Trematode Populations in the Atlantic Argentine, Argentina silus, and Their Use as Biological Indicators

1969 ◽  
Vol 26 (4) ◽  
pp. 879-891 ◽  
Author(s):  
J. S. Scott
Keyword(s):  
Biological Indicators ◽  
Reciprocal Relationship ◽  
Intermediate Hosts ◽  
Length Frequency ◽  
The West ◽  
Low Level ◽  
Mean Size ◽  
Mature Fish ◽  
Plankton Feeders ◽  
Trematode Parasites

The trematode parasites Lecithophyllum botryophorum, Derogenes various, Hemiurus levinseni, and Lampritrema nipponicum were found in Argentina silus off Nova Scotia and Newfoundland. Changes in the length-frequency distribution in the population of L. botryophorum at different times of the year reflected changes in parasite recruitment and were used tentatively to estimate the life span of the parasite.Hemiurus levinseni had a high intensity and incidence in very young fish, decreasing to a low level in mature fish; L. botryophorum had the reciprocal relationship; and D. varicus was intermediate in incidence and had a low level of intensity in fish of all sizes. These results were related to the occurrence of the intermediate hosts of the parasites and to the movement of A. silus to deeper water as it increases in size. The intensity of infestation with L. botryophorum increased from south to north. Seasonal variation in recruitment, with a peak immediately after spawning, was reflected in the intensity of infestation, mean size, and percentage of immature specimens of L. botryophorum.The young A. silus are midwater plankton feeders and the mature fish change to a diet that incorporates a high proportion of the crustacean intermediate host of L. botryophorum, probably an amphipod. There is no parasitological evidence of separate populations of A. silus in the west Atlantic.

scholarly journals A re-evaluation of the occurrence of freshwater molluscs in the Kruger National Park

Koedoe ◽  
1998 ◽  
Vol 41 (1) ◽  
Author(s):  
K.N. De Kock ◽  
C.T. Wolmarans
Keyword(s):  
Species Diversity ◽  
National Park ◽  
Kruger National Park ◽  
Intermediate Hosts ◽  
Freshwater Molluscs ◽  
Freshwater Mollusc ◽  
Mollusc Species ◽  
Trematode Parasites

Most of the previous records of the freshwater molluscs from the Kruger National Park date back prior to and up to 1966. On account of several droughts between 1966 and 1995 it was decided to do a survey of the freshwater mollusc population in 1995 to evaluate the effect of these droughts. The traditional mollusc intermediate hosts were also screened for trematode parasites to establish whether or not they were infected. No infected molluscs were found. Eight of the 19 species reported up to 1966 were not found during the 1995 survey. Three new mollusc species were collected in 1995. The consequences of the drought are clearly visible when the species diversity found in the dams in the 1995 survey, is compared to what was previously recorded.

scholarly journals Global warming and temperature-mediated increases in cercarial emergence in trematode parasites

Parasitology ◽  
2005 ◽  
Vol 132 (1) ◽  
pp. 143-151 ◽  
Author(s):  
R. POULIN
Keyword(s):  
Global Warming ◽  
Geographical Distribution ◽  
Climate Models ◽  
Extreme Values ◽  
Geometric Mean ◽  
Effect Of Temperature ◽  
Trematode Species ◽  
Intermediate Hosts ◽  
Cercarial Production ◽  
Trematode Parasites

