Zur Lokomotionsaktivität des Amphipoden Orchestia platensis im Freiland und im Laboratorium

Abstract

The daily locomotory activity of Orchestia platensis (Kröyer) was recorded in situ and under constant conditions in the laboratory. The equipment for automatical recording is described. The species is very abundant along the coast of the Baltic Sea (non-tidal conditions). It only propagates for about half a year (April-October, Bock 1967). During this time the adults have a nocturnal activity; thus the time of ecological activity is very limited. Not every night suits Orchestia: severe darkness, rain, low temperature and wind, depress their activity. As a result, only about 10% of the total life-span of Orchestia can be utilized for feeding, propagation and other ecologically important functions. Further difficulties arise from catastrophies in the biotope of Orchestia: inundation or desiccation cause mass emigrations even during the day, when predators are active. Therefore losses are very high. Orchestia adapts to these conditions by at once utilizing favourable conditions. An endogenous component of their activity can be easily revealed by studies under constant conditions but is practically of no importance in the natural biotope. An endogenous pattern of activity, as in mammals or birds, is therefore not discernible. © 1967 Biologischen Anstalt Helgoland.