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1
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Toxic effect of cyanobacterial blooms on the grazing activity of Daphnia magna Straus

100%
Lotocka M.
Oceanologia
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2001
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tom 43
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nr 4
The investigations aimed to determine the impact of cyanobacteria Microcystis aeruginosa (K¨utz.) K¨utz. and Aphanizomenon flos-aquae (L.) Ralfs ex Bornet et Flah., both toxic algae, on the grazing intensity of Daphnia magna Straus. In order to determine the parameter permitting the quantitative determination of the grazing intensity of herbivorous organisms, methods based on the following techniques were applied: microscopy, to determine the degree of gut fullness; spectrophotometry, to determine the levels of chlorophyll a and its degradation products in the food composition; high-performance liquid chromatography (HPLC) to determine the content of exogenous and endogenous carotenoids. Each of these methods confirmed that the tested algae species inhibited grazing intensity in D. magna Straus. The most obvious effects were obtained when M. aeruginosa (K¨utz.) K¨utz. was used as food. With these cyanobacteria, the gut fullness indicator did not exceed 58%, and the chlorophyll a content in the digestive system of the tested D. magna was three times lower than that in the control organisms. It seems that the defensive reaction of organisms was a reversible process. However, the possibility of a long-term, sublethal influence of cyanobacteria on the physiology and internal processes of this species cannot be ruled out.
2

Reproductive parameters, kidney fat index, and grazing activity relationships between the sexes in Cantabrian chamois Rupicapra pyrenaica parva

100%
Perez-Barberia F. J., Mutuberria G., Nores C.
Acta Theriologica
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1998
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tom 43
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nr 3
Reproductive parameters, kidney fat index and grazing activity of both sexes of Cantabrian chamois Rupicapra pyrenaica parua (Cabrera, 1910) in relation to age, season and year are presented and compared with those of other chamois subspecies and cervids. Females younger than three years old had not ovulated. Ovulated ovaries were significantly heavier than non-ovulated ovaries in March-April, and these dif­ferences remained until the following rutting season. All pregnant females carried a single foetus. A significant decrease in the percentage of parous females was found in 3-11 years age class (94%) compared with > 11 years (50%). There were no differences in the kidney fat index (KFI) between age classes for either of the sexes throughout the study period. Females showed a significant higher KFI in August­-October 1993 than in August-October 1992, coinciding with a significantly greater abundance of grass in 1993. Throughout the year KFI in females showed less fluc­tuations than in mates. Males began the rutting season with a significant KFI three times higher than did females. However, by the spring, the KFI of the mates had fallen to half of that of the females. In March-April pregnant females showed a significantly higher KFI than non-pregnant or late-conception adult females. Feeding activity of females and sward height throughout the year were inversely related. Females grazed more actively than males in the summer, rut and spring, except in winter where no differences in feeding activity between sexes were found. The dif­ferences in the KFI and feeding activity are discussed in relation to the parental investment and the sexual dimorphism-body size theory.
3
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The effect of temperature and humidity on the grazing activity of Deroceras reticulatum (O. F. Muller, 1774) and the damage to rape plants

80%
Kozlowski J., Jaskulska M., Kaluski T., Kozlowska M.
Folia Malacologica
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2011
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tom 19
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nr 4
Winter rape is susceptible to damage caused by D. reticulatum (O. F. Müller) mainly in the early phases of the plants’ development. The degree of damage and the size of yield losses depend on the slug population and the grazing activity, which are governed by many environmental factors. Laboratory studies were performed to analyse the rate and amount of damage to rape plants (2–3 leaf stage) caused by D. reticulatum, and the effect of temperature and soil humidity on the slug’s grazing activity. With increasing air temperature (up to 16°C) the amount of damage increased, but the effect was not lasting. The slugs were also active at low temperatures (+1°C), and although their grazing was less intense, the amount of damage after seven days could reach an average of 34%. In laboratory tests, the soil humidity had no marked effect on the amount of damage done by the slugs.
4

Grazing effects of alien amphipods on macroalgae in the littoral zone of the Neva Estuary [Eastern Gulf of Finland, Baltic Sea]

80%
Berezina N., Golubkov S., Gubelit J.
Oceanological and Hydrobiological Studies
|
2005
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tom 34
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nr Suppl.1
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