Gymnodinium Stein (ref. ID; 1618) or Stein em. Kofoid & Swezy (ref. ID; 3517)

[ref. ID; 1618]
Pellicle delicate; subcircular; bilaterally symmetrical; numerous discoid chromatophores varicolored (yellow to deep brown, green, or blue) or sometimes absent; stigma present in few; many with mucilaginous envelope; salt, brackish, or fresh water. (ref. ID; 1618)

[ref. ID; 3490]
The flagellate cell is generally ovoid and is provided with the girdle near the middle part and the sulcus which does not extend along the entire length on the ventral side. The transverse flagellum waves in the girdle and the longitudinal one comes out at the central portion of the sulcus and stretched posteriorly. The nucleus is usually more or less large and situated in the center of the cell. The chromatophores are usually numerous and discoidal or ovoidal, while rarely absent. (ref. ID; 3490)

Gymnodinium aeruginosum Stein (ref. ID; 1618)
Description; Green chromatophores; ponds and lakes. (ref. ID; 1618)
Measurements; 20-32 by 13-25 um. (ref. ID; 1618)
Gymnodinium agile Kofoid & Swezy (ref. ID; 1618)
Description; Along sandy beaches. (ref. ID; 1618)
Measurements; About 28 um long. (ref. ID; 1618)
Gymnodinium arcuatum Kofoid (ref. ID; 3494)
Description; The species with an arcuated posterior end is oblong in lateral view, and yellowish orange in colour of the body due to absence of chromatophores and presence of oil globules. (ref. ID; 3494)
Measurements; Length 50 um; breadth 35 um. (ref. ID; 3494)
Gymnodinium aureolum (Hulburt) Hansen (ref. ID; 7121)
Description; Free-living. GenBank accession number AY999082. (ref. ID; 7121)
Geographic origin; Current waters off Namibia. (ref. ID; 7121)
Gymnodinium baccatum Balech, 1965 (ref. ID; 3544)
Description; The small elongate naked dinoflagellate consists of a smaller conical epicone and a larger ovate hypocone. The girdle hungs down on the ventral face and the sulcus stretches to the posterior end. A number of ovoid chromatophores are scattered in the entire body, in which two minute pulsing vacuoles of a pale pink color are typically seen. The nucleus is rather large near the center of the body. (ref. ID; 3544)
Comments; The present form is more or less different in details from one reported by Balech (1965) from the Weddell Sea, but they are closely allied to each other in general contour. Such slight differences are probably caused by fixing samples. Therefore, the form from the sea near Syowa Station may be included in G. baccatum described in originally by Balech from the Weddell Sea. (ref. ID; 3544)
Measurements; Length 23-30; breadth 14-20 um. (ref. ID; 3544)
Gymnodinium baicalense Antipova (ref. ID; 7121)
Description; Free-living. GenBank accession number FJ024297. (ref. ID; 7121)
Geographic origin; Lake Baikal, Russia. (ref. ID; 7121)
Gymnodinium catenatum Graham, 1943 (ref. ID; 6716) reported year? (ref. ID; 3494, 7121)
Description; The cell is oblong in swimming and round in resting. The apical end anteriorly is produced and the distal end is rounded. The girdle is wide and transversal in the middle of the body. Chromatophores are numerous and ovate. A number of individuals usually make a long chain-like colony. (ref. ID; 3494)
Free-living. GenBank accession number AF022193. (ref. ID; 7121)
Remarks; This species produces paralytic shellfish toxins (PSP). The toxic dinoflagellate G. catenatum was first described occurring in the Gulf of California in 1943 (Graham, 1943). (ref. ID; 6716)
Geographic origin; Coastal waters of Africa. (ref. ID; 7121)
Measurements; Length 47-52 um, breadth 23-25 um in swimming; length 30-35 um in resting. (ref. ID; 3494)
Significant differences were found between cell length (CL), cell width (CW) and CW/CL ratios in laboratory cultures in the late exponential growth phase. Average CL varied between 41 and 53.69 um, with a range between 26.94 and 69.99 um; average CW varied between 33.75 and 40.68 um, with a range between 25.04 and 54.73 um; the average CW/CL varied between 0.76 and 0.97 um, with a range between 0.49 and 1.27 um. Cingulum thickness was between 3 and 4.11 um, with a range between 1.97 and 6.74 um. Cell size varied with the length of the chain and position in the chain. (ref. ID; 6716)
Gymnodinium cinctum Kofoid & Swezy (ref. ID; 3544)
Description; The body consists of a conical epicone and a hemispherical hypocone. The girdle is transversal at the middle of the body and the sulcus does not stretch to the ends. Numerous small chromatophores are scattered in the entire body. The ovoid nucleus usually exists in the posterior half of the body. (ref. ID; 3544)
Measurements; Length 27-48; breadth 22-25 um. Length 32 um, breadth 25 um in a cyst. (ref. ID; 3544)
Gymnodinium flavum Kofoid & Swezy (ref. ID; 3544)
Description; The rounded body has a wide, nearly straight girdle transversing at the center and a short sulcus. The surface layer of the body is more or less hardened to take a constant form. Chromatophores are many and ovoidal. The nucleus is ellipsoid and typically near the center. (ref. ID; 3544)
Measurements; Length 30-40; breadth 25-40 um. (ref. ID; 3544)
Gymnodinium frigidum Balech (ref. ID; 3544)
Description; The body is broadly conical with a roundly pointing apical end and a slightly concave basal flat. The girdle is wide and descends at the center of the ventral face, and the sulcus is also wide and extends to the sunken posterior end. Numerous small chromatophores are ovoid and distributed radially. The large ellipsoidal nucleus is typically at the center. (ref. ID; 3544)
Measurements; Length 45-47; breadth 37-42 um. (ref. ID; 3544)
Gymnodinium fuscum (Ehrenberg) Stein (ref. ID; 7121) reported author and year? (ref. ID; 6716)
Description; Free-living. GenBank accession number AF022194. (ref. ID; 7121)
Geographic origin; Freshwater lake, Europe. (ref. ID; 7121)
Gymnodinium hiroshimaensis Hada, 3497 (ref. ID; 3497 original paper)
Comments; The new form is allied to Gymnodinium paulseni Schiller in presence of chromatophores and general contour, but is different from the latter in having a lager epicone with a more pointing anterior end. (ref. ID; 3497)
Gymnodinium impatiens Skuja (ref. ID; 7121)
Description; GenBank accession number EF058239. (ref. ID; 7121)
Geographic origin; Freshwater reservoir, Brandenburg; Neuglobsow, Germany. (ref. ID; 7121)
Gymnodinium lunulum Schutt (ref. ID; 3494)
Description; The species well-known owing to the complicated life history is one of the common plankton organisms in seas surrounding Japan. (ref. ID; 3494)
Measurements; Length 95-100 um, breadth 18-20 in crescent cysts. (ref. ID; 3494)
Gymnodinium marinum Kent (ref. ID; 3497)
Description; The body is tumbler-shaped, consisting of the small epicone in which the sulcus is not stretched, and of the broader hypocone, and contains no chromatophore, many small globules and a large ovoidal nucleus. (ref. ID; 3497)
Measurements; Length 10 um; breadth 7 um. (ref. ID; 3497)
Gymnodinium mikimotoi Miyake & Kominami, 1935 (ref. ID; 7109) reported year? (ref. ID; 3494)
Syn; Gymnodinium nagasakiense Takayama & Adachi, 1984 (ref. ID; 7109)
Description; The compressed species is rounded with a lower epicone, comprising with a hypocone. Oblong chromatophores are many and yellowish green. (ref. ID; 3494)
Comments; This species is closely similar G. simplex Lohmann in form and size, but it is easily distinguishable from the latter in having many smaller chromatophores instead of few larger ones in the latter. (ref. ID; 3494)
Measurements; Length 15-25 um; breadth 15-24 um. (ref. ID; 3494)
Gymnodinium minor Lebour (ref. ID; 3497, 3544)
Description; Having no chromatophore, the minute rounded species is colourless. The girdle is transversal slightly below the middle, and the sulcus is not extended into the epicone. The nucleus is spherical and situated at the center of the body. (ref. ID; 3497)
The colorless form without chromatophores is small and elliptical in side view. The girdle is transverse at the middle of the body, and the sulcus slightly extends upwards, while fairly downwards from the center. The nucleus is comparatively large and ovoid at the center of the body. The pulsing vacuoles are usually seen due to absence of chromatophore. The protoplasm is more or less granular. (ref. ID; 3544)
Measurements; Specimens examined from Hiroshima Bay are fairly smaller in comparison with European ones, the former being 10 um in length, while the latter 28 um. (ref. ID; 3497)
Length 18; breadth 16 um. (ref. ID; 3544)
Gymnodinium nelsoni (ref. ID; 3731, 4102)
Description; Marine dinoflagellate. (ref. ID; 4102)
Gymnodinium ostenfeldi Schiller (ref. ID; 3494)
Description; The elongate form consisting of a small epicone and a longer hypocone, is somewhat compressed and twisted in swimming. Chromatophores are many and greenish brown. The pulsing vacuole connecting two flagellar pores is reddish as seen like an eye-spot. (ref. ID; 3494)
Measurements; Length 15-25 um; breadth 10-18 um. (ref. ID; 3494)
Gymnodinium ovulum Kofoid & Swezy (ref. ID; 3494)
Description; The round species without chromatophores generally has a large oil drop and a long longitudinal flagellum. (ref. ID; 3494)
Measurements; Length 15-20 um; breadth 12-15 um. (ref. ID; 3494)
Gymnodinium palustre Schilling (ref. ID; 1618, 3490)
Description; In fresh water. (ref. ID; 1618)
The oblong species of which the epicone is somewhat longer than the hypocone. (ref. ID; 3490)
Measurements; 45 by 38 um. (ref. ID; 1618)
Gymnodinium rotundatum Klebs (ref. ID; 1618)
Description; In fresh water. (ref. ID; 1618)
Measurements; 32-35 by 22-25 um. (ref. ID; 1618)
Gymnodinium simplex Lohmann (ref. ID; 3494) or (Lohmann) Peters, 1930 (ref. ID; 4151)
Description; The small unarmored dinoflagellate is rounded and more or less compressed laterally. Chromatophores are comparatively large and several in number. (ref. ID; 3494)
Measurements; Length 15-20 um. (ref. ID; 3494)
Gymnodinium soyai Hada, 1970 (ref. ID; 3544 original paper)
Description; The small body is somewhat compressed dorso-ventrally, and consists of a conical epicone and a fairly larger hypocone rounded at the posterior end. The girdle is curved on the ventral face, and the sulcus does not typically extend to the epicone, while the latter stretches to the antapical end. Chromatophores are many and ovoid, and the nucleolus is usually central. Two pulsing vacuoles are scarcely observed. The cysts are generally ellipsoidal and covered with thick gelationus layers. (ref. ID; 3544)
Comments; The new species is easily distinguishable from the allied form, G. cinctum Kofoid & Swezy, in smaller dimension and in fewer number and larger size of chromatophores. It is a common species in the region of the antarctic sea neighboring Syowa Station, being found in many plankton materials of surface water. (ref. ID; 3544)
Measurements; Length 13-28; breadth 10-23; length of cysts 25-30; breadth of the same 17-23 um. (ref. ID; 3544)
Gymnodinium splendens Lebour, 1925 (ref. ID; 3731) reported year? (ref. ID; 3494)
Description; The unarmored form is fairly compressed and composed of a conical epicone anterior end and a hypocone with an arcute depression at the posterior end. The deep girdle is located transversally at the middle of the body. Many lines made of minute rod-shaped chromatophores run radially. The large ovoidal nucleus is at the center of the cell. (ref. ID; 3494)
Measurements; Length 75-77 um; breadth 50-55 um; thickness 25-30 um. (ref. ID; 3494)
Gymnodinium tenuissimum Lauterborn (ref. ID; 3490)
Description; The ovate species as long as 48-60 um and as broad as 40-50 um, is remarkably compressed dorso-ventrally as thick as about 5 um. Living individuals usually bend ventrally the lateral ends of the flattened cell. The chromatophores are numerous, discoidal and dark brown. (ref. ID; 3490)
Gymnodinium veris Lindemann (ref. ID; 3490)
Description; The small species, 20-37 um in length and 14-30 um in breadth, is ovate in front view and is slightly compressed dorso-ventrally. The chromatophores are numerous and yellowish brown in colour. (ref. ID; 3490)
[Cyst]: When temperature of water become higher, encysted ones appear. Cysts generally change from the larger diamond-shaped form to the smaller confetto-shaped one. (ref. ID; 3490)
Comments; The specimens having two longitudinal flagella were found by Ohno (1911) from the pond in the University of Tokyo in winter and reported as the new species named Gymnodinium biciliatum. Being closely allied in form and size excepting in number of flagella and also almost equal in season of occurrence, they seem to be included in this species. (ref. ID; 3490)