Agar seaweed scientifically known as Eucheuma spp. is seaweeds that are most common and fast growing species in the Philippines and are found from just below the low tide mark to the upper subtidal zone of the reef, growing usually on sandy-corally to rocky substrata where water movement is slow to moderate. They grow by means of an apical meristem consisting of a group of actively dividing cells at the tip of the branches. They exhibit a triphasic life cycle, consisting of the gametophyte (n) (dioecious), carposporophyte (2n) and the sporophyte (2n).
Even though commercially significant, species of eucheuma are difficult to identify without the aid of close scientific examination, as different species may have very similar morphologies. It is assumed that eighteen to twenty species alone fall within the genus Eucheuma, represented by the groups Cottoniformia, Eucheuma, Gelatiformia, and Anaxiferae.
The thallus of Eucheuma ranges from 35 to 74 cm. Branches are brittle to cartilaginous in consistency, ranging from 7 to 9 cm in length, with whorled/spinous branchlets. The cell diameters are as follows: 2-5 µm outer cortexes, 30-196 µm inner cortex and 20-45 µm medulla. Rhizoids of the medulla are present but thylles are absent. Tetrasporangia are zonate with tetraspores ranging from 13 to 36 µm in diameter. Spermatophyte conceptacles range over 350-650 x 300-420 µm with a spermatial diameter of 14-29 µm. Cystocarps and carpospores have not been observed in this species.
Agar seaweed which is also known as Guso is seaweeds that are most common and fast growing species in the Philippines and consists of minimal amount of essential nutrients, minerals and vitamins that are essential in our daily life.