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1.
The occurrence of eggs, pelagic larvae and juveniles, and settled juveniles of the dragonetRepomucenus valenciennei in Tokyo Bay, Japan, were investigated by plankton net and bottom trawl surveys between September 1990 and September 1991. Eggs, and pelagic larvae and juveniles appeared from April to November (spring to autumn), peaking in both spring and autumn. From the temporal pattern of egg and pelagic fish occurrence, and pelagic duration reported elsewhere (ca. one month), settlement could be predicted as occurring from late spring to autumn. However, settled juveniles appeared from August to December, with an abrupt peak in November. Aging from daily increments in the otoliths of settled recruits in 1990 indicated that the latter comprised individuals which had hatched between mid-September and early November (i.e. autumn cohort), implying that individuals which had hatched in spring to summer (April to August) were not recruited. Benthic hypoxia occurs widely in Tokyo Bay, from June to October each year, particularly in the northern part, which is the main nursery area ofR. valenciennei. The timing of dissolved oxygen recovery, and appearance of settled fish coincided closely (i.e. November), indicating that summer hypoxic conditions prevented the settlement of the spring cohort and hence recruitment to the population.  相似文献   

2.
M. M. Babiker 《Hydrobiologia》1986,135(1-2):71-79
Two annual breeding seasons are indicated for populations of T. nilotica in the White Nile: a major autumnal season (mid-July–September) coinciding with the annual rainfall and a smaller back-up season in February–March. During these seasons reproducing females constituted 80% and 40% of the total population of mature females compared to 10–12% in the intervening summer period. Enhanced gonadal development, fecundity and GSI values characterized the breeding seasons. Gonadal maturation proceeded uninterruptedly even during the summer and repeated fractional spawning is suggested for this species within and beyond the breeding seasons. Most of the spring breeders were either very young or relatively old fish and most medium-sized females bred in the main autumnal season. Older fish were less fecund (by 70–75%) compared to younger fish. In the latter, fecundity increased progressively with body growth (r2 = 0.732; p<0.001); the proportionality was lost in medium-sized fish and in older females (0.9–1.5 kg) fecundity correlated negatively with increased body size.  相似文献   

3.
We investigated seasonal changes in the density of epiphytic cladocerans Alona spp. (Chydoridae, Anomopoda) in two habitats, emergent and submerged aquatic plants, in Lake Suwa, Japan, from April to August 1998 and from April to November 2000. Alona had a density peak in early June on reeds (emergent) and in late June on Potamogeton malaianus (submerged). In summer, Alona density remained low in both habitats. Although density was positively correlated with the abundance of epiphytic algae, the birth rate was constant and no correlation between algal abundance and clutch size was detected. In a field experiment using ropes as an artificial substrate covered with high and low densities of epiphytic algae as food, more Alona attached to the ropes with the high density of algae. These results suggest that Alona may select food-rich habitats and migrate seasonally, and that migration is an important factor in the population dynamics of epiphytic chydorid cladocerans such as Alona. In Lake Suwa, Alona may migrate from the reed zone to the submerged macrophyte zone in June.  相似文献   

4.
The number, size and developmental stage of young in the brood pouch of female Tenagomysis tasmaniae, Anisomysis mixta australis and Paramesopodopsis rufa was recorded throughout the year. Breeding was intensive from spring till the end of autumn for the three species. Calculation of the egg ratio for each species showed that their major reproductive peaks occurred during spring and summer. A winter depression in the breeding cycle was observed for T. tasmaniae and P. rufa, but A. mixta australis ceased breeding during winter. Seasonal variation in the length of gravid females and number of young carried was evident for these three species. Females were longer in spring and summer and carried more young than in autumn and winter. A linear relationship between female length and brood size was demonstrated for each species; annual and seasonal equations were calculated for females carrying each developmental stage. The seasonal equations showed that for a female of given length fecundity was greater during spring than any other season. Natality was estimated to be highest during late spring, summer and early autumn for the three species. No seasonal variation in the size of eggs was evident for the three species. The reproduction pattern of T. tasmaniae, A. mixta australis and P. rufa appears to be very similar to that reported for the majority of iteroparous coastal temperate mysids throughout the world.  相似文献   

