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Diurnal
Terms modified by Diurnal Selected AbstractsDaily rhythms and sex differences in vasoactive intestinal polypeptide, VIPR2 receptor and arginine vasopressin mRNA in the suprachiasmatic nucleus of a diurnal rodent, Arvicanthis niloticusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2009M. M. Mahoney Abstract Diurnal and nocturnal animals differ with respect to the time of day at which the ovulatory surge in luteinizing hormone occurs. In some species this is regulated by the suprachiasmatic nucleus (SCN), the primary circadian clock, via cells that contain vasoactive intestinal polypeptide (VIP) and vasopressin (AVP). Here, we evaluated the hypothesis that chronotype differences in the timing of the luteinizing hormone surge are associated with rhythms in expression of the genes that encode these neuropeptides. Diurnal grass rats (Arvicanthis niloticus) were housed in a 12/12-h light,dark cycle and killed at one of six times of day (Zeitgeber time 1, 5, 9, 13, 17, 21; ZT 0 = lights-on). In-situ hybridization was used to compare levels of vip, avp and VIP receptor mRNA (vipr2) in the SCN of intact females, ovariectomized females, ovariectomized females given estradiol and intact males. We found a sex difference in vip rhythms with a peak occurring at ZT 13 in males and ZT 5 in intact females. In all groups avp mRNA rhythms peaked during the day, from ZT 5 to ZT 9, and had a trough in the dark at ZT 21. There was a modest rhythm and sex difference in the pattern of vipr2. Most importantly, the patterns of each of these SCN rhythms relative to the light,dark cycle resembled those seen in nocturnal rodents. Chronotype differences in timing of neuroendocrine events associated with ovulation are thus likely to be generated downstream of the SCN. [source] Diurnal and seasonal variation in methane emissions in a northern Canadian peatland measured by eddy covarianceGLOBAL CHANGE BIOLOGY, Issue 9 2010KEVIN D. LONG Abstract Eddy covariance measurements of methane (CH4) net flux were made in a boreal fen, typical of the most abundant peatlands in western Canada during May,September 2007. The objectives of this study were to determine: (i) the magnitude of diurnal and seasonal variation in CH4 net flux, (ii) the relationship between the temporally varying flux rates and associated changes in controlling biotic and abiotic factors, and (iii) the contribution of CH4 emission to the ecosystem growing season carbon budget. There was significant diurnal variation in CH4 emission during the peak of the growing season that was strongly correlated with associated changes in solar radiation, latent heat flux, air temperature and ecosystem conductance to water vapor. During days 181,215, nighttime average CH4 efflux was only 47% of the average midday values. The peak value for daily average CH4 emission rate was approximately 80 nmol m,2 s,1 (4.6 mg CH4 m,2 h,1), and seasonal variation in CH4 flux was strongly correlated with changes in soil temperature. Integrated over the entire measurement period [days 144,269 (late May,late September)], the total CH4 emission was 3.2 g CH4 m,2, which was quite low relative to other wetland ecosystems and to the simultaneous high rate of ecosystem net CO2 sequestration that was measured (18.1 mol CO2 m,2 or 217 g C m,2). We estimate that the negative radiative forcing (cooling) associated with net carbon storage over the life of the peatland (approximately 2200 years) was at least twice the value of positive radiative forcing (warming) caused by net CH4 emission over the last 50 years. [source] Sap flow of Artemisia ordosica and the influence of environmental factors in a revegetated desert area: Tengger Desert, ChinaHYDROLOGICAL PROCESSES, Issue 10 2010Huang Lei Abstract Artemisia ordosica is considered as an excellent sand-fixing plant in revegetated desert areas, which plays a pertinent role in stabilizing the mobile dunes and sustaining the desert ecosystems. Stem sap flows of about 10-year-old Artemisia ordosica plants were monitored continuously with heat balance method for the entire growing season in order to understand the water requirement and the effects of environmental factors on its transpiration and growth. Environment factors such as solar radiation, air temperatures, relative humidity, wind speed and precipitation were measured by the eddy covariance. Diurnal and seasonal variations of sap flow rate with different stem diameters and their correlation with meteorological factors and reference evapotranspiration were analysed. At the daily time scale, there was a significantly linear relationship between sap flow rate and reference evapotranspiration with a correlation coefficient of R2 = 0·6368. But at the hourly time scale, the relationship of measured sap flow rate and calculated reference evapotranspiration (ET0) was affected by the precipitation. A small precipitation would increase the sap flow and the ET0; however, when the precipitation is large, the sap flow and ET0 decrease. Leaf area index had a coincident variation with soil water content; both were determined by the precipitation, and meteorological factors were the most significant factors that affected the sap flow of Artemisia ordosica in the following order: solar radiation > vapour pressure deficit > relative humidity > air temperature > wind speed. The close correlation between daily sap flow rate and meteorological factors in the whole growing season would provide us an accurate estimation of the transpiration of Artemisia ordosica and rational water-carrying capacity of sand dunes in the revegetated desert areas. Copyright © 2010 John Wiley & Sons, Ltd. [source] Leaflet Movement of Robinia pseudoacacia in Response to a Changing Light EnvironmentJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 4 2007Cheng-Cheng Liu Abstract Diurnal and nocturnal leaflet movement of black locust (Robinia pseudoacacia L.) was investigated under three light schemes: 100% natural irradiance, 50% shading, and 90% shading. Changes in leaf mid-vein angle were described by measurements of two planes: (i) ,, the angle formed by the bottom of the petiolule and its relation to the horizontal plane; and (ii) ,, the angle between the petiolule and the main leaflet vein. The two highest light regimens had a significant effect on ,. Variation in , tends to make the leaflet more erect, thereby minimizing any negative impact of high irradiance on leaf lamina. Light-dark rhythms induced variation in , (termed nyctinastic movement). Nyctinastic movement is important during the low light levels experienced by leaflets in early morning and late afternoon. At low light levels, the leaflet stopped nyctinastic movement and , was fixed at an angle that may have enabled the leaf lamina to maximize light interception. After the light-dark cycle was reestablished, nyctinastic movement was restored. Taken together, our results suggest that irradiance induces variation in , leading to diurnal leaflet movement (diaheliotropism), whereas the light-dark cycle influences ,, which results in nocturnal leaflet movement. Both angles are important for describing patterns of leaf movement in R. pseudocacia. [source] Modulation of vertebral and tibial growth by compression loading: Diurnal versus full-time loadingJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2005Ian A. Stokes Abstract Purpose: This study was designed to determine whether the amount of endochondral growth response to mechanical compression and the underlying