Journal of Plankton Research Volume 4 Number 1: 143-153 1982

Skidaway Institute of Oceanography, P.O. Box 13687, Savannah, GA 31406, USA
(Received June 1980; accepted June 1981)

Abstract. Laboratory experiments are reported which provide information on culture conditions, mortality, fecundity and growth of Thalia democratica and Dolioletta gegenbauri in relation to simulated environmental conditions. Thaliaceans were maintained in laboratory culture at 20ºC. Culture vessels were 2.5 1 glass bottles. Diets consisted of Isochrysis galbana and Peridinium trochoideum, offered alone or together at total concentrations of 0.25 to 0.70 mm³ x l ¬¹. Laboratory released aggregate stages of Thalia were maintained for one week and gonozooid, phorozooid and oozooid stages of Dolioletta were reared for up to three weeks with daily mortality rates of 5 - 10%. There was no effect of diet on mortality rate. Thalia did not reproduce sexually but Dolioletta did routinely. Each Thalia solitary released a mean (± SE) of 54 ± 8 aggregates of 1. 1 - 2.1 mm length. Each Dolioletta gonozooid produced 2 - 6 larvae 0. 6 - 1.2 mm long, and each phorozooid released a mean of 31 ± 11 gonozooids. Aggregate growth was exponential for 7 days, with daily exponential growth coefficients (k) ranging from 0.03 - 0.36. Gonozooids grew exponentially for 17 days with a range of k from 0.08 - 0.25, and phorozooids grew exponentially for 5 days with k ranging from 0. 17 - 0.69. There was no effect of food concentration on k. Generation times of Thalia and Dolioletta were estimated to be from 3 - 6 weeks. These are probably maximum generation times for these two species in the Georgia Bight.