Hundreds of years ago, sailors were terrified by the Kraken, a dreadful sea monster capable of sinking ships and with a taste for human flesh. Today we know the legends of this monster were based on sightings of giant squids. This animal belongs to the genus Architeuthis and was the subject of many scientific studies. Despite its enormous size (up to 18m), the giant squid is astoundingly elusive and much of its biology remains unknown. Thus shrouded in mystery, Architeuthis is almost a mythological creature and has a place both in science and in myth: the very last of the legends to persist to this day.

Architeuthis; cephalopod; giant squid; Microcosmus marinus; sea serpent

For the first navigators, the sea was a great unknown, treacherous, unstable, and above all, dangerous; yet, it was the only way to reach certain places. For these men, the sea seemed to hide in its inconceivable depths a horde of lurking monsters. Even the bravest seafarers showed a respectful dread of the sea, and the stories they told gradually became legends, for, as the saying goes, “the tale grows in the telling.” An encounter with any unknown animal in the open sea had the potential to gain a mythological edge. For a monster worthy of its tales, gigantic size was not enough; it should also have some means to attack a ship and kill its crew.

Over the centuries, many sea monster legends were born and forgotten; only a few have reached our days. The Kraken, one of these “survivors,” is perhaps the largest monster ever imagined by mankind. Its legend was also born from seamen’s stories, but it was much modified and strengthened over the years. Right from the start, the Kraken was universally incorporated into Nordic mythology and folklore (Hamilton, 1839). According to an obscure, ancient manuscript of circa 1180 by King Sverre of Norway, the Kraken was just one of many sea monsters (Lee, 1883). Still, it had its own peculiarities: it was colossal in size, as large as an island, and capable of sinking ships; it haunted the seas between Norway and Iceland, and between Iceland and Greenland (Lee, 1883).

Two other Nordic sea monsters have records almost as old as the Kraken, appearing in the “Saga of Örvar-Oddr” (an Icelandic story from the thirteenth century by an anonymous author); their names are Hafgufa (“sea-mist”) and Lyngbakr (“heather-back”). The habits of theses monsters were later described in the Norwegian encyclopedia Konungs Skuggsjá (from circa 1250, also by an anonymous author). They shared many features with the Kraken, namely their gigantic size (as big as an island or mountain) and their inclination to attack ships and their crews. Therefore, these monsters have been considered as references to the Kraken and are treated as the same monster.

However, nearly all sea monsters had some (or all) of these traits, and as such many of them were linked to or confused with (or, to borrow the lexicon of taxonomy, “placed in synonymy with”) the Kraken over the centuries. Their features only reflected the fears of the first navigators, and the Kraken proved to be the strongest figure in their folklore, dragging every other sea monster under its shadow. The other monsters included the Aspidochelone (or Fastitocalon), a creature also similar to an island; possibly the bishop-fish (also known as the sea bishop, sea monk or monk-fish), a sea monster whose legend might also have originated from encounters with seals, sharks or walruses; and, finally, even the biblical Leviathan (Wallenberg, 1835; Ellis, 1998; Matthews, Matthews, 2005).

This confusion of creatures explains why the Kraken is found under so many guises in art and literature, from a misshapen mass to a giant cephalopod, passing through creatures as distinct as a humanoid sea giant, a huge, usually lobster-like, crustacean, and a sea serpent (Magnus, 1555; Gesner, 1587; Ashton, 1890). It was only much later that the Kraken’s figure stabilized. Until the beginning of the eighteenth century, science and myth were not clearly separated, and the Kraken slowly but steadily took on the shape of a giant cephalopod, largely due to the increase in the number of sightings of giant squids as seafaring became more common. This culminated in the Kraken’s “modern” form as a giant squid, which can be understood as a return to the animal that long ago originated the legend.

Architeuthis, wanted dead or alive

As seen above, all Architeuthis specimens recovered until the beginning of the twentieth century were almost exclusively stranded on beaches. Subsequent marine research began using new methods to capture animals, including trawling nets, but few were the giant squids captured at sea. This even led some authors (Roper, Boss, 1982) to question whether squids were able to avoid capture somehow. In any case, all the recovered animals were dying or already dead (and in a bad state of preservation); in the worst cases, only parts of the animal, like a tentacle fragment, were recovered. The difficulty in finding specimens is reported by Aldrich (1991), who started distributing posters saying, “Wanted! Dead or alive”, and even offering rewards. (He says he managed to secure many specimens this way.)

