Grazing and assimilation rates of natural populations of planktonic rotifersKeratella cochlearis, Keratella quadrata andKellicottia longispina in a eutrophic lake (Aydat, France)

Hydrobiologia ◽  
1990 ◽  
Vol 194 (2) ◽  
pp. 119-131 ◽  
Author(s):  
Nicole Lair ◽  
H. Oulad Ali
Keyword(s):  
Natural Populations ◽  
Eutrophic Lake ◽  
Keratella Quadrata

Birth rate of planktonic rotifers in relation to food concentration in a shallow, eutrophic lake in western Canada

1979 ◽  
Vol 57 (6) ◽  
pp. 1206-1214 ◽  
Author(s):  
Robert L. Baker
Keyword(s):  
Birth Rate ◽  
Environmental Parameters ◽  
Eutrophic Lake ◽  
Food Concentration ◽  
Western Canada ◽  
Birth Rates ◽  
Keratella Cochlearis ◽  
Shallow Eutrophic Lake ◽  
Keratella Quadrata ◽  
Planktonic Rotifers

Population dynamics and birth rates of Keratella quadrata, Keratella cochlearis, Keratella earlinae, Pompholyx sulcata, and Brachionus angularis were studied in a shallow eutrophic lake of western Canada during 1975–1976. The Keratella species were collected throughout the year with maximum population densities in spring and fall. Pompholyx sulcata and B. angularis were common only during summer months.An extensive correlation analysis involving 'lagged' variables was performed to ascertain relations between birth rates and environmental parameters (temperature and food). Birth rates of all five species were positively correlated with temperature. Concentrations of certain phytoplankton (Rhabdomonas, Rhodomonas, Chlamydomonas, and Ankistrodesmus) were positively correlated with Keratella birth rates. Birth rates of K. cochlearis and P. sulcata were positively correlated with concentration of bacteria. Correlations involving 'lagged' variables were often different from those using 'simultaneous' variables.

High-voltage electron microscopy of maxillary gland of spirochete-infected brine shrimp: lesion of efferent tubule

1988 ◽  
Vol 46 ◽  
pp. 362-363
Author(s):  
G. E. Tyson ◽  
M. J. Song
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Brine Shrimp ◽  
Natural Populations ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Infected Adult

Natural populations of the brine shrimp, Artemia, may possess spirochete- infected animals in low numbers. The ultrastructure of Artemia's spirochete has been described by conventional transmission electron microscopy. In infected shrimp, spirochetal cells were abundant in the blood and also occurred intra- and extracellularly in the three organs examined, i.e. the maxillary gland (segmental excretory organ), the integument, and certain muscles The efferent-tubule region of the maxillary gland possessed a distinctive lesion comprised of a group of spirochetes, together with numerous small vesicles, situated in a cave-like indentation of the base of the tubule epithelium. in some instances the basal lamina at a lesion site was clearly discontinuous. High-voltage electron microscopy has now been used to study lesions of the efferent tubule, with the aim of understanding better their three-dimensional structure.Tissue from one maxillary gland of an infected, adult, female brine shrimp was used for HVEM study.

Effect of acid deposition on trichome morphology and dogwood anthracnose biology

1992 ◽  
Vol 50 (1) ◽  
pp. 840-841
Author(s):  
Kyle T. Thornham ◽  
R. Jay Stipes ◽  
Randolph L. Grayson
Keyword(s):  
Acid Deposition ◽  
Disease Incidence ◽  
Natural Populations ◽  
Tree Disease ◽  
Flowering Dogwood ◽  
Discula Destructiva ◽  
Disease Induction ◽  
Dogwood Anthracnose ◽  
Trichome Morphology ◽  
Precipitation Events

Dogwood anthracnose, caused by Discula destructiva (1), is another new catastrophic tree disease that has ravaged natural populations of the flowering dogwood (Cornus florida) in the Appalachians over the past 15 years, and the epidemic is prognosticated to continue (2). An estimated 9.5 million acres have been affected, primarily in the Appalachian Mountains, from VA southwards, alone, and an estimated 50% of all dogwoods in PA have been killed. Since acid deposition has been linked experimentally with disease induction, and since the disease incidence and severity are more pronounced at higher elevations where lower pH precipitation events occur, we investigated the effect of acidic foliar sprays on moiphologic changes in the foliar cuticle and trichomes (3), the initial sites of infection and foci of Discula sporulation.

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