中文摘要：

小头虫复合种在形态特征上非常相似．对渤、黄、东海潮间带11个小头虫种群的形态学研究显示，渤海和黄海种群的形态特征基本一致，而东海种群形态则呈较高的多样性，具有一些文献中未曾记录的胸部刚毛式．实验室种群生活史观察表明，青岛湾和铜陵镇种群幼虫具有卵黄营养发育模式，新孵化的幼虫直接定着在基质上或经历很短的一段浮游期．但这2个种群之间的成虫体节数（P〈0．01）及卵的大小（P〈0．01）具极显著的差异．峰尾镇和鼓浪屿的实验室种群都观察到2类幼虫：无体节分化的担轮幼虫和具10多个体节的后担轮幼虫．2个种群之间在成虫体节数（P〈0．05）、卵大小（P〈0．01）及浮游幼虫大小（P〈0．01）上的差异显著．野外调查中未发现雌雄同体现象存在，但在实验室培养的青岛湾和鼓浪屿种群中，均发现有雄性先熟和雌性先熟的雌雄同体．为了更准确地解释小头虫复合种的分化及系统进化关系，尚需在生活史、形态学和亲缘地理学方面作进一步的综合研究．

英文摘要：

Capitella capitata is a complex of morphologically similar but genetically distinct sibling species. Examination of C. capitata complex from intertidal zones of Bohai Sea, the Yellow Sea and the Eastern China Sea revealed that individuals from Bohai Sea and Yellow Sea were almost identical in morphology. Those from East China Sea showed diversified morphology with some thoracic setal formulas not recorded previously. Examination of four laboratory populations found that Qingdao Bay and Tonglingzhen populations had a lecithotrophic larva mode with newly hatched metatrochophore larvae settleing in strata directly or had a brief planktonic life stage. Adult worm average setiger numbers （P〈0.01） and egg sizes （P〈0.01） were significantly different in these two populations. Fengweizhen and Gulangyu Island populations exhibited polymorphism in larva development. Both trochophore with no setiger differentiation and metatrochophore with over 10 setigers were found in laboratory culture. Average adult setiger numbers （P〈0.05）, and egg sizes （P〈0. 01） vary widely in these two populations. Planktonic larvae from Fengweizhen population were remarkably smaller than Gulangyu Island population （P〈0.01）. Although no hermaphrodite individuals were found in field sample, both protandrous and protogynous hermaphrodite individuals were observed in laboratory populations from Qingdao Bay and Gulangyu Island. To understand more fully differentiation and evolution in C. capitata complex, further studies need to be done.