Although many notothenioid fishes are primarily carnivorous, some species consistently feed on macroalgae and are therefore omnivorous. Among fish, the degree of herbivory is usually reflected in the morphology of the gastrointestinal system especially intestine length. We examined a large number of juvenile and adult specimens of nine sympatric notothenioid species collected sequentially over eight summer seasons at Potter Cove, South Shetland Islands. We provide relative intestine lengths (RIL), distinct proportions of algae and animal prey in the diets (W%), and numbers of pyloric caeca for all species. The sister species Notothenia coriiceps (NOC) and N. rossii (NOR) evidenced significantly different intestinal growth over ontogeny and ate distinctly different proportions of algae and animal prey. We establish a ranking of the degree of herbivory for the fish species in the local ecosystem, and this was found to be related to their distinct feeding types and strategies. There is a correspondence between intestine length/RILs and degree of herbivory in six of the nine species analysed but no clear association between the number of pyloric caeca and degree of omnivory or carnivory. Compared to other teleosts, our results, and those in the literature, indicate modest divergence in notothenioids that include a phylogenetic decrease in the number of pyloric caeca, from 6 to 7 in most nototheniids to 2–3 in channichthyids, and a 1.8-fold difference in average relative intestine lengths which are most frequently 50–70% of body length and never exceed body length. This is consistent with the unspecialized gastrointestinal morphology that reflects the dietary and ecological plasticity of many notothenioids, exemplified by the high degree of omnivory in species such as NOC and NOR.

中文翻译：

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南极半岛西部九种拟鱼的食草程度和肠道形态

尽管许多拟鱼主要是肉食性的，但一些物种始终以大型藻类为食，因此是杂食性的。在鱼类中，食草性的程度通常反映在胃肠系统的形态，特别是肠的长度上。我们检查了在南设得兰群岛波特湾的八个夏季期间依次收集的九种同域notothenioid 物种的大量幼年和成年标本。我们提供相对肠道长度 (RIL)、饮食中藻类和动物猎物的不同比例 (W%) 以及所有物种的幽门盲肠数量。姐妹物种 Notothenia coriiceps (NOC) 和 N. rossii (NOR) 证明了个体发育过程中肠道生长的显着不同，并且食用了明显不同比例的藻类和动物猎物。我们建立了当地生态系统中鱼类的食草程度排名，发现这与它们独特的摄食类型和策略有关。在分析的 9 个物种中的 6 个物种中，肠道长度/RIL 与食草程度之间存在对应关系，但幽门盲肠数量与杂食性或肉食性程度之间没有明确关联。与其他硬骨鱼相比，我们的结果和文献中的结果表明，拟鱼科的差异不大，包括幽门盲肠数量的系统发育减少，从大多数拟鱼科的 6 到 7 到 channichthyids 的 2–3，以及 1.8 倍平均相对肠道长度的差异，最常见的是身体长度的 50-70%，从不超过身体长度。