Cobia Rachycentron canadum L. 1766 are a circumglobal, pelagic species inhabiting most subtropical and tropical nearshore environments (Briggs 1960; Shaffer and Nakamura 1989). They are often found in large groups around flotsam or other large fishes (Joseph et al. 1964; Shaffer and Nakamura 1989; Felix and Hackradt 2008). Known to migrate great distances in the Western Atlantic (Shaffer and Nakamura 1989), R. canadum often experience seasonal and locational variation in available prey resources (Smith 1995). Dietary analyses suggest that adult R. canadum are opportunistic feeders but that the bulk of their diet is dominated by demersal fishes and crabs (Smith 1995; Meyer and Franks 1996; Arendt et al. 2001). Analyses of R. canadum prey-resource utilization suggest they undergo an ontogenetic shift in diet. Juvenile diets are dominated by small, nektonic fishes (e.g., Anchoa), shrimps, (e.g., Trachypenaeus and Sicyonia), and cephalopods (e.g., Loligo) with relatively few demersal species occurring in the guts (Franks et al. 1996). Conversely, adults appear to focus more on bottom-dwelling prey, including: benthic crabs, eels, tonguefish, hogchoker, hardhead catfish, pipefishes, searobins, flounders, drums, croakers, and rays. Species of rays identified from R. canadum stomachs include Rhinoptera bonasus Mitchill 1815, Hypanus sp. (formerly Dasyatis), and Narcine brasiliensis Olfers 1831 (Knapp 1951; Smith 1995; Meyer and Franks 1996; Arendt et al. 2001). In December 2018, a professional angler caught an R. canadum specimen in 12 m of water, 25 km NNE of St. Lucie Inlet, FL, and 3 km offshore from Ft. Pierce, FL. The angler was chumming with numerous types of prey and the R. canadum came to the chum slick, while following bull sharks, Carcharhinus leucas Valenciennes 1839. The fish was immediately placed on ice and the head was later removed and frozen for subsequent processing. The specimen was received in early January 2019 and was dissected in preparation for processing by carrion beetles, Dermestes maculatus de Geer 1774. Upon dissection, two stingray spines were discovered embedded in the rostrum, one on each side of the ascending process of the premaxilla (Fig. 1a–c). The spine on the fish’s right (Fig. 1d) was embedded at a relatively shallow angle and resided parallel to the ascending process of the premaxilla. The spine on the fish’s left (Fig. 1e) was delivered at a sharper angle and penetrated deep into soft tissue between the maxillary head, the palatine, and the