TASTE BUDS IN THE PITS AT THE POSTERIOR
DORSUM OF THE TONGUE OF
STENELLA COERULEOALBAFUSAO YAMASAKI, SHUNRO KOMATSU
Department of Biology, Sapporo Medical College, Sapporo

AND
TOSHIRO KAMIYA
Department of Anatonry, Faculty of Medicine, University of Tokyo, Tokyo

ABSTRACT

There are five to eight pits that form a V-shaped row opening anteriad at
the posterior dorsum of the tongue of Stenella coeruleoalba. The pits have fiveto ten warty projections protruding from their bottoms. Epithelium covering
the projections is markedly thinner than that of the dorsum. Taste buds resembling those of other mammals can be found in the epithelium of the projections and in that of the thinned side wall of the pits of young dolphins.
However, taste buds are considerably few in number. They cannot be observed in adults.
INTRODUCTION

It is not known whether Cetacea possess a gustatory sense because taste buds
have not been identified in all cetacean species. Yablokov (1961 ; 1972) has
suggested that depressions located on the V-shaped line on the root of the odontocete tongue might act as chemoreceptors. Sokolov and Volkova (1971) investigated the tongues of Stenella coeruleoalba, Phocoena phocoena, Tursiops truncatus, andDelphinus delphis, but they failed to find taste buds. Neither could Sokolov andKuznetzov (1971) find taste buds in Lagenorhynchus acutus, Tursiops truncatus, andPhocoena phocoena. However, these authors suggested that the dolphins must havea gustatory sense according to examinations in which specimens responded well toseveral chemical substances dissolved in sea water. Recently, taste buds havebeen observed within the epithelium of the papillae of the pits located on the rootof the tongues in Delphinus delphis and Tursiops truncatus (Suchowskaja, 1972) andin T. truncatus (Donaldson, 1977). We have found taste buds, which resemble
those of the gustatory cells in other mammals, lying in the epithelium of the pits
in Stenella coeruleoalba. The follwoing brief report on this dolphin should help todisseminate knowledge of the gustatory sense of Cetacea.

Sci. Rep. Whales Res. Inst.,

No. 30, 1978, 285-290

286

YAMASAKI,KOMATSUANDK A MIYAス!fATERIALSANDMETHODSThe materi
alsexamine
d were taken from fetal,young and adul
ts
t
age
s oft
hestr
i
pe
d dol
phin,St
enel
l
acoer
ul
eoal
ba(bodylengt
h60,98,115,150,about200,237,and 238cm)
,cole
ct
e
d o町 thePacif
i
cc
oas
tofI
zupen
insu
lai
nJapan. 1'在ater
were白xedi
n1
0% formal
i
nsol
ut
i
ona
tt
hesit
eofcolect
ion ands
entto ourla‑borator
y. Afterma
crosc
opi
calobservations,pie
ce
scor
r
e
spondingt
ot
hepi
t
swere
embe
dde
dinpar
aff
i
norc
elloi
di
n. Serials
eetionswere made and then stainedwithhematoxyl
i
nande
os
i
n. Typieals
ectionswer
es
e
lect
e
dfo
rphot
omicrograp
hy.
内OBSERVATI
ONSAND DISCUSSION
Thedorsum oft
he tongue ofStenellacoeruleoalba,ass
hown inF
ig.1, exhi
bit
sa
V‑s
haped rowwi
t
hf
ivet
oei
ghtpi
t
sopeninganteria
dattheposter
ioraboutone‑
f
ourt
h oft
hewhol
ele
ngt
hoft
he t
ongue （仕om apext
ot
heepi
glott
is). Sokolov
andVolkova(1971)obs
erve
dt
hre
eton
inei
nt
hi
sdol
p
hi
n. Theangl
eoft
heV isabout100。in adults, and iss
omewhat blunteri
n youngerspe
cimens. No pi
tsexistonthemidline,andtheirnumberisnotalwayst
hesameonbothsides. Thes
hapeoftheopeni
ng ofthep
itsi
sr
ound i
nt
heear
l
ys
t
age becoming long andnarrow, and trench‑like in adult
s. In the adul
t,t
he pi
ti
sapproxima
t
el
y2 t
o8m minle
ng
th,1t
o2m minwi
dt
h and lt
o1.5m mindepth. Thesize,shape,

2Fi
g.I. Th
eposteri
ordorsumoft
hetongueo
fSte
11ellacoeruleoalba(bodyl
ength,238cm)v
iew
e
df
romt
hed
or
s
alaspect. Fiv
ep
it
sar
cp
r
es
en
tfo
rmi
n
gaV‑
shapcdrow. Ling
ualg
lan
dsa
r
ewelde
v
e
lope
dexc
epta
r
ou
n
dt
hec
i
r
cu
mf
er
enceo
fthe
pits,andg
landorificesa
r
ec
lear
lyv
isiblea
sb
lac
ks
potso
nt
hedo1sum. XI.I.
Fig.2. Do
rsalv
iewo
ft
heo
neo
ft
hepi
tso
ft
he1
50cmαlf. War
t
ypr
o
ject
ionsarcc
lear
lyv
isiblei
nt
hepi
. ×2
t0.
S
ci.Re
p.Hノ~iales Res.l
1
1sl.
,

No.30,1978.

