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Reproductive Stages (reproductive + stage)
Kinds of Reproductive Stages Selected AbstractsOntogenetic switches from plant resistance to tolerance: minimizing costs with age?ECOLOGY LETTERS, Issue 3 2007Karina Boege Abstract Changes in herbivory and resource availability during a plant's development should promote ontogenetic shifts in resistance and tolerance, if the costs and benefits of these basic strategies also change as plants develop. We proposed and tested a general model to detect the expression of ontogenetic tradeoffs for these two alternative anti-herbivory strategies in Raphanus sativus. We found that ontogenetic trajectories occur in both resistance and tolerance but in opposite directions. The juvenile stage was more resistant but less tolerant than the reproductive stage. The ontogenetic switch from resistance to tolerance was consistent with the greater vulnerability of young plants to leaf damage and with the costs of resistance and tolerance found at each stage. We posit that the ontogenetic perspective presented here will be helpful in resolving the current debate on the existence and detection of a general resistance,tolerance tradeoff. [source] Antioxidative Enzymes and Sucrose Synthase Contribute to Cold Stress Tolerance in ChickpeaJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 5 2009S. Kaur Abstract Chickpea is sensitive to low temperature (<10°C) during its reproductive stage. Low temperature adversely affects the development of pods and seeds. This study was undertaken to investigate the role of sucrose metabolizing enzymes in seed development and potential of antioxidative enzymes in protecting seeds and podwalls from the deleterious effects of cold stress in advanced cold tolerant chickpea breeding lines. Healthy pod set was observed in these tolerant lines in the end of December where as low temperature susceptible PBG-1 did not flower. Two lines ICCV 96029 and ICCV 96030 showed susceptible characters such as reduced flowering, blackened and shrivelled seeds and yellowish pods in comparison to other cold stress tolerant lines due to sudden dip of temperature (<1 °C) during the first week of January. These two lines were, therefore, treated as susceptible checks in comparison to other tolerant lines. A significantly higher activity and specific activity of sucrose synthase was observed in seeds of most of the cold tolerant lines in comparison with ICCV 96029 and ICCV 96030, thereby providing sugars as well as sugar nucleotides for their growth and starch synthesis during unfavourable low temperature. The developing seeds and podwalls of tolerant genotypes had higher activities of antioxidant enzymes, i.e. catalase, ascorbate peroxidase and glutahione reductase in comparison with ICCV 96029 and ICCV 96030. It appears that the higher activities of antioxidant enzymes in podwall protect the developing seeds from cold stress. [source] Breeding in high-elevation habitat results in shift to slower life-history strategy within a single speciesJOURNAL OF ANIMAL ECOLOGY, Issue 2 2009H. Bears Summary 1Elevational gradients create environmental variation that is hypothesized to promote variation in life-history strategies. We tested whether differences in life-history strategies were associated with elevation in a songbird, the dark-eyed junco (Junco hyemalis; Aves; A.O.U. 1998). 2We monitored birds in four replicated sites per elevation, at 2000 m a.s.l. (high elevation) and 1000 m a.s.l. (low elevation), in the Rocky Mountains of Canada. 3Over 5 years, we measured the following traits and vital rates: egg-laying schedules, morphological indicators of reproductive stage, seasonal reproductive success, indicators of competitive class (age, size, arrival time), and survival rates. 4We found two main patterns: with an increase in breeding elevation, dark-eyed juncos delayed the development of structures necessary for reproduction (e.g. cloacal protuberance in males) and reduced the duration of their reproductive period to less than half of the time used by low-elevation birds; and 5Juncos at high-elevation sites had 55,61% lower annual reproductive success and 15 to 20% higher survival rates. While adult juncos at high elevations produced fewer offspring, those offspring were in better condition. Proportions of age and size classes in high- compared to low-elevation populations were similar, suggesting that a life-history trade-off is present, rather than competition forcing inferior competitors to breed in a peripheral habitat. The apparent trade-off between reproduction and survival corresponded to a shorter period of favourable weather and available food in high- compared to low-elevation habitats. 