Table of Contents
Dataset Papers in Biology
Volume 2013 (2013), Article ID 839671, 6 pages
Dataset Paper

Longitudinal Observation of Japanese Lancelet, Branchiostoma japonicum, Metamorphosis

1Department of Biological Sciences, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8526, Japan
2Department of Virology, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan
3Center for Marine Environment Studies, Kumamoto University, 39-1 Kurokami 2-chome, Kumamoto, Kumamoto 860-8555, Japan

Received 4 April 2012; Accepted 8 May 2012

Academic Editors: M. Kurokawa, K. Terakado, and S. Tochinai

Copyright © 2013 Takao Kaji et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The lancelet (amphioxus) performs metamorphosis and produces minute and ciliate pelagic larvae commonly found in other metamorphic marine invertebrates. During larval life and metamorphosis, however, the animal displays interesting combination of features not found in other animals such as long coexistence of ciliate and muscular locomotion and no change in feeding behavior. The uniqueness of lancelet metamorphosis can provide important data to understand the evolutionary history of this animal as well as the metamorphosis broadly appeared in metazoans. Although lancelet metamorphosis has been studied, all previous studies depended on cross-sectional observations. To get serial data on metamorphic events, we performed longitudinal observations on the Japanese lancelet under the culture condition and confirmed the following: (1) there were individual variations of the duration of metamorphosis from 15 to 27 days; (2) growth was arrested for a month and the maximum reduction of the body length (2.2%–3.2%) occurred when gill slits became paired; (3) during rather long duration of metamorphosis, the oral transformation and the division of the gill pores by tongue bar were completed within two to four days. Our observations suggest that the duration and mode of lancelet metamorphosis depend mainly on intrinsic requirements rather than on extrinsic selective pressures.