The nematode fauna of the Murray River estuary,South Australia; the effects of the barrages across its mouth

The littoral nematode fauna of the Murray River, South Australia, above and below the barrages that control the outflow of the river into the Southern Ocean has been investigated by taking cores of the sediment at monthly intervals for one year. Samples of river water were taken at the same time for chemical analysis and sediment particle size has also been investigated.At two sites below the barrages the salinity varied depending on the volume of water discharged through the barrages. It rose almost to that of sea water while they remained closed, but fell to that of the river water when they were all open and discharging large volumes of river water. The nematode population fluctuated from about 12 200 to 180 000 m^-2 for nine months, but the numbers of live nematodes fell sharply in July through to September, accompanied by heavy nematode mortality, reaching 100% at one site in August. We attribute the mortality to a prolonged discharge of river water. More than 40 genera have been identified, most with cosmopolitan distributions.Above the barrages, at Mundoo and on Lake Alexandrina the water is fresh river water. The fauna was less dense than that below the barrages; with a maximum of 10000 m^-2. It comprised genera typical of freshwaters overseas (no comparable studies of Australian freshwater nematodes have been reported), such as Eutobrilus, Tripyla and Ironus, together with two species from typical marine genera, i.e. Mesacanthion and Enoploides. The latter species is very similar to E. fuviatilis from the Volga river.It is suggested that low population density below the barrages, when compared with other estuaries, reflects periodic mortality in estuarine nematodes when salinity falls drastically, whilst above the barrages there is a mixture of tolerant estuarine and typical freshwater nematodes.     

Annual Changes in Meiobenthos Community Structure in Alekseev Bight, Sea of Japan

We performed a comparative analysis of the taxonomical composition and population density of the meiobenthos and substrate types of Alekseev Bight, Sea of Japan, throughout the period when a plantation for mariculture of Japanese scallop was exploited in the bight and for a decade after the plantation had been removed. We found that silting of substrates in the bight decreased and the number of taxonomical groups that constituted the meiobenthos increased. The nematodes that, earlier, dominated the meiobenthos in terms of population density were later exceeded by foraminiferans, the species diversity of which increased. Changes are revealed in the composition of the dominant species of these groups.     

Seasonal Dynamics of the Population Density of Mass Species and Trophic Groups of Free-living Marine Nematodes

Seasonal changes in the distribution density and trophic-group composition of marine nematodes were studied in a strait between Reineke and Popova islands (Amurskii Bay, Sea of Japan). Four nematode species dominated throughout the observation period, constituting altogether over 60% of the total nematode population density. Temperature indirectly affected the population composition of mass nematode species. The nine dominant species from Amurskii Bay (Sea of Japan) were classified into three trophic groups. In the spring, the nematode taxocene was dominated by predators; in the autumn, by nonselective detrivorous species; and in the winter and summer, by bottom feeders. Within each season, the trophic structure of the nematode taxocene was almost constant, with the number of species constituting the trophic group being the only variable.     

Effect of the Razdol’naya River on structure of the free-living nematode community of the Amursky Bay,Sea of Japan

The effect of the Razdol’naya River on the littoral and sublittoral nematode community was studied in the innermost part of the Amursky Bay. Thanks to the seasonal abundance of juveniles of macrobenthic animals, pseudomacrobenthic species prevailed in the meiobenthos littoral community. Juvenile amphipods dominated (39.5%), the percentage of nematodes was 18.4% (45 species). The nematodes dominated in the meiobenthos community (65.7%, 71 species) at the sublittoral zone. The similarity of the species structure of littoral and sublittoral nematodes reached 36.5%. Low population density (2.6±1.7 thousand ind/m²) and poor species diversity of nematodes (7 species), the dominating form being Oncholaimium paraolium, were recorded at the littoral zone, which was subjected to direct riverine influence (1‰salinity). The correlation analysis revealed no relationship between salinity and population density of nematodes at the littoral zone. At the sublittoral zone (at stations of salinity less than 2.85‰) the parameters of population density (73.9±32.3 thousand ind/m²) and species diversity (12 species) of nematodes were the lowest, Parodontophora timmica dominated. A poor expressed dependence between the density of nematode populations and salinity was revealed. The correlation between the average size of ground particles and population density of nematodes was recorded. The greatest similarity of the species structure of littoral and sublittoral nematodes (26.67%) was recorded on gravel-sand bottoms.     

