DUODENAL PORTION OF THE HEPATO-PANCREATIC
DUCT OF THE BOUTU, !NIA GEOFFRENSIS

KENJI KITO AND FUSAO YAMASAKI*ABSTRACT

The duodenal portion of the hepato-pancreatic duct of the Boutu,
Inia geojfrensis (body length 204 cm, female), was examined macroscopicallyand light microscopically. Passing through the muscle layer of theduodenum, the hepato-pancreatic duct ran intramurally, and formed theduodenal pouch, and opened into the lumen of the duodenum proper.
The intramural cystic gland, mucous in nature, was located in the relatively
thick submucosa of the duodenum, in which scattered bundles of muscle
fibers were arranged in a layered appearance. A tentative comparison forsome features of the duodenal portion of the hepato-pancreatic ductsuggests that the fresh water dolphins may be a phylogenetically peculiar
group in toothed whales.

INTRODUCTION

The hepato-pancreatic duct of the cetacean bile-passage generally dilates andforms a well-developed glandular structure in the duodenal wall (Kamiya,1962; Yablokov, Bel'kovich and Borisov, 1972). This glandular structure,termed as the intramural cystic gland, supposedly plays a role in the storageand excretion of the gall, compensating to some extent for the absence of thegallbladder (Kamiya, 1962). According to the above two works, the intramural
cystic gland is located in the submucosa of the duodenum in whalebone
whales and the sperm whale, and in the muscle layer of the duodenum in
toothed whales except in the case of the sperm whale. It is, therefore,suggested that the location of the intramural cystic gland in the duodenal wallis an important character to consider the phylogeny of the cetaceans.
Some studies on the fresh water dolphins also have mentioned thehepato-pancreatic duct passing through the duodenal wall: Takahashi andYamasaki (1972) and Yamasaki, Takahashi and Kamiya (1972) on Platanista
gangetica; Yamasaki, Takahashi and Kamiya (1975) and Takahashi, Yamasakiand Kamiya (1976) on Pontoporia blainvillei; Zhou and Li (1981) on Lipotes
vexillifer; Zhou, Li and Pilleri (1982) on Inia boliviensis; and Yamasaki and Kito(1984) on Inia geoffrensis. In order to discuss the fresh water dolphins, regarding the features of the bile-passage, it is necessary that these features of the*Department of Biology, Sapporo Medical College, Sapporo 060, Japan
Sci. Rep. Whales Res. Inst.,No. 36, 1985, 89-95

90KITOANDYAMASAKIIni
αandLipote
sbedescribedatl
easta
sdetailedlyastha
tofthePlαtαnistaand
Pontopor
ia.Thepresen
tpaper,asthethir
dre
por
tonth
emorphologicals
tudyofthedigestiv
etractofh臼 geoffrens
is,describe
sde
tailedlyt
hehepato・pan‑creaticductint
heduodenumandp
rov
ide
ssomefundamentalknowledget
ocons
i
dert
hephylogeneticrelat
io
ns
hi
poft
hefreshwaterdolphinsinthec
etaceans.
句MATERIALANDMETHODS
Aspec
imenoft
heBoutu(Amazoniandolphin),Iηiageoffreηsis(bodylength204cm,female)wasprovidedf
ort
hi
sstud
ybyKamogawaSeaWorld,Chiba,Japan,afterdeath from anunident
ifie
ddisease. Theduodenumwi
t
ht
he
hepat
o・pancreaticducttakenfrom theabdominalc
av
ity waspreserv
edin
10% formal
ins
olut
io
nandt
r
ans
por
te
dt
oourl
abora
tory
.Thebile‑
passageoutsideoftheduodenumha
sbeenexcludedfromthemate
r
i
alt
r
ans
po
r
t
ed,sot
hatt
h
ep
r
e
se
ntobser
v
a
t
ioni
sr
est
r
ict
e
dt
oonl
yt
h
ehepato‑pan
c
r
e
at
i
cduct
lo
c
at
e
dint
h
eduodenum.A
f
t
e
rm
ac
r
o
s
c
o
p
i
c
alob
se
r
v
at
i
on,t
h
em
ate
r
i
alwas
embedde
dinc
e
llo
i
din,sectioned,and stainedw
ith hematoxylin‑
eos
i
nfor
li
ghtm
i
cr
oscop
y.