6Thus, elevation had a strong influence on life-history characteristics of a single species over a short spatial distance, suggesting a shift in life history from a high reproductive strategy at lower elevations to a high survivor strategy at high elevations. 7This is the first paper to show a shift in avian life-history strategies along an elevational gradient (in both genders, of multiple age classes) when region (latitude) and phylogenetic histories are controlled for. [source] Estimation of gonad volume, fecundity, and reproductive stage of shovelnose sturgeon using sonography and endoscopy with application to the endangered pallid sturgeonJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2007By J. L. Bryan Summary Most species of sturgeon are declining in the Mississippi River Basin of North America including pallid (Scaphirhynchus albus F. and R.) and shovelnose sturgeons (S. platorynchus R.). Understanding the reproductive cycle of sturgeon in the Mississippi River Basin is important in evaluating the status and viability of sturgeon populations. We used non-invasive, non-lethal methods for examining internal reproductive organs of shovelnose and pallid sturgeon. We used an ultrasound to measure egg diameter, fecundity, and gonad volume; endoscope was used to visually examine the gonad. We found the ultrasound to accurately measure the gonad volume, but it underestimated egg diameter by 52%. After correcting for the measurement error, the ultrasound accurately measured the gonad volume but it was higher than the true gonad volume for stages I and II. The ultrasound underestimated the fecundity of shovelnose sturgeon by 5%. The ultrasound fecundity was lower than the true fecundity for stage III and during August. Using the endoscope, we viewed seven different egg color categories. Using a model selection procedure, the presence of four egg categories correctly predicted the reproductive stage ± one reproductive stage of shovelnose sturgeon 95% of the time. For pallid sturgeon, the ultrasound overestimated the density of eggs by 49% and the endoscope was able to view eggs in 50% of the pallid sturgeon. Individually, the ultrasound and endoscope can be used to assess certain reproductive characteristics in sturgeon. The use of both methods at the same time can be complementary depending on the parameter measured. These methods can be used to track gonad characteristics, including measuring Gonadosomatic Index in individuals and/or populations through time, which can be very useful when associating gonad characteristics with environmental spawning triggers or with repeated examinations of individual fish throughout the reproductive cycle. [source] Effects of thiol compounds on in vitro maturation of canine oocytes collected from different reproductive stagesMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 9 2007Mohammad Shamim Hossein Abstract Various thiol compounds are known to improve cytoplasmic and/or nuclear maturation of oocytes in vitro. The present study examined the effects of two thiol compounds, cysteine (0.1, 0.5, and 1.0 mM) and cysteamine (50, 100, and 200 µM), on cytoplasmic and nuclear maturation of canine oocytes. Oocytes collected from different reproductive stages were cultured in TCM-199 supplemented with 10% fetal bovine serum, 2.2 mg/ml sodium carbonate, 2.0 µg/ml estrogen, 0.5 µg/ml FSH, 0.03 IU/ml hCG, and 1% penicillin,streptomycin solution for 72 h. Data were analyzed by two-way ANOVA after arcscine transformation and protected by Bonferroni post hoc test. The effects of cysteine and cysteamine on canine IVM were varied depending on the reproductive stage of oocyte donor bitches. In the follicular stage, significantly more oocytes reached the metaphase II (M II) stage when cultured with 0.5 or 1.0 mM cysteine (16.7% and 16.9%, respectively) compared to the control (6.2%). In the follicular stage, cysteamine increased oocyte maturation rate upto the M II stage (15.1% to 17.0%) compared to the control (4.4%). Both the 0.5 mM cysteine and 100 µM cysteamine, alone or together, increased the intracellular GSH level of canine oocytes compared to the control. Irrespective of reproductive stage, no further beneficial effects on nuclear or cytoplasmic maturation were observed when 0.5 mM cysteine and 100 µM cysteamine were supplemented together. In conclusion, addition of 0.5 mM