SELECTIVE SURVIVAL OF A THERMOSTABLE DIRECT HEMOLYSIN-PRODUCING VIBRIO-PARAHAEMOLYTICUS IN THE ALIMENTARY-TRACT OF A JUVENILE ESTUARINE GASTROPOD (CLITHON RETROPICTUS)

Juvenile estuarine gastropods (Clithon retropictus), maintained in ult raviolet ray-irradiated recirculating artificial seawater with a salin ity of 20 parts per thousand at 28 degrees C, preserved thermostable d irect hemolysin (TDH)-producing strain D-3 of Vibrio parahaemolyticus at a level of 10(4)-10(5) colony forming units per gram (cfu/g) and TD H-non-producing strains N-18 and R-13 at a level of 10(1)-10(2) cfu/g in the alimentary tract for at least 21 days after ingestion. In adult s, the numbers of the three strains decreased to a level of 100 cfu/g within 21 days under the same conditions. This evidence supports our r ecent observations that TDH-producing strains increased to a high leve l in the summer months in the presence of high levels of TDH-non-produ cing strains in the alimentary tract of juvenile C. retropictus at est uaries in Japan.