Nucleic acid and protein concentrations and their ratios are increasingly used as correlates of nutritional condition and growth in marine species. However, their application in studies of reptile growth has not yet been validated. The green turtle (Chelonia mydas) is an endangered marine reptile for which assessing population health requires knowledge of demographic parameters such as individual growth rates. The purpose of this study was to evaluate a number of biochemical indices ([DNA], [RNA], RNA:DNA ratio, [protein], protein:DNA ratio, and RNA:protein ratio) in liver, heart, and blood as potential predictors of recent growth rate in juvenile green turtles under controlled feeding conditions. Intake of juvenile green turtles was manipulated over twelve weeks to obtain a range of growth rates. With the exception of [RNA](blood), [DNA](heart), and [protein]:[DNA](liver), all biochemical indices demonstrated significant linear relationships with growth rate during the last 1.5 weeks of the study. The best single predictors of recent growth were hepatic [RNA] and [RNA]:[protein], which explained 66% and 49%, respectively, of the variance in growth. Contrary to expectations, these two indices were negatively correlated with growth rate. To investigate the possibility that hepatic [RNA] was higher in slow-growing turtles because of elevated expression of antioxidant genes, we quantified glutathione peroxidase activity and total antioxidant potential. Both measures of antioxidant function were affected by intake and growth histories, but these effects did not explain our results for hepatic RNA and protein concentrations. We developed a model that predicted 68% of the variance in specific growth rate (SGR) with the equation SGR = -0.913(ln[RNA](liver)) + 17.689(Condition Index) + 4.316. In addition, our findings that [DNA] and [RNA]:[DNA] for blood were significantly correlated with SGR demonstrate the potential utility of minimally invasive tissue sampling that could facilitate instantaneous population monitoring.

中文翻译：

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与幼年绿海龟（Chelonia mydas）近期生长相关的生化指数

核酸和蛋白质浓度及其比率越来越多地被用作海洋物种营养状况和生长的相关因素。然而，它们在爬行动物生长研究中的应用尚未得到验证。绿海龟 (Chelonia mydas) 是一种濒临灭绝的海洋爬行动物，评估种群健康需要了解人口参数，例如个体增长率。本研究的目的是评估肝脏、心脏和血液中的许多生化指标（[DNA]、[RNA]、RNA:DNA 比率、[蛋白质]、蛋白质:DNA 比率和 RNA:蛋白质比率），如在受控饲养条件下，青海龟近期增长率的潜在预测因子。对幼年绿海龟的摄入量进行了 12 周的控制，以获得一系列的增长率。除了[RNA]（血液），[DNA]（心脏），和[蛋白质]：[DNA]（肝脏），在研究的最后 1.5 周内，所有生化指标都显示出与生长速率显着的线性关系。近期生长的最佳单一预测因子​​是肝脏 [RNA] 和 [RNA]:[蛋白质]，它们分别解释了生长变化的 66% 和 49%。与预期相反，这两个指数与增长率呈负相关。为了研究由于抗氧化基因表达升高而导致生长缓慢的海龟肝脏 [RNA] 较高的可能性，我们量化了谷胱甘肽过氧化物酶活性和总抗氧化潜力。抗氧化功能的两种测量都受到摄入和生长历史的影响，但这些影响并不能解释我们对肝脏 RNA 和蛋白质浓度的结果。我们开发了一个模型，该模型预测特定增长率 (SGR) 的 68% 方差，公式为 SGR = -0.913(ln[RNA](liver)) + 17.689(Condition Index) + 4.316。此外，我们发现血液的 [DNA] 和 [RNA]:[DNA] 与 SGR 显着相关，这证明了微创组织取样的潜在效用，可以促进即时人口监测。