腐肉食性小型巻貝2種に対するフグ毒給餌実験

摘要

A feeding experiment of TTX-containing diet was conducted using the small scavenging marine snails Pliarcularia globosa and Reticunassa festiva. Seventy-five specimens of each species were divided into 15 groups of 5 individuals, of which 3 groups were directly submitted, without feeding, to toxin quantification as described below. TTX was not detected. Each of the remaining 12 groups was accommodated in a plastic case (80×70×40 mm) filled with seawater, and fed for 24 hours with ovary tissue (0.1g) of the pufferfish Takifugu vermicularis, whose TTX content had previously been determined. Then the seawater was exchanged for fresh seawater, the snails were reared for 4 days without feeding, and then the seawater was changed again. This feeding/rearing cycle (5 days) was repeated 8 times, and 3 groups were sampled every 2 cycles. The combined viscera and combined muscle of each group were each extracted with 0.1% aqueous acetic acid, and then TTX was quantified by liquid chromatography-mass spectrometry. The estimated amount of ingested TTX was calculated by multiplying the difference between the amounts of ovary tissue supplied and remaining by the toxin content (122-126 MU/g). Similar mean values of 5.1MU/group/cycle in P. globosa and 5.3 MU/group/cycle in R. festiva were obtained. Toxin content (TTX amount per gram of tissue) and toxin amount (TTX amount per group) during the experimental period were 0.23-2.85 MU/g and 0.05-0.96 MU/group, respectively, in P. globosa viscera. Both values increased markedly from the 2nd cycle to the 6th cycle. In contrast, no such increase in toxin content/amount was observed throughout the experimental period in P. globosa muscle (＜0.05-0.86 MU/g, ＜0.02-0.27 MU/group), R. festiva viscera (＜0.05-0.8 MU/g, ＜0.02-0.33 MU/group), and R. festiva muscle (＜0.05-0.81 MU/g, ＜0.02-0.23 MU/group). The remaining ratio of TTX (percentage of total toxin amount [sum of the toxin amount of viscera and muscle] to estimated TTX ingestion amount) was less than 4% in P. globosa, and less than 2% in R. festiva after the 4th cycle, suggesting that the possibility that these two species would accumulate TTX at levels hign enough to raise food hygiene issues is low.%腐肉食性小型巻貝のテトロドトキシン(TTX)蓄積能•蓄積機構解明に資するため，ムシロガイ科のコブムシロとアラムシロを用いて毒化モデル実験を行った.両種にTTX含有餌料を投与すると，ともに内臓と筋肉が僅かに毒化した.組織中のTTX量の最高値は，コブムシロ内臓で2.85MU/g,筋肉0.86MU/g，アラムシロ内臓0.80MU/g,筋肉0.81MU/gで，コブムシロ内臓で毒が最も多く残存する傾向が見られた.TTX残存率(推定TTX摂取量に対する総残存TTX量の割合)は，おおむねコブムシロで4％未満，アラムシロで2％未満と非常に低く，これら2種が食品衛生上問題となるほど高毒化する可能性は低いものと推察された.