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Alexandrium monilatum is a thecate, chain-forming dinoflagellate (Figure 1 and video). Individual cells are wider than long, thus with anterior-posterior flattening. Plates that make up the theca are rather delicate and not easily differentiated (Figure 2). The Kofoidean plate formula for Alexandrium (Hallegraeff 2003) is Po, 4’, 0a, 6’’, 6c, 9-11s, 5’’’,1p, 1’’’’. Balech (1995) indicated that A. monilatum conforms to this general formula, and has 10s. The 1’ plate does not contact the Po of the apical pore complex (Figure 3), and a small ventral pore is usually present at the junction of 1’, 2’ and 4’ (Figure 3). This ventral pore may be a characteristic confined to Florida specimens.
Cells are joined in chains by exudates from the apical attachment pore (Figure 3, red arrow) and the antapical attachment pore, centrally located and surrounded by several raised radial markings, in the large and concave posterior sulcal plate (Figure 4, red arrow). This attachment is not firm and, though 16-cell chains are quite common, 8- and 4-cell chains are also frequent. In quiet waters, 32-cell chains can be found. In the original description, Howell (1953) found up to 40 individuals per colony. Despite this, when grown in stationary culture, there is a tendency for the colonies to degenerate into unicells.
Alexandrium monilatum is photosynthetic and filled with large number of small brown or yellow-brown chloroplasts that radiate from the centrally located nucleus, which is somewhat lunate. At least some strains are bioluminescent (Latz et al. 2008).
GenBank has limited information on the molecular genetics of this species http://www.ncbi.nlm.nih.gov/.
HABITAT AND DISTRIBUTION
Habitat & Regional Occurence
Alexandrium monilatum is a coastal and estuarine planktonic species of warm temperate and tropical environments, and is known from both eastern Pacific and western Atlantic Oceans. It is widespread in the Gulf of Mexico and Caribbean Sea, and has been recorded from the Chesapeake Bay.
Indian River Lagoon Distribution & Abundance
In the IRL, A. monilatum is most often found in summer and early fall, particularly south of Fort Pierce, rarely reaching concentrations of more than a few thousand cells per liter. However, Norris (1983) reported a bloom of 106 cells per liter at Melbourne Beach. It has been rare in the Banana River and Mosquito Lagoon.
Balech, E. 1995. The genus Alexandrium Halim (Dinoflagellata). Sherkin Island Marine Station, Cork, Ireland. 151pp.
Gates, JA & WB Wilson. 1960. The toxicity of Gonyaulax monilata Howell to Mugil cephalus. Limnol. Oceanogr. 5: 171-174.
Halim, Y. 1967. Dinoflagellates of the South East Caribbean Sea (East Venezuela). Internationale Revue des gesamten Hidrobiologie 52: 701-755.
Hallegraeff, GM. 2003. Taxonomic Principles. In: Hallegraeff, GM, Anderson, DM & AD Cembella (Eds.). 383-432. Manual on Harmful Marine Microalgae. UNESCO Publishing, Paris. 793pp.
Hsia, MH, Morton, SL, Smith, LL, Beauchesne, KR, Huncik, KM & PDR Moeller. 2006. Production of goniodomin A by the planktonic, chain-forming dinoflagellate Alexandrium monilatum (Howell) Balech isolated from the Gulf coast of the United States. Harmful Algae 5: 290-299.
Howell, JF. 1953. Gonyaulax monilata sp. nov.,the causative dinoflagellate of a red tide in the east coast of Florida in August-September 1951. Trans. Amer. Microsc. Soc. 72: 153-15.
Latz, MI, Bovard, M, VanDelinder, V, Segre, E, Rohr, J & A Groisman. 2008. Bioluminescent response of individual dinoflagellate cells to hydrodynamic stress measured with millisecond resolution in a microfluidic device. J. Exp. Biol. 211: 2865-2875.
Loeblich III, AR. 1970. The amphiesma or dinoflagellate cell covering. In: Yochelson, EL (Ed.). Proceedings of the North American Paleontological Convention, Chicago, September 1969, Part 2. G. Allen Press, Lawrence, KS. 867-929.
May, SP, Burkholder, JM, Shumway, SE, Hegaret, H, Wikfors, GH & D Frank. 2010. Effects of the toxic dinoflagellate Alexandrium monilatum on survival, grazing and behavioral response of three ecologically important bivalve mollusks. Harmful Algae 9: 281-291.
Norris, DR. 1983. The occurrence of a toxic dinoflagellate in the Indian River system, Florida. Fla. Sci. 46: 150-153.
Ray, SM & DV Aldrich. 1967. Ecological interactions of toxic dinoflagellates and mollusks in the Gulf of Mexico. 75-83. In: Russell, FE & PR Saunders [Eds.]. Animal Toxins, First International Symposium on Animal Toxins. Pergamon Press, NY.
Taylor, FJR. 1976. Dinoflagellates from the international Indian Ocean Expedition. Bibliothec. Botan. 132: 1-234 + 46 Plates.
Walker, LM & KA Steidinger. 1979. Sexual reproduction in the toxic dinoflagellate Gonyaulax monilata. J. Phycol. 15: 312-315.