TASTE BUDS IN STENELLA

287

and number of the pits vary considerably from specimen to specimen in the Stenella
observed. The pits may be variable in appearance in the same species in otherdolphins as illustrated by the following description in Tursiops truncatus: three tonine fossae (Sokolov and Volkova, 1971); small cavities (Suchowskaja, 1972);
distinct cavities rather than a groove (Caldwell and Caldwell, 1972); an 8 to
12 mm long continuing groove on the left and three shorter sections on the right(Donaldson, 1977). These seem to be due to individual differences and the degreeof development. In Delphinapterus leucas, five shallow, oval hollows were demonstrated at the corresponding region by Yablokov (1972). Therefore, the appearance of the pits also seem to differ in interspecies. However, in the observedcases of Platanistidae (Platanista, Pontoporia and Inia), no pits could be found inthat region (Yamasaki et al., 1976a).
As shown in Fig. 2, there are five to ten warty projections, conical in shape,
protruding from the bottoms of the pits in the 115 and 150 cm calves. However,there are only one or two projections in each small pit. They are approximately
0.3 to 0.8 mm in diameter at their bases and about 0.3 to 0.6 mm in height. The
upper limit of the projections never reaches the surface of the tongue. The projections are remarkably visible in the young stage, and in the adult they becomerather indistinguishable besides being often hard to observe from the dorsal aspect
because of the elongation and narrowing of the pit orifice. Aggregations of lymphocytes are present in places in the lamina propria of the pits. It is likely thatthe projections correspond to conical-shaped papillae in the Tursiops truncatusobserved by Donaldson (1977) and possibly to the 'globular bodies' in Delphinapterus leucas described by Sonntag (1922).
Pits can already be recognized in a 60 cm fetus. Since the developmental
degree of each pit varies considerably, various stages of development of the pits
can be observed in a 98 cm fetus. At first, a hollow develops in the area corresponding to the future pit and breaks away from the circumference. It then sinks
and the broken blocks, which are covered by thin epithelium, form warty projections.
Lingual glands, sero-mucous in nature, are well developed from the mid partof the dorsum of the tongue to the epiglottis in the 115 cm calf and they are extremely well developed in the adult. The glands open on the dorsal surface, except
for the circumference adjacent to the pit orifice. The galnds also open at thebottom of the pit around projections almost with no gland ducts. In some projections the glands open at their tips with a short duct. The glands are not always
well-developed at the bottom of the pit as compared with those of the rest of thetongue. Sokolov and Volkova ( 1971) used the term ' fossa ' for the opening of
the lingual glands seen on the dorsum and also used this term in considering thepit to be a deeper and larger fossa. Donaldson (1977) has suggested that the pits
may be derived from the gland ducts, based on the observation of the marsupial
tongue (Kubota et al., 1963). In the abovementioned observation of the fetal
tongues of the Stenella, we could not clarify whether the pits are derived from lingual
gland ducts. Further studies on this subject will be made in the near future.
Sci. Rep. Whales Res. Inst.,No. 30, 1978.

288

YAMASAKI,KOMATSU ANDKAMIYA

Thedorsumoft
hetongueoft
hecalv
esobservedi
scoveredbyat
hic
kstratifiedsquamousepithelium,approxi
mately 600μm ormor
ei
nt
hic
kn
e
s
s
, ofwh
ic
ht
heat
i
o
nbutwithoutcompleted
is‑supe
rf
ic
i
all
aycrs
howsatendcncytowardc
orni五cappearanceofn
uclei. The ep
it
heliu
mt
hin
sremarkablya
tt
he insideoft
hepitall and bottom), and measur
es 40 to 100μm (Fig. 3a・）
(project
ion,its 副巴 wPap
il
lae ofconnecti
ve t
issu
eoft
he dorsum ar
ew
el
ldev
e
lo
ped but t
hoseon thc
ins
idcoft
h
cp
i
tar
enot
. Tastebudsr
esemblingt
hos
eofothermammalscanbe
cl
car
l
yobs
cr
v
edl
yi
ngi
nt
heepi
theliu
moft
h
epr
oject
io
nandt
hesidewalloft
hc
pi
ti
nt
he115cmand 150cms
pe
c
ime
ns(Fi
g.3b)
. Tastebudsareal
wayspr
esent
w
it
hi
nt
het
hi
115cmspec
imen arccovercdbya l
ayerc
on
s
is
t
in
goftwoort
hr
e
巴 e
lon
gat
ec
el
Is
町

