Relating Zooid and Colony Growth in Modular Organisms Arborescent Cheilostome Bryozoans

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9306729 Lidgard Unlike solitary animals such as dogs or cats, bryozoans are animal colonies. Each colony is made up of tens or even thousands of modules called zooids. The zooids within a colony often differ from one another in form, but share a similar kind of growth by budding from pre-existing zooids. This colonial organization thus introduces variation and complexity not found in the growth of solitary animals. Different arrangements of zooids and different budding processes allow bryozoan colonies to grow into a remarkable variety of forms, including vines, sheets, mounds and miniature "trees". Bryozoans are among the most diverse groups of bottom dwelling animals in marine and freshwater habitats. Yet skeletal anatomy related to budding and colony formation is unknown for many encrusting and most erect bryozoans because no broadly based study has been attempted. The purpose of this research is to analyze zooid and colony growth among tree-like cheilostome bryozoans and to fill critical gaps in neglected areas of cheilostome morphology. These comparative studies will allow (a) evaluation and extension of previous growth models based on studies of encrusting colonies to include newly recognized patterns in erect colonies, (b) assessment of the taxonomic distribution of characters related to zooid and colony growth, and (c) documentation of relationships among zooid form and budding patterns and colony form. Light microscopy and scanning electron microscopy will be used to compare growth patterns in both living and fossil groups. %%% Bryozoans are interesting and poorly understood colonial animals. What appears to be a single "tree-like" form may actually consist of thousands of individuals. This project will study patterns of colony growth both in living and fossil forms of these animals. Insights will be provides for a major group of animals whose higher level relationships are poorly resolved and whose fossil record contains muc h of the known diversity. ***