一项研究发现，一个古老的化石蚊子的腹中含有它最后吸的血，这证实了这些昆虫在4600万年前以血为食。大约1.4万种现存的昆虫吸血，包括跳蚤、蜱和蚊子。尽管这种觅食策略看上去在一批生物中间独立进化出来，这种行为的化石证据罕见。Dale Greenwalt及其同事报告的证据显示一只来自美国蒙大拿西北部的吸饱了血的蚊子在进食之后不久死去，并且从中始新世以来就保存在页岩中。在这个昆虫的腹部发现了高浓度的铁之后，这组科研人员用一种称为非破坏性质谱法的技术分析了这个样本，并且发现了铁的来源是血红素，即让血红蛋白能够输送氧的分子实体。这组作者报告说，尽管诸如DNA等大而脆弱的分子通常不会在石化过程中存在下来，这只古蚊子证实了某些复杂的有机分子，诸如血红素，在适宜的条件下可以长期保存。此外，这组作者说，这些发现把这个昆虫家族以血为食的化石记录延长了4600万年（生物谷Bioon.com）。
生物谷推荐的英文摘要
Proceedings of the National Academy of the Sciences of the United States of America doi: 10.1073/pnas.1310885110
Hemoglobin-derived porphyrins preserved in a Middle Eocene blood-engorged mosquito
Dale E. Greenwalta，1， Yulia S. Gorevab， Sandra M. Siljestromb，c，d， Tim Roseb， and Ralph E. Harbache
Although hematophagy is found in ～14，000 species of extant insects， the fossil record of blood-feeding insects is extremely poor and largely confined to specimens identified as hematophagic based on their taxonomic affinities with extant hematophagic insects； direct evidence of hematophagy is limited to four insect fossils in which trypanosomes and the malarial protozoan Plasmodium have been found. Here， we describe a blood-engorged mosquito from the Middle Eocene Kishenehn Formation in Montana. This unique specimen provided the opportunity to ask whether or not hemoglobin， or biomolecules derived from hemoglobin， were preserved in the fossilized blood meal. The abdomen of the fossil mosquito was shown to contain very high levels of iron， and mass spectrometry data provided a convincing identification of porphyrin molecules derived from the oxygen-carrying heme moiety of hemoglobin. These data confirm the existence of taphonomic conditions conducive to the preservation of biomolecules through deep time and support previous reports of the existence of heme-derived porphyrins in terrestrial fossils.