growth mechanism differed with night-time or day-time loading, relative to full-time loading. Methods: Mechanical compression (nominally 0.1 MPa stress) was applied across tibial and tail vertebral growth plates of growing Sprague,Dawley rats. Four groups of animals (five per group) were used: 24/24 h (full-time loading); 12/24 h (day-loading); 12/24 h (night-loading); and 0/24 h (sham instrumented). Contralateral tibiae and adjacent vertebrae served as within-animal controls. The animals were euthanized after eight days. Growth plates were processed for quantitative histology to measure 24-h growth, total and BrdU-positive proliferative zone chondrocyte counts, and hypertrophic chondrocytic enlargement in the growth direction. Results: Growth as a percentage of within-animal control averaged 82% (full-time); 93% (day-loading); 90% (night-loading); 100% (sham) for vertebrae. For proximal tibiae it averaged 70% (full-time); 84% (day-loading); 86% (night-loading); 89% (sham). Reduced amount of hypertrophic chondrocytic enlargement explained about half of this effect in full-time loaded growth plates, but was not significantly altered in half-time loaded growth plates. The remaining variation in growth was apparently explained by reduced total numbers of proliferative zone chondrocytes. These findings indicate that sustained compression loading suppressed growth more than intermittent loading at both anatomical locations. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Diurnal and seasonal variations in stomatal conductance of rice at elevated atmospheric CO2 under fully open-air conditionsPLANT CELL & ENVIRONMENT, Issue 3 2010HIROYUKI SHIMONO ABSTRACT Understanding of leaf stomatal responses to the atmospheric CO2 concentration, [CO2], is essential for accurate prediction of plant water use under future climates. However, limited information is available for the diurnal and seasonal changes in stomatal conductance (gs) under elevated [CO2]. We examined the factors responsible for variations in gs under elevated [CO2] with three rice cultivars grown in an open-field environment under flooded conditions during two growing seasons (a total of 2140 individual measurements). Conductance of all cultivars was generally higher in the morning and around noon than in the afternoon, and elevated [CO2] decreased gs by up to 64% over the 2 years (significantly on 26 out of 38 measurement days), with a mean gs decrease of 23%. We plotted the gs variations against three parameters from the Ball-Berry model and two revised versions of the model, and all parameters explained the gs variations well at each [CO2] in the morning and around noon (R2 > 0.68), but could not explain these variations in the afternoon (R2 < 0.33). The present results provide an important basis for modelling future water use in rice production. [source] Diurnal and oviposition-related changes in heart rate, body temperature and locomotor activity of laying hensANIMAL SCIENCE JOURNAL, Issue 2 2004Ashraf M. KHALIL ABSTRACT Diurnal and oviposition patterns of heart rate (HR), deep body temperature (BT) and locomotor activity (LA) in conscious and unrestrained Rhode Island Red hens were studied by a radiotelemetry system. Behavioral observations were also made on diurnal changes and during the pre- and post-laying period. Heart rate, BT and LA showed characteristic diurnal changes synchronized with a photoperiod of 15 h light and 9 h dark. In the light period, HR, BT, and LA levels were significantly higher than in the dark period (P < 0.001). Furthermore, the highest levels of these parameters were recorded just after they were fed (08.30 hours), while the lowest level was measured after lights-off and remained stable throughout the dark period. Behavioral observations indicated that during the light period the hens spent most of their time in very active movement, exhibiting various behavioral patterns. However, in the dark period the hens spent almost all their time resting. The present results suggest that performing various behavioral activities cause heat generated by muscle exertion, which plays a significant role in daily HR, BT, and LA in laying hens. However, during the 60 min before and after oviposition, LA appeared to have increased steadily toward the moment of laying, and then regressed gradually in the post-laying period to a level significantly lower than in the pre-laying period (P < 0.001). Furthermore, the pre-laying behavior of hens indicated extreme restlessness and more activity, whereas the post-laying period is characterized by less activity and increased relaxation. Consequently, laying behavior has a profound but transitory effect on HR and BT, suggesting that oviposition was probably associated with intense LA. [source] Diurnal and semidiurnal rainfall cycles during the rain season in SW Amazonia, observed via rain gauges and estimated using S-band radarATMOSPHERIC SCIENCE LETTERS, Issue 2 2009Cláudio Moisés Santos e Silva Abstract The rainfall field estimated by an S-band radar was evaluated with rain gauges network measurements during the Tropical Rainfall Measuring Mission and Large-Scale Biosphere,Atmosphere Experiment in Amazonia (TRMM-LBA), then the daily variability associated with the presence (absence) of the South Atlantic convergence zone (SACZ) were studied. The results showed the high spatial variability of the rainfall over southwest (SW) Amazonia and suggest that local mechanisms (topography and/or local circulations induced by contrast of vegetation) may be associated with heavy rainfall episodes; moreover, it was possible to observe the squall line influence on the diurnal and semidiurnal cycles. Copyright © 2009 Royal Meteorological Society [source] Effects of Conversion of Dry Tropical Forest to Agricultural Mosaic on Herpetofaunal AssemblagesCONSERVATION BIOLOGY, Issue 2 2008IRERI SUAZO-ORTUÑO atributos de vulnerabilidad; bosque tropical seco; ensambles herpetofaunísticos; modificación del hábitat; mosaico agrícola Abstract:,We explored the impact of forest conversion to agricultural mosaic on anuran, lizard, snake, and turtle assemblages of Neotropical dry forests. Over 2 years, we sampled 6 small watersheds on the west coast of Mexico, 3 conserved and 3 disturbed. The disturbed watersheds were characterized by a mosaic of pastures and cultivated fields (corn, beans, squash) intermingled with patches of different successional stages of dry forest. In each watershed, we conducted 11 diurnal and nocturnal time-constrained searches in 10 randomly established plots. We considered vulnerability traits of species in relation to habitat modification. Eighteen anuran, 18 lizard, 23 snake, and 3 turtle species were recorded. Thirty-six species (58%) occurred in both forest conditions, and 14 (22%) and 12 species (19%) occurred only in the conserved and disturbed sites, respectively. Assemblages responded differently to disturbance. Species richness, diversity, and abundance of lizards were higher in disturbed forests. Anuran diversity and species richness were lower in disturbed forest but abundance was similar in both forest conditions. Diversity, richness, and abundance of turtles were lower in disturbed forest. The structure and composition of snake assemblages did not differ between forest conditions. We considered species disturbance sensitive if their abundance was significantly less in disturbed areas. Four anuran (22%), 2 lizard (11%), and 3 turtle (100%) species were sensitive to disturbance. No snake species was sensitive. The decline in