达氏鲟仔鱼消化系统的发育及摄食初期食性的初步观察

OBSERVATIONS ON THE DEVELOPMENT OF THE DIGESTIVE SYSTEM AND THE FEEDING HABIT OF THE FRY OF ACIPENSER DABRY ANUS DUMERIL

本文描述了达氏鲟仔鱼消化系统的发育过程及仔鱼的食性。 将仔鱼消化系统的发育过程归纳为三个阶段,即初期发育阶段、消化道分化完成阶段、发育完善阶段。这三个阶段与仔鱼的垂直游泳、水平游泳和进入底层生活三个生态阶段相对应。 观察了仔鱼在池塘培育和室内饲养条件下摄食的种类、开始摄食时的长度及消化道内卵黄物质吸收的情况。 根据仔鱼具有口腔齿及消化道结构的特点,认为仔鱼属底层肉食性鱼类的食性类型。其摄食对象主要是水蚯蚓和摇蚊幼虫等底栖无脊椎动物,其次是在池壁和水底活动的枝角类和桡足类。 仔鱼的混合营养阶段不是发生在水平游泳阶段而是发生在进入底层生活之后,与其他的鲟科鱼类仔鱼不同。

The development of the digestive system of the Acipenser fry can be divided general-ly into three stages: 1. The early development stage. When the length of the fry is 12--21.5mm, theyolk sac is large, and the alimentary tract remains primitive. Then the mouth openingand four buds of barbels appear.The fry swims vertically. 2. The completion of the alimentary tract. At this stage the fry attains a length of 21.5--26mm. The mouth is active, provided with toothed jaws. The intestine, rectumand anus are finally differentiated. The fry swims in level. 3. At the completion of the digestive system. The body length of the fry attains to26. 5--30 mm. The oral cavity bears teeth, and the liver, pancreas and pyloric caeca, etc.differentiate to completion. The fry becomes bottom dwelling. The fish is typically carnivorous and bottom dwelling. The fish prefers to eat inver-tebrates, such as freshwater Oligochaetes, Chironomids, Oladocerans, Copepods, etc. Roti-fers and algae are seldom consumed. As the body length reaches 30--31. 5mm. the yolk is nearly absorbed, and the frybegins to take food.