A MALFORMED FOETUS OF A SOUTHERN SEI WHALE

AKITO KAWAMURA l)
During the Antarctic whaling season of 1967/68, a badly malformed
230 cm long female foetus was found on the FIF Nisshin Maru. It was from asei whale (Balaenoptera borealis) (No. 1545) caught at 57° 35' S, 84° 54' Eon
26 February 1968. The mother was 15.4 m long and 11-years old, with sevenovarian corpora including the corpus luteum of this pregnancy. The total
length of the foetus was measured from the most anteriorly protruding partof the premaxilla to the notch between the flukes. It was recorded in thecatch log as 218 cm long. The foetus showed a harelip-like malformation due
to grotesque development of the head region. The premaxilla was greatly
deformed, resulting in a downward curve. A deep depression was evident on
the lower mandible (Fig. 1). Although the animal was not dissected, theentire head appeared poorly developed as far as the region of the maxillae.
This region appeared shorter than the premaxillae region. The tail flukes
sloped considerably, causing the entire fluke spread to be very narrow.
Essentially the same characteristic was reported by Ohsumi (1959) for a
deformed fin whale (B. physalus) foetus. Measurements for the right flipper:
1) Tip to axilla, 2) anterior end of lower border to tip of flipper, and 3)
greatest width of flipper, were 27.0, 38.0, and 8.3 cm, respectively. These
measurements are the same as those of a 244-245 cm long, normally developed foetus. The foetus was placed in formalin solution and transferredfrom the Whales Research Institute to the Institute of Cetacean Research inTokyo.
The upper jaw of the present foetus was clearly deformed. Although one
instance of an upwardly bent upper jaw has been reported in Stenella
coeruleoalba (Tobayama and Uchida, 1964), Nakamura (1968) stated, aftersurveying the occurrence of deformed lower jaws in postnatal sperm whales(Physeter catodon), that malformation of the upper jaw rarely occurs in cetaceans. Two examples similar to the present case have been reported for fin
whale foetuses (Nishiwaki, 1957; Ohsumi, 1959), and siamese twins of thehumpback whale (Megaptera novaeangliae) had upper jaw deformation tosome extent (Zemsky and Budylenko, 1970, Figs 3 and 4). However, deformation appears to occur only rarely in postnatal baleen whales. Extensive
head and mouth region malformation in whale neonates probably causes
difficulty in sucking or later feeding, thus greatly lessening the chances ofsurvival.
1)

Faculty of Bioresources, Mie University, 1515 Kamihama-cho, Tsu, Mie, 514 Japan

Sci. Rep. Cetacean Res.,
No. 1, 1990, 93-95

94

KAWAMURAREFERENCES
NAKAMURA, K. 1968. Studies on the whale with deformed lower jaw, with special reference to its feeding.
Bull. Kanagawa Pref. Mus., Kanagawa, Japan 1: 13-27.
N1sHIWAKI, M. 1957. One-eyed monster of fin whale. Sci. Rep. Whales Res. Inst., Tokyo 12: 193-195.
OttsUMI (Kimura), S. 1959. A deformed fin whale fetus. Sci. Rep. Whales Res. Inst., Tokyo 14: 145-147.
ToBAYAMA, T. and UCHIDA, S. 1964. [A dolphin of malformed rostrum.] Geiken Tsushin, Whales Res. Inst.,
Tokyo 151: 43-44. (in Japanese).
ZEMSKY, V. A. and BuoYLENKO G. A. 1970. Siamese twins of humpback whale. Trans. Atlantniro 29: 225-230.
(in Russian).

Fig. 1. A 230 cm malformed female foetus of a southern sei whale found on 26 February 1968. Whale number indicated as 1545 in the catch log of the Nisshin Mam fleet
in 1967/68 season.
CD Entire body of the foetus.
@ Head of the foetus showing the blowholes in an extremely forward pos1t10n,
malformed development of the maxillae and premaxillae regions, and upwardly
curved tip of the lower jaw. The eye is shown by the arrow.
@ Opened mouth showing oral cavity, palatal ridge, tongue and extremely depressed lower jaw.

Sci. Rep. Cetacean Res.,
No. 1, 1990

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