F
i
gsI
aand I
b.Photomicrogiaphso
ft
hel
ong
i
tud
i
n
alse
ct
i
onoft
h
eduodenal
por
t
i
o
noft
heh
e
p
a
to・p
an
cr
e
at
i
cduc
twhic
hi
sl
oc
at
e
dint
h
eduodena
l
w
al
loft
he
I
n
i
ag
eo
j
fr
en
s
i
s.Them
idp
ar
toft
hedu
ctwass
e
ct
ion
e
dtr
an
sv
er
sel
yandshowni
nFig.2.F
igsl
aand lbs
howt
hef
inalone
‑
fou
rt
handt
hei
nit
ia
lpar
toft
heduodenalpouch,res
pect
iv
el
y.Thepouchexsistssubmucosallyintheduodena
lwal
l.DI‑
duodenallu
men;Opトlumeno
fduodenalpouch;Tm‑tun
ic
amu
scu
lar
i
s
oft
heduodenum;Hp‑hepato・pancreaticduct;Pld‑plicalongitudinali
sduodeni;
anarrowshowst
heori
ficeoftheduodenalpouch.H‑Estain.x 8.
Sci.Rep. Wha
lesRes.Inst.
,No.3
6,198
5

DUODENAL POUCH OFTHEBOUT U

91

OBSERVATIONtaenumpropera
eduodhloftlaewhdteretcductenitaer
cno・paThehepatalt
is.Thedb)
aandlslgi
F
tramuraly(nwardsi
ananaleandrlepanget
herstarslumenandformedt
largediheduodenalwalennt
eductihsoftht
r
uof
e‑
er
ht
dl
uo,whichc
iisduoden
nal
idu
t
ongi
alc
il
ep
hh;t
aledduodenalpouc
c‑o
hest
e
c
a
fr
u
sr
en
n
i
e
ht
no,
edi
w
cm
6.
0dn
a
g
nol
cm
5.
1t
u
ob
a
s
i,
n
e
e
syl
t
c
n
it
s
i
d
bee
hot
t
n
c duct opened iit
aer
co・pan. The hepat
he duodenum properof thehe midpan of t
ion of ttce
esserv
se uanhaph of t
r
gor
ci
mot
. 2.A pho
ig
F
ner
nki
c
hi
het
soft
t
si
ons
numc
heduode
roft
e
ya
el
lc
emus
.Th
hc
uo
enalp
duod
a
so
ubmuc
asel
kt
ic
h
het
nt
diet
aco
sl
hi
.Theduodenalpouc
srone
et
u
ino
h
andt
heaoftsoc.Themu)worraen(eanbes
scr
eb
i
lefc
moothmushsomescnwhi
ieerarrmohefandsoftenandgl
llum
na
ode
edu
h
toftahhantrtekic
hsthi
uc
po
enof
lum‑
len;Dp
llum
dena
duo
‑.DIer
ut
nna
usi
or
ees
tsar
ert
t
ael
h
sandt
mucou
ubmucosa;
aselt
eduodenum;Ts‑
hsoft
ri
aul
c
amus
cniut
lpouch;T m‑
ane
duod.
6.X 1
niat
Es.H‑
er
ut
curt
lsaic
ifit
ar
‑
*.,
tsnsR目 . I
e. Whal
J/.ReicS,1985
6.3oN92

KITO AND YAMASAKI

duodenal lumen through the slit-like orifice with 2 mm in length (Fig. la),which was located about 9 cm away from the commencement of theduodenum proper. The duodenal papilla was indistinct and no peculiar structure was found around the orifice.
Microscopically, the hepato-pancreatic duct ran in the submucosa of theduodenum after passing through the muscle layer of the duodenum (Fig. lb).
There were no longitudinal or transverse folds and also no villi on the innersurface of the duodenal pouch; luminal epithelium was seen to be worn-off.
As shown in Figs 1and2, the lamina propria mucosae of the hepato-pancreatic
duct was 0.3-1.2 mm thick, and was occupied with well-developed tubuloalveolar glands. This glandular structure, the intramural cystic gland, wasmucous in nature and apparently differed from that of the duodenum
proper, mostly consisting of serous glands. Goblet cells were not foundamong the epithelial cells of the intramural cystic glands and lymphatic
nodules were also absent in the lamina propria mucosae of the hepato-pancreatic duct. No sphincteric smooth muscles could be seen either at theproximal or distal portion of the duodenal pouch, though the outer longitudinal muscles of the duodenal wall irregularly and intermittently extended
to the submucosa around the proximal portion of the intramural cystic gland.
Scattered bundles of smooth muscle fibers gave a layered appearance near
the middle of the submucosa between both the mucosa of the duodenum andthe hepato-pancreatic duct.
DISCUSSION