dermethmoid. Subsequent processing of the skull revealed two additional stingray spine fragments (Fig. 1f, g), both embedded in the skin of the roof of the mouth. Given the morphological characteristics of the first spine (Fig. 1d), it is likely from an eagle ray, Myliobatis sp. If this idenfication is correct, this would be the first record of a Myliobatis in the stomach contents of R. canadum. There are two species of Myliobatis present along the Atlantic coast, Myliobatis freminvillii Lesueur 1824 in depths to 10 m (Bigelow and Schroeder 1953) and Myliobatis goodei Garman 1885 in depths to 200 m (Molina and Cazorla 2015). This spine could also be from R. bonasus as R. canadum are known to feed upon them in more northerly locations (e.g., Chesapeake Bay; see Arendt et al. 2001) and their spine resembles that of Myliobatis. The large gaps between the lateral barbs along the spine and its smooth, featureless shaft are likely the result of having been embedded in the R. canadum for a lengthy period of time. The fish’s immune system appears to have begun digesting the spine which has degraded the surface grooves used to conduct venom and eroded the barbs along its edges creating the wide gaps observed. The other spines appear to be from either Hypanus (formerly Dasyatis) species [e.g. Hypanus sabinus (Lesueur 1824) or Hypanus say (Lesueur 1817)], or Urobatis jamaicensis Cuvier 1816, as spines from these species appear very similar (Huskey, pers. obs.) and are within the range of sizes observed here. It seems these spines were only recently embedded in * Steve Huskey steve.huskey@wku.edu

中文翻译：

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嵌入军曹鱼头骨的黄貂鱼刺

Cobia Rachycentron canadum L. 1766 是一种环绕全球的远洋物种，栖息在大多数亚热带和热带近岸环境中（Briggs 1960；Shaffer 和 Nakamura 1989）。它们经常在漂浮物或其他大型鱼类周围成群结队地被发现（Joseph 等人，1964 年；Shaffer 和 Nakamura 1989 年；Felix 和 Hackradt 2008 年）。R. canadum 以在西大西洋长距离迁徙而著称（Shaffer 和 Nakamura 1989），常经历可用猎物资源的季节性和位置变化（Smith 1995）。膳食分析表明，成年 R. canadum 是机会性饲养者，但它们的大部分饮食以底栖鱼类和螃蟹为主（Smith 1995；Meyer 和 Franks 1996；Arendt 等，2001）。对 R. canadum 猎物资源利用的分析表明它们在饮食上经历了个体遗传的转变。青少年的饮食以小、游动鱼类（例如 Anchoa）、虾（例如 Trachypenaeus 和 Sicyonia）和头足类动物（例如 Loligo），其肠道中的底层物种相对较少（Franks 等人，1996 年）。相反，成年人似乎更关注底栖猎物，包括：底栖蟹、鳗鱼、舌鱼、猪颈鱼、硬头鲶鱼、尖嘴鱼、海知鱼、比目鱼、鼓鱼、黄花鱼和鳐鱼。从 R. canadum 胃中鉴定出的射线种类包括 Rhinoptera bonasus Mitchill 1815、Hypanus sp.。（原 Dasyatis）和 Narcine brasiliensis Olfers 1831（Knapp 1951；Smith 1995；Meyer 和 Franks 1996；Arendt 等人 2001）。2018 年 12 月，一名专业垂钓者在 12 m 深的水中、佛罗里达州圣露西湾 NNE 25 公里处以及距 Ft. 3 公里处捕获了一个 R. canadum 标本。皮尔斯，佛罗里达州。