proctal fin的用法和樣例：
例句
- Old World freshwater catfishes having naked skin and a long anal fin more or less merged with the eellike caudal fin.
東半球的淡水鯰魚，體表無鱗，有類似鰻魚尾鰭的很長的臀鰭。 - The male shows elongated rays in its anal fin and yellow pearl organs on the jaws and opercula during breeding season.
雄魚的臀鰭鰭條特長，交配季節兩頜和鰓蓋會長出黃色的珠星。
