二枚貝の浮游幼貝(Veliger)の識別について

Abstract

Knowledge of the larval history of bivalves, especially their identification of species in plankton samples, would be of great importance for fisheries investigators making possible reliable prediction of spatfalls and efficient collections, as well as breeding seasons of adult forms and dates of larval settlement, and would, moreover, contribute much toward the solution of a wide range of problems, both practical and academic. Up to this time little has been known concerning the larvae of most bivalves, although several extensive studies had been made by STAFFORD, KANDLER, LEBOUR, MIYAZAKI, YOSHIDA, J∅RGENSEN, SULLIVAN and REFS. In the present work the author has revealed that the identification of larval stages of bivalves should be carried out not only by the shapes of prodissoconth but also by their developmental findings and the spawning habits of adult population, the latter being classified into groups A and B as shown below. A-group (Marine form); a) Standard type, b) Protobranch type, c) Egg mass or string type, d) Incubatory type. B-group (Freshwater form); a) Glochidium type, b) Lasidium type, c) Sphaerium type, d) Corbicula type, 1) Corbicula leana type, 2) Corbicula sandai type, 3) Corbicula japonica type (Brackish). Further, having closely studied the drawings and descriptions covering some 200 species in aggregate number published by the investigators abovementioned, the present author has classified post-larvae into 20 types on the basis of definitely recognizable characteristics of prodissoconchs, which would be useful to any investigators interested.