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PHYCOLOGICAL SOCIETY OF AMERICA

Morphology

General Description

Antithamnion has filamentous, axial growth, meaning it has definitive axes of growth made up of a chain of single cells. Its base is prostrate, cells are uninucleate, and gland cells are cut off from the vegetative cell. Species of Antithamnion are generally separated by four characteristics [14]:

1. form of whorl-branchletes

2. number of carpogonial branches in an indeterminate branch tip

3. the position and form of the branchlets bearing gland cells

4.the location of indeterminate lateral branches in relation to each other on the main axis and in relation to the whorl branchlets on the cell to which they are attached

How do you tell apart the three similar species on the central California coast?

The best way to tell apart A. defectum, A. dendroidem, and A. kylinii is to look at the branching. A. dendroidem has no branching of its determinate branches, as can be seen in the first sketch below on the left. A. defectum and A. kylinii both have pectinate branching (only on one side of the axis) of their determinate branches. A. defectum uniquely lacks a determinate whorl-branch on the opposite of the axis where the indeterminate branch is located, as can be seen in the middle drawing below. A. kylinii has an opposite whorl-branch for each of its determinate branches, as can be seen below on the right. [15]

In addition, the gland cells (whose function is discussed below) are located in different places on A. dendroidem and A. defectum. In A. defectum the gland cell is located on the tip of the branch as seen to the right, and in A. dendroidem they are located at the base of a branch as seen below. I am unaware of where they are located in A. kylinii.

Gland cells are also commonly referred to as vesicle cells or secretory cells. They contain a sulfated, acidic polysaccharidic material, and any other cell structures such a nucleus and chloroplasts degrade when the gland cell matures. Active secretion of this polysaccharidic material does not occur, nor are there any organelles designed for extracellular secretion. This evidence suggests that the gland cells do not have a secretory function, but possibly a storage function of some kind. [16] A recent study found that bromide was required for both maintenance and initial formation of gland cells in red algae, although more studies are needed to fully understand the function of these cells. [17]

Size

Antithamnion is relatively small, as can be seen by the size of it in my hand on the left, and in this small petri dish on standard graph paper above.

 

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References and Acknowledgements

© 2005 Charlotte Stevenson