Aquatic Parasitology Laboratory and Southeastern Cooperative Fish Parasite and Disease Laboratory, School of Fisheries, Aquaculture, & Aquatic Sciences, College of Agriculture, Auburn University, 559 Devall Drive, Auburn, Alabama 36832.
Arkansas Game and Fish Commission, 2 Natural Resources Drive, Little Rock, Arkansas 72205.
J Parasitol. 2023 May 1;109(3):233-243. doi: 10.1645/23-11.
The parasites infecting invasive carps in North America (all Cypriniformes: Xenocyprididae: grass carp, Ctenopharyngodon idella [Valenciennes, 1844]; silver carp, Hypophthalmichthys molitrix [Valenciennes, 1844]; bighead carp, Hypophthalmichthys nobilis [Richardson, 1845]; and black carp, Mylopharyngodon piceus [Richardson, 1846]) are little studied, and no parasite has been reported from silver carp there. We herein surveyed silver carp from Barkley Reservoir and Cheatham Reservoir (Cumberland River, Tennessee; June and December 2021) and the White River (Arkansas; May 2022) and collected numerous monogenoid specimens infecting the pores on the outer face of the gill raker plate. We heat-killed, formalin-fixed, and routinely stained some specimens for morphology and preserved others in 95% ethanol for DNA extraction and sequencing of the large subunit ribosomal DNA (28S). We identified our specimens as Dactylogyrus cf. skrjabini because they had a dorsal anchor deep root that is much longer than the superficial root, an approximately parallel penis and accessory piece, and a relatively large marginal hook pair V. No type specimen of Dactylogyrus skrjabiniAkhmerov, 1954 (type host and locality is silver carp, Amur River, Russia) is publicly available, but we borrowed several vouchers (NSMT-Pl 6393) that infected the gill rakers of silver carp captured in the Watarase River, Japan. The original description of D. skrjabini was highly stylized and diagrammatical, differing from the specimens we studied from North America and Japan by the dorsal anchor having a superficial root and shaft that comprise a strongly C-shaped hook (the superficial root curves toward the dorsal anchor point) (vs. superficial root straight, at ∼45° angle to deep root and directed away from the dorsal anchor point), a single, much reduced transverse bar that is narrow for its entire breadth (vs. dorsal and ventral transverse bars robust and broad, having an irregular outline), an accessory piece that lacks digitiform projections (vs. accessory piece with 4 digitiform projections), and an accessory piece that lacks a half cardioid-shaped process (vs. accessory piece having a half cardioid-shaped process). Our 28S sequences (generated from 4 specimens of D. cf. skrjabini: 2 from Tennessee [763 base pairs (bp)] and 2 from Arkansas [776 bp]) were identical to 1 ascribed to D. skrjabini from Japan. The present study is the first verifiable and credible report of a parasite from silver carp in North America and the first nucleotide information for a parasite from silver carp in North America.
北美的入侵鲤鱼（所有鲤形目：鱊科：草鱼，Ctenopharyngodon idella [Valenciennes, 1844]；鲢鱼，Hypophthalmichthys molitrix [Valenciennes, 1844]；鳙鱼，Hypophthalmichthys nobilis [Richardson, 1845]；和青鱼，Mylopharyngodon piceus [Richardson, 1846]）中的寄生虫研究较少，尚未有寄生虫从那里的鲢鱼报告。我们在此调查了 Barkley 水库和 Cheatham 水库（田纳西州坎伯兰河；2021 年 6 月和 12 月）以及 White 河（阿肯色州；2022 年 5 月）的鲢鱼，并收集了大量感染鳃耙板外表面孔的单殖吸虫标本。我们对一些标本进行了热致死、福马林固定和常规染色，以进行形态学研究，并将其他标本保存在 95%乙醇中，用于提取和测序核糖体 DNA 28S 大片段。我们将我们的标本鉴定为 Dactylogyrus cf. skrjabini，因为它们的背锚有一个深根，比浅根长得多，一个大约平行的阴茎和附属物，以及一对相对较大的边缘钩 V。Dactylogyrus skrjabiniAkhmerov, 1954 的模式标本（模式宿主和产地是俄罗斯的银鲤鱼）没有公开，但是我们借用了一些银鲤鱼的标本（NSMT-Pl 6393），这些标本感染了日本 Watase 河的银鲤鱼的鳃耙。D. skrjabini 的原始描述非常风格化和图表化，与我们从北美和日本研究的标本不同，背锚有一个浅根和轴，构成一个强烈的 C 形钩（浅根向背锚点弯曲）（与浅根直，与深根成 45°角，指向远离背锚点），一个单一的，非常小的横向条，整个宽度都很窄（与背侧和腹侧横向条粗壮且宽阔，具有不规则的轮廓），一个没有指状突起的附属物（与有 4 个指状突起的附属物），一个没有半心形过程的附属物（与有半心形过程的附属物）。我们的 28S 序列（从 4 个 D. cf. skrjabini 标本中生成：2 个来自田纳西州[763 个碱基对（bp）]和 2 个来自阿肯色州[776 bp]）与来自日本的一个被认为是 D. skrjabini 的序列完全相同。本研究是首次可靠地报告了北美的寄生虫来自银鲤鱼，也是首次报道了北美的寄生虫来自银鲤鱼的核苷酸信息。
