Decomposers, Bacteria, and Microbenthos 377 



(Figure 8-13) while the majority of the ciliates in late June were algae 

 feeders. 



Among the important algae feeders were Nassula and Cryptogramma 

 sp. (both feed mainly on blue-green algae), Frotonia acuminata, F. leucas, 

 Prorodon teres, Strombidium sp. and a number of oxytrichids. Species of 

 Stentor, Stylonychia mytilus, and Euplotes patella grazed on algae but 

 also ate other ciliates and zooflagellates. The bacterivorous ciliates were 

 mostly small holotrichs such as Colpidium, Tetrahymena, and Tnmyema, 

 but two large forms, Spirostomum teres and Blepharisma lateritium, were 

 also common while Vorticella regularly occurred on particles of detritus. 

 The most important carnivorous ciliates were Lacrymaria sp., Dileptus 

 anser, Spathidioum sp., and a number of holophryids (e.g., 

 Pseudoprorodon sp.) which fed on zooflagellates and other ciliates. 

 Finally, the category "histophagous" in Figure 8-13 refers to ciliates that 

 specialize in attacking and eating damaged but living metazoans such as 

 oligochaetes and chironomids (Mugard 1949). This quantitatively 

 unimportant group was represented by Ophryoglena sp. and Coleps hirtus. 

 In general, the ciliate assemblage in this arctic pond is strikingly similar to 

 that of temperate freshwater ponds of similar sediment type (Bick 1958, 

 Picken 1937, Noland and Gojdics 1967). 



Rhizopods such as amoebae and testaceans are also present in the 

 sediments of the pond, but it is likely that the testaceans were washed in 



FIGURE 8-14. Nematodes in the center of Pond B, 1971 and 1973. 



