Brinckmannia hexactinellidophila, n. gen., n. sp.: a hydroid living in tissues of glass sponges of the reefs, fjords, and seamounts of Pacific Canada and Alaska

Abstract

This paper reports on an intimate association of a cnidarian with glass sponges. Hexactinellid sponges of the genus Heterochone were found to regularly contain numerous tiny hydroids in their tissue. The hydroid belongs to a new genus and species and is here named Brinckmannia hexactinellidophila. Brinckmannia hexactinellidophila is a reduced form, lacking tentacles and gonophores, which certainly is an adaptation to its endobiotic mode of life. The possession of desmonemes allows it to be classified as a member of the suborder Filifera of the order Anthoathecata. The shape of the hydranth reveals some clear affinities with the Proboscidactylidae, a relationship which is also strongly suggested by a comparison of 16S gene sequences. Because a closer relationship to some other families cannot be excluded at this stage, the new genus is nevertheless not assigned to any known family and classified as Filifera incertae sedis.