Sididae and Daphniidae 207 



Families sididae and daphniidae 



CULTURE OF CLADOCERA 



A. M. Banta, Brown University 



THESE small animals are useful as food for cultures of hydra, young 

 and older aquarium fish, and larval salamanders. More directly as 

 scientific material, they are very useful for laboratory teaching and 

 for research purposes. 



They provide a favorable laboratory type for illustration of the struc- 

 ture of an entomostracan for which, because of their transparency, they 

 may readily be used alive to demonstrate most of the morphological 

 structures and in addition several physiological activities (respiration 

 feeding and egestion, circulation, reproduction). They are also ad- 

 vantageous for the study of animal behavior, adjustment to environment 

 adjustment to the annual seasonal cycle, etc. They are unexcelled for 

 the study of parthenogenetic reproduction and the environmental control 

 of sex of offspring. 



As material for physiological studies or experimentation a clone of 

 cladocerans provides the almost unique advantage of genetic uniformity, 

 which is practically guaranteed by their diploid parthenogenetic repro- 

 duction. 



For studies in the genetics of a pure line or clone they are probably 

 unequalled among metazoans. Also, thanks to the technique developed 

 by Miss Thelma R. Wood, they may be used for studies of genetics in 

 sexual reproduction, an essential supplement to the analysis of the genetics 



of the clone. 



Live animals with which to start cultures may ordinarily be obtained 

 from small ponds or lakes during the open season and frequently through 

 the ice in winter. Daphnia longispina and the species of Simocephalus 

 may be secured in moderate numbers in many sections the year round. 

 Simocephalus also occurs occasionally in dense vegetation in relatively 

 quiet portions of freshwater streams. Daphnia pulex is frequently 

 abundant especially in spring and early summer in clear and often in 

 rather dirty pond water. The species of Moina are found in late spring 

 and summer in pig-lot or stable-yard puddles and in other situations 

 where the content of organic matter in the water is high. 



The essential food of most Cladocera is bacteria or single-celled, not 

 filamentous, algae. For Daphnia magna, algae are sometimes more 

 advantageous than bacteria although usually D. magna does very well in 

 manure culture medium. But for the other species of Daphnia, for 

 Simocephalus, and some of the Sididae, bacteria seem equally good or 

 better. For Moina, bacteria of the colon group (which generally prevail 



