RADULAR PRODUCTION-RATES IN 2 SPECIES OF LACUNA-TURTON (GASTROPODA, LITTORINIDAE)

The molluscan radula is a dynamic organ, both in terms of its use and production. New rows of teeth are constantly produced at the posterior end of the radula, while older, worn teeth are shed anteriorly, produ cing a dynamic equilibrium. We used a cold-shock to mark the radular r ibbon and measure tooth row production rates in two gastropod species, Lacuna vincta (Montagu) and L. variegata Carpenter. We found that the average tooth row production rate at 10-11 degrees C did not differ b etween these tao species, and was 2.94 (SE = 0.002) rows per day for L acuna vincta and 2.97 (SE = 0.002) for L. variegata. Inter-individual variability in production rate was very low, and was correlated with s hell length; smaller individuals had slightly higher production rates. The total length of the radular ribbon varied greatly among individua ls, ranging from 47 to 94 (2.57 to 5.68 mm) rows in L. vincta and 53 t o 99 rows (2.80 to 7.14 mm) in L. variegata, and was only somewhat cor related with the length of the shell. This great variability will resu lt in large differences among individuals in the time it takes to repl ace the radula totally, from 14.96 to 35.44 days in L. vincta and from 17.43 to 39.69 days in L. variegata.