摘要:
胡子鲶(Clarias fuscus)的胚胎和幼鱼的发育过程与蟾胡子鲶(C.batrachus)类似,器官分化时间和大小比例则有一定的差异。胡子鲶卵呈球形,富含卵黄,卵径1.7—1.9毫米;出膜仔鱼全长4.8—5.1毫米,比蟾胡子鲶约大1/3;幼鱼卵黄囊被吸收消失的时间比蟾胡子鲶迟1—2天。心脏的出现和搏动与开始出现血液循环的间隔时间只有3—5小时;耳石的出现几乎和心脏的出现处在同一时间内,与白鲢有较大的差异。在仔鱼前期居维氏管明显,但出现的时间比蟾胡子鲶稍迟些。仔鱼出膜形式与蟾胡子鲶不同,也与一般鱼类出膜形式不同。仔鱼是以腹部卵黄囊顶破卵膜,以卵黄囊先出膜,一般鱼类多数是以头部或尾部先出膜的。在水温28.5—31℃的条件下,从受精到孵化出膜的时间为28小时25分;幼鱼期共历时12—15天。
Abstract:
The present paper deals with the embryonic and larval development of Clarias fuscus (Lacépède).The fertilized eggs of Clarias fuscus are sticky and spheroid in shape. They are 1.7—1.9 mm in diameter, containing a large quantity of yolk.At the water temperature of 28.5—31.0℃, 38 minutes after fertilization egg plasm begins to concentrate towards the animal pole of the egg and forms a reddish blastoderm. 55 minutes after fertilization, it undergoes the first cleavage. 3 hours and 30 minutes after fertilization, the size of blastomeres becomes smaller and smaller and it is hard to distinguish clearly the cells; this is the morula stage.4 hours and 20 minutes after fertilization, blastodermal cells can still be seen, though indistinctly, and form high blastula. After that, the blastoderm becomes flat and reaches the flat blastula stage.7 hours and 50 minutes after fertilization, the blastomers wrap downwards, this is the beginning of the gastrula stage. 50 minuteslater, the embryonic shield is formed, this is the midgastrula stage. 10 hours and 25 minutes after fertilization, the blastoderm wrap downwards over 4/5 of yolk sac, with neural groove forming on the dorsal part of embryo. 1 hour and 15 minutes later, body segments occur in the mid-part of the embryo.14 hours and 40 minutes after fertilization, optic vesicles appear on both sides of the fore-brain. 17 hours after fertilization, the tail becomes movable. 21 hours and 50 miuntes after fertilization, embryonic body begins to wriggle. 26 hours and 10 minutes after fertilization, heart is to pulsate. 2 hours and 15 minutes later, embryoes begin to break the membrane and hatch out.Newly hatched larvae have a body length of 4.8—5.1 mm. About 72 hours after hatching, the fry will be able to swim, and their yolk sacs are almost absorbed. The now start feeding. Two weeks after hatching, the fry are fully developed in external morphology and may be reared in ponds.The favourable water temperature for embryonic development of Clarias fuscus is 20—33℃, of which 25—30℃ is the optimum. Embryonic development will come to a standstill or will be abnormal when the temperature is below 18℃.
本站查看
下载: