The relation between the development of feeding organs and feeding modes of the anchovy [Engraulis japonica]

The present study deals with the structure of feeding organs, and food at the larval stage or shirasu of the anchovy Engraulis japonica (HOUTTUYN). In this paper are discussed the relation between the development of feeding organs and feeding modes. For this study, some 36, 000 anchovies are collected mainly from catches by shirasu boat seiners operating in the Suruga Bay from 1968 to 1976. Feeding organs of anchovy larvae remain underdeveloped. For example, the mouth and the esophagus of a larva 10.3 mm TL. are as small as 1/30 and 1/20 of those of an adult 130.8 mm TL., respectively. The porosity of gill rakers of 0.04-0.20 for larval stages which represents filtering efficiency and the open area ratio of 0.40-1.06 for the same stages are only 1/15-1/30 and 1/2-1/4 of those for the adult, respectively. These values reach constant levels at 80 mm TL. The “biting lunge” in anchovy larvae is a peculiar feeding mode for these larvae that have still underdeveloped feeding organs.