北海道厚岸湾におけるオホーツクヘラムシ Idotea ochotensis Brandt の食性と成長

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The feeding habits and growth of the marine isopod Idotea ochotensis collected from Akkeshi Bay on the Pacific coast of Hokkaido, northern Japan, were studied. Individuals of I. ochotensis were maintained in the laboratory and provided with different kinds of plant material as food. The plants used were two species of seagrass (Phyllospadix iwatensis and Zostera asiatica) and two species of seaweed (Fucus distichus subsp. evanescens and Laminaria longissima). Fresh leaves of two species of seaweed and fresh and dead leaves of the two seagrass species were provided separately, for a total of six types of food. Food preferences of mature adults were examined through pairwise feeding tests in which individual animals were offered two types of food materials simultaneously and allowed to choose between them for 24 hours. Adults consistently preferred seaweeds to seagrasses, but no clear preference was detected between the two seaweed species or between the two seagrass species. For juveniles of three size classes and mature adults, one-day rates of food consumption were compared between the different food item. Small and middle-sized juveniles ate a greater amount of Zostera asiatica and dead leaves of Laminaria longissima than other food items, but for large juveniles and mature adults, Laminaria longissima was the most eaten food. Juveniles of all size classes ate significantly greater amounts of dead leaves of Zostera asiatica than fresh leaves of that species, but no such difference was seen in mature adults. Finally, starting within 3 days after hatching, small juveniles of I. ochotensis were reared for 4 weeks on the above six different types of food. Although not statistically significant at the 0.05 level, there was a weak trend for juveniles provided with their preferred food grow larger than those provided with a less preferred one. Inspection of the gut contents of field-collected individuals revealed that I. ochotensis in Akkeshi Bay feeds mainly on seaweeds and takes only a small amount of seagrasses, as expected from the results of the laboratory studies.
日本ベントス学会の論文
2002-06-27

北海道厚岸湾におけるオホーツクヘラムシ Idotea ochotensis Brandt の食性と成長

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