MICROFLORA AND TETRODOTOXIN-PRODUCING BACTERIA IN THE LINED MOON SHELL NATICA-LINEATA

The lined moon shell Natica lineata was seasonally collected from two places in Taiwan, Kaohsiung City, and Pintgung Prefecture, and assayed for anatomical distribution of tetrodotoxin (TTX) and aerobic hetrotrophic bacteria. Kaohsiung specimens showed a higher toxicity than Pingtung ones. At either place, the gastropod exhibited the highest toxicity in February. The aerobic bacteria counts exhibited an outstanding seasonal variation: 10(8) CFU (colony forming unit)/g in August 1990, reducing to 10(5) CFU/g in February 1991, and then increasing to 10(6) CFU/g in May 1991. Predominant genera were Vibrio, Aeromonas, Flavobacterium, and Pseudomonas. Vibrio comprised more than 46% of the genera, with V. alginolyticus as the major one. However, there was no relationship between the total viable counts and the toxicity of the shellfish. HPLC, UV, and GC-MS analyses demonstrated that some bacteria when isolated, such as V. alginolyticus and Aeromonus spp., produced TTX and/or related substances.