Octopus (Abdopus) sp. 5 were collected from a reef flat at Cooke Point, Port Hedland in northern Western Australia. The octopi had a body size of between 5-6 cm and tentacle span of between 20 and 30 cm.Specimens were euthanased by rapid decapitation, stored at -20°C and shipped frozen to the Australian Institute of Marine Science in Townsville. Three legs from each of the four individuals were pooled for toxin extraction. Each of the four samples was extracted with 80% ethanol, homogenised, sonicated three times for 10 minutes, then clarified by centrifugation. This process was repeated two additional times with fresh extraction solvent. For each of the four extracts, the three supernatants generated were pooled, filtered through 0.2 mm nylon filters and lyophilised. Dried extracts were reconstituted in 0.05 M acetic acid and passed through a centrifugal ultra-filter and the ultra filtrates then used for radio-receptor assay and preliminary chemical analysis.Quantitation of STX concentration equivalents (STXeq) with [³H]-STX radio-receptor assays using saxiphilin and voltage gated sodium channel, was performed and octopus extracts were assayed in triplicate for inhibition of STX binding in the sodium channel and saxiphilin assay.All sample extracts which competed with [³H]-STX in the radio-receptor assays were analysed by LC-FLD for STX, decarbamoylSTX, neoSTX, 11-hydroxysulphate STXs (GTX1-6), N-sulfocarbamoyl-11-hydroxy-sulphate STXs (C1-4), hydroxybenzoate STXs and TTX.Identification of suspect toxin peaks was undertaken by mass spectrometric analysis of separated toxins using liquid chromatography-mass spectrometry (LC-MS) performed in single ion monitoring (SIM) mode.
Previous research indicates that Port Hedland on the north-west coast of Australia is a source of marine animals, encompassing a range of crustacea, gastropod and bivalve molluscs, which harbour both tetrodotoxin (TTX) and paralytic shellfish toxins (PSTs). This study was undertaken as part of a renewed investigation into paralytic shellfish toxin distribution in benthic organisms in this region.
This was the first time that saxitoxin had been reported from this family of predatory molluscs and highlights the need for greater public awareness of risks associated with consumption of previously unrecognised vectors of paralytic shellfish poisoning, such as octopus and other benthic feeders.
