JAPANESE JOURNAL OF ECOLOGY

In winter only about five species of fish larvae were collected and in summer they increased to about 30 species. Larvae of fishes were most abundantly collected during June to August and the eggs were abundant in the period of April to July. In winter both were scanty. The variations of total catch were subject to increment or decrement of the eggs or larvae of Sardinops melanosticta (T. et S.), Engraulis japonica (HOUTTUYN), Cololabis saira (BREVOORT) and Upeneus bensasi (T. et S.). Comparing with those in the adjacent waters of the Goto Islands, the period of occurrence in this area was shorter and later in most species, and several species were common in the Oki area but scarce in the Goto area. The dominant species were Sardinops melanosticta and Etrumeus micropus (T. et S.) in Spring, Engraulis japonica and Upeneus bensasi in summer, and Goniistius zonatus (C. et V.) (or G. quadricornis (GUNTHER)) and Labracoglossa argentiventris PETER in autumn.

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Some ecological characters of individuals were compared among four populations of the almond moth. The populations were bred for about 20 generations under the experimentally controlled conditions. When the food was supplied at an interval longer than the mean length of a life cycle of the moth, the duration of the developmental period of the individuals becomes longer than that of the individuals in the population with short interval of food supply. The individuals in the population which had been parasitized with the Ichneumon wasp, Nemeritis canescens GRAV., become slower in their development and slightly lower in their susceptibility to the parasitoid wasp than the individuals in the population free from its parasitization. These differences of the ecological characters of the individuals among populations may be caused by the action of the different mechanisms of density regulation. The individual difference of the head width of the moth can not be seen among these populations.

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Um die Beziehungen unter den Oribatidenzonosen, Pflanzendecken und Bodencharakteren zu suchen, wurde in Oku-Nikko-Gebirge eine zonologische Untersuchung durchgefuhrt. Als die Untersuchungsstellen wurden 18 Bestanden von verschiedenen Vegetationstypen, die im Untersuchungsgebiete typisch treten, gewahlt. Zuerst erscheinen hier Beschreibungen jeder Pflanzendecke und Bodenschicht bis zu 20cm Tiefe. Ferner sind die gefundenen Oribatidenarten und ihre Fundorten in einer Tabelle zusammenfassend hinzugesetzt.

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Some laboratory experiments concerning food consumption were carried out on Strongylocentrotus intermedius. The animals eat a wide variety of sea-weeds. The daily amount of food eaten per adult specimen (ca. 50mm in test diameter) varied largely among different kinds of sea-weeds ; the largest amount of food eaten was about 3g in wet weight when supplied with Laminaria japonica and the lowest was about 0.5g in Ulva pertusa. These values correspond to respectivelly 6 per cent and 1 per cent of the body weight of the sea urchin. Marked decline in the daily amount of food eaten per adult specimen of sea urchin was between July and October, while such decline was not recognized in the young specimen. The above restriction of the feeding of the adult urchins may bs attributed to some physiological factors correlated with gonadal development. The daily rate of feeding decreased as the urchin grew larger. However, there was no significant difference of sea urchins of different size in their ability to assimilate the food eaten. Assimilation efficiency increases with rising water temperature and vice versa ; the mean value of assimilation efficiency was about 70 per cent in summer and about 55 per cent in winter, when Laminaria japonica was supplied as food for the sea urchins. The amount (in dry weight) of food (Laminaria japonica) assimilated kept a high level (ca. 270mg/day/individual)during February to June and fell to about 50mg/day/individual in September and October.

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