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1.
The life history of the freshwater shrimp Palaemonetes antennarius (H. Milne Edwards, 1837) was investigated from April 1993 to November 2002 at 13 sites in the delta of the Neretva River, Croatia. The sex ratio (males vs. females) was in favour of females throughout the study year . The breeding period lasts from April to August with a peak of 75% of the ovigerous female in June. The maximum number of eggs carried by ovigerous females was 73, and there was a positive significant linear correlation between fecundity (number of early embryonic stage eggs per female) and female body size (carapace length) (R2=0.698, p<0.01). The breeding period was longer in limnocrenes and lakes with oligohaline-limnic water than in other habitat types because the water is more rapidly warmed in spring and cooled more slowly in autumn in these habitats. Larvae were present from June to October, with a peak reaching 19.4% of the total population in June. The shrimps follow a synchronic univoltine life cycle with a short egg-laying period and a new summer generation. Their larvae, apparently having no ecological flexibility, did not appear in any environment with high oscillations of salinity. 相似文献
2.
The variability of the respiratory surface area of Simulium monticola Friederichs, 1920 and Simulium argyreatum Meigen, 1838 pupae was studied in detail. 333 pupae from Western Carpathian Mts. were investigated. According to the tubercles on thorax and head of the pupa of S. monticola, two morphological forms were distinguished (S. monticola 1 and S. monticola 2). Both were studied separately. In any species or form respectively we measured the lengths of all respiratory filaments and basal trunks, the widths of the basal trunks, the widths of the filaments on their proximal and distal end and the widths 0.25 mm from the proximal end. In all species (forms) differences in the size of the respiratory surface area between the first (April – June) and the second generation (August – October) were found. In S. monticola 1 the mean real respiratory surface area was significantly (p < 0.001) larger in spring (3.67 mm2) than in summer (2.19 mm2). In S. monticola 2 the mean real respiratory surface area was 3.45 mm2 in spring, and it was significantly larger in females than in males (p = 0.034). In S. argyreatum the mean real respiratory surface area was 2.80 mm2 in spring 2001 while in different summer generations it was significantly smaller: 1.58 mm2 in 1999, 1.84 mm2 in 2000 and 2.12 mm2 in 2001. All these groups differed significantly from each other. Regression models could explain 64.5% (power model) of the real respiratory surface area in S. monticola 1 and 19.9% (various models) of the real respiratory surface area in S. argyreatum due to the variability of the adult size. 相似文献
3.
The life history of the amphipod Orchestia sp. cf. cavimana (Heller, 1865) was studied throughout the course of a year with monthly samplings and the use of pitfall traps along the shores of Lake Albano in central Italy. The data thus obtained showed two peaks in abundance (the first in June and the second in October) and a minimum capture frequency in February. Egg-bearing females were recorded in spring and late summer, whilst recruitment occurred from spring to autumn, with maximum in June and October. The data collected also indicated the presence of a positive correlation between the abundance of talitrids and both temperature and sediment moisture. Morphological analysis enabled the identification of four different cohorts (with a lifespan of the species of approximately 12–15 months) all four of which remained distinguishable throughout the course of the year. It, moreover, enabled sex determination in individuals of 5 or more millimetres. The subsequent distribution indicated that, when significant, the sex ratio was female biased and that maximum size was greater in males. In particular, maximum sizes were recorded in spring for both males and females and were of 17.5 and 13.0 mm, respectively. Furthermore, the total body length recorded for egg-bearing females was positively correlated with the number of eggs in their brood pouch. 相似文献
4.
An Aphanomyces sp. (Oomycetes) was found to be an important egg parasite of Eudiaptomus gracilis (Copepoda) in Lake Mondsee (Austria). The infection is evidenced by densely packed infection hyphae, attached with holdfasts and wrapped around the female's abdomen. The infection hyphae give rise to hyphae which penetrate the egg sac, and subsequently kill all eggs. The infection obviously has no pathogenetic effects on the egg-carrying female. Infected females appear during summer and fall, mainly in warm water layers. Infected egg clutches are found at all seasons of the year, indicating considerable birth control of the Eudiaptomus population by parasite infection. It seems possible that the actual Aphanomyces sp. is not the only parasite involved. 相似文献
5.