abundance of disturbance-sensitive species was associated with the reduction of forest canopy cover, woody stem cover, roots, and litter-layer ground cover. Anuran species with small body size and direct embryonic development were especially sensitive to forest disturbance. An important goal for the conservation of herpetofauna should be the determination of species traits associated with extinction or persistence in agricultural mosaics. Resumen:,Exploramos el impacto de la conversión de bosques a mosaico agrícola sobre ensambles de lagartijas, serpientes y tortugas de bosques Neotropicales secos. Durante 2 años muestreamos 6 cuencas pequeñas, 3 conservadas y 3 perturbadas, en la costa occidental de México. Las cuencas perturbadas se caracterizaron por un mosaico de pastizales y campos cultivados (maíz, frijol, calabaza) entremezclados con parches de bosque seco en diferentes etapas sucesionales. En cada cuenca, realizamos 11 búsquedas diurnas y nocturnas en 10 parcelas establecidas aleatoriamente. Consideramos los atributos de vulnerabilidad de especies en relación con la modificación del hábitat. Registramos 18 especies de lagartijas, 23 de serpientes y 3 de tortugas. Treinta y seis especies (58%) ocurrieron en ambas condiciones de bosque, y 14 (22%) y 12 (19%) especies solo ocurrieron en los sitios conservados y perturbados, respectivamente. Los ensambles respondieron a la perturbación de manera diferente. La riqueza de especies, la diversidad y la abundancia de lagartijas fueron mayores en los bosques perturbados. La diversidad y riqueza de especies de anuros fueron menores en el bosque perturbado pero la abundancia fue similar en ambas condiciones de bosque. La diversidad, riqueza de especies y abundancia de tortugas fueron menores en el bosque perturbado. La estructura y la composición de los ensambles de serpientes no difirieron entre condiciones de bosque. Consideramos que las especies eran sensibles a la perturbación si su abundancia fue significativamente menor en las áreas perturbadas. Cuatro (22%) especies de anuros, 2 (11%) de lagartijas y 3 (100%) de tortugas fueron sensibles a la perturbación. Ninguna especie de serpiente fue sensible. La declinación en la abundancia de especies sensibles a la perturbación se asoció con la reducción en la cobertura del dosel, de tallos leñosos, raíces y hojarasca. Las especies de anuros de cuerpo pequeño y desarrollo embrionario directo fueron especialmente sensibles a la perturbación del bosque. La determinación de atributos de las especies asociadas con su extinción o persistencia en mosaicos agrícolas debería ser una meta importante para la conservación de la herpetofauna. [source] Daily and developmental modulation of "premotor" activity in the birdsong system,DEVELOPMENTAL NEUROBIOLOGY, Issue 12 2009Nancy F. Day Abstract Human speech and birdsong are shaped during a sensorimotor sensitive period in which auditory feedback guides vocal learning. To study brain activity as song learning occurred, we recorded longitudinally from developing zebra finches during the sensorimotor phase. Learned sequences of vocalizations (motifs) were examined along with contemporaneous neural population activity in the song nucleus HVC, which is necessary for the production of learned song (Nottebohm et al. 1976: J Comp Neurol 165:457,486; Simpson and Vicario 1990: J Neurosci 10:1541,1556). During singing, HVC activity levels increased as the day progressed and decreased after a night of sleep in juveniles and adults. In contrast, the pattern of HVC activity changed on a daily basis only in juveniles: activity bursts became more pronounced during the day. The HVC of adults was significantly burstier than that of juveniles. HVC bursting was relevant to song behavior because the degree of burstiness inversely correlated with the variance of song features in juveniles. The song of juveniles degrades overnight (Deregnaucourt et al. 2005: Nature 433:710,716). Consistent with a relationship between HVC activity and song plasticity (Day et al. 2008: J Neurophys 100:2956,2965), HVC burstiness degraded overnight in young juveniles and the amount of overnight degradation declined with developmental song learning. Nocturnal changes in HVC activity strongly and inversely correlated with the next day's change, suggesting that sleep-dependent degradation of HVC activity may facilitate or enable subsequent diurnal changes. Collectively, these data show that HVC activity levels exhibit daily cycles in adults and juveniles, whereas HVC burstiness and song stereotypy change daily in juveniles only. In addition, the data indicate that HVC burstiness increases with development and inversely correlates with song variability, which is necessary for trial and error vocal learning. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] Defining and measuring braiding intensityEARTH SURFACE PROCESSES AND LANDFORMS, Issue 14 2008Roey Egozi Abstract Geomorphological studies of braided rivers still lack a consistent measurement of the complexity of the braided pattern. Several simple indices have been proposed and two (channel count and total sinuosity) are the most commonly applied. For none of these indices has there been an assessment of the sampling requirements and there has been no systematic study of the equivalence of the indices to each other and their sensitivity to river stage. Resolution of these issues is essential for progress in studies of braided morphology and dynamics at the scale of the channel network. A series of experiments was run using small-scale physical models of braided rivers in a 3 m , 20 m flume. Sampling criteria for braid indices and their comparability were assessed using constant-discharge experiments. Sample hydrographs were run to assess the effect of flow variability. Reach lengths of at least 10 times the average wetted width are needed to measure braid indices with precision of the order of 20% of the mean. Inherent variability in channel pattern makes it difficult to achieve greater precision. Channel count indices need a minimum of 10 cross-sections spaced no further apart than the average wetted width of the river. Several of the braid indices, including total sinuosity, give very similar numerical values but they differ substantially from channel-count index values. Consequently, functional relationships between channel pattern and, for example, discharge, are sensitive to the choice of braid index. Braid indices are sensitive to river stage and the highest values typically occur below peak flows of a diurnal (melt-water) hydrograph in pro-glacial rivers. There is no general relationship with stage that would allow data from rivers at different relative stage to be compared. At present, channel count indices give the best combination of rapid measurement, precision, and range of sources from which measurements can be reliably made. They can also be related directly to bar theory for braided pattern development. Copyright © 2008 John Wiley & Sons, Ltd. [source] Feeding ecology of fishes associated with Egeria spp. patches in a tropical reservoir, BrazilECOLOGY OF FRESHWATER FISH, Issue 1 2006F. M. Pelicice Abstract ,, This research characterised feeding ecology of fishes associated with patches of Egeria najas and Egeria densa, two submerged macrophytes, in Rosana Reservoir, Upper Paraná River basin, Brazil. Fishes were sampled using a 1 m2 throw trap in patches of different macrophyte biomass and in three diel periods during a wet season. Fish diet (10 species) was primarily composed of autochthonous items (zooplankton, algae and aquatic insect larvae). Almost all intra-specific diet patterns had moderate to low levels of diet similarity, indicating a high variability in diet. Some species showed no diel patterns in feeding activity, whereas others were primarily diurnal or nocturnal. No differences in feeding activity were observed among habitats of medium and high macrophyte biomasses, and species tended to feed on the same items among these habitats. The most abundant fish species demonstrated low inter-specific diet overlap and appear not to compete for food resources. We suggest that Egeria patches are feeding grounds and shelter for small-sized fish species. Resumen 1. Esta investigación caracterizó la ecología trófica de las especies de peces asociadas a manchas de Egeria najas e E. densa, dos macrofitas sub-aquaticas, en la represa de Rosana (alto Río Paraná, Brasil). Los peces fueron colectados con un throw trap de 1 m2 en manchas con distintas biomasas de macrófitas y en tres períodos del día, durante la estación lluviosa. 