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147
Erwin J.O. Kompanje
Naturalis (Nationaal Natuurhistorisch Museum), Leiden & Natuurhistorisch Museum Rotterdam
Kompanje, E.J.O., 2005 - A case of symmetrical conjoined twins in a bottlenose dolphin Tursiops
truncatus (Mammalia, Cetacea) - DEINSEA 11: 147-150 [ISSN 0923-9308]. Published 29 December
2005
Case reports of conjoined twins (‘Siamese twins’) in wild mammals are very scarce. Most published
reports of conjoined twinning concern cases in man or in domestic mammals. In this article a case of
conjoined twinning in a wild mammal is described: a parapagus dicephalus with unilateral schistopro-
sopus in a bottlenose dolphin Tursiops truncatus stranded on the coast of the Netherlands in 1917. This
case concerns the oldest known case of a symmetrical conjoined twin in a cetacean species.
Correspondence: dr Erwin J.O. Kompanje, Natuurhistorisch Museum Rotterdam, P.O. Box 23452,
3001 KL Rotterdam, The Netherlands, e-mail: e.j.o.kompanje@erasmusmc.nl
Keywords: conjoined twins, parapagus dicephalus, double monster, Tursiops truncatus.
INTRODUCTION
Conjoined twins (‘Siamese twins’) are well
known in man, in domestic and laboratory
mammals, domestic and wild birds and in
wild and captive-bred reptiles, amphibians and
fishes, but are very rarely described in wild
mammals. The precise incidence is unknown,
most likely due to high prenatal and antenatal
mortality. Almost all known cases of con-
joined twins in wild mammals concern unborn
embryos and fetus found during dissection of
the pregnant dead female. The aim of this arti-
cle is to describe a postnatal case of symmetri-
cal conjoined twins in a wild mammal.
Case report
A dead, 125 cm long, newborn female
dicephalic bottlenose dolphin Tursiops trun-
catus (Montagu, 1824), with open umbilicus,
was found on the beach at Wijk aan Zee, the
Netherlands, on 20 July 1917. The specimen
was sold to the Rijksmuseum voor Natuurlijke
Historie (now: Naturalis, National Museum of
Natural History) in Leiden. After preservation,
three photographs were made of the monstrum
(Fig. 1). Shortly afterwards, the specimen
was given on loan to the Anatomical Cabinet
of Leiden University for further study, but
nothing was published on this case. The speci-
men is untraceable now. It is neither in the
Anatomical Cabinet nor in any other museum,
and it is - unfortunately - most probably lost
for science. It supposedly got lost after an
English air raid during the Second World War
(Kompanje 2001). The three photographs
(reproduced here in Figure 1), still present
in the archives of the National Museum of
Natural History, form the only proof of this
rare case. This case was mentioned in a review
of Tursiops strandings along the Dutch coast
(Kompanje 2001).
A case of symmetrical conjoined twins in
a bottlenose dolphin Tursiops truncatus
(Mammalia, Cetacea)
148
DEINSEA11,2005
Figure1ParapagusdicephalusinabottlenosedolphinTursiops truncatesfromWijkaanZee,theNetherlands,20July1917.
adorsalview,bventralview,cheadsinfrontalview.[ArchivesNaturalis,NationalMuseumofNaturalHistory,Leiden]
ab
c
DISCUSSION
Conjoined twins are always conjoined in one
of only eight sites (Spencer 2001, 2003) and
are named after the site of union [see also
Kompanje (2005) - this volume - for further
details]. Normal twinning is very rare in
cetaceans. González et al. (1999) estimated
a 0.5% occurrence of multiple gestation of
all observed pregnant females in small ceta-
ceans. With the exception of the present case,
and of the case described by Cesarini et al.
(2004), only four cases of conjoined twins in
Cetaceans could be traced in the literature, all
found in unborn foetusses during dissections
in the Japanese and Russian whaling industry
(Table 1). Other complex foetal anomalies
found during these dissections includes holo-
prosencephaly, schistoprosopus and anoto-
cephaly, all in baleen whales (e.g., Zinchenko
& Ivashin 1960).
The present case is the first example of
conjoined twins in a wild newborn dolphin.
A diagnosis of a parapagus dicephalus mono-
somos dibrachius with unilateral schistopro-
sopus on the left head in a full-term female
newborn bottlenose dolphin seems accurate.
A second case in a wild newborn bottlenose
dolphin is described by Cesarini et al. (2004).
Judging from the description these authors
gave (two faces, one braincase, one foramen
magnum) this pair of conjoined twins should
be diagnosed as parapagus diprosopus.
Symmetrical conjoined twins in wild terres-
trial mammals have been very rarely reported
(Table 2). Spontaneous occurrence of con-
joined twins in laboratory animals is uncom-
mon. Szabo (1989) reported one conjoined
twin out of 10.000 in the rat and one case in
4000 rabbits bred in 20 years.
Spencer (2000a, 2000b, 2003) provides con-
vincing evidence that symmetrical conjoined
twins are the result of secondary fusion of two
originally separate monovular embryonic discs,
and are not the result of incomplete fission
producing a partially separated zygote.
149
KOMPANJE:symmetricalconjoinedtwinsinabottlenosedolphin
Reference species taxonomy age
Kawamura 1969 Balaenoptera borealis thoracopagus fetus
Kawamura & Kashita 1971 Stenella coeruleoalba cephalopagus fetus
Kamiya et al. 1981 Stenella coeruleoalba parapagus dicephalus fetus
Zinchenko & Ivashin 1987 Balaenoptera acutorostrata thoracopagus fetus
Kompanje 2001 Tursiops truncatus parapagus dicephalus newborn
Cesarini et al. 2004 Tursiops truncatus parapagus diprosopus newborn
Table1PublishedcasesofsymmetricalconjoinedtwinsinCetacea.
Reference species taxonomy age
Reisel 1671 Lepus europaeus cephalopagus newborn
Jung 1671 Lepus europaeus cephalopagus newborn
Seger 1671 Lepus europaeus cephalopagus newborn
Mentzel 1686 Alces alces cephalopagus fetus
Neugebauer 1851 Lepus europaeus cephalopagus newborn
Benesch 1957 Lepus europaeus cephalopagus newborn
Fay 1960 Odocoileus virginianus parapagus dicephalus fetus
Table2Publishedcasesofsymmetricalconjoinedtwinsinwildmammals,otherthanCetacea.
150
DEINSEA11,2005
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Received12October2005
Accepted9November2005
DEINSEA - ANNUAL OF THE NATURAL HISTORY MUSEUM ROTTERDAM
P.O.Box 23452, NL-3001 KL Rotterdam The Netherlands