Free amino acids and osmoregulation in the intertidal pulmonate Onchidium tumidium

The aim of this study is to elucidate the osmoregulatory capabilities of the intertidal pulmonate Onchidium tumidium. Our results indicate that O. tumidium could tolerate hyperosmotic stress more effectively than hypoosmotic stress. In 10% seawater (SW), it was capable of maintaining its plasma hype...

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Bibliographic Details
Published in:Marine biology 1999-09, Vol.134 (4), p.735-741
Main Authors: CHEW, S. F, HO, S. Y, IP, Y. K
Format: Article
Language:English
Subjects:
Amino acids
Animal and plant ecology
Animal, plant and microbial ecology
Animals
Autoecology
Biochemistry. Physiology. Immunology
Biological and medical sciences
Fundamental and applied biological sciences. Psychology
Invertebrates
Marine
Marine biology
Mollusca
Mollusks
Onchidium tumidium
Osmoregulation
Physiology. Development
Protozoa. Invertebrata
Pulmonata
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Summary:The aim of this study is to elucidate the osmoregulatory capabilities of the intertidal pulmonate Onchidium tumidium. Our results indicate that O. tumidium could tolerate hyperosmotic stress more effectively than hypoosmotic stress. In 10% seawater (SW), it was capable of maintaining its plasma hyperosmotic and hyperionic to the external medium. However, it rapidly gained weight in 10% SW, and no restoration of body weight was observed. In contrast, in 90% SW it was able to recover its body weight partially. In a hyperosmotic medium, accumulation of intracellular free amino acids (FAA) was responsible for cell volume regulation. The accumulated FAA might originate from protein catabolism, which occurred in the internal organs (IO). In contrast, the relatively smaller amination:deamination ratio of glutamate dehydrogenase in the body wall (BW) and IO of specimens exposed to hypoosmotic stress might lead to a higher rate of amino acid catabolism. This was supported by the greater ammonia contents in the BW and IO of, and higher rate of ammonia excretion by, specimens exposed to 10% SW.
ISSN:0025-3162
1432-1793
DOI:10.1007/s002270050590