Distribution patterns of photosymbionts in the host colony

Location of the photosymbionts is different among the host species.
The schematic drawing below shows the cross section of the host colony and the location of the photosymbionts (mainly Prochloron).
The three host species in red letter (i.e., Trididemnum clinides, T. nubilum and T. solidum) do not harbor Prochloron but other cyanophyte species.
The distribution pattern is closely related to the mode of transmission of the algal cells from the parental colony to the progeny (embryo and larva).