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Date of Award


Document Type


Degree Name

Master of Science (M.S.)


Biological Sciences

First Advisor

John S. Tucker

First Committee Member

Edmund H. Smith

Second Committee Member

Victor Loosanoff


Adula (Botula) falcata Gould (Soot-Ryen, 1955) lives commonly as a byssally attached rock borer in soft mudstone reefs at Bolinas and Moss Beach, California (Figure 1). Keen (1963) reports that Adula falcata has been collected from the intertidal to a depth of ten fathoms. Its distribution is from Coos Bay, Oregon, to Cape San Lucas, Lower California (Hertlein and Strong, 1946), and collection data indicate a range as far south as Peru (Soot-Ryen, 1955).

While is possesses the protective advantage of living cryptically, Adula falcata is subjected to an environmental stress not faced by epifaunal mytillids; namely, it must function within a burrow into which sediment material is being continuously deposited from both particle laden water passing over its burrow entrance and the mudstone byproducts of its own mechanical boring. The following is a comparative study on the ciliary mechanisms of feeding, digestion, and sediment removal in Adula falcata. Sediment removal could hardly be considered separately from feeding and digestion, as it is during these latter two processes that sediment is resolved from potential food material and extruded from the burrow.

Aside from publications of a purely taxonomic nature, the sole direct references to Adula falcata have been in Lloyd’s (1897) observations on lamellibranch rock boring and Yonge’s (1955) comprehensive work on the adaptation and evolution of the boring habit in the Family Mytilidae. It was, in fact, Yonge’s observations on the role of Figure 1. A lateral view of the burrow of Adula falcata. The mudstone burrow has been cracked open to expose the left side of the enclosed bivalve. This byssally attached mussel had withdrawn from the head of the excavation and had extended its siphonal process for feeding. Other noteworthy features include the furry incrustation on the posterodorsal triangle of the valve and a partially eroded umbone.



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