5.
The night monkeys (Aotus azarai) of Formosa, Argentina provide an opportunity to investigate the influences of ambient temperature and photoperiod on reproduction in a highly seasonal environment: the Chaco. Between 1997 and 2000, we collected data to evaluate the relationship between rainfall, ambient temperature, photoperiod and food availability and the annual distribution of mating behavior and births in 15 groups of monkeys in the forests of the Eastern Argentinean Chaco. Our data show that the area is highly seasonal, characterized by significant fluctuations in rainfall, temperature, photoperiod and food availability. There are two rain peaks in April and November and a dry season lasting from June to August. Monthly mean temperatures were on average 11°C lower during winter months than they were during summer months. Temperatures <10°C and >33°C were also frequent through the year. Days are 3 h longer during the summer than during the winter months. Insect abundance and the percentage of tree species producing fruits, flowers or new leaves reached a low in the coldest winter months. Mating was infrequent, and we only observed it between May and September. Half the births (n = 13) occurred during a 2-week period in October. Infant survival during the first 6 mo of life was high (96%). Our findings suggest an environmental control of reproduction. Changes in photoperiod and temperature may promote reproductive activity in females that might conceive and begin pregnancy at a time void of high temperatures that could be metabolically challenging.  相似文献   

6.
为了解茉莉花(Jasminum sambac)的内生菌多样性,利用16S rDNA高通量测序技术对其内生细菌组成进行测定。结果表明,茉莉花的内生细菌有38门78纲150目257科434属,其中变形菌门、放线菌门、壁厚菌门、拟杆菌门和绿弯菌门的物种丰度较高。变形菌门在6-10月的丰度均最高(70.3%~85.7%)。7月份植株的细菌Shannon指数最高(3.14)、Simpson指数最小(0.13),表明细菌群落多样性最高,且高温有利于提高植株内生细菌多样性。聚类和主成分分析表明,7和8月、9和10月的植株内生细菌群落构成相似度高,6月与其他月份的差异大。冗余分析和热图分析表明,土壤营养成分影响植株内生群落组成,以全氮、全磷和有机质含量为主要。这为挖掘利用茉莉花有益的内生菌资源奠定基础。  相似文献   

7.
Investigation of annual changes in phytoplankton community structure in a small artificial eutrophic pond was carried out from May 2002 to April 2003. A heavy bloom of Aphanizomenon flos-aquae var. klebahnii Elenk. (Cyanobacteria) persisted in most of the water column from June to the end of October. In November, the A. flos-aquae bloom suddenly crashed and green algae were predominant until the end of spring. Weekly monitoring suggested strong involvement of the changes in abiotic factors in the cyanobacterial bloom degradation. To clarify the effects of pH, water temperature, and day length on the growth of A. flos-aquae, laboratory batch experiments were conducted. The results showed that A. flos-aquae could not grow below pH 7.1 and 11°C, and the growth tended to be suppressed under a 10L:14D photoperiod. pH, water temperature, and day length are vital factors in the growth of A. flos-aquae and, additionally, grazing by cyclopoid copepods also seemed important in bloom collapse.  相似文献   

8.
The seasonal occurrence of Tetranychus kanzawai Kishida populations on hydrangea (Hydrangea macrophylla) was studied at two different localities in Ibaraki, Japan, during a three-year period. There were two types of seasonal population trends: one with a population peak from May to June, and the other with the spring peak in June and the autumn peak in September–October. Each year the populations on hydrangea plants abruptly declined just after the spring peak. Predators showed a delayed density-dependent numerical response. The population crashed even in the absence of predators, suggesting that the predators had nothing to do with the June decline. Furthermore, the rate of development from larva to adult and the fecundity in adult females on detached hydrangea leaves decreased markedly just prior to the abrupt decline in density in June. Consequently, seasonal changes in plant quality (perhaps influenced by secondary compounds) seem to contribute to the drastic decline of T. kanzawai density on hydrangea in June.  相似文献   

