AN INDEX OF AGE WHEN BIRTHDATE IS UNKNOWN INAPLYSIA CALIFORNICA: SHELL SIZE AND GROWTH IN LONG-TERM MARICULTURED ANIMALS

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Abstract
The purpose of this study was to determine the age of postmetamorphic Aplysia when the birthdate was not known. The study is based upon the long-term growth and maintenance of Aplysia californica kept in artificial sea water up to 235 days. Body and organ weights and organ size were measured. The most reliable measure of growth and age was the size of the internalized shell. The rate of shell growth was determined, and on the average it was 0.23 mm/ day throughout post-metamorphic life. A means of determining age using shell size is given. The results reported here are used to determine the age of Aplysia in which age-dependent changes in behavior and in anatomical and physiological properties of single nerve cells have been found.