《Limnologica》2019
Atyoida serrata is a small amphidromous shrimp distributed in the south-west Indian Ocean. This species is threatened by human activities such as fisheries and river discharge withdrawals. Knowledge of its reproductive biology is essential to develop management plans and reduce the impacts of these threats. This study presents the results of a one-year survey in three stations along the Langevin River, Reunion Island. Densities of shrimps dominated by juveniles decreased with an increasing altitude. However, the largest individuals were more numerous upstream. Despite variable size structures among stations, all the largest individuals were females. Females larger than 32 mm Total Length had a probability of 50% or more of being ovigerous. Fecundities were ranged from 271 eggs for a 28 mm TL female to 4,365 eggs for a 47 mm TL female. Reproductive activity was observed throughout the year with a considerable increase from September to April. This increase was positively correlated to day-lengths and to a lesser extent to elevated water temperatures and river discharges. This study suggests a fishing restriction in the upstream areas and during the reproductive season. Attention should be paid to management of water withdrawal during low water levels to reduce impacts on the larva drift. 相似文献
6.
Marina Manca Patrizia Comoli Teresa Spagnuolo 《Aquatic Sciences - Research Across Boundaries》1997,59(1):48-56
We compared three methods for calculating the standing stock biomass ofDaphnia hyalina galeata population in Lago Maggiore during a single year. We applied body length/carbon regression equations (LCR) obtained under
controlled laboratory conditions and directly from field data on carbon and body length to field data on length-specific abundance.
Laboratory-derived equations satisfactorily described our field estimates of length-specific carbon content in spring. As
the length-standardized carbon content decreased exponentially along the season, we included time of the year as an auxiliary
variable, and tested whether it affected slope, intercept or both. The decrease had no effect on slope but reduced the intercept
of the LCR. We also calculated biomass, using a single mean value from the literature. By comparing the results with those
obtained by simple conversion of individuals number into carbon we might discriminate between the effect of changes in the
size frequency distribution of the population and the decrease with time of the length-standardized carbon content. Although
we tested the different models for non-ovigerous females, the results did not change when we included also data on females
with eggs in the first three developmental stages, whereas they changed substantially when we included females with embryos.
We formulate two hypotheses to explain this result and discuss possible implications for the calculation of the standing stock
biomass ofDaphnia population. 相似文献
7.
Rotifers are one of the smallest metazoans, served as perfect material for evolution theories and excellent food resources to larva in aquaculture. Population dynamics of rotifers help to optimize culture conditions, and to understand selection of asexual and sexual reproduction types. We described population dynamics of three Brachionus angularis strains using the life table method, with three types of food. The following demographic parameters were analyzed: intrinsic rate of increase (r), net reproductive rate (R0), generation time (T), average lifespan (L), and the total percentage of mictic females in the offspring. The results showed that there were significant effects of strain on the parameters except for R0. However, the food type significantly affected r, R0, T, and the total percentage of mictic females in the offspring. Demographic parameters differed among strains, showing the possible adaptation to local niches. In comparison to Chlorella pyrenoidosa, Scenedesmus obliquus served more nutrition to enlarge population size, and more mixis was induced in rotifer populations fed on it. 相似文献
8.
探究鱼类繁殖策略是了解鱼类种群动态的关键.通过对珠江西江流域重要的经济鱼类广东鲂(Megalobrama terminalis)生殖周期、产卵时间、成熟期长度、生殖力类型和生殖力等方面进行研究,阐明在人类活动日益加强下,西江广东鲂的繁殖策略适应性变化情况.研究表明,广东鲂个体平均体长245 mm,优势体长集中在260~280 mm,平均体重347 g,优势体重集中在320~480 g.用L 50逻辑斯谛回归方法推算广东鲂雌鱼和雄鱼初次性成熟体长分别为244.5和232.2 mm.雌雄性比例为1.105∶1,且随着体长增加,雌雄性比呈现出先下降后上升的变化趋势.广东鲂繁殖群体在产卵季节为48月,产卵高峰为6月初持续到7月上旬,产卵季节内广东鲂鱼苗的密度与径流量显著相关.广东鲂绝对繁殖力平均为73069粒,相对繁殖力平均为118.7粒/g,绝对繁殖力与体长和体重均呈正相关.广东鲂繁殖群体性腺成熟系数与性腺重、肥满度以及体重密切相关.广东鲂种群繁殖策略在人类活动加剧影响下呈现出适应性变化:初次性成熟体长变小,绝对繁殖力下降. 相似文献
9.