Even so, a large number of records were gathered, giving a good idea of the geographical distribution of Architeuthis (see Ellis, 2004, for an exhaustive list of all animals sighted and/or recovered). With all these data, it is clear that Architeuthis is a cosmopolitan genus, i.e. it occurs in the entire world, but it is especially abundant in the North Atlantic, the western North Pacific and off the South African and New Zealand coasts (Robison, 1989; Aldrich, 1991; González et al., 2000). Some authors (Roper, Young, 1972; Nesis et al., 1985) suggested that Architeuthis reproduced in warm waters, where the juvenile would grow, and then the adults would migrate to temperate or cold waters, where they would feed, grow and mature. However, this hypothesis was disproved when additional data surfaced: Roeleveld & Lipinski (1991) showed that  Architeuthis  live and reproduce in the same area.

Architeuthis, the single genus of the family Architeuthidae, has about 20 species, many precariously described, usually based only on tentacle fragments (Figure 10), beaks (Figure 11) or other body parts (Clarke, 1966, ¹⁹⁶⁸; Roper, Boss, 1982; Roeleveld, 2000). Until the 1940s, it was common practice to describe a new species whenever a new fragment was found, as Steenstrup, Verrill and others had done. This is why the descriptions were never accompanied by clear diagnoses to distinguish among the many species (Clarke, 1966; Roper, Boss, 1982; Roeleveld, 2000). Thus, the family’s taxonomy remains messy to this day, in large part due to the scarcity of well-preserved material and the logistical difficulty of conducting a comparative study with such huge animals. Moreover, the existing material is scattered throughout many museums and universities in different parts of the world, and a good portion of the original specimens were discarded, since the institutions are hardly equipped to house more than one of these monsters (Aldrich, 1991). This confusion has led many researchers to avoid identifying the species in their works, referring to the object of their studies simply as Architeuthis sp. or even onlyArchiteuthis.

Therefore, it can easily be seen that the genus is in dire need of a taxonomic revision, especially when taking into account the large number of specimens recovered since the species’ original descriptions. A handful of authors have risked issuing some opinions regarding the group’s taxonomy, but none have conducted any proper revisionary work. Some believe that few of the current species are valid: for Roper and Boss (1982), for instance, the genus only has three valid species: A. dux from the North Atlantic,A. japonica from the North Pacific, and A. sanctipauli from the southern hemisphere. Others (Aldrich, 1991; Förch, 1998; Roeleveld, 2000) claim that all the genus diversity can be accommodated in a single species of variable morphology, namely A. dux. However, the division into a few species seems better grounded, for some striking differences have been described between the animals from the Pacific and from the Atlantic, as well as between the two “populations” from the North Atlantic (Roper, Young, 1972). Besides, there is still the curious case of the “dwarf”  Architeuthis,   giant squid that reaches maturity with an astoundingly small size, less than 30cm (Toll, Hess, 1981). It is very likely a new species and, according to Roeleveld and Lipinski (1991), also deserves a separate genus to accommodate it (albeit still in the family Architeuthidae).

The biology of the elusive Architeuthis

Little is known about the biology of giant squids. Since almost all the available specimens for study have been found dead or dying, little information could be extracted from them (Roper, Sweeney, Nauen, 1984). Even so, malacologists have made every effort to extract as much as they could from their specimens. Therefore, knowledge has advanced slowly (and is permeated by speculations), depending largely on the luck of finding good specimens to work with. Still, a great deal of information has been gathered in this century and a half of studies.

The coloring of Architeuthis goes from dark red to brown, but it very likely shares with other squids the ability to instantly change color (Roper, Boss, 1982; Aldrich, 1991). The giant squid’s eyes are the largest in the animal kingdom, but are proportionally small when compared with other cephalopods (Roeleveld, Lipinski, 1991). Cephalopod eyes tend to be as complex as those of birds and mammals, and since vision is their main sense, the large eyes of Architeuthis most likely serve some purpose in the dark depths it inhabits. The importance of its ability to change color at such depth and the function of its eyes in locating prey and ink in escaping from predators (its ink sac is relatively small) remain elusive (Ellis, 2004).

