美国科研人员捕捉到一种极不寻常的生物：一种以海藻为食并将海藻色素吸收到自身细胞中的海蜗牛。更令人惊讶的是，这种蜗牛不仅能借此进行很好的伪装，还能像植物一样进行光合作用以获取能量。
美国缅因州大学的蜗牛研究者发现，这种海蜗牛在生命初期以海藻为食，但却并不完全消化海藻，而是将其中的绿色素吸收进自己的细胞。它们吃的海藻越多，其颜色就变得越绿。
让研究者感到惊讶的是，这种蜗牛不仅能借此进行伪装，甚至还会从一种活性生命状态过渡到一种大体上的植物状态。因为一旦它们进食海藻变绿后，就能在没有任何食物的情况下生存数月之久。它们只靠水和自身体内绿色素通过光合作用制造的能量生存。
以詹姆斯·曼哈特为首的科研人员在《国家科学院学报》上撰文描述了这种名为Elysia chlorotica的海蜗牛。曼哈特说：“Elysia的生长需要海藻，没有海藻它们无法活下来。不过，一旦它们偷到充足的绿色素就会立即变成一种带有太阳能动力装置的动物。”
科学家认为，在遥远的未来，这种蜗牛甚至有可能将绿色素遗传给后代。到那时，它们就不必在生命的初始阶段进食海藻了，而且将成为第一种通过光合作用获取能量的动物。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS 2008 105:17867-17871;doi:10.1073/pnas.0804968105
Horizontal gene transfer of the algal nuclear gene psbO to the photosynthetic sea slug Elysia chlorotica
Mary E. Rumpho, Jared M. Worful, Jungho Lee, Krishna Kannan, Mary S. Tyler, Debashish Bhattacharya, Ahmed Moustafa, and James R. Manhart
The sea slug Elysia chlorotica acquires plastids by ingestion of its algal food source Vaucheria litorea. Organelles are sequestered in the mollusc's digestive epithelium, where they photosynthesize for months in the absence of algal nucleocytoplasm. This is perplexing because plastid metabolism depends on the nuclear genome for >90% of the needed proteins. Two possible explanations for the persistence of photosynthesis in the sea slug are (i) the ability of V. litoreaplastids to retain genetic autonomy and/or (ii) more likely, the mollusc provides the essential plastid proteins. Under the latter scenario, genes supporting photosynthesis have been acquired by the animal via horizontal gene transfer and the encoded proteins are retargeted to the plastid. We sequenced the plastid genome and confirmed that it lacks the full complement of genes required for photosynthesis. In support of the second scenario, we demonstrated that a nuclear gene of oxygenic photosynthesis, psbO, is expressed in the sea slug and has integrated into the germline. The source of psbO in the sea slug is V. litoreabecause this sequence is identical from the predator and prey genomes. Evidence that the transferred gene has integrated into sea slug nuclear DNA comes from the finding of a highly diverged psbO 3′ flanking sequence in the algal and mollusc nuclear homologues and gene absence from the mitochondrial genome of E. chlorotica.We demonstrate that foreign organelle retention generates metabolic novelty (“green animals”) and is explained by anastomosis of distinct branches of the tree of life driven by predation and horizontal gene transfer.
