Giant and Colossal Squid Fact Sheet
Giant and Colossal Squid Fact Sheet
By Dr. Steve O'Shea and Dr. Kat Bolstad -- Last updated: April 6, 2008
Fig. 1. Mid-arm hooks and sucker rings on
Basic squid morphology and terminology.
Steve and Kat are members of the TONMO staff. You can communicate with them both in our Cephalopod Science forums.
INTRODUCTION TO FACT SHEETS
To ensure accurate reporting of these squid species, the following brief notes
have been prepared. First, a simplified account of squid morphology (Fig. 1),
where we detail the differences between squid and octopus; second, an introduction to size and how it has been measured (and misreported); and third,
an introduction to the two species that you will be hearing a lot about: Colossal Squid (Mesonychoteuthis hamiltoni) and Giant Squid (Architeuthis dux).
We already have online an introduction to octopus and squid anatomy in our article, Deep-Sea Cephalopods: An Introduction and Overview, so will not unnecessarily duplicate that information. For the sake of this article we will focus on the absolute basics of cephalopod anatomy, and some frequently cited measures, particularly Mantle Length (ML), Standard
Length (SL), and Total length (TL).
1. Introduction to squid anatomy: Basic squid and octopus facts
A basic squid has:
8 arms and two tentacles, each endowed with hooks and/or suckers and sucker rings (Figs 1—4)
A basic octopus has:
8 arms endowed with one or two rows of suckers (but never hooks or sucker rings); they have no tentacles (Fig. 5)
Some squid naturally lose the tentacles in post-larval stages, so that the
adult possesses 8 arms only; some squid can have more than 2 fins. Some
octopuses (9 species in New Zealand waters) possess two well-developed fins;
these 9 species also have a well-developed pen (like a cuttlebone) in their mantle, and are considered rather primitive, commonly referred to as 'Dumbo Octopuses'.
The only universal distinction
between a squid and an octopus is that the suckers of squid are armed with
hooks or sucker rings (or a combination of the two), while octopus have simple
suckers without secondary armature (Fig. 5). It is the squids' hooks and rings
that have enthralled the public most. You will find additional information on
squid and octopus in our Guide to Frequently Used Characters, Character States and Measures.
With this basic introduction to
octopus and squid anatomy aside, we can move on to the real purpose of this
fact sheet. The Giant and Colossal Squid Fact Sheet.
Fig. 2: tentacle club of Architeuthis,
showing circular-saw-like sucker rings.
Fig. 3: tentacle club of Mesonychoteuthis,
with swiveling hooks.
Fig. 4: Profile of Mesonychoteuthis tentacle club, showing hooks.
Fig. 5: Suckers of Haliphron atlanticus, the giant gelatinous octopus (the world's largest species of octopus), lacking secondary armature.
What we know about Giant Squid (Architeuthis dux) (Figs 6–8):
Quite a lot – check out these
Age and growth
Buoyancy and feeding
Distribution around New Zealand
There is also a tremendous body of
scientific literature available for this species.
The juvenile was caught and filmed
live by Dr Steve O'Shea in 2001; unfortunately all died before they could be grown in captivity. The adult was photographed live off Japan in a series of stills by Dr Tsunemi Kubodera in September 2004; the adult was subsequently filmed live at the surface off Japan in December 2006, also by Dr Tsunemi Kubodera.
Architeuthis is frequently
misreported to attain a total length of 20 metres (~65 feet). However, the
largest specimen known washed ashore on a New Zealand beach, Lyall Bay (Wellington) in the winter of 1887. It was a female and "in all ways smaller than any of the hitherto-described New Zealand species", according to Kirk (1887), the gentleman who described this very specimen. Apparently it measured 55 feet 2 inches in total length (16.8m), but this simply cannot be correct, and this length almost certainly is a product of imagination or lengthening (stretching like rubber bands) of the very slight tentacular arms, as it mantle was only 71 inches long (1.8m). We know that it was not measured with a conventional tape, but was paced, as Kirk says so in his publication. A comparable-sized
female (ML 1.8m) measured post mortem and relaxed (by modern standards) today
would have a total length of ~32 feet (9.8m).
Mantle length (as opposed to total
length) is the standard measure in cephalopods. Of more than 130 Architeuthis specimens that the authors have examined, none has attained a mantle exceeding 2.25m (7.4 feet), or total length of 13m (42 feet).
Standard Length (SL) is the length
of a squid excluding the tentacles; in Architeuthis this measure very
rarely exceeds 5m. The rest of the animal's length, to a total length of 13m, is made up of the two long tentacles. Of more than 130 specimens that we have examined, none has exceeded these figures (Fig. 7).
Architeuthis beaks recovered from the
stomachs of sperm whales are smaller than or of comparable size to Architeuthis
beaks recovered from specimens trawled in New Zealand waters. Therefore, since
we believe sperm whales capable of catching even the largest giant squid, no evidence exists for recognising larger specimens than those that are currently known. Moreover, it is most likely that a single species, Architeuthis dux, exists worldwide, so 'larger species' of Architeuthis do not occur. Accordingly, to perpetuate myths of Architeuthis to 20 metre lengths (60 feet) and weights of up to 1000kg (a ton, or 2205lbs) is a disservice to science.
