フナムシ Megaligla exotica(Roux)の週期活動 : II. 群れをなしての週期移動と体内生理要因及び潮汐週期との関連

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1) ONDO and MORI reporded the outline of the periodic journey of the shore isopod population in 1956. The present paper deals with some results of my further investigations executed at the natural habitat. 2) The isopod population migrates periodically twice a day as mentioned previously. From investigations executed at the natural habitat, it was concluded that there was no direct interrelations between the periodic journeys and changes of tidal level. They always go towards the beach early in the morning and reach the feeding places on the intertidal rock surfaces. They repeat the following characteristic behavior, i.e. when the tide rises, they retire to the high part of drift line but do not return to the resting places, on the contrary, when the tide lowers, they again return towards the drift line. Thus, the range of feeding and migration was limited by the changes of drift line in the daytime, as shown in Fig. 1. In the late afternoon, they commense their evening journey to return to their resting places just before sunset. Thus, it was ascertained that the periodic journey of the isopod population is influenced by periodicity of environmental factors as daily changes of solar illumination, but on the other hand, it was also true that the internal physiological conditions (chiefly diurnal changes in conditions of alternative hunger and satiety)and interspecific relationships are also important. From the ecological point of view, the periodic journey of the isopod population belongs to the recurrent movement. 3) An attempt was made to learn something of the nature of the physiological conditions in the detailed forms of the daily cycles of the melanophores and of the daily changes in conditions of alternative hunger and satiety. The melanophores were staged at hour intervals through 24 hours. The average stage of melanophore was determined by estimating the average melanophore state on the dorsal surface of the walking leg, antennae and dorsal surface of the body. The classification based upon HEWER's study was used, with 1…contracted, 2…slightly stellate, 3…stellate, 4…slightly expanded, 5…expanded, 6…fully expanded. A detailed analysis of the character of the diurnal changes in the melanophores of M. exotia confirmed the precision of the 24 hour endogenous rhythm as indicated in Fig. 2. On the other hand, to see clearly the changes in conditions of alternative hunger and satiety, 20-30 individuals of the same agers-as-semblage(individuals of 20-30mm body length)were collected at hour intervals through 24 hours at the natural habitat and afterwards, dissected to confirm whether their conditions of alternative hunger and satiety. Generally, all members of the agers-assemblage just mentioned taking morning journey were in conditions of hunger and those of evening journey were sufficiently fed. Therefore, the state of such internal physiological conditions affect the time when the isopod population begins to take morning and evening journeys. From these experiments, it is pointed out that the time when all members of the isopod population begin to take morning and evening journeys was synchronized with the changes in conditions of alternative hunger and satiety. These facts are indicated in Fig. 2. 4) When migrating, all members of the same population run from rock to rock. To investigate the behavior patterns, some experimental analyses were carried out under natural conditions. As a result, it may be concluded that the isopods seek an adequate pathway to the feeding or resting places with their thigmotactic sense. These results are shown in Table 1.
日本生態学会の論文
1958-04-30

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恩藤芳典
鳥取大学学芸学部生物教室

フナムシ Megaligla exotica(Roux)の週期活動 : II. 群れをなしての週期移動と体内生理要因及び潮汐週期との関連

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