| In the Wake of the Giant Squid |
| Sunday, 13 January 2008 | |
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James Bullock explores the underwater world of sea monsters With our deep seas teeming with a seemingly endless array of fascinating creatures, no animal captures the imagination quite like the giant squid. A sea monster straight out of seafaring legend, it has become the inspiration for countless works of fiction, from the early Norse tales of the Kraken to Jules Verne’s Twenty Thousand Leagues Under the Sea and the film Pirates of the Caribbean. Neither is it ever far from the scientific and even global headlines whenever new discoveries are announced regarding this enigmatic animal. The giant squid, Architeuthis dux, is a genuinely massive cephalopod belonging to the Architeuthidae family, which simply translates as ‘arch-squid’. The largest specimens are estimated to be an enormous 13 metres from caudal fin to tentacle tip, with the mantle which makes up the bulk of the squid reaching lengths of up to two-and-a-half metres. That’s a total length of more than seven times the height of an average man and puts the giant squid amongst the largest living organisms on Earth. Although claims of 20-metre-plus squid are widely discredited (with accusations of ‘tentacle stretching’), there are still many who believe there are even larger cephalopods hiding deep in the oceans. Squid-like sea monsters have been written about since Norse sailors first encountered them in the thirteenth century. Architeuthis, however,was not scientifically classified until 1857 when the Danish zoologist Japetus Steenstrup succeeded in bringing it to the attention of his contemporaries, who were studying specimens that had been causing interest by intermittently washing up on beaches around the globe. At first, his work was based on local legends and sketchy evidence, with samples dating back as far as the 1700s. But as the number of sightings of dead animals increased, the sceptical scientific community gradually began to accept the giant squid as more than just a tall story for sailors. Yale’s Professor Addison E.Verrill added credibility to Stennstrup’s research in 1873 when he identified two beached ‘Kraken’ as Architeuthis. Also in 1873, a group of frightened Newfoundland fishermen killed “a sea monster” and took it to their local priest, who displayed it draped over his bathtub. This was the first complete giant squid specimen available to science.Two mysterious mass strandings followed during the late nineteenth century, which left a number of giant squid beached off the coast of Newfoundland, Canada, and around the New Zealand shoreline. Still no explanation has been accepted as to the reason for these, and to date there has been no repeat of this strange occurrence. Nevertheless, as a result, many giant squid specimens were made available for scientific study. So what has changed since then and, Johnny Depp aside, how does Architeuthis fit into the public consciousness and twenty-first century science? In September 2005, headlines were made around the world when two Japanese researchers, Tsunemi Kubodera and Kyoichi Mori, finally succeeded in photographing the living cephalopod in its natural habitat, 900 metres below the surface. The photos showed a mass of tentacles emerging from the black depths and vigorously attacking a line baited with smaller squid. It was so active that, having been snared, it took the squid four hours to struggle free, leaving behind a five-and-a-half-metre-long tentacle for the scientists to study. This unexpected sample allowed Kubodera to confirm the identity of the specimen through DNA sequencing and morphological analysis of the paired suckers, which are unique to giant squid, and helped to put its total length at around eight metres.The key outcome from this study was the wider acceptance of the idea that the squid is an active and aggressive predator, snaring its prey with its powerful feeding tentacles, rather than a passive drifting scavenger. The key to locating Architeuthis was to track its principal predator, the sperm whale (Physeter macrocephalus). Believed until recently (when joined by the sleeper shark) to be the only animals big enough to predate the giant squid, sperm whale specimens are regularly recovered with undigested chitin squid beaks in their stomachs. Giant sucker scars on the whales’ skin suggest that the conflict is not entirely one-sided, and much focus has been placed on these encounters as a basic location system for giant squid. Dr Kubodera explains, “the reason why we thought those large mesopelagic squids could escape from trawl nets and submersibles when approached was due to the unusual undulation and strong light they produced. Instead, we applied a compact underwater camera and video system which caused a minimum disturbance to the deep-sea environment.” This approach has proved extremely successful, as he has obtained images not only of Architeuthis, but also of the beautiful Taningia danae octopus-squid, filmed earlier this year exhibiting a stunning bioluminescent hunting behaviour. Besides this, last December, Dr Kubodera followed up on his breakthrough images with the first ever video of a giant squid as it was pulled to the surface from a depth of 650 metres. It is often said that the deep ocean is less explored than the surface of the Moon but it is safe to say that there is a lot more life in the oceans. Without doubt there are many undiscovered species left at the bottom of our seas and it is very tempting to believe that there are still more monsters lurking out there. Dr Kubodera agrees: “There should be a huge biomass of large cephalopods existing in the mesopelagic waters, given the feeding habits of the top marine predators, especially the sperm whales.” Yet, he notes, they are largely hidden “behind the darkness of the deep-sea.” This was reinforced in 1925 when it was discovered that Architeuthis was not the only massive cephalopod inhabiting our oceans.Two strange barbed tentacles were found in the stomach of a sperm whale. Morphologically different from the giant squid due to the presence of swivelling hooked barbs protruding from the tentacle suckers, this identified a species previously unknown to science, the so-called ‘colossal’ squid. The colossal squid (Mesonychoteuthis hamiltoni) is in fact even larger than the Architeuthis, at least in terms of weight (it is often misreported as being longer, though its tentacles are usually less pronounced). Its football-sized eyes are also the biggest of any animal. Very little is known about the colossal squid and only a few specimens have ever been recorded— though in February this year a trawler in the Antarctic Ross Sea picked up the largest colossal squid, and the first male specimen, ever seen. At 10 metres long and just short of half a tonne, it is not only the largest squid, but the largest invertebrate ever recorded. The rarity of the creatures has meant that our understanding of deep-sea cephalopods is limited. In an interesting historical note, the giant squid was proposed as an explanation for another one of the ocean’s mysteries—the ‘St Augustine Monster’. An enormous five tonne mass of rotting white flesh that washed ashore in Florida in 1896, it is the most famous example of what are now commonly known as ‘globsters’. It was believed by many observers (including the attending physician and many subsequent researchers) to be a stranded “gigantic octopus,” with a predicted tentacle span of anything up to 60 meters. However, this idea changed in 1995, when Sidney Pierce and colleagues took a closer look at a sample that had been kept for posterity at the Smithsonian Institute. They used electron microscopy to show that the material was almost pure collagen, claiming that it had neither the necessary fibre arrangement nor the biochemical signature to be of invertebrate origin. They came to the rather more mundane conclusion that the giant corpse was in fact the decomposed skin and blubber of a sperm whale, largely dismissing the idea of the gigantic octopus. Several species of the more modest giant octopus do however exist and are well documented. The biggest confirmed measurement belongs to the rare four metre-long gelatinous octopus, Haliphron atlanticus, as recorded in 2002 by New Zealand biologist Dr Steve O’Shea. There is undoubtedly more work to be done before we fully understand the giant squid. Despite being found in every ocean of the world, very little is known about its life cycle and nothing is known of its social behaviour. Plans are already in place to attempt to raise squid larvae in aquariums in the hope of observing some of its life cycle. As research continues and commercial fishermen begin to trawl at even greater depths for healthy fish stocks, bringing more intact specimens up to the surface, it seems only a matter of time until we know what else the deep ocean is hiding from us. Here be monsters… James Bullock is a PhD student in the Department of Zoology |
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