H
HALIMEDA
Edward Drew
Townsville, Queensland, Australia
Synonyms
Siphonales (in older literature); Siphonous algae
Definition
Halimeda is a genus of warm temperate to tropical
macroalgae classified into
Phylum: Chlorophyta
Class: Bryopsidophyceae
Order: Bryopsidales
Family: Halimedaceae
Genus: Halimeda
Phytochemistry
Photosynthetic pigments
Halimeda chloroplasts contain the characteristic photosynthetic pigments of the Chlorophyta, plus siphonoxanthin
and siphonein, which are specific to the Bryopsidales.
Cell wall
Halimeda and most other Bryopsidales have cell walls
composed of a xylose-based b-1–3 linked xylan, not the
glucose-based cellulose found in all other Chlorophyta.
General
Author’s Halimeda Web site:
http://members.iinet.net.au/$edrew1/halimeda/halimeda.
htm
Appearance
Halimeda thalli are composed of branching chains of calcified green segments joined together by flexible,
uncalcified nodes. The thalli may be erect, pendant, or
sprawling. They may grow up to 25 cm high or cover over
1 m if sprawling. They are anchored by holdfasts, which
may be
(i) A small basal mass about a cm long, consisting of
matted rhizoidal filaments adhering to rocks.
(ii) Or a large, dense bulbous mass, 1–13 cm long, buried in the sediment. It consists of fine rhizoids with
adhering sediment particles and can be up to 40%
of the plant’s total weight.
(iii) Or several diffuse, inconspicuous patches of rhizoids
arising at intervals from segments or nodes of the
algae sprawling on rocks or unstable surfaces.
Segment size and shape vary considerably between species. They may be flat, keeled, or even cylindrical in some.
Their outline varies from ovate to cuneate and may be distinctly lobed. The width varies from 2 to 55 mm.
Taxonomy
Halimeda tuna, from the Mediterranean Sea, is the holotype of the genus. It was first described, but named
Sertolara, by Imperato (1599). During the next century,
it was given several different generic names and was considered to be a coralline animal. In 1812, it was finally recognized as a plant and given its currently recognized
binomial name, Halimeda Tuna (Ellis and Solander,
1786; Lamouroux, 1816). At that time, exploration of
tropical regions had just begun, and the number of
described Halimeda species reached 26 by 1887, most
species being described solely on the basis of their segment morphology.
Currently, 44 species are recognized, distinguished
using the morphological and anatomical characters
David Hopley (ed.), Encyclopedia of Modern Coral Reefs, DOI 10.1007/978-90-481-2639-2,
# Springer Science+Business Media B.V. 2011
HALIMEDA
Edward Drew
Townsville, Queensland, Australia
Synonyms
Siphonales (in older literature); Siphonous algae
Definition
Halimeda is a genus of warm temperate to tropical
macroalgae classified into
Phylum: Chlorophyta
Class: Bryopsidophyceae
Order: Bryopsidales
Family: Halimedaceae
Genus: Halimeda
Phytochemistry
Photosynthetic pigments
Halimeda chloroplasts contain the characteristic photosynthetic pigments of the Chlorophyta, plus siphonoxanthin
and siphonein, which are specific to the Bryopsidales.
Cell wall
Halimeda and most other Bryopsidales have cell walls
composed of a xylose-based b-1–3 linked xylan, not the
glucose-based cellulose found in all other Chlorophyta.
General
Author’s Halimeda Web site:
http://members.iinet.net.au/$edrew1/halimeda/halimeda.
htm
Appearance
Halimeda thalli are composed of branching chains of calcified green segments joined together by flexible,
uncalcified nodes. The thalli may be erect, pendant, or
sprawling. They may grow up to 25 cm high or cover over
1 m if sprawling. They are anchored by holdfasts, which
may be
(i) A small basal mass about a cm long, consisting of
matted rhizoidal filaments adhering to rocks.
(ii) Or a large, dense bulbous mass, 1–13 cm long, buried in the sediment. It consists of fine rhizoids with
adhering sediment particles and can be up to 40%
of the plant’s total weight.
(iii) Or several diffuse, inconspicuous patches of rhizoids
arising at intervals from segments or nodes of the
algae sprawling on rocks or unstable surfaces.
Segment size and shape vary considerably between species. They may be flat, keeled, or even cylindrical in some.
Their outline varies from ovate to cuneate and may be distinctly lobed. The width varies from 2 to 55 mm.
Taxonomy
Halimeda tuna, from the Mediterranean Sea, is the holotype of the genus. It was first described, but named
Sertolara, by Imperato (1599). During the next century,
it was given several different generic names and was considered to be a coralline animal. In 1812, it was finally recognized as a plant and given its currently recognized
binomial name, Halimeda Tuna (Ellis and Solander,
1786; Lamouroux, 1816). At that time, exploration of
tropical regions had just begun, and the number of
described Halimeda species reached 26 by 1887, most
species being described solely on the basis of their segment morphology.
Currently, 44 species are recognized, distinguished
using the morphological and anatomical characters
David Hopley (ed.), Encyclopedia of Modern Coral Reefs, DOI 10.1007/978-90-481-2639-2,
# Springer Science+Business Media B.V. 2011