Dead Man’s Fingers, Codium Fragile

Scientific Name: Codium Fragile
Common Name(s)
: Dead Man's fingers

INVASIVE to MAINE                                                    Images to come.

Research Summary
: Dylan D. and Matt M.
While we were researching there were not a lot of resources easily found on this species, however there are a lot of interesting facts.  like when a piece of the seaweed breaks off and lands in another area it can re-establish there.  Something we found surprising was that the only thing that eats the Codium fragile species is a sea slug. Some of the most important things we found while doing this research was that Codium fragile is all over the U.S.A and some people eat the species.

Identifying Characteristics

  • Codium fragile is a very slimy, spongy algae. 
  • Dark green algae that resembles a cushion of tissue.
  • The segments look like dark green fingers.
  • Can grow up to 36 inches (91cm).
  • Attaches by a broad sponge-like hold-fast.
  • Juvenile stages appear as fuzzy moss-like mats.
  • Bleaches white when washed up on shore.


Taxonomy of Species
   Scientific Classification
 What That Classification Means
 Kingdom  Protoctista
 Eukaryotic, one or many celled,
 Phylum  Chlorophyta
 The green algae. 
 Class  Chlorophyceae   Algae distinguished chiefly by having a flip like tail (flagella) and a clear 
 green color.
 Order  Codiales
 An order of Caulerpales which contains algae that lack any diving walls. 
 They are put into three different orders. 
 Family  Codiaceae
 The codiaceae are a family of algae, specifically of the Bryopsidales.
 Genus  Codium   The genus for seaweed.
 Species  Fragile
 This species can easily break, they are very fragile

Similar species include: Codium edule, velvet horn seaweed.

Location and Movement
Origin/ Native Range  Is native to Japan.
 Codium fragile was first seen in the United States in 1957 on Montauk Point, Long Island Sound,
 New York.
Spread of Species
  • Is spread by reproduction of fragments.  
  • Humans have played a part of spreading this species because they were transporting shellfish to different parts of the country.
  • Attaches to rocks, shells, ship hulls.
Where is it now invasive?
  • Is very invasive in a place called Wareham, Massachusetts and throughout the Gulf of Maine.
  • Canadian locations include: Lunenburg Bay, Nova Scotia, Mahone Bay, Nova Scotia, St.Margarets Bay, Nova Scotia, Peggy Cove, Nova Scotia

Is this species in Maine?
Where has it been identified?
  • Populations near the seacoast were small until the 1960s when they began to spread south from Boothbay Harbor, Maine, where it was introduced to Maine.  
  • Spread south in the Gulf of Maine and was identified at Nubble Light, on Cape Neddick, Maine in 1985, spreading further to the Isles of Shoals which is in Gulf of Maine.
  • Is now identified in Wareham, Massachusetts and throughout the Gulf of Maine.
How was this species introduced  Was introduced by fishermen transporting shellfish to Maine.

Natural Environment
  • Can be found in permanent tide-pools and in shallow waters along the coast line. 
  • It attaches itself to clams and shellfish.
Climate and Temperature Range
  • Adult temperature -2 to 34 degrees Celsius.
  • Reproductive temperature range 10 to 24 degrees Celsius.
  • Adult salinity range 12 to 40 ppt. (parts per trillion).

Ecological Interactions  It is a producer
 Obtains its nutrients through photosynthesis.
Consumed By
 Is consumed by the sea slug.  

  • Codium will often make its home on and attach itself to the shells of oysters, scallops, and clams. This can cause problems because an attached adult plant can hinder the movement and feeding of the shellfish. 
  • Codium fragile is a killer to shellfish by making a home on top of the shellfish causing it to be smothered.
  • It is very buoyant and as it floats with currents and waves it can pull the shellfish to shore.
Human  Some cultures eat this species.
Economic  Codium could maybe have a multi-million dollar effect on the regional shellfish economy.

Biological  The sea slug eats Codium fragile and is a suggested method to control large populations.
  • Some ways to mechanically remove Codium fragile are trawling, dredging, cutting, and suctioning.  
  • Removing by hand, which requires time and labor.
 Cultural  It has been suggested to prevent this alga by using ropes nets and boat hulls.
  • Using chemical herbicides is not an option but they are debating about using sea slugs to kill the species or mechanically remove Codium fragile.
  • These herbicides have to come in contact with this seaweed for any effect. 
  • For these herbicides to work they have to use large doses, which may impact surrounding species.

Interesting Facts
  If pieces of the seaweed breaks off it can re-establish in another area.