• Alexandrium fundyense is a dinoflagellate
• It has two flagella (one like a belt surrounding the cell body, the other along the body)
• It has a theca, the "house" in which the cell body dwell, which is fit together by cellulosic plates like puzzle pieces
• It lives in the upper layer of the ocean, and has weak mobility, hence it is called plankton
• It is photosynthetic, hence a phytoplankton
• It is widely distributed
• It can cause harmful algal blooms (commonly known as "Red tides") as a result of active reproduction and low grazing by herbivores
• It is capable of producing saxitoxin, a neuromuscular toxin that causes Paralytic Shellfish Poisoning (PSP); the toxin can be accumulated through the food chain and end up in shellfish and some filter-feeding fish, constituting health threat for animals and humans

• Most plastid genes have been transferred to the nuclear genome
• Peridinin as major accessory pigment
• Form II Rubisco that is believed to arise from horizontal gene transfer from a proteobacterial origin

• Gigantic genome (230 pg DNA/cell)
• There are about 143 chromosomes
• Chromosomes are permanently condensed
• There are no typical histone proteins as in other eukaryotes do to package chromosomal DNA
• DNA contains 5-hydroxymethylmuracil, which replaces a large fraction of the thymidine (RAE, P. M. M. 1976. Hydroxymethyluracil in eukaryote DNA: a natural feature of the Pyrrophyta (dinoflagellates). Science 194: 1062–1064.).

Flagella and theca in dinoflagellates

To understand the morphology of A. fundyense, it is helpful to first learn the general morphology of dinoflagellates. Dinoflagellates can be “naked” (no theca, or athecate) or thecate (like A. fundyense). Structure of the theca vary from one group of dinoflagellates to another. Their two flagella can grow in different ways as well.

Thecal plate structure of A. fundyense

It is morphologically identical to A. tamarense (which does not always produce toxins) except for the missing ventral pore on the 1' plate in A. fundyense (Anderson et al. 1994).

North America

• Newfoundland (Hansen, Daugbjerg & Franco 2003)
• Nova Scotia (Cembella et al., 2002)
• Gulf of Maine (Anderson, 1997; McGillicuddy et al., 2003)
• Southern New England (Anderson et al., 2005)

Australia and New Zealand

• Australia (Hallegraeff et al., 1991)
• New Zealand (MacKenzie et al., 2004; Leaw et al., 2005)

Vegetative cells are normal, active cells that  use their two flagella to move. They actively reproduce by binary division.

When environmental conditions become unfavorable, sexual reproduction is induced, resulting in the generation of cysts. A vegetative cell can produce, or become, a gamete, two of which fuse to form a zygote, which develops into a cyst. Cyst cells do not have flagella, but have thick cell walls and contracted cytoplasm. They have a yellow inclusion that fluoresces yellow when excited by blue light. When cysts are ready to germinate, they fluoresce red due to the chlorophyll they have synthesized. A common way to count cysts uses primuline, which fluoresces green to make the cysts more visible.

There are several stages to the Alexandrium life cycle: motile vegetative cells, haploid gametes, diploid zygotes, dormant cysts, and temporary cysts (not shown). Asexual reproduction through binary fission is most common (steps 2-3 in the life cycle). However, Alexandrium species can also undergo a sexual cycle. In sexual reproduction, motile mating types (gametes) fuse, which produces a motile diploid zygote (called a planozygote; steps 4-5). The planozygote will swim, then take the form of a dormant cyst and settle to seabed (steps 5-1). It will wait until environmental conditions are ideal before germinating (steps 1-2). There is also an endogenous (internal) annual clock that controls germination. So cysts can be a seeding population for a bloom of A. fundyense.

Information Sourced From:

• MicrobeWiki: Alexandrium

• >28 species have been described
• This genus is distributed globally
• Some species produce toxins, some do not
• Relatively young lineage among dinoflagellates (77 million years before present; A. tamarense/fundyense complex arose around 23-45MYBP)
• Distinction of documented species: difficult

References

• Uwe John, Robert A. Fensome, and Linda K. Medlin 2003. The Application of a Molecular Clock Based on Molecular Sequences and the Fossil Record to Explain Biogeographic Distributions Within the Alexandrium tamarense "Species Complex" (Dinophyceae). Mol. Biol. Evol. 20(7):1015-1027.
• http://dinos.anesc.u-tokyo.ac.jp/plankton/tree/p-tree16.htm

• Eukaryota
• Alveolata
• Dinophyceae
• Gonyaulacales Taylor 1980
• Gonyaulaceae
• Alexandrium Halim, 1960
• Alexandrium fundyense Balech 1985

Reference

• Steidinger, K. A., and K. Tangen. 1997. Dinoflagellates, p. 387-584. In Tomas, C. R., (ed.), Identifying marine phytoplankton. Academic Press, New York. Pp. 387-584.

