Back
Gymnodinium plasticum
Gymnodinium plasticum sp. nov., Wang et al. 2017
Type locality: Plastic Lake, south-central Ontario, Canada
Original description: Wang et al. 2017:
Diagnosis:
Vegetative cells with rounded epicone and hypocone, inhabiting fresh water. Chloroplasts in the periphery forming a network and nucleus elongated longitudinally. There are 9–10, 5 and 8–10 rows of vesicles on the epicone, cingulum and hypocone, respectively. The cingulum is deeply incised with a descending displacement of approximately one cingular width. The sulcus intrudes deeply into the epicone. There is a circular orange stigma in the sulcal area. The apical structure complex (ASC) is horseshoe shaped encircling the apex around 80%. The ASC consists of two pronounced ridges and a deep groove inside. The cyst has a rounded epi- and hypocyst. The cyst is rectangular in lateral view and trapezoidal in polar view. The cyst has a wide cingulum and covered by a thin wall with smooth surface.
Description:
The cells display a characteristic golden colour (Fig. 1), and only a small fraction can form paired chains in optimal conditions (Fig. 2). Many band-like chloroplasts are interconnected to form a network in the periphery of the cell (Figs 3,4). A few round starch rings, presumably stalked pyrenoids are located near the cingulum and a circular orange stigma is present in the sulcal area (Fig. 5).
The nucleus is elongated running nearly vertically, and occupies most of the cell spanning from the epicone to the hypocone (Figs 3,6). The epicone is nearly equal in size to the hypocone. Both the epicone and the hypocone are rounded (Figs 3–5).
Cingulum: deeply incised and has sharp edges, with a descending displacement of approximately one cingular width.
Sulcus: narrow and deeply excavated, especially in the intercingular area due to the projection of right epicone (Fig. 1).
Under SEM, the cells show amphiesmal vesicles which are either pentagonal or hexagonal (Figs 7–10). As many as seven amphiesmal pores (around 0.5 μm in diameter) are present in the epicone and hypocone (Fig. 9). There are around 9–10, 5 and 8–10 rows of vesicles on the epicone, cingulum and hypocone (Fig. 10, 11), respectively. The sulcus intrudes around 60% of the epicone where it connects to the onset of the apical structure complex (ASC) (Figs 7,8). The ASC is horseshoe-shaped and joins the sulcal intrusion, forming the shape of a question mark. The ASC runs anticlockwise, and encircles the apex around 80%. The ASC consists of two pronounced ridges
and a deep groove inside (Figs 10,12). The outer ridge is ornamented with numerous small knobs (Figs 13,14).
The cyst from the field has a rounded epicyst and a rounded to conical hypocyst (Figs 15,16), around 30.8–40.6 μm long, 28.0–35.4 μm wide and 23.8–29.5 μm deep (n = 6).
Cyst wall: thin, and is underlain by a thicker endospore layer.
Shape: cyst is rectangular in lateral view and trapezoidal in apical and antapical view and is excavated on the ventral side (Figs 17,18).
Cyst filled: with brown granules and there is a conspicuous red accumulation body inside and a spherical nucleus (Figs 15–17).
Cingulum: wide, accounting for approximately 40% of the cyst length, and has a smooth surface (Figs 19,20).
Archeopyle: not observed
Dimensions:
25.5–36.1 μm long, and 21.2–27.6 μm wide
epi- and hypocyst: 30.8–40.6 μm long, 28.0–35.4 μm wide and 23.8–29.5 μm deep
The vegetative cells of Gymnodinium plasticum (strain TIO826) are 25.5–36.1 μm long (mean = 30.2 ± 2.5 μm, n = 42) and 21.2–27.6 μm wide (mean = 24.7 ± 2.5 μm, n = 42). Vegetative cells of strain TIO827 are 25.0–34.1 μm long (mean = 29.7 ± 2.4 μm, n = 40) and 19.8–26.4 μm wide (mean = 23.5 ± 2.6 μm, n = 40).
Affinities:
As G. plasticum, Gymnodinium limitatum Skuja and G. mirabile Penard have deep sulcal intrusions, but G. mirabile is much larger (48–68 μm long, 46–62 μm wide) and has a small nucleus located in the hypocone (Penard 1891, plate V, fig. 1). Gymnodinium limitatum has a spherical nucleus and produces spherical cysts (Skuja 1956, Tafel LXI, figs 29–31). Gymnodinium impatiens has no sulcal intrusion and is much smaller and produces ellipsoidal cysts (Skuja 1964, Tafel LXVI, figs 31–34). Gymnodinium uberrimum (Allman) Kofoid & Swezy is of similar size and can form paired cell chains too but its nucleus is rounded and small and it has slight sulcal intrusion (Allmann 1855, pl. 3, figs 9–17). G. plasticum is also similar to G. excavatum Nygaard but the latter has a pronounced eyespot (Nygaard 1945), thus was considered as a synonym of Biecheleria pseudopalustris (J. Schiller) Moestrup, Lindberg & Daugbjerg (Moestrup et al. 2009). G. plasticum differs from G. fuscum
in the shape of hypocone and nucleus, the configuration of chloroplasts and the cyst morphology (Hansen et al. 2000b).
G. plasticum is also similar to some marine athecate species in general shape and sulcal intrusion, including Gymnodinium mundulum Campbell, Gymnodinium aureolum, Gymnodinium polycomma Larsen, Gymnodinium corollarium and G. litoralis A. Reñé (Campbell 1973; Larsen 1994; Hansen et al. 2000a; Sundström et al. 2009; Reñé et al. 2011), but differ in the cell size, elongated nucleus running vertically, and banded chloroplasts forming a network (Table S1).
G. plasticum superficially resembles the cyst of the freshwater species Woloszynskia tylota (H. Mapletoft, M. Montgomery, J. Waters & P. Wells) B.T. Bibby & J.D. Dodge
in the general shape and a wide cingulum, but differs in the lack of a pronounced apical horn and eight additional protuberances in the four corners (Mapletoft et al. 1966). It also somewhat resembles the cyst of the freshwater species G. chiastosporum (Harris) Cridland, but differs in the absence of projections at each edge (Harris 1940). The cyst is also different from that of the freshwater species Glenodinium segriense Dangeard, which has a pronounced apical and antapical horn (Dangeard 1939). The cyst of G. plasticum also somewhat resembles that of the marine species G. trapeziforme Attaran-Fariman & Bolch (Attaran-Fariman et al. 2007), but differs in the absence of microreticulation on the surface and in its transparent color (as opposed to brown).
Type locality: Plastic Lake, south-central Ontario, Canada
Original description: Wang et al. 2017:
Diagnosis:
Vegetative cells with rounded epicone and hypocone, inhabiting fresh water. Chloroplasts in the periphery forming a network and nucleus elongated longitudinally. There are 9–10, 5 and 8–10 rows of vesicles on the epicone, cingulum and hypocone, respectively. The cingulum is deeply incised with a descending displacement of approximately one cingular width. The sulcus intrudes deeply into the epicone. There is a circular orange stigma in the sulcal area. The apical structure complex (ASC) is horseshoe shaped encircling the apex around 80%. The ASC consists of two pronounced ridges and a deep groove inside. The cyst has a rounded epi- and hypocyst. The cyst is rectangular in lateral view and trapezoidal in polar view. The cyst has a wide cingulum and covered by a thin wall with smooth surface.
Description:
The cells display a characteristic golden colour (Fig. 1), and only a small fraction can form paired chains in optimal conditions (Fig. 2). Many band-like chloroplasts are interconnected to form a network in the periphery of the cell (Figs 3,4). A few round starch rings, presumably stalked pyrenoids are located near the cingulum and a circular orange stigma is present in the sulcal area (Fig. 5).
The nucleus is elongated running nearly vertically, and occupies most of the cell spanning from the epicone to the hypocone (Figs 3,6). The epicone is nearly equal in size to the hypocone. Both the epicone and the hypocone are rounded (Figs 3–5).
Cingulum: deeply incised and has sharp edges, with a descending displacement of approximately one cingular width.
Sulcus: narrow and deeply excavated, especially in the intercingular area due to the projection of right epicone (Fig. 1).
Under SEM, the cells show amphiesmal vesicles which are either pentagonal or hexagonal (Figs 7–10). As many as seven amphiesmal pores (around 0.5 μm in diameter) are present in the epicone and hypocone (Fig. 9). There are around 9–10, 5 and 8–10 rows of vesicles on the epicone, cingulum and hypocone (Fig. 10, 11), respectively. The sulcus intrudes around 60% of the epicone where it connects to the onset of the apical structure complex (ASC) (Figs 7,8). The ASC is horseshoe-shaped and joins the sulcal intrusion, forming the shape of a question mark. The ASC runs anticlockwise, and encircles the apex around 80%. The ASC consists of two pronounced ridges
and a deep groove inside (Figs 10,12). The outer ridge is ornamented with numerous small knobs (Figs 13,14).
