Colony Specificity in the Marine Bryozoan Dakaria subovoidea

Abstract

There is little information about colony specificity (allorecognition) in bryozoans. We examined the presence of colony specificity in the bryozoan Dakaria subovoidea, a common species on the Japanese coast. When two colonies made contact with each other at their growing edges, four types of reactions were observed: (1) overgrowth onto the opposing colony, (2) bilaminar erect growth, (3) nonfusion reaction, and (4) fusion reaction. When one of the growing edges was in poor condition, the first type of reaction was observed in both allogeneic and autogeneic combinations. The colony that was in poor condition was always overgrown with the good one. When both of the growing edges were in good condition, one of the other types of reactions was observed. In the second type of reaction, the colonies recognized the opposite colony as if it were a substratum and grew so as to form a standing wall. The third type of reaction exhibited the degeneration of zooids at the contact area. In this case, there were no fused zooids at the contact area. The fourth type of reaction was the fusion of colonies leading to the formation of contact border pores between zooids of the two colonies and sometimes to the formation of fused zooids at the contact area. The contact border pores exhibited unique morphology, which has not been reported previously. In this case, both colonies continued to grow harmoniously in direction in the same plane. These results suggest that colony specificity exists in D. subovoidea, as found in other sessile colonial marine organisms.