Global warming can affect the world's biota and the functioning of ecosystems in many indirect ways. Recent evidence indicates that climate change can alter the geographical distribution of parasitic diseases, with potentially drastic consequences for their hosts. It is also possible that warmer conditions could promote the transmission of parasites and raise their local abundance. Here I have compiled experimental data on the effect of temperature on the emergence of infective stages (cercariae) of trematode parasites from their snail intermediate hosts. Temperature-mediated changes in cercarial output varied widely among trematode species, from small reductions to 200-fold increases in response to a 10 °C rise in temperature, with a geometric mean suggesting an almost 8-fold increase. Overall, the observed temperature-mediated increases in cercarial output are much more substantial than those expected from basic physiological processes, for which 2- to 3-fold increases are normally seen. Some of the most extreme increases in cercarial output may be artefacts of the methods used in the original studies; however, exclusion of these extreme values has little impact on the preceding conclusion. Across both species values and phylogenetically independent contrasts, neither the magnitude of the initial cercarial output nor the shell size of the snail host correlated with the relative increase in cercarial production mediated by rising temperature. In contrast, the latitude from which the snail-trematode association originated correlated negatively with temperature-mediated increases in cercarial production: within the 20 ° to 55 ° latitude range, trematodes from lower latitudes showed more pronounced temperature-driven increases in cercarial output than those from higher latitudes. These results suggest that the small increases in air and water temperature forecast by many climate models will not only influence the geographical distribution of some diseases, but may also promote the proliferation of their infective stages in many ecosystems.

Biology and Management of Dogfish Sharks

2009 ◽  
Keyword(s):  
Juvenile Fish ◽  
Catch Rate ◽  
Spiny Dogfish ◽  
Commercial Fishery ◽  
Sources Of Information ◽  
Strait Of Georgia ◽  
The Status ◽  
Mean Size ◽  
Catch Rates ◽  
Mature Fish

Abstract.—Spiny dogfish <em>Squalus acanthias </em>have been an important component of the Strait of Georgia fisheries from the late 1800s to the late 1940s, when the fishery collapsed owing to overfishing and changes in market demand. The stock population levels have sustained a commercial fishery of approximately 2,000 metric tons since 1978. Recent concerns regarding the status of dogfish stocks worldwide have reprioritized the status assessment of dogfish in British Columbia. Longline research surveys were conducted for dogfish in the Strait of Georgia in 1986, 1989, and 2005. Additional sources of information are catch and effort data collected through logbook records from the commercial longline fishery. Recent improvements in gear configuration resulted in a switch in the mid-1990s from traditional J hooks to circle hooks, which makes direct comparison of catch rates difficult. In November 2004 a calibration experiment using J hooks and circle hooks demonstrated that, overall, spiny dogfish catch per unit effort (CPUE) for circle-hook gear was 1.6–1.7 times higher than that for J-hook gear. After applying this conversion to the commercial longline CPUE data available for 1980–1984 and 2000–2004, no significant trend in catch rate over time was detected. The catch rate observed in the longline research survey actually increased in 2005 compared to 1986 and 1989. In both fisheries and research data, the proportion of smaller spiny dogfish in the size distribution has increased, reducing the overall mean size. The decline in mean size is probably due to an increase in recruitment of juvenile fish. However, caution in management of this stock is warranted given that the current commercial fishery is now landing a large proportion (estimated 80%) of immature fish. Increased fishing pressure on juveniles could have implications for the abundance of mature fish in upcoming decades.

scholarly journals Analysis of Possible Triggering Mechanisms of Severe Thunderstorms in the Tropical Central Andes of Peru, Mantaro Valley

Atmosphere ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 301 ◽  
Author(s):  
J.L. J.L. ◽  
A.S. A.S. ◽  
S. S. ◽  
D. D. ◽  
E. E. ◽  
...  
Keyword(s):  
Central Andes ◽  
The South ◽  
The West ◽  
Subtropical Anticyclone ◽  
Low Level ◽  
The Andes ◽  
Severe Thunderstorms ◽  
Westerly Winds ◽  
Moisture Fluxes ◽  
Triggering Mechanisms

