Possible source of tetrodotoxin in the starfish Astropecten scoparius

The seasonal variations of toxicity and stomach contents in toxic starfish Astropecten scoparius were detected. The average highest specimen toxicity, expressed as tetrodotoxin (TTX), was 16,821 mouse units (MU). The toxin was composed of TTX only, except April's sample containing mainly TTX along with minor paralytic shellfish poisons. The composition in the stomach of less and more toxic starfish was mainly Veremolpa scabra and Umborium suturale, respectively. The toxicities of U. suturale and V. scabra, found in the starfish stomach were 65 and 33 MU, respectively. For those collected from the coastal waters, U. suturale was toxic with average toxicity value of 77 MU/g, but V. scabra was nontoxic. The toxin in the specimens of U. suturale collected from either the digestive gland of starfish or the coastal waters, was TTX and anhydroTTX only. It indicates that the starfish A. scoparius might mainly accumulate high amount of TTX from U. suturale. Furthermore, both small gastropods U. suturale and Natica psuestes are first reported to contain TTX.