How often does conjugation in ciliates occur? Clues from a seven-year study on marine sandy shores

Abstract

Conjugation is a distinctive process of ciliate sexual reproduction, and while its induction and progression have been widely investigated in lab-cultured strains of several species, little information has been gathered about the actual frequency of this sexual process in natural habitats. This study focuses on the frequency of conjugation in ciliates dwelling on Mediterranean sandy shores. Over the period 1990 to 1996, 680 sand samples (1 ml) were collected along Italian coasts and examined just after collection for the presence of conjugating pairs. Overall, the samplings yielded 28 890 individual ciliates belonging to 121 species, but only 20 conjugating pairs belonging to 8 different species. Conjugation, therefore, seems to be an erratic sexual phenomenon and not as frequent in ciliates of temperate marine sandy shores as previously thought.