Like some other squid species (such as the families Enoploteuthidae, Histioteuthidae and Bathyteuthidae), Architeuthis has pockets in its muscles containing a solution of ammonium ions (NH₄⁺), which is less dense than seawater (Clarke, Denton, Gilpin-Brown, 1979; Boyle, 1986; Robison, 1989). This solution grants the giant squid neutral buoyancy, i.e. it can keep itself steady without having to continually expend energy swimming (Roper, Boss, 1982). This feature was first thought to had evolved only once in the squids’ history and that all the families belonged to the same lineage (Roeleveld, Lipinski, 1991), but this hypothesis has recently been questioned (Voight, Pörtner, O’Dor, 1994). Besides, when some other morphological and anatomical features are taken into account, the family Architeuthidae seems to be a relatively ancient lineage among squids (Roeleveld, Lipinski, 1991).

Robson (1933) was the first researcher that tried to discover something about the giant squid’s way of life through its anatomical structure. This was the beginning of a heated debate in the scientific literature about the capabilities of Architeuthis. Some authors defend the idea of an agile, powerful predator worthy of the erstwhile myths. For them, the animal’s powerful musculature, mainly in its funnel and mouth, as well as the high levels of enzymatic activity and protein concentration in the muscles indicate a good swimmer, apt for capturing active prey (Clarke, 1966; O’Dor, 1988; Robison, 1989; Aldrich, 1991; Seibel, Thuesen, Childress, 2000). On the contrary, there are some studies indicating that it has a limited oxygen transport capacity in the blood (Brix, 1983, but his results have been fiercely contested by Boyle, 1986) and weak muscles in the fins and funnel (Robson, 1933;Roper, Boss, 1982), with a small concentration of proteins, lipids, cholesterol and glycogen (Rosa, Pereira, Nunes, 2005). This has led some authors to consider the giant squid a slow and relatively weak animal, preying by ambush with its long tentacles (Robson, 1933; Roper, Boss, 1982; Pérez-Gándaras, Guerra, 1989; Roeleveld, Lipinski, 1991).

Aldrich (1991) claimed that those who considered Architeuthis a weak swimmer confused speed with agility and maneuverability. Therefore, the giant squid would have low maneuverability and agility, but would be a potent swimmer, capable of reaching great speeds; at least fast enough to escape its main predator, the sperm whale (Physeter macrocephalus). Aldrich (1991)cites – Grønningsæter (1946), who sighted a giant squid swimming on the sea surface and calculated its speed at 20 to 25 knots (37 to 46km/h); nevertheless, this record remains doubtful (Ellis, 2004). In any case, the giant squid’s cruising speed, its most used kind of movement, would not require such powerful muscles as expected by some authors, since it uses very little of the cephalopods’ muscular capability (Ellis, 2004).

The stomach contents of an animal can be used to discover its diet and therefore infer its feeding strategy (and, indirectly, ascertain whether Architeuthis is indeed a powerful predator). Despite the fact that a squid’s beak and radula turns almost all food into unrecognizable bits (the Architeuthis beak reaches up to 15cm and the radula 10cm; Roper, Boss, 1982), some information can sometimes be extracted from its stomach contents.  Architeuthis feed mainly on fishes and squids, and many prey species have been identified (Roper, Young, 1972; Pérez-Gándaras, Guerra, 1978, ¹⁹⁸⁹; Toll, Hess, 1981; Förch, 1998; Lordan, Collins, Perales-Raya, 1998; Bolstad, O’Shea, 2004). Crustaceans, bivalves and other benthic animals, as well as algae, have sporadically been found (Aldrich, 1991; Förch, 1998; Lordan, Collins, Perales-Raya, 1998), but are either considered secondary ingestion (i.e. they would have been previously ingested by the prey) or are present only in stranded Architeuthis specimens and are therefore not considered natural components of its diet (Bolstad, O’Shea, 2004). As such, the giant squid’s diet is consistent with that of both an active predator and that of an ambush predator. A very welcome answer comes in the form of an exceptional report by Kubodera and Mori (2005): unprecedented film footage of a live Architeuthis in its natural habitat, 900m deep in the North Pacific. These authors attained this feat after many decades of frustrated efforts by tens of other researchers. The film shows many images of the squid grabbing bait, showing that it is indeed a fast and powerful swimmer, capturing its prey with its long, strong tentacles. Nevertheless, in order to end the debate once and for all, the only thing remaining is to see a live Architeuthiscapturing live, active prey.

