Phylogeny & Ontogeny

The hagfish, an Agnathan cyclostomes is the most primitive of true vertebrates as evidenced by its formed, circulating RBC and haemaocytopoietic tissue in the submucosa of the gut tract.(1) Interested in the phylogeny of the IR the authors were prompted to ship from the Scripps Institute of Oceanography and the kindness of Dr. David Jensen, about 120 California hagfish to explore this question. IR was characterized by 3 parameters: 1formation of circulating specific Ab post Ag stimulation 2-development of delayed sensitivity post sensitization and 3-rejection of genotypically different donor grafts. The authors were particularly interested in the phenomenon of anamnesis. The results of their findings, in the California hagfish, demonstrated their apparent inability to form circulating Ab, to develop delayed sensitivity, and reject homografts. This was correlated with the lack of lymphoid cells and ability to produce an IR.