BACKGROUND About 4 x 10(5) eggs in more than 5000 marine turtle nests are deposited every year on a 3.6 km long beach in French Guiana (South America). The dry biomass of eggs is estimated to be 5 x 10(3) kg, yet only 25% of this organic matter will return to the ocean in the form of hatchlings. Such amounts of organic matter are supposed to drive the functioning of the beach ecosystem. Previous studies have shown that egg predators and detritivorous organisms dominate the trophic relationships and the dynamics of the system. The role of a terrestrial insect Scapteriscus didactylus (Latreille), which damages up to 40% of the eggs of the marine turtle (Dermochelys coriacea), was unexpected. However it was impossible from direct observations to prove that the mole cricket consumed a significant amount of these eggs. Therefore, the precise place of the mole cricket in the nitrogen and carbon cycles of the beach ecosystem could not be determined. In order to answer this question, we looked for a marine signature of carbon and nitrogen source metabolized by the mole cricket. RESULTS This study estimated the individual variability of delta13C and delta15N in the cuticle of Scapteriscus didactylus. The isotopic signature was compared between individuals collected at two sites: a village where mole crickets fed on human food scraps and the nearby Awala-Yalimapo beach, where food availability depends seasonally on the nesting sea turtles. The mole crickets collected near the habitations garbage showed no significant variations in the stable isotopic signature, within-and between age groups. On the contrary, isotopic values shifted from a signature of a terrestrial herbivorous diet in the mole crickets during early developmental stages, to isotopic values in adults in accordance with the exploitation of marine animal resources. CONCLUSION The heterogeneity of individual signatures during the year is due to a selective exploitation of the food sources, differing in space and time. Some individuals, from the beach sample consumed a sufficient quantity of turtle eggs to induce the increase of isotopic enrichment observed in the cuticle. Scapteriscus didactylus is an opportunist feeder and plays a role in the turn over of the beach organic matter.

中文翻译：

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通过陆生昆虫 Scapteriscus didactylus 角质层的稳定同位素分析证明其开发海洋资源的证据。


背景技术每年，在法属圭亚那（南美洲）3.6公里长的海滩上，有超过5000个海龟巢中会产下大约4 x 10(5)个海龟蛋。蛋的干生物量估计为 5 x 10(3) kg，但其中只有 25% 的有机物质会以幼体的形式返回海洋。如此大量的有机物应该能够推动海滩生态系统的运转。先前的研究表明，卵捕食者和食腐生物主导着系统的营养关系和动态。陆生昆虫 Scapteriscus didactylus (Latreille) 的作用是出人意料的，它会损害海龟 (Dermochelys coriacea) 40% 的卵。然而，通过直接观察不可能证明蝼蛄消耗了大量的这些卵。因此，无法确定蝼蛄在海滩生态系统氮和碳循环中的精确位置。为了回答这个问题，我们寻找蝼蛄代谢的碳源和氮源的海洋特征。结果本研究评估了 Scapteriscus didactylus 角质层中 delta13C 和 delta15N 的个体变异性。对在两个地点收集的个体进行了同位素特征比较：一个村庄，蝼蛄以人类食物残渣为食；另一个地点是附近的阿瓦拉-亚丽马波海滩，那里的食物供应季节性取决于筑巢的海龟。在居住区垃圾附近收集的蝼蛄在年龄组内和年龄组之间的稳定同位素特征没有显着变化。 相反，同位素值从蝼蛄在早期发育阶段的陆地草食性饮食的特征转变为与海洋动物资源的开发相一致的成虫的同位素值。结论 年内个体特征的异质性是由于对食物来源的选择性利用、空间和时间的不同造成的。海滩样本中的一些个体消耗了足够数量的海龟蛋，以诱导角质层中观察到的同位素富集增加。 Scapteriscus didactylus 是一种机会主义饲养者，在海滩有机物的周转中发挥着作用。