Structure en taille des crustacés planctoniques d'un lac dimictique du Bouclier canadien

1988 ◽  
Vol 66 (7) ◽  
pp. 1570-1577
Author(s):  
Lucie Martin ◽  
Bernadette Pinel-Alloul
Keyword(s):  
Seasonal Variation ◽  
Annual Cycle ◽  
Size Structure ◽  
Principal Coordinate Analysis ◽  
Size Spectra ◽  
Fall Season ◽  
Planktonic Crustaceans ◽  
Bouclier Canadien ◽  
Intermediate Linkage ◽  
Chronological Clustering

From May 1981 to July 1982, 28 zooplankton samples were taken from the pelagic zone of Lake Cromwell, Quebec. Seasonal variation in the size structure of the planktonic crustacean community was studied using three different multidimensional analyses: intermediate linkage clustering, principal coordinate analysis, and chronological clustering. The results of these analyses showed the existence of distinct patterns in the size distribution of planktonic crustaceans during the annual cycle. During winter, the community was dominated by intermediate-sized organisms (0.51–0.60 mm), and by a few of larger size (0.96 mm). In springtime, nauplii appeared, and the larger size classes were reduced, giving the size spectra a characteristic shape. Small organisms (0.06–0.22 mm) dominated the population throughout the summer. The fall season was characterized by the opposite observation: small organisms slowly decreased in number while the intermediate classes (0.51–0.60 mm) increased in number to reach their peak in winter. These size–frequency patterns may be related to varying food levels and composition throughout the year.

Alternate Changes in Birth Seasonality of Twins During 1971–1984 in Japan

1987 ◽  
Vol 36 (3) ◽  
pp. 373-380 ◽  
Author(s):  
I. Nakamura ◽  
Y. Amau ◽  
K. Nonaka ◽  
T. Miura
Keyword(s):  
Seasonal Variation ◽  
Birth Seasonality ◽  
Fall Season ◽  
Multiple Ovulation ◽  
Seasonal Factors ◽  
Inducing Factors

AbstractBirth dates of 1,536 twin-pairs in 1971-1984 were collected from the members of an association of twins' mothers. The seasonal variation of twinning changed every 2-4 years. Years when twinning rate was higher in the summer-fall season (1971-72, 1976-77, 1982-84) and those when a peak of the rate was not observed (1973-75, 1978-81) appeared alternately. In years with a summer-fall peak, the elevation of twinning in the summer-fall season was detected consistently in both like- and unlike-sexed and in both MZ and DZ twin groups. The twinning seasonality in these years, however, was not evident in twin births of mothers who were born in May-July. These results suggest the possibility that seasonal factors which influence the twinning rate be not multiple-ovulation-inducing but probably abortion-inducing factors and most likely seasonally epidemic microbes.

Shifts in plankton size spectra modulate growth and coexistence of anchovy and sardine in upwelling systems

2016 ◽  
Vol 73 (4) ◽  
pp. 611-621 ◽  
Author(s):  
T. Mariella Canales ◽  
Richard Law ◽  
Julia L. Blanchard
Keyword(s):  
Size Structure ◽  
Prey Availability ◽  
Empirical Work ◽  
Size Composition ◽  
Size Spectrum ◽  
Small Particles ◽  
Size Spectra ◽  
Factors Influencing ◽  
Spectrum Model ◽  
Model Scenarios

Fluctuations in the abundance of anchovy (Engraulis spp.) and sardine (Sardinops sagax) are widespread in marine ecosystems, but the causes still remain uncertain. Differences between the planktonic prey availability, selectivity, and predation between anchovy and sardine have been suggested as factors influencing their dynamics. Using a dynamical multispecies size-spectrum model, we explore the consequences of changes in plankton size composition, together with intraguild predation and cannibalism, on the coexistence of these species. The shift towards smaller plankton has led to a reduction in the growth rate of both species. The effect was more deleterious on anchovy growth because it is unable to filter small particles. In model scenarios that included the effects of cannibalism and predation, anchovy typically collapsed under conditions favouring smaller sized plankton. The two species coexisted under conditions of larger sized plankton, although strong predation in conjunction with weak cannibalism led to the loss of sardine. The model provides new testable predictions for the consequences of plankton size structure on anchovy and sardine fluctuations. Further empirical work is needed to test these predictions in the context of climate change.

Copepods size structure in various phases of a cold-core eddy - Normalised Abundance Size Spectra (NASS) approach.

2020 ◽  
Vol 206 ◽  
pp. 104197
Author(s):  
L. Jagadeesan ◽  
T.N.R. Srinivas ◽  
A. Surendra ◽  
G. Sampath Kumar ◽  
M.P Aswindev ◽  
...  
Keyword(s):  
Size Structure ◽  
Size Spectra ◽  
Cold Core

scholarly journals Seasonal migrations, body temperature fluctuations, and infection dynamics in adult amphibians

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4698 ◽  
Author(s):  
David R. Daversa ◽  
Camino Monsalve-Carcaño ◽  
Luis M. Carrascal ◽  
Jaime Bosch
Keyword(s):  
Seasonal Variation ◽  
Body Temperature ◽  
Annual Cycle ◽  
Batrachochytrium Dendrobatidis ◽  
Effective Means ◽  
The Body ◽  
Infection Prevalence ◽  
Body Temperatures ◽  
Annual Cycles ◽  
Prediction And Prevention

