Codium is a genus of edible seaweed green algae (or seaweed) under the order Bryopsidales. The genus name is derived from a Greek word that pertains to the soft texture of its thallus. One of the foremost experts on Codium taxonomy was Paul Silva at the University of California, Berkeley.
Taxonomy and nomenclature
This genus is the largest member of the algal family Codiaceae and consequently under order Bryopsidales and it currently has about 143 confirmed species and four (4) unresolved members.
Stackhouse, unfortunately, failed to provide
holotype specimens for
C. tomentosum (type species) and some of its dichotomously branching congeners leading to misidentifications; P.C. Silva delineated
C. tomentosum,
C. fragile, and
C. vermilara and established neotypes for each species to finally resolve this taxonomic blunder.
Morphology
Being a member of the order Bryopsidales,
Codium is coenocytic and siphonous.
Their spongy thallus is composed of a single, multinucleated, branched, tubular cell called siphon which terminates at a swollen end called the utricle.
These siphons intertwine with each other to form the clear mesh-like center of the
Codium thallus called the medulla while the utricles surround this central layer to form a green to dark-green palisade layer called the cortex.
The genus has a wide variety of thalli forms: (1) mat-forming, the thalli encrusts and adheres to given a substrate using its medullary filaments; (2) spherical, the thalli forms a ball and is superficially attached to an area using rhizoidal filaments; and (4) erect thalli, typically dichotomously branched with its medulla surrounded by utricles.
Similar to most seaweed species, Codium species also exhibit a wide range of morphological plasticity which has been a great challenge to its morphology-based taxonomy.
Distribution
In terms of its natural range,
Codium has a latitudinal range that encompasses the tropical to temperate areas, however, this genus is not found in the frigid polar regions of the world.
Ireland
Two of these species are very rare in
Ireland.
Codium adhaerens has been recorded from a few sites on the west coast and from
Tory Island on the north coast in
County Donegal. In 1837 it was found in Church Bay in
County Antrim,
[Morton,O. 1994. Marine Algae of Northern Ireland. Ulster Museum. ] but has not been found there since.
There are other species of "doubtful validity":- Codium amphibium is included in William Henry Harvey's Phycologia Britannica Pl.xxxv. and noted as: "spreading in patches of great extent along the edge of the sea, over the surface of a turf-bog which meets the shore at Roundstone Bay" (Ireland).
Worldwide
Invasion of Codium spp.
Even though
Codium species are well-distributed across the globe, certain species have managed to escape their natural range and invade other areas. In the case of
C. fragile spp.
tomentosoides, commonly known as "oyster thief", the increasing marine traffic has made it possible for it to escape its natural locality (Japan) and spread to Europe and USA forcing devastating biodiversity and aquacultural losses.
Ecology
Codium has been observed to inhabit both from the intertidal zone down to the subtidal area.
Life history
Codium, like most ulvophycean seaweeds, exhibit a diplontic life history wherein the dominant diploid (2N) thallus produces the male and female gametangia that will produce the haploid (N) gametes through meiosis.
Moreover,
Codium are also capable of fragmentation, which has led to its unwanted spread across the globe.
Exploitation, harvesting and cultivation
South Korea is the leading consumer and producer of farmed
Codium (commonly known as
cheonggak) in the world; with about 4000 metric tons of fresh weight produced in 2017 and valued at 2 million US dollars.
Farming and cultivation of
Codium in South Korea is a thriving industry; their method first involves seeding a rope line with isolated pieces of utricles and medullary filaments
and finally transferring it into the open sea for the grow-out cultivation.
Chemical composition/Natural products chemistry
A recent review on the bioactivity of the genus
Codium has revealed that most of its polysaccharides, glycoproteins, galactans, anionic macromolecules, and other extracts/compounds have shown to have a variety of uses as immunostimulatory, anticoagulant, anticancer, anti-inflammatory, antibacterial, antifungal, and antiviral agent.
Utilization and Management
Codium is used either fresh or dry and is typically cooked and seasoned with soy sauce and vinegar or mixed with kimchi.
