广西茅尾海的香港巨牡蛎(Crassostrea hongkongensis)在不同养殖区的性腺发育变化

Gonad Development of Oyster (Crassostrea hongkongensis)at Different Cultural Sites in Maowei Bay, Guangxi, China

中文关键词: 香港巨牡蛎  组织切片  性腺发育  盐度  温度

英文关键词: Crassostrea hongkongensis  Histological study  Gonad development  Salinity  Temperature

中文摘要:

      为探究香港巨牡蛎(Crassostrea hongkongensis)的繁殖特性以及春季死亡原因，采用肉眼观察、活体镜检和组织切片方法研究了茅尾海沙井的香港巨牡蛎苗种吊养于大风江黄场的1龄牡蛎的性腺发育周年变化，并建立了快速判断香港巨牡蛎性腺发育程度的方法。对比分析了吊养在茅尾海沙井、大风江入海口内的黄场和入海口外的鑫丰场的2龄牡蛎性腺发育的启动和发展过程。结果显示，广西茅尾海的香港巨牡蛎每年只有1个繁殖周期，性腺发育过程可划分为未分化期(1–3月)、分化期(4月)、成熟排放期(5–10月)及休止期(11–12月) 4个阶段；1龄和2龄牡蛎的性腺发育基本同步；大风江入海口外的牡蛎的性腺发育较入海口内的牡蛎提前约15 d，而比茅尾海内海的牡蛎提前约30 d，入海口外的牡蛎的性腺4月即发育到成熟排放期，冬季饵料的丰富程度和温度、盐度等因素可能是造成这种差异的原因。研究还发现，高温少雨天气下，海水盐度高，抑制了牡蛎性细胞的排放，导致入海口外侧吊养牡蛎的大规模死亡，濒临死亡的牡蛎性腺处于退化和崩解状态。鉴于此，认为4月初即需密切监测吊养于入海口外的牡蛎性腺的发育状况和天气状况，及时收获性腺饱满的牡蛎，或将吊养牡蛎的蚝排放置在河流入海口内区域过冬。

英文摘要:

      The oyster Crassostrea hongkongensis is the main aquaculture species along south China coast and has an important economic value. The Maowei Bay adjacent to Qinzhou of Guangxi Province has been the largest natural oyster seed field, and oysters originating from this area are named after the place (Qinzhou oyster). The estuary of the Dafeng River is a major aquaculture site for Qinzhou oyster in Guangxi Province. Due to the promotion of the deepwater-raft-hanging-culture mode, massive death of oysters has occurred frequently in spring since 2008 and resulted in the rapid drop in the amount of oyster seeds in the Maowei Bay. In this study we explored the reproductive cycle of oyster gonad development and investigated the causes of the massive death, using one-year old oysters from the estuary of Dafeng River (HH, whose larva came from the Maowei Bay). We developed a method for rapid identifying the developmental stage of oyster gonad with the combination of naked-eye observation, biopsy and histological analysis. We also compared the gonad development of two-year old oysters from inside (HH) and outside (XF) of the estuary of the Dafeng River and from the Maowei Bay (MS). We found that Qinzhou oysters had only one breeding cycle each year which can be divided into 4 gonad developmental stages: the undifferentiated stage from January to March, the differentiation stage in April when the gender became distinguishable, the mature and discharging stage from May to October when the oysters spawned repeatedly, and the resting stage from November to December during which the gonads atrophied and disappeared. Gonad development of XF oysters started half a month earlier than HH oysters and one month earlier than MS oysters. In 2014 it was observed that the gonad of XF oysters developed into mature stage in April. The variation might be caused by differences in temperature, salinity and food abundance. Moreover, in overly hot and dry weather the gonad discharge was inhibited probably by high salinity, which may explain the massive death in the high salinity area. Therefore, we recommend close monitoring on the gonad development and seawater salinity in spring. The oysters should be harvested or transported to the inner estuary immediately after they mature, so as to avoid the massive death caused by scarce rainfall