Circadian respiratory biorhythm of marine gastropods <i>Natica maculosa</i>, <i>Umbonium vestiarum</i> and <i>Polynices didyma</i>

Abstract

Circadian respiratory biorhythm of the three gastropods was investigated and compared with that of bivalves under conditions identical to their tropical niche. The three marine gastropods conformed extremely well to the diurnal tidal rhythm similar to suspended sedentary bivalve, <i>Perna viridis</i> L. However, the maxima and minima were shifted by approximately 4 h respectively against the maximal high and minimal low tides. The shift by 4 h in maximal and minimal circadian respiratory activities corresponded to the receding and incoming tides, respectively. Comparison of maximal nocturnal respiratory activity against that of daylight maximal respiratory activity demonstrated the former to be greater by 39 and 48 % for <i>N. maculosa</i> and <i>U. vestiarum</i>, respectively, and for <i>P. didyma</i> by 25,22 and 26 % with increase in size (2.2, 2.8 and 3.2 cm).