Gut contents of a giant squid Architeuthis dux (Cephalopoda: Oegopsida) from New Zealand waters
Gut contents of a giant squid Architeuthis dux (Cephalopoda:
Oegopsida) from New Zealand waters
By Dr. Steve O'Shea and Kat Bolstad (Tintenfisch)
Authored: May 2, 2003 / Posted: Jan. 2, 2006
Note: Steve and Kat welcome discussion in TONMO.com's Physiology & Biology forum.
K. S. BOLSTAD
Earth and Oceanic Sciences Research Institute
Auckland University of Technology
Private Bag 92 006
Auckland, New Zealand
Abstract New diet information for the giant squid
(Architeuthis dux) is presented based on the identification
of substantial identifiable prey items recovered
from the gut contents of a specimen caught in
New Zealand waters. Prey items are attributed to two
species of squid: Nototodarus sp. and Architeuthis dux. The incidence of Nototodarus in the stomach contents is not new, but the occurrence of Architeuthis remains is. Numerous fragments of an Architeuthis tentacular club, consisting of carpus, manus, and dactylus suckers, and the dactylic pouch, introduce the possibility of cannibalisma hitherto unreported behaviour in this genus. A synopsis of Architeuthis diet is presented and alternatives to cannibalism (such as autophagy) are evaluated.
Keywords cannibalism; Architeuthis; Nototodarus;
Mollusca; Cephalopoda; diet
No stomach caecum found amongst the more than
100 giant squid specimens (Architeuthis dux) previously
examined by the authors has contained more
than trace fish bone, scale, and unidentifiable squid
remains. However, a recent routine dissection of one
specimen revealed a stomach caecum distended with
food items. The present caecum is significant in three ways: the contents include many identifiable hardpart
remains; the inventory of known prey items is
increased; and, once identified, the prey composition
proves quite remarkable, without precedent in giant
Popular and scientific interest in Architeuthis has
been sparked by its reputed rarity and superlative
size. An increased incidence of capture in recent
years has also produced increasingly regular reports
of distribution, morphology, and data available postmortem
(such as diet).
The diet of Architeuthis has previously been described
(e.g., Toll & Hess 1981; Förch 1998; Lordan
et al. 1998; Ré et al. 1998) only from identification
of trace recognisable prey-item remains from gut
contents. Moreover, because of the fragmentary nature
of remains, attribution of prey items to genus
or species is usually provisional at best.
The most detailed reports of Architeuthis diet are
those of Förch (1998) and Lordan et al. (1998). Förch
reports 8 species of fish (7 of which were rattails
(Macrouridae) and 1 tentatively identified as orange
roughy (Hoplostethus atlanticus)), 2 types of crustacean
(chelae of 1 unidentified species, and 5 identified
species of copepod), and 2 species of squid
(Moroteuthis ingens and Nototodarus sloanii), in the
diet of New Zealand Architeuthis. Lordan et al.
(1998) report fish (Trachurus trachurus and
Micromesistius poutassou), crustaceans (Nephrops
norvegicus), bivalves (Modiolus phaseolinus),
cephalopods (Todarodes sagittatus, Eledone
cirrhosa (from statoliths) and tentatively Taonius
pavo), several ascidians, unidentified cestode and
nematode species, and small stones in the diet of
Architeuthis from Irish waters.
Toll & Hess (1981) report gut contents containing
unidentifiable cephalopod and fish remains;
Roper & Young (1972) similarly describe the gut of
one juvenile as containing much unidentifiable
amorphic material and a few small fish bones.
Pérez-Gándaras & Guerra report beaks of squids
Histioteuthis sp. and Ommastrephes caroli (1978),
and much-masticated, unidentifiable cephalopod
remains from adult specimens (1989). Similarly unidentifiable cephalopod remains (nine large squid
suckers of 1316 mm diameter, lacking sucker rings)
are reported from an adult by Zeidler & Gowlett-
The more unusual items that have been reported
from the stomachs of Architeuthis include pebbles
(Ré et al. 1998), the alga Fucus sp. (Kjennerud
1958), unidentified algae (Nordgård 1928; Aldrich
1991), and cestodes (Pippy & Aldrich 1969).
