Reproductive rates and periodicities of oceanic tintinnine ciliates

Tintinnine ciliates from 3 strata (40 m increments from the surface to 120 m depth) at a station in the oceanic North Pacific Ocean were sampled repeatedly through the day during a cruise in August-September 1984. Fourteen species were encountered in sufficient numbers to allow analysis of their diel periodic~ty and rates of reproduction. Species in the upper 2 strata (0 to 40 m, 40 to 80 m) consistently displayed 'clear' or 'probable' diel periodicity in division. &vision peaks occurred either near midnight (20:OO to 02:OO h local time) or during the afternoon (13:OO to 17:OO h). Conservative estimates of specific growth rates had a range of 0.017 to 0.027 h-' (generation times of 40.4 to 25.3 h). Data for 3 species were sufficiently well-developed to allow calculation of the duration of the recognizable division stages (8.3 to 9.5 h) and more precise estimates of specific growth rates (0.027 to 0.039 h-'). Species from the deepest stratum (80 to 120 m) displayed quite different reproductive behavior Periodicity was never clearly definable and, when probable, was relatively low in amplitude, although average percentages of dividing cells were similar to those noted for the upper 2 strata.