The whelk Neptunea arthritica (Buccinidae) is a common fishery species in Hokkaido, northern Japan. Although ecological information is needed for fisheries management, there is only one paper examining the foraging ecology of this species and it reported that N. arthritica preyed mainly on the invasive mussel Mytilus galloprovincialis. To date, no studies have examined utilization of native prey species by this whelk. Here, we report the findings of a study on the native prey utilization by N. arthritica in an area where M. galloprovincialis is not present. We conducted line transect sampling every month from May 2018 to May 2019 on the western coast of Hakodate Bay, southwestern Hokkaido, Japan. Prey items were composed mostly of gastropods (72%), followed by bivalves (24%) and only a small amount of carrion (<4%). Overlapping spatial distributions were observed among size classes of N. arthritica, while the prey utilization varied with body size. Small individuals (<30 mm in shell height) preyed mainly on the small colloniid gastropod Homalopoma sangarense, while larger individuals (>40 mm) preyed mainly on two tegulid gastropods (Chlorostoma lischkei and Omphalius rusticus) and two venerid bivalves (Protothaca euglypta and Ruditapes philippinarum). There were positive size relationships between whelk body size and prey size for prey categories (Vetigastropoda, Caenogastropoda and Bivalvia) and even for the same prey species (H. sangarense, O. rusticus and P. euglypta). These results suggest that N. arthritica is a predator of mobile gastropods, especially during its early life stage, in areas without the invasive Mediterranean mussel. It is possible that the foraging strategy of N. arthritica may differ quite markedly between areas with and without the invasive mussel.

中文翻译：

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海王星关节炎（Caenogastropoda：Buccinidae）的猎物利用：对腹足动物的捕食和与大小相关的变异

海王螺（Buccinidae）是日本北部北海道常见的渔业物种。尽管渔业管理需要生态信息，但只有一篇论文研究了该物种的觅食生态，并报道了关节炎猪笼草主要捕食入侵贻贝 Mytilus galloprovincialis。迄今为止，还没有研究检查过这种螺对本地猎物物种的利用。在这里，我们报告了一项关于 N. arthritica 在没有 M. galloprovincialis 的地区利用本地猎物的研究结果。我们于 2018 年 5 月至 2019 年 5 月每月在日本北海道西南部函馆湾西海岸进行线样带采样。猎物主要由腹足类动物（72%）组成，其次是双壳类动物（24%）和少量腐肉（<4%）。在关节炎猪笼草的大小类别中观察到重叠的空间分布，而猎物的利用率随体型的不同而变化。小型个体（壳高 < 30 毫米）主要捕食小型胶体腹足动物 Homalopoma sangarense，而大型个体（> 40 毫米）主要捕食两种腹足类动物（Chlorostoma lischkei 和 Omphalius rusticus）和两种带壳双壳贝类（Protothaca euglypta和菲律宾蛤仔）。对于猎物类别（Vetigastropoda、Caenogastropoda 和 Bivalvia），甚至对于相同的猎物物种（H. sangarense、O. rusticus 和 P. euglypta），螺体大小与猎物大小之间存在正大小关系。这些结果表明，关节炎猪笼草是移动腹足动物的捕食者，特别是在其早期生命阶段，在没有入侵地中海贻贝的地区。