2. La dieta de 10 especies estuvo compuesta principalmente de componentes autóctonos (zooplancton, algas y larva de insectos acuáticos). Casi todas las especies presentaron patrones de dieta intra-específica con similitudes moderadas o bajas (elevada variabilidad). Algunas especies no mostraron ningún patrón de actividad alimenticia durante el día mientras que otras fueron principalmente diurnas o nocturnas. No se observó ninguna diferencia de actividad alimenticia entre los habitats de media y alta biomasa de macrófitas, y las especies tendieron a alimentarse de los mismos componentes entre estos habitats. 3. Las especies de peces más abundantes mostraron un solapamiento alimenticio bajo y parecen no competir por recursos alimenticios. Sugerimos que las manchas de Egeria funcionan como lugar de alimentación y abrigo para los peces de pequeño tamaño. [source] Automated diffusion chambers to monitor diurnal and seasonal dynamics of the soil CO2 concentration profileEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2009F. Albanito Summary To better understand the factors controlling carbon dioxide (CO2) production and transport in soil, we developed a new method to continuously monitor soil CO2 concentration at multiple depths, by using diffusion chambers. The soil diffusion chambers are constructed from a high-density polyethylene cylindrical frame enclosed by a micro-polyvinylidene difluoride flat membrane (PVDF). All chambers are linked to an infrared gas analyser positioned above-ground through a multi-port valve system. We set up two experimental sites for long-term measurements of soil CO2 concentration, soil temperature and soil water content at depths of 0, 10, 20, 40 and 80 cm. The system provides the following advantages : (i) the use of the PVDF combined with the small dimensions of the diffusion chambers allows rapid diffusion of soil gas into the chambers and therefore a short equilibration time of the gas phase with the surrounding soil atmosphere, (ii) the equilibrating closed loop system allows the semi-continuous measurement of soil profile CO2 concentrations without creating a pressure differential within the chambers, thus reducing gas concentration distortions in the soil, (iii) the small size of the closed diffusion chambers reduces the initial soil disturbance during installation, (iv) it allows sampling in wet, humid soils, including ones that are waterlogged or temporarily saturated, and (v) the chambers do not require removal for maintenance purposes and are inexpensive. [source] Day,night changes in the spatial distribution and habitat preferences of freshwater shrimps, Gammarus pulex, in a stony streamFRESHWATER BIOLOGY, Issue 4 2005J. M. ELLIOTT Summary 1. As many invertebrates are nocturnal, their spatial distribution and habitat preferences may change from day to night. Both aspects are examined for Gammarus pulex by testing the hypotheses: (i) a power function was a suitable model for the spatial distribution of the shrimps in both day and night; (ii) diurnal and nocturnal spatial distributions were significantly different; (iii) diurnal and nocturnal habitat preferences were significantly different. Five different life-stages were treated separately. To ensure that the conclusions were consistent, large samples were taken near midday and midnight in April, June and November over 4 years at two sites about 3 km apart in a stony stream: downstream (n = 30) and upstream (n = 50). 2. The first and second hypotheses were supported at both sites. A power function, relating spatial variance (s2) to mean (m), was an excellent fit in all analyses (P < 0.001, r2 > 0.91), i.e. the spatial variance was density-dependent. All five life-stages were aggregated in the day. At night, the degree of aggregation increased for juveniles at higher densities but decreased for juveniles at lower densities, increased for immature females and males, but decreased slightly for mature females and especially mature males, the latter being close to a random distribution. There were no significant differences between sites, in spite of the lower numbers at the downstream site. 3. The third hypothesis was tested at only the upstream site and supported by comparisons between shrimp densities and 13 physical variables (distance from bank, water depth, water velocity, ten particle size-classes), and three non-physical variables (dry weights of bryophytes, leaf material, organic detritus). During the day, densities were strongly related to particle sizes with the following preferences: 0.5,8 mm for juveniles, 8,256 mm for the other life-stages with a weaker relationship for males. There were no significant positive relationships with the other variables, apart from bryophytes for immature shrimps and adults. At night, densities were unrelated to particle size; juveniles and immature shrimps preferred low water velocities near the banks, often where leaf material and organic detritus accumulated, females often preferred medium water velocities slightly away from the banks, and males showed no habitat preferences. 4. Day samples do not provide a complete picture of habitat preferences and probably identify refuge habitats. Day,night changes in spatial distribution and habitat preferences are an essential part of the behavioural dynamics of the shrimps and should be investigated in other species. [source] Diurnal and seasonal variation in methane emissions in a northern Canadian peatland measured by eddy covarianceGLOBAL CHANGE BIOLOGY, Issue 9 2010KEVIN D. LONG Abstract Eddy covariance measurements of methane (CH4) net flux were made in a boreal fen, typical of the most abundant peatlands in western Canada during May,September 2007. The objectives of this study were to determine: (i) the magnitude of diurnal and seasonal variation in CH4 net flux, (ii) the relationship between the temporally varying flux rates and associated changes in controlling biotic and abiotic factors, and (iii) the contribution of CH4 emission to the ecosystem growing season carbon budget. There was significant diurnal variation in CH4 emission during the peak of the growing season that was strongly correlated with associated changes in solar radiation, latent heat flux, air temperature and ecosystem conductance to water vapor. During days 181,215, nighttime average CH4 efflux was only 47% of the average midday values. The peak value for daily average CH4 emission rate was approximately 80 nmol m,2 s,1 (4.6 mg CH4 m,2 h,1), and seasonal