Morphological and molecular discrimination of green macroalgae Chaetomorpha aerea and C. linum
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摘要: 海洋大型绿藻气生硬毛藻(Chaetomorpha aerea)和线形硬毛藻(C. linum)在分类方面易引起混淆。针对这个问题,我们尝试通过形态与分子分析来区分这两个种。气生硬毛藻和线形硬毛藻能通过形态特征区分,如藻体形态、细胞形状与大小、细胞长宽比(LWR)及细胞壁收缢等。气生硬毛藻的藻体一般向基纤细,上部直径270-500μm,中部直径160-360μm,下部直径100-160μm;在上部,细胞的长小于宽;细胞壁常常在横隔处收缢,使得丝体呈珠状。而线形硬毛藻的藻体在相同个体上常常直径为稳定的90-300μm,细胞圆柱状或桶状,细胞壁常不收缢;其LWR比气生硬毛藻的大。分子分析结果表明,这两个种的18S rRNA基因差异为3.6%-3.7%、ITS为53.5%-54.3%。在系统发育上,它们分布在较远的进化支上,证明在分子水平上具有遗传差异。另外,形态学数据表明,线形硬毛藻样品的藻体直径变化大,范围达到90μm-300μm。因此,建议这两个种作为独立种处理。
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关键词:
- 气生硬毛藻Chaetomorphaaerea /
- 线形硬毛藻Chaetomorphalinum /
- 分子鉴定 /
- 形态比较 /
- 18SrRNA /
- ITS
Abstract: Green macroalgae Chaetomorpha aerea and C. linum are taxonomically confused. In this paper, we tried morphological and molecular analyses to separate these two species. C. aerea and C. linum can be distinguished from morphological characteritics, such as frond dimension, cells size and shape, their mean length/width ratios(LWR), and cell walls constriction. Thalli of C. aerea attenuate basipetally, with diameter 270-500μm at upper portion, 160-360μm at middle portion, 100-160μm at basal portion. For the upper part, the length of cells is less than their diameter. Cell walls usually constrict at the dissepiments, which are pellucid or colorless and give the filament beaded appearance. In contrast, thalli of C. linum often have a constant diameter of 90-300μm within the same individual, cell walls usually do not constrict and cells are cylindrical or barrel shaped. The LWR is larger than that of C. aerea. Results show that the pairwise distance between two species is 3.6%-3.7% for 18S rRNA gene and 53.5%-54.3% for ITS region. In phylogeny, they distribute at distant clades, which confirms a genetic divergence at molecular level. In addition, morphological data indicates that filament diameter of C. linum samples is highly variable, ranging from 90μm to 300μm. Then these two species can be considered as separate species.-
Key words:
- Chaetomorpha aerea /
- Chaetomorpha linum /
- molecular identification /
- morphology comparison /
- 18S rRNA /
- ITS
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