Species composition and distribution of free-living marine nematodes in Vostok Bay, Sea of Japan

The qualitative and quantitative composition of free-living marine nematodes have been studied in Vostok Bay (Peter the Great Bay, Sea of Japan). It is found that the population density of nematodes in the bottom sediments of Vostok Bay shows an uneven distribution. The mean population density equaled 56800 ± 23400 specimens/m². A correlation has been revealed between the population density of nematodes and the substrate type. Altogether, 85 species of nematodes have been found; they were dominated by Sabatieria palmaris, Rhabdodemania orientalis, Araeolaimus parvibulbosus, Oncholaimium paraolium, Doryolaimopsis peculiaris, and Metachromadora itoi. Six taxocenoses of nematodes were distinguished, taking into account the species dominating in the population density and using cluster analysis of the obtained data. The dominating trophic assemblage of nematodes was “scrapers.” In general, the species composition of nematodes in Vostok Bay is characterized by the relatively great similarity with that in other areas of Peter the Great Bay (Sea of Japan).     

Diversity and distribution of the mangrove forests in Taiwan

In a survey of 1992 to 1994, mangrove forests withfour species of true mangroves, Kandelia candel(L.) Druce, Avicennia marina(Forsk.) Vierh.,Rhizophora stylosaGriff., and Lumnitzera racemosaWilld., were found at 22locations in the west coast of Taiwan. The northernrange of their distribution was at Tanshui Estuary(Latitude 25^°11N) and the southern range atTapen Bay (22^°28N). The total area wasestimated to be 286.95 ha. There was an obvious changein species composition and a decrease in speciesnumber of true mangroves from south to north: the fourspecies dominated by A. marinain thesouth and K. candelas thesole species in the north. Air temperature associatedwith sea surface temperature and oceanic currents inwinter, but not soil property, was found to be theprimary environmental factor, affecting the diversityand distribution of true mangroves in Taiwan as wellas in the northeast region of Asia.     

A Theoretical Model of the Winter Survival Dynamics of Meloidogyne spp. Eggs and Juveniles

A theoretical model of the winter survival dynamics of Meloidagyne spp. was developed by considering the roles of egg hatching and juvenile mortality and the initial populations of eggs and juveniles at the onset of winter. Two distinct patterns of juvenile dynamics appear which depend upon the numerical values of the model parameters. The model predicts whether eggs or juveniles are the major component of overwintering nematode populations at any time prior to planting. The model could be elaborated to include egg viability and differential mortality of eggs but at some cost in ease of mathematical analysis. A general procedure for fitting the proposed model to experimental or observational data is outlined.     

Influence of Soil Temperature and pH on Pratylenchus Penetrans and P. crenatus in Alfalfa and Timothy

Numbers of Pratylenchus penetrans in alfalfa and timothy, and to a lesser extent P. crenatus in timothy, increased substantially as temperature increased from about l0 C to 30 C. However, P. crenatus in alfalfa decreased in number as temperature increased. Mobility of P. crenatus in vertical soil columns decreased as temperature increased from 9.5 C to 28.5 C. Raising the soil pH from 5.0 to 6.9 in which alfalfa was grown increased the numbers of P. penetrans and greatly reduced the numbers of P. crenatus. The numbers of both nematode species in timothy were reduced significantly as soil pH was increased. The optimum soil pH for movement of P. penetrans was 6.0. Pratylenchus crenatus moved equally well over a range of pH 5.0 to 7.0.     

