Size-correlated polymorphisms in phyllotaxis-like periodic and symmetric tentacle arrangements in hydrozoan Coryne uchidai

Introduction: Periodic organ arrangements occur during growth and development and are widespread in animals and plants. In bilaterian animals, repetitive organs can be interpreted as being periodically arranged along the two-dimensional space and defined by two body axes; on the other hand, in radially symmetrical animals and plants, organs are arranged in the three-dimensional space around the body axis and around plant stems, respectively. The principles of periodic organ arrangement have primarily been investigated in bilaterians; however, studies on this phenomenon in radially symmetrical animals are scarce.Methods: In the present study, we combined live imaging, quantitative analysis, and mathematical modeling to elucidate periodic organ arrangement in a radially symmetrical animal, Coryne uchidai (Cnidaria, Hydrozoa).Results: The polyps of C. uchidai simultaneously formed multiple tentacles to establish a regularly angled, ring-like arrangement with radial symmetry. Multiple rings periodically appeared throughout the body and mostly maintained symmetry. Furthermore, we observed polymorphisms in symmetry type, including tri-, tetra-, and pentaradial symmetries, as individual variations. Notably, the types of radial symmetry were positively correlated with polyp diameter, with a larger diameter in pentaradial polyps than in tetra- and triradial ones. Our mathematical model suggested the selection of size-correlated radial symmetry based on the activation-inhibition and positional information from the mouth of tentacle initiation.Discussion: Our established quantification methods and mathematical model for tentacle arrangements are applicable to other radially symmetrical animals, and will reveal the widespread association between size-correlated symmetry and periodic arrangement principles

授業「キャンプ実習」に関する研究（4） ― 4 ヶ年の基礎研究と総合評価―

This research of the fourth stage executed mainly the comparison of the basic researches into four years. The chief purpose was clarification of a universal part of four years. The results were summarized as follows: 1．The reason for participation was“Cheap expenditure”and“Course credit”．The expected program was“Observation of constellation”and“Outdoors cooking”．The expectation and the acquisition target were“Enjoyment”，“Safety”and“Peace”． 2．This year’s problem was a discovery of the method of thoroughly improving students’knowledge and technologies. 3．Students’leadership was extent to be able to do“Life guidance”and“Standard program”． 4．The factor analysis has extracted the following six factors.“Mutual guidance and Consideration”， “Impartiality and Democratic”，“Inspiration and Commitment”，“Active collaboration and Device”，“ Pleasant sharing”and“Self management and Health condition”． 5．The attitude to the students’outdoors activities has changed independent and positively.The practice gave the good influence to students’“Standpoint and Attitude”．The practice was effective in“Understanding and Goodwill”to nature. There was a difficulty of controlling the influence by the weather when doing outdoor sports