This dietary synopsis shows that deep-water
pelagic cephalopods and fish are prevalent in gut
contents of trawled Architeuthis, and that a surprising
diversity of shallow-water benthic or sessile organisms
may also appear in the guts of stranded
specimens. Whether adult Architeuthis is a benthopelagic
or truly pelagic species remains unconfirmed.
MATERIALS AND METHODS
The gut contents reported here were recovered from
the stomach caecum of an extensively damaged
(mantle only, of 1.6 m length) mature female
Architeuthis. No capture data accompanied the carcass.
Although unlocalised, this specimen is known
to have been caught in New Zealand waters by hoki
trawl, and was probably taken between 400 and
600 m depth off one of two locations: either West
Coast South Island, near to Hokitika Canyon, during
July and August, or Banks Peninsula, East Coast
South Island, between December and February.
Dissection revealed a caecum distended with
prey. The caecum was cut open, the frozen contents
photographed in situ, removed, defrosted in a bucket
and then fixed in 5% carbonate-buffered formalin
solution for 24 h. Fixed contents were then passed
over a 1-mm sieve, rinsed in fresh water, and transferred
to 40% carbonate-buffered isopropyl alcohol
for preservation. Alcohol-preserved samples were
subsequently passed over a 1-mm sieve, the contents
placed into trays and manually screened, and identifiable
prey remains extracted and sorted for subsequent
By process of elimination, prey items were identified
through comparison with a complete reference
collection of New Zealand squid species. The caecal
contents were critically compared with equivalent
structures from locally occurring squid species.
Stomach contents have been accessioned into the
biological collections of the Auckland University of
Technology (AUT), Earth & Oceanic Sciences
(EOS) Research Institute, accession # AUT G.22.
Collection acronyms used in text are: AUT, Auckland
University of Technology; NMNZ, Museum of
New Zealand; and NZOI, the National Institute of
Water & Atmospheric Research Ltd (NIWA), formerly
the New Zealand Oceanographic Institute.
Fig. 1 Distended Architeuthis stomach caecum, cut open, revealing defrosting prey remains in situ.
In addition to much unidentified cephalopod soft tissue,
the caecum contents (Fig. 1) comprised: the
posterior portion of a squid mantle, with gladius;
several separate gladius fragments; an intact buccal
bulb, with beaks, oesophagus and intestine; an anterior
portion of mantle with paired inverted-Tshaped
mantle-locking cartilages; one T-shaped
funnel-locking cartilage; one nearly intact arm of
length 107 mm, bearing many suckers with strong
distal- to disto-lateral dentition (8 long teeth) and
smooth proximal margins, and numerous shorter arm
fragments possessing suckers with comparable dentition.
All of these remains are attributed to a species
of Nototodarus. Two cephalopod eyes and 4
small, disassociated cephalopod eye lenses cannot
reliably be attributed to any taxon due to lack of systematic
characters, although they are probably also
referable to Nototodarus. The largest of these prey
remains (a near-intact portion of mantle, with paired
mantle-locking cartilages) was of 69 mm length,
33 mm relaxed diameter and 19 mm compressed
dimension (preserved measures).
Both smooth and dentate sucker rings were represented
amongst the gut contents. Smooth sucker
rings vary from ~2 to 4.5 mm diameter, while dentate
sucker rings, divisible into two groups, are < 1 mm in diameter (with 79 teeth distributed around the distal- and disto-lateral margins) and 513.5 mm diameter (with 1825 uniform small-sized teeth evenly distributed around the margin).
The larger suckers are of a type and size consistent with those found on the tentacle club of Architeuthis dux, and as they cannot be differentiated from voucher samples, we conclude that they are from the same species.