cysteine and 100 µM cysteamine to the maturation medium improved IVM of canine oocytes. Mol. Reprod. Dev. 74: 1213,1220, 2007. © 2007 Wiley-Liss, Inc. [source] Phenology of the environmental weed Achillea millefolium (Asteraceae) along altitudinal and disturbance gradients in the Snowy Mountains, AustraliaNORDIC JOURNAL OF BOTANY, Issue 2 2004Frances Mary Johnston This study examined the phenology of the weed Achillea millefolium over a growing season in the Snowy Mountains. Vegetative and reproductive characteristics of plants in 1 m2 quadrats were compared among sites at four different altitudes (medium and high montane, low and high subalpine) and three types of infrastructure (primary road, secondary road and building, total 12 sites). Altitude, infrastructure and time of year did not affect percentage cover of vegetation. Flowering started earlier and lasted longer in the low montane sites compared to high subalpine sites. The type of infrastructure only affected the number of reproductive structures at the peak of flowering, with A. millefolium growing next to buildings having two to three times more inflorescences per m2 than along primary and secondary road verges. At the peak for each reproductive stage, there was an average of 1.47 developing inflorescences, 21 inflorescences in bud, 24 inflorescences in flower, 4 inflorescences setting seed, and 3 releasing seed. Based on the maximum number of inflorescences present at any time at each site, there was an average of 36 inflorescences, giving an estimate potential seed production of 51 400 seed per one m2 for A. millefolium in the Snowy Mountains. If the climate changes in the Snowy Mountains as predicted, then it is likely that yarrow will produce more inflorescences and seed in the higher altitude sites. [source] Predicting invertebrate diversity from disturbance regimes in forest streamsOIKOS, Issue 1 2002Russell G. Death The link between substrate disturbance and stream invertebrate species richness is often complicated by the fact that substrate disturbance removes both invertebrates and periphyton (a potential food source). It is never clear whether disturbance acts directly on species diversity by removing animals or indirectly by reducing one of their food sources. To examine this relationship invertebrate diversity patterns were examined in 25 forest streams in Urewera National Park, New Zealand, where light attenuation from the forest canopy was postulated to limit periphyton biomass and remove the confounding influence of periphyton on the link between substrate disturbance and invertebrate diversity. Invertebrate species richness declined linearly with increasing substrate disturbance. Although periphyton biomass was comparatively low, species richness was more strongly related to periphyton biomass than to any disturbance measure. The highly mobile nature and terrestrial reproductive stage of many lotic invertebrates suggest that colonisation dynamics may have a more important influence on diversity patterns than monopolisation of resources for population growth. Although both the intermediate disturbance hypothesis and the dynamic equilibrium model encompass colonisation as a critical determinant of diversity both models also require a trade-off between the colonising and competitive ability of individual species; a phenomenon which does not appear to occur widely in lotic communities. Rather, it is postulated that resource levels will set an upper limit to the species richness of a benthic community that can be achieved through colonisation of taxa in the absence of disturbance, while disturbance removes taxa and resets the colonisation process. [source] Activity budgets and activity rhythms in red ruffed lemurs (Varecia rubra) on the Masoala Peninsula, Madagascar: seasonality and reproductive energeticsAMERICAN JOURNAL OF PRIMATOLOGY, Issue 1 2005Natalie Vasey Abstract The activity budgets and daily activity rhythms of Varecia rubra were examined over an annual cycle according to season and reproductive stage. Given the relatively high reproductive costs and patchy food resources of this species, I predicted that V. rubra would 1) travel less and feed more during seasonal resource scarcity in an attempt to maintain energy balance, and 2) show sex differences in activity budgets due to differing reproductive investment. Contrary to the first prediction, V. rubra does not increase feeding time during seasonal food scarcity; rather, females feed for a consistent amount of time in every season, whereas males feed most during