sentences:  Amongst their major orders albaillellaria, ectinaria, the spherical spumellaria and the hood-shaped nassellaria can be distinguished.According to Takahashi (1983) radiolarians stay for 2 to 6 weeks in the euphotic zone (productive surface layer to 200 meters water depth) before they start sinking.Their descent through 5000 meters of ocean water can take from two weeks to as long as 14 months.