Descriptions on Unidentified Species ofDibranchiate Cephalopods.
I. An Oegopsiden Squid belonging
to the Genus Architeuthis
By
EIJI lWAI(Laboratory of Fisheries Zoology, Faculty of Agriculture, Tokyo University)

In recent years some authors have reported on the Cephalopods
found in Japan and its adjacent waters. However since 1929, noattempt has yet been made to present a monograph of the species
found in these areas. Furthermore, as the preliminary records, treated
only the species of the coast and bay and a few pelagic members, it
is believed that many unidentified species still exist in the ocean.
The present specimens belonging to Oegopsids have not been hitherto
catalogued in Japan. In many respects, these specimens resemble thesquids of the genus Archteuthis and it is thought to be a young typeof A. japonica, but on the other hand striking differences were seen,
especially on the structure of the gladius and the horny ring found on
the arm suckers.
As mentioned by PFEFFER and ROBSON, it is very difficult to determine the species in Architeuthidae, because of the following reasons.
(1) Only a few specimens belonging to the family were obtained
up to the present.
(2) Almost all the squids described were those found, either partially digested or destroyed in the digestive canal of the whale,or those found stranded in the storm.
(3) Most of the reports are limited to the description of giant,mature squids.
(4) In some of the species, sexual dimorphism etc. are seen.
From the above reasons, PFEFFER stated that the fifteen known
species of Architeuthidae could better be divided into 3 groups, i. e.
Nordpazijische, Nordatlantische und Siidliche Formen, and discussed fromthe viewpoint of geological variations. In the North Pacific, only asingle species was reported by PFEFFER and others.
The two specimens described here were found in the digestive canal,
perhaps in the stomach of the sperm whale, captured near the Bonin
Islands in the summer of 1952. In this paper the author has tried todescribe the specimens, by discussing their resemblances and differenceswith A. japonica and other Oegopsids.

140

E. !WAIThe author has much pleasure in acknowledging his indebtedness
to Dr. M. NISHIWAKI, who kindly supplied the specimens, to Prof. M.
ISHIKAWA and Y. SUYEHIRO for their invaluable advice and guidance,
and to Assoc. Prof. T. HIBIYA for his kind assistance in reading theproofs of this paper.
General Observations
Mantle: Body rather small, subfusiform as seen in general squids
and its length reaches 3! to 4 times the maximum breadth taken at theanterior orifice. From the opening the mantle gradually tapers posteriorly, forming a straight line at each lateral margins to the origin of thefin, whence it becomes much narrower and continues to the extremity asa slender spit-like process, but not conical as seen in Ommastrephes(plates I and II). According to SASAKI's description on A1·chiteuthis
japonica, the maximun breadth of the mantle is at about one-third of
the length from the anterior end; however, PFEFFER described that itis broadest at the orifice.
Actual measurements of the specimens after preservation in formalin
are given in table 1.
The mantle is rather thick, fleshy and smooth; on all its surface,
Table 1.

Morphological measurements of the two specimens

Body portion
Mantle:Head:dorsal length
maximum breadthdorsal length
breadthheight

Arms

No. 2

92
26
24
25
17

104
26
26
26
18

(mm)
(

")

( " )
( " )
(

" )

"
" )
( " )
( " )
)

length of the firstthe second
the third
the fourth
formulalengthFinbreadthlength/breadth
Fin length/Body length((

Tentacle: length
club

(mm)

* most elongated

No. 1

left
53
65
63
58

right
54
60
60
56

2~3>4>1

52
61
85
50

( % )

" )
" )

!

