Busst Georgina M A, Britton J Robert
Department of Life and Environmental Sciences, Faculty of Science and Technology, Bournemouth University, Poole BH12 5BB, UK.
Department of Life and Environmental Sciences, Faculty of Science and Technology, Bournemouth University, Poole BH12 5BB, UK
J Exp Biol. 2016 Apr;219(Pt 7):1060-8. doi: 10.1242/jeb.137380. Epub 2016 Feb 19.
Diet-tissue discrimination factors (Δ(13)C and Δ(15)N) are influenced by variables including the tissues being analysed and the taxon of the consumer and its prey. Whilst differences in Δ(13)C and Δ(15)N are apparent between herbivorous and piscivorous fishes, there is less known for omnivorous fishes that consume plant and animal material. Here, the omnivorous cyprinid fishes Barbus barbus and Squalius cephalus were held in tank aquaria and exposed to three diets that varied in their constituents (plant based to fishmeal based) and protein content (13% to 45%). After 100 days and isotopic replacement in fish tissues to 98%, samples of the food items, and dorsal muscle, fin tissue and scales were analysed for δ(13)C and δ(15)N. For both species and all diets, muscle was always enriched in δ(15)N and depleted in δ(13)C compared with fin tissue and scales. Across the different diets, Δ(13)C ranged between 2.0‰ and 5.6‰ and Δ(15)N ranged between 2.0‰ and 6.9‰. The diet based on plant material (20% protein) always resulted in the highest discrimination factors for each tissue, whilst the diet based on fishmeal (45% protein) consistently resulted in the lowest. The discrimination factors produced by non-fish diets were comparatively high compared with values in the literature, but were consistent with general patterns for some herbivorous fishes. These outputs suggest that the diet-tissue discrimination factors of omnivorous fishes will vary considerably between animal and plant prey, and these specific differences need consideration in predictions of their diet composition and trophic position.
饮食-组织判别因子（δ¹³C和δ¹⁵N）受多种变量影响，包括所分析的组织、消费者及其猎物的分类单元。虽然草食性和食鱼性鱼类之间的δ¹³C和δ¹⁵N差异明显，但对于既食用植物又食用动物物质的杂食性鱼类，人们了解较少。在此，将杂食性鲤科鱼类钝吻棒花鱼和意大利须鱥饲养在水族箱中，并让它们摄食三种成分（从植物性到鱼粉性）和蛋白质含量（13%至45%）各不相同的饲料。100天后，鱼组织中的同位素替换率达到98%，对食物样本以及背肌、鳍组织和鳞片进行δ¹³C和δ¹⁵N分析。对于这两个物种和所有饲料，与鳍组织和鳞片相比，肌肉中的δ¹⁵N始终富集，而δ¹³C则贫化。在不同饲料中，δ¹³C的变化范围在2.0‰至5.6‰之间，δ¹⁵N的变化范围在2.0‰至6.9‰之间。以植物性物质为基础（蛋白质含量20%）的饲料，每种组织的判别因子始终最高，而以鱼粉为基础（蛋白质含量45%）的饲料则始终导致最低判别因子。与文献中的值相比，非鱼类饲料产生的判别因子相对较高，但与一些草食性鱼类的一般模式一致。这些结果表明，杂食性鱼类的饮食-组织判别因子在动物和植物猎物之间会有很大差异，在预测它们的饮食组成和营养级时需要考虑这些特定差异。
