匙吻鲟早期形态发育与生长阶段划分

STUDY ON EARLY MORPHOLOGICAL DEVELOPMENT AND DIVISION OF GROWTH STAGES OF ANNUAL AMERICAN PADDLEFISH

匙吻鲟早期生活史可分为仔、稚、幼鱼３期。出膜至２３～２５日龄，全长约５７ｍｍ时为仔鱼期。此期形态变化以吻部最为显著，由钝状占全长的１５％，发育至扁平桨状，接近全长的３０％。稚鱼期结束时（６７～７３日龄），鳍条发育完成，鳍式为背鳍（Ｄ）３７～４４，臀鳍（Ａ）３３～４５，胸鳍（Ｐ）２１～２６，腹鳍（Ｖ）２３～３０，尾鳍（Ｃ）７９～９１，全长约１６４ｍｍ。生长７３日后为幼鱼期，全长＞１６４．０ｍｍ，吻长大于全长的３０％，身体各部分比例与成体相似。在匙吻鲟早期发育中，其吻长、头长增长较迅速，而体高、眼径、尾柄高增长较为缓慢。

The early life history of American paddlefish is divided into three stages: larva, juvenile and young. The larva stage lasts for 23～25 days from hatchery, during which time its body grows to about 57 mm and the kiss length accounts for approximately 30% of the total length. In the juvenile stage (67～73 days after hatchery) all the fins complete their development (D.37～44, A. 33～45, P. 21～26, V. 23～30 and C. 79～91) with a total length of 164 mm. It enters into the young stage 73 days after hatchery, during which time its body grows to >164.0 mm, the length of its kiss accounts for >30% of the total and the proportion of various parts of the body is simmilar to that of the adult paddlefish. In its early development the length of its kiss and head increases quite rapidly while its body height, eye diameter and tail height grow comparatively slowly.