• Nuclear genes are highly “redundant” (Zhang et al., 2006. J. Euk. Microbiol. 53: 142-150; Erder and Anderson 2006. BMC Genomics. 7: 88)
• mRNA are spliced leader trans-spliced (Zhang et al. 2007. PNAS104: 4618-4623)
• Little transcriptional regulation (Erder and Anderson 2006. BMC Genomics. 7: 88 )
• Mitochondrial mRNA subject to editing (Zhang and Lin 2005. J. Euk. Microbiol. 52: 538-545)

Biosynthetic pathway for saxitoxin (modified from Shimizu 1993). (1) Claisen condensation between arginine and acetate; (2) amidinotransfer from a second arginine to α-amino group of first intermediate; (3) formation of the first heterocycle by a retro-aldol-like condensation; (4) formation of the remaining two heterocycles by unknown reactions; (5) introduction of methyl side chain by electrophilic attachment; (6) rearrangement involving 1,2-H shift from C-6 to C-5; (7) epoxidation of methyl side chain; (8) opening of epoxide to an aldehyde; (9) reduction of aldehyde to alcohol; (10) O-carbamoyl transfer and oxidation reactions completing the STX molecule. "=X" in the intermediates may be two hydrogens, a keto, or two hydroxy groups.

Reference

• Kellmann, R & Neilan, B. 2007. Biochemical characterization of paralytic shellfish toxin biosynthesis in vitro. Journal of Phycology  43 (3), 497-508).

PSP is caused by a suite of chemically slightly different toxins. Their differences may lie in the structure of the side groups. A partial list is shown in the table; more than 20 types have been identified. Different Alexandrium species may produce different combinations of these toxins.

Reference:

• Aquatic (Marine and Freshwater) Biotoxins: Environmental Health Criteria No.37. Published under the Joint Sponsorship of the United Nations Environment Program, the International Labour Organization, and the World Health Organization, 1984. Geneva: WHO, 1984. 96 pp, (ISBN 92-4-154097-4)

• The common name is saxitoxin. It is a derivative of arginine and acetate (Shimizu 1986. Pure & Appl. Chem. 58(2): 257—262).
• It is a sodium channel blocker.
• Toxin production is cell cycle-dependent, most actively produced in the G1 phase of the cell cycle (Taroncher-Oldenburg and Anderson 2000).
• Symptoms of poisoning: In mild cases, symptoms begin within 30 minutes and may include a tingling sensation or numbness around lips, gradually spreading to face and neck; prickly sensation in fingertips and toes; headache, dizziness, nausea, vomiting, and diarrhea. In extreme cases, it may lead to muscular paralysis, pronounced respiratory difficulty, and a choking sensation. Death through respiratory paralysis may occur within 2-24 h of ingestion. (Hallegraeff, G. M. 1993. A review of harmful algal blooms and their apparent global increase. Phycologia 32: 79-99; also see http://www.answers.com/topic/paralytic-shellfish-poisoning.)
• Lethal dosages: In mice, the intraperitoneal saxitoxin LD50 parentally is 3-10 µg/kg body weight and orally is 263 µg/kg body weight (death within minutes of respiratory failure). LD50 is dosage at which 50% of the affected population die. In humans, oral lethal dosage is 9-10 mg/kg for an adult. Assuming a 70 kg person, this is ~700 mg.

The map below shows areas with records of paralytic shellfish poisoning (PSP) toxins. The number of affected locations has increased dramatically over the last several decades.

Blooms occur when cells divide faster than they are grazed. The 2005 bloom in Gulf of Maine area was the largest in New England since 1972. The map below shows areas closed to shellfishing (red lines and blue square).

Reference

NOAA Awards More Emergency Funding to New England Red Tide Response Effort. NOAA Magazine. 9 June 2005.

• AlgaBase
• ITIS
• uBio
• NCBI taxonomy browser
• GBIF Portal
• Northeast PSP: New England Harmful Algal Bloom / Red Tide information
• Harmful Algae