STRUCTURE AND PROPERTIES OF HYALINE SPHERES IN HOLOTHUROID LARVAE

The structure of the hyaline spheres (I-IS) in the larvae of the holot huroids Parastichopus californicus and Stichopus japonicus was examine d by electron microscopy, and their sensitivity to a range of hydrolyt ic enzymes was tested. The HS are attached to epithelium and extend in to the blastocoel. They consist primary of extracellular material but scattered cells surround them, and a few are found within matrix. Ultr astructurally, the matrix has a gel-like appearance and contains fine granules and fibrils. HS are dissolved very specifically by hyaluronid ase (IO mg/ml, pH 5.4). Pronase, trypsin and papain at the same concen tration damage both HS and the larval body to varying degrees. Surpris ingly, HS sink when isolated from the larval body, so it is unlikely t hey serve as flotation devices. It seems more likely they serve as sto rage of structural elements utilized after metamorphosis.