Alternate Title

Age Determination in the Sand Dollar Mellita tenuis


Mellita tenuis were collected from six locations along the Florida gulf coast from March 1997 through Sep. 1998. The anterior-posterior length of the test was measured, and growth lines in the interambulacral plates near the ambitus on the aboral surface (which are oldest) were counted. The number of growth lines is size independent as would be expected if seasonality of growth and growth rate were uncoupled. However, a collection of small individuals had many more growth lines and one of the large individuals had many less than would be anticipated. Lines near the ambitus are difficult to count because they are compressed. In addition, gray growth lines occur between the light and dark ones. The number of plates in the petal increases with body size to an asymptote and cannot be used to age M. tenuis.