variation in CH4 flux was strongly correlated with changes in soil temperature. Integrated over the entire measurement period [days 144,269 (late May,late September)], the total CH4 emission was 3.2 g CH4 m,2, which was quite low relative to other wetland ecosystems and to the simultaneous high rate of ecosystem net CO2 sequestration that was measured (18.1 mol CO2 m,2 or 217 g C m,2). We estimate that the negative radiative forcing (cooling) associated with net carbon storage over the life of the peatland (approximately 2200 years) was at least twice the value of positive radiative forcing (warming) caused by net CH4 emission over the last 50 years. [source] Estimating diurnal to annual ecosystem parameters by synthesis of a carbon flux model with eddy covariance net ecosystem exchange observationsGLOBAL CHANGE BIOLOGY, Issue 2 2005Bobby H. Braswell Abstract We performed a synthetic analysis of Harvard Forest net ecosystem exchange of CO2 (NEE) time series and a simple ecosystem carbon flux model, the simplified Photosynthesis and Evapo-Transpiration model (SIPNET). SIPNET runs at a half-daily time step, and has two vegetation carbon pools, a single aggregated soil carbon pool, and a simple soil moisture sub-model. We used a stochastic Bayesian parameter estimation technique that provided posterior distributions of the model parameters, conditioned on the observed fluxes and the model equations. In this analysis, we estimated the values of all quantities that govern model behavior, including both rate constants and initial conditions for carbon pools. The purpose of this analysis was not to calibrate the model to make predictions about future fluxes but rather to understand how much information about process controls can be derived directly from the NEE observations. A wavelet decomposition enabled us to assess model performance at multiple time scales from diurnal to decadal. The model parameters are most highly constrained by eddy flux data at daily to seasonal time scales, suggesting that this approach is not useful for calculating annual integrals. However, the ability of the model to fit both the diurnal and seasonal variability patterns in the data simultaneously, using the same parameter set, indicates the effectiveness of this parameter estimation method. Our results quantify the extent to which the eddy covariance data contain information about the ecosystem process parameters represented in the model, and suggest several next steps in model development and observations for improved synthesis of models with flux observations. [source] Simulated and observed fluxes of sensible and latent heat and CO2 at the WLEF-TV tower using SiB2.5GLOBAL CHANGE BIOLOGY, Issue 9 2003Ian Baker Abstract Three years of meteorological data collected at the WLEF-TV tower were used to drive a revised version of the Simple Biosphere (SiB 2.5) Model. Physiological properties and vegetation phenology were specified from satellite imagery. Simulated fluxes of heat, moisture, and carbon were compared to eddy covariance measurements taken onsite as a means of evaluating model performance on diurnal, synoptic, seasonal, and interannual time scales. The model was very successful in simulating variations of latent heat flux when compared to observations, slightly less so in the simulation of sensible heat flux. The model overestimated peak values of sensible heat flux on both monthly and diurnal scales. There was evidence that the differences between observed and simulated fluxes might be linked to wetlands near the WLEF tower, which were not present in the SiB simulation. The model overestimated the magnitude of the net ecosystem exchange of CO2 in both summer and winter. Mid-day maximum assimilation was well represented by the model, but late afternoon simulations showed excessive carbon uptake due to misrepresentation of within-canopy shading in the model. Interannual variability was not well simulated because only a single year of satellite imagery was used to parameterize the model. [source] Magnetic Resonance Sounding: New Method for Ground Water AssessmentGROUND WATER, Issue 2 2004M. Lubczynski The advantage of magnetic resonance sounding (MRS) as compared to other classical geophysical methods is in its water selective approach and reduced ambiguity in determination of subsurface free water content and hydraulic properties of the media due to the nuclear magnetic resonance (NMR) principle applied. Two case examples are used to explain how hydrogeological parameters are obtained from an MRS survey. The first case example in Delft (the Netherlands) is a multiaquifer system characterized by large signal to noise ratio (S/N = 73), with a 24 m thick, shallow sand aquifer, confined by a 15 m thick clay layer. For the shallow aquifer, a very good match between MRS and borehole data was obtained with regard to effective porosity nc,28% and specific drainage Sd,20%. The MRS interpretation at the level deeper than 39 m was disturbed by signal attenuation in the low resistivity (,10 ,m) media. The second case of Serowe (Botswana) shows a fractured sandstone aquifer where hydrogeological parameters are well defined at depth >74 m below ground surface despite quite a low S/N = 0.9 ratio, thanks to the negligible signal attenuation in the resistive environment. Finally, capabilities and limitations of the MRS technology are reviewed and discussed. MRS can contribute to subsurface hydrostratigraphy description, hydrogeological system parameterization, and improvement of well siting. The main limitations are survey dependence upon the value of the S/N ratio, signal attenuation in electrically conductive environments, nonuniformity of magnetic field, and some instrumental limitations. At locations sufficiently resistive to disregard the signal attenuation problems, the MRS S/N ratio determines how successfully MRS data can be acquired. Both signal and noise vary spatially; therefore, world scale maps providing guidelines on spatial variability of signal and noise are presented and their importance with respect to the MRS survey results is discussed. The noise varies also temporally; therefore, its diurnal and seasonal variability impact upon the MRS survey is covered as well. [source] Modelling snowpack surface temperature in the Canadian Prairies using simplified heat flow modelsHYDROLOGICAL PROCESSES, Issue 18 2005Purushottam Raj Singh Abstract Three practical schemes for computing the snow surface temperature Ts, i.e. the force,restore method (FRM), the surface conductance method (SCM), and the Kondo and Yamazaki method (KYM), were assessed with respect to Ts retrieved from cloud-free, NOAA-AVHRR satellite data for three land-cover types of the Paddle River basin of central Alberta. In terms of R2, the mean Ts, the t -test and F -test, the FRM generally simulated more accurate Ts than the SCM and KYM. The bias in simulated Ts is usually within several degrees Celsius of the NOAA-AVHRR Ts for both the calibration and validation periods, but larger errors are encountered occasionally, especially when Ts is substantially above 0 °C. Results show that the simulated Ts of the FRM is more consistent than that of the SCM, which in turn was more consistent than that of the KYM. This is partly because the FRM considers two aspects of heat conduction into snow, a stationary-mean diurnal (sinusoidal) temperature variation at the surface coupled to a near steady-state ground heat flux, whereas the SCM assumes a near steady-state, simple heat conduction, and other simplifying