Abstract
The life cycle of many dinoflagellates includes at least one nonflagellated benthic stage (cyst). In the literature, the different types of dinoflagellate cysts are mainly defined based on morphological (number and type of layers in the cell wall) and functional (long- or short-term endurance) differences. These characteristics were initially thought to clearly distinguish pellicle (thin-walled) cysts from resting (double-walled) dinoflagellate cysts. The former were considered short-term (temporal) and the latter long-term (resting) cysts. However, during the last two decades further knowledge has highlighted the great intricacy of dinoflagellate life histories, the ecological significance of cyst stages, and the need to clarify the functional and morphological complexities of the different cyst types. Here we review and, when necessary, redefine the concepts of resting and pellicle cysts, examining both their structural and their functional characteristics in the context of the life cycle strategies of several dinoflagellate species.
Highlights
Dinoflagellates are aquatic, highly ecologically diverse, eukaryotic organisms
Microorganisms 2014, 2 dinoflagellate species are associated with harmful algal blooms (HABs) they have been the focus of intense study, including of their complex life cycle
More than 10% of the approximately 2000 known marine dinoflagellate species produce cysts as part of their life cycle (Figure 1). These benthic phases play an important role in the ecology of the species, as part of a planktonic-benthic link in which the cysts remain in the sediment layer during conditions unfavorable for vegetative growth and, from there, reinoculate the water column when favorable conditions are restored
Summary
Dinoflagellates are aquatic, highly ecologically diverse, eukaryotic organisms. As one of the major groups of phytoplankton, they are important contributors to aquatic primary production. With the discovery that planozygotes were able to divide it became apparent that the complexity of dinoflagellate life cycles was greater than originally thought [19,20] Following corroboration of this behavior in several species, the capacity of dinoflagellate sexual phases to restore the vegetative phase, bypassing cyst formation, became well accepted [21,22,23,24]. It is well established that pellicle cysts are the product of asexual or sexual reproduction and that they play a significant role in dinoflagellate bloom dynamics [12,26,32,33] Another type of dinoflagellate cyst that deserves consideration comprises the dividing non-motile stages, or so-called division cysts, of a few dinoflagellate species, i.e., Woloszynskia apiculata (transferred to the genus Tovellia by [34]), Alexandrium taylori, Protoperidinium steidingerae, P. depressum, Kryptoperidinium foliaceum, and Pfisteria piscicida. Because the main traits used in past and present cyst studies to classify cysts are related to characteristics of the cell wall, we use the term “pellicle cysts” to refer to thin-walled cysts, and “resting cysts” for cysts classified as thick-walled, aiming to be generic and thereby to facilitate literature comparisons
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