Dead-Man’s Fingers Algae
Codium fragile
Dead-man’s fingers are small seaweeds that originated in Japan but are now found worldwide. They have different reproduction options available and can be easily introduced in a new environment. These algae are considered an invasive species because of how they become the dominant plant species in areas where they are not native. Though they have natural predators like snails, they are not the snails’ preferred food due to the algae’s taste. However, there are some places on the planet where this algae is eaten regularly by humans!
Originally published: June 25, 2024
Last updated: January 23, 2026
SPECIES IN DETAIL
Dead-Man’s Fingers Algae
Codium fragile
CONSERVATION STATUS: Invasive Species
CLIMATE CHANGE:
Geographic Distribution
Originating off the coast of Japan, it can now be found worldwide in temperate waters.
Habitat
They are found year round at open coasts, estuaries, tide pools, and intertidal and subtidal zones. They attach to rocks, shells, and other hard substrates. Dead-mans fingers can be found in sheltered habitats such as bays and harbors. They are able to grow in shallow coastal waters up to 15 meters in depth.
Physical Characteristics
Dead Man’s Fingers is a dark green algae with thick, felt-like branches. The branches are either cylindrical or Y-shaped, giving them their finger-like appearance.
Size
These algae can grow 39—90 centimeters (15—35 omches) and weigh up to 3 kilograms (6.61 pounds) per plant.
Diet
They gain nutrients through photosynthesis (converting energy from sunlight).
Reproduction
Dead-man’s fingers algae reproduce in three ways: sexual reproduction, parthenogenetically, and asexually. First, with sexual reproduction, the male and female gametes are both produced on separate plants. Each of the gametes has two flagella, and the female gametes are larger than the male gametes. Second, they reproduce parthenogenetically where the female gamete develops into a new individual without fertilization. Third, this algae reproduces asexually, forming a genetically identical individual from a branch or stem of the parent plant.
Behavior
Dead-man’s fingers are considered an invasive species. They can be found wrapped around places like dock pilings. They use their roots and branches to wrap around shells, so much so that they can even stop the invertebrates inside from moving and may even dislodge them completely! This algae is likely to displace the native seagrasses and seaweed due to its fast growth.
Adaptation
This algae is well adapted to areas of low sunlight, making it easy to spread in developed coasts, especially under human made structures like piers and harbors. Its dense bush like structures makes it harder for fish swim through.
Conservation
Dead-man’s fingers algae is an invasive species, having the ability to overtake native kelp species worldwide, which then displaces the animals that call that forest home. It’s especially known for overtaking oyster beds. This algae is edible and also used as feed in mariculture.
Special Notes
At one time dead man’s fingers were used as packing material for shipping live marine invertebrates!
SPECIES IN DETAIL | Print full entry
Dead-Man’s Fingers Algae
Codium fragile
CONSERVATION STATUS: Invasive Species
CLIMATE CHANGE:
Originating off the coast of Japan, it can now be found worldwide in temperate waters.
They are found year round at open coasts, estuaries, tide pools, and intertidal and subtidal zones. They attach to rocks, shells, and other hard substrates. Dead-mans fingers can be found in sheltered habitats such as bays and harbors. They are able to grow in shallow coastal waters up to 15 meters in depth.
Dead Man’s Fingers is a dark green algae with thick, felt-like branches. The branches are either cylindrical or Y-shaped, giving them their finger-like appearance.
These algae can grow 39—90 centimeters (15—35 omches) and weigh up to 3 kilograms (6.61 pounds) per plant.
They gain nutrients through photosynthesis (converting energy from sunlight).
Dead-man’s fingers algae reproduce in three ways: sexual reproduction, parthenogenetically, and asexually. First, with sexual reproduction, the male and female gametes are both produced on separate plants. Each of the gametes has two flagella, and the female gametes are larger than the male gametes. Second, they reproduce parthenogenetically where the female gamete develops into a new individual without fertilization. Third, this algae reproduces asexually, forming a genetically identical individual from a branch or stem of the parent plant.
Dead-man’s fingers are considered an invasive species. They can be found wrapped around places like dock pilings. They use their roots and branches to wrap around shells, so much so that they can even stop the invertebrates inside from moving and may even dislodge them completely! This algae is likely to displace the native seagrasses and seaweed due to its fast growth.
This algae is well adapted to areas of low sunlight, making it easy to spread in developed coasts, especially under human made structures like piers and harbors. Its dense bush like structures makes it harder for fish swim through.
Dead-man’s fingers algae is an invasive species, having the ability to overtake native kelp species worldwide, which then displaces the animals that call that forest home. It’s especially known for overtaking oyster beds. This algae is edible and also used as feed in mariculture.
At one time dead man’s fingers were used as packing material for shipping live marine invertebrates!