加拉帕戈斯似殖口虫的形态学、细胞发生学与分子系统学

Morphology,morphogenesis and molecular phylogeny of a soil hypotrichous ciliate Gonostomoides galapagensis(Ciliophora,Hypotrichia,Gonostomatidae)

利用活体观察和蛋白银染色技术对采自甘肃省永昌县马铃薯农田的加拉帕戈斯似殖口虫形态学和细胞发生学特征进行研究,通过提取物种的DNA信息,获得该种的核糖体小亚基基因(SSUrDNA)序列,通过序列比对和构建系统发育树对殖口虫科属间的系统发育关系进行探讨.结果表明,该种形态学特征为:活体大小约为(60~85μm)×(20~25μm),虫体呈长椭圆形,两端收缩钝圆,3列额腹棘毛列,1根口棘毛,横前棘毛、横棘毛和尾棘毛均缺失,大核6~8枚,小核1~4枚附着于大核附近.细胞发生学特征为:老口围带被前仔虫完整保留;第ⅡI~V列棘毛原基以初级发生式发生,第I列棘毛原基单独发生;无横棘毛、横前棘毛和尾棘毛的形成;左右缘棘毛原基产生于老结构;3列背触毛原基产生于老结构.分子系统学分析表明加拉帕戈斯似殖口虫与中华殖口虫和殖口虫属未定种以较高的置信值聚为一支,与殖口虫科其他属形成姐妹支,分子信息再次印证殖口虫科为非单元发生。

The morphology and morphogenesis of Gonostomoides galapagensis,collected from a Solanum tuberosum field in Yongchang County,Gansu Province,China,were investigated using live observations and protargol staining;the small subunit ribosomal gene(SSU rDNA)sequences were obtained,and through sequence alignment and phylogenetic tree construction,their phylogenetic position in the family discussed.The results showed that the morphology of G.galapagensis was characterized by three frontoventral rows,one buccal cirri,pretransverse cirrus,transverse cirrus and caudal cirrus absent;six to eight macronuclear nodules and one to four micronuclei attached to the macronuclear nodules.The morphogenesis was characterized by the parental adoral zone of membranelles retained completely by the proter and the cirral primordia II-VI being of primary primordia,except for anlage I which develops independently;no pretransverse,transverse cirri and caudal cirri are formed;the left and right marginal rows develop intrakinetally and 3 dorsal kineties develop intrakinetally.Phylogenetic analyses based on SSU rDNA sequences showed that G.galapagensis is clusted with Gonostomum sinicum and Gonostomum sp.with a high support,which forms sister clades with other genera of the family,and the molecular information again confirmed that the family Gonostomatidae as a non-monophyletic group.