The vertical distribution of Architeuthis, i.e. the depths at which it lives, is also somewhat uncertain. At first, it was thought that these animals inhabited abyssal depths (Steenstrup, 1857), but more recent evidence points to another pattern. The vertical distribution of the predators of Architeuthis can be used to infer where the giant squid lives. Juvenile giant squids are preyed upon by sharks and bony fishes (Roper, Young, 1972; Cherel, 2003), while adults are preyed upon almost exclusively by sperm whales (Roper, Boss, 1982; Clarke, 1980;Aldrich, 1991). Therefore, it is claimed that the giant squid lives between the surface and 1,100m deep (possibly reaching 2,000m; Roper, Boss, 1982). However, there is evidence that there could be differences: (1) in the depths inhabited by different populations (or species) around the globe (Roeleveld, Lipinski, 1991); (2) among age classes, with juvenile squids living closer to the surface and adults inhabiting greater depths (Roper, Boss, 1982; Lu, 1986; Robison, 1989; Förch, 1998); (3) for the same animal, which could vertically migrate daily, living closer to the surface during the day but deeper during the night (Roeleveld, Lipinski, 1991).

Sperm whales are the great predators of adult Architeuthis (Roper, Boss, 1982; Aldrich, 1991) and the battles between these titans are perhaps more frequent than once imagined. It is very common to find scars on whales’ skin (Figure 12) left by giant squids’ suction cups, whose edges are armed with small but sharp chitinous denticles (Roper, Boss, 1982). Both the arms and the tentacle’s clubs have suction cups, but the scars are probably caused by the squids’ arms (Ellis, 2004), even if the reconstruction of such battles show the tentacles wrapped tight around the whale (Figure 13). Architeuthis tentacles can reach more than 10m in length, but it is impossible for the animal to use them as constricting weapons, for they lack the musculature for this (Roper, Boss, 1982; Ellis, 2004). A giant squid could never overcome a sperm whale in a duel (actually a preying attempt by the latter) and its only option would be to quickly escape (Aldrich, 1991). Surprisingly, Aldrich (1991) reports similar scars to those found on sperm whales in specimens of Architeuthis, meaning that some sort of confrontation may occur between conspecifics. Unfortunately, it is not possible to tell if such disputes are related to feeding, reproduction or even to some other unanticipated reason. This piece of information could also be related to the reports of supposed cannibalism (Bolstad, O’Shea, 2004), in which pieces of tentacles and arms of Architeuthis were found in the stomach contents of conspecifics. Curiously, Architeuthis,  as well as many other cephalopods, seems to be able to regenerate lost portions of its tentacles (Aldrich, Aldrich, 1968).

Data about Architeuthis reproduction are also scarce. The giant squid seems to show great sexual dimorphism in size, with females growing much larger than males; however, the implications of this fact remain unknown (Hoving et al., 2004). Reproduction in cephalopods occurs with the transfer of spermatophores, small structures containing the sperm (Rocha, Guerra, González, 2001). Generally, one of the male’s arms bears special modifications to perform the spermatophores’ transference and is called a hectocotylus (Rocha, Guerra, González, 2001). This structure is also present in Architeuthis (Knudsen, 1957; Roper, Boss, 1982; Aldrich, 1991), but spermatophore transfer seems to be a little unusual: spermatophores have been found lodged inside the arms of some females (Norman, Lu, 1997; Guerra et al., 2004; Hoving et al., 2004). Few other squids, of much smaller sizes than Architeuthis, show this behavior (Norman, Lu, 1997). In other cephalopods, the spermatophores are usually lodged in an exclusive receptacle inside the female’s mantle. Moreover, a female Architeuthis can apparently store spermatophores even when it is not yet sexually mature, which is perhaps a reproductive strategy, since an encounter between two giant squids might not be a very frequent occurrence in the ocean’s dark depths (Norman, Lu, 1997; Hoving et al., 2004). The ovaries found in some specimens have led to the estimate that Architeuthis can produce from one million to ten million eggs, each about 1.5mm in diameter, and it probably lays them in large gelatinous masses, like some other large oceanic squids (Roper, Boss, 1982; Boyle, 1986; Roeleveld, Lipinski, 1991; Hoving et al., 2004).

Some young specimens, a few centimeters in length, have been found throughout the world (Roper, Young, 1972; Lu, 1986). Considering the disparity in size between juveniles and adults and the fact that  Architeuthis  has a life cycle of about two to two and a half years, as is the rule in cephalopods (Rocha, Guerra, González, 2001), it is estimated that its growth rate is incredibly fast (Jackson, Lu, Dunning, 1991; Gauldie, West, Förch, 1994). Little else is known about the giant squid’s biology and it is believed that the rest of its physiological and behavioral features are similar to other squids.