assumptions, and the KYM does not balance the snowpack heat fluxes by assuming the snowpack having a vertical temperature profile that is linear. Copyright © 2005 John Wiley & Sons, Ltd. [source] Hourly and daily clearness index and diffuse fraction at a tropical station, Ile-Ife, NigeriaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 8 2009E. C. Okogbue Abstract Dataset consisting of hourly global and diffuse solar radiation measured over the period February 1992 and December 2002 have been utilized to investigate the diurnal and seasonal variations of hourly and daily clearness index together with the diffuse fraction at a tropical station Ile-Ife (7.5°N, 4.57°E), Nigeria. Statistical analysis (the frequency and cumulative frequency distribution of the hourly and daily clearness index) and subsequent characterization of the sky conditions over the station based on these were also done, and their implications for solar energy utilization in the area discussed. Daytime (11:00,15:00 LST) monthly mean hourly diffuse fraction, M,d (explained in a separate ,List of Symbols' provided, along with other symbols used in this article), have values, which are most of the time less than 0.52, 0.54 and 0.60 respectively for January, February and March in the dry season. However, during the months of July and August (which are typical of the wet season), the values range between 0.61 and 0.85 (being generally greater than 0.65) with the corresponding values of the monthly mean hourly clearness index, M,T, ranging between 0.23 and 0.45. Statistical analysis of hourly and daily clearness index showed that the local sky conditions at the station were almost devoid of clear skies and overcast skies (clear skies and overcast skies occurred for only about 3.5% and 4.8% of the time respectively). The sky conditions were rather predominantly cloudy (cloudy skies occurred for about 88% of the time) all the year round. Copyright © 2009 Royal Meteorological Society [source] Evaluation of Usefulness of Daily Mean Temperature Studies on Impact of Climate ChangeJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2005S. Chauhan Abstract The impact of global warming on rise in temperature in different regions has often been expressed as a change in mean temperature (Tmean). The recent results suggest that this change could be both in diurnal and interannual temperatures. Therefore it is important to assess the impact of diurnal variation with the same mean temperature on crop plants for understanding the impact of climate change on agriculture, and also assess the possibility of genetic variation in adaptation. The present study in wheat (Triticum aestivum) varieties examines the effect of varying Tmax and Tmin, while maintaining the same mean temperature on phenology, growth and productivity. The mean temperatures examined are 18 °C with Tmax/Tmin combination of 18/18, 20/16, 22/14 and 24/12 °C. These wheat varieties differed considerably in their response to varying Tmax and Tmin with respect to days to ear emergence, anthesis, biomass accumulation and grain yield. The wheat variety HD2329, a popular Mexican dwarf high yielding cultivar showed maximum adaptation in the temperature combinations examined. The results suggest the need to refine the crop ideotypes in the context of the changing global scenario. This may require detailed experimental studies on various phenological phases. Such studies would help in assessing genotypes which may be having adaptation and thus identify the potential donors for further improvement of crops. [source] Body mass change strategies in blackbirds Turdus merula: the starvation,predation risk trade-offJOURNAL OF ANIMAL ECOLOGY, Issue 2 2005R. MACLEOD Summary 1It is theoretically well established that body mass in birds is the consequence of a trade-off between starvation risk and predation risk. There are, however, no studies of mass variation from sufficiently large wild populations to model in detail the range of diurnal and seasonal mass change patterns in natural populations and how these are linked to the complex environmental and biological variables that may affect the trade-off. 2This study used data on 17 000 individual blackbirds Turdus merula to model how mass changes diurnally and seasonally over the whole year and over a wide geographical area. Mass change was modelled in respect of temperature, rainfall, day length, geographical location, time of day and time of year and the results show how these mass changes vary with individual size, age and sex. 3The hypothesis that seasonal mass is optimized over the year and changes in line with predictors of foraging uncertainty was tested. As theory predicts, reduced day length and reduced temperature result in increased mass and the expected seasonal peak of mass in midwinter. 4The hypothesis that diurnal mass gain is optimized in terms of starvation,predation risk trade-off theory was also tested. The results provide the first empirical evidence for intraspecies seasonal changes in diurnal mass gain patterns. These changes are consistent with shifts in the relative importance of starvation risk and predation risk and with the theory of mass-dependent predation risk. 5In winter most mass was gained in the morning, consistent with reducing starvation risk. In contrast, during the August,November non-breeding period a bimodal pattern of mass gain, with increases just after dawn and before dusk, was adopted and the majority of mass gain occurred at the end of the day consistent with reducing mass-dependent predation risk. The bimodal diurnal mass gain pattern described here is the first evidence that bird species in the wild gain mass in this theoretically predicted pattern. [source] A quantitative study of day,night changes in the spatial distribution of insects in a stony streamJOURNAL OF ANIMAL ECOLOGY, Issue 1 2002J. M. Elliott Summary 1As many invertebrates are nocturnal, their spatial distribution may change from day to night. This behavioural aspect of their population dynamics has been ignored, but is now examined for the first time by testing the hypotheses: (i) a power function was a suitable model for the spatial distribution of common species of Ephemeroptera, Plecoptera and Trichoptera in a stony stream; (ii) the spatial distribution varied between species but was similar within species for larvae greater and smaller than half-size; (iii) diurnal and nocturnal spatial distributions were significantly different for each species. To ensure that the conclusions were consistent, large samples (n = 30) were taken near midday and midnight in April, June and November over 4 years. 2Twenty,one species were taken in sufficient numbers for the analyses; seven species were too sparse to be included. The first hypothesis was supported. A power function, relating spatial variance (s2) to mean (m), was an excellent fit in all the analyses (P < 0·001, r2 > 0·95), i.e. the spatial variance was density,dependent. The power b, often used as an ,index of aggregation', varied in the range 0·88,2·50. 