Osmoregulatory response to salinity changes in Boleophthalmus pectinirostris and Periophthalmus cantonensis

• Main Authors: Chu, Chwen-Mei, 朱純眉
• Other Authors: Hui-Chen Lin
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/55489861622977104754

碩士 === 東海大學 === 生物學系 === 87 === 英 文 摘 要 Euryhaline mudskippers in estuary mudflats have amphibious behavior. There are at least four species of mudskippers in Taiwan. They are Periophthalmus cantonensis, Boleophthalmus pectinirostris, Scartelaos viridis, and Scartelaos gigus. Periophthalmus cantonensis will escape from water onto rocks during high tide. Physiological studies also suggest that this amphibious behavior facilitates the maintenance of body fluid osmolality of P. cantonensis. On the other hand, B. pectinirostris would stay in water when tide rises. Based on these behavior observation, I hypothesized that B. pectinirostris are better in osmoregulation than P. cantonensis to environmental changes. The present study simulated environmental salinity change in the field. After being transferred from 35 gl-1 seawater to fresh water for 6 hr, mudskippers were transferred back to 35 gl-1 for another 6 hr. Their plasma Na+ level and gill Na+,K+-ATPase activity were sampled. The results showed that, with artificial salinity challenge, B. pectinirostriss still maintained a constant plasma osmolality either in under-water mode or in free-living mode. No significant change in Na+,K+-ATPase activities was found in free-living mode but there was a significant increase in under-water mode. Under the same experimental design, P. cantonensis managed to maintain a constant plasma osmolality when they were in free-living mode, but a fluctuation was observed in under-water mode. In addition, fish from both behavior modes varied in Na+,K+-ATPase activity. But the degree of change was more pronounced in under-water mode. When both species were compared at the same time, their plasma Na levels were not significantly different in free-living mode. But in under-water mode, P. cantonensis fluctuated in the plasma Na level. Similarly, the Na+,K+-ATPase activities of P. cantonensis oscillated more significantly than that of B. pectinirostris in under-water mode. However, the Na+,K+-ATPase activities of both species changed only slightly in free-living mode. In conclusion, these two species of mudskippers have different strategies in salinity adaptation. B. pectinirostris raises their gill Na+,K+-ATPase activities to maintain constancy in plasma osmolality, while P. cantonensis escapes from water in response to emvironmental salinity change.