2011—2020年,三峡水库共开展了14次促进坝下江段四大家鱼自然繁殖的生态调度试验,于每年5—7月在长江中游沙市江段开展鱼类早期资源调查研究,旨在掌握生态调度实施以来产漂流性卵鱼类自然繁殖的响应变化,评估生态调度对长江中游鱼类自然繁殖的贡献。十年间共采集到鱼卵35种,其中典型产漂流性卵鱼类有25种,主要种类包括贝氏?(Hemiculter bleekeri)、鯿(Parabraims pekinensis、银鮈(Squalidus argentatus)、草鱼(Ctenopharyngodon idellus)、鲢(Hypophthalmichthys molitrix)、翘嘴鲌(Culter alburnus)和花斑副沙鳅(Parabotia fasciata);鱼卵群落多样性指数H、均匀度指数E和稳定性指数ICV在年际间呈现先降低后升高的变化趋势,优势度指数D恰好相反,变化拐点出现在2017年,表明2017年以来群落多样性趋于增加,群落结构趋于稳定;产漂流性卵鱼类繁殖规模总体呈先减少后增加变化,有8个类群的繁殖规模逐年增加,鱼类繁殖高峰频次逐渐升高,大规模繁殖出现的时段逐渐延长... 相似文献
10.
Phytoplankton biomass size structure and its regulation in the Southern Yellow Sea (China): Seasonal variability 总被引：7，自引：0，他引：7
Mingzhu Fu Zongling Wang Yan Li Ruixiang Li Ping Sun Xiuhua Wei Xuezheng Lin Jingsong Guo 《Continental Shelf Research》2009,29(18):2178-2194
Phytoplankton size structure plays a significant role in controlling the carbon flux of marine pelagic ecosystems. The mesoscale distribution and seasonal variation of total and size-fractionated phytoplankton biomass in surface waters, as measured by chlorophyll a (Chl a), was studied in the Southern Yellow Sea using data from four cruises during 2006–2007. The distribution of Chl a showed a high degree of spatial and temporal variation in the study area. Chl a concentrations were relatively high in the summer and autumn, with a mean of 1.42 and 1.27 mg m−3, respectively. Conversely, in the winter and spring, the average Chl a levels were only 0.98 and 0.99 mg m−3. Total Chl a showed a clear decreasing gradient from coastal areas to the open sea in the summer, autumn and winter cruises. Patches of high Chl a were observed in the central part of the Southern Yellow Sea in the spring due to the onset of the phytoplankton bloom. The eutrophic coastal waters contributed at least 68% of the total phytoplankton biomass in the surface layer. Picophytoplankton showed a consistent and absolute dominance in the central region of the Southern Yellow Sea (>40%) in all of the cruises, while the proportion of microphytoplankton was the highest in coastal waters. The relative proportions of pico- and nanophytoplankton decreased with total biomass, whereas the proportion of the micro-fraction increased with total biomass. Relationships between phytoplankton biomass and environmental factors were also analysed. The results showed that the onset of the spring bloom was highly dependent on water column stability. Phytoplankton growth was limited by nutrient availability in the summer due to the strong thermocline. The combined effects of P-limitation and vertical mixing in the autumn restrained the further increase of phytoplankton biomass in the surface layer. The low phytoplankton biomass in winter was caused by vertical dispersion due to intense mixing. Compared with the availability of nutrients, temperature did not seem to cause direct effects on phytoplankton biomass and its size structure. Although interactions of many different environmental factors affected phytoplankton distributions, hydrodynamic conditions seemed to be the dominant factor. Phytoplankton size structure was determined mainly by the size-differential capacity in acquiring resource. Short time scale events, such as the spring bloom and the extension of Yangtze River plume, can have substantial influences, both on the total Chl a concentration and on the size structure of the phytoplankton. 相似文献
11.
