The Chlorella cell wall is made of indigestible cellulose, just like green grass, WHILE the cell wall of Spirulina is made of complexed proteins and sugars.As noted, Spirulina has a soft cell wall made of complex sugars and protein, and is different from most other algae in that it is more easily digested.As stated earlier, an enzyme called biliverdin reductase, converts the biliverdin to unconjugated bilirubin.
Spirulina provides all the required amino acids, and in a form that is five times easier to digest than terrestrial meat or soy protein.
An analogy used at a pet food seminar I attended was this: You can achieve the protein analysis on many pet foods with a used pair of leather shoes, but leather shoes contain little usable proteins.
An animal (fish for our purposes) produces unconjugated biliverdin, a yellow colored breakdown product of normal heme catabolism, formed by failing red blood cells.
Heme (also called Haem in the UK) is composed of iron plus amino acids from globin of hemoglobin.
The primary species of Spirulina are Arthrospira platensis and Arthrospira maxima.
Another species is Spirulina fusiformis; it is a freshwater algae as opposed to Marine/Saltwater species of the commonly harvested/aquacultured species noted earlier. Arthrospira fusiformis is capable of a great deal of polymorphism, it changes its shape, color and other charastistics in adapting to its environment.
A circulating erythrocyte is little more than a container for hemoglobin; Erythrocytes which have a 120 day life span transport oxygen and carbon dioxide between the gills/lungs and all the tissues of the body are broken down utilizing these Heme via the tetrapyrrole; biliverdin, which is then converted to bilirubin and carried to the liver by the plasma protein.
Bilirubin is excreted in bile, and its levels are elevated in certain diseases and is then transported into the cytoplasm of every cell in the body of the animal (fish).
Aphanizomenon Flos-Aquae is a related algae found in Klamath Lake Oregon (see References).
Like Spirulina, this Klamath Lake blue green algae has been shown to be very nutritionally dense, diverse and absolutely non-toxic.
Most commercial Spirulina used for human and fish food consumption primarily is grown in the USA, Thailand, India and China.