2 kinds of larval morphology which belong to the Lingulida （Brachiopoda: Lingulata） from the easten part of the Seto Inland Sea, Japan

Abstract

A large number of linguliformean brachiopod larvae were collected from off the coast of Kagawa Prefecture in the easten portion of the Seto Inland Sea, Japan. Larvae of various sizes with embryonic shells were identified as Lingula spp. with the number of cirri increasing with age up to 11 pairs. Those larvae without embryonic shells were identified as Discradisca spp. which are characterized by three stages: (1) having remarkably long embryonic setae but lacking larval shells, with up to four pairs of cirri, (2) formation of larval shells and retaining the long embryonic setae and (3) larval shells with curved setae and losing the embryonic setae. Planktonic larvae of these brachiopods are easily collected by plankton net and readily segregated into each family by means of the presence or absence of embryonic shells. Therefore, the plankton collecting is a useful method for the preliminary survey of lingulid brachiopods.