Gabi Müller 《Aquatic Sciences - Research Across Boundaries》1995,57(2):119-126
The influence of parasites on the breeding biology of the European minnow (Phoxinus phoxinus) was studied by examining 268 adult and 59 young-of-the-year minnows from an artificial Swiss Alpine lake for parasites during the breeding seasons in 1990 and 1991. Two trematode parasites;Diplostomum phoxini, in their brains, andMacrolecithus papilliger, in their guts, were found. The prevalence ofD. phoxini was 100% in both years. The mean abundance was 231 in 1990 and 448 in 1991; the difference was significant. Prevalence (and abundance) ofM. papilliger was 37.5% (1.04±0.39) in 1990 and 59.5% (2.68±0.55) in 1991; also significantly higher in 1991 than in 1990. No differences in prevalence or abundance between males and females were found. Numbers of both parasites were significantly correlated with fish length. There was seasonal variation in the abundance ofD. phoxini metacercariae, with a peak in June/July in both years. The prevalence ofM. papiller decreased after July in both years. Distribution of the two trematodes was overdispersed as indicated by the variance to mean (abundance) ratio. The observed seasonal variation inD. phoxini abundance also suggests that sublethal parasites could influence the population dynamics of their hosts. 相似文献
12.
Groundwater provides an important source of water for maize cultivation where the water table is shallow in the semi-arid Hailiutu River catchment of the Maowusu Desert on the Erdos Plateau in Northwest China. A HYDRUS-1D model of the unsaturated flow beneath a maize (Zea mays L.) field was calibrated and validated with measured soil water contents at various depths during the maize growing period from 30 April to 1 October 2011, and from 23 May to 27 September 2012, respectively. The model computed the actual maize evapotranspiration (ETa) as 580 mm during the whole growing period from 30 April to 1 October 2011. The groundwater contribution to ETa was calculated to be 220 mm, accounting for 38% of maize water use during the growing season in 2011. When the groundwater level drops below a depth of 157 cm, maize can no longer use groundwater for transpiration. The irrigation water requirement increases with the increase of groundwater table depth. These results are very important for managing crop irrigation in the area.
EDITOR D. KoutsoyiannisASSOCIATE EDITOR L. Ruiz 相似文献
13.
Comparative study of morphometric measurements was undertaken on populations of Palaemonetes antennarius from two freshwater habitat zones (lacustrine pelagic and lacustrine littoral) and from the fluvial littoral habitat zone of three estuaries of north-western Greece. Multivariate statistical analyses (principal component analysis and discriminant function analysis) revealed clear morphometric differences between sexes and sampling sites. The observed differences are expressed mainly thought the measurements related to the body heights (carapace height and second pleon height), as a result of sexual dimorphism, High values for the female body heights seem to be correlated to specific fecundity profile and reproductive strategy. On the other hand, morphometrical variables related mainly to body lengths, such as rostral, telson and pleon lengths, were observed to be correlated to the study sites. Characters related to the summing capacity (telson length, telson width and pleon lengths) were generally found to have higher values in the specimens from habitats with high reophilic profile. 相似文献
14.
