Data from: Predation on feather stars by regular echinoids as evidenced by laboratory and field observations and its paleobiological implications

Among extant crinoids, the feather stars are the most diverse and occupy the greatest bathymetric range, being especially common in reef environments. Feather stars possess a variety of morphological, behavioral and physiological traits that have been hypothesized to be critical to their success, especially in their ability to cope with predation. However, knowledge of their predators is exceptionally scant, consisting primarily of circumstantial evidence of attacks by fishes. In this study the question whether regular echinoids, recently shown to consume stalked crinoids, also consume feather stars is explored. Aquarium observations indicate that regular echinoids find feather stars palatable, including feather stars known to be distasteful to fish, and that regular echinoids can capture and eat live feather stars, including those known to swim. Gut-content analyses of the echinoid Araeosoma fenestratum (Thomson, 1872), which is commonly observed with large populations of the feather star Koehlermetra porrecta (Carpenter, 1888) in video transects from marine canyons off the coast of France, revealed elements of feather stars in the guts of 6 of 13 individuals. The high proportion of crinoid material (up to 90%), and the presence of articulated crinoid skeletal elements in the gut of A. fenestratum, suggest that these echinoids consumed at least some live crinoids, although they may have also ingested some postmortem remains found in the sediment. Additionally, photographic evidence from the northeast Atlantic suggests that another regular echinoid, Cidaris cidaris (Linnaeus, 1758), preys on feather stars. Thus in spite of the broad suite of antipredatory adaptations, feather stars are today subject to predation by regular echinoids and may have been since the Mesozoic, when this group of crinoids first appeared.在现生海百合（crinoids）类群中，羽星（feather stars）是多样性最高且栖息水深范围最广的类群，在礁体生境中尤为常见。羽星具备多种形态学、行为学及生理学特征，这些特征被假说为其演化成功的关键，尤其是在应对捕食胁迫的能力上。然而，学界对其捕食者的了解却极为匮乏，现有证据多为鱼类袭击羽星的间接佐证。本研究针对规则海胆（regular echinoids）是否也会捕食羽星这一问题展开探讨——此前已有研究表明规则海胆会捕食有柄海百合（stalked crinoids）。水族箱观测结果显示，规则海胆会取食羽星，包括那些被鱼类视作难吃的羽星种类；同时规则海胆能够捕获并取食活体羽星，包括具备游泳能力的羽星类群。对海胆（echinoid）类物种Araeosoma fenestratum（Thomson, 1872）的肠道内容物分析显示，在其13个个体的肠道中，有6个个体检出了羽星组织残留。该物种常与大量羽星Koehlermetra porrecta（Carpenter, 1888）一同出现在法国近岸海底峡谷的视频样带观测记录中。肠道内海百合组织占比极高（最高可达90%），且检出了关节连接的海百合骨骼结构，这表明该种海胆至少会取食部分活体海百合——尽管它们也可能摄食了沉积物中的海百合尸骸。此外，东北大西洋的影像证据表明，另一种规则海胆Cidaris cidaris（Linnaeus, 1758）也会捕食羽星。因此，尽管羽星演化出了多样的反捕食适应性特征，但其现今仍会遭受规则海胆的捕食；且自中生代羽星类群首次出现以来，这种捕食关系可能就已存在。