Ontogenesis of coelomocytes in sea cucumber (Apostichopus japonicus) studied with probes of monoclonal antibody

• Ontogenesis of coelomocytes in sea cucumber Apostichopus japonicus was studied.
• Antigen of spherulocytes was firstly detected from blastula stage.
• Antigen of lymphoid cells was first detected from big-auricular larvae.
• Lymphoid cells may not be progenitor cells or stem cells for A. japonicus.

Monoclonal antibodies (MAbs) specifically against coelomocytes of Apostichopus japonicus were employed to study the ontogenesis of coelomocytes by indirect immunofluorescence assay technique (IIFAT). Different developmental stages were identified by histochemical staining method. Stages including blastula, gastrula, auricularia (small-auricular larvae, mid-auricular larvae and big-auricular larvae), doliolaria, pentactula and juvenile were examined. The positive reactions with both MAb1C2 against all the types of coelomocytes and MAb3F6 specific to spherulocytes, were observed firstly at the blastula stage of the embryos. The positive reaction with MAb1E2 against lymphoid cells was observed from the big-auricular larvae, which indicated that lymphoid cells may not be progenitor cells or stem cells for A. japonicus. An increase of fluorescence intensity for each cell may imply a possible enhancement of the innate defensive mechanism as the embryogenesis progress.