Differences in seasonality and temperature dependency of stand transpiration and canopy conductance between Japanese cypress (Hinoki) and Japanese cedar (Sugi) in a plantation 
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下载免费PDF全文 Takami Saito Tomo'omi Kumagai Makiko Tateishi Nakako Kobayashi Kyoichi Otsuki Thomas W. Giambelluca 《水文研究》2017,31(10):1952-1965
In this paper, we present an investigation of interspecies differences in transpiration of the 2 most common plantation forest tree species in Japan, both in the family Cupressaceae with different northern limits of native distribution, Japanese cypress (Hinoki; Chamaecyparis obtusa Sieb. et Zucc.) and Japanese cedar (Sugi; Cryptomeria japonica D. Don). The stem sap flow rate was measured in 2 nearby stands of similar leaf area index in a 42‐year‐old plantation. Single‐tree and stand‐scale transpiration rates (Etre and Esta, respectively) were observed during an ideal autumn environment. At the stand scale, mean sap flux density of Hinoki was greater than that of Sugi, whereas total sapwood area per ground area was smaller in Hinoki than Sugi. Because the 2 variables had counterbalancing effects on transpiration, Esta of Hinoki was similar to (94% of) that of Sugi. This offset was also found between the mean Etre of the 2 species. Esta was similar between the stands from May to October, whereas Esta of Sugi was notably greater than that of Hinoki from February to April. During these 3 months, the difference in cumulative Esta was 21.7 mm, which accounted for 79% of the difference in annual Esta between Hinoki and Sugi (192 and 219 mm/year, respectively). We found that canopy conductance (Gc) and its sensitivity to the mean vapour pressure deficit during daylight hours in Sugi were particularly high in early spring, whereas those in Hinoki shifted gradually throughout the growing season. This difference was related to the optimal temperature of Gc in Sugi, which was approximately 10 °C lower than that in Hinoki. Our results suggest that plantations of water‐conserving species such as Hinoki produce timber slowly but yield water resources generously. Moreover, for plantations of trees sensitive to high temperature, such as Sugi, managers should be concerned about possible future decline caused by anticipated global warming. 相似文献
15.
The dynamics of theCeratium hirundinella population and the abundance of dinocysts in the plankton and sediments were studied in Lake Sempach in 1988. In 1987, a rich population ofCeratium (380 cells ml–1) accompanied byPeridinium spp. developed in the lake. The dinocysts were found entrapped in a kind of flocs, in the deepest part of the lake, in the upper flocculent layer. The number of viable cysts ofCeratium in the sediments decreased gradually from April to July 1988. TheCeratium population increased slowly starting in April, and reached a maximum number in August (31 cells ml–1).Peridinium willei reached 100 cells ml–1. Newly formed cysts ofCeratium were recorded in the plankton and sediments at the end of July — beginning of August. They appear in the sediments as separate cells. Their number increased gradually, reaching a maximum of 600 cysts l–1 at the end of October.Ceratium formed more cysts than didPeridinium, but the rate of survival of theCeratium cysts appears to be lower than that ofPeridinium cysts. In addition to their biological functions, the cysts also have an impact on the ecosystem as carriers of nutrients from down to up and from up to down. 相似文献
16.
Water samples were collected from cold and warm karst springs for stable isotopes (δ18O and δD) and 3H from SE of Kashmir valley (western Himalayas) to distinguish the sources of recharge and infer their recharge areas. The spring water samples were most depleted in heavier isotopes in May (average δ18O: ?8.87‰ and δD: ?50.3‰) and enriched in September (average δ18O: ?7.58‰ and δD: ?48.1‰). The depleted 18O and 2H of spring waters bear the signatures of winter precipitation while as the enriched 18O and 2H of spring waters bear the signature of summer rainfall. D‐excess and 3H corroborate with the stable isotope results that the spring flow in spring season (May) and autumn (September) is dominantly controlled by the melting of winter snowmelt and summer rainfall, respectively. The results showed that unlike δD, the δ18O value in the karst spring waters decreases in January suggesting δ18O shift. The spring water samples also fall above the Local Meteoric Water Line and Global Meteoric Water Line indicating the δ18O shift due to interaction of groundwater with the host carbonate rocks during its traverse. The mean elevation of the recharge areas of the springs using δ18O and δD tracers was also estimated. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
17.
Copper is more toxic to all life stages of the copepod Tisbe than cadmium. The most sensitive life stage of Tisbe to both copper and cadmium is the one-day-old nauplius. The resistance of larval stages of Tisbe increases with age (one-day-old nauplii 48h mg Cu l?1. and 0.5384 mg Cd l?1, 0.3415 mg Cu l?1. and 0.645 mg Cd l?1. for five-days-old nauplii and 0.5289 mg Cu l?1. and 0.9061 mg Cd l?1. for ten-days-old nauplii. The two reproductive stages of Tisbe tested (females with ovigerous bands and females bearing the first ovigerous sac) demonstrated an increased sensitivity to metals and proved more sensitive than the ten-days-old copepodids (only females with ovigerous bands had a similar sensitivity to copper with the ten-days-old copepodids). 相似文献
18.
