ELECTROCARDIOGRAPHICAL STUDIES ON BOTTLE-NOSEDDOLPHIN (T RUSIOPS T RUNCATUS)KIKUJI TOKITA* AND ECG RESEARCH GROUP**
So far as the authors know, little studies on ECG of the whale havebeen reported. This paper deals with ECG of Trusiops truncatus which
the authors had opportunity to obtain on July 18, 1957, when they weretransported alive by trucks overland, from fishing-port Arari to Enoshima
Aquarium in which they were to be reared.
The reason to study ECG of the whale is as follows. After the reporton digitalis in 1932, Tokita and his collaborators published a paper on
the mechanism of its effect on heart-rate in 1951 and 1952, a new aspectof the regulation mechanism of autonomic nerve. This stimulated theauthors to begin studies in order to reveal the heart-rate regulation
mechanism by collecting the ECG of laboratory animals and those inzoo, extending from mouse to elephant, rice-bird to crane, and killifish
to commom boa. In the course of the studies, the authors were afforded
this opportunity.
CONDITION OF WHALE AND ECG-RECORDING

Before the transportation, Trusiops had been reared for two weeks
to a month in Arari Bay with squids or fishes. ECG-recording was madeat the port, immediately after they were loaded on auto-trucks, next atMishima after 4 hours and finally at Enoshima after 8 hours. On thetruck, one side of the animal body was immersed in sea-water containedin a canvus tank surrounded by ice-pillars, and the other side was covered
with blancket moistened with the sea-water. The road passed throughhigh grounds between Arari and Mishima, and through the Hakone
Mountain, about 1,300 meters high between Mishima and Enoshima.
Water temperature in the canvus tank was 23°C at Arari and 30°C atMishima and Enoshima. Body-weight of Trusiops was 260 to 300 Kg,
but an infant was 110 Kg. Unfortunately, one of the loaded died on thetruck at Arari, but the other four reached safely to Enoshima and arestill living.
To induce ECG, electrodes (Injection needle) were implanted into thebody at the spots corresponding to those of the human body, or the* Department of Pharmacology, Medical School, Toho University, Tokyo.
**Ryuta Ito, Sukeaki Nishimuta, Yoshinori Kawasaki Naoyoshi Nakamura, Kozo Saito,
Sho Isogai and Yasuo Ogawa.

159

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ELECTROCARDIOGRAPHICAL STUDIES ON BOTTLE-NOSED DOLPHIN

165

metalplate-electrodes were attached to these spots without implanting.
RESULTS

1) Heart-rate. The heart-rate of four Trusiops ranged 81 to 137 per
minute and even after transportation, increasing in the course of timein two cases and decreasing in other two.
2) Details of ECG. Equal to other animals, the beats were regular
except in the one which died, and P, QRS and T were observed. Proportions of RR to other parts did not differ from those of other animals.
T was relatively low similar to a large animal such as elephant. In
one case, T was normal at Arari, reversed at Mishima and recovered
at Enoshima. In a second, T was normal at Arari, but reversed slightly
at Mishima. But irrespective of these changes, they swam lively in
Enoshima Aquarium and they are still alive. In the case which died,arrhythmia, markedly reversed T and disrupted R were observed.
3) Respiration. The rate was 1.5 to 4 per minute in the Aquariumin which they could swim voluntarily. But on the truck, it ranged 4
to 7 per minute and not regular during transportation.
DISCUSSION AND SUMMARYAs described above, average heart-rate was 100 per minute. This wasunexpectedly rapid. The first problem is whether this rate was normal
or not. Although this record was done under unusual conditions, in otherwords, although aquatic animals were investigated on land under intensive stress, the heart-rate did not change markedly and details of ECG
were not influenced exceedingly. From these results, it can be remarked
that±20% of this average would be the normal range of heart-rate forbottlenosed dolphin. The difference between that of adult and infant
seemed small.
Low voltage of T is equal to that of a large animal such as elephant(for example, Indila in Ueno zoo, Tokyo). Reversal of T would be thesign of shock as is seen in human, because the one which died showed
the sign of reversal in significant grade, but that of other cases wasslight and might have recovered after they were released into theAquarium.
Thanks are due to Dr. M. Nishiwaki and Staffs of Enoshima Aquarium
who offered the authors the opportunity to investigate and the Fukuda
ECG Co. who help them in the recording.