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Cell volume regulation in the intertidal pulmonate, onchidium tumidium
Author
Ho, Soo Yin
Supervisor
Chew, Shit Fun
Abstract
Onchidium tumidium is an osmoconformer and that it is able to regulate its volume at 10% or 90% seawater (SW). However, it is a more effective volun2e regulator in 90% SW than in 10% SW. Results indicate that after an upward transfer from 50% to 90% SW, there were significant increases in the total free amino acids (TFAA) in the whole animal, coelomic plasma (CP), body wall (BW) and internal organs (10). Increased proteolysis was more likely to occur in the I0 than in the BW of 0. tumidium exposed to 90% SW as reflected by a lowered water-soluble protein content in the I0 of slugs exposed to 90% SW compared to those of slugs exposed to 50% SW. It is probable that the higher TFAA in the BW of O.tumidium exposed to 90% SW compared to that of slugs exposed to 50% SW was partially due to NH4+ trapping by α-ketoglutarate in the presence of glutamate dehydrogenase to form glutamate as indicated by a significantly higher amination deamination-1 ratio. Glutamate could then be channeled to form other amino acids via transaminases. When being confronted with a downward transfer from 50% SW to 10% SW, there was possibly a release of free amino acids (FAA) from the BW of 0. tumidium into the CP as indicated by the increase in TFAA in the CP and a decrease in TFAA in the BW. The significantly lower amination deamination-1 ratio in the I0 shows that it is most probably involved in the breakdown of FAA during hypoosmotic stress.
Date Issued
1996
Call Number
QH604 Ho
Date Submitted
1996