A new type of gap junction in the phylum Brachiopoda.

Gap junctions in the phylum Brachiopoda are shown to be of the P type as has been previously reported in invertebrates only in molluscs and possibly bryozoans. However, the mollusc gap junctions appear identical to vertebrae gap junctions in the fracture face on which particles remain, in particle spacing and in particle arrangement. The brachiopod gap junction, on the other hand, has general appearance traits which are more commonly seen in other invertebrate gap junction types. The freeze-fracture appearance of the brachiopod gap junction is described and discussed in relation to other types of gap junction which have been reported.