The cyst from the field has a rounded epicyst and a rounded to conical hypocyst (Figs 15,16), around 30.8–40.6 μm long, 28.0–35.4 μm wide and 23.8–29.5 μm deep (n = 6).
Cyst wall: thin, and is underlain by a thicker endospore layer.
Shape: cyst is rectangular in lateral view and trapezoidal in apical and antapical view and is excavated on the ventral side (Figs 17,18).
Cyst filled: with brown granules and there is a conspicuous red accumulation body inside and a spherical nucleus (Figs 15–17).
Cingulum: wide, accounting for approximately 40% of the cyst length, and has a smooth surface (Figs 19,20).
Archeopyle: not observed
Dimensions:
25.5–36.1 μm long, and 21.2–27.6 μm wide
epi- and hypocyst: 30.8–40.6 μm long, 28.0–35.4 μm wide and 23.8–29.5 μm deep
The vegetative cells of Gymnodinium plasticum (strain TIO826) are 25.5–36.1 μm long (mean = 30.2 ± 2.5 μm, n = 42) and 21.2–27.6 μm wide (mean = 24.7 ± 2.5 μm, n = 42). Vegetative cells of strain TIO827 are 25.0–34.1 μm long (mean = 29.7 ± 2.4 μm, n = 40) and 19.8–26.4 μm wide (mean = 23.5 ± 2.6 μm, n = 40).
Affinities:
As G. plasticum, Gymnodinium limitatum Skuja and G. mirabile Penard have deep sulcal intrusions, but G. mirabile is much larger (48–68 μm long, 46–62 μm wide) and has a small nucleus located in the hypocone (Penard 1891, plate V, fig. 1). Gymnodinium limitatum has a spherical nucleus and produces spherical cysts (Skuja 1956, Tafel LXI, figs 29–31). Gymnodinium impatiens has no sulcal intrusion and is much smaller and produces ellipsoidal cysts (Skuja 1964, Tafel LXVI, figs 31–34). Gymnodinium uberrimum (Allman) Kofoid & Swezy is of similar size and can form paired cell chains too but its nucleus is rounded and small and it has slight sulcal intrusion (Allmann 1855, pl. 3, figs 9–17). G. plasticum is also similar to G. excavatum Nygaard but the latter has a pronounced eyespot (Nygaard 1945), thus was considered as a synonym of Biecheleria pseudopalustris (J. Schiller) Moestrup, Lindberg & Daugbjerg (Moestrup et al. 2009). G. plasticum differs from G. fuscum
in the shape of hypocone and nucleus, the configuration of chloroplasts and the cyst morphology (Hansen et al. 2000b).
G. plasticum is also similar to some marine athecate species in general shape and sulcal intrusion, including Gymnodinium mundulum Campbell, Gymnodinium aureolum, Gymnodinium polycomma Larsen, Gymnodinium corollarium and G. litoralis A. Reñé (Campbell 1973; Larsen 1994; Hansen et al. 2000a; Sundström et al. 2009; Reñé et al. 2011), but differ in the cell size, elongated nucleus running vertically, and banded chloroplasts forming a network (Table S1).
G. plasticum superficially resembles the cyst of the freshwater species Woloszynskia tylota (H. Mapletoft, M. Montgomery, J. Waters & P. Wells) B.T. Bibby & J.D. Dodge
in the general shape and a wide cingulum, but differs in the lack of a pronounced apical horn and eight additional protuberances in the four corners (Mapletoft et al. 1966). It also somewhat resembles the cyst of the freshwater species G. chiastosporum (Harris) Cridland, but differs in the absence of projections at each edge (Harris 1940). The cyst is also different from that of the freshwater species Glenodinium segriense Dangeard, which has a pronounced apical and antapical horn (Dangeard 1939). The cyst of G. plasticum also somewhat resembles that of the marine species G. trapeziforme Attaran-Fariman & Bolch (Attaran-Fariman et al. 2007), but differs in the absence of microreticulation on the surface and in its transparent color (as opposed to brown).