垂钓者正在与多种类型的猎物和 R. 1839 年，canadum 跟随公牛鲨 Carcharhinus leucas Valenciennes 来到了密友浮油上。这条鱼立即被置于冰上，随后将鱼头取出并冷冻以进行后续加工。该标本于 2019 年 1 月上旬收到，并被解剖以准备由腐肉甲虫 Dermestes maculatus de Geer 1774 进行处理。解剖后，发现两根黄貂鱼刺嵌在喙部，前上颌骨升突的两侧各有一根（图 1a-c)。鱼右侧的脊椎（图 1d）以相对较浅的角度嵌入，平行于前上颌骨的上升过程。鱼左侧的脊椎（图 1e）以更锐利的角度刺入上颌头部、腭骨和皮甲样之间的软组织。随后对头骨的处理揭示了两个额外的黄貂鱼脊椎碎片（图 1f，g），它们都嵌入在口腔顶部的皮肤中。鉴于第一刺的形态特征（图 1d），它很可能来自鹰鳐，Myliobatis sp。如果这个鉴定是正确的，这将是第一次在 R. canadum 的胃内容物中发现 Myliobatis。大西洋沿岸有两种 Myliobatis，Myliobatis freminvillii Lesueur 1824 深度达 10 m（Bigelow 和 Schroeder 1953）和 Myliobatis goodei Garman 1885 深度达 200 m（Molina 和 Cazorla 2015）。这种脊椎也可能来自 R. bonasus，因为已知加拿大 R. canadum 在更北的地方以它们为食（例如，切萨皮克湾；参见 Arendt 等人 2001），并且它们的脊椎类似于 Myliobatis 的脊椎。沿着脊椎的侧倒刺与其光滑、无特征的轴之间的大间隙可能是长时间嵌入 R. canadum 的结果。这条鱼的免疫系统似乎已经开始消化脊椎，脊椎已经降解了用于传导毒液的表面凹槽，并侵蚀了沿其边缘的倒刺，从而形成了观察到的大间隙。其他刺似乎来自 Hypanus（以前的 Dasyatis）物种 [例如 Hypanus sabinus (Lesueur 1824) 或 Hypanus say (Lesueur 1817)] 或 Urobatis jamaicensis Cuvier 1816，因为这些物种的刺看起来非常相似（Huskey，pers. obs.) 并且在此处观察到的尺寸范围内。似乎这些刺是最近才嵌入 * Steve Huskey steve.huskey@wku.edu 无特征的轴可能是长时间嵌入 R. canadum 的结果。这条鱼的免疫系统似乎已经开始消化脊椎，脊椎已经降解了用于传导毒液的表面凹槽，并侵蚀了沿其边缘的倒刺，从而形成了观察到的大间隙。其他刺似乎来自 Hypanus（以前的 Dasyatis）物种 [例如 Hypanus sabinus (Lesueur 1824) 或 Hypanus say (Lesueur 1817)] 或 Urobatis jamaicensis Cuvier 1816，因为来自这些物种的刺看起来非常相似（Huskey, pers. obs.) 并且在此处观察到的尺寸范围内。似乎这些刺是最近才嵌入 * Steve Huskey steve.huskey@wku.edu 无特征的轴可能是长时间嵌入 R. canadum 的结果。这条鱼的免疫系统似乎已经开始消化脊椎，脊椎已经降解了用于传导毒液的表面凹槽，并侵蚀了沿其边缘的倒刺，从而形成了观察到的大间隙。其他刺似乎来自 Hypanus（以前的 Dasyatis）物种 [例如 Hypanus sabinus (Lesueur 1824) 或 Hypanus say (Lesueur 1817)] 或 Urobatis jamaicensis Cuvier 1816，因为这些物种的刺看起来非常相似（Huskey，pers. obs.) 并且在此处观察到的尺寸范围内。似乎这些刺是最近才嵌入 * Steve Huskey steve.huskey@wku.edu 这条鱼的免疫系统似乎已经开始消化脊椎，脊椎已经降解了用于传导毒液的表面凹槽，并侵蚀了沿其边缘的倒刺，从而形成了观察到的大间隙。其他刺似乎来自 Hypanus（以前的 Dasyatis）物种 [例如 Hypanus sabinus (Lesueur 1824) 或 Hypanus say (Lesueur 1817)] 或 Urobatis jamaicensis Cuvier 1816，因为这些物种的刺看起来非常相似（Huskey，pers. obs.) 并且在此处观察到的尺寸范围内。似乎这些刺是最近才嵌入 * Steve Huskey steve.huskey@wku.edu 这条鱼的免疫系统似乎已经开始消化脊椎，脊椎已经降解了用于传导毒液的表面凹槽，并侵蚀了沿其边缘的倒刺，从而形成了观察到的大间隙。其他刺似乎来自 Hypanus（以前的 Dasyatis）物种 [例如 Hypanus sabinus (Lesueur 1824) 或 Hypanus say (Lesueur 1817)] 或 Urobatis jamaicensis Cuvier 1816，因为这些物种的刺看起来非常相似（Huskey，pers. obs.) 并且在此处观察到的尺寸范围内。似乎这些刺是最近才嵌入 * Steve Huskey steve.huskey@wku.edu 或 Urobatis jamaicensis Cuvier 1816，因为这些物种的刺看起来非常相似（Huskey, pers. obs.）并且在此处观察到的尺寸范围内。似乎这些刺是最近才嵌入 * Steve Huskey steve.huskey@wku.edu 或 Urobatis jamaicensis Cuvier 1816，因为来自这些物种的刺看起来非常相似 (Huskey, pers. obs.) 并且在此处观察到的尺寸范围内。似乎这些刺是最近才嵌入 * Steve Huskey steve.huskey@wku.edu