the resource-rich, hot dry season. The results are consistent with other predictions: V. rubra travels less in the resource-scarce cold rainy season, and there are some pronounced sex differences, with females feeding more and resting less than males in every season and in every reproductive stage except gestation. However, there are also some provocative similarities between the sexes when activity budgets are examined by reproductive stage. During gestation, female and male activity budgets do not differ and appear geared toward energy accumulation: both sexes feed and rest extensively and travel least during this stage. During lactation, activity budgets are geared toward high energy expenditure: both sexes travel most and in equal measure, and rest least, although it remains the case that females feed more and rest less than males. These similarities between female and male activity budgets appear related to cooperative infant care. The high energetic costs of reproduction in V. rubra females may require that they allot more time to feeding year round, and that their overall activity budget be more directly responsive to seasonal climate change, seasonal food distribution, and reproductive schedules. Am. J. Primatol. 66:23,44, 2005. [source] Reproduction, growth and stress response in adult red sea bream, Pagrus major (Temminck & Schlegel) exposed to different photoperiods at spawning seasonAQUACULTURE RESEARCH, Issue 4 2010Amal Biswas Abstract Adult red sea bream, Pagrus major (body weight, 1.0,2.0 kg) was exposed to three photoperiods [12 h light:12 h dark (12L:12D), 16 h light:8 h dark (16L:8D) and 24 h light:0 h dark (24L:0D)] from 2 months before spawning till the end of the spawning season to investigate growth, spawning and stress response. During the spawning season, tanks were checked every morning for spawned eggs. The growth performance in fish under 24L:0D was stimulated with significantly higher feed intake than those under other photoperiods (P<0.05). The number of eggs and gonadal histology confirmed that three and five females out of six in each of duplicate tanks of the 16L:8D treatment spawned. In contrast, only two out of six females in one tank of the 24L:0D treatment spawned, and no spawns were observed in the 12L:12D treatment. At the end of the spawning period, both 17,-estradiol and testosterone levels were significantly higher in fish exposed to 16L:8D followed by 12L:12D and 24L:0D photoperiods (P<0.05). Photoperiod manipulation did not cause significant stress response in fish (P>0.05). The results suggest that stimulating the growth performance of red sea bream at reproductive stage with a 24L:0D photoperiod is possible if the fish are subjected to this photoperiod long before the onset of the spawning season. [source] Applying Network Analysis to the Conservation of Habitat Trees in Urban Environments: a Case Study from Brisbane, AustraliaCONSERVATION BIOLOGY, Issue 3 2006MONIKA RHODES conectividad de perchas; fauna que utiliza oquedades; planificación de la conservación; red sin escala; Tadarida australis Abstract:,In Australia more than 300 vertebrates, including 43 insectivorous bat species, depend on hollows in habitat trees for shelter, with many species using a network of multiple trees as roosts. We used roost-switching data on white-striped freetail bats (Tadarida australis; Microchiroptera: Molossidae) to construct a network representation of day roosts in suburban Brisbane, Australia. Bats were caught from a communal roost tree with a roosting group of several hundred individuals and released with transmitters. Each roost used by the bats represented a node in the network, and the movements of bats between roosts formed the links between nodes. Despite differences in gender and reproductive stages, the bats exhibited the same behavior throughout three radiotelemetry periods and over 500 bat days of radio tracking: each roosted in separate roosts, switched roosts very infrequently, and associated with other bats only at the communal roost. This network resembled a scale-free network in which the distribution of the number of links from each roost followed a power law. Despite being spread over a large geographic area (>200 km2), each roost was connected to others by less than three links. One roost (the hub or communal roost) defined the architecture of the network because it had the most links. That the network showed scale-free properties has profound implications for the management of the habitat trees of this roosting group. Scale-free networks