scholarly journals Seasonal Fluctuations In Luteinizing Hormones (lh), Follicle Stimulating Hormones (FSH) And Testosterone Levels In Male African Giant Rats.

2020 ◽  
Vol 2 (2) ◽  
pp. 161-170
Author(s):  
O. S Olawuwo
Keyword(s):  
Dry Season ◽  
Wet Season ◽  
Luteinizing Hormones ◽  
Testosterone Levels ◽  
Sexual Activities ◽  
In Captivity ◽  
And Performance ◽  
Follicle Stimulating Hormones ◽  
Cricetomys Gambianus ◽  
The Tropics

As part of the several efforts to understand the biology of the African Giant rats (AGR) (Cricetomys gambianus), seasonal changes in the gonadotropin and testosterone levels of the adult male African giant rats of about 1 – 1½ years of age in captivity were investigated during wet and dry seasons in the tropics. Male giant rats (n = 10) were kept for 12 months and blood samples were collected monthly (on 15th of each month), during the dry (November – February) and wet (March – June) seasons for Luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone assays. The hormones’ levels were evaluated to suggest the best breeding season for giant rat in South-West Nigeria. The result showed that there were significant variation (p<0.001) in LH and FSH levels in the giant rat in the wet season when compared with the dry season. However, testosterone level was significantly lower (p<0.001) in the wet season than in the dry season. The study showed that sexual activities in the male AGR might be higher in the dry season with peak activities in December in the tropics while the gonadotropins prepare the animals for sexual activities in the dry season. Further studies on the seasonal activities of gonadotropins in the female will give more insight into the sexual receptivity and performance in these animals.

scholarly journals Yields of Organically Grown Sweet Pepper Cultivars and Lines during the Hot-wet and Cool-dry Season in the Tropics

2009 ◽  
Vol 19 (2) ◽  
pp. 418-422 ◽  
Author(s):  
Peter Juroszek ◽  
Hsing-Hua Tsai
Keyword(s):  
Organic Farming ◽  
Farming Systems ◽  
Sweet Pepper ◽  
Dry Season ◽  
Viable Alternative ◽  
Conventional Farming ◽  
Wet Season ◽  
Commercial Cultivars ◽  
The Tropics ◽  
Cool Dry Season

Organic production is considered by many researchers to be a viable alternative to conventional farming systems. Equivalent yields already have been demonstrated in several studies. The major objective of our study was to collect data on total and marketable fruit yields of sweet pepper (Capsicum annuum) under organic farming conditions in the tropics. Experiments were conducted during the hot-wet season from 7 Mar. 2007 to 30 July 2007 and during the cool-dry season from 27 Nov. 2007 to 7 Apr. 2008. The six experimental entries included four commercial F1 hybrids and two genotypes bred at AVRDC–The World Vegetable Center (Shanhua, Taiwan). During the hot-wet season, high total (44.6–55.7 t·ha−1) and marketable yields (36.9–45.6 t·ha−1) were achieved under organic farming conditions in the open field similar to yields of conventionally produced sweet pepper in previous field experiments at AVRDC. The total yield of the commercial cultivars Queen Star and Hercules exceeded 50 t·ha−1; however, this was not significantly different compared with the other trial entries. During the cool-dry season, the total (25.4–45.7 t·ha−1) and marketable yields (21.1–37.8 t·ha−1) of all trial entries were reduced, probably because the relatively late planting date in November and relatively low air temperature resulted in reduced fruit set. The commercial cultivars Andalus and Green Bell Improved realized in both seasons a total fruit yield of more than 40.0 t·ha−1, suggesting that these can be grown successfully in hot-wet and cool-dry seasons. The relatively high yields of sweet pepper achieved on-station under tropical climatic conditions may encourage farmers and agricultural stakeholders to consider organic farming approaches as a viable alternative to conventional farming systems.

Reproduction in the northern brown bandicoot (Isoodon macrourus) in the Australian Wet Tropics

2009 ◽  
Vol 57 (2) ◽  
pp. 105 ◽  
Author(s):  
Karl Vernes ◽  
Lisa Claire Pope
Keyword(s):  
Environmental Factors ◽  
Wild Population ◽  
Dry Season ◽  
Adult Males ◽  
Wet Season ◽  
Timing Of Reproduction ◽  
Adult Females ◽  
Wet Tropics ◽  
Almost All ◽  
The Tropics