43o
F
i
g.3
a.P
hoto
mi
c
rog
r
ap
ho
fav
er
t
icals
ec
t
i
ono
fon
eo
fthep
i
tso
ftheISOcmc
alf.
Thec
pit
hcliu
mcov
eringtheproje
ct
ionsandt
hesidew
allo
ft
hep
it
si
sre
mar
kablyt
hinn
e
rt
hant
ha
toft
hedo
1
判 m. Twotastebuds(arrow)areobserv
e
dint
het
hi
nepitheliu
m. L
ingualg
landsopenatt
hebottomofthepit. ×25.
Fig.3
b. Avi
ewo
ft
hep
ar
ti
ndi
cate
db
yt
hea
rro
wi
nF
i
g.3
au
nde
rhi
ghe
rm
ag
ni
f
i
‑
cat
i
on.T
a
st
eb
u
dsl
i
ei
nt
het
hi
np
a
rto
ft
hee
pi
t
he
li
u
m. Theo
u
te
rt
ast
ep
or
e
canb
es
ee
ni
nt
heu
ppe
rt
ast
eb
u
d. ×3
25.
wi
t
houtanuppers
tr
at
i
fi
eds
quamousepit
hel
iall
aye
r. Notast
ebudsa
r
epr
esent
i
nt
hesea
r
eas. Taste bud
sextend from t
he basementme
mbrane almost t
ot
he
epi
t
hel
i
als
ur
face. Anou
t
e
rt
ast
eporeandtwok
indsofc
ells,tast
eandsupporting
,
e
cog
n
iz
e
d. Thel
onga
xi
soft
h
e budsi
sapproximately40 t
o45μ mincan b巴 rlength,andabout30t
o40μ macross.I
nthespec
imenofapproximately200cm
ndi
amet
e
r,ar
el
ocatedi
nt
h
el
ower
bodyl
e
ngt
h,t
ast
eb
u
ds,about20t
o30μ mione‑t
h
ir
doft
h
ee
p
it
h
eliumwithoutano
u
t
e
rt
ast
ep
or
e. C
e
l
l
sformi
n
gt
h
ebuds
ar
er
at
h
e
ri
r
regu
l
a
ri
narrangement,probablyduet
odegener
ation. Thesef
in
di
n
gs
ar
es
i
mil
ari
n appearance tothose observed by Donaldson (1977)int
headult
Sc
i.Rψ.WhalesRes.I
nst.
,No.30,1978.

TASTE BUDS IN STENELLA

289

Tursiops truncatus. We suppose that larger taste buds having an outer taste pore
will be found in the younger Tursiops. Taste buds could not be found in the specimens of the adult Stenella (237 and 238 cm). In the 98 cm fetus, the part corresponding to the pits is covered with thin epithelium (20 to 40 pm, about one-tenthof the thickness of that of the dorsum), and is on almost the same level as the tongue
surface. A few primordial taste buds, similar to those of fetal fur seals observed
by Kubota (1968), could be found within this area. Features of the pits, warty
projections, and taste buds in the Stenella we observed are essentially similar to thoseof the Tursiops and DeljJhinus reported by Suchowskaja (1972), although the author
used other terms of reference*.
Although taste buds in the Stenella can be clearly observed in the pits of theyoung stage (115 cm and 150 cm), they are considerably few in number, and may
degenerate with age. This may be one reason that taste buds have not been foundin Cetacea since examinations have been done only on few sections or in adults.
There is a possibility of finding taste buds in other cetacean tongues when detailed
observations are done on all parts of the pits with consideration of age. There are
no descriptions concerning the body length of the Tursiops and Delphinus in Suchowskaja's article (1972). The examination on the time sequence of taste buds will beexpected in other odontocetes.
Pit-formation may precede the appearance of the taste buds because typicaltaste buds have not been observed in the developing stages of the pits of fetuses.
Since the calves of the Stenella start feeding on solid food at the age of about 0.5year, at a body length of about 140 cm (Kasuya, 1972), it seems that there is somerelations between feeding time and the formation of the taste buds. Adult dolphins may depend upon some other senses, possibly cultivated with age, for taking
food if taste buds are realy nonexistent in adults. Donaldson (1977) also supposedthat young dolphins might first learn which fish to eat by taste and gradually these
acceptable-tasting fish might come to be recognized by appearance.
Sokolov and Volkova (1971) have stated that papillary projections along theanterolateral margin of the tongue in Odontocete evidently have a receptor function. However, these projections of the Stenella have no taste buds and nerve fiber
bundles are inconspicuous. Therefore, we have considered the projections to bestructures with a mechanical function for suckling rather than as a sensitive partof the tongue (Yamasaki et al., 1976b; 1978).
Absence of lingual papillae is another characteristic of the cetacean tongue.
Of course, there are no vallate papillae seen in other mammals. Donaldson (1977)
thinks that the linguopharyngeal groove (corresponding to what we call a pit)
might be a variation of the circumvallate papilla. The pits, at least in position,
may correspond to the vallate papillae of other mammals. The tast buds in mammals, for example in man, usually lie within the thinner side surface epitheliumof the foliate and circumvallate papillae. The dorsum of the tongue of dolphinshas a much thicker epithelium than that of other mammals. The epithelium cover-* Suchowskaja called the warty projections and the taste buds as 'taste buds' and 'gustatory papillae',respectively.

