The Effect of Sampling Methods on the Apparent Constituents of Ink from the Squid Sepioteuthis australis
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Results of experiments conducted on ink recovered from the squid Sepioteuthis australis indicate that there is no epinephrine or protein naturally present in the ink as it would be ejected in vivo. Protein content was effectively zero when ink was syringed from the duct end of the ink sac of freshly killed animals. By contrast, there were proteins in samples collected from dead specimens where ink was collected by a stripping method. From these samples, a single large molecular weight protein was identified as having tyrosinase activity. Digestion of syringed ink did not yield signs of melanin-bound proteins. Analysis of supernatants after centrifugation of squid ink consistently revealed the presence of DOPA, dopamine, and taurine, whereas epinephrine and nor-epinephrine were recorded from what was believed to be contaminated ink. Histological investigations of the ink sac revealed a compartmentalised glandular structure distal to the duct end. Closer observation of the glandular tissue showed that compartments increased in size as they matured and moved further into the lumen. It was concluded that the presence of epinephrine and tyrosinase (or a related protein) in the ink of S. australis could be attributed to rupturing of basal glandular compartments or contamination from other sources during the extraction process.
Key WordsSepioteuthis australis Ink sac Ink Protein Tyrosinase DOPA Dopamine Taurine
We thank all those who accompanied us on squid fishing expeditions. Andrew Beck and Shaun O’Sullivan produced high quality sections of ink sac tissue. Miguel De Barros Lopez gave us invaluable advice and guidance. The School of Pharmacy and Medical Sciences, through Allan Evans, gave us material support and encouragement without which we could not have conducted this work.
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