| Abstract: | 中 文 摘 要 彈塗魚是生活於潮間帶的魚種，為廣鹽性魚類。彈塗魚有兩棲性行為，能自由活動於水中及泥地上。在台灣至少共有三屬四種彈塗魚，分別為跳彈塗(Periophthalmus cantonensis)、大彈塗(Boleophthalmus pectinirostris)、青彈塗(Scartelaos viridis)及大青彈塗(Scartelaos gigus)。前人研究指出，跳彈塗在面臨漲退潮鹽度變化時，會離開水中到岩石上。生理的研究也證實，跳彈塗離水的行為有助於維持體內滲透壓的恆定；相較之下，大彈塗在面臨漲退潮鹽度變化的情況，並不以離水行為逃避環境中鹽度的變動，是否表示大彈塗在水中具有較佳的滲透壓調節能力，是本實驗所要探討的重點。本實驗模擬環境鹽度的變化，先由35g/l 海水轉移至淡水6小時後，再次轉移至35g/l 海水6小時，並在各時間點測彈塗魚的血液鈉離子含量及鰓部Na+,K+-ATPase活性變化，實驗結果顯示：（一）大彈塗在面臨模擬環境鹽度轉移時，血液中鈉離子濃度不論在何種行為模式下，大都維持一穩定狀態；在Na+,K+-ATPase活性方面，自由出入水面組並無顯著變化，但在完全抑制於水面下組中，轉移至淡水的第6小時及再轉移至海水後的 2 小時，活性有顯著上升；（二）跳彈塗同樣面臨模擬環境鹽度轉移時，血液中鈉離子濃度在自由出入水面組，皆維持一穩定狀態，在完全抑制於水面下組，則會隨環境鹽度改變而變化；在 Na+,K+-ATPase活性方面，不論何者行為模式，活性都會隨環境鹽度變化而改變，但自由出入水面組變化幅度較小；（三）將大彈塗及跳彈塗做一比較，在自由出入水面處理方式下，血液鈉離子濃度變化並無顯著差異；在完全抑制於水面下處理組，跳彈塗的變化幅度大於大彈塗；在 Na+,K+-ATPase活性方面，在自由出入水面組的兩種魚之間，變化幅度都不大，但是在完全抑制於水面下組，跳彈塗的變動幅度大於大彈塗的變動。由上述的實驗中，可以說明大彈塗在面臨鹽度急遽變化（例如漲潮時），體內會自然產生 Na+,K+-ATPase來維持體內的滲透壓，而跳彈塗則是利用逃離鹽度的行為來維持體內滲透壓。
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. |
