CHAPTER XIX 



AQUATIC EARTHWORMS AND OTHER 

 BRISTLE-BEARING WORMS 

 (CHAETOPODA) 



By frank smith 

 Professor of Systematic Zoology and Curator of the Museum of Natural History, University of Illinois 



Earthworms, with their flexible segmented bodies and four 

 double rows of bristles, or setae, are objects familiar to all students 

 of animal life. Although most species are terrestrial there are also 

 aquatic ones and these are abundantly represented in our fresh 

 waters. Closely related to the earthworms ar.d similar in structure 

 are numerous other worms which are essentially aquatic. These 

 also, with certain exceptions, are provided with setae and are 

 included with earthworms in the group Oligochaeta. The setae- 

 bearing worms of the sea (Polychaeta) commonly bear the setae on 

 lateral muscular outgrowths of the body wall, the parapodia. The 

 Oligochaeta and Polychaeta collectively are often referred to as the 

 Chaetopoda. 



The Chaetopoda, Hirudinea (leeches), and certain strictly marine 

 worms which are not under consideration here, are included in the 

 phylum Annelida. 



Fresh-water Polychaeta 



Although the Polychaeta are essentially marine in habit, a few 

 species in various parts of the world have become adapted to 

 fresh-water conditions. Manayunkia speciosa Leidy is foimd in 

 the Schuylkill River and in other fresh-water situations near Phila- 

 delphia, and Johnson has described two fresh-water species from 

 the western coast region, — Nereis limnicola Johnson from Lake 

 Merced, near San Francisco, and Lycastoides alticola Johnson from 

 Lower California. 



These are stray intruders from the rich, marine fauna of this 

 group in adjacent salt water, and none have yet been discovered 



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