Variations inter-populations de la structure d'âge et de la croissance du Prosobranche Bithynia tentaculata L.

1985 ◽  
Vol 63 (6) ◽  
pp. 1345-1353 ◽  
Author(s):  
B. Vincent ◽  
C. Létourneau
Keyword(s):  
Age Structure ◽  
Sexual Maturity ◽  
Abiotic Factors ◽  
Temporal Variations ◽  
Population Densities ◽  
Bithynia Tentaculata ◽  
Spatio Temporal ◽  
Sudden Decrease ◽  
Velocity Water ◽  
St Lawrence River

The main variations in age structure and growth of different generations were studied in 25 populations of the prosobranch Bithynia tentaculata in the St. Lawrence River (Québec). The general unbalanced age structures of the populations reflect a low recruitment encountered during an odd year because of a general disturbance in the environment. The age structure is correlated to temperature, sediments, and current velocity. Water chemistry is largely responsible for the spatial variations in lengths of the adults, but these variations do not seem to influence the age at sexual maturity. Population densities may be regulated by an increase in the growth rate of young which would reduce the age at sexual maturity in populations with low densities; this mechanism would, however, be of little use to compensate a sudden decrease in density or an unbalanced age structure in a population. These results and those of previous studies on this species reveal the important role played by abiotic factors in regulating the spatio-temporal variations of the demographic profile of this prosobranch which possesses a high phenotypic plasticity.[Journal translation]

Variations de la fécondité et de la structure des populations chez Bithynia tentaculata L. (Gastropoda: Prosobranchia)

1983 ◽  
Vol 61 (11) ◽  
pp. 2417-2423 ◽  
Author(s):  
B. Vincent ◽  
M. Gaucher
Keyword(s):  
Growth Rate ◽  
Population Structure ◽  
Sexual Maturity ◽  
Temporal Variations ◽  
Bithynia Tentaculata ◽  
Poor Recruitment ◽  
One Year ◽  
Iteroparous Species ◽  
St Lawrence River

In 1982, we studied three populations of the snail Bithynia tentaculata living in a cold environment in the upper estuary of the St. Lawrence River (Quebec), with particular emphasis on the population structure and the fecundity of the different generations. This and other studies show that large variations can occur in the age of sexual maturity from year to year; these are caused by variations in the growth rate and could cause important changes in the growth rate of the populations. Also, there does not appear to be an adequate mechanism to compensate poor recruitment in one year and thus an unbalance in the population structure can be seen for at least 7 years. Fecundity varies from one population to another and from one year to the next. Differences are greater between populations, but both phenomena often interact. These results show the relevance of long-term observations, still quite rare, in order to interpret spatial and temporal variations in the bionomics of iteroparous species.[Journal translation]

Cycle de développement, croissance et production de Pisidium amnicum (Mollusca: Bivalvia) dans le Saint-Laurent (Québec)

1981 ◽  
Vol 59 (12) ◽  
pp. 2350-2359 ◽  
Author(s):  
B. Vincent ◽  
G. Vaillancourt ◽  
N. Lafontaine
Keyword(s):  
Population Dynamics ◽  
Sexual Maturity ◽  
Dry Weight ◽  
Mortality Rates ◽  
The Other ◽  
Annual Production ◽  
Bithynia Tentaculata ◽  
The Mean ◽  
Total Dry Weight ◽  
St Lawrence River

The population dynamics of Pisidium amnicum have been studied in one population of the St. Lawrence River over a 2-year period during which 19 samples were taken. The species can live up to 3 years and it is iteroparous; individuals generally attain sexual maturity after 1 year and they reproduce twice, once at 2 and once at 3 years of age. In adults, mortality is lower in winter than during the rest of the year and mortality rates are twice as high during the 1st year than during the 2nd year. Total dry weight (PT, in milligrams) is related to maximum length (L, in millimetres) according to the equation PT = 0.0283∙L3,80 and flesh dry weight (PC, in milligrams) is related to length as follows: PC = 0.007∙L3,18. The annual production to mean biomass (P/B) ratio is 1.4, the mean annual production being 1.298 mg/m2 of total dry weight and 107 mg/m2 of flesh weight. Comparing these results with those obtained for the gastropod Bithynia tentaculata in the same environment and at the same period of the year has shown that the growth of Pisidium amnicum is far less influenced by the temperature regime than that of the other species and that its production is at least 10 times lower.

Cycle de développement, croissance, effectifs, biomasse et production de Bithynia tentaculata L. (Gastropoda : Prosobranchia) dans le Saint-Laurent (Québec)

1981 ◽  
Vol 59 (7) ◽  
pp. 1237-1250 ◽  
Author(s):  
B. Vincent ◽  
G. Vaillancourt ◽  
M. Harvey
Keyword(s):  
Life Cycle ◽  
North America ◽  
Reproductive Strategy ◽  
Sexual Maturity ◽  
Individual Growth ◽  
Bithynia Tentaculata ◽  
St Lawrence River

The life cycle of Bythinia tentaculata has been studied over a period of 2 years in five localities of the freshwater estuary of the St. Lawrence River. Sexual maturity is attained after 2 years and the species is iteroparous; this might prove to be a particularly advantageous reproductive strategy in this river. The main phases of individual growth are related to age and thermal variations of the water and they occur during the months of May, June, and July of the first 2 years. Eggs are laid once a year and growth stops during winter for about 6 months. These results on the life cycle and growth of B. tentaculata, particularly in the fluvial section of the St. Lawrence River, are more similar to those obtained in Europe than to those obtained elsewhere in North America. Numbers, biomass, and production are markedly higher here than the values found by other investigators on the same species.[Journal translation]

scholarly journals The composition and heterogeneity of the rich and diverse rotifers (Rotifera: Eurotatoria) of the floodplain lakes (beels) of the Majuli River Island, Assam State (Northeast India)