We investigated timing of reproduction in a wild population of northern brown bandicoots (Isoodon macrourus) in the Australian Wet Tropics. Almost all births occurred during the late dry season and early wet season, and most adult females (78–96%) were carrying pouch young during those times. Litter sizes ranged from 1 to 6 pouch young (mean = 3.1) and was not influenced by season. Adult males had significantly larger testes in the late dry and early wet seasons, corresponding with the peak in births. Daylength was the only environmental factor that predicted the presence of a litter; when daylength exceeded 12 h, more than 70% of captured females were carrying pouch young, and most (94%) births were estimated to have occurred on days with >12 h of daylight. Various environmental factors have been proposed as a cue for breeding in I. macrourus, with daylength though to be the primary cue initiating breeding in temperate Australia, but temperature and rainfall thought to be more important in the tropics. Our data suggest that in the Australian Wet Tropics, increasing daylength in the late dry season acts as the primary cue for breeding.

Seasonal variation of carbon assimilation in mango (cv. Kensington Pride): effect of flowering treatments

2003 ◽  
Vol 54 (3) ◽  
pp. 309 ◽  
Author(s):  
Alonso González ◽  
S. J. Blaikie
Keyword(s):  
Gas Exchange ◽  
Chlorophyll Content ◽  
Leaf Gas Exchange ◽  
Average Rate ◽  
Carbon Assimilation ◽  
Vapour Pressure Deficit ◽  
Dry Season ◽  
Fruit Yield ◽  
Wet Season ◽  
The Tropics

In the tropics of northern Australia the mango cultivar Kensington Pride exhibits erratic flowering and fruiting and low productivity. Two treatments to manipulate flowering were applied. The first, mango flowering treatment (MFT), involved cutting a cincture through the bark around the circumference of the tree trunk and tying into the cincture a length of twine soaked in a solution of morphactin, CF125. The second involved applying paclobutrazol (PBZ) as a soil drench around the trunk of the tree. Phenology, leaf gas exchange, and fruit yield were assessed over 2 seasons in 3 separate groups of trees in commercial orchards near Darwin.Both MFT and PBZ supported earlier and/or more intense flowering in the season of application than did control trees. The PBZ was re-applied annually and the beneficial effect on flowering occurred in successive years. The MFT was applied once only at the start of the experiment and the effect of MFT was not evident in the second season.The effect of MFT on gas exchange was characterised by a severe reduction in net carbon assimilation (Amax), stomatal conductance (gs), and transpiration (E) for up to 4 months following treatment. Trees receiving PBZ generally had higher rates of leaf gas exchange than MFT trees but similar to control trees. During the dry season, leaves of MFT, control, and PBZ trees had similar rates of Amax. In the year of application, chlorophyll content of MFT trees was lower than that of the other treatments, but in the second year it was very similar to control trees. PBZ trees had the highest chlorophyll content during the study. Commercial fruit yield of PBZ-treated trees was 2–3 times higher than that of control or MFT trees. Independent of the flowering treatments, Amax followed a seasonal trend with an average rate of 9.05 μmol/m2.s (min. 4.42, max. 13.2) during the wet season (January–April), and 4.2 μmol/m2.s (min. 1.11, max. 8.7) during the dry season (May–October). Regression analysis demonstrated that 82% of the variation in gs and 76% of the variation in Amax could be explained by the effect of vapour pressure deficit of the leaf (VPDL) in field-grown mango trees.

scholarly journals Effects of genotype and season on the productive performance of commercial egg-type chickens in the derived savanna zone in Nigeria

2021 ◽  
Vol 39 (2) ◽  
pp. 4-13
Author(s):  
A. O. Oguntunji ◽  
A. E. Salako
Keyword(s):  
Rainy Season ◽  
Egg Production ◽  
Genetic Basis ◽  
Dry Season ◽  
Productive Performance ◽  
Performance Indices ◽  
Wet Season ◽  
Derived Savanna ◽  
And Performance ◽  
Season Interaction

Twelve (12) month production records of two commercial egg-type chickens, Nera Black (NB) and Isa Brown (IB) reared on a commercial farm in Ilora, Oyo State, Nigeria were analysed to assess effects of season and genotype on their performance. The production record was sorted according to the two recognized major seasons: wet (April-September) and dry (October-March) in the study area. Besides, the each major season was further partitioned into two sub-seasons namely: early rainy season (ERS: April-June), late rainy season (LRS: July-September), early dry season (EDS: October-December) and late dry season (LDS: January-March). Results of data analysis showed that genotype had no significant effect (P>0.05) on all the performance indices. Conversely, season significantly (P<0.05) affected all the performance parameters evaluated and hens performed better in wet seasons compared with dry months. There was significant (P<0.05) genotype by season interaction effect on egg production but not (P>0.05) for other productive parameters. IB strain performed better in wet season most especially in LRS while NB hens had better performance in dry season. Results from this study indicated that regardless of the season, the two egg strains should be employed for commercial egg production but adequate measure should be taken to combat the adverse effect of thermal stress on the welfare and performance of layers in the study area most especially in LDS months. Discrepancies in genotype by season interaction suggest genetic basis to differences in performances and physiological abilities of the investigated egg-strains to cope with stresses emanating from change in season.