Plant-parasitic nematodes associated with semi-temperate vegetables in the highlands of Benguet Province,Philippines

Thirteen genera (Aphelenchoides, Criconemella, Ditylenchus, Globodera, Helicotylenchus, Hoplolaimus, Meloidogyne, Longidorus, Paratrichodorus, Pratylenchus, Trichodorus, Tylenchus and Xiphinema) of plant-parasitic nematodes were found associated with 15 semi-temperate vegetable crops in Benguet Province, Philippines. Among these taxa, Helicotylenchus, Meloidogyne and Pratylenchus were the most predominant. Four taxa that can vector plant viruses were also found: Trichodorus, Paratrichodorus, Longidorus and Xiphinema. The taxa Paratrichodorus, Longidorus and Xiphinema have not been reported previously on semi-temperate vegetable crops in the Philippines. The most predominant nematode species were H. dihystera, P. penetrans and Meloidogyne spp. These nematodes were found abundantly in five out of the nine municipalities surveyed: Atok, Bakun, Buguias, Kibungan and Mankayan. The incidence of Criconemella sp., G. rostochiensis, Hoplolaimus sp., Longidorus sp., Trichodorus sp. and Tylenchus sp. was also recorded in at least one municipality. The predominant nematode species were also found on every vegetable crop examined. More particularly, H. dihystera was highly abundant on cucumber, cauliflower, Chinese cabbage, sweet pepper, snap bean and onion; P. penetrans was highly abundant on carrot, celery, garden pea, broccoli, cabbage, Chinese cabbage, Chinese mustard, onion, potato, radish and lettuce; Meloidogyne spp. were highly abundant on celery, cucumber, Chinese mustard, carrot, sweet pepper and potato. According to the formula by Fortuner and Merny (1973 Fortuner, R and Merny, G. 1973. Les nématodes parasites des racines associés au riz en Basse Casamance (Senegal) et en Gambie, Cahiers de l'Orstom. Série Biologique, 21: 3–20.  [Google Scholar]) for identifying the potential plant pathogens, these predominant nematode species were classified as potential pathogens with the ability to cause economic loss which shows that they are probably important active pathogens of these semi-temperate vegetables. The incidence of other nematode species in the rhizosphere included G. rostochiensis on sweet pepper, garden pea and potato; D. dipsaci on onion; Tylenchus sp. on lettuce, onion and broccoli; A. fragariae on carrot, lettuce, broccoli and onion; Criconemella sp. on cucumber and cauliflower; Longidorus sp. on carrot, celery, cucumber, broccoli, cabbage, cauliflower, Chinese mustard, snap beans, onion, potato and radish; X. americanum on lettuce, broccoli and onion; Paratrichodorus sp. on carrot, lettuce, onion and potato; and Trichodorus sp. on snap bean, potato and radish.     

基于GIS和RS的沈阳城市潜在人口分布特征

基于QuickBird卫星影像,采用阴影长度法对城市居住建筑面积进行测算,结合社会经济统计数据对沈阳城市潜在人口分布特征进行分析.结果表明: 2015年,沈阳市三环内各行政区潜在人口分布不均;三环内潜在人口空间分布呈现典型的圈层结构特征;各行政区潜在人口数量为铁西区＞沈河区＞皇姑区＞于洪区＞和平区＞大东区＞东陵区;各行政区潜在人口密度为铁西区＞和平区＞沈河区＞皇姑区＞于洪区＞大东区＞东陵区;城市西部潜在人口密度高于东部,南部高于北部.居住建筑及人口的空间分布与区域的自然条件、经济状况以及基础设施建设等因素紧密相关.在未来城市规划建设中,应考虑加强铁西区以及中心城区的基础设施建设,适当增加公园绿地数量,合理开发城市南部的居住用地,适当控制居住人口数量,避免造成较大的环境压力.     

