THE MUDSKIPPER PERIOPHTHALMODON SCHLOSSERI RESPIRES MORE EFFICIENTLY ON LAND THAN IN WATER AND VICE-VERSA FOR BOLEOPHTHALMUS-BODDAERTI

The surface area-specific oxygen consumption rates of Periophthalmodon schlosseri and Boleophthalmus boddaerti were comparable when they wer e submerged in water. However, the oxygen consumption rate of P. schlo sseri increased significantly upon terrestrial exposure; Terrestrial e xposure also significantly increased the pO(2) level in the blood of P . schlosseri. Similar phenomena were not observed in B. boddaerti. The se results confirmed that P. schlosseri, due to its special branchial morphological and morphometric adaptation, could respire more efficien tly on land than in water. In addition, the blood pH of P. schlosseri became significantly more alkaline upon terrestrial exposure. This obs ervation is unique among fishes. It would appear that the increase in blood pH was due to an increase in the production of bicarbonate, alth ough the mechanism involved was uncertain. The various effects of terr estrial exposure on P. schlosseri could be reverted by resubmergence i n 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. Th is result indicates that P. schlosseri indeed had a higher metabolic r ate on land than in water. (C) 1998 Wiley-Liss, Inc.