Sci. Rep. Whales Res. Inst.,
No. 30, 1978.

290

YAMASAKI, KOMATSU AND KAMIYA

ing the inside of the pits is markedly thinner than that of the dorsum of the tongue.
This fact may be the reason that the existence of the taste buds is only limited to thepits.
Generally, in other mammals, there is a V-shaped sulcus terminalis just behindthe vallate papillae by which the tongue is divided into the body and root. No
sulcus terminalis and no trace of the foramen caecum there can be seen on thedolphin's tongue. It should be adequate to consider that the body and the rootof the tongue meet at the point of the V-shaped row with pits, although it is necessary that embryological observations (e.g. as for the location of the dividing line
between the first and second pharyngeal arches) and examinations of the innervation be made. In Platanistidae, as mentioned above, no V-shaped mark can beseen on the dorsum of the tongue, and taste buds are lacking in all parts of thetongue (Yamasaki et al., l 976a ). Further observations are expected concerning
the gustatory sense of Platanistidae.
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C. C. Thomas, Springfield.
DONALDSON, B. J., 1977. The tongue of the bottlenosed dolphin (Tursiops truncatus). pp. 175-197. In:R.J. Harrison (ed.) Functional anatomy of marine mammals. Vol. 3, Academic Press, London, New Yorkand San Francisco.
KAsUYA, T., 1972. Growth and reproduction of Stenella coeruleoalba based on the age determination by meansof dentinal growth layers. Sci. Rep. Whales Res. Inst., 24: 57-79.
KUBOTA, K., 1968. Comparative anatomical and neurohistological observations on the tongue of thenorthern fur seal (Callorhinus ursinus). Anat. Ree., 161: 257-266.
KUBOTA, K., J. KUBOTA, N. FUKUDA, S. AsAKURA, S. NAKAGAWA and M. MAsur, 1963. Comparativeanatomical and neurohistological observations on the tongue of the marsupials. Anat. Ree., 147: 337353.
SoKOLOV, V. E. and 0. V. VoLKOVA, 1971. Structure of the dolphin's tongue. pp. 119-127. In: K. K.
Chapskii, and V. E. Sokolov (eds.), Morpholog_v and ecology of marine mammals; seals, dolphins, porpoises.
Israel Program for Scientific Translations, Jerusalem (English translation).
SoKOLOV, V. E. and V. B. KuzNEzov, 1971. Chemoreception in the Black Sea bottlenosed dolphin, Tursiops
truncatus. Ed. Academy of Sciences of the U.S.S.R., Moscow (in Russian), 201: 4, pp. 998-1000.
SONNTAG, C. F., 1922. The comparative anatomy of the tongues of the Mammalia. VII, Cetacea, Sireniaand Ungulata. Proc. :(ool. Soc. Land., 630-657.
SucHOWSKAJA, L. I., 1972. The morphology of the taste organs in dolphins. In: G. Pilleri (ed.), Investigations ofCetacea. IV, Berne, pp. 201-204.
YABLOKOV, A. V., 1961. On the "sense of smell" in marine mammals. Trudy soveshchaniya po ekologii ipromyslu morskikh mlekopitayushchikh., No. 12 (cited from Sokolov and Volkova, 1971).
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YAMASAKI, F., H. SATOMI and T. KAMIYA, 1976 a. The tongue of Franciscana (La Plata) dolphin, Pontoporia blainvillei. Okajimas Fol. anat. jap., 53: 77-92.
YAMASAKI, F., H. SATOMI and T. KAMIYA, 1976 b. An observation on the papillary projections at the lingual
margin in the striped dolphin. Sci. Rep. Whales Res. Inst., 28: 137-140.
YAMASAKI, F., S. KoMATSU and T. KAMIYA, 1978. Papillary projections at the lingual margin in the striped
dolphin, Stenella coeruleoalba, with special reference to their development and regression. ]. Morphol.
157: 33-47.
Sci. Rep. Whales Res. Inst.,

No. 30, 1978.