scholarly journals Assessing evapotranspiration drivers and patterns at multiple scale in the Amazon basin

2020 ◽  
Author(s):  
Adriana Aparecida Moreira ◽  
Anderson Luis Ruhoff
Keyword(s):  
Remote Sensing ◽  
Tropical Forest ◽  
Amazon Basin ◽  
Vegetation Index ◽  
Dry Season ◽  
Limiting Factors ◽  
Net Radiation ◽  
Wet Season ◽  
Basin Scale ◽  
The Tropics

&lt;p&gt;Evapotranspiration (ET) is a key variable to terrestrial climate system, transferring water from the surface to the atmosphere, regulating air temperature and carbon exchanges, thus, linking the water, carbon and water cycles. Despite its great importance, ET patterns in tropical biomes are not fully understood yet. Studies with eddy covariance (EC) ET measurements and remote sensing models demonstrated a huge importance over ET drivers and limiting factors. In this context, this study aimed to assess the ET process in the tropics, from local to basin scale, using EC measurements (from the LBA project) and remote sensing models (MOD16 and GLEAM). At local scale, measurements and estimates were evaluated against net radiation, precipitation and vegetation index (EVI), in order to assess how these drivers control ET patterns. Then, a Budyko approach was applied at basin scale to calculate how water and energy constrain ET in large basins, including Amazon, Solim&amp;#245;es, Purus, Medeira, Tapaj&amp;#243;s, and Xingu rivers. Our results demonstrated disagreements between models to represent maximum and minimum ET rates at tropical forest vegetation (at K43, K67 and K83 sites), with ET measurements peaking during the dry season, in a pattern coincident with annual net radiation cycle. Moreover, deep rooting of well-established rainforests, available soil moisture and increased solar radiation allow ET processes to be maintained during the dry season. ET estimates from MOD16 algorithm agree with these patterns, however, estimates from GLEAM indicates maximum ET rates during the rainy season. At cropland/pasture vegetation (at K77 site), also located in central Amazon, EC measurements showed moderate negative agreement with net radiation (R&amp;#178; = -0.48) and positive with precipitation (R&amp;#178; = 0.53), with decreasing ET rates during the dry season. GLEAM showed ET rates reduction in dry months, but also showed a peak in during wet season, while increasing ET estimates are observed for MOD16, both presented similar behavior as in tropical forest sites. Furthermore, measurements in the southwest part (RJA and FNS sites) did not show clear seasonal patterns, and both MOD16 and GLEAM algorithms, agree with decreasing ET rates during the dry season, showing a significant relationship with precipitation and vegetation indices. Results based on the Budyko approach indicated agreement between the models, indicating a predominant energy-limited condition when evaluated whole basin (at &amp;#211;bidos station), or basins located in the northern and western parts of Amazon (in Amazon, Purus, and Negro basins), which corroborates with other studies, where ET has limited energy availability. However, our results also demonstrated disagreements in basins located in the southern and eastern parts (in Madeira, Tapaj&amp;#243;s and Xingu basins), where MOD16 showed some water-limited conditions, whilst it was not observed for GLEAM algorithm. Whether the models agree in terms of seasonality and water and energy limitations, they also disagree between them and ground measurements. This study highlighted the importance to understand limitations of multi-models and multi-scale ET processes for hydroclimatological studies in the tropics.&lt;/p&gt;

scholarly journals Hot temperatures during the dry season reduce survival of a resident tropical bird

2018 ◽  
Vol 285 (1878) ◽  
pp. 20180176 ◽  
Author(s):  
Bradley K. Woodworth ◽  
D. Ryan Norris ◽  
Brendan A. Graham ◽  
Zachary A. Kahn ◽  
Daniel J. Mennill
Keyword(s):  
Southern Oscillation ◽  
Dry Season ◽  
Vital Rates ◽  
Wet Season ◽  
Functional Understanding ◽  
Female Survival ◽  
Tropical Bird ◽  
Hot Environments ◽  
Distributional Shifts ◽  
The Tropics

