Ibarrola I, Navarro E, Urrutia MB
Departamento de Biología Animal y Genética, Facultad de Ciencias, Universidad del País Vasco/Euskal Herriko Unibertsitatea, Apartado 644, E-48080, Bilbao, Spain
J Exp Mar Biol Ecol. 2000 Sep 20;252(2):181-198. doi: 10.1016/s0022-0981(00)00233-1.
Cockles Cerastoderma edule were fed two different concentrations ( approximately 0.8 and 2 mm(3) l(-1)) of two diets with different qualities ( approximately 10 and 60% of organic content) which were achieved by mixing different proportions of ashed silt particles with cells of the microalgae Tetraselmis suecica. Clearance, ingestion and absorption rates of organic matter and biochemical components were measured after 3 days (acute response) and 11 days (acclimated response) of exposure to the diets. With low quality diets cockles were found to reject part of the filtered matter ( approximately 25-35%) through pseudofaeces production both in the acute and acclimated responses. In the acute response, absorption rate of organic matter was positively dependent on food quality and quantity, but the physiological response to increasing food concentrations differed with food quality: with low qualities, increasing absorption rate resulted from the simultaneous increase of clearance ( approximately 2 times) and ingestion rate ( approximately 4 times) as well as absorption efficiency of organic matter ( approximately 22%). However, those fed high qualities, were found to compensate increasing food concentration by reducing ( approximately 50%) clearance rate. The resulting moderate increase of ingestion rate ( approximately 1.6 times) was accompanied with a reduction in absorption efficiency ( approximately 20%). Irrespective of food quality and quantity, protein and lipids were absorbed, respectively, with the highest (from 61.7 to 80.0%) and the lowest (from 42.6 to 66.8%) efficiency. Acclimated response was entirely affected by food quality: with low qualities, cockles greatly improved the energetic intake from available ration ( approximately 4 and 2 times, with low and high food concentrations, respectively). Both preingestive and digestive mechanisms were involved in this response: at the preingestive level, clearance rate and preingestive selection efficiency were significantly increased. At the digestive level, cockles were capable of maintaining absorption efficiency of organic matter with rising ingestion rate. On the contrary, acclimation to high quality diets brought about no significant increase in organic absorption rate: with low ration, clearance rate was kept constant, whereas with high ration the increase in clearance and ingestion rate ( approximately 2 times) promoted a compensatory reduction in absorption efficiency. However, the biochemical composition of the absorbed matter was found to be absolutely modified, both at low and high food rations, due to an strong reduction of lipid absorption efficiency. The observed modifications of absorption rate and/or the biochemical composition of the absorbed matter suggests the capability of cockles to adjust the digestive performance.
用两种不同质量（有机含量分别约为10%和60%）的饲料以两种不同浓度（约0.8和2立方毫米/升）投喂鸟蛤（Cerastoderma edule），这两种饲料是通过将不同比例的灰化淤泥颗粒与微藻四爿藻（Tetraselmis suecica）细胞混合制成的。在暴露于饲料3天（急性反应）和11天（适应反应）后，测量了有机物和生化成分的清除率、摄食率和吸收率。发现对于低质量饲料，鸟蛤在急性反应和适应反应中都会通过产生假粪便排出部分过滤物质（约25 - 35%）。在急性反应中，有机物的吸收率与食物质量和数量呈正相关，但对食物浓度增加的生理反应因食物质量而异：对于低质量饲料，吸收率的增加是由于清除率（约2倍）、摄食率（约4倍）以及有机物吸收效率（约22%）同时增加。然而，对于投喂高质量饲料的鸟蛤，发现它们通过降低（约50%）清除率来补偿食物浓度的增加。摄食率适度增加（约1.6倍）的同时吸收效率降低（约20%）。无论食物质量和数量如何，蛋白质和脂质的吸收效率分别最高（从61.7%到80.0%）和最低（从42.6%到66.8%）。适应反应完全受食物质量影响：对于低质量饲料，鸟蛤大大提高了从可利用食物量中的能量摄入（低食物浓度和高食物浓度时分别约为4倍和2倍）。这种反应涉及摄食前和消化机制：在摄食前水平，清除率和摄食前选择效率显著提高。在消化水平，鸟蛤能够随着摄食率的增加维持有机物的吸收效率。相反，适应高质量饲料并没有使有机物吸收率显著增加：食物量低时，清除率保持不变，而食物量高时，清除率和摄食率的增加（约2倍）导致吸收效率的补偿性降低。然而，由于脂质吸收效率大幅降低，在低食物量和高食物量时，所吸收物质的生化组成都发生了绝对改变。观察到的吸收率和/或所吸收物质生化组成的变化表明鸟蛤有能力调节消化性能。