Mesonychoteuthis hamiltoni Robson, 1925 (Figs 1, 3, 4, 8, 9) Vernacular: Colossal
Squid; Giant Cranch Squid
On April 1, 2003 the popular press
was first alerted to the Colossal Squid, a.k.a. Mesonychoteuthis hamiltoni, although this species has been known to the scientific community since 1925, after it was described from two arm (brachial) crowns recovered from sperm whale stomachs (Robson 1925). We have located 11 further reports in which adult and subadult specimens have been described, and are aware of at least 7 further, similarly sized specimens that have yet to be reported. Juveniles of this species are not uncommon from surface waters to ~1000m depth.
The relatively short arms are endowed with a combination of hooks and suckers.
Otherwise this species doesn't really differ from any other cranchiid squid (Family Cranchiidae) in any remarkable manner, with the exception of its size.
The tentacle club, the expanded distal portion of the tentacle, is endowed with two rows of swivelling hooks (Figs 3, 4)
The beaks are the largest known of any squid (Figs 9, 10), exceeding those of Architeuthis in size and robustness
The eyes are probably the largest in the animal kingdom (even larger than those of Architeuthis)
The 'colossal' cranchiid squid Mesonychoteuthis hamiltoni is thought to be the largest of all Recent cephalopods. However, due to lack of material, and the fragmentary, partially digested or juvenile nature of almost every previously reported specimen, the biology and morphology of this species have remained poorly known.
Mesonychoteuthis hamiltoni is actually a quite-well studied species, with 11 specimens above juvenile size (arbitrarily taken as 90mm ML), including the two Syntypes, having been reported since 1925. McSweeny (1970) provides a complete description of the juvenile of this species. Klumov & Yukhov (1975, in Russian) describe several (possibly 5) specimens of ML 390–1550mm, and offer a detailed account of hook, radular, beak, gladius, photophore, arm, tentacular club, and spermatophore morphology. Voss (1980) describes a subadult female of ML 1.25m
and refers to ‘several large partial specimens' (brachial crowns) in collections of the United States National Museum, Smithsonian Institution. Rodhouse & Clarke (1985) report a further specimen, ML 1.05m, trawled at a depth of 2000-2200m. Finally, Lu & Williams (1994) briefly report two specimens (one male, 107mm ML, and one female, 118mm ML), from a midwater trawl in Prydz Bay, Antarctica. Several additional authors have touched on various aspects of the species' anatomy in other papers: Clarke (1962, 1980) describes and illustrates the beaks; Engeser & Clarke (1988) illustrate both arm and tentacular hooks; Young (1984) illustrates the statocyst; Herring et al. (2002) further describe the ocular photophores on the specimen reported by Rodhouse & Clarke (1985); and Xavier et al. (2003) report a single tentacle from M. hamiltoni recovered from a longline hook off South Georgia. Clarke (1966) refers to 'several complete specimens... collected from sperm whale stomachs in the Antarctic,' the largest of which had a ML of 2–2.25m, but it is not certain whether either of these specimens has been reported on or described further; the location of these specimens also is unknown.
Fig. 8: size comparison of Architeuthis and Mesonychoteuthis, based on accounts of maximum mantle length.
Further information has been gleaned from gut-content analysis of its predators, primarily sperm whales, wandering albatross, Patagonian and Antarctic Toothfish, and sleeper sharks. Even the first two described specimens of this species were recovered from the stomach of a sperm whale, although they are undetermined sex and are in poor condition.
Based on all sources, M. hamiltoni appears to be abundant in the Antarctic, and important in the diets of apex predators such as the sperm whale (76–77% of male whale diet (Clarke 1980, Rodhouse & Clarke 1985) and sleeper shark (52% by weight (Cherel & Duhamel 2004).
This species attains the greatest weight, but not necessarily greatest length of all squid species, and is known to attain a mantle length of at least 2.5m. Should accounts relayed to us be correct, the largest specimen that we will be defrosting at the end of April 2008 has a ML of 4m.
In the absence of numerous specimens taken from a variety of localities (with the exception of paralarvae (relatively tiny juveniles), known to have circumpolar Antarctic distribution (Voss 1980, Nesis 2003)), the life history and
zoogeography of M. hamiltoni must be inferred from more indirect sources. Although predators are useful in providing some information on large
squid species (perhaps our best source at present), deriving information on the
geographic distribution of prey species solely from gut content specimens is
risky (O'Shea 2007). Certain predators of M. hamiltoni are known to
undertake extensive migrations; wandering albatross range in excess of 1200 km from their nest sites on average in search of prey (Jouventin & Weimerskirch 1990) and sperm whales are also known to migrate thousands of kilometres.
Fig. 9: size comparison of mature Mesonychoteuthis (left) and |
Architeuthis (right) beaks recovered from sperm whale stomachs.
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