THE TIDAL RHYTHM OF THE DIATOM HANTZSCHIA AMPHIOXYS

Abstract

A sand-dwelling population of H. amphioxys is descr., which exhibits a tidal rhythm that persists for some days when held without tide in the laboratory. This rhythm is characterized by periodic inversion of phototropism, and by agglutination of the members when in the photophobic state. A comparison of this behavior with that of Euglena limosa, Chromulina psammobia and Strombidium oculatum shows close analogies and suggests that the same explanation may account for the synchronization of physiological rhythm and tide in all cases. It may be that the rising tide acts as a selective factor. Organic substances produced by the diatoms contribute to the structural stabilization of the superficial sandy layer, and the presence of this organic material appears to be an ecological condition essential to the interstitial microfauna.