クロサンショウウオの繁殖行動,特に雄の助産行動について

抄録

The reproductive behavior of Hynobius nigrescens, especially its spawning behavior, was observed at Shimoshozenji in the city of Joetsu, Niigata Prefecture in 1992. Twenty-six spawnings were observed. In 17 of these cases, male behavior was observed when the female produced her egg sacs. The male of H. nigrescens has a remarkable reproductive behavior that I call “male midwife behavior”. The typical sequence of the reproductive behavior was: 1) a female perched on the twig which a male had grasped; 2) the female opened her vent and pressed it against the twig; 3) the female swung her tail slowly; 4) the male grasped the female's waist with his forelimbs; 5) the male bent backward lifting her body and pulling the egg sacs from the female's vent; 6) the male put the egg sacs between his hindlimbs and bent backward again; 7) the male released the female's waist and grasped the egg sacs; 8) other males began to scramble for the egg sacs; 9) the egg sacs were pulled out completely by the scrambling males; 10) the males ceased holding the egg sacs. The male that pulled out the egg sacs held them first, except in one case. The male that held the egg sacs occasionally grasped them tightly with his forelimbs and rubbed his vent over them while sliding his hindlimbs. The average number of males that held a pair of egg sacs was 5.6. On the average, the time for the behavior from 5) to 9) required 43 sec, and the time for the behavior from 5) to 10) required 642 sec.