THE FINE STRUCTURE OF GYMNODINIUM FUSCUM (DINOPHYCEAE)

Abstract

SUMMARYThe large freshwater dinoflagellate Gymnodinium fuscum (Ehrenberg) Stein, which is the type species of the genus, has flagella, chloroplasts, mitochondria, golgi bodies and chromosomes with typically dinophycean fine structure. It has an elaborate pusule with a large central vesicle, into which numerous small vesicles open, and a spiral canal which connects the central vesicle to the exterior. The nuclear envelope is complex with many flattened vesicles built into it which are perforated only towards the nucleus. The theca consists of three membranes, enclosing beneath the outer two a thin plate-like structure homologous with the plates of armoured dinoflagellates. Beneath the third membrane numerous microtubules are found. G. fuscum does not possess pyrenoids or trichocysts.

An electron microscope study of the excystment and early development of the dinoflagellateCeratium hirundinella

“…Dodge & Crawford (1970b) described the extensive tubular complex found in C. hirundinella as having similarities with the pusule, or osmoregulatory organelle, found in Gymnodinium fuscum (Ehrenb.) Stein (Dodge & Crawford, 1969). Since the tube found here, opening to the flagellar canal, has a similar membrane appearance to that of the tubular complex it is likely that it functions as a discharge tube for a simple tubular pusule system as proposed by Dodge (1972).…”

The encystment of a freshwater dinoflagellate: A light and electron-microscopical study

“…Food storage is apparent in the starch grains found in the hypocone and in the lipid droplets throughout the cytoplasm. No trichocysts are found in this organism, a feature which separates it from W. coronata and W. tenuissima, but in which it resembles some members of the related genus Gymnodinium Stein (Dodge & Crawford, 1969;Mignot, 1970).…”

“…When plates could be seen these were hexagonal in shape and numerous. The electron microscope has made it possible to see directly whether plates exist in the membraneous vesicles of the theca (Dodge & Crawford, 1970a) and it has confirmed the positions of Gymnodinium fuscum (Ehrenberg) Stein (Dodge & Crawford, 1969) and the Gymnodinium studied by Mignot (1970) both of which have only rudimentary 'plates', in contrast to the two freshwater species of Woloszynskia studied (Crawford & Dodge, in press; Crawford, Dodge & Happey, 1971) which have well-developed plates.…”

Gymnodinium litoralis sp. nov. (Dinophyceae), a newly identified bloom-forming dinoflagellate from the NW Mediterranean Sea

“…A horseshoe-shaped apical groove is, however, also seen in Polykrikos species, such as P. hartmanii (=Pheopolykrikos hartmanii), P. kofoidii, and P. schwartzii (Nagai et al, 2002;Takayama, 1985), the two species belonging to the Lepidodinium genus, L. viride and L. chlorophorum (Elbrä chter and Schnepf, 1996;Watanabe and Suda, 1990), and some warnowiids, such as Nematodinium and Proterythropsis (Hoppenrath et al, 2009). The presence of nuclear chambers has been observed in some Gymnodinium species, such as G. fuscum (Dodge and Crawford, 1969), G. aureolum (Hansen, 2001), G. nolleri (Ellegaard and Moestrup, 1999), and G. corollarium (Sundströ m et al, 2009), as well as in other genera, including Lepidodinium (Hansen et al, 2007), Barrufeta (Sampedro et al, 2011), andPolykrikos (Hoppenrath andLeander, 2007). In this study, we confirmed two key characters of the genus in G. litoralis, the shape of the apical groove and cingulum displacement, while others, including nuclear envelope chambers or a nuclear fibrous connective, are apparently absent.…”