In the p5 to p7 phases , most shrimp settle into life on the bottom or sides of the pond , they need only annelida and nematoda . at this time , 一般稚虾在p5 p7就开始进入底栖生活或倚壁生活，而嗜食环节动物annelida及圆形动物nematoda等小型底栖动物。
2.
As we all know , bilateral symmetry , three - layer embryo , metamerism and having a relatively developed head are the common characteristics of the arthropoda and annelida , so it is believed that arthropod originated from annelid 由于节肢动物具备环节动物两侧对称、三胚层、身体分节、头部较发达等特征，所以一般认为节肢动物起源于环节动物或类似环节动物的祖先。
3.
But as a matter of fact , athropoda has some more complex characteristics than annelida , such as the exoskeleton , departmental body - plan and segmented appendages , which , as one parameter , results in the abundance of arthropod fossils in the chengjiang fossil lagerstatte 但节肢动物还具有比环节动物更高级的特征，如：身体分部、附肢分节；循环、生殖、排泄等系统均较环节动物复杂高级，这可能是澄江化石库中节肢动物种数丰富的一个很重要的原因。
4.
The amounts of limnodrilus hoffmeisteri increased gradually from baihe to huacao section , and reached a peak in huacao section ; species from annelida , mollusca were not found in beixinjing and wuninglu sections ; species from oligochaeta were found and had certain numbers in zhejiang road section as the result of the effect of counterflow of the huangpu river 1材料与方法1 1采样断面及采样点在苏州河上海市区段的上游至下游共设6个采样断面，分别是白鹤、黄渡、华槽、北新泾、武宁路和浙江路断面。每个采样断面又分别设3 - 6个采样点。
