Nitrogen flux in giant clams: size-dependency and relationship to zooxanthellae density and clam biomass in the uptake of dissolved inorganic nitrogen
Nitrogen flux in giant clams: size-dependency and relationship to zooxanthellae density and clam biomass in the uptake of dissolved inorganic nitrogen
复制标题
巨蛤的氮通量：溶解无机氮吸收中的大小依赖性以及与虫黄藻密度和蛤生物量的关系
DOI：
10.1007/bf00349313
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发表时间：
1993
期刊：
影响因子：
2.4
通讯作者：
D. Yellowlees
中科院分区：
文献类型：
--
作者：
W. Fitt;T. Rees;R. Braley;J. Lucas;D. Yellowlees
砗磲蛤生活在印度洋-太平洋的珊瑚礁上，生活在无机氮浓度较低的水域。这项研究检测了巨型蛤砗磲蛤体内的氮通量。该物种的成虫和幼虫通常与共生双鞭毛虫属共生双鞭毛虫发生。通常被称为虫黄藻，它们生活在它们的组织中。完整的蛤吸收或释放溶解的无机氮（DIN），其通量的方向和大小取决于蛤的大小。非共生幼虫和虫黄藻较少的新定居幼体释放铵。当单独提供时，较大的幼鱼和成鱼从海水中消耗铵或硝酸盐。以蛤体湿重或虫黄藻数量为标准，小蛤体（1 ~ 5 cm）对DIN的吸收率最高，随着蛤体尺寸的增大（5 ~ 5 cm）而降低。在含高浓度铵（约20 μM）的海水中饲养≥1周的蛤蜊，通常在黑暗中释放铵，在光明中表现出净吸收。从小蛤中分离的虫黄藻（FIZ）比从大蛤中分离的虫黄藻（FIZ）吸收速率更高，这表明后者可能比前者更富氮。巨蛤体内的氮充足率梯度与虫黄藻密度有关，藻类密度和DIN吸收率的峰值都出现在小尺寸的蛤体内，其生长似乎也受到氮供应的限制。
Tridacnid clams live on coral reefs in the Indo-Pacific, in waters containing low concentrations of inorganic nitrogen. This study examined nitrogen flux in the giant clamTridacna gigas. Adults and juveniles of this species typically occur with symbiotic dinoflagellates of the genusSymbiodiniumsp., often referred to as zooxanthellae, which live in their tissues. Intact clams took up or released dissolved inorganic nitrogen (DIN), with the direction and magnitude of the fluxes dependent on clam size. Non-symbiotic larvae and newly-settled juveniles with few zooxanthellae released ammonium. Larger juveniles and adults depleted ammonium or nitrate from seawater, when offered separately. Rates of uptake of DIN, standardized to either clam wet weight or number of zooxanthellae, were highest in small clams (1 to 5 cm in length), and decreased with increasing clam size (>5 cm). Clams maintained in seawater containing high concentrations of ammonium (ca. 20 μM) for ≥ 1 wk generally released ammonium in the dark and exhibited net uptake in the light. Freshly isolated zooxanthellae (FIZ) from small clams had higher uptake rates than FIZ from larger clams, implying that the latter may be more nitrogen-sufficient than the former. The gradient of nitrogen sufficiency in giant clams is related to zooxanthellae density, with peaks of both algal density and rates of uptake of DIN occurring in small sizes of clams, whose growth also appears to be limited by nitrogen availability.