FRESHWATER SPONGE 



There is a single family of freshwater sponges, the Spongillidae. 

 These are simple animals with bodies made up of unspecialized tissue 

 without specific organs, consisting of a maze of interconnected 

 channels, chambers, and orifices. The support or skeleton of the animal 

 is mainly made up of random groups of needlelike siliceous bodies 

 called spicules (insert 1) surrounded by gelatinous masses and 

 sometimes a horny fiber called spongin. Spongin is the material that 

 makes up the body of the commercial marine sponge. The spicule is 

 useful in identifying this animal. 



The freshwater sponge is usually brown or yellowish in color; 

 occasionally the animal has a greenish cast. This green coloration is 

 produced by the unicellular algae that exist in the many chambers and 

 channels of the sponge body and provide a food source for the animal. 

 Water containing food materials is circulated through the many pores 

 of the sponge by movement of threadlike projections or flagella. 



The size of the freshwater sponge is variable, depending on location 

 and species. The sponge may be merely a slimelike or delicate mat 

 becoming encrusted with the numerous outgrowths and branches; or, 

 when new animals grow from year to year over the old, dead skeletons, 

 the encrustation may attain considerable size. 



The animal is able to regenerate with a few cells, often 

 overwintering in a perennial habit. The freshwater sponge produces 

 a highly resistant resting body, or "gemmule" (insert 2), that is quite 

 similar to the "statoblast" of Bryozoa. 



These animals are often found growing in clear, still water, and are 

 being reported with increasing frequency as attached (sessile) growths 

 in lined irrigation canals. 



Sponges in irrigation systems can cause considerable hydraulic 

 problems when growing in association with other aquatic animals and 

 plants. This undesirable effect is compounded by the favorable 

 substrate they create for invasion of a wide variety of other aquatic 

 pest organisms. 



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