On the Metamorphosis and Burrowing Habits of the Snake Eel, Muraenichthys gymnotus
On the Metamorphosis and Burrowing Habits of the Snake Eel, Muraenichthys gymnotus
复制标题
蛇鳗的变态与穴居习性
DOI：
10.11369/jji1950.27.237
复制
发表时间：
1980
期刊：
影响因子：
--
通讯作者：
Yasushi Nozawa
中科院分区：
文献类型：
--
作者：
A. Ochiai;Yasushi Nozawa
下颌为0·`1+I·`VI+0-4。胸鳍短小，约为头长的5倍，背鳍起点位于肛门稍前方，肌节总数131 ~ 140个，肛前肌节66 ~ 70个，肛后肌节64 ~ 71个，胆囊前缘位于肌节18 ~ 23处，第一垂直血管位于肌节16 ~ 20处，最后一条垂直血管位于肌节58 ~ 65处。消化道狭长，有6 ~ 9处微环。从我们的饲养实验结果可以看出，幼虫的变态在一周左右的时间内迅速完成，变态开始后第2天，双颚的幼虫牙齿完全消失，第5天，锥形牙齿开始出现。变态阶段，肛门位置缓慢前移，第5天背鳍开始于肛门上方或稍后，第4天在吻部、下唇和背外侧面散布小黑色素细胞，第5天全长最小，平均51.2mm。幼鱼期约20天，体长30倍以下，胸鳍几乎不可见或完全消失，幼鱼末期背鳍起源于肛门后约与吻长相等的位置，体呈浅褐色。变态前的幼虫在变态前停止活动，钻沙底，蛇鳗在变态期和幼鱼期都是典型的头钻者。
jaw,and 0•`1+I•`VI+0-4 in the lower. The pectoral fin is feeble and short,about 5 times in head length.The origin of the dorsal fin is situated slightly in advance of the anus.The total myomeres are 131 to 140, preanal myomeres 66 to 70,and postanal myomeres 64 to 71.The anterior margin of the gall-bladder is at level of myomeres 18 to 23,the 1st vertical blood vessel at myomeres 16 to 20,the last vertical blood vessel at myomeres 58 to 65.The alimentary canal is long and narrow,looped slightly in 6 to 9 places.The pigmentation of the body is conspicuous and characteristic. From the results of our rearing experiment,it can be concluded that the metamorphosis of the larvae is accomplished rapidly in about one week.The larval teeth on both jaws are lost entirely on the 2nd day after the onset of metamorphosis,and the conical teeth begin to appear on the 5th day.During the metamorphosing stage the position of the anus slowly moves forward,then the dorsal fin originates above or slightly behind the anus on the 5th day.Small melanophores are scattered on the snout,lower lip and dorsolateral surface of the body on the 4th day.The total length reaches its minimum size, 51.2 mm in average,on the 5th day. The juvenile stage lasts for about 20 days in the rearing experiment.The body is well elongate,its depth is lower than 30 times in total length.The pectoral fin is scarcely visible or entirely absent.In the last juvenile stage the dorsal fin originates behind the anus at a distance about equal to the length of the snout,and the bodys are colored with light brown. The premetamorphic larvae cease to be planktonic and burrow themselves into the sand bottom just before metamorphosis.The snake eel is a typical head burrower throughout metamorphosing and juvenile stages.