Herbarium specimen of Delesseria decipiens
Division Rhodophyta -
The Division Rhodophyta includes over 4,100 species of algae commonly know as the red algae. The major defining characteristics of the division include: possession of chlorophyll a and possibly chlorophyll d and the presence of phycobiliproteins, phycocyanin and phycoerythrin, a red pigment which is primarily responsible for the algae's unique color. Reproductive characteristics include the absence of flagellated sperm (spermatia) and the possession of carpogonia on the female gametophytes. Other defining characteristics include the arrangement of the thylakoids in the chloroplasts, which are not stacked but scattered individually in the chloroplasts, and the use of floridean starch a s a storage product.
Delesseria displays all of these characteristics, as well as other characteristics common among red alga, such as pit plugs and a brilliant red color.
First described by J.V. Lamouroux in 1813 and named for French naturalist Baron Delessert, the genus Delesseria includes species from a variety of places around the world including Delesseria sanguinea from the west coast of Europe and Delesseria lancifolia from the Falkland Islands and Antarctica. Of these, most scientific research has been done on D. sanguinea, including studies of seasonal growth patterns and sensitivity to UV light. Recent genetic analysis has questioned the classification of the genus, suggesting that D. decipiens and D. sanguinea are more closely related to the genus Membranoptera then to many of the other species currently in the Delesseria genus. The blades of Delesseria species are generally thin, flat and monostomatic while the conspicuous midrib is often polystromatic. Intercalary divisions occur in Delesseria except in the primary axial cell row.
The location of reproductive structures is also an important characteristic of the genus. Cystocarps are located on fertile leaflets branching from the midrib in the female gametophyte, and have a single carpogonial branch on a supporting cell. Spermatangia on the male gametophyte are located all over the thallus of the alga. Finally, tetraspores are located on blades of the last two orders of branching along the midrib.