. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 01 234567 DURATION OF ESTIVATION (mo) Figure 6. Purine content during estivation in O slrignxu (O) and O. xuhriulix (•). Measurements were only made with snails that had been maintained in the laboratory- prior to estivation. All values have been adjusted to a snail of average size based upon shell diameter. A. Urate content. B. Guanine content. C. Xanthine content. Sample sizes are given in 6A in parentheses with the value for O strigosa appearing first. Bars indicate one standard error of the mean. in the medium increased
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 01 234567 DURATION OF ESTIVATION (mo) Figure 6. Purine content during estivation in O slrignxu (O) and O. xuhriulix (•). Measurements were only made with snails that had been maintained in the laboratory- prior to estivation. All values have been adjusted to a snail of average size based upon shell diameter. A. Urate content. B. Guanine content. C. Xanthine content. Sample sizes are given in 6A in parentheses with the value for O strigosa appearing first. Bars indicate one standard error of the mean. in the medium increased from 150 to 300 mM, the same range of concentrations across which survivorship de- creased sharply in Oreohelix. In other organisms that accumulate high levels of urea, there are also high levels of compounds that are capable of counteracting the potentially deleterious effects of urea (Yancey cl ai, 1982; Yancey, 1985). For example, in elas- mohranch fish, which display a tissue concentration of urea in this range, methylamine compounds occur in a 1:2 proportion with urea. At this ratio, methylamines are able to counteract the disruptive effects of high urea in vitro and are presumed to act this way in vivo. The me- thylamine content of estivating O. strigosa was low relative to urea. If methylamines were distributed uniformly in the tissue water, then their concentration would corre- spond to ± If methylamine compounds are concentrated intracellularly, as suggested by work with mammalian cells (Yancey and Burg, 1990), the intracel- lular concentration can approach 25 mM. Relative to the urea measured at this point in estivation, however, even 25 mAI methylamines is far below the ratio of 1:2 at which methylamine effects counteract the perturbation of mac- romolecules by urea. Thus, we offer the hypothesis that urea toxicity is a factor that limits the duration of estivation that can be tolerated by these two species of land snail. While higher levels of urea ha
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