THE REACTION OF TWO STARFISHES, PATIRIA MINIATA AND ASTERIAS FORBESI, TO FOREIGN TISSUE IN THE COELOM

¹ Department of Zoology, Cornell University, Ithaca, New York

1. Two starfishes, Patiria miniata and Asterias forbesi, were found to discriminate between coelomic implants of homologous and heterologous pyloric caecum obtained from donors of these species and of two others, Asterias vulgaris and Henricia sanguinolenta.

2. Homologous transplants were recovered from the hosts one to five weeks after implantation and were found to be generally normal in histological appearance, although there was some growth of connective tissue and amebocyte masses in areas which had probably been damaged during the implantation procedure. Heterologous transplants were eliminated by the hosts within a week of implantation.

3. Henricia caecum was eliminated through the dermal branchiae by both hosts. Patiria, in contrast, eliminated Asterias caecum in a still undetermined way; the tissue may have been transferred from the host ray to the cardiac stomach, and either digested there or passed out through the mouth.

4. Contrary to expectation, amebocytic attack, phagocytosis, and encapsulation were not seen to play an important role in elimination of heterologous transplants, although amebocytes were associated with damaged areas in the homologous transplants. Such amebocytic activity is probably concerned with removal of cellular debris.

5. The results of these experiments may express a general tendency of starfishes to distinguish between implants of donors of different degrees of relationship, or they may represent special cases of discrimination. More work remains to determine how specific these tolerance-rejection thresholds are and how consistently they vary with different host-donor combinations.