STUDIES ON HOLOTHURIAN COELOMOCYTES. II. THE ORIGIN OF COELOMOCYTES AND THE FORMATION OF BROWN BODIES

¹ Department of Zoology, University of Washington, Seattle 5, Washington

1. Coelomocyte and brown body production were studied in four species of holothurians, Cucumaria miniata, Eupentacta quinquesemita, Parastichopus californicus, and Psolus chitonoides.

2. Available evidence suggests that at least some, if not all, lymphocytes possibly originate from mesenchymal cells in the hemal vessels of holothurians, and possibly later differentiate directly into hemocytes, amebocytes, and morula cells.

3. The coelomic fluid of Cucumaria and Eupentacta contains coelomocytes which can be arranged in a series intergrading between lymphocytes and hemocytes. These cells possibly represent stages in the transformation of lymphocytes into hemocytes.

4. Parastichopus and Psolus, which lack hemocytes, do not possess the series of cells interpreted as stages in hemocyte differentiation.

5. All four species of holothurians studied possess coelomocytes which can be arranged in a series intergrading between lymphocytes and amebocytes. These cells possibly represent stages in the differentiation of lymphocytes into amebocytes.

6. Granular lymphocyte-like cells located in the hemal vessels of the four species studied possibly represent stages in the differentiation of lymphocytes into morula cells.

7. Cucumaria miniata, Eupentacta quinquesemita, Psolus chitonoides, and Leptosynapta clarki were injected with suspensions of lamp black in sea water.

8. The carbon particles were engulfed by amebocytes which often also contained granules similar to the granules found in brown bodies.

9. Carbon particles were accumulated in the same regions of the body as brown body material.

10. Brown bodies composed partly of carbon particles were eliminated by the holothurians.

11. Amebocytes are believed to play a role in the accumulation of brown body material and in the production of brown bodies.

12. Carbon particles were also concentrated in the ciliated funnels or urns of Leptosynapta clarki.