| 摘要: |
| 锥状斯氏藻STDP01克隆品系于1993年1月分离自大鹏湾底泥中的单个锥状斯氏藻孢囊，并经单细胞分离培养成藻株。在电子显微镜下，对该藻的营养细胞和孢囊形态进行了观察，该藻营养细胞与多甲藻目的其它甲藻不同，没有非常明显的甲板；孢囊球形或卵形，直径15—30μm，突起钙化长短大小不一，从钝到尖。萌发孔为中间（theropylic）型。在实验室光、温及营养盐的人工调控下，运用倒置显微镜，对锥状斯氏藻生活史进行了追踪，发现该藻属典型的甲藻生活史，由营养生长、暂时性休眠和休眠孢囊三个阶段组成。孢囊形成通过有性生殖，经两配于结合形成浮游合于并进一步形成泡囊。对孢囊形成和萌发的条件进行探讨的结果表明，在营养盐充足的条件下锥状斯氏藻生长良好，最大比生长率可达0.42d-1；氮盐缺乏是诱寻其孢囊形成的关键因子，当锥状斯氏藻生长在f/2缺氮（以25 μmol/L NH4+代替NO3-）条件下孢囊形成率可达87％；磷酸盐缺乏虽然使营养生长减缓，但并不能诱导孢囊形成；对孢囊形成率也无显著影响。新形成的孢囊必须在经过一段时间休眠后，在氮源充足，光照、温度合适时方可萌发。孢囊在冰箱中经三个月储存后，在不同的温度（8，15，20和25°C）和光照（200,600,1600,2800,4500,6000和7500lx）下测试其萌发情况。萌发率与温度在8-20°C范围内呈正相关。在20°C时达到最大，为90%；15°C时为30%，8°C时仅为10%。而25°C时较20°C有所下降，为80%。光照实验15d后不同光照组（200lx组除外）萌发率都在80%-90%之间，200lx组为50%。表明微弱短暂的光照（200lx）即可启动萌发，高光强（7500lx）虽然可以虽短萌芽时间，对孢囊萌发率并无明显影响。结果表明，锥状斯氏藻孢囊萌发和大量繁殖都和氮营养紧密相关，富营养化特别是氮营养的富积是引发该藻赤潮发生的关键。 |
| 关键词: 锥状斯氏藻 生活史 孢囊 环境调控 |
| DOI： |
| 分类号: |
| 基金项目:国家自然科学基金!9389008 |
附件 |
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| THE LIFE CYCLE OF SCRIPPSIELLA TROCHOIDEA AND ITS PHYSIOL-ECOLOGICAL CONTROL |
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Qi Yuzao, Zheng Lei, Wang Rong
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Institute of Hydrobiology, Jinan University, Guangzhou 510632
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| Abstract: |
| The culture of Scrippsiella trochoidea was established from germinated cyst isolated from Dapeng Bay (southern China) sediment samples in January 1993. The clonal strain STDP 01 was re-isolated from a single cell of this culture. The morphology of vegetative cells and cysts of Scrippsiella trochoidea were observed using a scanning electronic microscope. The vegetative cell shows no obvious plates, which is different from other Peridnales species. The cyst, spherical to ovoid, has a diameter from l5 to 30 μm. The processes are calcareous and vary in length and in shape (from blunt to pointed). A theropylic archeropyle was observed. The different stages of life cycle were observed under the control of light, temperature and nutrient under lab conditions. The life cycle belongs to a typical dinoflagellate cycle which include a vegetative cycle (cell division), a temporary cyst cycle and a resting cyst cycle. Resting cyst cycle formation could be fulfilled by sexual reproduction and was formed from planozygote by fusion of two isogametes. In terms of the conditions for cyst formation and germination, when the nutrients were plenty, the vegetative cells of Scrippsiella trochoidea grew well and could reach a maximum growth ratio of 0.42d-1. Nitrate depletion was a key factor to induce cyst formation. When the vegetative cells were grown in the f/40 (25 μmol/L NH4+, no added NO3-) medium, the first cyst appeared at the stationery stage or the end of log phase (8th days) and cyst formation ratio reached 8.7%. Phosphate depletion can reduce the growth rate of vegetative cells but cannot induce cyst formation or affect the cyst formation ratio. Newly formed cysts can germinate only after a period of dormancy (3 months) when nitrogen is replete and light and temperature are suitable. Different temperatures (8, 15, 20, 25°C) and light intensities (200, 600, 1600, 2800, 4500, 6000 and 7500lx) were adopted to test the germination ratio of cysts after being stored in dark refrigerator in 4 - 5°C for three months. The results reveal that temperature has a positive relation with germination among 8, 15 and 20°C. The germination ratio can reach a maximum of 90% at 20°C, 30% at 15C and 10% at 8°C. The germination ratio was 80% at 25°C, which was less than 20°C. Even weak light intensity (200lx) can initiate cyst germination. After repletion with a fresh f/2 medium for two weeks, cyst germination ratio in different light intensities (600 - 7500lx) could reach the same (80% - 90%). High light intensity (7500lx) causes a decrease in the germination time, but has little effect on the germination ratio. The results also show that cyst formation and rapid vegetative reproduction have a close relationship with nitrate nutrient. Eutrophication is a key factor for bloom outbreak. |
| Key words: Scrippsiella trochoidea, Life cycle, Cyst, Environmental control |
