Learn About Sea Anemones & Relatives

There are 20 or more large and conspicuous sea anemones that can be seen intertidally or encountered subtidally by SCUBA divers in the northwest coast of North America. 

NOTE  lit. “wind flower” G., referring to a a common large flower (ranunculaceans) widespread in temperate areas.  Early references (e.g., in the 1550s) to anemones in English literature are to the flower while the designation “sea” anemone does not appear until the 1770s

ANIMATION of snail meeting an ANEMONE
© 2010 Thomas Carefoot

To learn about west-coast SEA ANEMONES: select a topic from the Cnidaria > Sea anemones & relatives menu at the top of the page

OR: play the ANIMATION of the snail meeting the ANEMONE

OR, if you want to see other animations: follow the snail on its ODYSSEY by CLICKING on any X-marked invertebrate on the map

Phylum Cnidaria (lit. “nettle-bearing” G.), referring to the nematocysts possessed by all members of the phylum; includes sea anemones, corals, sea pens, gorgonians, jellyfishes, hydroids

Class Anthozoa (lit. “flower animal” G.), including sea anemones, sea pens, soft corals, and cup corals

Subclass Hexacorallia (=Zoantharia) (lit. “six coral” G.), referring to six sets of mesenteries

Order Actiniaria (lit. “beach/seashore” G.), including sea anemones such as Anthopleura, Urticina, Epiactus, Metridium, Cribrinopsis, and others

Order Ceriantharia, including tube-inhabiting, burrowing anemones such as Pachyceriathus imbricata

Order Corallimorpharia (lit. “coral form” G.), including Corynactis californica

Order Scleractinia (lit. “hard” G.), including cup corals Balanophyllia spp.

Order Zoanthidea (=Zoanthiniaria), including epizoanthids Epizoanthus scotinus

NOTE references to Metridium senile in the scientific literature on west-coast sea anemones likely included 2 species, now separated into a larger (up to 1m in height), subtidal species known as Metridium farcimen (= M. giganteum) and 2 smaller, intertidal/subtidal species designated M. exilis and senile.  When it is clear that the larger species is being referred to in a research paper, the name M. farcimen is substituted. For a morphological, biochemical, and genetical analyses of the Metridium spp. complex see Bucklin & Hedgecock 1982 Mar Biol 66: 1.

In a later study on the same research topic of the Metridium complex, another set of authors asks, “how did an organism as conspicuous as M. giganteum escape formal description until now?”. The question is not really a fair one, as the authors of the 1982 paper do describe its presence, but just fail to provide a name for it. Fautin et al. 1989 The Wasmann J Biol 47: 77.

NOTE in a recent paper a consortium of Russian and Canadian scientists splits the commonly designated snaklock anemone Cribrinopsis fernaldi into two species based upon morphological and molecular data. The first, the one we usually typify as C. fernaldi, is larger with longer tentacles, has a conspicuous ring of marginal projections (verrucae) around the top of the column, has a white column with pinkish tentacles, and usually inhabits muddy bottoms. The other, now designated as C. rubens n. sp. is smaller with shorter tentacles, unformly red or white in colour, and inhabits rocky habitats. The two species also differ in their complements of cnidae (nematocysts). Sanamyan et al. 2019 Mar Biodiv https://doi.org/10.1007/s12526-019-00956-w. Inset photograph of verrucae courtesy Neil McDaniel, BC.

photographs showing snakelock anemone Cribrinopsis fernaldi with close view of protuberances (verrucae) on top rim of column photograph of Cribrinopsis rubens
Snakelock anemone Cribrinopsis fernaldi with inset photo showing close view of verrucae on the upper column rim 0.6x Sea anemone Cribrinopsis rubens n. sp. on rock wall showing red and white colour morphs 0.75x