The gastropod statolith:: a tool for determining the age of Nassarius reticulatus

The microstructure, shape and appearance of the growth rings in statoliths of Nassarius reticulatus ( L.) were investigated. This species possesses two statocysts, each containing a single spherical statolith of calcium carbonate of up to 0.22 mm in diameter in the largest animals. The relationship between statolith diameter (SD) and total shell height (TSH) is exponential [ln( TSH)= 26.3SD - 0.842], although the function is site specific. Statoliths of the largest whelks (> 29 mm) contained three or four clearly defined rings, corresponding to TSH values of similar to 1.1, 4.6 - 5.3, 12.0 - 13.5 and 18.5 mm, respectively. The first ring likely represents the "metamorphic'' ring that was deposited at the time of larval metamorphosis when the post-larval whelk adopted a benthic lifestyle. The estimated size of the whelks at formation of the second, third and fourth statolith rings closely matched the TSH inferred from the shell rings. It is concluded that the patterns of growth rings present in statoliths can provide information about the age and growth of N. reticulatus.