2021 ◽  
Vol 52 (2) ◽  
pp. 165-181
Author(s):  
Bhushan Kumar Sharma ◽  
Sumita Sharma
Keyword(s):  
Abiotic Factors ◽  
Regional Distribution ◽  
Hard Water ◽  
Temporal Variations ◽  
Northeast India ◽  
Floodplain Lakes ◽  
Brahmaputra Basin ◽  
Spatio Temporal ◽  
The Rich ◽  
The Tropics

The tropical and subtropical floodplain lakes are hypothesized as one of the globally interesting rotifer rich ecosystems. Our study indicating the biodiverse Rotifera of ten ‘slightly acidic to circum-neutral, moderately hard-water and de-mineralized’ tropical floodplain lakes (beels) of the Majuli River Island of the Brahmaputra river basin of northeast India mendorses this hypothesis. Total richness, the richness of important families and community similarities affirm heterogeneity mof the rotifer species composition amongst the beels. The species richness registers significant spatio-temporal variations with seasonal differences amongst the beels and individually in each beel, and lacks significant influence of the recorded abiotic factors. The constellations of 76-81 species in three beels during winter and 76 species in one beel during pre-monsoon are noteworthy instances of ‘Rotifera paradox’. The rotifer fauna of the Majuli beels registers affinity with Southeast Asian and Oriental faunas, records several species of the regional distribution interest and exhibits the littoral-periphytic nature, while application of Q B/T and Q L/B quotients depicts limitations. This study merits ecological diversity interest for Rotifera vis-avis the floodplain lakes of India and elsewhere from the tropics and subtropics, and assumes biodiversity conservation importance due to threat of extinction of the Majuli – an alluvial floodplain of the Brahmaputra basin.

scholarly journals Die invloed van ouderdom op die komposterings - koers van organiese materiaal deur Eisenia fetida (Oligochaeta)

1995 ◽  
Vol 14 (4) ◽  
pp. 111-113
Author(s):  
Editorial Office
Keyword(s):  
Life Cycle ◽  
Environmental Factors ◽  
Age Structure ◽  
Eisenia Fetida ◽  
Sexual Maturity ◽  
Organic Waste ◽  
Optimal Conditions ◽  
Population Densities ◽  
Maximum Peak

One of the main objectives of a vermicomposting plant is to achieve a maximum composting rate of organic waste. Apart from population densities, substrate characteristics and environmental factors, age structure of the population is expected to affect the rate of composting. The composting rate of worms was studied in the laboratory under optimal conditions over a period of 55 days. Growth and sexual maturity were monitored as well as the composting rate during various stages of the life-cycle of Eisenia fetida. The composting rate was initially slow and reached a maximum peak when the worms were pre-clitellate.

Influence of temperature on the occurrence and distribution of the sand shrimp Crangon septemspinosaSay, 1818 (Decapoda: Caridea: Crangonidae) in polyhaline lagoons in Maryland, USA

2019 ◽  
Vol 39 (5) ◽  
pp. 586-593
Author(s):  
Paulinus Chigbu ◽  
Lauren Malinis ◽  
Hector Malagon ◽  
Steve Doctor
Keyword(s):  
Dissolved Oxygen ◽  
Relative Abundance ◽  
Linear Models ◽  
Abiotic Factors ◽  
Temporal Variations ◽  
Mean Temperature ◽  
Early Fall ◽  
Spatio Temporal ◽  
Maryland Coastal Bays ◽  
Chincoteague Bay

Abstract Sand shrimp, Crangon septemspinosaSay, 1818, is one of the most abundant decapod crustaceans in estuaries and coastal waters of the northwestern Atlantic Ocean, though little is known about its population dynamics in polyhaline lagoons of the mid-Atlantic region. Seasonal and spatial patterns of abundance and distribution of C. septemspinosa were evaluated in relation to temperature, salinity, and dissolved oxygen in Maryland coastal bays (MCBs) using monthly data (April to October 1994 to 2012). We tested the hypothesis that temperature influences the occurrence and distribution of sand shrimp in the lagoons. A consistent pattern of high relative abundance of shrimp in spring and its scarcity in summer and early fall was observed. Shrimp abundance was highest in the northern bays and at sites closest to the Ocean City Inlet during April, but lowest at sites in the upper parts of Chincoteague Bay and MCBs tributaries. As mean temperature increased from April (12.2–17.1 oC) to June (21.8–26.7 oC), the relative abundance of the shrimp decreased substantially at most sites except at two sites where mean water temperature was comparatively low (21.8–23.3 oC). By July, when mean temperature was at its maximum (23.1–28.9 oC) in the bays, shrimp were rarely caught in trawls even in early fall in spite of the decline in temperature. It is likely that shrimp moved into nearshore waters with cooler temperature or suffered high mortality due to high temperature during this period. Generalized linear models suggest that temperature, and temperature and dissolved oxygen combined, were the most important abiotic factors examined that influenced the spatial distribution of C. septemspinosa in May and June, respectively. Considering their trophic importance, the spatio-temporal variations in the occurrence and abundance of the shrimp have implications for food web dynamics in the MCBs.

Spatio-temporal variations of winter wheat water requirement and climatic causes in Huang-Huai-Hai Farming Region

2012 ◽  
Vol 20 (3) ◽  
pp. 356-362 ◽  
Author(s):  
Xiao-Lin YANG ◽  
Zhen-Wei SONG ◽  
Hong WANG ◽  
Quan-Hong SHI ◽  
Fu CHEN ◽  
...  
Keyword(s):  
Winter Wheat ◽  
Temporal Variations ◽  
Water Requirement ◽  
Spatio Temporal
Sign in / Sign up

Export Citation Format

Share Document