背角无齿蚌稚蚌形态发育与生长特性

Morphological development and growth characteristics of the juvenile of Anodonta woodiana

对背角无齿蚌稚蚌阶段的形态变化过程进行了连续观察，并详细描述了各发育时期的形态特征。结果表明背角无齿蚌稚蚌发育过程可分为贝壳增厚期、壳顶突出期、两翼形成期和背角生长期4个阶段。刚脱落的稚蚌平均壳长242．57μm，在水温为29．0—33．0℃的条件下，经过40d的生长和发育，进入幼蚌阶段，此时平均全长达12．07mm，其形态特征与成体相似。背角无齿蚌稚蚌发育过程中最明显的变化是壳顶位置的变化。在稚蚌发育过程中，壳长生长速度、贝壳性状间的比例关系并不相同。贝壳增厚期的壳长日增长率最高；壳高／壳长比例从稚蚌刚脱落时逐渐减小，到晚期又逐步增加；壳顶前端壳长／壳长的比值在贝壳增厚期逐渐增加，随后又减小，并逐渐与成体的比例接近。对背角无齿蚌稚蚌生长特性的研究表明：壳长与日龄的关系式为L=370．11—32．66t＋14．27t^2-0．15t^3（r=0．976）。

The morphological development of the juvenile of Anodonta woodiana was observed and described. According to the morphological characteristecs, the juvenile development of Anodonta woodiana could be divided into four stages： width expanding stage, umbo extruding stage, wing forming stage and horn growth stage. The average shell length of newly fallen juvenile was 242.57 μm. After developing and growing for 40 days, it came into the juvenile period at the water temperature of 29.0 -33.0 ℃. The juvenile was 12.07 mm in total length, with similar morphological characters to those of adult. The position of the umbo represented the most apparent changes during the juvenile development of Anodonta woodiana. Growth in shell length and body morphometrics varied during different developmental stages. The maximal growth rate appeared expanding stage, and it seemed slower incoordinately in later stages. The proportion of shell height to shell length decreased gradually from 1. 154 to 0.491 at the beginning, and then increased. However, the ratio of anterior length to length increased at first, and then increased to the scale of adult. The relationship between total length and day age could be expressed as L = 370. 11 -32.66t ＋ 14.27t^2 -0. 15t^3（r =0. 976）.