caulerpa by dr. s.n. suresh

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CAULERPA

{General characters and reproductive structure}

By

Dr. S.N. Suresh


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Caulerpa

Distribution: It includes 60 speices all of these are exclusively marine.

Many sp. are found along the Indian coast. A larger number of

marine species are lithophytes occurring attached to rocks, that after

cover extensive tracts of the sea floor. Some species are found

growing at a depth of 75 to 80 meters. A few grow epiphytically on

the roots of mangrooves. Svedelius and Boergesen (1907) classified

the various species ofCaulerpa into the following categories;

Mud Collecting species: Species which grow where there is much

mud and with a rhizome but often grows oblique are almost vertical

enabling them to reach the surface even when covered occasionally bymud (C.verticillata).

Sand and Mud bottom Species: This group grows rooted in the mud

or sand at the bottom the rhizome usually has a pointed tip with

which it bores its way through the soft substratum (C.cupresoides).

Rock and coral reef species: Species with diverse forms principally

attached to the rocks or corals growing in exposed or sheltered

localities. (C.racemosa).

Structure: The thallus of caulerpa is one celled (within septum) and

reaches a large size up to a meter in length. In size and external form

its simulates a angiospermic plant with a root stock. Some species

attains a size which may be as much as 30 cm in height and meter in

length.The thallus has a definite external form. It is differentiated

into a cylindrical rhizome like creeping portion. From the upper

surface of the rhizome arise a number of erect branches which

resembles foliage shoot and thus are often called assimilatory shoot

(or) leaves. From the lower side of the rhizome arise the numerous

branched thread like rhizoides.


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The rhizome like creeping portion and the attaching rhizoids

exhibit no variations in form. In many species the erect branches

have a central, cylindrical axis. The axis bears lateral outgrowths

which are known as the assimilators. C. vaerticilata the assimilators

are cylindrical and arranged in verticillate manner. The assimilators

ofC. selago are long, subulate and imbricate. In some species like C.prolifrea the upright branches are flattened, shortly stalked leaf-like

structures. Genetically the thallus is a diploid structure.

Thallus Structure: Internally, the plant body is characterized by the

complete absence of septation and is composed of closely apposed and

interwined coenocytic (multinucleate) threads traversed by

longitudinal and transverse skeletal strands called trabeculae. The

trabeculae are a strongly developed in the rhizome portion and

completely absent or poorly developed in the rhizoids.

The peripheral cytoplasm encloses numerous nuclei and

disciform chloroplasts devoid of pyrenoids. The wall is made up of

callose, pectin, pectic acids and a polymer of pentose sugar. There is

no cellulose. The wall is thick, living layer of cytoplsam which

surround a large, central vacuole. The chloroplasts are devoid of

pyrenoids.

Reproduction: Vegetative and sexual methods

Vegetative: It reproduces by the method of fragmentation. It

takesplace by the growth and decay of new and older parts, resulting

in the formation of new plants.

Sexual Reproduction:Majority of the species are dioecious. Iyengar (1940) reported one

monoecious sp. from India. Sexual reproduction is generally

anisogamous. The gamets produced being of two different sizes, the

smaller microgametes and the larger macrogametes. Thallus being

diploid meiosis occurs at the time of gamete formation. So, the gemets


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are haploid. Both the gametes are bifillagellate and pear shaped, with

a single curved chloroplast without a pyrenoid and a prominent

elongate eye-spot. They are developed on the assimilators or rarely on

the rhizome (C.prolifera) in special gametangial areas separated from

the rest of the protoplast by a membrane. The gamets are liberated

shortly after a mass of mucilage through the apices of elongatedpaplillae, the extrusion paplillae.

Soon after the liberation of gametes, the fertile parts of the

thallus die and decay. The gamets fuse in pairs in the open sea to

produce zygote which retains all the four filagella for a time. The

zygote soon loses its filagella, becomes spherical and secretes a wall

around it. After the zygote germinates and gives rise to the thallus.


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caulerpa by dr. s.n. suresh

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