Options
Nitrogen metabolism and excretion in the snakehead, channa asiatica, during terrestrial exposure
Author
Wong, Mei Yee
Supervisor
Chew, Shit Fun
Abstract
The snakehead, Channa asiatica, is a predaceous fish that resides in slow-flowing streams and crevices of riverbanks. During periods of low tide, the fish may be trapped in crevices and thus exposed to terrestrial conditions. Also, C. asiatica is also capable of eel-like movement on land. Thus, the fish might thus be subjected to voluntary terrestrial exposure in the course of it's life.
Nitrogenous waste excretion will be impeded in the absence of gill irrigation. In order to survive such exposure, C. asiatica must thus adopt strategies of alternative nitrogenous waste excretion or detoxification.
To investigate possible strategies adopted by C. asiatica, the fish was exposed to terrestrial conditions for various periods. After which, related end products like urea, ammonia and free amino acids are assayed, together with selected enzymes involved in the metabolism of the mentioned end products. Such enzymes include enzymes of the omithine-urea cycle and transaminases.
The rate of ammonia excretion of Channa asiarica exposed to terrestrial condition was reduced to one-fourth that of the submerged control. C. asiatica accumulated significantly higher levels of ammonia in the muscle, liver and plasma after different periods of terrestrial exposure. C. asiatica does not possess a complete ornithine-urea cycle. During terrestrial exposure, ammonia was not converted to urea. Instead, asparagine, glutamine and alanine were formed. The alanine content increased to nine times that of the submerged control in the muscle. The activities of alanine transaminase (ALT) and glutamate dehydrogenase indicate that alanine was formed from partial catabolism of amino acids via glutamate. The presence of malic enzyme suggests the pyruvate that forms alanine may arise from malate in the Kreb's cycle. Results of the mass-action ratio of ALT might indicate the possibility of the presence of different isozymes of ALT or the conversion of L-alanine to D-alanine during terrestrial exposure.
Nitrogenous waste excretion will be impeded in the absence of gill irrigation. In order to survive such exposure, C. asiatica must thus adopt strategies of alternative nitrogenous waste excretion or detoxification.
To investigate possible strategies adopted by C. asiatica, the fish was exposed to terrestrial conditions for various periods. After which, related end products like urea, ammonia and free amino acids are assayed, together with selected enzymes involved in the metabolism of the mentioned end products. Such enzymes include enzymes of the omithine-urea cycle and transaminases.
The rate of ammonia excretion of Channa asiarica exposed to terrestrial condition was reduced to one-fourth that of the submerged control. C. asiatica accumulated significantly higher levels of ammonia in the muscle, liver and plasma after different periods of terrestrial exposure. C. asiatica does not possess a complete ornithine-urea cycle. During terrestrial exposure, ammonia was not converted to urea. Instead, asparagine, glutamine and alanine were formed. The alanine content increased to nine times that of the submerged control in the muscle. The activities of alanine transaminase (ALT) and glutamate dehydrogenase indicate that alanine was formed from partial catabolism of amino acids via glutamate. The presence of malic enzyme suggests the pyruvate that forms alanine may arise from malate in the Kreb's cycle. Results of the mass-action ratio of ALT might indicate the possibility of the presence of different isozymes of ALT or the conversion of L-alanine to D-alanine during terrestrial exposure.
Date Issued
1999
Call Number
QL639.1 Won
Date Submitted
1999