Table 1 summarizes the macro- and microscopical features on the duodenal
portion of the hepato-pancreatic duct of the fresh water dolphins, based uponthe following studies, Takahashi and Yamasaki (1972) and Yamasaki et al.
(1972) on Platanista gangetica; Yamasaki et. al. (1975) and Takahashi et al.
(1976) on Pontoporia blainvillei; Zhou and Li (1981) on Lipotes vexillifer; andZhou et al. (1982) on Inia boliviensis; Yamasaki and Kito (1984) and the present study on Inia geoffrensis. This table is unfortunately incomplete because
all information on the features are not given from the above studies. Therefore, it is presently possible to compare the fresh water dolphins in only a few
characters which are clearly described.
The hepato-pancreatic duct of Inia is similar to that of Pontoporia andPlatanista in running analwards within the submucosa of the duodenum andin entering the lumen of the duodenum proper through the orifice not surrounded by any peculiar prominences. While, the hepato-pancreatic duct ofLipotes runs within the circular muscle layer of the duodenum and enters thelumen of the duodenal ampulla through the orifice surrounded by a lip-likeprominence (Zhou and Li, 1981). The intramural cystic gland of I. geoffrensis
is mucous in nature as that of Pontoporia, and it also clearly forms theduodenal pouch as that of Platanista. The duodenal pouch of Platanista isSci. Rep. Whales Res. Inst.,
No. 36, 1985

~<: ;w.
i<'~[~::>J~~~\Jt"'-°'~"'::>J

mucous0.3-1.2 mm

not found

scattered bundlesof muscle fibers

duodenum proper

indistinct

1.5 x 0.6 cm

Nature of the intramural
cystic gland

Thickness of the mucosa

Lymphatic nodules

Musculature around thehepato-pancreatic duct

Location of opening of thehepato-pancreatic duct

Duodenal papilla

Size of plica longitudinalisduodeni**

circular muscle layerof the duodenal wall-

indistinct

2.0 x 1.0 cm

lip-like prominencearound the orificeduodenal ampulla

abundant-

duodenum proper

l.3mm

mucous*absent*muscle layer

Lipotes
vexillifer3!

0.4-0.6 mm

mucous*absent*submucosa*

Inia
boliviensis2!

indistinct

1.5 x 0.7 cm

1.5 x 0.9 cm

duodenum proper

thin circular layer,
many muscle fibers
scatteredabundant

0.5-2.4 mm

serous,partially mucous

present

submucosa

Platanista
gangetica5!

indistinct

duodenum proper

well-developed longitudinal muscle layerpresent

0.6-1.3 mm

mucousabsentsubmucosa

Pontoporia
blainvillei 4J

References: 1) Yamasaki and Kito (1984) and the present study, 2) Zhou et al. (1982), 3) Zhou and Li (1981), 4) Yamasaki et al. (1975)
and Takahashi et al. (1976), 5) Takahashi and Yamasaki (1972) and Yamasaki et al. (1972).
- Data not given. * Data suggested from photomicrographs of the hepato-pancreatic duct. ** Length x width.

present

Duodenal pouch

submucosa

Inia
geojfrensis 1!

COMPARISON OF THE DUODENAL PORTION OF THE HEPATO-PANCREATIC DUCT IN THE FRESH WATER DOLPHINS

Location of the hepatopancreatic duct in theduodenal wall

Character

TABLE 1.

t:I

(j()

<.Oc...,c0I:;:)

M::r:...,::r:0..,,

Clc0"':)>
t""'zM

t:I0c

94

KITO AND YAMASAKI

more developed than that of I. geoffrensis and is especially characterized by thepresence of many circular folds on its inner surface and the presence of villiof the mucosa; Pontoporia has no pouch in the duodenal wall*. There is nomention of the nature of the intramural cystic gland in Lipotes and J. boliviensis,
though the photomicrographs of the hepato-pancreatic duct in the duodenal
wall in Lipotes (Fig. 2-2, Zhou and Li, 1981) and I. boliviensis (Plate 4A, Zhou etal., 1982) suggest that both their glandular structures are mucous in natureand they have no distinct duodenal pouch. If the duodenal pouch is really
missing in the bile-passage of I. boliviensis but present in that of I. geoffrensis,
the feature of the duodenal pouch appears to be one of the importantcharacters in which to classify these two closely related dolphins of thegenus Inia.
According to Kamiya (1962), the intramural cystic gland is located in thesubmucosa of the duodenum in whalebone whales and it is located in the circular muscle layer of the duodenum in toothed whales except in the case of
the sperm whale, whose gland is located in the submucosa, the same as inwhalebone whales. Yablokov et al. (1972) added to Kamiya's view, based upon
their investigation on the duodenum of the white whale, Delphinapterus, thatthe intramural cystic gland has its own musculature in toothed whales (exceptthe sperm whale) and is not found in whalebone whales and the sperm whale.
Among the fresh water dolphins, Lipotes has the intramural cystic gland in themuscle layer of the duodenum as do most toothed whales, though it is not
mentioned whether the gland of Lipotes has its own musculature or not. The
Pontoporia, Platanista, and Inia have the intramural cystic gland in the submucosa as do whalebone whales and the sperm whale. The three differ, however,from whalebone whales and the sperm whale in regards to the distributionalfeature of the musculature in the submucosa. The intramural cystic gland of
Pontoporia is surrounded by a very thin submucosa and a remarkably developed muscle layer, mainly consisting of longitudinal muscles, of thehepato-pancreatic duct; so that it appears to be located in the muscle layer ofthe duodenum. The intramural cystic gland of Platanista is also surrounded
by a thin submucosa and a relatively thin muscle layer, and many muscle
fibers are distributed within the submucosa and lamina propria of the duct.
The intramural cystic gland of Inia is characterized by the scattered bundlesof muscle fibers intermittently running near the middle of the thick submucosa between both the mucosa of the duodenum and the hepato-pancreaticduct. Thus, in toothed whales, the fresh water dolphins seem to be a peculiar
group consisting of dolphins having the intramural cystic gland with its own
musculature in the submucosa of the duodenum and those dolphins having
the intramural cystic gland in the muscle layer of the duodenum.
The duodenal portion of the hepato-pancreatic duct of the fresh water* The glandular structure of the hepato-pancreatic duct having no distinct duodenal pouch is thought
to be a kind of the intramural cystic gland.

