Publication: A comparative study on the biochemical adaptations of the mudskippers, periophthalmodon schlosseri and boleophthalmus boddaerti when exposed to environmental hypercapnia
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Date
1999
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Abstract
Exposure of Periophihalmodon schlosseri and Boleophthalmus boddaerii to 6 h or 48 h of environmental hypercapnia (5% C02 in air) resulted in respiratory acidosis that was compensated for by an accumulation of HCO3 in the blood. The significant decrease in the plasma [CI] of B. boddaerii after 6 h and 48 h of hrpercapnia suggests a probable decrease in the activity of the branchid HCO3/Cl exchange mechanism. The concentration of total ammonia in the liver, muscle and blood plasma of B. boddaerii upon 48 h of hypercapnia showed significant decrease. Hence, B. boddaerii may not be utilizing unionized ammonia for acid base regulation.<br><br>Hypercapnic exposure did not impose adverse consequences on the metabolism of both mudskippers since the level of muscle glycogen and lactate and the energy charge of the muscle and liver remained unchanged. Moreover, the blood p02 level was not affected by hypercapnia, suggesting that anaerobic metabolism did not occur. Significant decrease in the muscle glutarnine, plasma aspartate and a significant twofold increase in the guanine levels in the muscle of P, schlosseri strongly suggests the involvement of de novo purine synthesis in the detoxification of C02. No such change was observed in B. boddaerii.<br><br>Therefore, it was hypothesized that P. schlosseri, being less efficient in aquatic respiration because of its terrestrially adapted gill morphology, has developed the ability to remove COz via de novo purine synthesis. B. boddoerti, on the other hand, did not exhibit such capability and might be more effective in removing C02 via conventional branchial means.