Abstract
Among brackish T. obscurus, fresh water T. brevispinis, and marine T. trigonocephalus, there was a great difference in their osmotic regulation abilities, though they belong to the samegenus.
In particular, T. obscurus had the highest adaptability to sudden changes of environmental salinity. Conccntrations of Na+in plasma and musle and those of Cl-, NPN, ammoia and urea in muscle increased with the rise of environmental salinity. Increasing rate of nitrogen compounds was noticeably larger than that of other fish. These results suggest that nitrogen compounds probably play an important rote in osmotic regulation.
In addition, salinity of their habitat most likely brings about the difference of osmotic regulation abilities among these fish, and furthermore, these abilities vary according to the seasons.
