Population Age Structure and Growth of the Trochid Monodonta Lineata Determined From Shell Ring

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Abstract
Seasonal changes in the rate of shell formation frequently affect the surface morphology of molluscan shells, with reductions in feeding activity and calcification rates at low temperatures producing winter rings that can be used for age determination. Such annuli are well-known in lamellibranchs and have greatly facilitated studies on their growth, longevity and other age-related processes (as reviewed by Wibur & Owen, 1964; Rhoads & Panella, 1970; Comfort, 1957, 1979). However, they occur less frequently in gastropods and many species that do show such checks are relatively short-lived, or else their growth ceases or becomes erratic on sexual maturity.