Mesonychoteuthis: a new monster?

The largest Architeuthis ever recorded reaches 18m in length (some say 20m, but the tentacles extend after death, possibly leading to overestimated measures; Ellis, 2004), including the tentacles, and the mantle alone can reach up to 6m (Roper, Boss, 1982). However, the vast majority of specimens are much smaller (Clarke, 1966; Roper, Sweeney, Nauen, 1984; Roeleveld, Lipinski, 1991; Norman, 2000). The estimated weight of the largest specimens ranges from 400kg to 1t (Clarke, 1966; Roeleveld, Lipinski, 1991).

But even with such a great size, there is another species of squid that apparently wants to take the place of Architeuthis as the world’s largest invertebrate. The “colossal squid” (Mesonychoteuthis hamiltoni, family Cranchiidae), from the Antarctic Ocean, can apparently surpass Architeuthis in both length (by at least 1m) and weight (O’Shea, Bolstad, 2008). However, since not one single gigantic specimen has been recovered (the published accounts record only a maximum of 3m mantle length, 10m of total length and ~500kg; Roper, Jereb, 2010), this is simply an estimate made by extrapolation from young specimens or beaks. Moreover, such records have never been published in scientific journals; they are restricted to amateur websites and therefore cannot be confirmed. Thus, despite the greater amount of attention the media has given to Mesonychoteuthis, Architeuthis remains the sea monster par excellence.

Did the Kraken exist after all? Fossils revive idea of ancient sea monster that turned its prey’s bones into works of ART

• Kraken is a legendary tentacled monster that ate whales and even ships
• Markings found in 2011 gave rise to claims the Kraken may have existed
• Researchers have now found a fossil said to belong to an ancient squid
• They also found bones from the animal’s prey arranged in strange patterns
• Discoveries have revived claims about the mythical creature’s existence

By VICTORIA WOOLLASTON
UPDATED: 12:33 EDT, 1 November 2013

As the story goes, the mythical Kraken was an ancient tentacled sea monster that ate whales and devoured entire ships.

In 2011 researchers found the remains of a marine lizard that had been arranged in a strange pattern by what they claimed was a giant Kraken-style octopus playing with its food.

These claims were widely criticised, but now new fossils discovered by the same researchers add further weight to the theory that the Kraken not only existed, but that he used his prey’s bones as art.

Both claims have been made by Professor Mark McMenamin, a paleontologist at Mount Holyoke College in Massachusetts.

Professor McMenamin initially found the strange arrangement of vertebrae of the ichthyosaur Shonisaurus popularis in Berlin-Ichthyosaur State Park in Nevada.

The shonisaurus was a sea reptile that lived around 200 million to 250 million years ago. (BS)

His latest discoveries include the beak of what is believed to be an ancient cephalopod, as well as more bones arranged in unusual patterns and shapes.

This new arrangement of ichthyosaur fossils, which Professor McMenamin saw from a photo taken at the University of Nevada’s Museum of Natural History, show the bones laid out in the museum exactly how they had been found in the park.  

Next to the remains of the ichthyosaur was a ‘debris pile’ of scattered bones that were no longer in their correct order within the skeleton.

McMenamin told LiveScience: ‘When I saw that photograph, basically my eyeballs popped out.’

‘We think one plausible explanation of this is an attack on the icthyosaur by a much larger predator.’

Professor McMenamin argues that the way the bones were arranged could not have occurred naturally.

He reiterated his point at a meeting of geoscientists recently by saying there was ‘virtually zero’ chance the sea’s currents could have moved them into such an arrangement.

Professor McMenamin said that evidence of the Kraken, which would have been up to 30 metres long, comes from the vicious injures it inflicted on the giant marine reptile ichthyosaur, either by drowning the creature or snapping its neck.

The researcher claims he can tell this by examining the placement and sucker markings on bones, which seems to prove the creatures were drowned or had their necks snapped by a Kraken-like creature.

But Professor Professor McMenamin said: ‘I was aware that anytime there is controversy about depth, there is probably something interesting going on.’

‘Modern octopus will do this,’ Professor McMenamin said. ‘What if there was an ancient, very large sort of octopus, like the Kraken of mythology?’

‘I think that these things were captured by the Kraken and taken to the midden and the cephalopod would take them apart.’

Professor McMenamin explained the absence of any Kraken fossils with the fact that octopuses are soft-bodied creatures, but sceptics say his explanation is simply circumstantial evidence.