Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi, MS, 39762, USA.
Department of Fisheries and Wildlife, College of Agriculture and Natural Resources, Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI, 48824, USA.
Syst Parasitol. 2021 Apr;98(2):119-130. doi: 10.1007/s11230-021-09965-5. Epub 2021 Mar 9.
Henneguya Thélohan, 1892 is the second most species rich genus of myxozoans, with reports from freshwater and marine fish worldwide. In the Great Lakes region of North America, muskellunge Esox masquinongy is an important game fish species that serves as an apex predator in the ecosystems of many inland lakes. The myxozoan fauna of esocid fish, especially muskellunge, remains largely understudied. During fish health assessments, muskellunge were examined for parasitic infections and myxozoan pseudocysts were observed on gill clip wet mounts. When ruptured under pressure, the intralamellar pseudocysts released thousands of myxospores consistent with those of the genus Henneguya. The myxospores were 67.3-96.6 (79.1 ± 5.9) µm in total length. The spore body was 18.6-22.6 (20.9 ± 1.0) µm × 5.4-6.9 (6.3 ± 0.4) µm in valvular view and 3.5-4.0 (3.8 ± 0.3) µm wide in sutural view. The two pyriform polar capsules positioned at the anterior of the spore body were 6.4-7.7 (7.0 ± 0.4) µm × 1.8-2.1 (2.0 ± 0.1) µm and each contained a tightly coiled polar filament with 9-10 turns. Two tapering caudal processes extended from the posterior of the spore body and were 47.3-75.6 (58.3 ± 5.8) µm in length. Histologically, large intralamellar polysporic plasmodia were surrounded by plump pillar cells and a distinct layer of plasma. Mild inflammation was present peripherally, with small numbers of necrotic germinative cells and intraplasmodial phagocytes internally. Ribosomal 18S rRNA gene sequence data were obtained from three gill pseudocysts. The three ~2000-bp sequences were identical, but shared no significant similarity with any publicly available sequence data. Phylogenetic analyses demonstrated sequence data from this Henneguya fell within a well-supported clade of Henneguya spp. reported from northern pike Esox lucius in Europe. Based on the distinct morphological, histological and molecular data, this species is designated as Henneguya michiganensis n. sp. from muskellunge in Michigan, USA.
1892 年，Henneguya Thélohan 是第二大种类丰富的粘孢子虫属，在世界各地的淡水和海水鱼类中均有报道。在北美洲的大湖区，北美狗鱼 Esox masquinongy 是一种重要的游钓鱼类，是许多内陆湖泊生态系统中的顶级捕食者。关于北美狗鱼的粘孢子虫动物群，尤其是北美狗鱼，仍在很大程度上尚未得到充分研究。在鱼类健康评估过程中，对北美狗鱼进行了寄生虫感染检查，并在鳃夹湿载片上观察到粘孢子虫假囊。当在压力下破裂时，层间假囊释放出数千个与 Henneguya 属一致的粘孢子。这些粘孢子的全长为 67.3-96.6（79.1±5.9）μm。孢子体在瓣状视图中的大小为 18.6-22.6（20.9±1.0）μm×5.4-6.9（6.3±0.4）μm，在缝合视图中的宽度为 3.5-4.0（3.8±0.3）μm。位于孢子体前部的两个梨形极囊的大小为 6.4-7.7（7.0±0.4）μm×1.8-2.1（2.0±0.1）μm，每个极囊内都含有一个紧密卷曲的极丝，有 9-10 圈。两个从孢子体后部延伸出来的锥形尾突的长度为 47.3-75.6（58.3±5.8）μm。组织学上，大的层间多孢子质体被丰满的柱细胞和一层明显的血浆所包围。周边有轻度炎症，内部有少量坏死的生殖细胞和质体内噬细胞。从三个鳃假囊中获得了核糖体 18S rRNA 基因序列数据。这三个~2000bp 的序列完全相同，但与任何公开可用的序列数据均无显著相似性。系统发育分析表明，该粘孢子虫的序列数据属于在欧洲的北梭鱼 Esox lucius 中报道的 Henneguya spp. 的一个支持良好的分支。基于独特的形态学、组织学和分子数据，该物种被指定为来自美国密歇根州的北美狗鱼的密歇根 Henneguya michiganensis n. sp.。
