CHAPTER III 



ECTOPARASITIC PROTOZOA 



By 



B. D. Reynolds 

 The University of Virginia 



Many different protozoa may be found living on the external 

 surfaces of aquatic plants and animals. Most of these use their 

 hosts merely as a perch or conveyance ; this relation may be asso- 

 ciated with commensal habits. In some cases, the protozoa may 

 accumulate in such numbers as to block the ready progress of their 

 host. On the other hand, there are a few protozoa which live on 

 the external surfaces as real parasites. Representatives of the first 

 group will be referred to as epizoic protozoa to signify that they 

 are not parasitic in a strict sense. 



]\Iost epizoic forms belong to the primitive flagellates, peri- 

 trichous ciliates, or suctoria. Usually they are either pedunculated 

 or sessile, though some that are placed in the group are capable 

 of moving freely over the surface of their host. Xo special effort 

 has been made to list all of the forms which have been reported 

 and only one species is given for each genus. Some of the genera 

 contain a large number of epizoic species. Some doubtful forms 

 have been omitted purposely; others, such as the chytridiace^, 

 do not properly belong in this group. The sporozoa have been 

 omitted because they are primarily tissue parasites. 



Epizoic protozoa live in both fresh and salt water and have been 

 found attached to practically all animals occurring in these habitats. 

 They are especially abundant on Crustacea, particularly so on the 

 genera Gammarits and Cyclops. Only a few references are given to 

 papers dealing with these forms. Of those given, special attention 

 is called to the works of Kent (1880-1882), Collin (1911-1912) 

 and Swarczewsky (1928). 



In the following list some of the epizoic protozoa are given, 



II 