9.
Irina C. Rivier 《Hydrobiologia》1996,320(1-3):235-241
Cyclops kolensis Lill. forms dense populations in different water-bodies of the Upper Volga basin. In spring, when the other planktonic crustaceans have not yet appeared, C. kolensis is an important food object for fishes. Its active reproduction occurs from April to the beginning of June. A rapid accumulation of stage IV copepodids in the plankton occurs in June and at 12–14° they sink into the pelogene in a diapause stage. During the summer stagnation period the diapausing copepodids are distributed evenly over the bottom; their abundance here is 0.7–0.8 million ind. m-2 (Rybinsk reservoir). During storms and autumn active water mixing the copepodids together with detritus are disturbed and brought to the deepest, silt rich, part of the water-bodies. After the ice formation and at the beginning of bottom heating the diapausing copepodids are transported by near bottom currents and are concentrated in depressions; their biomass here reaches 60 g m-3. After the thermo-oxy-cline formation they revive and begin to live actively. Copepodids feed, accumulate adipose matter and in February–March they begin to moult.  相似文献   

10.
The factors influencing the abundance of phytoplankton in the Yellowknife River, in the Canadian subarctic, were determined from collections made for 42 consecutive months from June 1975 to November 1978. The spring bloom of plankton occured during April of each year in response to changing light conditions. WhileChlamydomonas lapponica was dominant during this period, it was replaced during the early part of the summer by a rapid succession ofDinobryon species in whichD. cylindricum was followed byD. sociale and in turn byD. bavaricum andD. divergens. Although low nutrient levels permitted the development ofDinobryon during the summer, the abundance of diatoms was greatly limited by the concentrations of SiO2 (< 0.1 g/m3). Algal densities began to decline in August and reached low overwintering levels by November. The absence of a fall bloom in densities was due to a combination of low temperatures and nutrient levels.P.O. Box 2310, Yellowknife, Northwest Territories, X1A 2P7, Canada  相似文献   

11.
We estimate fluctuations in population size and sex ratio, documentbreeding behavior and reproduction, and determine the diet of a population ofthe lesser long-nosed bat, Leptonycteris curasoae, in anisland cave in Chamela Bay, Jalisco, Mexico, with monthly sampling during anannual cycle (October 1999–October 2000). Based on the area of thecave's ceiling and wall covered with L. curasoae inrelation to the potential roost area without them, in 1999 the abundanceincreased from 80% in October to 100% in November and December. In 2000 thepopulation decreased to 80% in January, 50% in February, 30% in March, 20% inApril, 10% in May, 5% in June and July, and less than 1% in August. Thepopulation rapidly increased to 60% in September and to 80% in October.Throughout the year there were significantly more males than females; however,there was significant heterogeneity over months. In September–Novemberthere were more females, but in December–August there were more malespresent. The majority of pregnant and lactating females were observed fromDecember to March and in July, while males were reproductive fromSeptember–January and in May–June. Breeding activity was observed inthe cave in November–December. Twenty-six species of plants were consumedduring the year, based on pollen identification from fecal samples. Bombacaceousspecies were the most important component of the diet from January to May andCactaceae were most important in June–September. Peak abundance and reproductive activitycoincided with peak flower resource availability, which occurred between Octoberand January and in June–July. The year-round presence and reproductiveactivity of L. curasoae at this site throughout the yeardemonstrate that many individuals are annual residents in this area and indicatethe importance of this roosting site. In order to develop a successfulconservation program for L. curasoae, in addition toprotecting migratory corridors and northern maternity roosts, it is equallyimportant to identify and protect areas that function as breeding colonies andyear-round sanctuaries for resident populations in the south.  相似文献   