The caecal contents also included portions of a
tentacle club dactylus, with dactylic pocket and 10
intact, smooth-ringed suckers (Fig 57), in addition
to 23 unlocalised detached suckers with smooth
sucker rings, 3 with attached knobs. The latter are
attributable to either carpal or dactylic portions of a
tentacle club. Numerous tentacular sucker-ring fragments
(greatest fragment depth 8 mm) (Fig. 2, 3),
and 62 suckers with intact sucker rings, each with 1825 sharp-pointed, similarly sized projecting
teeth, with sucker and sucker ring greatest diameters
14.0 and 13.5 mm, respectively (Fig. 4) were also
Fig. 24 Architeuthis tentacle club manus sucker rings: 2, 3 medial sucker ring fragments; 4, marginal sucker ring, lateral profile; scale bar 10 mm. 57 Architeuthis tentacle-club carpal-sucker rings: 5, oral; 6, aboral; and 7, lateral perspectives; scale bar 5 mm. 810 Moroteuthis ingens arm sucker rings (NMNZ M.12952): 8, oral; 9, aboral; and 10, lateral perspectives; scale bar 3 mm. 11, 12: Cranchiid mid-arm sucker rings: 11, Teuthowenia pellucida (NMNZ M.160610); 12, Galiteuthis sp. (NZOI Stn Z8791); scale bar 1 mm.
Morphology of sucker rings
Several unrelated genera of squid have sucker rings
superficially similar to those described here. To support
the above attribution of smooth and larger dentate
sucker rings to Architeuthis, we here briefly
discuss sucker ring dentition in these other groups.
Post-paralarval onychoteuthid squid (Onychoteuthidae)
have smooth sucker rings. Three genera
are known from New Zealand waters (Notonykia,
Onychoteuthis, and Moroteuthis). The diameter of
the largest smooth sucker rings recovered from the
Architeuthis gut contents (4.5 mm) exceeds that of
locally occurring mature specimen of any Notonykia or Onychoteuthis species (1.8 mm [Female (F), mantle length (ML) 177 mm, NMNZ M.160475] and 1.9 mm [F, ML 137 mm, NMNZ M.74145], respectively).
The smooth sucker ring of Moroteuthis can be differentiated from that of Architeuthis by its eccentric ring aperture surrounded by a raised, narrow ridge, and a pronounced basal notch (Fig. 810).
The two cranchiid genera Teuthowenia and
Galiteuthis have sucker-ring dentition varying from
smooth to dentate (Voss 1980, 1985). The sucker
rings of New Zealand specimens of these genera
conform to those illustrated in Voss (locs cit.), although
some rings possess more developed dentition
than earlier reported (Fig. 11, 12). The eccentric ring
aperture of these taxa similarly serves to differentiate
them from those of Architeuthis.
The largest arm suckers on both Nototodarus sloanii and N. gouldi possess 79 pointed teeth distributed around the distal and disto-lateral margins (Dunning & Förch 1998), and voucher samples are
inseparable from the smaller suckers found in the Architeuthis gut contents.
The larger fragmented sucker rings bear only a
superficial resemblance to those of Todarodes
filippovae and T. angolensis, in that they are of large
size. The tentacle club medial manus sucker rings
of these two species are characterised by 713 and
1316 long-pointed teeth respectively (Dunning &
Wormuth 1998), while the equivalent suckers on the
related Ommastrephes bartrammi have a single
greatly enlarged tooth in each sucker ring quadrant
(Dunning 1998). The largest intact sucker rings attributed
to Architeuthis, recovered from the Architeuthis gut contents, have the 1825 similarly
sized teeth characterising this genus (Förch 1998).
The diet of Architeuthis
Although prey items must be well masticated by
cephalopods in order to pass through the narrow
oesophagus (maximum relaxed diameter 10 mm in
this specimen), one prey fragment recovered from
the stomach caecum was of 69 mm greatest dimension,
and 19 mm compressed dimension; many other
fragments were of comparable size. It appears that
Architeuthis dispatches prey by slicing it into large
pieces and passing them down the oesophagus. Nevertheless,
the dimensions of larger prey items are at
striking odds to the diameter of the relaxed oesophagus,
especially given that the oesophagus in
cephalopods passes directly through the brain.
As algae are reported only from the gut contents
of stranded specimens (Aldrich 1991, specimen # 10;
Nordgård 1928; Kjennerud 1958), we do not believe
them to be a natural component of Architeuthis diet.
