Culture Of Amphioxus And Shark, Karyotype And C-Banding Pattern Of Amphioxus Chromosome

Amphioxus, a cephalochordate, is an important model for studies of evolution and comparative biology. The success to culture cells from amphioxus tissues will greatly to contribute in vitro approach as to study gene expression and regulation, etc. The purpose of this study is to find out and optimize the culture conditions for the proliferation of amphioxus cells in vitro. The tissues used for primary cultures were head, tail, gill, gut and metapleural fold. The media selected were L-15, F-12, M 199, MEM, DMEM and PRMI 1640. The optimal culture conditions for amphioxus cells in vitro are: medium, L-15; temperature, 25癈; and osmolarity 735 mmol kg-1. Among the tissues tested, head and tail cells grew best.Liver is an important organ in maintaining the internal homeostasis in vertebrates, and liver cell lines will be a good model for in vitro study of liver metabolism and physiology as well as for the research of toxicology and carcinogenesis. In addition, liver cell lines could be used for sources of bioactive products like liver oil. Here we have tried to initiate liver cell culture of lip shark. It was found that: (1) L-15 medium supplemented with 20% FBS best supports the growth of the cell, and (2) optimal temperature was 22 .The amphioxus cells cultured in vitro were used to study its chromosome number karyotype and C-banding pattern. It showed that the diploid chromosome number (2n) of amphioxus Branchiostoma belcheri tsingtauense was 36. The first pair of the 36 chromosomes of B. belcheri tsingtauense was subtelocentric and the other 17 pairs telocentric. This is in line with the finding that the karyotype of the amphioxus is 2n=36, 2st+34t, FN=36. C-banding analysis showed that about 54.3% (32/67) of the chromosome surface was positively stained. Around the second pair chromosomes,50% of them exhibited markedly different bands from each other. This broadly support that amphioxus chromosomes No. 2 are a pair of sex-chromosomes. In addition, the position of nucleolar organizer regions was situated on the centromeric regions of No. 12 pair chromosomes with Ag-staining method and the total number of NORs was 2. All these show that amphioxus chromosomes represent primitive types of the chromosomes of the lower chordates.