In vitro studies on Patiria Mininata (Brandt) coelomocytes, with remarks on revolving cysts

Abstract Coelomic fluid from several Patiria miniata , pooled in test tubes and maintained at 4°C, will form sheet-like cell clots in about 24 hours. The clots probably begin as monolayer syncytia on the lower walls of the test tubes and later contract and thicken. The clots are reversible and in 48–96 hours, cells making up the clots begin to scatter away from each other. One-fourth of the hanging-drop preparations made from the clots and kept at 4°C stayed in good condition for three weeks. Only one type of coelomocyte occurs regularly in Patiria and probably in most other asteroids as well. It is a phagocytic amebocyte. In normal starfish the coelomocytes have bladder-like ectoplasmic extensions; under conditions which induce clotting the coelomocytes become filiform amebocytes; and finally, when present on a clot edge or when applied to a surface such as a coverslip, they develop broad, ruffled or crinkled pseudopodia. Carmine-filled coelomocytes were withdrawn from Patiria inoculated 74 models capable of yielding basic information applicable to many echinoderm groups. Origin and function of the revolving cysts remain obscure. We know some cysts contain phagocytic elements which may be coelomocytes, and the cysts must gain their propellent flagella from one of the flagellated tissues adjacent to the coelomic cavity, perhaps by phagocytes partially ingesting flagellated cells. In vitro , coelomocytes do engulf flagella-bearing cells and the flagella may remain beating for at least some time after the parent cell is incorporated into the phagocyte. Single flagella with the attendant small bits of matter must also be phagocytized as foreign bodies, for they are not normal to the coelomic fluid. If formed by coelomocytes in conjunction with many separate flagellated cells, the cyst-like nature of the completely formed bodies might be induced by the same forces which form the zooids of Volvox and related flagellated colonial protozoans. On the other hand, some uncolored cysts occured in coelomic fluid where nearly all the single coelomocytes had particles of carmine in the cytoplasm, casting doubt on the invariable presence of free coelomocytes in the cysts 1 . The occurence of cysts in coelomic fluid just removed from apparently normal Patiria deserves comment. In the process of taking starfish from their environment some tube feet are usually torn and other wounds may occur even when great care is taken. These breaks might release bits of the flagellated epithelium into the coelom where by some process they form into the revolving cysts. It is just as likely that wounds normally acquired would accomplish the same end. Judging from the long life of revolving cysts in hanging drops, one might assume they would last as long or longer in the coelomic cavity since days earlier with carmine, indicating inert foreign material may remain in this species of starfish at least 74 days. Spherical multinucleate macrophages measuring up to 275 microns in diameter occured in the coelomic fluid of carmine-inoculated starfish. They also were present in fresh clots prepared from coelomic fluid of normal starfish. Flagellated cells, minute flagellated corpuscles, and variously-shaped crystal-like bodies were found in coelomic fluid withdrawn from normal starfish. These were probably present adventitiously and were aspirated into the needle from coelomic lining or pyloric caeca. Spherical revolving cysts were found in the coelomic fluid of normal starfish. They sometimes contained coelomocytes as well as flagellated cells but we could not ascertain if they always included coelomocytes. They were not ciliates or abnormally-developing larvae. Sperm were not involved in their formation. At least part of their origin must be in cells or groups of cells from the flagellated coelomic lining. They maintained their integrity and continued revolving up to 73 days in hanging drops, even after all other cells in the drop were lysed or granular, and even in the presence of numerous apparently nonpathogenic bacteria.