Laboratory of Parasitology, Joint Graduate School of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan.
These authors contributed equally to this work.
Folia Parasitol (Praha). 2022 Aug 24;69:2022.017. doi: 10.14411/fp.2022.017.
Multivalvulid myxosporeans of the genera Kudoa Meglitsch, 1947 and Unicapsula Davis, 1924 (Cnidaria: Myxozoa) are often the cause of unsightly cyst formation or postmortem myoliquefaction in the trunk muscle of commercial marine fish, which reduces the market value of infected individuals. Twenty species (18 Kudoa spp. and two Unicapsula spp.) have been recorded from carangid fish, although the majority of them, excluding polyxenous species, such as K. amamiensis Egusa et Nakajima, 1980, K. iwatai Egusa et Shiomitsu, 1983, K. nova Naidenova, 1975, K. quadratum (Thélohan, 1895) and K. yasunagai (Hsieh et Chen, 1984), are limited to a single or a few fish species. We report the occurrence of macroscopic cysts of Kudoa trachuri Matsukane, Sato, Tanaka, Kamata et Sugita-Konishi, 2011 in the trunk muscle of four new host fish species, i.e., Pseudocaranx dentex (Bloch et Schneider), Decapterus akaadsi Abe, D. muroadsi (Temminck et Schlegel) and Decapterus tabl Berry, fished from the Philippine Sea (Northwest Pacific Ocean), off southwestern of Japan. Myxospore morphology and genetic characteristics of the ribosomal RNA gene (rDNA) of these isolates were consistent with previous records of K. trachuri from Trachurus japonicus (Temminck et Schlegel) from around Japan. In addition, a new species of Kudoa that forms long filamentous pseudocysts in trunk myofibres was found in four of the six D. tabl collected in this study. We describe Kudoa longichorda sp. n. for this new isolate, based on its morphology of subquadrate myxospores with four shell valves and polar capsules and with small dimensions (length 4.3-5.5 µm, width 6.0-6.8 µm, thickness 4.8-6.3 µm, polar capsule length 2.3-3.1 µm, polar capsule width 1.1-1.7 µm), as well as 18S and 28S rDNA sequences distinct from those of known species.
多瓣膜微孢子虫科的 Kudoa Meglitsch, 1947 和 Unicapsula Davis, 1924 属（刺胞动物：粘孢子动物）通常是商业海鱼躯干肌肉中形成难看的囊肿或死后液化的原因，这降低了受感染个体的市场价值。已从鲹科鱼类中记录了 20 种（18 种 Kudoa 种和 2 种 Unicapsula 种），尽管其中大多数（除了多宿主种，如 Kudoa amamiensis Egusa et Nakajima, 1980、Kudoa iwatai Egusa et Shiomitsu, 1983、Kudoa nova Naidenova, 1975、Kudoa quadratum (Thélohan, 1895) 和 Kudoa yasunagai (Hsieh et Chen, 1984)）仅限于单一或少数几种鱼类。我们报告了在来自菲律宾海（西北太平洋）、日本西南部捕捞的 4 种新宿主鱼类的躯干肌肉中发现了 Kudoa trachuri Matsukane、Sato、Tanaka、Kamata 和 Sugita-Konishi, 2011 的宏观囊肿。这些分离株的微孢子形态和核糖体 RNA 基因（rDNA）的遗传特征与之前在日本周围的 Trachurus japonicus（Temminck et Schlegel）中记录的 Kudoa trachuri 一致。此外，在本研究中采集的 6 尾 D. tabl 中，有 4 尾发现了一种在躯干肌纤维中形成长丝状假囊肿的新 Kudoa 种。我们根据其具有四个壳瓣和极囊的亚方形微孢子的形态以及较小的尺寸（长度 4.3-5.5 µm、宽度 6.0-6.8 µm、厚度 4.8-6.3 µm、极囊长度 2.3-3.1 µm、极囊宽度 1.1-1.7 µm），以及与已知种不同的 18S 和 28S rDNA 序列，为这个新分离株描述了 Kudoa longichorda sp. n.。
