Volvox

This article is about Volvox, a colony of microorganisms. For the rock music band with the same name, see Volvox (band)

Volvox is one of the best-known chlorophytes and is the most developed in a series of genera that form spherical colonies. Each Volvox is composed of numerous flagellate cells similar to Chlamydomonas, on the order of 1000-3000 in total, interconnected and arranged in a glycoprotein-filled sphere (coenobium). The cells swim in a coordinated fashion, with a distinct anterior and posterior - or since Volvox resembles a little planet, a 'north and south' pole. The cells have eyespots, more developed near the anterior, which enables the colony to swim towards light.

An asexual colony includes both somatic, or vegetative, cells, which do not reproduce, and gonidia near the posterior, which produces new colonies through repeated division. These daughter colonies are initially held within the parent and have their flagella directed inwards. Later, the parent disintegrates and the daughters invert. In sexual reproduction two types of gametes are produced. Volvox species can be monoecious or dioecious. (Male) colonies release numerous microgametes, or sperm, while in (female) colonies single cells enlarge to become oogametes, or eggs.

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Habitats

Volvox is found in ponds and ditches, and even in shallow puddles. The most favorable place to look for it is in the deeper ponds, lagoons, and ditches which receive an abundance of rain water. It has been said that where you find Lemna, you are likely to find Volvox; and it is true that such water is favorable, but the shading is unfavorable. Look where you find Sphagnum, Vaucheria, Alisma, Equisetum fluviatile, Utricularia, Typha, and Charales, Dr. Nieuwland reports that Pandorina, Eudorina and Gonium are commonly found in summer as constituents of the green scum on wallows in fields where pigs are kept. The flagellate Euglena is often associated with these forms. If you have a culture in the laboratory, do not throw it out when the culture disappears, because new coenobia are likely to develop from the oospores. The individual alga are connected by thin strands of cytoplasm, called protoplasmates.

Laboratory protocols

A colony of Volvox can be cultured using a mild plant fertilizer in distilled water. Use approximately 0.5 g of 10-5-5 plant fertilizer to 1000 ml of distilled water. Both the container and water should be sterile, boil mixture then let cool to room temp, prior to infusion. Place the container by a windowsill where filtered, not direct sunlight, will reach for at least a few hours per day. You will notice the colony will tend to settle to the bottom of your container at night then rise to the surface seeking sunlight.

Material of Volvox and other Volvocales may be fixed in the corrosive sublimate-acetic mixture^[1] used hot (85° C). If material is to be stained and mounted whole, use the aqueous mixture, otherwise if it is to be imbedded and cut, use the alcoholic. For mounting whole, stain in iron-alum haematoxylin, or in Magdala red and aniline blue, following the Venetian turpentine method. A few bits of broken cover glass, placed among the colonies, will prevent crushing.

Notes

1. ^ Corrosive sublimate-acetic is a mixture of mercuric chloride (2 g), glacial acetic acid (2 ml) and H₂O (100 ml).

References

• Chamberlain, Charles Joseph. Methods in Plant Histology.