and computational biology has also led to a comprehensive understanding of the physiological functions of plant melatonin. In this paper, we not only highlight the candidate genes from Arabidopsis thaliana and Oryza sativa that might be contributing to increasing plant endogenous melatonin but also elucidate and characterize the role of melatonin in plant growth and development in response to biotic and abiotic stresses.

Heat stress and sperm production in the domestic cat

This study aimed to assess 1) the effect of high environmental temperatures on sperm production and 2) the effectiveness of a temperature-humidity index (THI) to predict the degree of thermal stress in a cat model. Semen collection was performed by electroejaculation for 18 mo in 20 tomcats maintained under controlled photoperiod. Still, temperature and humidity were not experimentally manipulated to describe the effect of natural climate conditions on seminal samples. Ejaculates (n = 512) were then grouped according to temperature records of the sampling day and compared by temperature and THI index. Significant lower sperm parameters and increase sperm tail abnormalities were observed during warm environments (temperature and THI). Concentration and total sperm count were the most affected parameters. Environmental temperatures of 28.5 °C with 54% relative humidity (THI = 77.07) and 27.9 °C with 66% humidity (THI = 77.84) were upper thresholds of moderate thermal stress. Moreover, days with relative humidity near 90% led to severe thermal stress with temperatures as low as 26.6 °C (THI = 78.88). The current study demonstrates the detrimental effect of high environmental temperatures on sperm quality in the domestic cat. This effect is observed at lower temperatures when high relative humidity is present. In this sense, the THI was a reliable predictor of the magnitude of thermal stress experienced by cats. Thus, cats from reproductive programs should be maintained under controlled photoperiod cycles with temperatures around 20 °C and humidity around 70% to avoid semen detrimental effects.

Shifts in growth light optima among diatom species support their succession during the spring bloom in the Arctic

Abstract Diatoms of the Arctic Ocean annually experience extreme changes of light environment linked to photoperiodic cycles and seasonal variations of the snow and sea‐ice cover extent and thickness which attenuate light penetration in the water column. Arctic diatom communities exploit this complex seasonal dynamic through a well‐documented species succession during spring, beginning in sea‐ice and culminating in massive phytoplankton blooms underneath sea‐ice and in the marginal ice zone. The pattern of diatom taxa sequentially dominating this succession is relatively well conserved interannually, and taxonomic shifts seem to align with habitat transitions. To understand whether differential photoadaptation strategies among diatom taxa explain these recurring succession sequences, we coupled laboratory experiments with field work in Baffin Bay at 67.5°N. Based on field data, we selected five diatom species typical of different ecological niches and measured their growth rates under light intensity ranges representative of their natural habitats. To characterize their photoacclimative responses, we sampled pigments and total particulate carbon, and conducted 14C‐uptake photosynthesis response curves and variable fluorescence measurements. We documented a gradient in species respective light intensity for maximal growth suggesting divergent light response plasticity, which for the most part align with species sequential dominance. Other photophysiological parameters supported this ecophysiological framing, although contrasts were always clear only between succession endmembers, Nitzschia frigida and Chaetoceros neogracilis. To validate that these photoacclimative responses are representative of in situ dynamics, we compared them to the chlorophyll a‐specific light‐limited slope (α*) and saturated rate of photosynthesis (), monitored in Baffin Bay on sea‐ice and planktonic communities. This complementary approach confirmed that unusual responses in α* and as a function of light history intensity are similar between sentinel sympagic species N. frigida and natural ice‐core communities. While no light‐history‐dependent trends were observed in planktonic communities, their α* and values were in the range of measurements from our monospecific cultures. Synthesis. Our results suggest that Arctic diatoms species photoadaptation strategy is tuned to the light environment of the habitats in which they dominate and indeed drives the seasonal taxonomic succession.

First Report of Anthracnose Disease on Bletilla striata Caused by Colletotrichum orchidophilum in Yunnan, China.

Bletilla striata (Thunb.) Reichb. f. has high ornamental and medicinal value. B. striata has been used in Chinese medicine for thousands of years to treat various diseases, such as peptic ulcers, gastrointestinal diseases, lung diseases, and traumatic bleeding (Jiang et al. 2021). In September 2020, about 30% of B. striata plants in a plantation in Lancang County (Puer City, Yunnan Province, 22°48'17" N, 99°46'58" E) were found with symptoms resembling Bletilla anthracnose disease. In May 2021, symptomatic leaves were observed again with a disease incidence rate reached 54.05%, and were collected. The initial symptoms were the appearance of one or more round light brown spots on the leaves. Subsequently, the lesions became larger, forming oval brown-black spots. On severely affected leaves, several spots coalesced, causing withering and death of the leaves. To isolate the pathogen, 10 symptomatic tissues (5mm2) of 10 infected leaves were disinfected in 75% ethanol for 30s then in 2% sodium hypochlorite for 3 minutes, rinsed with sterile water for 3 times, incubated on potato dextrose agar (PDA) plates at 25℃ for 5 to 7 days with a 12 h light/dark photoperiodic cycle. Finally, ten pathogen strains with similar morphology were isolated and pure cultures were obtained by single spore isolation. The morphology of fungal colonies was round, carpet-like, flat and neat, and the color was gray black. The conidiophores were colorless to brown and oval or stick-shaped. The conidia were cylindrical or oblong, consisted of a single cell with blunt round ends, and were on average 12.92 (8.13-21.21) μm×3.96 (2.55-5.90) μm (n=200) in size. Based on the morphology and conidial characteristics, the pathogen was identified as Colletotrichum sp. (Damm et al. 2012). The total genomic DNA of representative isolates (LCTJ-02, LCTJ-03, LCTJ-04, LCTJ-05 and LCTJ-06) was extracted and the ITS region, GAPDH, ACT and HIS3 gene regions were amplified and sequenced using the primer pairs ITS1/ITS4, GDF1/GDR1, 512F/783R, and CylH3F/CylH3R, respectively (Cai et al. 2009). The sequences were deposited in GenBank (MZ433189 to MZ433193 for ITS, MZ436430 to MZ436434 for GAPDH, MZ436435 to MZ436439 for HIS3 and MZ448474 to MZ448478 for ACT). BLAST search revealed that all sequences showed 98% to 100% homology with the corresponding sequences of C. orchidophilum ex-type (CBS 632.80). Phylogenetic trees were constructed using neighbor-joining and maximum likelihood methods for the combined data set of the ITS, GAPDH, ACT, and HIS3 genes by MEGA-X (Kumar et al.2018). In general, LCTJ-02, LCTJ-03, LCTJ-04, LCTJ-05, LCTJ-06, and C. orchidophilum type strains clustered on the same clade. To confirm pathogenicity, the five isolates of C. orchidophilum were inoculated in healthy leaves of potted B. striata, as described by Cai et al. (2009), with slight modifications. Each leaf was inoculated with three drops(10 µl drop-1) of conidia suspension (106 spores mL-1). The control group was mock inoculated with sterile water the same way. All samples were covered with plastic bags and maintained at 70% to 80% relative humidity for seven days. After this period, all inoculated leaves showed similar lesions, and the symptoms were identical to those observed in the field. The control plants remained healthy. The pathogens were re-isolated from two leaves of each treatment and re-identified as C. orchidophilum. To our knowledge, this is the first report of C. orchidophilum causing anthracnose on B. striata in China. In the future, the occurrence and transmission of this pathogen should be further studied in order to develop reasonable control measures.