The mudskipperPeriophthalmodon schlosseri respires more efficiently on land than in water and vice versa forBoleophthalmus boddaerti

Abstract

The surface area–specific oxygen consumption rates of Periophthalmodon schlosseri and Boleophthalmus boddaerti were comparable when they were submerged in water. However, the oxygen consumption rate of P. schlosseri increased significantly upon terrestrial exposure. Terrestrial exposure also significantly increased the pO2 level in the blood of P. schlosseri. Similar phenomena were not observed in B. boddaerti. These results confirmed that P. schlosseri, due to its special branchial morphological and morphometric adaptation, could respire more efficiently on land than in water. In addition, the blood pH of P. schlosseri became significantly more alkaline upon terrestrial exposure. This observation is unique among fishes. It would appear that the increase in blood pH was due to an increase in the production of bicarbonate, although the mechanism involved was uncertain. The various effects of terrestrial exposure on P. schlosseri could be reverted by resubmergence in water. On land, P. schlosseri had a heart rate of 55 beats · min–1. The rate decreased to 11 beats · min–1 within 5 min of submergence. This result indicates that P. schlosseri indeed had a higher metabolic rate on land than in water. J. Exp. Zool. 280:86–90, 1998. © 1998 Wiley-Liss, Inc.