Basic Studies on Artificial Breeding of Killer Whales

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Initial research plan was much changed due to the difficulty of use in subject animals of killer whales in the aquarium during the study period, but we obtained following information as basic knowledge for the future success of artificial breeding of killer whales. That is ; l) we succeeded in the sperm freezing of the Pacific white-sided dolphin by applying straw method ; 2) the comparative analysis of sperm external morphology of ten cetacean species including the killer whale revealed that sperm of killer whale is long, and the head is widest and fan-shaped ; 3) sperm motion analysis by using Cell Soft software showed that post-thaw sperm of the bottlenose and Pacific white-sided dolphin have characteristics (motility, speed etc.) similar to those of sperm of humans and rabbits ; 4) ultrasonic diagnosis of gonads (testes and ovaries) for bottlenose dolphins and Pacific white-sided dolphins was attempted, and ovarian corpora, follicles and fetus were identified with the seasonal changes in testis size, and 5) hormonal study on corpora lutea and placenta suggested the source of progesterone secretion during pregnancy was both of ovarian corpus luteum and placenta in dolphins, and no pregnancy specific proteins were detected in serum samples and placental tissues from pregnant dolphins by electrophoreisis and hCG EIA, Serum levels of estrone sulfate in pregnant dolphins fluctuated with different patterns between species studied (striped dolphins and Dall's porpoise) and pregnancy stages (early and late).