Daily actyivity rhythm of two Mediterranean Lamellibranchs (Pecten Jacobaeus and Lithophaga lithophaga) regulated by light-dark period

Salánki, János (1966) Daily actyivity rhythm of two Mediterranean Lamellibranchs (Pecten Jacobaeus and Lithophaga lithophaga) regulated by light-dark period. A Magyar Tudományos Akadémia Tihanyi Biológiai Kutatóintézetének évkönyve, 33. pp. 135-142. ISSN 0365-3005

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Abstract

The rhythmic activity of the closer muscles of Pecten and Lithophaga was recorded and a daily rhythm in the amplitude and frequency of the contractions as well as a difference in the degree of opening of the valves was established. The daily rhythm depends on the illumination changes and can be shifted by lengthening the light or dark periods. It is concluded that basic functions of the well developed eyes of Pecten and the primitive dermal photoreceptors of Lithophaga do not differ from each other from the viewpoint of regulation by light-dark periodicity. This means that primitive photoreceptors are also capable of perception of long-term light and dark changes. It seems probable that the effect of illumination realizes, through the receptors, on the tonus-and rhythm-regulating centre of the nervous system, which latter in the absence of external periodicity do not have a diurnal “clock” mechanism.

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