我国西沙群岛石花菜属一新纪录变种: 匍匐石花菜扁平变种Gelidium pusillum var. pacificumTaylor

摘要

2014年3—4月间,在西沙群岛鸭公岛海藻资源调查中采集到一种石花菜类海藻,经鉴定为匍匐石花菜扁平变种Gelidium pusillum var.pacificum Taylor.其主要特征为: 1.藻体紫红色,丛生; 2.藻体高约1~2cm,由匍匐茎和直立枝构成, 直立枝基部圆柱形或扁压, 上部扁平, 具有不规则或羽状分枝, 匍匐茎近圆柱形, 其下生有不规则或尖锥状固着器; 3.皮层细胞2~3层,根丝细胞数量较多,集中分布在髓层; 4.四分孢子囊生于小枝顶端,形成囊群,四分孢子囊横切面观长卵圆形,埋于皮层细胞中,十字形分裂; 5.枝顶端轴细胞形态为穹形,突出于皮层外.上述特征1~3可将匍匐石花菜扁平变种区别于我国产的匍匐石花菜其他变种, 特征5可将该变种区别于个体较小的蓝色拟鸡毛菜, 特征4不能有效地区分近缘种.综合如上特征, 利用营养生长特征鉴定我国分布的个体较小的石花菜和拟鸡毛菜类群是一种可行的方法.该变种为我国三沙市西沙群岛首次记录, 丰富了南海诸岛海藻区系的植物地理成分, 也为进一步分析该区系的植物地理全貌提供了技术资料.%A survey of macroalgal resources in the Xisha Islands was carried out from March to April 2014. A species of Gelidium sp. was collected and identified asGelidiumpusillum var.pacificum Taylor. The main characters of this species were as follows: 1. thallus purple-red, caespitose; 2. plants up to 1-2 cm high, composed of creeping and erect axes, creeping axes slender cylindrical, and the upper part of erect axes compressed, with irregular or pinnated branches; 3. in transverse sections, cortices consist of 2-3 layers, and rhizoidal filaments were abundant in medulla; 4. tetrasporangium ovoid in transverse view, embedded in the cortical cells, divided cruciately and developed on the apical part of branchlets, forming sori; and 5. the apical cell of the main axis was globose, dome-shaped, protruding out of cortical cells.Gelidiumpusillum var.pacificum can be segregated from other variants withinGelidiumpusillum by combining characters 1 to 3. Characters 5 can be used to distinguishGelidiumpusillum var.pacificum from small sizedPterocladiella species, such asPterocladiellacaerulescens. Characters 4 cannot be used to discriminate it from its related species, because the size and shape of sori vary similarly. Thus,apical morphology may be a promising vegetative attribute to segregate small sizedGelidium species from some similar Pterocladiella species found in China.Gelidiumpusillum var.pacificum was the first record in Sansha region of the South China Sea, which enriched the species diversity of this marine algal flora and further facilitated the analysis of general aspects of this marine algal flora.