12.
温彬  高勤峰  董双林  宁鲁光 《生态学报》2016,36(14):4327-4336
于2012年7月至2013年4月调查了荣成靖海湾3个不同水深的刺参(Apostichopus japonicus)养殖池塘内大型底栖动物的构成,以了解不同水深对刺参养殖池塘环境条件的影响以及由此引起的大型底栖生物群落结构的改变。结果表明:3个不同水深梯度池塘(1#浅水位、2#正常水位和3#高水位)底部光照强度、叶绿素a(Chla)和总有机物(TOM)含量存在显著差异,各池塘水温差异不显著。光强、Chla和TOM含量在夏季、冬季和春季均表现为1#池塘显著高于3#池塘;秋季各池塘间光强和TOM含量差异不显著,Chla含量则表现为3#池塘显著高于1#池塘。各季节3个池塘间大型底栖动物在种类组成、丰度、生物量和多样性指数上均存在显著性差异。大型底栖动物丰度和生物量夏季均表现为1#池塘显著高于3#池塘,秋季和冬季则相反;春季1#池塘丰度显著高于3#池塘,生物量则差异不显著。这些差异主要与其各自优势种及其优势度指数大小有关。大型底栖动物多样性指数夏季和秋季均表现为1#池塘高于3#池塘,春季则相反,冬季各池塘间多样性指数差异不显著。单因子相似性分析(ANOSIM)表明,各季节3个池塘间大型底栖动物群落结构均存在显著差异,表明水深梯度对刺参养殖池塘大型底栖动物群落结构造成显著性影响。相似性百分比分析(SIMPER)显示,各季节对3个池塘间大型底栖动物群落差异起主要作用的物种为各个池塘的优势种。典范对应分析(CCA)表明,水深、Chla和TOM含量为影响大型底栖动物群落的主要环境因子。  相似文献   

13.
An annual reproductive periodicity of Tripneustes gratilla in northern Taiwan is revealed by both the gonad development stages and the gonad index. The gonads of T. gratilla recovered from spawning in February—March, propagated gametocytes in April—June, came to prematurity in July—August, and matured in September—November. Spawning occurred in October—December. The breeding pattern of T. gratilla over a broad geographical area appears to be related to seasonal changes of sea temperatures.  相似文献   

14.
A field experiment was conducted to elucidate the survival of P. verrucosum in infested bulk soil(T1) and infested soil with waste grain (T2). The infested soil and reference soil (T3) was filled into steel cylinders, which were buried and sampled 13 times during a period from October 1994 to March 1996.The abundance of P. verrucosum and indigenous soil fungi were assessed by dilution plating on a selective and diagnostic medium (DYSG). Kernel infection was examined in T2. According to our results, P. verrucosum seems well adapted to survival in arable soil and little affected by indigenous fungi. During the first autumn and winter the grain caused a proliferation of P. verrucosum while its abundance in bulk soil was more constant except for a decrease in February 95, which is ascribed to frost/thaw alternations. In T2, P. verrucosum initially infected more than 50% of the kernels but during the first few months it was ousted by other fungi. A hypothesis regarding waste grain as the natural niche for the fungus in the field was therefore partly rejected. A gradual decrease in the abundance of P. verrucosum in soil during spring, a die-off in the dry summer and aproliferation during the second winter were found in both T1 and T2. Our results cannot provide the reason for the increase during the second winter. On an overall basis, however, they show that P. verrucosum can survive in the field, proliferate on soil organic matter and probably become an integral part of the soil ecosystem. This may constitute a risk of grain contamination when given appropriate environmental conditions. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

15.
The modes of seed dispersal in the prostrate annual, Chamaesyce maculata, with multiple overlapping generations were investigated. We found that C. maculata has two modes of seed dispersal; autochory in the summer and myrmecochory in the autumn. Seasonally different modes of seed dispersal have not been known in other plant species. The large proportion of seeds produced in the summer was positioned further than the expanse of the parent plants by automatic mechanical seed dispersal. Therefore, autochory would be effective for avoiding competition between parent and offspring plants. No autochory occurred in the seeds produced in the autumn. The seeds of C. maculata without an elaiosome were dispersed by seed-collecting ants in the autumn. Although 18 ant species in total visited the plants of C. maculata at the 50 sites investigated, only two ant species, Tetramorium tsushimae and Pheidole noda frequently carried the seeds of C. maculata. The low frequency of seeds carried out of the nest by P. noda suggests that the workers of P. noda carry the seeds as food into their nest. So, P. noda might be a less effective seed disperser for C. maculata, corresponding to the effectiveness of seed dispersal by harvester ants. However, T. tsushimae ants frequently carried the seeds into and out of their nest, suggesting that T. tsushimae do not regard the seeds of C. maculata as a food resource. Thus, T. tsushimae may be an effective seed disperser for C. maculata.  相似文献   

