ABSTRACT
Fine structure of the spherulocytes of the holothuroid Holothuria tubulosa (Echinodermata).
Two distinct types of spherulocytes occur in the general body cavity of the holothuroid Holothuria tubulosa. Type A spherulocytes correspond to the colourless spherulocytes already described in holothuroids and echinoids. Though also colourless, type B spherulocytes show striking morphological similarities with the red spherulocytes of echinoids. It is hypothesized that type B spherulocytes would fulfil similar functions as the red spherulocytes of echinoids, viz, the protection of the holothuroid against invading microorganisms through the secretion of particular toxines.
