Zoologisches Forschungsmuseum Alexander Koenig, Adenauerallee 160, 53113 Bonn, Germany.
Front Zool. 2014 Jan 16;11(1):5. doi: 10.1186/1742-9994-11-5.
The Mediterranean sacoglossan Elysia timida is one of the few sea slug species with the ability to sequester chloroplasts from its food algae and to subsequently store them in a functional state in the digestive gland cells for more than a month, during which time the plastids retain high photosynthetic activity (= long-term retention). Adult E. timida have been described to feed on the unicellular alga Acetabularia acetabulum in their natural environment. The suitability of E. timida as a laboratory model culture system including its food source was studied.
In contrast to the literature reporting that juvenile E. timida feed on Cladophora dalmatica first, and later on switch to the adult diet A. acetabulum, the juveniles in this study fed directly on A. acetabulum (young, non-calcified stalks); they did not feed on the various Cladophora spp. (collected from the sea or laboratory culture) offered. This could possibly hint to cryptic speciation with no clear morphological differences, but incipient ecological differentiation. Transmission electron microscopy of chloroplasts from A. acetabulum after initial intake by juvenile E. timida showed different states of degradation - in conglomerations or singularly - and fragments of phagosome membranes, but differed from kleptoplast images of C. dalmatica in juvenile E. timida from the literature. Based on the finding that the whole life cycle of E. timida can be completed with A. acetabulum as the sole food source, a laboratory culture system was established. An experiment with PAM-fluorometry showed that cultured E. timida are also able to store chloroplasts in long-term retention from Acetabularia peniculus, which stems from the Indo-Pacific and is not abundant in the natural environment of E. timida. Variations between three experiment groups indicated potential influences of temperature on photosynthetic capacities.
E. timida is a viable laboratory model system to study photosynthesis in incorporated chloroplasts (kleptoplasts). Capacities of chloroplast incorporation in E. timida were investigated in a closed laboratory culture system with two different chloroplast donors and over extended time periods about threefold longer than previously reported.
地中海袋海牛（Elysia timida）是少数几种能够从食物藻类中摄取叶绿体并将其储存在消化腺细胞中保持功能状态超过一个月的海蛞蝓物种之一，在此期间，质体保持高光合作用活性（即长期保留）。在自然环境中，成年的 E. timida 被描述为以单细胞藻类 Acetabularia acetabulum 为食。本研究旨在探讨 E. timida 作为实验室模型培养系统及其食物来源的适宜性。
与文献报道的幼体 E. timida 首先以 Cladophora dalmatica 为食，然后转而以成体饮食 A. acetabulum 为食不同，本研究中的幼体直接以 A. acetabulum（年轻的、非钙化的茎）为食；它们不以提供的各种 Cladophora spp.（从海洋或实验室培养中收集）为食。这可能暗示着没有明显形态差异的隐种形成，但存在初步的生态分化。用透射电子显微镜观察幼年 E. timida 最初摄入的 A. acetabulum 叶绿体显示出不同的降解状态——聚集或单独存在——以及吞噬体膜的片段，但与文献中幼年 E. timida 中 Cladophora dalmatica 的盗食质体图像不同。基于发现 E. timida 的整个生命周期可以仅以 A. acetabulum 为唯一食物来源完成的这一发现，建立了一个实验室培养系统。用 PAM 荧光法进行的实验表明，培养的 E. timida 也能够从属于印度洋-太平洋地区且在 E. timida 的自然环境中并不丰富的 Acetabularia peniculus 中储存长期保留的叶绿体。三个实验组之间的差异表明温度对光合作用能力可能有影响。
E. timida 是研究嵌入叶绿体（盗食质体）光合作用的可行实验室模型系统。在一个封闭的实验室培养系统中，用两种不同的叶绿体供体和比以前报道的时间延长三倍多的时间，研究了 E. timida 中叶绿体的整合能力。
