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Literature Review of the Microalga Prymnesium parvum and its Associated Toxicity

Sean Watson, Texas Parks and Wildlife Department, August 2001


Background Biology and Diagnostic Features

Prymnesium parvum is a microalga in the class Prymnesiophyceae, order Prymnesiales and family Prymnesiaceae, and is a common member of the marine phytoplankton (Bold and Wynne 1985, Larsen 1999, Lee 1980). It is a uninucleate, unicellular flagellate with an ellipsoid or narrowly oval cell shape (Lee 1980, Prescott 1968). Green, Hibberd and Pienaar (1982) reported that the cells range from 8-11 micrometers long and 4-6 micrometers wide. The authors also noted that the cells are sometimes slightly compressed with the posterior end rounded or tapered and the anterior end obliquely truncate. An individual P. parvum cell has two equal flagella and a well-developed haptonema (Lee 1980). The flagella are used for motility and the haptonema may be involved in attachment and/or phagotrophy (McLaughlin 1958, Prescott 1968). Green, Hibberd and Pienaar (1982) found that the flagella range from 12-15 micrometers long and the flexible, non-coiling haptonema ranges from 3-5 micrometers long. These authors noticed that each cell has body scales of two types found in two layers with scales of the outer layer having narrow inflexed rims and those of the inner layer having wide, strongly inflexed rims. The scales are an important diagnostic feature invaluable in distinguishing P. parvum from closely related algal species, and the flagella-to-cell length ratio and the haptonema-to-cell length ratio are also important diagnostic features that aid in identifying this organism, especially when collected in mixed algal blooms (Chang and Ryan 1985).

In P. parvum, the nucleus is located centrally between two chloroplasts, one being lateral and the other parietal, that are usually yellow-green to olive in color (Green et al. 1982). Lee (1980) noted that a two-membrane chloroplast endoplasmic reticulum is present with the outer membrane of the chloroplast ER being continuous with the outer membrane of the nuclear envelope. The author also found a large Golgi apparatus located at the anterior end of the cell. This single polarized Golgi apparatus is always located between the bases of the two flagella and the nucleus (Bold and Wynne 1985). A contractile vacuole is also sometimes found at the anterior end of P. parvum cells (Lee
1980). The reserve metabolite chrysolaminarin is found in posterior vesicles (Green et al. 1982, Lee 1980). Peripheral muciferous bodies and lipoidal globules may also be present and the cysts formed by P. parvum have been reported as having an oval shape (Green et al. 1982).

Bold and Wynne (1985) described the microalga P. parvum as photosynthetic with possible heterotrophic growth (phagotrophy) when cells sink below the euphotic zone. They also found that it is a euryhaline and eurythermal organism tolerating a broad range of salinities and temperatures.

Global Occurrence of Fish Kills

Aditional Information:

Would you like to know more?
The Biology of Golden Alga summarizes what we know about the alga and its toxins.

Where does golden alga fit compared to other single-celled organisms?
The Golden Alga Family Tree gives examples of and information about golden alga and other protists.

What does golden alga look like?
TPWD Golden Alga Images has photos of fish kills, golden algal cells, and short videos of live golden alga. These images may be used for noncommercial/educational purposes as long as TPWD is given credit and other site policies are followed.

Golden Alga Information Card: TPWD has collaborated with the Texas Commission on Environmental Quality and other entities to produce a golden alga information card. Download a PDF from the TCEQ website or request a free hard copy from TPWD at

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