3Most analyses supported the second hypothesis. For four species, the difference between the two size groups was just significant (P < 0·05), but was due to inadequate data for three species. Large larvae of the fourth species, the caddis Odontocerum albicorne, were less aggregated than small larvae at night, and were the only group with a b -value less than one. 4The third hypothesis was partially supported. The distribution did not change significantly (P > 0·05) for nine species; five burrowers in gravel, moss or mud, two highly mobile predators, one sedentary, case,building, Trichoptera species, and one net,spinning Trichoptera species. Aggregation was reduced significantly (P < 0·001) at night for four species, all case,building Trichoptera larvae. Aggregation increased significantly (P < 0·001) at night, except at low densities, for the remaining eight species, one being a nocturnal predator and the others being herbivorous species; all occurred frequently in night samples of invertebrate drift. Day,night changes in spatial distribution were therefore an essential part of the behavioural dynamics of 12 of the 21 species, and should be investigated in other species, including terrestrial species. [source] Estimates of blue duiker (Cephalophus monticola) densities from diurnal and nocturnal line transects in the Korup region, south-western CameroonAFRICAN JOURNAL OF ECOLOGY, Issue 2 2006Matthias Waltert No abstract is available for this article. [source] Spatial and temporal patterns in Lemniscomys striatus (Linnaeus 1758) as revealed by radio-trackingAFRICAN JOURNAL OF ECOLOGY, Issue 4 2001Anke Hoffmann Abstract Lemniscomys striatus was radio-tracked in the Imperata - Cymbopogon grassland of the Queen Elizabeth National Park in Uganda. Home range sizes calculated by Ranges V® using the minimum convex Polygon method (at 95%) in the postburnt grassland were on average 4.8 times larger than those before the fire. An inverse relation between home range size and population density was found. Lemniscomys striatus was diurnal with two activity peaks during daylight, but activity ended only after dusk. Résumé On a étudiéLemniscomys striatus par radio-tracking dans la prairie àImperata-Cymbopogon du Parc National Queen Elizabeth, en Ouganda. La taille des territoires calculées par Ranges V® en utilisant la méthode du polygone convexe minimum (à 95%) dans la prairie après les feux, était en moyenne 4,8 fois plus grande que celles d',avant les feux. On a découvert une relation inverse entre la taille du territoire et la densité de population. Lemniscomys striatus est diurne, avec deux pics d'activité pendant la journée, mais son activité ne cesse qu',après le crépuscule. [source] Hermit crabs, humans and Mozambique mangrovesAFRICAN JOURNAL OF ECOLOGY, Issue 3 2001David K. A. Barnes Abstract There is a complex interrelationship between upper shore hermit crabs (such as Coenobita sp. and Clibanarius sp.), coastal human populations and mangrove forests in Mozambique. The abundance, activity, shell selection and behaviour of three species of hermit crab are related to the level of mangrove cover. With increased density of mangrove trees, the study species of hermit crab changed in abundance, tended to become diurnal, spent more time feeding and were clustered in larger groups when doing so, and selected longer spired shells. All five of the same variables are also linked to the proximity and activity of humans through both direct and indirect actions. Direct effects included a tendency to nocturnal activity with proximity to human activity; indirect effects included increased and more clumped food supplies, and shell middens from intertidal harvesting and deforestation. Mangroves are important to local human populations as well as to hermit crabs, for a wide variety of (similar) reasons. Mangroves provide storm shelter, fisheries and fishery nursery grounds for adjacent human settlements, but they also harbour mosquito populations and their removal provides valuable building materials and fuel. Hermit crabs may be useful (indirectly) to coastal human populations by being a source of food to certain commercial species, and by quickly consuming rotting/discarded food and faeces (thereby reducing disease and pests). They can also cause minor problems to coastal human populations because they use shells of (fisheries) target mollusc species and can be more abundant than the living molluscs, thereby slowing down effective hand collection through confusion over identification. The mixture of positive and negative attributes that the three groups impart to each other in the Quirimba Archipelago, northern Mozambique, is discussed. Résumé Il existe des interrelations complexes entre les Bernard-l'Ermite du haut littoral (tels que Coenobita sp. Et Clibanarius sp.), les populations humaines côtières et les forêts de mangroves au Mozambique. L'abondance, l'activité, le choix de la coquille et le comportement de trois espèces de Bernard-l'Ermite sont liés au degré de couverture de la mangrove. Lorsque la densité des arbres de la mangrove augmente, l'abondance des espèces étudiées de Bernard-l'Ermite change, ils ont tendance à devenir diurnes, passent plus de temps à se nourrir et se rassemblent à ces moments-là en plus grands groupes, et ils choisissent aussi de plus longues coquilles. Les cinq mêmes variables sont aussi liées à la proximité et à l'activité des hommes, directement et indirectement. Parmi les effets directs, on compte une tendance à une activité nocturne lorsque les activités humaines sont proches ; les effets indirects incluent des apports de nourriture et de débris de coquilles accrus et plus regroupés résultant des marées et de la déforestation. Les mangroves sont aussi importantes pour les populations locales que pour les Bernard-l'Ermite, pour toute une série de raisons (semblables). Les mangroves constituent un abri en cas de tempête, un terrain de pêche et de frai dont bénéficient les populations humaines voisines, mais elles renferment aussi beaucoup de moustiques, et leur bois fournit un bon matériau de construction et du combustible. Les Bernard-l'Ermite peuvent être (indirectement) utiles aux populations côtières car certaines espèces commerciales sont comestibles et que tous consomment rapidement les restes de nourriture en décomposition et les excréments (réduisant ainsi les risques de maladie et d'animaux nuisibles). Ils peuvent aussi causer des problèmes mineurs aux populations côtières parce qu'ils utilisent la coquille d'espèces de mollusques qui font l'objet de la pêche et qu'ils peuvent être plus abondants que les mollusques eux-mêmes, ce qui ralentit la pêche manuelle à cause du besoin d'identification. On discute le mélange de qualités négatives et positives que les trois groupes représentent les uns pour les autres dans l'Archipel de Quirimba, au nord du Mozambique. [source] Pollinator shifts and the loss of style polymorphism in Narcissus papyraceus (Amaryllidaceae)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2010R. PÉREZ-BARRALES Abstract Darwin proposed that the driving force for the evolution of style polymorphisms is the promotion of cross-pollination between style morphs, through accurate placement of pollen on the pollinator's body. This hypothesis has received much attention, but the effect of different pollinators in the fitness of morphs remains poorly understood. Narcissus papyraceus is a style dimorphic species (long -L- and short -S- styled) with isoplethic (1 : 1) and L-monomorphic populations, mainly visited by long-tongued (LT) nocturnal and short-tongued (ST) diurnal pollinators, respectively. We studied natural female fertility of morphs, and assessed the role of diurnal and nocturnal pollinators. We also quantified female fertility of the morphs in experimental populations with different morph ratio, exposed to predominately long- or short-tongued pollinators. We found that with LT pollinators, both morphs were successfully pollinated in all morph ratio conditions, suggesting that these