16.
As a result of increased nutrient levels in the Baltic Sea during thepast 50 years, mass developments of filamentous algae have become a commonfeature along the Swedish east coast and deposition of organic matter has alsoincreased. To test whether these two factors have any effects on the early lifestages of Fucus vesiculosus a number of laboratory andfield studies were conducted. The amount of epilithic and epiphytic filamentousalgae on F. vesiculosus and the amount of deposited matterin the littoral zone were quantified during the two reproductive periods ofF. vesiculosus, early summer (May–June) and lateautumn (September–October). Both filamentous algae (Cladophoraglomerata) and deposited matter (introduced either before or aftersettlement of fertilized eggs) were shown to significantly decrease the numberof surviving germlings. The survival of germlings seeded on stones withfilamentous algae, or seeded on culture dishes concurrently with the lowestconcentration of deposited matter (0.1 g dm–2),was 5% or less. In the field, the amount of filamentous algae was significantlyhigher during F. vesiculosus summer reproduction, whereasthe amount of deposited matter collected in traps was significantly higherduring the period of autumn reproduction. The greatest biomass of filamentousalgae was observed at sheltered sites. Based on the negative effects offilamentous algae and deposited matter on Fucusrecruitmentand the observation of local and seasonal differences in abundance offilamentous algae and deposition, we suggest that the prerequisites for thesurvival of either summer or autumn-reproducing populations of F.vesiculosus in the Baltic Sea may differ locally.  相似文献   

17.
We collected data on diet and daytime activity budget, and investigated the phenology of food trees and food abundance for a group of Rhinopithecus roxellana on the East Ridge of Yuhuangmiao in the Qinling Mountains from November 2001 to December 2003. We calculated the seasonal activity budget using data collected by scan sampling from 84 full-day observations (winter 16, spring 18, summer 28, autumn 22 days). During scan sampling we recorded behavioral states, and the food items and species consumed. The subjects consumed 84 plant species, including trees and shrubs of 29 families, and lichens. Food species varied seasonally. The overall diet of R. roxellana consisted of 29.4% fruit/seeds, 29.0% lichens, 24.0% leaves, 11.1% bark, 4.2% buds, 1.3% twigs and 1.0% unidentified items. Because the abundance of different food items varied seasonally, the monkeys had to shift their major food items seasonally. The annual activity budget of R. roxellana was 36.2% time spent resting, 35.8% feeding, 22.9% moving, and 5.1% other behavior. Seasonal changes in activity budget were observed. R. roxellana spent more time moving in autumn, when the quality of the food might be highest, and least time moving in winter when the food quality might be lowest. Thus, this type of monkey has a passive foraging strategy.  相似文献   

18.
In Lake Lucerne, Switzerland, the predaceous cladocerans Leptodora kindti and Bythotrephes longimanus segregate along spatial and temporal dimensions. In spring (April–May/June), Bythotrephes longimanus occurs below 0–20 m, while Leptodora is absent. In summer and early autumn (July–September/October), when Leptodora dominates during daytime in the 0–20 m depth, Bythotrephes longimanus also lives in deeper zones. Food competition and fish predation pressure may be the cause of differences in ecology of Leptodora and Bythotrephes acquired during evolution. Due to its transparency and tolerance of higher temperature, Leptodora could avoid fish predation and, therefore, competes with Bythotrephes longimanus successfully. In addition, the differences between the two species may account for the spatial and temporal niche segregation in oligotrophic Swiss Lakes. But spatial niche segregation is less important in mesotrophic lakes with high prey density than in oligotrophic lakes with low prey density. In small, eutrophic lakes importance of temporal niche segregation also decreases, and Bythotrephes is seldom or not present. The preference of Bythotrephes to live in deeper water to avoid fish predation during summer may be the cause of its difficulties to establish itself in small and eutrophic lakes with high prey densities, where the hypolimnion is missing or anoxic.In the spring, Bythotrephes exhibits r-strategy (smaller body size and a higher fecundity), the female is already fertile after the first molt. In the summer, a K-strategy prevails (larger body length and lower fecundity than in the spring), and female Bythotrephes are fertile only after the second molt. Shortage of prey (biomass of Bosmina and Daphniadecreased after June especially in the surface layers) and the maximum fish predation pressure in summer may change the life strategy of Bythotrephes: while fecundity decreases from generation to generation, body length increases. Enhanced prey densities (e.g. during mesotrophic conditions in L. Lucerne) lead to larger individuals in summer and autumn.  相似文献   

