Monterey Bay Aquarium Research Institute
Marine Botany

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Gelidium photograph (35840 bytes)

Gelidium is a genus of red algae with a very wide geographic range. Besides being beautiful, it is an economically valuable seaweed used in the production of agar.

To find out more about this alga, click on the topics below.

Morphology and Anatomy

Gelidium is a highly polymorphic genus with a wide range in size and structure. Most species are highly branched and show a characteristic growth pattern.

Reproduction and Life History

The taxonomy of red algae is based on the complex reproductive structures and life histories. Gelidium has a triphasic, isomorphic life history.


The taxonomy of the Rhodophyta is a complex topic with many classifications still open to debate. Gelidium is a member of the order Gelidiales.

Habitat and Distribution

Species of Gelidium are found in intertidal or subtidal areas in many parts of the world. It seems to be found in greater abudance in highly wave exposed areas.


The chemistry of Gelidum is typical of the Rhodophyta. Polysaccharides from the cell wall are used for agar.


The phycocolloid agar is extracted from Gelidium and it is part of an industry that generates hundreds of thousands of dollars yearly. In some Asian countries, Gelidium is also eaten.

© 1999 Sharon C. Komarow. All rights reserved.