Nitrogen metabolism and excretion in Allenbatrachus grunniens (L): Effects of variable salinity, confinement, high pH and ammonia loading

P. J. Walsh, Z. Wei, C. M. Wood, A. M. Loong, K. C. Hiong, S. M.L. Lee, W. P. Wong, S. F. Chew, Y. K. Ip

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

The nitrogen metabolism and excretion patterns of the grunting toadfish Allenbatrachus grunniens and the effects of salinity on these processes were examined. Individuals of A. grunniens were subjected to several experimental treatments, including variable salinity (2 to 30), high pH (8.5 compared to 7.0 for controls), high environmental ammonia (10 mM) and confinement to small water volumes, and measurements were made of activities of selected enzymes of nitrogen metabolism, ammonia and urea excretion rates, and tissue and plasma contents of ammonia, urea and amino acids. Activities of key ornithine-urea cycle enzymes were rather low (e.g. liver carbamoyl phosphate synthetase III activity was 0-001 μmols min-1 g-1), and A. grunniens consistently demonstrated a low capacity for urea excretion despite significant elevations of plasma and tissue ammonia contents by the high pH and high ammonia treatments. This species could thus be categorized as ammoniotelic. Total free amino acid contents in plasma and tissues were increased by the high pH and high ammonia treatments, but no patterns were discerned in individual amino acids that would indicate any preferential accumulation (e.g. alanine and glutamine) as has been noted previously in several semi-terrestrial fish species. Thus, it appeared that A. grunniens was not unusual in its patterns of nitrogen metabolism and excretion in comparison to other 'typical' teleosts. Furthermore, manipulation of salinity had no major effects on nitrogen excretion in either this species or in comparative studies with the ureotelic gulf toadfish Opsanus beta. The results are discussed in the context of the broader pattern of nitrogen metabolism and excretion in the Batrachoididae.

Original languageEnglish (US)
Pages (from-to)1392-1411
Number of pages20
JournalJournal of Fish Biology
Volume65
Issue number5
DOIs
StatePublished - Nov 2004

Keywords

  • Allenbatrachus grunniens
  • Ammoniotely
  • Batrachoididae
  • Carbamoyl phosphate synthetase
  • Ornithine-urea cycle
  • Ureotely

ASJC Scopus subject areas

  • Aquatic Science

Fingerprint Dive into the research topics of 'Nitrogen metabolism and excretion in Allenbatrachus grunniens (L): Effects of variable salinity, confinement, high pH and ammonia loading'. Together they form a unique fingerprint.

Cite this