Risks of parasitism vary over time, with infection prevalence often fluctuating with seasonal changes in the annual cycle. Identifying the biological mechanisms underlying seasonality in infection can enable better prediction and prevention of future infection peaks. Obtaining longitudinal data on individual infections and traits across seasons throughout the annual cycle is perhaps the most effective means of achieving this aim, yet few studies have obtained such information for wildlife. Here, we tracked spiny common toads (Bufo spinosus) within and across annual cycles to assess seasonal variation in movement, body temperatures and infection from the fungal parasite, Batrachochytrium dendrobatidis (Bd). Across annual cycles, toads did not consistently sustain infections but instead gained and lost infections from year to year. Radio-tracking showed that infected toads lose infections during post-breeding migrations, and no toads contracted infection following migration, which may be one explanation for the inter-annual variability in Bd infections. We also found pronounced seasonal variation in toad body temperatures. Body temperatures approached 0 °C during winter hibernation but remained largely within the thermal tolerance range of Bd. These findings provide direct documentation of migratory recovery (i.e., loss of infection during migration) and escape in a wild population. The body temperature reductions that we observed during hibernation warrant further consideration into the role that this period plays in seasonal Bd dynamics.

Mysid Life History and Seasonal Variation in Predation Pressure on Zooplankton

1983 ◽  
Vol 40 (11) ◽  
pp. 1968-1974 ◽  
Author(s):  
Paul A. Murtaugh
Keyword(s):  
Life History ◽  
Seasonal Variation ◽  
Feeding Rate ◽  
Size Structure ◽  
Seasonal Fluctuations ◽  
Predation Intensity ◽  
Lake Washington ◽  
History Of ◽  
Relative Vulnerability

The bivoltine life history of Neomysis mercedis in Lake Washington, Seattle, results in seasonal variation in population size structure that influences the amount and quality of predation suffered by its zooplankton prey. Population densities and size–frequency data for Neomysis are combined with information on the influence of body size on feeding rate and composition of the diet to predict relative predation intensity on five size classes of Daphnia over a 27-mo period. An imperfect relationship between mysid numbers and expected predation intensity and seasonal fluctuations in the relative vulnerability of different-sized prey are two consequences of the mysid's pattern of life history.

scholarly journals Phytoplankton size structure, distribution, and primary production as the basis for trophic analysis of Caribbean ecosystems

2010 ◽  
Vol 68 (4) ◽  
pp. 751-765 ◽  
Author(s):  
Marie-Hélène Forget ◽  
Trevor Platt ◽  
Shubha Sathyendranath ◽  
Paul Fanning
Keyword(s):  
Primary Production ◽  
Annual Cycle ◽  
Size Structure ◽  
Marine Ecosystem ◽  
Chlorophyll Concentration ◽  
Remotely Sensed ◽  
Remotely Sensed Data ◽  
Phytoplankton Size ◽  
Trophic Analysis ◽  
Phytoplankton Size Structure

Abstract Forget, M-H., Platt, T., Sathyendranath, S., and Fanning, P. 2011. Phytoplankton size structure, distribution, and primary production as the basis for trophic analysis of Caribbean ecosystems. – ICES Journal of Marine Science, 68: 751–765. An oceanographic survey was conducted in Caribbean waters in April and May 2006 to assess the marine ecosystem in the context of a trophic analysis of the foodweb. Analyses of pigment and absorption data revealed that the phytoplankton community was dominated by pico- and nanophytoplankton, particularly at the deep chlorophyll maximum. Based on cluster analysis of remotely sensed data, three dynamic provinces were defined for the region. A 5-year time-series of sea surface temperature and chlorophyll concentration provided information on the annual cycle of these properties. To implement the computation of primary production on a synoptic scale, parameters characterizing the biomass profiles and photosynthesis–irradiance relationships were assigned using four protocols: two regional approaches, a regression with surface chlorophyll, and the nearest-neighbour method (NNM), which has the advantage of assigning parameters on a pixel-by-pixel basis. Monthly images of primary production were computed over an annual cycle using MODIS chlorophyll a concentration. The NNM and the use of dynamic provinces emerged as the methods of choice for parameter assignment. Finally, a new approach from remotely sensed data was developed to estimate production-to-carbon ratios, a key input to Ecopath models. The results contribute to ecotrophic analysis of the Lesser Antilles Pelagic Ecosystem project.

scholarly journals Seasonal variation in thyroid activity of turtle Lissemys punctata with respect to annual cycle of reproduction

2010 ◽  
Vol 2 (2) ◽  
pp. 194-199
Author(s):  
Vidya R. Chandavar ◽  
Prakash R. Naik
Keyword(s):  
Seasonal Variation ◽  
Reproductive Cycle ◽  
Annual Cycle ◽  
Seasonal Cycle ◽  
Maximum Size ◽  
Reproductive Period ◽  
Thyroid Activity ◽  
The Relationship

The objective of the present investigation was to study the relationship between thyroid activity and reproductive cycle in turtle Lissemys punctata. The animals were studied in the annual seasonal cycle of reproduction for two consecutive years, which is distinguished into three separate periods namely regenerative, reproductive and recrudescent. The thyroid in L. punctata was observed to be a single pyramid shaped gland, creamy white to reddish-brown in color with lenticular profile. The diameter of the follicle was lowest in regenerative period, whichgradually increased in reproductive period attaining maximum size in recrudescent, where as epithelial height was highest in regenerative period, which gradually decreased in reproductive period reaching minimum in recrudescent period. Thyroid activity varies annually in relation to different phases of reproductive periods.

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