其腹面口区具二环围口纤毛列；背面具一列背刚毛。
There are two circumoral ciliary rows on the buccal region and a dorsal row of bristles.
为了减少磨损，提高活塞环的使用寿命，对整体无背压活塞环的设计进行了研究。
The design of integral non-backpressure piston rings was studied in order to reduce wear and to raise the piston ring life.
其腹面口区具二环围口纤毛列及一口前纤毛列；背面具一列背刚毛；腹面纤毛列的数目可发生较大变动。
There are two circumoral ciliarvrows and a preoral ciliary row on the buccal region and a dorsal row of bristles.
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