19.
The epiphytic algae on surfaces of the macrophyte Ranunculus penicillatus (Dumort.) Bab. var. calcareus (R. W. Butcher) C. D. K. Cook and on Cladophora glomerata (L.) Kütz growing in the River Itchen at Otterbourne near Southampton were studied between February 1984 and June 1985. The river at this site has a mean flow rate of 0.33 m s–1, and is about 16 m wide and on average 20 cm deep, with a discharge ranging through the year between 0.34 and 2.46 m3 s–1. The pH of the river varies little around 8.2, with a mean alkalinity of 236 mg HCO inf3 sup1 l–1, because of its origin from chalk springs. Ranunculus grows throughout the year, with peaks of biomass in spring and autumn. It forms a very large surface for attachment of epiphytes, and covers on average 40% of the stream bed. Numbers of epiphyte cells removed from Ranunculus ranged through the year between 52 × 103 and 271 × 103 cells mm–2 stream floor, with maximum numbers in April, and a secondary peak in October. This pattern partly reflects fluctuations in the biomass of Ranunculus; the number of cells per unit area of plant surface showed a broader spring peak and lower fluctuations in other seasons. Diatoms formed 65 to 98% of these epiphyte cells, with chlorophytes reaching their peak (10%) in summer and cyanophytes (25%) in autumn. Estimates of biomass of these epiphytic forms, derived from measurements of chlorophyll c, indicate a range between 30 and 100 g dry weight m–2 of weed bed. Colonisation studies showed that the algae grow and reproduce throughout the year, with a mean generation time of about 5 days, suggesting an annual production of about 3 kg dry weight m–2 of weed bed, which makes epiphytic algae the principal primary producers in the stream. The numbers and biomass of epiphytic algae on Cladophora are considerably less.The species of epiphytic algae found on Ranunculus were generally similar to those growing on Cladophora, and to epilithic algae on pebbles of the stream bed, but different species were dominant on the different substrata. Algal cells in the water column were all derived from benthic habitats, although their relative abundance was very different.  相似文献   

20.
Zaira cinerea (Fallén) is a parasitoid fly (Diptera: Tachinidae) that attacks adult carabid beetles. To better understand mechanisms of population persistence in this species, we examined seasonality of host beetle abundance, the frequency of parasitism, and the timing of fly eclosion. In addition, we evaluated host quality using numbers of larvae or puparia per individual beetle as a measure of quality. The fly parasitized only large carabids (≥15 mm body length); the lengths of fly puparia reached 7.4–10.8 mm during development in beetle abdomens, and larger hosts are likely essential. Of the 18 large carabid species collected in this study, we chose two, Carabus maiyasanus Bates and Leptocarabus procerulus (Bates), because they were large and abundant (87% of total catch). The two carabids had different phonologies; C. maiyasanus was abundant from spring to summer, and its abundance dropped sharply in autumn, while L. procerulus was abundant in autumn and rare from spring to summer except July. Parasitism was observed in all the months from May to November except June, and adult flies eclosed more than once a year (in early summer, late summer, and mid‐autumn), indicating that the species is multivoltine. Host quality of L. procerulus was higher than that of C. maiyasanus. Carabus maiyasanus was mainly used as a host from spring to summer, and L. procerulus was used in autumn. Thus, adult beetles of one or both species are available over most of spring, summer, and autumn, allowing population persistence of this fly species over time.  相似文献   

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