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| Dennert, H.G.; Maren, M.J. van. |
| The migration of G. zaddachi in La Slack, a small stream on the French Channel coast, and some physico-chemical properties of the river are discussed. In laboratory experiments, the influence of the Cl- and Ca++ concentration on the survival-rate and reproduction of G. zaddachi was investigated. A raise in the Cl- concentration of the medium caused a significant improvement of the survivalrate. A raise in the Ca++ concentration also gives, although not significant, a higher survival-rate. |
| Tipo: Article / Letter to the editor |
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| Ano: 1974 |
URL: http://www.repository.naturalis.nl/record/505269 |
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| Dennert, H.G.; Dennert, A.L.; Kant, P.; Pinkster, S.; Stock, J.H.. |
| 1. The real identity has been studied of juvenile gammarids, that were found in the fresh-water tidal region of the River Slack (France), 3 to 4 km inland of the mouth of its estuary. At the outset, these juveniles were (on basis of their morphology) considered to belong to Gammarus salinus. 2. Rearing demonstrated that the juveniles in question developed into adult Gammarus zaddachi. This indicates that the morphological criteria used in discriminating between G. salinus and G. zaddachi fail in juvenile material. Several morphological criteria are discussed and tested. It appears that a 100% certain key character does not exist, meaning that it is not possible to identify with absolute certainty all individuals in mixed populations of the two species. 3.... |
| Tipo: Article / Letter to the editor |
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| Ano: 1969 |
URL: http://www.repository.naturalis.nl/record/504231 |
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| Girisch, H.B.; Dennert, H.G.. |
| The migratory activity of Gammarus zaddachi and Gammarus chevreuxi is investigated in a current chamber, in which a tidal cycle can be simulated. In fresh running water the number of animals drifting with the current is of about the same magnitude as the number of animals actively swimming against the current. A diurnal periodicity is recorded in the migratory activity. The migratory activity is influenced by the population density and the food supply. In the current chamber a tidal cycle can be simulated by varying the factors current velocity, current direction, salinity, and temperature. The combination of a decrease in current velocity, followed by a slow current in the opposite direction, an increase in the salinity, and a rise in the temperature of... |
| Tipo: Article / Letter to the editor |
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| Ano: 1975 |
URL: http://www.repository.naturalis.nl/record/504600 |
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