detrital and bacterial control
several marineciliates were isolated in an attempt to find a bottom grazer having no undesirable effects when associated, in culture, with Acartia. Euplotes vannus MÜLLER,a relatively large(about 75 u), hypotrichous ciliate, survived and reproduced well at 15 C the chosen temperature for continuous culture. Primarily a bottom feeder,this ciliate consumed a sufficient quantity of standard food organisms to prevent detrimental accumulation. Reduction in bacterial population was demonstrated in small flasks, and no bacterial slime was observed in experimental cope pod cultures. Eggs of Acartia rest singly on the bottom of the culture vessel until hatched. Although the clilates fed in the same vicinity, they apparently did not affect normal hatching. Dead cope pods quickly become engorged with bacteria, and ciliates could be seen crawling over their exoskeletal surfaces, apparently consuming bacteria liberated from the carcasses. Acartia fed on ciliate population and completed the nutrient cycle. Euplotes vannus is now included routinely in all continuous culture of Acartia spp. at this laboratory