Cellulose digestion abilities determine the food utilization of mangrove estuarine crabs
Cellulose digestion abilities determine the food utilization of mangrove estuarine crabs
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DOI：
10.1016/j.ecss.2019.04.004
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发表时间：
2019-06-30
影响因子：
2.8
通讯作者：
Sano, Mitsuhiko
中科院分区：
文献类型：
--
作者：
Kawaida, Shun;Nanjo, Kusuto;Sano, Mitsuhiko
通过对6种螃蟹的食物利用和纤维素消化能力的研究，阐明了日本南部伊利奥莫特岛乌拉口河红树林河口物种间营养和空间分离的驱动机制。3种微生境(裸滩、裸滩和红树林)的优势蟹种的双重稳定同位素特征(Delta C-13和Delta N-15)表明，大多数种类的蟹类，如中华绒螯蟹和中华绒螯蟹，主要是同化的微型底栖动物(MPB)，而红树林内的芝麻蟹Parasesarma Bidens大量利用富含纤维素的红树林碎屑和树叶。沉积物有机质的化学性质分析表明，沉积物有机质主要由红树林碎屑组成，泥质滩地和森林中的红树林碎屑比沙质滩地更为丰富。相比之下，MPB在每个微生境中的现存量一直处于较低水平，特别是在红树林内，而不是在裸露的平地上。酶活性测定表明，鬼针草具有较高的纤维素酶活性，使该物种能够利用难降解的红树林物质，而其他纤维素酶活性较低的蟹类高度依赖营养丰富且易降解的MPB，尽管后者在红树林河口的数量很少。这些发现表明，富含纤维素的植物材料作为碳源的同化效率取决于纤维素酶活性水平，本质上控制着红树林河口蟹类之间的营养和空间隔离。考虑到植物碎屑的生物量较大，鬼针草很可能通过有效地消化/同化纤维素物质，在红树林生态系统中建立碎屑食物链中发挥不可或缺的作用。
Food utilization and cellulose digestion abilities of six crab species were examined to clarify the mechanisms driving trophic and spatial segregation among species within a mangrove estuary on the Urauchi River, Iriomote Island, southern Japan. Dual stable isotope signatures (delta C-13 and delta N-15) of dominant crab species inhabiting three microhabitats (bare sandy flat, bare muddy flat and mangrove forest) showed that most crab species, such as the soldier crab Mictyris guinotae and fiddler crab Gelasimus jocelynae, primarily assimilated microphytobenthos (MPB), while the sesarmid crab Parasesarma bidens inside the mangrove forest substantially utilized cellulose-rich mangrove detritus and leaf litter. Analyses of the chemical properties of sediment organic matter indicated that it comprised mainly mangrove detritus, which was more abundant on the muddy flat and in the forest compared to the sandy flat. In contrast, the standing stocks of MPB were at consistently low levels in each microhabitat, particularly inside the mangrove forest than on the bare flats. The enzyme assay revealed that P. bidens exhibited much higher cellulase activity, enabling the species to utilize refractory mangrove materials, whereas the other crab species with lower cellulase activity were highly dependent upon nutritious and easily degradable MPB, although the amount of the latter was largely limited in the mangrove estuary. These findings suggested that the assimilation efficiency of cellulose-rich plant materials as a carbon source, dependent upon the level of cellulase activity, essentially controls trophic and spatial segregation among crab species in the mangrove estuary. Given the greater biomass of plant detritus, it is likely that P. bidens plays an integral part in establishing the detritus food chain in the mangrove ecosystem through the effective digestion/assimilation of cellulose materials.