Sci. Rep. Whales Res. Inst.,
No. 36, 1985

DUODENAL POUCH OF THE BOUTU

95

dolphins have some important and useful characters as do other structures,such as the skelton, brain, the other digestive and respiratory organs, in orderto clarify the phylogenetic relationship among the fresh water dolphins andcetaceans. For example, the location of the opening of the hepato-pancreatic
duct into the duodenal lumen is already considered as a plesiomorphouscharacter (located at duodenum proper) or an apomorphous character(located at duodenal ampulla) in discussing the phylogeny of the fresh water
dolphins (Zhou, 1982). We will continue the discussion about the fresh water
dolphins when more details and new findings are gathered in the future
which will be sufficient to consider their phylogenetic relationship.

ACKNOWLEDGEMENTS
We wish to thank Dr T. Tobayama, Kamogawa Sea World, Chiba, for hiskindly supplying the specimen for this study, and Professor Dr K. Takahashi,
Department of Anatomy, Sapporo Medical College, Sapporo, for his valuableadvice.

REFERENCES
KAMIYA, T., 1962. On the "intramural cystic gland" of the cetacea. Acta Anat. Nippon, 37: 339-351. (inJapanese with English summary).
TAKAHASHI, K. and F. YAMASAKI, 1972. Digestive tract of Ganges dolphin, Platanista gangetica. 11. Small andlarge intestines. Okajimas Fol. anat. jap., 48: 427-452.
TAKAHASHI, K., F. YAMASAKI and T. KAMIYA, 1976. Extrahepatic bile-passage of Franciscana (La PlataDolphin), Pontoporia blainvillei. Okajimas Fol. anat. jap., 53: 115-126.
YABLOKOV, A.V., V.M. BEL'KOVICH and V.l. BoR1sov, 1972. Whales and dolphins. Acad. Sci. USSR, Moscow.
472 pp. (in Russian). (English translations were also referred; Joint Publications Research Service,Virginia, 1974-Part I and 11).
YAMASAKI, F., K. TAKAHASHI and T. KAMIYA, 1972. Liver and bile-passage of Ganges dolphin, Platanista
gangetica. Okajimas Fol. anat. jap., 49: 365-390.
YAMASAKI, F., K. TAKAHASHI and T. KAMIYA, 1975. Digestive tract of La Plata dolphin, Pontoporia blainvillei.
11. Small and large intestines. Okajimas Fol. anat. jap., 52: 1-26.
YAMASAKI, F. and K. KITo, 1984. A morphological note on the intestine of the Boutu, with emphasis on its
length and ileo-colic transition compared with other platanistids. Sci. Rep. Whales Res. Inst., 35:
165-172.
ZHOU, K. and Y. L1, 1981. On the intestine of the Baiji, Lipotes vexillifer. Acta Zoo!. Sinica, 27: 248-253. (inChinese with English abstract).
ZHOU, K., Y. LI and G. PILLER!, 1982. The digestive tract of Inia boliviensis (D'ORBIGNY, 1934). Investigations
on cetacea, 13: 125-133.
ZHou, K., 1982. Classification and phylogeny of the superfamily Platanistoidea, with notes on evidence ofthe morphology of the cetacea. Sci. Rep. Whales Res. Inst., 34: 93-103.

Sci. Rep. Whales Res. Inst.,
No. 36, 1985