貝類補食者アカムシHalla okudai(多毛綱)の餌選択性について

• Main Authors: Saito, Hidetoshi, Imabayashi, Hiromichi
• Format: Report
• Language: Japanese
• Published: 広島大学生物生産学部 2014
• Subjects: 餌選択性; 多毛類; アカムシ; アサリ; 二枚貝; Food preference; Polychaete; Halla okudai; Ruditapes pilippinarum; Bivalve; 660; Crassostrea gigas
• Online Access: http://ir.lib.hiroshima-u.ac.jp/00024682; http://ir.lib.hiroshima-u.ac.jp/files/public/2/24682/20141016145807179179/53-0551.pdf; https://doi.org/10.15027/24682

貝類捕食者である多毛類アカムシ Halla okudai の餌選択性を、野外調査および室内実験の双方から検討した。アカムシの主要な生息干潟(1.4個体/㎡)では、卓越順にホトトギス、ムラサキイガイ、アサリ、マガキ、オニアサリなどの二枚貝が混生していた。これら5種類の二枚貝に対する種類選択性実験を行い、30日間の摂餌数からイブレフ選択指数(E)の平均値を算出すると、アサリ0.61、ムラサキイガイ-0.49、オニアサリ-0.85、ホトトギス-0.90、マガキ-1.00となり、アサリは他の4種類と比較して極めて有意に選択・捕食された。アサリに対するサイズ選択性実験において、60日間の摂餌数から小型・中型・大型アサリの平均E値を算出すると、小型アカムシではそれぞれ0.05、-0.05、-0.29、中型アカムシでは-0.10、0.02、-0.02、大型アカムシでは-0.14、-0.11、0.13となり、成長に伴って選択・捕食するアサリも大型化する傾向がみられた。 Food preference of the molluscivorous polychaete Halla okudai were examined in field sampling and laboratory experiment. Bivalves such as Musculs senhousia, Mytilus edulis, Ruditapes philippinarum, Crassostrea gigas and Notochione jedoensis dominantly inhabited the intertidal flat, Hiroshima Bay, in which the polychaete was abundant. The preference for these five species of bivalves were indicated by IVLEV's electivity index (E), based on the number of bivalve eaten during 30 days. Mean values of the electivity index were as follows; 0.61 in R. philippinarum, -0.49 in M. edulis, -0.85 in M. senhousia, -0.90 in N. jedoensis and -1.00 in C. gigas. R. philippinarum was more significantly selected than the other four bivalves. As for the preference for different size of R. philippinarum eaten during 60 days, electivity index was calculated on small-, middle and large-sized bivalves, respectively; 0.05, -0.05 and -0.29 in small polychaete, -0.10, 0.02 and -0.02 in middle polychaete, -0.14, -0.11 and 0.13 in large polychaete. Thus, the polychaete tended to feed on large bivalve with increased age.