44
64
69
48

"
( "

(

left
54
61
61
56

2~3>4>1

(

(

1

right
56
66
65
58

left
105
23

right
*f66
23

left
121
23

right
119
22

Descriptions on Unidentified Species of Dibranchiate Cephalopods

141

devoided of any kinds of tubercles or folds. Purple-coloured chromatophores are as common as in any other squids. No luminous organs
are present. Antero-ventral margin of the mantle is slightly concaved
between the faint projections of the either sides of the funnel base ;dorsally the margin forms an obtuse angle of about 170° at the middle,
while in SASAKI's description it is said to form an angle of 120°.
Fin: Fin is typically terminal, and is about half the length of the
mantle; its breadth is decidedly longer than its length. The shape ofthe fin is very characteristic. It is more or less heart-shaped, but withan acute posterior extremity and quite resembling that of A. japonica.
Anteriorly its origin is somewhat auriculated on both sides of the body,and the antero-lateral margin is clearly convex, the convexity being
continued to the round ear-shaped lateral angle too. The post-lateral
margin is nearly straight except at the projected region.
Head: Head is roughly cubical in shape; the ventral surface isflat, whereas the dorsal and lateral sides are rounded. Breadth of thehead is a little narrower than the mantle and its length is about onefourth of the body length. The posterior end of the head is obviously
marked off from the neck by a distinct constriction at both funnelbases. Eyeballs comparatively large, and the perforated openings arealso wide; at the interspaces between the third arm and the tentacle,
is situated a very distinct sinus, the dorsal wall of which is more orless thickened (fig. 11). According to MITSUKURI and IKEDA, the "lacrymal gland" of A. japonica is much smaller than in these specimens.
Funnel excavation is deep, and is limited by a clear-cut horse-shoe
shaped fold, which widens into a broad thick membrane holding thefunnel laterally at the posterior region. Olfactory crest is not conspicuous; this organ may be composed of more than 10 fold-like streaks
running longitudinally at the lateral side of the head.
Nuckal cartilage: Nuckal cartilage spatulate, but on its structure
a little difference was observed when compared with that of A. japonica
given in SASAKI's description.
The anterior one-third of the nuckal cartilage is quadrangular inshape with its corners rounded, and its length is twice the breadth.
The posterior end narrows gradually and finally ends in a spoon-shaped
expansion. There are two median parallel ridges gently raised fromthe surface, which gradually flattens towards the posterior end. In
the crest between these ridges a shallow groove was observed. The
nuckal cartilage is 1.3 cm long and the maximum breadth is 0.4 cm.
Funnel: Funnel is relatively large, and especially expanded at thebase; its distal end being somewhat tubular, and a little recurved
ventrally. The funnel organ consists of dorsal and ventral pads. Among142

E. !WAI

these, the dorsal pads are remarkably distinct and are V-shaped. They
are placed beyond the anus and form an apex in the central region offunnel. The ventral pads were not clearly seen in these samples. The
funnel valve is wide, tongue-like and situated inside the siphon, a little
distance from the orifice, sticking to the dorsal wall.
Articulations: The whole appearance of the funnel cartilage isslender as a bamboo-leaf, as shown in fig. 9, with a deep, broad grooveat a little dorsal to the median line; the measurements are 1.3 cm inlength and 0.3 cm in breadth. The ventral side of the crest is faintly
elevated. Anterior end of the cartilage is more or less sharp pointed
and a little recurved to the outside, but the posterior end of the cartilage is blunt and turned to the inside. Mantle cartilage almost thesame with that of other species in Architeuthidae (fig. 10) i its length
nearly one and half times that of the funnel cartilage and is linear andkeeled. Its posterior part is a little broad and gently decreased inheight posteriorly.
Arms: Arms are more or less equal in length, shorter than the
mantle and its length order is 2 ·. 3 4 1; while in A . .faponica its
length exceeds that of the head and body length, and its order is
4 ·. 3>2>1. All arms roughly quadrangular shaped in cross-section,
tapering towards the tip evenly. At its lateral sides, slightly compressed, but clearly round on the aboral surface. The web only develops
on the outer sides of the ventral arms; the dorsal side much broader
than the ventral and widens towards the base. According to MITSUKURI
and IKEDA, webs are not seen on all arms. Protective membranes
which are well-developed in A . .faponica are not recognized in these
specimens, this may be the result of digestion.
Arm suckers: Arm suckers are large relative to the length ofarms. They are subspherical in shape and arranged in two rows throughout.
On the whole, the suckers on the ventral arms are decidedly smallest, the diameter being about half that of the suckers of the otherarms. The suckers, excepting those on the ventral arms are almostof the same size at particular levels. It may be said that the suckers
are the largest on the two second arms, and consist of about 40 seriesof suckers. The proximal 20 series are recognized with the naked eyes
and the rest are minute, in the distal region. The suckers on thesearms become larger gradually and the largest on the 7th or 8th series,
and then diminish in size distally. The number and arrangement of
the suckers on the other arms are about the same with that of thesecond arms.
A remarkable difference with that of A . .faponica, is that, on the
horny ring of each sucker in A. japonica a row of teeth are present.