provide high tolerance against stochastic events such as random roost removals but are susceptible to the selective removal of hub nodes. Network analysis is a useful tool for understanding the structural organization of habitat tree usage and allows the informed judgment of the relative importance of individual trees and hence the derivation of appropriate management decisions. Conservation planners and managers should emphasize the differential importance of habitat trees and think of them as being analogous to vital service centers in human societies. Resumen:,En Australia, más de 300 vertebrados, incluyendo 43 especies de murciélagos insectívoros, dependen de oquedades en árboles para refugiarse; muchas de ellas perchan en una red de múltiples árboles. Utilizamos datos de cambio de perchas en Tadarida australis (Microchiroptera: Molossidae) para construir una representación reticular de las perchas diurnas en los suburbios de Brisbane, Australia. Los murciélagos fueron capturados en un árbol con un grupo de varios cientos de individuos y liberados con transmisores. Cada percha utilizada por los murciélagos representó un nodo individual en la red, y los movimientos de murciélagos entre perchas constituyeron los eslabones entre los nodos. A pesar de las diferencias de género y etapas reproductivas, los murciélagos mostraron el mismo comportamiento en tres períodos de radiotelemetría y en más de 500 días de seguimiento de murciélagos: cada uno utilizó perchas separadas, cambiaban de percha poco frecuentemente, y se asociaron con otros murciélagos sólo en las perchas comunales. Esta red fue semejante a una red sin escala en la que la distribución del número de eslabones de cada percha cumplió una ley potencial. A pesar de estar dispersas en un área geográfica extensa (>200 km2), cada percha estaba conectada con otras por menos de tres eslabones. Una percha (el centro o percha comunal) definió la arquitectura de la red porque tenía a la mayoría de los eslabones. El hecho de que la red mostrara propiedades libres de escala tiene implicaciones profundas para la gestión de árboles que funcionan como perchas. Las redes libres de escala proporcionan alta tolerancia a eventos estocásticos como la remoción aleatoria de perchas, pero son susceptibles a la remoción selectiva de nodos centrales. El análisis de redes es una herramienta útil para el entendimiento de la organización estructural del uso de de árboles y permite el juicio informado de la importancia relativa de árboles individuales y por lo tanto la derivación de decisiones administrativas apropiadas Los planificadores y gestores de la conservación deberían enfatizar la importancia diferencial de árboles y considerarlos análogos a los centros de servicio vitales en las sociedades humanas. [source] Histology, histochemistry and morphometry of the ovary of the adult plains viscacha (Lagostomus maximus) in different reproductive stagesACTA ZOOLOGICA, Issue 4 2009Mirta Alicia Flamini Abstract Lagostomus maximus is a South American Hystricognathi rodent whose reproductive behaviour shows characteristics unusual for mammals, such as polyovulation (200,800 oocytes) and a high rate of embryo mortality. Thirty-six mature females captured in the province of Buenos Aires showed different physiological reproductive stages. Most of them presented a postpartum oestrus in August,September. This characteristic is different from that reported in other geographical areas. The stages considered were: anoestrus, follicular phase, early pregnancy and late pregnancy. The ovaries were light-pink and smooth and presented a tortuous cord-like aspect. Many primordial follicles were found in all the females studied. Follicles in different states of maturation and primary and accessory corpora lutea were observed in the cortex. These structures were smaller than those present in other related species. Follicles did not project into the surface of the organ. Calcified follicles of diverse size were found in all the ovaries. Atretic follicles were found in all the stages analysed. Interstitial tissue surrounding the follicles and the corpora lutea was also observed. The number and proportion of different cortical structures varied in the physiological stages analysed. The ovaries of the viscacha have differential characteristics in comparison to other Hystricognathi, some of them related to polyovulation. [source] Polycyclic aromatic hydrocarbon bioaccumulation by meiobenthic copepods inhabiting a superfund site: Techniques for micromass body burden and total lipid analysisENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2002Susan L. Klosterhaus Abstract Microtechniques for polycyclic aromatic hydrocarbon (PAH) body burden and total lipid analysis were developed and applied to determine the first lipid-normalized bioaccumulation factors for a hydrophobic organic toxicant in a meiobenthic organism (0.063-0.500 mm) living in field-contaminated sediments. The total lipid microtechnique combines the standard Bligh-Dyer extraction method with a colorimetric quantification method for analysis of samples containing 1 to 50 ,g lipid. The microtechnique for body burden analysis quantifies PAHs from tissue samples containing as little as 10 pg PAH. Fluoranthene, benz[a]anthracene, and benzo[a]pyrene biota-sediment accumulation factors (BSAFs) were determined for the meiobenthic copepod Microarthridion littorale living in an estuarine U.S. Environmental Protection Agency Superfund site. Gravid female, nongravid female, and male BSAFs were 0.82, 0.54, and 0.36, respectively, for fluoranthene; 0.50, 0.44, and 0.40, respectively, for benz[a]anthracene; and 0.09, 0.12, and 0.15, respectively, for benzo[a]pyrene. Comparison of nonlipid-normalized bioaccumulation factors (BAFs) to BSAFs indicates that M. littorale bioaccumulated PAHs on a gram lipid basis. The BSAFs declined consistently with increasing PAH log Kow for all copepod sex and reproductive stages. Sex- and stage-specific comparisons of BSAFs suggest that differences in lipid content and quality may lead to differences in BSAF values depending on PAH molecular weight and/or hydrophobicity. [source] Calcium supplementation of breeding birds: directions for future researchIBIS, Issue 4 2004S. James Reynolds Calcium is an essential nutrient for avian reproduction. Calcium-rich foods are consumed by breeding birds for production of eggshells and for provisioning chicks that are mineralizing skeletal tissues. A number of studies have documented calcium-limited reproduction, and calcium supplementation has been employed over the last decade to demonstrate degrees, causes and consequences of calcium limitation. However, supplementation studies have produced equivocal findings resulting from an absence of calcium limitation in the study species, a poorly designed supplementation procedure or both. Prior to effective calcium supplementation, many factors need to be considered. Calcium-limited breeding in birds can only be detected by monitoring breeding attempts for more than one year and by ensuring that the measured breeding parameters are sensitive to calcium availability. Natural calcium availability needs to be estimated, and daily calcium budgets for the appropriate reproductive stages determined for the study species. Most crucially, if calcium limitation of breeding is caused by secondary calcium limitation (e.g. through heavy metal toxicity), calcium supplementation will probably be ineffective. Effective calcium supplementation will then be achieved through careful planning , a study over several years using appropriate supplements (i.e. naturally occurring ones used by breeding birds), applied at the appropriate time of year (i.e. prelaying and/or chick-rearing phases) and using a response variable that is highly sensitive to calcium availability. If properly planned and performed, calcium supplementation is a cost-effective and potent tool for the study of bird breeding biology. [source] Developmental biology of medaka fish (Oryzias latipes) exposed to alkalinity stressJOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2010Z. L. Yao Summary Alkalinity stress is common in cultured aquatic animals and considered to be one of the major stress factors for fishes when they are transferred to saline-alkali waters. To evaluate potential effects of alkalinity on the developmental biology of Oryzias latipes, fertilized eggs, larvae and breeding fish were exposed to different carbonate alkalinity concentrations of 1.5,64.5 meq l,1, for 9, 120, and 60 days, respectively. The mortality of embryos significantly increased when exposed to the high concentrations (16.5,64.5 meq l,1). Although more than 50% of survived embryos hatched in 16.5 and 31.4 meq l,1 concentrations of carbonate alkalinity, most were not able to swim up after hatching. Morphological abnormalities such as coagulated embryos, halted embryo development, and hatching failure were observed at stages 15, 29,33 and 38 in high concentrations (31.4, 64.5 meq l,1). Almost all larvae in 16.5 and 31.4 meq l,1 treatments died 70 d post-hatch. Growth of juveniles