In some species of sea urchin, such as Lytechinus variegatus beta-1, 3-glucanase activity is present at two distinct developmental stages (in the unfertilized egg and again following gastrulation). There is a different form of the enzyme beta-1, 3-glucanase specific to each stage, and these forms can be distinguished immunologically and biochemically. The distinguishing characteristics of the egg and embryonic enzymes were used to analyze the forms of beta-1, 3-glucanase present in other species that express activity at only one of the two stages. The enzyme present in Tripneustes esculentes, which has activity only early in development, is an 80,000 dalton enzyme antigenically similar to the egg enzyme in Lytechinus. The enzyme present following gastrulation in Echinometra lucunter, however, is distinct from the egg enzyme and is similar to the embryonic enzyme in Lytechinus, despite the absence of activity in the eggs of Echinometra. These results indicate the two forms of beta-1, 3-glucanase (egg and embryonic) are expressed independently and in a stage-specific manner, suggesting they are not functionally equivalent. beta-1, 3-glucanase activity was also analyzed in interspecific hybrids. Tripneustes esculentes (which normally lacks the embryonic form) suppressed the expression of the embryonic enzyme in crosses with Lytechinus variegatus (which normally does express it). This suppression occurred whether the Tripneustes genetic material was maternal or paternal in origin. However, the embryonic enzyme normally expressed by Echinometra was expressed in crosses of this species with Tripneustes, i.e, Tripneustes did not suppress enzyme expression in these hybrids.(ABSTRACT TRUNCATED AT 250 WORDS)