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タイトル: Otolith strontium : calcium ratios in a freshwater stingray, Himantura signifer Compagno and Roberts, 1982, from the Chao Phraya River, Thailand
著者: Otake, Tsuguo
Ishii, Toshiaki
Tanaka, Sho
キーワード: Himantura signifier
freshwater stingray
Sr : Ca ratio
発行日: 2005年1月31日
出版者: International Coastal Research Center, Ocean Research Institute, the University of Tokyo
掲載誌情報: Coastal marine science. Vol.29No.2, 2005.1, pp. 147-153
抄録: Otolith microchemistry was examined in a freshwater stingray, Himantura signifer, collected from a freshwater region of the Chao Phraya River, Thailand. Otoliths of H. gerarudii and H. imbricata from the estuary at the mouth of the Chao Phraya River, and H. imbricata from the sea adjacent to the river mouth were also examined. Otolith Ca concentration was almost constant among the three species, regardless of their habitat environments. In contrast, Sr concentration and the Sr : Ca ratio differed considerably among the species, those of the freshwater species being at the lowest levels and that of the marine population of H. imbricata the highest. Intraspecific variation in Sr concentrations and Sr : Ca ratios found in H. imbricata from estuarine and marine environments suggested that those levels varied according to the habitat. Otolith Sr concentrations and Sr : Ca ratios of male freshwater stingrays increased with body growth, whereas those of female otoliths decreased temporarily to the lowest level in 250-300 mm disk width (mature) specimens. The findings suggested that H. signifer from freshwater regions enter a brackish or seawater environment at some time in their life history. The marked fluctuations in Sr concentration and Sr : Ca ratio in female otoliths may be related to presumed reproductive behavior, such as ceasing migration across a saline boundary during the reproductive period and giving birth in a freshwater region of the river, or may have been affected by changes in physiology and elemental metabolism associated with reproduction.
URI: http://hdl.handle.net/2261/5594
ISSN: 13493000
出現カテゴリ:Coastal Marine Science
Coastal Marine Science


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