Whidbey Island Beachwatchers
 

Intertidal Organisms EZ-ID GUIDES

 

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Codium fragile (Dead man's fingers, felty fingers)

photo of "dead man's fingers" seaweed
Copyright © 2006 Jan Holmes

 

Each complement of dichotomously branching dark green "fingers" arising from one holdfast is a mass of interwoven single celled filaments.  As the seaweed matures, filaments lose their cross walls becoming multinucleate cells.  The outer texture of the fingers is soft and sponge-like.  This seaweed has no asexual (sporophyte) stage.  Male and female gametes are produced on separate plants.

 

Two sea slugs graze on Codium fragile; Elysia hedgpethi and Placida dendritica.  Both animals pierce the seaweed with their radula and suck out cellular juices.  In Elysia, ingested chloroplasts continue to photosynthesize for several days and produce a lubricant the animal uses to glide on. 

    

C. fragile can be found in the low intertidal and subtidal on high energy beaches.  Branches, up to 1 cm wide, can reach lengths of over 30 cm. 

 

On the east coast of the U.S. a closely related subspecies C. fragile subsp. tomentosoides is an introduced rapidly spreading invasive species that has been an expensive problem for shellfish farmers, and in some areas overtakes recreational swimming beaches. 

 

This page was created by Jan Holmes on 8/18/06.