The aim of the present study is to analyze the triggering mechanisms of three thunderstorms (TSs) associated with severe rainfall, hail and lightening in the tropical central Andes of Peru, specifically above the Huancayo observatory (12.04 ∘ S, 75.32 ∘ W, 3313 m a.s.l.) located in the Mantaro valley during the spring-summer season (2015–2016). For this purpose, we used a set of in-situ pluviometric observations, satellite remote sensing data, the Compact Meteorological Ka-Band Cloud Radar (MIRA-35C), the Boundary Layer Tropospheric Radar and downscaling model simulations with the Weather Research and Forecasting (WRF) Model (resolutions: 18 km, 6 km and 2 km), and the Advance Regional Prediction System (ARPS) (resolution: 0.5 km) models in order to analyze the dynamic of the atmosphere in the synoptic, meso and local scales processes that control the occurrence of the three TS events. The results show that at synoptic scale, the TSs are characterized by the southern displacement of the South-east Pacific Subtropical Anticyclone up to latitudes higher than 35 ∘ S, by the weakening and south-eastern displacement of the Bolivian high–North east low system and by the intrusion of westerly winds along the west side of the central Andes at upper and medium levels of the atmosphere. At meso-scale, apparently, two important moisture fluxes from opposite directions are filtered through the passes along the Andes: one from the north-west and the other from the south-east directions converge and trigger the deep convection into the Mantaro valley. These moisture fluxes are generated by the intrusion of the sea-breeze from the Pacific ocean along the west of the Andes coupling with upper and middle westerly winds and by the thermally induced moisture fluxes coming from the South American low level jet at the east side of the Andes. At the local scale, there is a low-level conditional instability in the previous hours as well as during the occurrence of the TSs above the Huancayo observatory. In addition, the simulation results indicated the possibility of generation of inertial gravity waves in the Amazon basin, associated with geostrophic adjustment which transports energy and moisture into the central Andes plateau and consequently intensifies the thunderstorms above the Mantaro valley.

Trematodes and snails: an intimate association

2004 ◽  
Vol 82 (2) ◽  
pp. 251-269 ◽  
Author(s):  
Anne E Lockyer ◽  
Catherine S Jones ◽  
Leslie R Noble ◽  
David Rollinson
Keyword(s):  
Evolutionary History ◽  
Intermediate Hosts ◽  
Molecular Approaches ◽  
Complex Interactions ◽  
Intimate Association ◽  
In Vitro Cell Cultures ◽  
Medical Burden ◽  
Insight Into ◽  
Trematode Parasites

Trematode parasites share an intimate relationship with their gastropod intermediate hosts, which act as the vehicle for their development and transmission. They represent an enormous economic and medical burden in developing countries, stimulating much study of snail–trematode interactions. Laboratory-maintained snail–trematode systems and in vitro cell cultures are being used to investigate the molecular dialogue between host and parasite. These dynamic and finely balanced antagonistic relationships, in which parasites strongly influence the physiology of the host, are highly specific and may occasionally demonstrate co-speciation. We consider the mechanisms and responses deployed by trematodes and snails that result in compatibility or rejection of the parasite, and the macroevolutionary implications that they may effect. Although for gastropods the fossil record gives some insight into evolutionary history, elucidation of trematode evolution must rely largely upon molecular approaches, and for both, such techniques have provided fresh and often surprising evidence of their origins and dispersal over time. Co-evolution of snails and trematodes is becoming increasingly apparent at both cellular and population levels; the implications of which are only beginning to be understood for disease control. Untangling the complex interactions of trematodes and snails promise fresh opportunities for intervention to relieve the burden of parasitic disease.

scholarly journals Intraseasonal Land–Atmosphere Coupling in the West African Monsoon

2008 ◽  
Vol 21 (24) ◽  
pp. 6636-6648 ◽  
Author(s):  
Christopher M. Taylor
Keyword(s):  
Soil Moisture ◽  
Sensible Heat Flux ◽  
West African Monsoon ◽  
West African ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
The West ◽  
African Monsoon ◽  
Low Level ◽  
The Impact