insects could be involved in maintenance of the polymorphism, although other factors may also play a role. However, with ST pollinators, S-plants displayed less fertility than L-plants, and mating among L-plants was favoured, implying that the polymorphism is lost. These results underscore the role of pollinators on variations in style polymorphism. [source] Nest predators of Lance-tailed Manakins on Isla Boca Brava, PanamáJOURNAL OF FIELD ORNITHOLOGY, Issue 2 2009Jennifer L. Reidy ABSTRACT Nest predation is often the primary cause of nest failure for passerines. Despite this, little is known about predation rates and the nest predators of birds in the tropics. I used video cameras to monitor seven Lance-tailed Manakin (Chiroxiphia lanceolata) nests on Isla Boca Brava, Panamá. One nest fledged young and six nests failed due to predation. I recorded five predation events involving four avian predators and one mammalian predator. Crested Oropendolas (Psarocolius decumanus) predated two nests and a Roadside Hawk (Buteo magnirostris) and a Black-chested Jay (Cyanocorax affinis) each predated one. The mammalian predator was a common opossum (Didelphis marsupialis). All avian predation was diurnal; the mammalian predation was nocturnal. My results suggest that tropical birds are subject to a diverse suite of nest predators, and that avian predators may be an important cause of nest failure at my study site. RESUMEN La depredación de nidos es usualmente la primera causa del fracaso de lo nidos de los paserinos. A pesar de esto, poco se conoce sobre la tasa de depredación y los depredadores de nidos de aves neotropicales. Yo use cámaras de video para monitorear siete nidos del Lance-tailed Manakins (Chiroxiphia lanceolata) en la isla Boca brava, Panamá. De un nido salieron polluelos y seis nidos fracasaron debido a la depredación. Yo documente cinco eventos de depredación de los cuales cuatro fueron por aves y uno por mamíferos. Crested Oropendolas (Psarocolius decumanus) depredo dos nidos y Roadside Hawk (Buteo magnirostris) y el Black-chested Jay (Cyanocorax affinis) depredaron uno cada uno. El depredador mamífero fue un marsupial común (Didelphis marsupialis). Todas las depredaciones de aves fueron diurnas y la del mamífero fue nocturna. Mis resultados sugieren que las aves neotropicales están sujetas a una diversa gama de depredadores de nidos y posiblemente la depredación por aves puede ser una causa importante del fracaso de las nidadas en mi lugar de estudio. [source] Validating the use of temperature data loggers to measure survival of songbird nestsJOURNAL OF FIELD ORNITHOLOGY, Issue 4 2006Karel Weidinger ABSTRACT Accurate determination of nest fates and nest predators is possible through continuous video monitoring, but such monitoring is relatively expensive and labor intensive. If documenting of the timing of nest termination events is sufficient, then data loggers (DL) may allow more extensive sampling and may represent a viable alternative. I validated temperature DL records of nest survival time by simultaneous videotaping and compared results derived from DL records with those obtained by regular nest visits by an observer. I estimated the fate of 937 nests of nine species of open cup-nesting songbirds, including 673 nests monitored using DL, 165 monitored using video cameras, 33 validation nests monitored simultaneously using both DL and video cameras, and 132 control nests monitored only by observer visits. Deployment of DL did not negatively influence nest survival rate. DL reliably recorded survival time and allowed classification of nest fates based on the potential fledging age, regardless of the frequency of nest visits by an observer. The true fate of nests that survived beyond the potential fledging age can not be safely determined from time of failure, except for nocturnal events that suggest partial predation. Video revealed frequent partial or complete predation on nests with old nestlings that would have been categorized as successful by other methods. I conclude that temperature DL are efficient, reliable, and relatively inexpensive tools for recording exact nest survival times and classification of nest fates, with implications for nest survival modeling and discriminating between diurnal and nocturnal predation. SINOPSIS Es posible determinar con precisión la sobrevicencia en nidos y la depredación en estos mediante el uso de videos contínuos. Pero dicho monitoreo es relativamente costoso y requiere mucho trabajo. Si el documentar el momento en que se termina el anidamiento es suficiente para obtener la información, previamente mencionada, el uso de bitácoras electrónicas de temperatura (loggers) pudieran permitir el tomar muestras más amplias y por ende, representar una alternativa viable. Validé la toma de temperaturas con bitácoras electrónicas para determinar la sobrevivencia en nidos con la toma simultánea de videos y comparé los resultados obtenidos (con la bitácora) con los datos tomados por un observador que visitó regularmente los nidos. El estudio se hizo con 937 nidos de nueve especies de aves canoras cuyo nido es en forma de copa. De estos 673 se monitorearon utilizando bitácoras electrónicas de temperatura, 165 con cámaras de video, 33 con monitoreo simultáneo de bitacora y video y 132, como control, monitoreados mediante observación directa. El uso de las bitácoras no influyó negativamente en la tasa de sobrevivencia. La bitácora grabó el tiempo de sobrervivencia y permitió la clasificación de los nidos (exitoso o no exitoso) basado en el tiempo potencial de la edad de dejar el nido, sin importar la frecuencia de visita a los nidos por parte de observadores. La verdadera finalidad de los nidos que sobreviven, más alla de la edad potencial de dejar el nido los pichones, no puede ser determinado con exactitud, excepto en eventos nocturnos que surgieren depredación. El uso de videos permitió determinar la depredación parcial o completa en nidos, particularmente de pichones que se tardaron más que el tiempo promedio en dejar el nido y que en estudios se asume que sobrevivieron. Puedo concluir que las bitácoras electrónicas de temperatura son eficientes, confiables, de bajo costo y permiten determinar con precisión la sobrevivencia en nidos y la clasificación de estos entre exitosos y no exitosos, con implicaciones para construir modelos de sobrevivencia y discriminar entre depredores diurnos y nocturnos. [source] Characteristics of egg and larval production in captive bluespotted gobiesJOURNAL OF FISH BIOLOGY, Issue 5 2001L. A. Privitera Spawning of the Hawaiian coral-reef goby Asterropteryx semipunctata was diurnal, occurring at various times throughout the day. Mean length of eggs deposited in nests was 0·76 mm (range 0·67,0·84); mean egg width was 0·47 mm (range 0·41,0·52). Clutch size varied from 296 to 1552 eggs (mean=886±309), and was independent of standard length, total body weight, and body condition. Mean relative clutch size was 1·59 eggs mg -1 total body weight (range 0·84,2·43). Clutches hatched 4,5 nights after being deposited in a nest. Mean notochord length of newly-hatched larvae was 1·88 mm (range 1·60,2·04). The minimum period of time that elapsed between egg deposition and subsequent growth of a new batch of oocytes to spawning size was 5,6 days, providing a reasonable estimate of minimum spawning interval. Compared with other gobiids, tropical species tend to have shorter incubation periods, smaller eggs and smaller larvae at hatching. [source] | ||||||||||||||||||||||||||||||||||||||||||||||