exposed to carbonate alkalinity of 5.3 and 8.8 meq l,1 was not significantly different at 70 d and 120 d post-hatch. The number of eggs released by breeders, the fertilization rate and the hatching rate of eggs were significantly lower in the 31.4 meq l,1 treatment than in other treatments. Although medaka are capable of surviving in high alkalinities (31.4, 64.5 meq l,1) for an extended period of time, these conditions are stressful to the fish, especially at the embryonic and reproductive stages. [source] Reproduction in Bagre marinus (Ariidae) off Pernambuco, northeastern BrazilJOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2006P. Pinheiro Summary Throughout 1997, the catches of artisanal gillnetters working off the coast of northeastern Brazil were sampled monthly for Bagre marinus (Mitchill 1815). Significantly more females (n = 207) than males (n = 82) were caught, although there was no significant difference in their size compositions (21,47 cm fork length, FL). All males sampled (21,40 cm FL) had developed gonads and were classified as sexually mature. According to macroscopic and microscopic examination of their reproductive tract, females were separated into four reproductive stages (immature, maturing, mature, and resting). Size at 50% sexual maturity for females was estimated to be 33 cm FL. A positive linear relationship was detected between the size of mature females and their fecundity (between 11 and 32 oocytes). Clear reproductive progress indicated a spawning period between March and May. We conclude that further fishery-independent data are required to determine patterns of male abundances and distributions. [source] Stress-induced dynamic adjustments of reproduction differentially affect fitness components of a semi-arid plantJOURNAL OF ECOLOGY, Issue 1 2008Cristina F. Aragón Summary 1Summer drought stress is considered the primary constraint to plant performance in Mediterranean ecosystems. However, little is known about the implications of summer stress for plant reproduction under real field conditions and, particularly, for the regulatory mechanisms of maternal investment in reproduction. 2The relationship between plant physiological status at different reproductive stages over the course of the summer drought period and final reproductive output was modelled in the Mediterranean semi-arid specialist Helianthemum squamatum. 3Plant physiological status, assessed by the chlorophyll fluorescence-based parameter Fv/Fm, and soil moisture content beneath each plant, were determined in the field at five key phenological moments in a total of 88 plants. We used Generalized Linear Mixed Models to evaluate the effect of plant physiological status at those different dates on several components of reproduction (number of flowers and seeds per plant, fruit-set and intra-fruit seed abortion). We included soil moisture as an additional predictor to statistically control its potential effect on reproduction. 4Fv/Fm measured at midday was a significant predictor of reproductive output, but its significance varied over time and with the specific reproductive response variable. Fv/Fm measured at the onset of flowering was positively related to the number of flowers and seeds per plant, whereas Fv/Fm at the fruiting peak positively affected fruit-set. Soil moisture content was only significant when measured before flowering, being positively related to total flowers and seeds. The effect of stress on reproductive output acted either at an early stage of the reproductive season, by varying the number of flowers produced and seed primordia initiated, or at a later stage, by adjusting the number or ripe fruits. 5Synthesis. Our results show a direct relationship between physiological status and reproduction, and highlight the importance of the timing of stress for reproductive success. They also show that small departures from the physiological optimum at specific reproductive stages may cause significant decreases in the reproductive output. We suggest that the dynamic adjustment of reproduction in response to stress is adaptive in fluctuating and unpredictable Mediterranean semi-arid environments, where an adequate temporal distribution of maternal resources determines the species' ability to withstand severe environmental conditions. [source] HOMOTHALLIC AUXOSPORULATION IN PSEUDO-NITZSCHIA BRASILIANA (BACILLARIOPHYTA),JOURNAL OF PHYCOLOGY, Issue 1 2009Sonia Quijano-Scheggia Most pennate diatoms are allogamous, and various types of mating systems have been described. In