The relationship between the bryozoan Bugula neritina and its symbiont "Candidatus Endobugula sertula" is a specific yet complex model for defensive symbiosis where the host larvae obtain chemical protection from predation by symbiont-produced bryostatin. The symbiotic bacteria are located in both larval and adult tissues of the host. However, the bryostatins levels are higher in larvae and in adult zooids with ovicells where the larvae are brooded, compared to adult zooids without ovicells. In this study, symbiont cell density and bryostatin biosynthetic gene expression were quantified in host tissues, using TaqMan probe based Q-PCR, to investigate the mechanisms for the higher bryostatin content in larvae. The results showed that there are no significant differences of the symbiont cells in three tissues and the bryostatin gene expression is not different in ovicell-bearing zooids as compare to ovicell-free zooids suggesting that the host plays a role in transferring bryostatin to larvae.