Algae and Fishes: Benefits and Hazards
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freshwater while others are marine. Cyanobacteria are responsible for the formation
of harmful blooms, in nearly all water bodies.
5.1.1 Cyclic Peptides
Genera like Microcystis, Anabaena, Planktothrix, Oscillatoria, Nostoc, Haplosiphon
and Anabaenopsis are responsible for the production of cyclic peptides. Hepatotoxins produced in freshwater (microcystins) and marine water (nodularins) operate
through their strong covalent binding to hepatic enzymes called protein phosphatases
thereby causing their inactivation, depolymerization of hepatic cells, hemorrhage and
eventually death.
5.1.2 Neurotoxic Alkaloids—Anatoxins and Saxitoxins [39]
These neurotoxins produce rapid respiratory arrest. Three groups of cyanobacterial
neurotoxins are found:
• anatoxin-a and homoanatoxin-a, similar to acetyl choline in effect,
• anatoxin-a(S), which is an anticholinesterase, and
• saxitoxins, or paralytic shellfish poisons (PSPs) which block nerve cell sodium
channels. Anatoxin-a was found in Anabaena, Oscillatoria and Aphanizomenon
whereas homoanatoxin-a from Oscillatoria, anatoxin-a(S) from Anabaena, and
saxitoxins from Aphanizomenon, Anabaena, Lyngbya and Cylindrospermopsis.
The alkaloid toxins are diverse heterocyclic nitrogenous compounds. The nonsulphated alkaloid toxins of freshwater cyanobacteria (anatoxins and saxitoxin)
are all neurotoxins. The sulphated PSPs, C-toxins and gonyautoxins (sulphated
derivatives of saxitoxin) are also neurotoxins, but the sulphated alkaloid cylindrospermopsin blocks protein synthesis with a major impact on liver cells. Some
marine cyanobacteria also contain alkaloids (lyngbyatoxins, aplysiatoxins) which
are dermatoxins [39].
5.2 Toxins Produced by Dinoflagellates
These eukaryotic unicellular protists possess two unequal flagella: one smooth longitudinal & one hairy transverse. If two flagella arise from anterior end they are called
desmokont and if they arise in grooves they are called dinokont. There are also two
depressions one transverse called cingulum and one longitudinal called sulcus. The
nucleus is dinokryon. They are either thecate or naked. The emphysema vesicles
are found beneath plasma membrane. It can form cellulose plates in thecate species.
They can be photo-or heterotrophs. They are classified according to the International
Botanical code as well as the International Zoological code. Seventy five percent of
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freshwater while others are marine. Cyanobacteria are responsible for the formation
of harmful blooms, in nearly all water bodies.
5.1.1 Cyclic Peptides
Genera like Microcystis, Anabaena, Planktothrix, Oscillatoria, Nostoc, Haplosiphon
and Anabaenopsis are responsible for the production of cyclic peptides. Hepatotoxins produced in freshwater (microcystins) and marine water (nodularins) operate
through their strong covalent binding to hepatic enzymes called protein phosphatases
thereby causing their inactivation, depolymerization of hepatic cells, hemorrhage and
eventually death.
5.1.2 Neurotoxic Alkaloids—Anatoxins and Saxitoxins [39]
These neurotoxins produce rapid respiratory arrest. Three groups of cyanobacterial
neurotoxins are found:
• anatoxin-a and homoanatoxin-a, similar to acetyl choline in effect,
• anatoxin-a(S), which is an anticholinesterase, and
• saxitoxins, or paralytic shellfish poisons (PSPs) which block nerve cell sodium
channels. Anatoxin-a was found in Anabaena, Oscillatoria and Aphanizomenon
whereas homoanatoxin-a from Oscillatoria, anatoxin-a(S) from Anabaena, and
saxitoxins from Aphanizomenon, Anabaena, Lyngbya and Cylindrospermopsis.
The alkaloid toxins are diverse heterocyclic nitrogenous compounds. The nonsulphated alkaloid toxins of freshwater cyanobacteria (anatoxins and saxitoxin)
are all neurotoxins. The sulphated PSPs, C-toxins and gonyautoxins (sulphated
derivatives of saxitoxin) are also neurotoxins, but the sulphated alkaloid cylindrospermopsin blocks protein synthesis with a major impact on liver cells. Some
marine cyanobacteria also contain alkaloids (lyngbyatoxins, aplysiatoxins) which
are dermatoxins [39].
5.2 Toxins Produced by Dinoflagellates
These eukaryotic unicellular protists possess two unequal flagella: one smooth longitudinal & one hairy transverse. If two flagella arise from anterior end they are called
desmokont and if they arise in grooves they are called dinokont. There are also two
depressions one transverse called cingulum and one longitudinal called sulcus. The
nucleus is dinokryon. They are either thecate or naked. The emphysema vesicles
are found beneath plasma membrane. It can form cellulose plates in thecate species.
They can be photo-or heterotrophs. They are classified according to the International
Botanical code as well as the International Zoological code. Seventy five percent of