Observation on Developmental Changes during the Sexual Reproductive Period of Sargassum thunbergii

Abstract

The growth, development, and sexual reproduction of <em>Sargassum thunbergii</em>, which collected from Dongtou, Zhejiang Province were studied under controlled lab conditions, and its early developmental process were recorded. Results showed that: (1) The first appearance of receptacle on <em>S. thunbergii</em> in the present study was in the mid-May and became matured in about late of June, and the eggs and sperms were realeased from female and male receptacles respectively. The released eggs attached to the surface of female receptacles and were fertilized by sperms to form zygotes. A clearly correlationship between the length of receptacle and its maturing level was observed, which was helpful for the artificial breeding of <em>S. thunbergii</em>. Moreover, temperature and salinity had obviously effect on the growth of receptacles, and temperature seemed more essential as compared to the salinity. The optimal condition combination basing on the orthogonal analysis for the receptacle’s growth was 22 ℃ and salinity 30. (2)The fertilized eggs began its first cell division at 1 hour after fertilization and the continuous 2 times of divisions would result in a four-cell structure. Cellular division occured every 2~3 h thereafter and finally formed the multi-cell germling. The germlings would stick to the substrates for adherence, and their lengths increased steadily with some side heaves observed within 23 days. They grew well with a coarse surface and darkened color. Results in the present study inferred that the combination of germling breeding and sexual reproduction for the artificial cultivation of <em>S. thunbergii</em> was feasible.