Alternating bryozoan

Amathia alternata

Family Vesiculariidae - bryozoans

Colony of polyps; branching, bushy, erect; color brownish to yellowish; branching appears somewhat undulating or twisted; branching is bifurcate (splits into 2 branches at each node); tubular polyps called zooids in short, double rows along branches (stolons); zooid rows straight or spiraled at up to a 90° angle along stolons; alternate double rows oriented at about 180° from each other on stolons and nearly touching each other; no extra extensions (terminal processes) at the end of each stolon (past the last zooid row).
Similar Species
Other similar bryozoans have different degrees of zooid spiraling around the stolon, usually greater than 100° (only 0-90° in A. alternata). Other bryozoans may also have more than 2 branches at each node (3 or 4), extensions (terminal processes) at the end of each branch (past the last zooid), and zooid rows that are oriented approximately 30° from each other (about 180° in A. alternata) and are much further apart (not nearly touching).
Gulf and bay, usually attached to a substrate, hardened or otherwise
Maximum Size
30 cm (12 in)
Other Common Names
Previous Scientific Names