Abstract Via its impact on surface fluxes, subseasonal variability in soil moisture has the potential to feed back on regional atmospheric circulations, and thereby rainfall. An understanding of this feedback mechanism in the climate system has been hindered by the lack of observations at an appropriate scale. In this study, passive microwave data at 10.65 GHz from the Tropical Rainfall Measuring Mission satellite are used to identify soil moisture variability during the West African monsoon. A simple model of surface sensible heat flux is developed from these data and is used, alongside atmospheric analyses from the European Centre for Medium-Range Weather Forecasting (ECMWF), to provide a new interpretation of monsoon variability on time scales of the order of 15 days. During active monsoon periods, the data indicate extensive areas of wet soil in the Sahel. The impact of the resulting weak surface heat fluxes is consistent in space and time with low-level variations in atmospheric heating and vorticity, as depicted in the ECMWF analyses. The surface-induced vorticity structure is similar to previously documented intraseasonal variations in the monsoon flow, notably a westward-propagating vortex at low levels. In those earlier studies, the variability in low-level flow was considered to be the critical factor in producing intraseasonal fluctuations in rainfall. The current analysis shows that this vortex can be regarded as an effect of the rainfall (via surface hydrology) as well as a cause.

scholarly journals Role of the West African Westerly Jet in Sahel Rainfall Variations

2012 ◽  
Vol 25 (8) ◽  
pp. 2880-2896 ◽  
Author(s):  
Bing Pu ◽  
Kerry H. Cook
Keyword(s):  
Decadal Variability ◽  
West African Monsoon ◽  
Moisture Flux ◽  
Relative Vorticity ◽  
West African ◽  
The West ◽  
Low Level ◽  
Westerly Jet ◽  
Positive Vorticity ◽  
Sahel Rainfall

Abstract The West African westerly jet is a low-level feature of the summer climatology that transports moisture from the eastern Atlantic onto the African continent at 8°–11°N. This study examines the relationship between the jet and Sahel precipitation variability in August, when both the jet and rainfall reach their seasonal maxima. Variations of the West African westerly jet are significantly positively correlated with precipitation variations over the Sahel on both interannual and decadal time scales. Three periods are identified (1958–71, 1972–87, and 1988–2009), corresponding to times with a wet Sahel–strong jet, dry Sahel–weak jet, and relatively wet Sahel–strong jet. In wet (dry) periods, enhanced (decreased) westerly moisture fluxes associated with a strong (weak) jet increase (decrease) the low-level moisture content over the Sahel, decreasing (enhancing) the stability of the atmosphere. This association between the jet and Sahel rainfall is also found in case studies of 1964, 1984, 1999, and 2007. The southerly moisture flux associated with the West African monsoon has less pronounced decadal variability than the westerly moisture flux of the West African westerly jet and weaker correlations with Sahel rainfall. When the monsoon flow is weak, for example, 1999 and 2007, the Sahel may still experience positive precipitation anomalies in association with strong westerly moisture transport by the jet. The West African westerly jet is also important for stabilizing the regional vorticity balance by introducing strong relative vorticity gradients. Northward flow advects low relative vorticity south of the jet to balance positive vorticity tendencies generated by midtropospheric condensation.

scholarly journals SOSIALISASI POLITIK KPU PROVINSI JAWA BARAT DALAM PEMILIHAN GUBERNUR DAN WAKIL GUBERNUR JAWA BARAT TAHUN 2018

2019 ◽  
Vol 4 (2) ◽  
pp. 223-256
Author(s):  
Cecep Nurzaman ◽  
Neneng Yani Yuningsih ◽  
Firman Manan
Keyword(s):  
Qualitative Method ◽  
Political Socialization ◽  
The Political ◽  
The West ◽  
West Java ◽  
Persons With Disabilities ◽  
Low Level ◽  
Political Access ◽  
Access Rights ◽  
Voter Groups

This research analyzes the political socialization carried out by the West Java Provincial KPU against disability voter groups in the election of the Governor and Deputy Governor of West Java in 2018. This was motivated by the low level of participation in disability voters as well as the importance of opening political access rights for persons with disabilities. The theory used in this study is the theory of political socialization from Rush and Althoff where there are three methods, namely imitation, instruction and motivation. The method in this study is a qualitative method. The result of this research is the importance of political socialization to disability voters, because it is mandated by the 1945 Constitution and its derivative regulations and to realize an ideal democracy according to the criteria of voting equality and political socialization carried out by the West Java Provincial KPU to persons with disabilities to increase participation its politics with imitation methods, instruction and motivation.

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