Reproduction of the laboratory-maintained lancelet Branchiostoma belcheri tsingtaunese

The first description of the lancelet embryology was published by Kowalevsky in 1867, but the reproduction of laboratory-maintained animals has not yet been studied. In this study, healthy lancelets with fully-developed gonads were selected and cultured in the laboratory from 18 July 1996 to 11 August 1997 and from 25 June 1998 to 20 July 1999. The animals cultured from 1996 to 1997 were divided into three groups: female-only, male-only and female plus male (female:male =1:1), and those from 1998 to 1999 into two groups: female-only and male-only. It was found that (1) as in nature, the majority of the females and males cultured separately or in mixture in the laboratory were all capable of producing fully-grown gonads, as evidenced by the number of gonads, fecundity and diameter of oocytes; (2) none of the animals in the female-only and male-only groups spawned during the breeding season, but those in the female plus male group did; (3) the fertilized eggs obtained from the laboratory-maintained animals in the female plus male group developed normally. This appears to be the first report on reproduction of laboratory-maintained lancelets, and the results might be used to address the problem of artificial preservation of diminishing lancelet populations.