Description: This benthic, colonial, feathery-shaped hydroid has hydranths enclosed by a true hydrotheca, but the hydrotheca is not large enough to cover the entire hydranth when it is contracted, and it does not have an operculum. The hydranths are only on one side of the colony branches, and attach directly to the branches rather than having their own distinct stalks (photo). It has about 3 small nematophores associated with each feeding polyp (photo), which articulate with the branch they are attached to (so they are movable). Plumularia does not release its medusae (photo) but does release planula larvae. This species has no hydrothecae on the main stalks, but some of the medusae are attached there so gonozooids must be there (photo). On the branches (hydrocladia), it has polyps on every other segment (internode), but the constrictions forming the internodes are not strongly demarcated with annular ridges (photo). Colony to 5 (15) cm tall.
How to Distinguish from Similar Species: Of common featherlike hydroid colonies,Aglaopheniais larger and has nematophores which do not articulate and so are not movable, plus has distinctive corbulae. Abietenaria inconstans has feeding polyps on both sices of its branches plus has opercula. Obelia dichotoma has hydranths on individual distinct stalks.
Geographical Range: Cosmopolitan; Alaska to California on the American Pacific coast.
Depth Range: Intertidal to 133 m.
Habitat: Attached to rocks or floats; common on kelp holdfasts or stipes.
The nudibranch Dendronotus
albus has been seen on and may feed on these hydroids.
Kozloff, 1987, 1996
Schuchert, Peter, 2014. High genetic diversity in the hydroid Plumularia setacea: a multitude of cryptic species or extensive population subdivision? Molecular Phylogenetics and Evolution 76: pp 1-9
General Notes and Observations: Locations, abundances, unusual behaviors:
Authors and Editors of
Salish Sea Invertebrates web site provided courtesy of Walla