Population dynamics of the parasitic stages of Ostertagia spp. in sheep

Callinan A. P. L. and Arundel J. H. 1982. Population dynamics of the parasitic stages of Ostertagia spp. in sheep. International Journal for Parasitology12: 531–535. The development and survival of continuing infections of Ostertagia spp. in weaner sheep were studied in order to develop a general model of the parasitic stages of the life cycle of these sheep nematodes. After 10 days, 13.8% of infective larvae (L₃) given at the rate of 1 dose of 1000 L₃ twice per week (group 1) and 20.8% of L₃ given at the rate of 10,000 L₃ twice per week (group 2) were recovered in the first of the serial nematode counts. In the final counts at 137 days, 7.7 and 0.7% were recovered in these groups. The build up and maintenance of nematode populations was regulated and related to the level of infection. A model in which the death rate of the parasitic stages was a function of the time of exposure to infection and rate of infection was used to describe the serial total nematode counts. During the experiment there was no noticeable trend in numbers of fourth stage larvae (L₄) in nematode counts, the size of adult nematodes, nematode egg counts (EPG) and egg output per female nematode (EPF). After 112 days, liveweight gains were significantly reduced in group 2 only, but increases in wool lengths were significantly reduced in both groups.     

Developing management plans for the mangrove forest reserves of mainland Tanzania

The mangroves of Tanzania are currently not being managed although they are legally gazetted as forest reserves. The management of this overexploited and under estimated natural resource rests with the Forest and Beekeeping Division in the Ministry of Natural Resources and Tourism. It is the Division's intention to conserve the mangroves of Tanzania, therefore steps are being taken to reach that goal. So far the Division, through its established mangrove project, has done an inventory of all the mangroves of mainland Tanzania with the assistance of NORAD. Aerial photography and ground checks were used to assess the state of all the mangrove reserves in the country. Literature search and a socio-economic study was also undertaken.The inventory revealed that the area covered by mangrove vegetation is 115 901 ha while the previous records indicate about 80 000 ha. If the bare saline areas, water bodies, and salt pans which are part of the mangrove reserves are included, the area amounts to 172 879 ha for the Tanzania mainland. The mangrove reserves have already been mapped in 30 sheets. Some sheets are mapped using a scale of 1:25 000 while others are mapped in 1:50 000 scale. The maps show the vegetation types, the area of each vegetation type, and the stand density and height of each compartment.The paper therefore presents the current status of the mangroves of Tanzania in respect to area, distribution and vegetation types. Included are the strategies being used to develop the mangrove management plans for Tanzania.     

Some aspects of the synanthropization of nine species of the Turdidae family in Kaliningrad

Numbers, dynamics of distribution for ten years, and relations between density and the rate of urbanization in nine species of Turdidae are calculated. During the last ten years the area of spatial distribution of most species increased by 2–15 times. A positive relationship between the numbers of birds and the rate of urbanization is revealed in the Redstart (R_{N 142} = 0.16; p = 0.049) and the Black Redstart (R_{N 134} = 0.25; p = 0.03), a negative relationship was observed in the Nightingale (R_{N 134} = ?0.23; p = 0.006) and the Robin (R_{N 43} = ?0.28; p = 0.06). The numbers of Whinchat, Wheatear, and thrushes does not depend on the rate of urbanization.     

Contrasting genetic structures of two parasitic nematodes,determined on the basis of neutral microsatellite markers and selected anthelmintic resistance markers

For the first time, the neutral genetic relatedness of natural populations of Trichostrongylid nematodes was investigated in relation to polymorphism of the β‐tubulin gene, which is selected for anthelminthic treatments. The aim of the study was to assess the contribution of several evolutionary processes: migration and genetic drift by neutral genetic markers and selection by anthelminthic treatments on the presence of resistance alleles at β‐tubulin. We studied two nematode species (Teladorsagia circumcincta and Haemonchus contortus) common in temperate climatic zones; these species are characterized by contrasting life history traits. We studied 10 isolated populations of goat nematode parasites: no infected adult goat had been exchanged after the herds were established. Beta‐tubulin polymorphism was similar in these two species. One and two β‐tubulin alleles from T. circumcincta and H. contortus respectively were shared by several populations. Most of the β‐tubulin alleles were ‘private’ alleles. No recombination between alleles was detected in BZ‐resistant alleles from T. circumcincta and H. contortus. The T. circumcincta populations have not diverged much since their isolation (F_ST <0.08), whereas H. contortus displayed marked local genetic differentiation (F_ST ranging from 0.08 to 0.18). These findings suggest that there are severe bottlenecks in the H. contortus populations, possibly because of their reduced abundance during unfavourable periods and their high reproductive rate, which allows the species to persist even after severe population reduction. Overall, the data reported contradict the hypothesis of the origin of β‐tubulin resistance alleles in these populations from a single mutational event, but two other hypotheses (recurrent mutation generating new alleles in isolated populations and the introduction of existing alleles) emerge as equally likely.     

