The toxinology of sea snakes: A systematic review

Sea snakes belong to Hydrophiidae family mainly are found in tropical and subtropical waters of the world including the Persian Gulf. Their highly lethal venoms are more potent than snakes with terrestrial origin and contain complex mixtures of organic and inorganic bioactive substances, such as enzyme, and non-enzymatic proteins. There were limited studies on the venoms and toxins of sea snake; hence, the aim of this systematic review was to investigate the toxinological dimensions of sea snakes.
In order to investigate of the toxins of sea snakes, the “Hydrophis schistosus toxin", "Hydrophis cyanocinctus toxin", " Hydrophis lapemoides toxin", "Hydrophis spiralis toxin", and "Lapemis curtus toxin " terms were searched separately, in "PubMed database", in 10/08/2016 which obtained 32, 9, 2, 2 and 4 papers, respectively. The "Hydrophis gracilis toxin" term had no any results. For the “Hydrophis gracilis" term, two studies were obtained. The first one related to the sea snakes phylogenetic characteristics and the second one shared with other search results and well-connected with the issue. Some papers were similar in different searches. Of these, those studies were selected that had direct relevance to the subject .
The main isolated toxins from different sea snakes venoms included three-finger toxin (3FTx (short chain neurotoxins isoforms: AAL54893, AAL54892, ABN54806; long chain neurotoxins isoforms: AAL54894, AAL54895, P68416 , ABN54805), pelamitoxin (P62388), phospholipase A2 (both the basic and acidic PLA2), two phospholipases A2 (PLA2-H1 and H2), cysteine-rich secretory protein (CRISP), snake venom Zn2+metalloproteinase (SVMP), L-amino acid oxidase (LAAO), 5′-nucleotidase, Hydrophitoxins a, b and c, Hydrophis ornatus a, Hydrophis lapemoides a, PDGF and α- neurotoxins of rSN311, rSN316 and rSN285. Each toxin and protein family presents a wide range of pharmacological activities. Some of these neurotoxins were linked to acetylcholine receptors in the neuromuscular junctions. These toxins showed protease (gelatinase and caseinase) activities, and/or they produce the myonecrosis and biochemical and histopathological changes.
There is scant variability in the venom composition in the same and different species of sea snakes. Our study revealed that there is a rather simple venom profile with an affinity towards a lethal mixture of high abundance of neurotoxins and PLA2s, and lower amounts of toxins such as CRISP, SVMP and LAAO.