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This paper offers the first study of diurnal variations in the use of an estuarine habitat by Indo-Pacific humpback dolphins. Passive acoustic data loggers were deployed in the Xin Huwei River Estuary, Western Taiwan, from July 2009 to December 2010, to collect biosonar clicks. Acoustic encounter rates of humpback dolphins on the riverside of the estuary changed significantly over the four tidal phases, instead of the two diurnal phases based on the recordings from 268 days. Among the tidal phases, the encounter rates were lowest during ebb tides. Additionally, circling movements associated with the hunt for epipelagic fish significantly changed in temporal and spatial presence over the four tidal phases, matching the overall pattern of encounter rate changes in the focal estuary. Our findings suggest that the occurrence pattern and habitat utilization of humpback dolphins are likely to be influenced by the tidal-driven activity of their epipelagic prey. 相似文献
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This is the first report of gynandromorphy in Isoptera. An Asian dry-wood termite, Neotermes koshunensis (Shiraki) [Kalotermitidae], possessing both male and female phenotypic characteristics, was found on Okinawa Island, Japan. This deformed individual showed morphological and anatomical hermaphroditism in the abdomen. The right side of the seventh sternite was the female form and contained an ovary, while the left side was the male form and contained a testis. Genotypic analysis revealed that this individual was a genotypic bilateral chimera. These results suggested that the termite was a bilateral gynandromorph with a male left side and a female right side. As reported previously in other insects, double fertilization (by two sperms, one with an X and one with a Y chromosome) of a binucleate egg is the most likely mechanism that generated this genotypic bilateral chimera. N. koshunensis has the ability to reproduce through parthenogenesis, in which the secondary polar body is likely to be used for nuclear phase recovery. If the second polar body in this mechanism has high fertility and healthy embryogenic potential, like an egg nucleus, some of gynandromorphs might be produced by a side effect of parthenogenetic ability. 相似文献
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Tomonari Akamatsu Kiyomi Nakamura Ryo Kawabe Seishiro Furukawa Hiromi Murata Akihiro Kawakubo Masayuki Komaba 《Marine Biology》2010,157(8):1879-1887
A number of local populations of finless porpoises (Neophocaena phocaenoides) are widely distributed throughout the warm coastal waters of Asia. The Omura Bay population, consisting of approximately
300 individuals, is the smallest of five populations inhabiting Japanese waters. It is a relatively new population that established
after the global warming that took place approximately 9000 years ago. To observe whether these porpoises appear in the major
corridor to the ocean from Omura Bay, we used acoustic monitoring to record occurrences of finless porpoises from November
2007 to May 2009. A stereo acoustic event recorder recorded the intensity and the sound source direction of biosonar signals,
providing independent traces of sound sources corresponding to each detected animal. A total of 226 individuals were detected
over the 1.5-year monitoring period, of which 76% occurred at night and 73% occurred during March and April. We compared the
presence of porpoises to the Japanese anchovy catch in Omura Bay and the Hario Strait over the same period. Results suggested
that possible reductions in anchovy resources in the bay could attract porpoises to the outside of their normal habitat. In
total, 70% of the porpoise recordings took place when the tidal current was moving out of Omura Bay. Porpoises might follow
the prey that are transported out of the bay due to the strong outbound current. The finless porpoises confined to the bay
might extend their swimming area if prey is available. 相似文献
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