POPULATION AGE STRUCTURE, GROWTH AND LONGEVITY OF THE MARINE GASTROPOD UROSALPINX CINEREA SAY

¹ Biological Sciences Group, University of Connecticut, Storrs, Connecticut 06268

1. A study of growth and age structure in a Connecticut population of Urosalpinx cinerea was carried out using both shell length and weight frequency analysis. A cumulative growth curve is proposed and compared with other published data for the species.

2. Growth interruption marks (annuli) occur in Urosalpinx but are not as useful as in some other mollusks because of difficulty in discriminating annuli from interruptions caused by other factors.

3. Close to seventy percent of maximum shell growth is attained after two growing seasons. No increase in length occurs after four to five years and older snails, if present, constitute a very small proportion of the total population.

4. Growth of oyster drills in their first season is highly variable. Prey quality and availability may be the principal cause of this.

5. At Noank, Balanus balanoides is the major prey species of U. cinerea but newly hatched and very young snails frequently attack encrusting ectoprocta, particularly Cryptosula pallasina. This diversification of prey is an advantage to the predator since it leads to a reduction in competition for food between juveniles and adults.