蛇鮈的产卵习性及胚胎发育

The breeding habits and embryonic development of longnose gudgeon (Saurogobio dabryi Bleeker)

蛇 每年３～４月产卵，产卵下限温度１２℃．产卵环境特点：微流水，底质为卵石和沙质的浅水河滩．集群产卵，繁殖群体的性比为♀：♂＝８：１．卵微粘性，卵径１．０～１．１ｍｍ，比重略大于水．在水温１５．０～１８．３℃条件下，观察了胚胎及胚后发育过程：受精后１ｈ６ｍｉｎ，胚盘形成；再过２５ｈ４ｍｉｎ后，胚孔封闭．从受精到孵化历时８１～８２ｈ，初孵仔鱼全长４．５ｍｍ．孵出后第１０ｄ，卵黄囊消失，全长６．４ｍｍ．

Longnose gudgeon (Saurogobio dabryi Bleeker) spawns from March to April every year when the water temperature rises above 12℃. The spawning grounds locate at pebbly and sandy shoals with the water flowing slowly. When spawning parental fishes gather at the grounds and the ratio of the female and male is 8: 1. The ripe egg of this:fish is slightly sticky and demersal, and its diameter is 1. 0 1. 1mm. The embryonic developthent was observed at 15. 0-18. 3℃ in laboratory: Embryonic disc formed 1 hour 6 minutes after ferhlization ; 25 hours 4 minutes later, blastopore closed. The whole pro cess of embryonic development lasted for about 81-82 hours, from ferhlied eggs to the larvae just hatched out. The total length of newly-hatched larvae is 4. 5 mm. The yolk was aborbed completely 10 days after hatching, when the total length is 6. 4 mm. The type of eggs and mating system of the fish are also discussed.