Rather we suggest that a dying or struggling squid
might gnash its beak against algal-covered rocks
before stranding. Stones, reported from the stomachs
of both stranded and trawled specimens (Lordan et
al. 1998; Ré et al. 1998), must also be an unnatural
component in Architeuthis diet, and are likely to have
been secondarily ingested with prey items in in-situ captured
specimens, or ingested in a similar way to
algae in stranded specimens. The bivalve (Modiolus
phaseolinus), small ascidians, and unidentified
cestode and nematode species described from the
stomach caecum of Architeuthis (Lordan et al. 1998)
are both therein and here considered to be secondarily
ingested. The copepods reported from stomach caecal contents in three of Förch's specimens (numbers
2, 4, and 12) may also have been secondarily
ingested, although, given the regularity of occurrence
it is also possible that they actually parasitise the
Pelagic fish and cephalopod remains prevailed in
the gut contents of trawl-caught specimens (Pérez-
Gándaras & Guerra 1978, Toll & Hess 1981, Förch
1998, and the present report), and squid were also
present in the caecum of the floating specimen reported
by Zeidler & Gowlett-Holmes (1996). We
believe that pelagic squid and fish are the natural diet
of Architeuthis dux, and that it appears that it is a
pelagic species, rather than a bentho-pelagic one.
Most Architeuthis caught by trawl in New Zealand
waters have been associated with the hoki fishery,
trawled from between 400 and 600 m. To the
best of our knowledge, only one Architeuthis specimen
has ever been caught during deeper-water
(>800 m) trawling for orange roughy (Förch 1998),
and none of the 105 specimens received over the past
7 years, examined by the present authors, was taken
by orange roughy trawl. Surprisingly, then, a report
of orange roughy within gut contents of an
Architeuthis exists, although the identification was
tentative only (Förch 1998). Also unusual, given the
close association between the hoki fishery and the
incidence of Architeuthis capture in the water column,
is the absence of hoki in the diet of
Architeuthis. Instead, other macrourid fish and squid
dominate in the diet of regionally captured specimens.
Thus, it appears that Architeuthis probably
preys on the same food items as hoki (small fish,
prawns and squid), instead of on the hoki itself.
Accidental self-ingestion, autophagy or cannibalism
Because dactylic suckers, marginal and fragmented
manus suckers, and carpal suckers with knobs still
attached were recovered from the stomach contents
of this Architeuthis, we conclude that portions of an
entire tentacle club have been consumed, perhaps as
an aftermath of inter-architeuthid aggression or mating.
It is possible that the large unidentified suckers
reported by Zeidler & Gowlett-Holmes (1996) from
an Architeuthis stomach caecum are referable to Architeuthis, which would then constitute another
record of either cannibalism or autophagy in the
Regeneration of a damaged tentacle club has been
reported for Architeuthis (Aldrich & Aldrich 1968),
so the loss of the club has precedent and need not
be fatal. Aldrich later describes (1991, p. 474) a
beached specimen (# 15) as unique amongst those
he had encountered, in that it clearly showed evidence
of having engaged in battle with what was
apparently another cephalopod. He bases this conclusion
on evidence of sucker scars ranging from 2.7
to 4 mm in diameter on some arms, in addition to
the ends of incomplete arms being serrated in a manner
unlike that associated with beaching. Aldrich
(1991, p. 475) attributes this damage to combat with
another architeuthid. Our report of large tentacular
sucker rings of Architeuthis from a stomach caecum,
and that of Zeidler & Gowlett-Holmes (1996), of
large unidentifiable suckers recovered from a
conspecific stomach, equally support Aldrich's
contention that damage through combat with other
architeuthids is possible. Whether intentional or not,
ingestion of an entire Architeuthis tentacle club does
We thank the New Zealand Ministry of Fisheries
Scientific Observer Programme, and the many observers
who have saved Architeuthis specimens over the years.
We must also thank Bruce Marshall, Museum of New
Zealand, for his entertaining after-hour banter, for access
to large laboratory facilities that enabled these dissections
to proceed, and for editorial advice on an earlier
manuscript version; John Buckeridge, Auckland
University of Technology; Ellen Förch, University of
Auckland; Carolyn King, University of Waikato, and an
anonymous reviewer. Finally, we thank Maureen Lemire
and Discovery Communications Inc. (Discovery Channel,
Washington DC, USA), without whose continued support
this contribution would not have been possible.
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