The role of water in the behaviour of an estuarine mud-flat diatom.
Hopkins, J.T. (1966) The role of water in the behaviour of an estuarine mud-flat diatom. Journal of the Marine Biological Association of the United Kingdom, 46 (3). pp. 617-626.
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The tidal rhythm of migration of the mud-flat diatom community is a curtailed diurnal rhythm. Evidence is given of the similarity of these two oscillations in the laboratory and in the natural conditions of the estuary. However, the interference of the diurnal rhythm by water or stirring results only in one repeated rhythm on the following day; thereafter the migrations revert to a daylength- induced synchronization. Evidence of rhythms in geotaxy, phototaxy and motility is presented. Observations of undisturbed diatoms living in translucent particles show that movement only occurs at the migration periods. At these periods entrainment of geotaxy to the phototaxy has been described; the sign and strength of the phototaxy determines the direction of migration and the time of entrainment ofthe phototaxy and the geotaxy the period of the oscillation. The change from an afternoon to a morning upward migration occurs when the Surirella gemma community is wetted in darkness; in this situation the migration is a transient response and on the following day the migration rhythm reverts to one phased by daylength.
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