Species differences in stomatal control of water loss at the canopy scale in a mature bottomland deciduous forest 总被引：2，自引：0，他引：2
In order to evaluate factors controlling transpiration of six common eastern deciduous species in North America, a model describing responses of canopy stomatal conductance (GS) to net radiation (RN), vapor pressure deficit (D) and relative extractable soil water (REW) was parameterized from sap flux data. Sap flux was measured in 24 mature trees consisting of the species Carya tomentosa, Quercus alba, Q. rubra, Fraxinus americana, Liriodendron tulipifera, and Liquidambar styraciflua in a bottomland oak-hickory forest in the Duke Forest, NC. Species differences in model coefficients were found during the 1997 growing season. All species showed a reduction in GS with increasing D. RN influenced GS in the overstory shade intolerant L. styraciflua to a larger extent than the other species measured. In addition, despite a severe drought during the study period, only L. tulipifera showed a decline in GS with decreasing REW. The primary effect of the drought for the other species appeared to be early autumn leaf senescence and abscission. As a result, despite the drought in this bottomland forest accustomed to ample water supply, maximum daily transpiration (1.6 mm) and growing season transpiration (264 mm) were similar to a nearby upland forest measured during a year of above average precipitation. These results may aid in assessing differences in water use and the ability of bottomland deciduous species to tolerate alterations in the frequency or amount of precipitation. Results also suggest little variation in water use among forests of similar composition and structure growing in different positions in the landscape and subjected to large interannual variation in water supply. 相似文献
19.
The Ponto-Caspian mysid Limnomysis benedeni was first recorded in Lake Constance in summer 2006, and a stable population developed at the site of discovery. Although this mysid is common in the Rhine and Danube rivers, little is known about its ecology and impact in systems of invasion. We investigated the autecology of L. benedeni in habitat-choice and food experiments. In the habitat-choice experiments, highly structured habitats, i.e., stones covered with zebra mussels (Dreissena polymorpha), macrophytes, and especially stonewort, were strongly preferred. In food experiments, L. benedeni fed mostly on food sources with a small particle size, e.g., biofilm on leaf litter, biodeposited material of zebra mussels, epilithon, and phytoplankton. We also compared the L. benedeni population data from Lake Constance with that from rivers. In Lake Constance, female L. benedeni were nearly 30% larger and carried more than three times more eggs in spring (9.4±0.6 mm and 28.4±5.7 eggs) than in summer (6.7±0.8 mm and 8.7±2.9 eggs). The mysids present in spring might be the generation that over-wintered; in summer, this generation was probably replaced by a new generation of smaller individuals. The large brood size and the detritivorous feeding strategy might allow L. benedeni to colonize Lake Constance rapidly. 相似文献
20.
Miloš Buřič Antonín Kouba Pavel Kozák 《Aquatic Sciences - Research Across Boundaries》2009,71(4):473-477
Thirteen adult Orconectes limosus males (carapace length 32.5 ± 2.48 mm; weight 10.8 ± 2.63 g) were radio-tagged and tracked during and after the spring mating
period, April–June 2008. Average distances moved per day were higher in the mating period (14.9 ± 21.4 m) due to mate searching
activity. During the mating period, movement did not correlate with water temperature, and crayfish were active during daylight
hours. They moved rapidly upstream and downstream, a maximum 118 and 95 m per day, respectively. When water temperature increased
over 10°C, this initiated the end of mating and the start of spawning, and the spring migration abruptly ceased. An influence
of water temperature on movements was observed during the non-reproductive period. Orconectes limosus was highly mobile in small watercourses, signifying a threat of penetration into native crayfish habitats, and potentially
enabling the transmission of crayfish plague. This threat was increased during the mating period due to increased activity. 相似文献