Gymnodiniales

Cells rounded-oblong to pear shaped, dorso-ventrally flattened. Length 24 - 36 microns, width 19 - 26 microns, breadth (lateral) approximately 12 microns, length to width ratio 1.1 - 1.7. Epicone 2 - 4 microns wide, club-shaped, with two lobes, often slightly deflected to the left. Cingulum beginning 0.1 - 0.3 of the cell length from the apex, relatively wide (1 - 3 microns), incompletely encircling the epicone, distal end approximately 2 - 3 microns higher than proximal. Longitudinal groove (0.5 - 2 microns wide) present on the dorsal side, beginning at the apex and descending through the middle of the cell to 0.6 - 0.9 of the cell length from the apex. Hypocone forms a 'collar' around the epicone in dorsal view, this has a division in the middle due to the dorsal longitudinal groove. Sulcus indistinct. Longitudinal flagellum originating 2 - 3 microns below the proximal end of the cingulum. Nucleus in the posterior part of the hypocone, rounded to crescent shaped, may be to the left of the cell, 9 - 11 x 5 - 10 microns. Chloroplasts yellow-brown, 1 - 2 x 1 - 4 microns, often more concentrated in the centre of the cell. A central, pyrenoid-like structure sometimes observed. Indented around the inside of the periphery of the ventral side, 1 - 2 microns from the cell rim. Non-motile cells more circular, with the hypocone encircling the epicone, surrounded by a hyaline layer. Non-motile cells more commonly observed than motile cells.

Amphidinium testudo Herdman 1924. Just dividing cell.

Amphidinium testudo Herdman 1924.

Amphidinium testudo Herdman 1924.

Amphidinium testudo Herdman 1924.

Dorsal view of this sand-dwelling dinoflagellate from Sippiwisset Marsh, Massachusetts, USA. Photo by Shauna Murray and Bob Moore.

Ventral view of this sand-dwelling unarmoured dinoflagellate. From Sippiwissett Marsh, Massachusetts USA. Image by Shauna Murray and Bob Moore.

Amphidinium (am-fee-din-ee-um) boggayum Murray et Patterson 2002. The image shows a non-motile stage (temporary cyst) surrounded by a hyaline layer. The yellow-brown chloroplasts are visible.

Cells oval to oblong from the ventral side, anterior end asymmetrical, apex slightly to the left of the cell. Slightly dorso-ventrally flattened. Length 39 - 58 microns, width 25 - 45 microns, breadth (lateral) approximately 22 microns, length to width ratio 1.1 - 1.5. Proximal end of the cingulum originates 0.5 - 0.6 of the cell length from the apex, rising vertically to 0.2 - 0.3 of the cell length from the apex, then turning left and continuing initially at a slight upward angle on the ventral side. On the dorsal side, cingulum descends in a left turning spiral, ends not displaced. Cingulum initially narrow, widening to approximately 2 - 3 microns, becoming narrow where the ends meet. Sulcus narrow, curving to the right towards the posterior, where it indents the antapex. Apical groove continuing from where the cingulum changes direction, forming an anticlockwise loop around the apex. Longitudinal flagellum arising below the proximal end of the cingulum. Nucleus in the epicone, oval, 10 - 12 microns. One or two small reddish bodies occasionally present, probably food bodies. Numerous yellow-brown chloroplasts, 2 - 3 microns diameter, scattered throughout the cell. Cell surface uneven, covered in bumps approximately 1 microns diameter. Cells very fast swimming, changing to the non-motile form moments after becoming stationary. Non-motile cells round, covered in a hyaline layer, approximately 40 microns diameter, usually cingulum or sulcus not apparent.

Amphidinium boggayum, dividing cyst, observed in marine muds and sandy sediments in the vicinity of Broome, Western Australia in September 2003. This image was taken using differential interference contrast optics.   This work was supported by the Australian Biological Resources Study.

Amphidinium boggayum, from the dorsal side, observed in marine muds and sandy sediments in the vicinity of Broome, Western Australia in September 2003. This image was taken using differential interference contrast optics.   This work was supported by the Australian Biological Resources Study.

Amphidinium boggayum, cyst (non-motile cell) from the ventral side, observed in marine muds and sandy sediments in the vicinity of Broome, Western Australia in September 2003. This image was taken using differential interference contrast optics.   This work was supported by the Australian Biological Resources Study.

Amphidinium boggayum, cyst (non-motile cell) from the ventral side, observed in marine muds and sandy sediments in the vicinity of Broome, Western Australia in September 2003. This image was taken using differential interference contrast optics.   This work was supported by the Australian Biological Resources Study.

Amphidinium boggayum, motile cell, from the ventral side, observed in marine muds and sandy sediments in the vicinity of Broome, Western Australia in September 2003. This image was taken using differential interference contrast optics.   This work was supported by the Australian Biological Resources Study.

Amphidinium (am-fee-din-ee-um) corpulentum Kofoid & Swezy 1921. The image on the left is a mid focus plane through a cell showing the nucleus on the right side of the cell (= the right image side). Red to orange food vacuoles and yellow-brown plastids are visible. The image on the right shows a cell in ventral view (side-reversed). The cingulum is at the anterior end and an apical groove is visible.

Amphidinium (am-fee-din-ee-um) corpulentum Kofoid & Swezy 1921. The image shows a cell in ventral view. The nucleus is on the right cell side (left image side). The cingulum is near the anterior end of the cell. The apical groove is clearly visible. The platids are yello-brown.

Amphidinium corpulentum Kofoid et Swezy 1921.

Amphidinium corpulentum Kofoid et Swezy 1921.

Amphidinium corpulentum Kofoid et Swezy 1921.

Amphidinium corpulentum Kofoid et Swezy 1921.

Amphidinium (am-fee-din-ee-um) latum Lebour 1925. The image shows a cell in ventral view. The red stigma is visible in the sulcal area. The plastids are blue-green and yellow-brown. The epicone is shorter than the hypocone.

Cells rounded square to oblong from the ventral side, dorso-ventrally flattened. Length 16 - 25 microns, width 13 - 26 microns, length to width ratio 0.8 - 1.8. During ingestion, cell shape distorted, becoming broader and rounder. Epicone cone shaped, with a pointed apex. Cingulum wide, approximately 2 microns, completely encircling the cell. Sulcus narrow, a straight line down the middle of the cell, becoming wider at the antapex, where it forms a notch. Short sulcal extension present on the epicone. Apical groove present, continuing from the sulcal extension to the left of the apex and then in an anticlockwise spiral around the apex. Nucleus in the centre or to the left of the hypocone, rounded. Chloroplasts not present. Different coloured food bodies/kleptochloroplasts present, including bright pale green, brown and blue-green cells. Generally very fast swimming. Non-motile cells rarely observed, round, approximately 22 microns diameter, surrounded by a hyaline layer, cingulum often still recognisable.

Amphidinium latum, an unsually large cell with green inclusions, observed in marine muds and sandy sediments in the vicinity of Broome, Western Australia in September 2003.   This work was supported by the Australian Biological Resources Study.

Amphidinium latum observed in marine muds and sandy sediments in the vicinity of Broome, Western Australia in September 2003.   This work was supported by the Australian Biological Resources Study.