B14-O-05Correlative imaging analysis of Tardigrada (water bears) under the active and dehydrated states by X-ray micro-computed tomography, electron microscopy and confocal microscopy

Abstract

Some Tardigrades can survive in the dehydrated state called ‘tun’. However how they can achieve such a remarkable ability of anhydrobiosis has not been well understood. We studied the internal structure of the tuns of three Tardigrade species by mCT at SPring-8 (BL20XU and BL47XU) at the resolution of 83〜500nm: Milnesium tardigradum, Ramazzottius varieornatus, as well as Macrobiotus sp. collected on the Harima Science campus of the Univ. of Hyogo. Previously we identified stylets, buccal tubes, pharynx, and eggs (2010A1350, 2013A1319). Here we succeeded in visualizing organelles with less X-ray absorption (2014B1568). By comparing the mCT images with the ones by confocal microscopy, we identified them as droplets in the coelomic cells in the tun. This allowed us to map the 3D distribution of droplets in a coelomic cell as well as coelomic cells in a tun (Fig). We also visualized the structure of organs in the active state, including the brain, eyes, ganglia, muscles, and digestive organs by mCT and TEM. We are now analyzing the structural change during the recovery (rehydration) by cryo-mCT, and the nano-structure of the tun by electron microscopy.