Dinoflagellates

In this article, we will discuss Dinoflagellates. So, let’s get started.

Dinoflagellates are a biologically complex group of protists that comprise planktonic, meroplanktonic, and benthic species. They have different modes of nutrition making it difficult to attribute the group as a
whole to animals or plants. Some species produce toxins that impact human health through consumption of contaminated seafood or water or aerosol exposure (Hackett et al., 2004). Toxic algae blooms are
increasingly documented over the past decades and may have a considerable economic impact. Extensive blooms of dinoflagellates may cause a coloration of water known as red tide. Some species are an important source of bioluminescence (Hackett et al., 2004). Since it has been finally accepted more than 50 years ago that the fossil hystrichospheres in Mesozoic and
Cenozoic sediments are cysts of dinoflagellates (e.g., Dale, 1983), dinoflagellate cysts have become important in stratigraphy and understanding past environments.

General Characteristics

Dinoflagellates (c. 2 to 2,000 mm) are primarily unicellular eukaryotes but some species are colonial, and chain formation is common (Taylor et al., 2008). Organisms are assigned to the division Dinoflagellata
(kingdom Alveolata) based on possession of one or more of a suite of characters including an amphiesma, two dissimilar flagella, and a unique type of nucleus (Taylor, 1987). The amphiesma is the complex outer region of the cell wall, usually containing a single layer of flattened vesicles. These amphiesmal vesicles
may contain thecal plates usually composed of cellulose (thecate or armored forms). Six basic types of tabulation, i.e., arrangement of amphiesmal vesicles, are known (Fensome et al., 1993). Dinoflagellates without thecal plates are called athecate, naked, or unarmored. A distinctive flagellar apparatus consisting of a coiled transverse flagellum within a cingular groove and a posterior flagellum within a sulcal groove enables a spiral motion and to move freely in the water column (Taylor, 1987). Swimming speeds range from centimeters to a few meters per hour. Vertical migration is a result of endogenous rhythms. This motility permits to optimize position in the euphotic zone to a limited extent to take full advantage of light and nutrients and avoids sinking under very stable water conditions. The unique type of nucleus, the dinokaryon, is characterized by chromosomes that remain condensed between cell divisions, and a lack of histones. Dinoflagellates may have special vacuole-like structures of unknown function called pusules (usually two per cell). The accessory pigment peridinin that enables energy transfer may be present in photosynthetic cells.