The Development and Influence of Meloidogyne incognita and M. javanica on Wheat

The effects of soil temperature and initial inoculum density (Pi) of Meloidogyne incognito and M. javanica on growth of wheat (Triticum aestivum cv. Anza) and nematode reproduction were studied in controlled temperature baths in the glasshouse. Nematode reproduction was directly proportional to temperature between 14 and 30 C for M. incognita and between 18 and 26 C for M. javanica. Reproduction rates (Pf/Pi, where Pf = final number of eggs) for Pi''s of 3,000, 9,000, and 30,000 eggs/plant were greatest at each temperature when Pi = 3,000. Maximum M. incognita reproduction rate (Pf/Pi = 51.12) was at 30 C. At 26 C, M. javanica reproduction (Pf/Pi = 14.82, 9.02, and 4.23 for Pi = 3,000, 9,000, and 30,000, respectively) was about half that of M. incognita when Pi = 3,000 or 9,000 but similar when Pi = 30,000. Reproduction of both species was depressed between 14 and 18 C. Shoot and root growth and head numbers were inversely related to soil temperature between 14 and 30 C but were not affected by the Pi of M. incognita when 7 d old seedlings were inoculated. When newly germinated seedlings were inoculated with M. incognita or M. javanica, the Pi did not affect shoot and root fresh weights, shoot/root ratio, and tillering, but it did reduce root dry weight (M. javanica at 26 C) and increase shoot dry weight (M. incognita at 18-22 C). The optimum temperature range is lower for wheat growth than for nematode reproduction. Wheat cv. Anza is a good host for M. incognita and M. javanica, but it is tolerant to both species.     

Plant-parasitic nematodes and yellowing of leaves associated with black pepper plants in Vietnam

Thirty-five nematode species belonging to 19 genera were extracted from 432 soil and root samples collected in 19 districts in six provinces in the North Central Coast, Central Highlands and Phu Quoc Island. Based on our study, the predominant nematode species associated with black pepper plants in Vietnam is Meloidogyne incognita: almost every soil and root sample examined during our study was infected with this root-knot nematode species. No difference in frequency of occurrence of M. incognita among the three agro-ecological regions surveyed was observed. However, the root population density of M. incognita in black pepper plants was on average about five times higher in the North Central Coast and Central Highlands than in Phu Quoc Island. Large differences in root population density of M. incognita on black pepper plants were observed in different districts within the same agro-ecological region. Black pepper roots infected with M. incognita showed the same type of galls as described in the literature. The percentage of root galling averaged about 40% in all the three agro-ecological regions. The percentage of black pepper plants with yellow leaves was on average about 20–25% in the North Central Coast and Central Highlands, which was somewhat higher compared to Phu Quoc Island (16.9%). Large differences in percentage of black pepper plants with yellow leaves were observed in different districts within the same agro-ecological region. The same type of yellow leaves as described in the literature for black pepper plants infected with Meloidogyne species was observed in our study. In general, a positive relationship between the soil and root population densities of M. incognita on black pepper plants and percentage of plants with yellow leaves was observed. However, in one district (Quang Tri) a relatively low nematode population density was associated with a high percentage of plants with yellow leaves. Five nematode species were recorded for the first time on black pepper plants in Vietnam. Our study reconfirms previous reports that Radopholus similis does not occur in Vietnam.