水螅异常极性体轴的形成及矫正进程的观察

The Formation and Self-correction of Ectopic Polar Body Axis in Hydra Magnipapillata

目的:如何建立和维持体轴是一个基本的发育生物学问题,而淡水水螅是适合进行形态发生和个体发育调控机制研究的重要模式生物。本文观察了大乳头水螅异常极性体轴的形成及矫正进程,初步探讨水螅极性体轴的维持和调控机制。方法:先切取水螅的整个头部,再获得带二根触手的口区组织。通过ABTS细胞化学染色法检测水螅基盘分子标志物过氧化物酶的表达,判别水螅基盘组织(水螅足区的末端)是否形成。结果:从40块口区组织再生得到的水螅个体中有1例极性体轴发育异常的个体,其身体两端均发育成头区,且两端的头区均具有捕食能力。随后水螅其中一端头区的触手逐渐萎缩、退化,最终该端头区转化成具有吸附能力的基盘组织。结论:水螅组织的再生涉及极性体轴的重建,而一些特殊因素可能造成临时性的水螅极性体轴调控紊乱。本研究表明水螅具备自我矫正异常极性体轴的能力。另外,本研究结果显示水螅触手可以萎缩直至退化,该现象涉及的细胞学过程可能是非常复杂的,有可能涉及到触手细胞的凋亡转化过程,也可能是触手的高度分化细胞仍然具备去分化能力、去分化后再转移到身体其他地方,其具体机制值得进一步探究。

Objective： Understanding how one animal establishes and maintains its body axis is a fundamental question in developmental biology, and freshwater hydra is a suitable model organism for the research about morphogenesis and ontogeny. In the study, the formation and self-correction of ectopic polar body axis in Hydra magnipapillata were observed, and the mechanisms by which the polar axis of hydra is maintained and controlled were discussed. Methods： The whole head tissue was prepared by amputation at the position just below the tentacle ring, and then mouth region tissue with two tentacles was separated from the whole head tissue.Moreover, in order to observe whether new basal disc has regenerated or not, the cytochemical staining method based on substrate ABTS was used to reveal the expression of the peroxidase of basal disc. Results： One hydra body with ectopic polar body axis was found among40 new hydra bodies, and both ends of the hydra body all developed into the head regions, in addition, both head regions were able to prey Artemia larvae. Soon afterwards, the tentacles at one body end gradually atrophied, degenerated, and ultimately the body end losing tentacles turned into basal disc. Conclusion： The tissue regeneration of hydra usually involves the reconstruction of the polar body axis,and some special factors may cause temporary ectopic polar body axis. The results of this study show that the hydra has the ability of self-correcting ectopic polar body axis. In addition, the degradation of hydra tentacles may be involved in some very complex cellular processes such as the apoptosis of tentacle cells, the dedifferentiation of highly differentiated tentacle cells and then transferring to other parts of the hydra body. In a word, the exact mechanism of hydra tentacle degradation is worth further exploration.