INVERTEBRATE AQUATIC 

 ANIMALS 



In addition to various types of aquatic plant life found in irrigation 

 systems, many small aquatic animals also present problems to water 

 distribution. These animal pests, being of a relatively low order in the 

 animal kingdom and therefore lacking an internal bone structure, are 

 referred to as invertebrate animals. The aquatic animals of this type 

 that create problems for the irrigation operator are submersed during 

 some portion of their life cycle, usually attaching to submerged water 

 structures or burrowing in the bottom mud of canals. Some of these 

 more commonly observed animals are: Bryozoans or pipe moss, 

 freshwater sponge, larvae of certain aquatic insects, and freshwater 

 clams. 



The problems that Bryozoa, sponge, and insect larvae create on 

 irrigation structures are similar in scope to those produced by attached 

 algae. These animals attach themselves to canal linings and other 

 submerged water structures, creating considerable obstruction to 

 waterflow. Also, the Bryozoa and sponge are often found growing 

 inside of pipes and enclosed water conduits. The freshwater clam, 

 while it does not attach to submerged water structures, does under 

 certain conditions grow and develop so prolifically as to reduce the 

 carrying capacity of a canal. Clams reduce the cross-sectional area of 

 a canal by aiding in the rapid development of silt bars on the canal 

 bottom. 



General descriptions of some of the typical invertebrate aquatic 

 animals found in irrigation systems are given in the following pages 

 to familiarize the reader with types that may be encountered. 



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