Ontogenetic development of the pronephros and the distribution of B-lymphocytes in adult pronephros of the mandarin fish Siniperca chuatsi

Ontogenetic development of the pronephros was examined in the mandarin fish Siniperca chuatsi, collected from the first to the 35th day post hatching (dph). Renal tubules and undifferentiated haemopoietic cells were observed on the 1st dph. The development of the pronephros was subjectively divided into three stages according to changes in its composition. At the first stage ( from the 1st to 7 dph), the pronephros mainly consisted of renal tubules and some haemopoietic cells; at the second stage (from the 7th to 35th dph) with the composition of lymphocytes and renal tubules. Afterwards, the number of renal tubules decreased and then disappeared, and the number of lymphocytes increased and adrenal gland was found surrounding the blood vessels. In situ PCR technique was successfully used to detect the distribution of B-lymphocytes expressing IgM mRNA in the pronephros of adult mandarin fish. It is shown that lymphocytes are distributed in the whole pronephros, with some of them located around the blood vessels