Pseudo-nitzschia, reproductive stages have been identified in some species, and it is generally accepted that the genus is mainly heterothallic. Here we report homothallic auxosporulation of Pseudo-nitzschia brasiliana Lundholm, Hasle et G. A. Fryxell. To our knowledge, this is the first verified description of homothallic sexual reproduction in the genus. Auxospore formation was observed in all 16 subclones derived from three initial clonal cultures of P. brasiliana. Pairing was followed by production of two gametes per gametangium, which fused to give two zygotes. Each zygote (early auxospore) was initially spherical and adhered to one girdle band of the parental frustule. The two auxospores tended to expand parallel to each other and perpendicular to the parental frustule. Elongation was synchronous, slightly asynchronous, or totally asynchronous. The entire process of sexual reproduction, from gamete formation to the appearance of the initial vegetative cells, took 2,4 d. The occurrence of sex in a homothallic species seems an advantageous life strategy for this species in that any encounter between cells of the right size class is potentially sexual. [source] Effects of thiol compounds on in vitro maturation of canine oocytes collected from different reproductive stagesMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 9 2007Mohammad Shamim Hossein Abstract Various thiol compounds are known to improve cytoplasmic and/or nuclear maturation of oocytes in vitro. The present study examined the effects of two thiol compounds, cysteine (0.1, 0.5, and 1.0 mM) and cysteamine (50, 100, and 200 µM), on cytoplasmic and nuclear maturation of canine oocytes. Oocytes collected from different reproductive stages were cultured in TCM-199 supplemented with 10% fetal bovine serum, 2.2 mg/ml sodium carbonate, 2.0 µg/ml estrogen, 0.5 µg/ml FSH, 0.03 IU/ml hCG, and 1% penicillin,streptomycin solution for 72 h. Data were analyzed by two-way ANOVA after arcscine transformation and protected by Bonferroni post hoc test. The effects of cysteine and cysteamine on canine IVM were varied depending on the reproductive stage of oocyte donor bitches. In the follicular stage, significantly more oocytes reached the metaphase II (M II) stage when cultured with 0.5 or 1.0 mM cysteine (16.7% and 16.9%, respectively) compared to the control (6.2%). In the follicular stage, cysteamine increased oocyte maturation rate upto the M II stage (15.1% to 17.0%) compared to the control (4.4%). Both the 0.5 mM cysteine and 100 µM cysteamine, alone or together, increased the intracellular GSH level of canine oocytes compared to the control. Irrespective of reproductive stage, no further beneficial effects on nuclear or cytoplasmic maturation were observed when 0.5 mM cysteine and 100 µM cysteamine were supplemented together. In conclusion, addition of 0.5 mM cysteine and 100 µM cysteamine to the maturation medium improved IVM of canine oocytes. Mol. Reprod. Dev. 74: 1213,1220, 2007. © 2007 Wiley-Liss, Inc. [source] Anatomicohistological Characteristics of the Female Genital Organs of the White-lipped Peccary (Tayassu pecari) in the Peruvian AmazonANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 6 2009P. Mayor Summary This study examined the anatomical and histological characteristics of the genital organs of the female white-lipped peccary in the wild in different reproductive stages, collected by rural hunters in the North-eastern Peruvian Amazon. Mean ovulation rate was 2.12 ± 0.83 follicles and litter size was 1.78 ± 0.41 embryos or fetuses per pregnant female, resulting in a low rate of reproductive wastage, averaging 0.33 ± 0.66 (16.04%) oocytes or embryos per pregnancy. The ovulation rate and the anatomical performance of the uterus could limit the prolificacy of this species. Females in follicular phase showed follicular waves suggesting the synchronous growth of a cohort of follicles. Different uterine and vaginal epithelium features changed in accordance with the reproductive state of the female. Pregnant females and females in the luteal phase presented a significant proliferation of endometrial uterine glands, characterized by hyperplasia and branching of endometrial glands, and increase in the proportion of cervical epithelial cells with periodic acid-schiff (PAS)-positive granules compared with that in females in the follicular phase. Females in the follicular phase showed a more developed vaginal epithelium (in thickness and in layer composition) than females in the luteal phase and pregnant females. [source] | |||||||||||||