> >Descriptions on Unidentified Species of Dibranchiate Cephalopods

143

However, in these samples teeth are completely absent.
Tentacles: The structure of the tentacle is most characteristic andis not seen in other Oegopsids. The length of the tentacle reaches
to that of the head and body, but much shorted than the tentacle of
A. japonica. The width is a little narrower than the arms. The club isfeebly expanded and somewhat lanceolate and sharp pointed at its distal
extremity, protected by a flap of thin membrane at the edge. The length of the clubis about 1/5 to 2/9 of the tentacle. Regarding
the structure of the tentacle, the most striking characters are the arrangement andstructure of suckers on the hand portion(fig. 5 and text-fig. 1).
Tentacular suckers: The suckers arearranged in 5 rows, and the middle ones
are much larger than the lateral ones. Of
the middle ones, the centro-basal 3 suckers
are extraordinarily large, measuring up to
2 mm in dia. These suckers are fiat typicallybasin-shaped, and each sessiled by a very
short, but thick stalk. On the margins of
the horny ring of the largest sucker, 26
teeth triangular in form are situated atregular intervals and it is all projected outside from the chitinous margin. Of theseteeth, the ventral one is larger than thedorsal one.
·.©>·.oc~. . . . .. .
i.
~~
Next in size to the horny ring in the
middle row, the order is as second, first,
fourth and fifth row respectively. i.e. thesize of the horny rings becomes smaller
gradually in the order of the rows shown
above. The teeth too, found on these horny
rings become proportionately smaller in relation to its horny ring. From the above
description it is apparent that the suckersof the rows which are ventral most (i.e. the
5th row) are the smallest in size.
Further to this, the author observed that
Text-fig. 1. The arrangethese suckers of the fifth row, towards the ment of variable suckers on eachdistal end, lose their proper positions and region of the tentacular club.
insert themselves more in the distal region x5.

., i@I. . e· .· .
;~:

l>

•

• • : •_..;·

ri·::d ::~

.

144

E. !WAIin the company of the suckers of the fourth row. So the dispositionof the suckers on the boarder line, between the hand region and the
distal region, is {Ilore or less disturbed, and it becomes a question todetermine to which region the suckers belong decisively. In respect
to this character, these specimen agree with the squids of the genus
Meleagloteuthis. In A. japonica, however, the hand of the tentacularclub has suckers in 4 oblique rows, of which the suckers of the two
median rows are much larger than those of the marginal rows. Nevertheless, they are all basin formed.
The suckers known as the fixing apparatus on the carpal organ(carpal region) are eleven in number. They have smooth horny ringsand pads are found in the interspaces of these suckers. The suckers
decrease in size proximally.
The distal region of the tentacular club is composed of about 40
series of minute suckers arranged in 4 or 5 rows. Its horny rings aretoothless.
An interesting fact is that along the two-thirds of the linear groove,running in the median line inside the tentacular stem from the end of
the carpal organ to the base are situated 14 suckers and pads, which
are nearly equal in size to the distal suckers, with smooth horny rings.
Gladius: Gladius thin, feather-like as shown in fig. 8; the maximum breadth is a little shorter than one-eighth the length of the sample.
Rhachis carinated on the back, but the keel does not appear throughthe mantle at its dorsal median line. The vane attached to the posterior
seven-eighth of the rhachis, is much broad, its widest part being at a
distance of one-fourth the length of the gladius from the anterior end.
From here it becomes slender gradually towards the posterior end.
Secondary development can be seen out of the lateral vanes. The tipof the given specimens being damaged, the structure of the posterior
part was not observable. However the author doubts, whether the end
cone distinctly recognized in A. japonica is also found in these specimen. Ribs are firm and are dark amber coloured in formalin solution.
Discussion

