Studying the diet of crustaceans based on the direct visual inspection of the gut contents can be difficult because they can ingest only a portion of the prey and further crush it into very small pieces, making a very few food items identifiable. Here, the usefulness of molecular methods to identify the species present in the gut contents of two crustaceans, the shore crab Carcinus maenas and the brown shrimp Crangon crangon, was tested. Stomach contents were removed, and their total genomic DNA extracted followed by amplification (PCR) with four specific prey mtDNA primers. Since both crustaceans are opportunistic predators, preying upon around 40 different species, the study was restricted to common potential preys in the sampled area, the Minho Estuary (Portugal): the common goby Pomatoschistus microps, the ragworm Hediste diversicolor, the flounder Platichthys flesus and the peppery furrow shell Scrobicularia plana. After testing the most appropriate methodology for DNA extraction and PCR amplification to detect the presence of each potential prey with positive control samples, the same methodology was applied to the stomach content samples. The molecular methods allowed for detection of the presence of P. microps, P. flesus and H. diversicolor in the stomachs of both crustaceans. Therefore, once potential prey and their availability in the system are known, PCR technique can be an alternative tool to overcome some of the limitations of traditional methods in the study of the crustaceans’ diet, even when stomach contents include a great part of ‘detritus’. This study reflects also the need to develop more tools (primers) to improve the assessment of predator–prey interactions in aquatic ecosytems.

根据肉眼内脏成分的直接肉眼检查来研究甲壳类动物的饮食可能很困难，因为它们只能摄入一部分猎物并将其进一步粉碎成非常小的碎片，从而使很少的食物可以识别。在这里，测试了分子方法对鉴定两个甲壳类动物岸蟹Carcinus maenas和棕色虾Crangon crangon的肠道含量中存在的物种的有用性。去除胃中的内容物，提取其总基因组DNA，然后用四种特异性猎物mtDNA引物进行扩增（PCR）。由于两个甲壳类动物都是机会性掠食者，它们捕食大约40种不同的物种，因此该研究仅限于采样区Minho Estuary（葡萄牙）的常见潜在猎物：普通虾虎鱼Pomatoschistus菌，杂虫Hediste diversicolor，比目鱼Platichthys flesus和胡椒沟壳Scrobicularia。在测试了最合适的DNA提取和PCR扩增方法以检测阳性对照样品中每种潜在猎物的存在之后，将相同的方法应用于胃内容物样品。分子方法可用于检测假单胞菌，实蝇和杂色杆菌的存在在两个甲壳动物的肚子里。因此，一旦知道了潜在的猎物及其在系统中的可用性，PCR技术就可以克服传统方法在甲壳类动物饮食研究中的某些局限性，即使在胃中含有大量“碎屑”的情况下'。这项研究还反映了需要开发更多的工具（引物）来改善对水生生态系统中捕食者与猎物相互作用的评估。