Understanding how climate change will shape species distributions in the future requires a functional understanding of the demographic responses of animals to their environment. For birds, most of our knowledge of how climate influences population vital rates stems from research in temperate environments, even though most of Earth's avian diversity is concentrated in the tropics. We evaluated effects of Southern Oscillation Index (SOI) and local temperature and rainfall at multiple temporal scales on sex-specific survival of a resident tropical bird, the rufous-and-white wren Thryophilus rufalbus , studied over 15 years in the dry forests of northwestern Costa Rica. We found that annual apparent survival of males was 8% higher than females, more variable over time, and responded more strongly to environmental variation than female survival, which did not vary strongly with SOI or local weather. For males, mean and maximum local temperatures were better predictors of survival than either rainfall or SOI, with high temperatures during the dry season and early wet season negatively influencing survival. These results suggest that, even for species adapted to hot environments, further temperature increases may threaten the persistence of local populations in the absence of distributional shifts.

scholarly journals Spermatogenesis and plasma testosterone levels under field conditions, in males of the common toad (Rhinella arenarum Hensel, 1867), from the Monte Desert, Argentina

2018 ◽  
Vol 148 (1) ◽  
Author(s):  
Lorena Quiroga ◽  
Eduardo Sanabria ◽  
Graciela Jahn ◽  
Miguel Fornés
Keyword(s):  
Fat Body ◽  
Dry Season ◽  
Field Conditions ◽  
Plasma Testosterone ◽  
Wet Season ◽  
Monte Desert ◽  
Testosterone Levels ◽  
Dry Seasons ◽  
Rhinella Arenarum ◽  
Wet And Dry Seasons

The reproductive function in anurans depends on interactions between the hypothalamus, adenohypophysis and gonads, which are mediated by an endocrine circuit. We studied the relationship between reproductive and histological parameters, variation in spermatogenic activity, and plasma testosterone concentration cycle for a population of Rhinella arenarum under field conditions in the Monte Desert of Argentina. We captured 28 adult male R. arenarum from December 2009 to November 2010, and define two seasons (wet and dry seasons). We performed histological analyses of the testes and used radioimmunoassay to determine plasma testosterone concentrations. Our results showed no difference in testicular volume between the wet and dry seasons, but found that changes in the fat body mass were higher in the dry season. The spematogenic cycle was characterized by the prominent presence of spermatogonia at the end of the dry season and the wet season. We also observed a higher percentage of primary spermatocytes in the wet season. In addition, we found that R. arenarum showed a continuous spermatogenic cycle, and spermatogenesis produced a high percentage of sperm bundles in the dry season, concordant with high levels of testosterone. Testosterone levels were highest during the dry season (33.89 ± 7.85 ng/ml). Our data indicate that plasma testosterone showed a “dissociation” from reproductive activity such that the two parameters are asynchronous during the reproductive season. The characteristics of the reproductive cycle of R. arenarum allow this species the plasticity to colonize different environments, from tropical regions to deserts.

scholarly journals Regional N<sub>2</sub>O fluxes in Amazonia derived from aircraft vertical profiles

2009 ◽  
Vol 9 (4) ◽  
pp. 17429-17463 ◽  
Author(s):  
M. T. S. D'Amelio ◽  
L. V. Gatti ◽  
J. B. Miller ◽  
P. Tans
Keyword(s):  
Biomass Burning ◽  
Regional Scale ◽  
Dry Season ◽  
N2o Emissions ◽  
Amazon Forest ◽  
Vertical Profiles ◽  
Wet Season ◽  
N2o Flux ◽  
New Approach ◽  
The Tropics

Abstract. Nitrous oxide (N2O) is the third most important anthropogenic greenhouse gas. Globally, the main sources of N2O are nitrification and denitrification in soils. About two thirds of the soil emissions occur in the tropics and approximately 20% originate in wet rainforest ecosystems, like the Amazon forest. The work presented here involves aircraft vertical profiles of N2O from the surface to 4 km over two sites in the Eastern and Central Amazon: Tapajós National Forest (SAN) and Cuieiras Biologic Reserve (MAN), and the estimation of N2O fluxes for regions upwind of these sites. To our knowledge, these regional scale N2O measurements in Amazonia are unique and represent a new approach to looking regional scale emissions. The fluxes upwind of MAN exhibited little seasonality, and the annual mean was 2.1±1.0 mg N2O m−2 day−1, higher than that for fluxes upwind of SAN, which averaged 1.5±1.6 mg N2O m−2 day−1. The higher rainfall around the MAN site could explain the higher N2O emissions. For fluxes from the coast to SAN seasonality is present for all years, with high fluxes in the months of March through May, and in November through December. The first peak of N2O flux is strongly associated with the wet season. The second peak of high N2O flux recorded at SAN occurs during the dry season and can not be easily explained. However, about half of the dry season profiles exhibit significant correlations with CO, indicating a larger than expected source of N2O from biomass burning. The average CO:N2O ratio for all profiles sampled during the dry season is 94±77 mol CO:mol N2O and suggests a larger biomass burning contribution to the global N2O budget than previously reported.

