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.
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