As stated above, these specimen have similarities and agree very
well with the descriptions of A. J·aponica in many points, i.e. (1) in theexternal appearance of the mantle and the fin, (2) the structure of thearticulating cartilage, (3) in the arrangement of suckers on all arms,(4) the basemental structure of the tentacular club and its stem, and(5) the fixing apparatus. But on the other hand, many differenceswere also seen and are summalized in table 2.

Descriptions on Unidentified Species of Dibranchiate Cephalopods

145

Table 2.
A. japonica (adult)

The specimens

Hand region of ten·tacular clubconsists of 4 rows of suckers

consists of 5 rows of suckers
and 3 ones of the central
row much larger than theothersArmsmuch longer than body lengthand arm formula; 4"73>2>1

not longer than body lengthand arm formula; 2"73>4>1

Horny rings of arm
suckers

all with dentation

not any teeth

Fin

decidedly long er than breadth

length shorter than breadth

Gladiusforms an end·cone at theposterior extremity

not formed

In addition to this, some of the results, established by the comparison of these samples with A. japonica seem also to be applicable toother species of this genus.
It may be thought that these different characters, especially of thefin, arm order, and the arrangement of the tentacular suckers, could
have originated as a result of morphological variations during growthof the same species. These samples were at first believed to be ayoung type of A. japonica, with resemblances to locality.
However, will it be possible to explane for the formation of teethon the whole margins of the horny ring on all arm suckers, and forthe fundamental difference on the structure of the gladius ? In theserespects, the author hestiated to draw a conclusion.
Still more, comparing these specimens with other Oegopsids, results
obtained were as follows.
These specimens differ:
From Branchioteuthidae in:(1) The structure of the tentacular club.
(2) The presence or absence of the fixing apparatus.
(3) The teeth of the horny ring on the arm suckers.
(4) The form of the gladius.
From Histioteuthidae in:(1) The mantle structure and (2) the body form.
From Enoploteuthidae and Onychoteuthidae in:(1) The horny ring of the arm suckers and (2) the surface
structure of the mantle.
And from other families, differences are clearly recognized at a
glance. It is very difficult to conclude to which species in Architeuthis
these specimens belong at present and regards on this point, will be
discussed and reported in some future.

146

E.~IWAI

References
BERRY, S. S.:
A Catalogue of Japanese Cephalopoda.
Proc. Acad. Nat. Sci. 1912
Philadelphia, 380-444 (1912).
MITSUKURI, K. and IKEDA, S.: Note on a giant Cephalopoda. Zoo!. Mag. Tokyo 7, 39-50(1895).
PI•'EFFER, G.: Die Cephalopoden der Plankton-Expedition. Ergebnis. Plank. Exp. Humboldt., II. F. a, 1-815 (1912).
RAE, B. B.: Descriptions of a Giant Squid stranded near Aberdeen. Proc. Malac. Soc.
London 28, 163-167 (1950).
ROBSON, G. C.: On Architeuthis clarkei, a new Species of gigant Squids, with Obser·
vations on Genus. Proc. Zoo!. Soc. London 1933 (3), 681-697 (1933).
SASAKI, M.: Notes on Oegopsida Cephalopodes found in Japan. Annot. Zoo!. Jap., 9,89-120 (1916).
- - - - . A Monograph of the Dibranchiate Cephalopods of the Japanese and adjacent
Waters. }our. Coll. Agric. Hokkaido Imp. Univ., 20. Suppl. Numb., 1-357 (1929).

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