scholarly journals Regional N<sub>2</sub>O fluxes in Amazonia derived from aircraft vertical profiles

2009 ◽  
Vol 9 (22) ◽  
pp. 8785-8797 ◽  
Author(s):  
M. T. S. D'Amelio ◽  
L. V. Gatti ◽  
J. B. Miller ◽  
P. Tans
Keyword(s):  
Biomass Burning ◽  
Regional Scale ◽  
Dry Season ◽  
N2o Emissions ◽  
Amazon Forest ◽  
Vertical Profiles ◽  
Wet Season ◽  
N2o Flux ◽  
Nitrification And Denitrification ◽  
The Tropics

Abstract. Nitrous oxide (N2O) is the third most important anthropogenic greenhouse gas. Globally, the main sources of N2O are nitrification and denitrification in soils. About two thirds of the soil emissions occur in the tropics and approximately 20% originate in wet rainforest ecosystems, like the Amazon forest. The work presented here involves aircraft vertical profiles of N2O from the surface to 4 km over two sites in the Eastern and Central Amazon: Tapajós National Forest (SAN) and Cuieiras Biologic Reserve (MAN), and the estimation of N2O fluxes for regions upwind of these sites. To our knowledge, these regional scale N2O measurements in Amazonia are unique and represent a new approach to looking regional scale emissions. The fluxes upwind of MAN exhibited little seasonality, and the annual mean was 2.1±1.0 mg N2O m−2 day−1, higher than that for fluxes upwind of SAN, which averaged 1.5±1.6 mg N2O m−2 day−1. The higher rainfall around the MAN site could explain the higher N2O emissions, as a result of increased soil moisture accelerating microbial nitrification and denitrification processes. For fluxes from the coast to SAN seasonality is present for all years, with high fluxes in the months of March through May, and in November through December. The first peak of N2O flux is strongly associated with the wet season. The second peak of high N2O flux recorded at SAN occurs during the dry season and can not be easily explained. However, about half of the dry season profiles exhibit significant correlations with CO, indicating a larger than expected source of N2O from biomass burning. The average CO:N2O ratio for all profiles sampled during the dry season is 94±77 mol CO:mol N2O and suggests a larger biomass burning contribution to the global N2O budget than previously reported.

Weed Control for Growing Sorghum in Puerto Rico

1969 ◽  
Vol 53 (3) ◽  
pp. 199-206
Author(s):  
F. R. Miller ◽  
H. J. Cruzado ◽  
R. W. Bovey ◽  
C. C. Dowler
Keyword(s):  
Puerto Rico ◽  
Weed Control ◽  
Avena Sativa ◽  
Dry Season ◽  
Weed Species ◽  
Wet Season ◽  
Supplemental Irrigation ◽  
Economical Method ◽  
The Tropics ◽  
Sorghum Bicolor L

Herbicides 2-chloro-4,6-bis(isopropylamino)-s-triazine (Propazine), 2- chloro-4-ethylamme-6-isopropylamino-s-triazine (Atrazine) and 3-(3-4-dichlorophenyl)- l, 1-dimethylurea (Diuron) were evaluated on sorghum (Sorghum bicolor (L.) Moench.) var. SA 406 at the Federal Experiment Station, Mayagüez, Puerto Rico. Applied as a pre-emergence spray, both Propazine and Atrazine at 3 lb./A. controlled broadleaf weeds and grasses, and were more effective than Diuron for control of broadleaf weeds in the initial test. Propazine was less injurious to sorghum than Atrazine. Effectiveness of Propazine was greater during the dry season (with supplemental irrigation) than during the wet season. Hand-weeded sorghum yielded significantly more fodder than plots treated with Propazine at 1 and 3 lb./A. during the wet season, but not during the dry season. Oats (Avena sativa (L.)) grew without apparent injury from herbicide residues when planted in plots 6 months after treatment with Propazine at rates of 1 and 3 lb./A. Propazine used at 2 to 3 lb./A. appears to be a safe and economical method of weed control in sorghum for the Tropics where soil type, rainfall, weed species, etc., are similar to those described herein.

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