Patterns of Budding in the 

 Freshwater Hydroid Craspedacusta 



Charles F. Lytle- 



Dcpartment of Zoolofiy, Indiana University, Bloominp.t()n, Indiana 



Craspedacusta sowerbii Lankester is a freshwater hydrozoan 

 observed sporadically in many lakes, ponds, quarries, and im- 

 poundments of North America. It is best known for its conspicuous 

 medusa stage (Fig. 1), although the life cycle also includes a 

 nearly transparent polyp stage, which is microscopic and devoid of 

 tentacles. These polyps are attached permanently to various sub- 

 merged objects and grow as single hydranths or more commonly 

 as small colonies of two to seven simple hydranths joined at their 

 base (Fig. 2). There is no investing perisarc on the hydranths of 

 C. sowerbii though a loose case of detritus can usually be seen 

 around the basal portion of the hydranths and the base of the 

 colony. This detritus is held by a mucous secretion of the epidermal 

 cells. 



An individual hydranth is typically flask-shaped and measures 

 approximately 0.3-0.5 mm. in length, while a colony composed of 

 several hydranths may reach an overall diameter of two to three 

 millimeters. The hydranths may be divided roughly into four 

 regions: 1) a distal capitulum bearing several dozen nematocysts; 

 2) a constricted neck region; 3) expanded budding region; and 



^This paper is contribution No. 706 from tlie Department of Zoology, Indiana Uni- 

 versity and is based on a portion of a thesis submitted to the faculty of Indiana 

 University for the Ph.D. degree. This investigation was supported in part by a pre- 

 doctoral fellowship CF-8674 from the National Cancer Institute, United States 

 Public Health Service. 



2 Present address: Department of Zoology, Tulane University, New Orleans 18, 

 Louisiana. The author wishes to express his appreciation for the guidance and 

 support of Drs. Sears Crowell and Robert Briggs. 



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